Zero-Carbon Energy Kyoto 2010: Proceedings of the Second International Symposium of Global COE Program

Green Energy and Technology

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Takeshi Yao Editor

Zero-Carbon Energy Kyoto 2010 Proceedings of the Second International Symposium of Global COE Program “Energy Science in the Age of Global Warming—Toward CO2 Zero-emission Energy System”

Editor Takeshi Yao Program Leader Professor of the Graduate School of Energy Science Kyoto University Steering Committee of GCOE Unit for Energy Science Education Yoshida-honmachi, Sakyo-ku Kyoto 606-8501, Japan [email protected]

ISSN 1865-3529 e-ISSN 1865-3537 ISBN 978-4-431-53909-4 e-ISBN 978-4-431-53910-0 DOI 10.1007/978-4-431-53910-0 Springer Tokyo Berlin Heidelberg New York Library of Congress Control Number: 2011920681 © Springer 2011 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. The use of general descriptive na mes, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant ­protective laws and regulations and therefore free for general use. Cover design: WMXDesign, Heidelberg, Germany Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com)

Preface

Since 2008, four departments of Kyoto University, Japan—the Graduate School of Energy Science, the Institute of Advanced Energy, the Department of Nuclear Engineering, and the Research Reactor Institute—along with the Institute of Economic Research have been engaged in a Global Center of Excellence (COE) Program entitled “Energy Science in the Age of Global Warming—Toward a CO2 Zero-emission Energy System”. (Here, we have abbreviated all greenhouse gases including carbon dioxide to “CO2.”) This Global COE Program is being carried out under the auspices of the Ministry of Education, Culture, Sports, Science and Technology of Japan with the support of Kyoto University. The aim is to establish an international education and research platform to foster educators, researchers, and policymakers who can develop technologies and propose policies for establishing a scenario toward a CO2 zero-emission society no longer dependent on fossil fuels by the year 2100. Last year, the Global COE held its First International Symposium, Zero-Carbon Energy, Kyoto 2009, at the Kyoto University Clock Tower and published the proceedings in a book by the same title. This year, the Second International Symposium of the Global COE was held at Kyoto University’s Oubaku Plaza. The many excellent lectures and discussions by invited speakers and members of the Global COE and the interesting presentations by students of the GCOE Unit for Energy Science Education reflect the progress achieved by the program. This book is a compilation of those lectures and presentations. As part of the further agenda of the Global COE, the Scenario Planning Group is setting out a CO2 zero-emission technology roadmap and drawing up a CO2 zero-emission scenario based on analyses of social values and human behavior. The Advanced Research Cluster is promoting a socioeconomic study of energy, a study of new technologies for renewable energies, and research on advanced nuclear energy by following the roadmap established by the Scenario Planning Group. At the GCOE Unit for Energy Science Education, students are planning and conducting interdisciplinary group research of their own, combining social and human sciences with natural science and working toward CO2 zero emission. By participating in the scenario planning and through interaction with researchers from other fields, students will acquire the ability to survey the whole energy system and to apply the experience to their own research. The Global COE is striving to foster v

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young researchers who will be able to employ their skills and knowledge with a broad international perspective and expertise in their field of study in order to respond to the needs of society in terms of various energy and environmental problems. The Global COE is publicly promoting the achievements of the platform by making information available on the website of the Global COE; by publishing annual reports, quarterly newsletters, books, and self-inspection and -evaluation reports; by hosting domestic and international symposia and activity report meetings; by hosting the industry–government–academia collaborative symposia and citizen lectures; and by co-hosting related meetings both domestically and internationally. For securing energy and conservation of the environment, which are the most important issues for the sustainable development of human beings, the Global COE continues to take action for the establishment of “low-carbon energy science” as an interdisciplinary field integrating social science and human science with the natural sciences. Takeshi Yao Program Leader Global COE “Energy Science in the Age of Global Warming –– Toward a CO2 Zero-emission Energy System”

Contents

Part I  Scenario Planning and Socio-economic Energy Research (i)  Invited Paper Singapore’s Perspective on Energy and Future Cities.................................. Seeram Ramakrishna

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(ii)  Contributed Papers Long-Term Scenario Analysis of a Future Zero-Carbon Electricity Generation System in Japan Based on an Integrated Model....................... Qi Zhang, Benjamin Mclellan, Nuki Agya Utama, Tetsuo Tezuka, and Keiichi N. Ishihara Evaluation of Carbon Dioxide Absorption by Forest in Japan................... Yoshiyuki Watanabe, Satoshi Konishi, Keiichi Ishihara, and Tetsuo Tezuka 2050 ASEAN Electricity Demand: Case Study in Indonesia and Cambodia.................................................................................................. Nuki Agya Utama, Keiichi N. Ishihara, Qi Zhang, and Tetsuo Tezuka

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(iii)  Session Papers Proposal of a Method for Promotion of Pro Environmental Behavior with Loose Social Network............................................................. Saizo Aoyagi, Tomoaki Okamura, Hirotake Ishii, and Hiroshi Shimoda

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Performance Analysis Between Well-Being, Energy and Environmental Indicators Using Data Envelopment Analysis.................... Jordi Cravioto, Eiji Yamasue, Hideki Okumura, and Keiichi N. Ishihara

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Municipal Solid Waste Management with Citizen Participation: An Alternative Solution to Waste Problems in Jakarta, Indonesia........................................................................................................... Aretha Aprilia, Tetsuo Tezuka, and Gert Spaargaren The Influence of the Electrification in Erdos Grassland in Inner Mongolia, China................................................................................ Wuyunga and Tetsuo Tezuka

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Part II  Renewable Energy Research and CO2 Reduction Research (i)  Invited Papers The Potential of Biodiesel with Improved Properties to an Alternative Energy Mix......................................................................... Gerhard Knothe

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Net Energy Calculations for Production of Biodiesel and Biogas from Haematococcus pluvialis and Nannochloropsis sp. ............................. Luis F. Razon

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(ii)  Contributed Papers Characterization of Oligosaccharides with MALDI-TOF/MS Derived from Japanese Beech Cellulose as Treated by Hot-Compressed Water.............................................................................. Kazuchika Yamauchi and Shiro Saka

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Microwave/Infrared-Laser Processing of Material for Solar Energy......... 100 Taro Sonobe, Kyohei Yoshida, Kan Hachiya, Toshiteru Kii, and Hideaki Ohgaki (iii)  Session Papers Pongamia pinnata as Potential Biodiesel Feedstock...................................... 111 Fadjar Goembira and Shiro Saka Construction of a Novel Strictly NADPH-Dependent Pichia stipitis Xylose Reductase by Site-Directed Mutagenesis for Effective Bioethanol Production..................................................................................... 117 Sadat Mohammad Rezq Khattab, Seiya Watanabe, Masayuki Saimura, Magdi Mohamed Afifi, Abdel-Nasser Ahmad Zohri, Usama Mohamed Abdul-Raouf, and Tsutomu Kodaki

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Evaluation of Different Methods to Determine Monosaccharides in Biomass......................................................................................................... 123 Harifara Rabemanolontsoa, Sumiko Ayada, and Shiro Saka Pyrolysis and Secondary Reaction Mechanisms of Softwood and Hardwood Lignins at the Molecular Level............................................. 129 Mohd Asmadi, Haruo Kawamoto, and Shiro Saka Fractionation of Japanese Cedar and Its Characterization as Treated by Supercritical Water.................................................................. 136 Mahendra Varman and Shiro Saka Two-Step Hydrolysis of Japanese Cedar as Treated by Semi-Flow Hot-Compressed Water with Acetic Acid............................. 142 Natthanon Phaiboonsilpa and Shiro Saka Liquefaction Behaviors of Japanese Beech as Treated in Subcritical Phenol........................................................................................ 147 Gaurav Mishra and Shiro Saka Glycerol to Value-Added Glycerol Carbonate in the Two-Step Non-Catalytic Supercritical Dimethyl Carbonate Method.......................... 153 Zul Ilham and Shiro Saka Prospect of Nipa Sap for Bioethanol Production.......................................... 159 Pramila Tamunaidu, Takahito Kakihira, Hitoshi Miyasaka, and Shiro Saka Dissolution of Cerium Oxide in Sulfuric Acid............................................... 165 Namil Um, Masao Miyake, and Tetsuji Hirato Utilization of Magnetic Field for Photocatalytic Decomposition of Organic Dye with ZnO Powders................................................................ 171 Supawan Joonwichien, Eiji Yamasue, Hideyuki Okumura, and Keiichi N. Ishihara Hybrid Offshore Wind and Tidal Turbine Power System to Compensate for Fluctuation (HOTCF)...................................................... 177 Mohammad Lutfur Rahman, Shunsuke Oka, and Yasuyuki Shirai Beam Stabilization by Using BPM in KU-FEL............................................. 187 Yong-Woon Choi, Heishun Zen, Keiichi Ishida, Naoki Kimura, Satoshi Ueda, Kyohei Yoshida, Masato Takasaki, Ryota Kinjo, Mahmoud Bakr, Taro Sonobe, Kai Masuda, Toshiteru Kii, and Hideaki Ohgaki

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Analysis of Transient Response of RF Gun Cavity Due to Back-Bombardment Effect in KU-FEL..................................................... 193 Mahmoud Bakr, Heishun Zen, Kyohei Yoshida, Satoshi Ueda, Masato Takasaki, Keiichi Ishida, Naoki Kimura, Ryota Kinjo, Yong-Woon Choi, Taro Sonobe, Toshiteru Kii, Kai Masuda, and Hideaki Ohgaki Part III  Advanced Nuclear Energy Research (i)  Contributed Papers Nuclear Characteristics Transition Depend on the Position of External Source on the Accelerator-Driven System Using KUCA and FFAG Accelerator........................................................................ 205 Jae-Yong Lim, Cheolho Pyeon, Tsuyoshi Misawa, and Ken Nakajima High Performance Computing of MHD Turbulent Flows with High-Pr Heat Transfer............................................................................ 214 Yoshinobu Yamamoto and Tomoaki Kunugi (ii)  Session Papers Comparison Between Microbubble Drag Reduction and Viscoelastic Drag Reduction........................................................................... 225 Li-Fang Jiao, Tomoaki Kunugi, and Feng-Chen Li Numerical Study on Bubble Growth Process in Subcooled Pool Boiling....................................................................................................... 233 Yasuo Ose and Tomoaki Kunugi Towards Gyrokinetic Simulations of Multi-Scale Micro-Turbulence in Tokamaks: Simulation Code Development............... 239 Paul P. Hilscher, Kenji Imadera, Jiquan Li, and Yasuaki Kishimoto Study of a Particle Confinement in Helical Type Reactor by GNET Code................................................................................................. 245 Yoshitada Masaoka and Sadayoshi Murakami Study of the Mechanisms Leading to the Nonlinear Explosive Growth of Double Tearing Instabilities in Fusion Plasmas.......................... 252 Miho Janvier, Yasuaki Kishimoto, and Jiquan Li Remote Collaboration System Based on the Monitoring of Large Scale Simulation “SIMON”: A New Approach Enhancing Collaboration................................................................................ 258 Akihiro Sugahara and Yasuaki Kishimoto

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Target Design of High Heat and Particle Load Test Equipment for Development of Divertor Component...................................................... 264 Do-Hyoung Kim, Kazuyuki Noborio, Yasushi Yamamoto, and Satoshi Konishi Experimental Investigation on Contact Angles of Molten Lead–Lithium on Silicon Carbide Surface.................................................... 271 Yoshitaka Ueki, Tomoaki Kunugi, Keiichi Nagai, Masaru Hirabayashi, Kuniaki Ara, Yukihiro Yonemoto, and Tatsuya Hinoki Comparison of Operation Characteristic in Radiation Detectors Made of InSb Crystals Grown by Various Methods..................................... 278 Yuki Sato, Tomoyuki Harai, and Ikuo Kanno Specimen Size Effects on Fracture Toughness of F82H Steel for Fusion Blanket Structural Material......................................................... 286 Byung Jun Kim, Ryuta Kasada, Akihiko Kimura, and Hiroyasu Tanigawa Tensile Behavior of Transient Liquid Phase Bonded ODS Ferritic Steel Joint............................................................................................ 292 Sanghoon Noh, Ryuta Kasada, and Akihiko Kimura Helium Ion Irradiation Effects in ODS and Non-ODS Ferritic Steels.................................................................................................... 300 Ryuta Kasada, Hiromasa Takahashi, Kentaro Yutani, Hirotatsu Kishimoto, and Akihiko Kimura Thermal Conductivity of SiCf /SiC Composites at Elevated Temperature..................................................................................................... 306 Youngju Lee, Yihyun Park, and Tatsuya Hinoki Development of the Crack Detection Technique for NITE SiC/SiC Composite Applied to Fusion Blanket............................................. 311 Kazuoki Toyoshima, Tomoaki Hino, and Tatsuya Hinoki Author Index.................................................................................................... 317 Keyword Index................................................................................................. 319

Part I Scenario Planning and Socio-economic Energy Research

Singapore’s Perspective on Energy and Future Cities Seeram Ramakrishna

Abstract  With physical constraints of land size and with no natural energy resources, Singapore has to harness the human and intellectual capital of the nation to have sustainable economic growth in an urban setting. Many cities of the future have similar constraints like Singapore. With UN estimating that about 60% of the world’s population is expected to be living in urban cities by 2030, we have to develop new energy models urgently. Singapore had taken a whole-of-government approach that engaged the global, regional and local talent, industries, academicians and the citizens to develop long term strategic plans to address the challenges of energy sustainability in a holistic manner. The strategic objective is to build a distinctive global city which is liveable and lively into the future. Singapore has no natural energy resources of coal, oil gas, hydro, geothermal and biomass power. The prevailing wind speed is not high enough to be tapped with the current technology. The tidal wave is not strong enough to be tapped. Singapore has limited options and is highly dependent on fossil-based energy source. Between fuel oil and natural gas, it has gradually move to natural gas as it emits 40% less CO2 than fuel oil. The other energy options are to increase waste to energy, consider option of biofuels, promote solar energy and studying the feasibility and option of nuclear power. Enhancing energy efficiencies in all sectors of electricity generation, industries, transportation and housing are key strategies to reduce carbon footprint of future city. Increasing electrification of urban mobility and increasing connectivity in the various transportation of walking, cycling, cars, buses and trains will make city travel more energy efficient. For the built environment, zero-energy building and green building certification will encourage the use of more climate-neutral energy sources. With the strategic location that Singapore is just 1° north of the equator, solar energy is expected to provide 10–15% of the primary energy source for Singapore. Keywords  Climate change • CO2 emissions • Energy • Future cities

S. Ramakrishna (*) Office of Deputy President (Research and Technology), National University of Singapore, 21 Lower Kent Ridge Road, Singapore 119077, Singapore e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_1, © Springer 2011

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1 Introduction Rapid economic development, urbanization and consumerism have led to soaring demand for energy. The global energy crisis is at the forefront of current events. According to the United Nations, 60% of the earth’s population (4.9 billion people) will live in cities by 2030. The number of megacities, which metropolises with a population of more than ten million, will increase from 22 today to 26 by 2015. There are more than 300 cities with over a million inhabitants. Today, about half of the world’s population lives in cities. Cities consume about 75% of the world’s energy. They emit 80% of the world’s green-house gases. The urban population is expected to increase. As such, if urbanization continues on the same scale, there will be an increasing demand by city dwellers to access to energy, water, mobility and efficient, affordable healthcare (Fig. 1). City planners and developers will need to rapidly scale up their urban infrastructure to provide for the city dwellers, who will need good access to energy, water, mobility and affordable housing. Cities, by virtue of their high human density and economic growth, are the hotspots of climate-changing practices such as high energy consumption, pollution and deforestation.

Fig.  1  Urban and rural population of the world, 1950–2050. Source: World Urbanization Prospects, The 2009 Revision

Singapore’s Perspective on Energy and Future Cities

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2 Singapore Singapore is a small city, densely populated, with few natural resources and an open economy. Global problems, from the financial crisis to the threat of climate change, cast a large shadow on our small island nation. We are a city-state of 5.08 million people1 on a small island with no natural hinterland. We import much of what we consume. All the elements of a functioning state – our homes and offices, factories and power plants, roads, reservoirs, airports – have to be located within the 700 km2. At the same time, we need to ensure that our people have a clean, green and comfortable environment to live in. Singapore’s overall goal is to grow in an efficient, clean and green way. The strategic objective is to build a distinctive global city which is liveable and lively into the future. Singapore’s economy had grown from labour intensive to knowledge and innovation intensive economy in less than 50 years. Like most countries that do not have natural energy resources, the key challenges are sustainable economic growth and safeguarding our energy security and natural environment (Fig. 2).

Fig. 2  Singapore economic development journey. Source: Singapore Department of Statistics 1  Statistics Singapore www.singstat.gov.sg Singapore’s total population was 5.08 million as at end June 2010. There are 3.77 million residents, of which 3.23 million were Singapore citizens and 0.54 million were permanent residents.

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Fig. 3  Drivers for change

With Singapore physical constraint of land size and with no natural energy resources of coal, oil, gas, hydro, wind, tidal, geothermal and biomass power and the need to mitigate climate change, Singapore is driven to find new ways for sustained economic growth while safeguarding our energy security and natural environment (Fig. 3). Under the leadership of the Prime Minister, the country took a whole-of-government approach and appointed international advisory panels of top minds, form interministerial committees, engaged the academics and industrials in local panels and using web-based platform to engage the public in consultation and feedback to tackle the challenges. The four key areas of focus include: look at all available energy options, for short term will increase fuel mix to use more natural gas, built more waste incineration plants for electricity generation, deploy more solar panel applications, work on biofuels and undertake feasibility of nuclear option. Energy Efficiencies are immediate actions can be taken for all sectors. Increase electrification of urban mobility. And use more climate-neutral energy sources for built environment. Climate change and energy issues are complex and cut across different sectors and industries, and involve policies from different ministries and agencies. The Energy Policy Group (EPG) was set up in 2006 with four working groups on Economic Competitiveness, Energy Security, Climate Change and the Environment, and Energy Industry Development, headed by the different agencies as shown in Fig. 4. The clean energy movement in Singapore gained momentum in 2007, when Prime Minister Lee Hsien Loong announced that Singapore will be developing the clean energy industry as a key growth area, generating a potential $1.7 billion in revenue and 7,000 jobs by 2015 [1]. The National Energy Policy Report developed by the Ministry of Trade and Industry (MTI) and released in November 2007 outlines six strategies for Singapore

Singapore’s Perspective on Energy and Future Cities

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Fig. 4  Energy Policy Group

to strengthen its economic competitiveness, enhance energy security and improve environmental sustainability [2]. The six key strategies are: 1 . Promote Competitive Markets 2. Diversify Energy Supplies 3. Improve Energy Efficiency 4. Build Energy Industry and Invest in Energy R&D 5. Step Up International Development 6. Develop Whole-of-Government Approach In April 2009, the Singapore Government unveiled an S$1 billion (US$730 billion) Sustainable Development Blueprint which contains strategies and initiatives developed towards achieving both economic growth and a good living environment for Singapore over the next two decades [3]. The blueprint is based on a four-pronged strategy: boosting our resource efficiency, enhancing our urban environment, building our capabilities, and fostering community action. Some of the aggressive targets set include: 1. To achieve a 35% reduction in energy intensity (consumption per dollar GDP from 2005 levels by 2030. 2. To raise overall recycling rate to 70% by 2030. 3. To improve air quality by reducing ambient PM 2.5 (fine particles) levels to an annual mean of 12 mg/m3 by 2020, and maintain the same levels up to 2030. 4. To build Singapore into an international knowledge hub in sustainable development solutions. 5. To achieve a community in Singapore where environmental responsibility is a part of our people and business culture.

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The government has taken actions to catalyze collaborative innovation. For instance, to encourage energy-efficient building technologies, the Building and Construction Authority (BCA) has set aside a $5 million fund to encourage local developers to partner experts worldwide to develop prototype building designs that can achieve at least 50% improvement in energy efficiency [4]. Besides new buildings, the Government has also established a $100 million fund to help building owners upgrade and improve the energy performance of their existing buildings. At the same time, the Housing and Development Board (HDB) has embarked on the largest solar test-bed in Singapore to understand and adapt solar technology to our local conditions. Through the Housing Development Board public housing programme implemented over the last 50 years, over 80% of Singaporeans live in 900,000 HDB flats across the island, with 95% of them owning their homes. As the largest housing developer in Singapore, HDB plays a key role in spearheading sustainable development practices. In Singapore, we have a Green Mark Scheme under the BCA. This is a green building rating system, promoting and adoption of green building design and technologies. Under this scheme, buildings are assessed on factors including energy and water efficiency, indoor environmental quality and environmental protection. We have set a target of at least 80% of buildings in Singapore should attain Green Mark certification by 2030.2 NUS has achieved the Green Mark awards for its University Town, University Town’s Education Resource Centre, the Mochtar Riady Building at the NUS Business School and the T-Lab. The Singapore Government is taking the lead in embracing the green mark standards for all public sector buildings. For its part, the HDB is aiming for the Green Mark Platinum standard, the highest green mark rating, for some important public housing projects. HDB is also developing its first Eco-Precinct, named the Treelodge@Punggol. Punggol is a coastal town located at Singapore’s northeast.3 With its eco-friendly features that capitalize on nature and the use of green technologies, the precinct will create a green living environment and raise popular awareness of environment sustainability. Punggol will serve as a ‘living laboratory’ to test new ideas and technologies in sustainable development, integrating urban solutions to create a green living environment. R&D studies will be conducted to address the diverse expectations and changing aspirations of residents. Urban solutions in the areas of energy, waste and water management will be explored. Eventually, HDB hopes to lower the implementation cost of these solutions and to replicate them across other towns.

Economic Development Board (EDB). Housing and Development Board (HDB).

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Going forward, Singapore seeks to serve as a “Living Laboratory” where new ideas and technologies in sustainable development can be tested (Fig. 5). It invites companies to partner our government agencies, local companies and research institutes for a diversity of R&D activities. Singapore will be a “Living Laboratory” to test new concepts, develop and commercialize cutting-edge urban solutions, capitalizing on Singapore’s experience in systems-level integration across six focus areas (See footnote 2) (Fig. 6). One key area is in promoting of energy efficiency. Energy efficiency reduces the carbon footprint in our city and also saves costs for businesses and consumers.

Fig. 5  Singapore as a Living Laboratory

Fig. 6  Urban solutions focus areas

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In addition, Singapore forms global partnerships with other countries to develop innovative prototypes for the sustainable cities of tomorrow. One good example is the Tianjin Eco-city in China [5]. The Governments of Singapore and China are jointly developing the 30 km2 city into an environmentally friendly, socially harmonious and resource efficient city. This project involves putting in place key infrastructure to support sustainable development, such as a light-rail transit line to link the Eco-city to Tianjin City and surrounding districts, a pneumatic waste collection system, a new wastewater treatment plant, and major rehabilitation works for existing water bodies. In July 2010, a ground-breaking ceremony was held at Jurong Island where Singapore will build the world largest Experimental Power Grid of 1 MW [6]. This S$38 million (US$27.5 million) facility will be ready by second half of 2011. This Experimental Power Grid Centre (EPGC) will perform research on “intelligent grids” and distributed energy resources. This power grid will allow power from solar, fuel cells, and electric/hybrid vehicles to feed energy back into the system. NUS performs high-quality research over a broad range of disciplinary and crossdisciplinary areas. It has a wide energy and environment cluster as shown below (Fig. 7). The Solar Energy Research Institute of Singapore (SERIS) is Singapore’s national institute for applied solar energy research, jointly set up by NUS and the Economic Development Board (EDB). It performs quality research and work closely with the industry in solar photovoltaic devices as well as innovative materials for solar and energy-efficient buildings. It has a research funding of S$130 million over 5 years. The Energy Studies Institute (ESI) is established by the Singapore Government and hosted by NUS. As Southeast Asia’s first think-tank on energy issues, ESI play an important role in the development of energy policies in the region on three key areas – Energy Economics, Energy Security, and Energy and the Environment. The NUS Global Asia Institute (GAI) is an initiative of NUS President Tan Chorh Chuan on research and scholarship directed at topics pivotal to Asia’s future. The institute will bring together existing expertise from NUS and other universities, particularly those with expertise in India and China, in its quest for solutions that will solve the critical issues within Asia [6]. In the area of nuclear energy, subject to the Singapore Government’s support, NUS is prepared to undertake the following high impact research in areas such as: 1 . Nuclear Forensics and Detection 2. Radio Chemistry and Nuclear Defense 3. Reactor Engineering 4. Nuclear Medicine 5. Material Sciences 6. Environmental Sciences 7. Life Sciences

Singapore’s Perspective on Energy and Future Cities

Fig. 7  NUS energy and environment cluster (color figure online)

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3 Conclusion Cities today face many similar challenges arising from pressures such as urbanization, climate change, and energy constraints. No one city is able to solve all the problems it faces. Only by collaborating with one another through sharing of ideas and expertise, cities of the world can learn from one another as they grow and develop sustainably.

References 1. The Straits Times, 27 March 2007 “S’pore aims to be key player in green energy push” 2. Ministry of Trade and Industry (MTI). http://www.mti.gov.sg/. Accessed 13 Sept 2010 3. Ministry of the Environment and Water Resources (MEWR). http://app.mewr.gov.sg/. Accessed 13 Sept 2010 4. Building and Construction Authority (BCA). http://www.bca.gov.sg/. Accessed 13 Sept 2010 5. Sino-Singapore Tianjin Eco-city. http://www.tianjinecocity.gov.sg/. Accessed 13 Sept 2010 6. The Straits Times, 17 July 2010 “Power grids of the future” – The world’s largest experimental energy grid, and the first in South-east Asia, is being developed on Jurong Island

Long-Term Scenario Analysis of a Future Zero-Carbon Electricity Generation System in Japan Based on an Integrated Model Qi Zhang, Benjamin Mclellan, Nuki Agya Utama, Tetsuo Tezuka, and Keiichi N. Ishihara

Abstract  The realization of a zero-carbon electricity system is of vital importance to a future zero-carbon energy system and society. Nuclear power and renewable energy are expected to contribute significantly to this in the future in Japan. Therefore, in the present study, their roles in future zero-carbon electricity system was examined using long-term scenario analysis from 2005 to 2100 based on an integrated analysis model. The analysis is conducted in three steps to (1) estimate electricity demand and load pattern based on lifestyle and industrial structure in the future using a bottom-up simulation sub-model; (2) plan the optimized power generation mix to satisfied obtained electrical demand and load subject to various constraints including natural resources, economic, environmental, geographic, natural conditions, etc. using an optimization sub-model (3) confirm the reliability of the obtained best mix power generation system by using an hour by hour simulation sub-model. The results give the schedule of nuclear and renewable energy development from 2005 to 2100 and show that they will contribute 60% and 40% respectively in terms of electricity production by 2100. Finally, the whole system is proven as technically feasible with the help of EV (Electric Vehicle) batteries and hydrogen for daily and seasonal electric storage respectively, operated based on smart control technologies. Keywords  Electricity generation system • EV • Nuclear power • PV • Zero-carbon

1 Introduction In an examination of potential zero-carbon energy futures for Japan, it was considered that the CO2 emission reductions required could be achieved mainly in three different ways: by a reduction in energy demand, an expansion in nuclear power or

Q. Zhang (*), B. Mclellan, N.A. Utama, T. Tezuka, and K.N. Ishihara Graduate School of Energy Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_2, © Springer 2011

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the increase in renewable energy production. Several studies also show that this reduction could be achieved by increasing the share of electricity utilization on the end-user side [1, 2], which is considered to be the most effective way to reduce demand through technology substitution and energy saving, and increase the penetration of nuclear power and renewable energy simultaneously. The philosophy adopted in this study agrees with these studies and considers that society is becoming more reliant on electricity, which further highlights the need to move to a zerocarbon electricity system based on zero-carbon power sources including nuclear power and renewable energy (Photovoltaic (PV), wind, biomass, etc.). Although some future zero-carbon energy system scenarios based on renewable energy (solar, wind, wave, etc.) have been proposed both for individual countries or globally [3, 4], the most common criticism is that renewable energy produces electricity too intermittently and is too costly. Thus, nuclear power is expected to contribute as a low-carbon energy source much more in the future in Japan [1, 5]. On the other hand, in the future, renewable energy is likely to become cheaper and cheaper, but nuclear power may become more and more expensive due to the price rise of nuclear fuel. Furthermore, too much nuclear power without effective nuclear waste treatment will convert the CO2 problem to a nuclear waste problem. Therefore, in the present study, long-term planning of a scenario for a zero-carbon electricity generation system with maximum renewable energy from 2005 to 2100 is conducted using a developed integrated model.

2 Scenario Analysis for Electricity Generation System and Proposal for an Integrated Model The basic idea of the present study is to conduct the scenario in three steps to (1) estimate electricity demand and load pattern based on lifestyle and industrial structure in future; (2) plan the optimized power generation mix to satisfy electrical demand and load subject to various constraints including natural resources, economic, environmental, geographic, natural conditions, etc. (3) study the reliability of the obtained best mix power generation system using an hour by hour simulation. Therefore an integrated model has been proposed including (1) a bottom-up simulation model, (2) an optimization model (3) an hour by hour simulation model. As shown in Fig. 1, three sub-models are connected with each other through data flow.

3 Estimating Future Electricity Demand The final total electrical demand and load is obtained using the bottom-up simulation model as shown in Fig. 1 based on framework comprised of residential, commercial, industrial and transportation sectors and their several sub-sectors. The simulation is

Long-Term Scenario Analysis of a Future Zero-Carbon Electricity Generation System

Efficiency Improvement

Technology Substitution

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Annual Electricity Demand

Bottom-Up Simulation Model Life Style

Estimating electricity demand

Electric Annual Load Duration Curve

Population, GDP, Macro Economy

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Physical, natural and system constrains

Long-term Electricity Mix Planning Model

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Environment and economy constrains Hourly Electric Load Data

Hourly Demand-Supply Electricity Storage (Battery, Hydrogen)

Hour by Hour Simulation Model

Reliability examination of electricity system

Optimization planning of electricity mix

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Best Mix Of Electricity System

Operation Pattern of Power Plants

Fig. 1  Proposed Integrated Scenario Analysis model for Zero-Carbon Electricity system (ZCEISAM)

Final Energy Consumption(1015J) (Left) and Electrification(%)(Right) 16000.00

electricity heat oil coal

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80.00%

biomass hydrogen gas Electrification ratio

70.00% 60.00%

12000.00

Electrification Ratio (%*

10000.00

40.00%

8000.00

Electricity

6000.00 4000.00 2000.00

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Oil Coal, Natural gas

Biomass

30.00% 20.00%

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2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 2065 2070 2075 2080 2085 2090 2095 2100

Fig. 2  Obtained final energy demand by using the bottom-up simulation model

conducted in several steps based on the base year data, assuming parameters such as efficiency, share design according to socio-economic and technology parameters such as lifestyle, macro economy, technology improvement and technology shift. The simulation results are shown in Fig. 2, in which the electricity demand is shown to increase from 1,000 TWh to 1,500 TWh from 2005 to 2100 [6].

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4 Long-Term Optimization Planning of Electricity Generation The detailed long-term optimization planning model in the proposed integrated model is shown in Fig. 3. The model aims to find the least total CO2 emission solution to meet the electrical demand obtained in the previous step, subject to various constraints including physical space, replace schedule, generation grid technology, environmental, economic, resource availability, and so on. The proposed optimization method is quite different to many models proposed in past studies such as MARKAL and AIM (Asia-Pacific Integrated Model), which aim to find the least cost solution. The philosophy is that the external costs that will arise from the negative environmental impacts of fossil fuel burning and climate change are not considered in the existing least cost analysis models, meaning that these results cannot be accepted as realistic. Therefore, if humanity is really serious about the climate change issue, the least total amount of CO2 accumulation in the atmosphere should be the goal pursued, which means a least total CO2 emissions path for a final zerocarbon energy system should be pursued. The obtained optimization results (subject to the main constraints listed in (Table  1) are shown in Fig.  4. The results indicate that to realize a zero-carbon electricity generation system by 2100, Japan will still be dependent 60% on nuclear power, with 35% on all renewable energy and 5% on energy storage.

Capacity constraints Fuel Consumption Cost Constraints

Electricity Demand Electrical Load Pattern

Initial Install Capacity New Equipment Constraints

Least Accumulated CO2 Long-term Planning Optimization Model Construction Cost OM Cost Fuel Cost

Install Capacity, Electricity production Cost, Fuel Consumption CO2 Emission Power Output Pattern Utilization Ratio

Efficiency Load Factor Constraints Electrical Storage Constraints

Fig. 3  Long-term optimization planning model for electricity generation mix

Long-Term Scenario Analysis of a Future Zero-Carbon Electricity Generation System Table 1  Main constraints for the optimization planning [7–10] Max capacity Replacement strategy Annual CF Min 60% Coal Replace 50% (of current capacity) by 2050, and no Max 85% replacement after 2050 Oil No replacement (of current Min 30% capacity) Max 60% Min 40% Gas Replace 100% (of current capacity) by 2050, and no Max 70% replacement after 2050 Hydro 30 GWe Max construction capacity: 40% 1 GW/year Nuclear 185 GWe Max construction capacity: 80–90% 3 GW/year PV 100 GWp 2030: 54 GW 12% Wind

50 GWe

Biomass 30 GWe

2050: 25 GW

20%

Max construction capacity: 1 GW/year

60–80%

21

Hourly CF Min 50% Max 90% Min 0 Max 100% Min 0 Max 100% 40%

Min 0 Max 70% Min 0 Max 100% Min 0 Max 100%

CF Capacity factor Power Generation (100 GWh)

18000.00

Battery Wind Gas

16000.00 14000.00

PV Nuclear Oil

Biomass Coal Hydro PV

Battery

12000.00

Wind

Biomass

10000.00 8000.00

Nuclear

6000.00 4000.00 2000.00 0.00

Coal Oil

Gas Hydro

2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 2065 2070 2075 2080 2085 2090 2095 2100

Year

Fig. 4  Obtained electricity generation mix for zero-carbon electricity system in Japan

5 Hour by Hour Simulation Model for Reliability Analysis For the case of zero-carbon power sources, the output electricity of nuclear power stations cannot be adjusted, due to safety and economic constraints, and the output electricity of renewable power from solar, wind and wave highly depends on weather conditions such as intensity of sunlight, strengths of wind and waves which are highly unpredictable. Therefore, the existence of adequate electricity storage facilities is a key part of zero-carbon electricity systems to level electric loads and absorb the output fluctuations of renewable power sources. Therefore, batteries in electric vehicles (EV) [11–14] and hydrogen [15–17] are selected for daily and

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seasonal electricity storage, the whole electricity system and detailed hour by hour simulation model are shown in Figs.  5 and 6 respectively, by which the hour by hour electricity supply-demand balance and electricity storage information can be obtained. The input hourly electrical load data and electricity mix were obtained in the first two steps. The hourly power generation is obtained according to nuclear operation conditions, solar irradiation and wind speed, etc. The simulation starts by reading the hourly electric loads from the data record. Then it checks if the amount of power generation at one point in time is greater than the load demand. If so, the system will use its spare capacity to either recharge the batteries (providing that they are not full) or generate hydrogen. However, if the amount of power generated is lower than the electricity demands, then the system will first attempt to use the electricity stored in batteries, and then when these are empty it will generate electricity from the stored hydrogen. The hourly electrical supply-demand balance relationship and electricity storage operation information were obtained by using the developed computer software Hydrogen-Based Electricity Storage PEM Electrolyzer

Grid Power Source

Storage

Fuel Cell

E2H H2E

Electrical Load

Smart Control G2V V2G

Electric Vehicle (EV)

Electricity/Hydrogen Information Communication

Battery-Based Electricity Storage

Fig. 5  Schematic diagram of a zero-carbon electricity system based on electric storage and smart control technologies

Hourly Available Capacities of Hydrogen Production and Electricity Supply from Fuel Cells

Hourly Electrical Load Data

Hourly Short-term, Long-term, Comprehensive Electric Storage Strategy

Hour by Hour Demand-Supply Computer Simulation

Hourly Available Charge/Discharge Capacity of Batteries in EVs

Hourly Power Generation

Hourly Moving Pattern and Charge/Discharge Pattern of EVs

Hourly Demand-Supply Hourly Electricity Storage (Battery, Hydrogen)

Operation Pattern of Power Plants, solar irradiation, wind speed

Fig.  6  Hour by hour simulation model for confirming demand-supply balance in electricity system

Long-Term Scenario Analysis of a Future Zero-Carbon Electricity Generation System

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Fig. 7  Hour by hour simulation result obtained by using a developed computer code

code as shown in Fig.  7. The results show that during the spring and autumn periods, and some week-long Japanese holidays such as the New Year Festival (beginning of Jan.), Golden Week (beginning of May) and Bon Festival (middle of August.), surplus electricity generated from nuclear power is converted to hydrogen through water electrolysis when the EV batteries are in a “full” state. On the other hand, electricity is generated from hydrogen fuel cells in winter and summer when many electrical load peaks appear due to the heating and air conditioning demands, respectively. Hence during this period the hydrogen generated during the other periods must be converted back into electricity.

6 Conclusion A zero-carbon electricity generation system is of vital importance to the achievement of a zero-carbon emissions energy system in future, with the society becoming reliant on electricity more and more. An integrated model has been proposed to conduct long-term scenario analysis for zero-carbon electricity generation system in Japan from 2005–2100. The electricity demand is expected to increase from 1,000 TWh to 1,500 TWh from 2005 to 2100, and Japan will be dependent 60% on nuclear power, with 35% for all renewable energy and 5% for energy storage. The obtained electricity generation system is proven to be technically feasible and reliable with the help of EV batteries and hydrogen for daily and seasonal electric storage respectively, operated based on smart control technologies.

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Acknowledgements  The authors wish to thank all members in the GCOE scenario planning committee, scenario-advanced technology joint meeting and scenario strategy meeting in Graduate School of Energy Science, Kyoto University for helpful comments and support.

References 1. JAEA (2009) 2100 nuclear vision (in Japanese) 2. Ministry of Economy (2005) Trade and industry, super long-term strategic technology roadmap, energy technology vision 2100. Ministry of Economy, Japan (in Japanese) 3. Lund H, Mathiesen BV (2009) Energy system analysis of 100% renewable energy systems – the case of Denmark in years 2030 and 2050. Energy 34:524–531 4. Jacobson MZ, Delucchi MA (2009) A path to sustainable energy by 2030. Sci Am 301(5):38–45 5. Uchiyama Y (2008) Global warming and future nuclear power industry. Trans At Energy Soc Jpn 50(4):2–3 (in Japanese) 6. Zhang Q, Tezuka T, Ishihara KN, Esteban M, Utama NA (2009) Study on a zero-carbon electricity system in Japan using a proposed optimization model. Proceedings of international symposium on sustainable energy and environmental protection (ISSEEP), Yogyakarta, Indonesia, 23–26 November 2009 7. World Nuclear Association (2009) Nuclear power in France. http://www.world-nuclear.org/ info/inf40.html. Updated Oct 2009, Accessed Dec 2009 8. Tokyo Electric Power Company (2009) Nuclear power monthly capacity factor data. http:// www.tepco.co.jp/nu/index-j.html. Accessed Dec 2009 [16] 9. The Homepage of Kansai Electric Power Cooperation (2009) http://www.kepco.co.jp/ localinfo/live/n_unten/teikaku/teikaku.htm. Accessed Dec 2009 10. Zhang Q (2010) Study on the potential of nuclear power and renewable energy in Japan. GCOE scenario strategy meeting, May 2010 (in Japanese) 11. Yoda S, Ishihara K (1997) Global energy prospects in the 21st century: a battery-based society. J Power Sources 68(1):3–7 12. Kariatsumari H, Shimizu N, and Nozawa A(2009) Smart grid ON! – Next generation electricity gird based on battery and sensor, Nikkei Electronics, 2009.10.19:30–52 (in Japanese) 13. Guille C, Gross G (2009) A conceptual framework for the vehicle-to-grid (V2G) implementation. Energy Policy 37(11):4379–4390 14. Kempton W, Kubo T (2000) Electric-drive vehicles for peak power in Japan. Energy Policy 28(1):9–18 15. Hall PJ, Bain EJ (2008) Energy-storage technologies and electricity generation. Energy policy 36(12):4352–4355 16. Gutierrez-Martın F, Garcıa-De Marı JM, Baıri A, Laraqi N (2009) Management strategies for surplus electricity loads using electrolytic hydrogen. Int J Hydrogen Energy 34:8468–8475 17. Honma T, Ed. (2006) Handbook of hydrogen and fuel cell, Ohmsha (in Japanese)

Evaluation of Carbon Dioxide Absorption by Forest in Japan Yoshiyuki Watanabe, Satoshi Konishi, Keiichi Ishihara, and Tetsuo Tezuka

Abstract  In order to investigate regional absorption of carbon dioxide (CO2) by forests in Japan, first, focusing on an experimentally obtained relation between photosynthetic rate of a tree and atmospheric CO2 concentration around the tree, the atmospheric CO2 concentration dependence of CO2 absorption rate of forests has been described by a Michaelis–Menten type function. Secondly, from the viewpoint of local region for operating area of electric power companies, CO2 absorption by forests has been investigated for different three cases with a simple model in which the atmospheric CO2 concentration around artificial forests are artificially increased up to 1,000  ppm. The resultant CO2 absorption by forests much depends on the atmospheric CO2 concentration, and will be effectively promoted by an easy artificial treatment. Those results might be useful to design a biomass energy carbon capture storage system toward a sustainable society. Keywords  Absorption • Atmospheric CO2 concentration • Carbon dioxide (CO2) • Forest • Photosynthesis

1 Introduction In recent years, emission of greenhouse gasses typified by carbon dioxide (CO2) drastically has increased with drastic increasing energy demand on global scale; consequently, global warming and various environmental issues grow into serious problems. In Japan, total artificial CO2 emissions as of FY 2008 is about

Y. Watanabe (*), K. Ishihara, and T. Tezuka Graduate School of Energy Science, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan e-mail: [email protected] S. Konishi Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan

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1,214 ­million tonnes [1], where the CO2 emissions mostly are classified into the ­following three main sectors: (a) Energy industries sector typified by heat power generation, (b) Manufacturing industries and Construction sector typified by ion-, steel- and cement-making, and (c) Transport sector typified by automobiles. On the other hand, removals (absorption) of CO2 at continental areas in Japan is mostly classified into the land use, land-use change and forestry (LULUCF) sector, and the value as of FY 2008 is about 79 million tonnes [1], and in which CO2 absorption by forest land is about 80 million tonnes that corresponds to about 7% of the total artificial CO2 emissions (1,214 million tonnes). This means that forest is an important natural sink to remove and storage CO2. In the present study, the emission and absorption of CO2 in Japan are discussed focusing on the heat power generation and forest land. For the heat power generation in Japan, there are ten big electric power companies (Hokkaido-, Tohoku-, Tokyo-, Chubu-, Hokuriku-, Kansai-, Chugoku-, Shikoku-, Kyushu-, and Okinawa-electric power Co., Inc.). Figure  1a shows the electric production by the ten companies in FY 2005–2009 (avg.) [2]. The operating region of each company is also shown in the figure. The electric production by Tokyo and Chubu are much higher than those by the other companies because of large amount of population and industrial establishments. The total electric production by the all companies is about 490 billion kW h with CO2 emissions of about 340 million tonnes which is estimated by the CO2 emission factor 0.69 kg-CO2/kW h for heat power generations. As to forest land in Japan, total forest land area as of FY 2008 is about 25.0 million ha which covers about 70% of Japan’s total land area (37.8 million ha). About 60% and 40% of the total forest land area mainly are covered by natural forests (native forest) and artificial forests (intensively managed forests), respectively. The natural forests consist of broadleaf trees such as cherry, maple and oak, while the artificial forests consist of needle leaf trees such as Larix kaempferi, cedar and cypress. Figure 1b shows the forest land area as of FY 2007 [3] in the operating region of each electric power company. Notice that each number in the figure corresponds that in Fig. 1a. The north land (Hokkaido and Tohoku) has relatively much forest. In addition, both natural forests and artificial forests exist in a relatively large amount at any operating regions except Okinawa. Here, consider the photosynthesis in plants. The photosynthesis is a chemical reaction inside a plant, and is between H2O and CO2 absorbed by the plant, leading to production of dioxide (O2) and storage of carbon. Figure 2 represents an experimentally obtained relation between photosynthetic rate and CO2 concentration in the atmosphere for Larix kaempferi seedlings [4]. The photosynthetic rate much depends on the atmospheric CO2 concentration. This indicates that when the atmospheric CO2 concentration around forests can be increased by artificial or some means, the forests will absorb much more CO2. From those arguments described above, in the present study, focusing on the relation between photosynthetic rate of forests and the atmospheric CO2 concentration, CO2 absorption by forests at the operating region of each electric power company was numerically investigated, in which the atmospheric CO2 concentration around forests was increased by an artificial means as described in the next section.

Evaluation of Carbon Dioxide Absorption by Forest in Japan

27

200

Tohoku

138

Hokkaido

Hokuriku

150

104

Chugoku

Chubu Shikoku

100

Tokyo

Kansai

Kyushu Okinawa

69

50

35

0

0

Emission of CO2 (million tonnes)

Electric production (billion kWh)

a

Electric power company

Forest land area (million ha)

b

6

Natural forests

40% Artificial forests Natural forests

60%

4

Artificial forests 2

0

Operating region of each electric power company Fig. 1  (a) Electric production by the ten big electric power companies in FY 2005–2009 (avg.) and (b) forest land area in the operating region of each electric power company in FY 2007

2 Procedure The present study was conducted through the following two steps: (a) Focusing on the relation between photosynthetic rate of a tree and atmospheric CO2 concentration, the atmospheric CO2 concentration dependence of CO2 absorption by forests was described using a numerical formula, in which that the Larix kaempferi as one of needle leaf trees was chosen; (b) From the view point of the operating region of each electric power company, CO2 absorption by forests was investigated using a

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Exp.

Photosynthetic rate, v (µmolm−2 s−1)

Larix kaempferi 6

4

2

0

−2

0

200

400

600

800

1000

Concentration of CO2 in the atmosphere, x (ppm) Fig. 2  Experimentally obtained relation between photosynthetic rate and CO2 concentration in the atmosphere for Larix kaempferi seedlings

CO2

Power plant

Pipeline

Forests

Fig. 3  Simplified schematic of transportation of CO2 emitted form a heat power plant into forests by pipeline

simple model in which the atmospheric CO2 concentration around artificial forests was artificially increased as represented in Fig. 3. As shown in the figure, CO2 emitted from a heat power plant is directly transported and spread into forests using pipeline, where the concentration of atmospheric CO2 spread inside forests is maintained with 1,000 ppm which is much higher than the average (equilibrium) atmospheric CO2 concentration of around 385 ppm. Notice that this artificial treatment is done for only artificial forest. Namely, the atmospheric CO2 concentration around artificial forests is set to 1,000 ppm, while that around natural forests is set to the average value (385  ppm). By the way, the atmospheric CO2 concentration inside forests cannot be increased over 1,000  ppm because the limit for animals not to die (get pale) is around 1,000 ppm.

Evaluation of Carbon Dioxide Absorption by Forest in Japan

29

3 Results and Discussion First, by fitting of the tendency for Larix kaempferi in Fig. 2 to a Michaelis–Menten type function, the relation between photosynthetic rate of a tree and atmospheric CO2 concentration around the tree was described by n(x) = 11.49x/(624.48+x)−1.02, where x is the atmospheric CO2 concentration. The photosynthetic rate increases with increasing the atmospheric CO2 concentration, and becomes progressively saturated over 1,000  ppm. When the atmospheric CO2 concentration is around 1,000 ppm, the photosynthetic rate increases more than twice of that at around the average CO2 concentration (385 ppm). And then, the description of relation between CO2 absorption rate of forests and atmospheric CO2 concentration around forests was attempt using the following two assumptions: (a) The tendency of relation between CO2 absorption rate of forests and atmospheric CO2 concentration is similar to that between the photosynthetic rate of a tree and atmospheric CO2 concentration; (b) Most of current forest land in Japan is soaked at around 385 ppm of the average CO2 concentration, and the total CO2 absorption by forests is approximated by the 80 million tonnes mentioned in the previous section. The resultant equation with the two assumptions is given by K(x) = an(x) in the unit (ton-CO2/ha), where a is the constant number of 0.99. The CO2 absorption rate of forests is an increasing function of atmospheric CO2 concentration, and the absorption rate at around 1,000 ppm is more than twice of that at around 385 ppm. Through the use of K(x), CO2 absorption by forests at a variety of atmospheric CO2 concentration can be estimated. Next, from the view point of the operating region of each electric power company, CO2 absorption by forests was investigated for the following three cases: (a) Current forest land, (b) Forest land with twice artificial forest land area, and (c) Forest land with new species of artificial forests. Figure 4 shows the annual CO2 emission and absorption by heat power plants and forests for the three cases: (a), (b) and (c). In the case of (a), the CO2 absorption by forests is 111 million tonnes. This value is increase of 39% over the current one (80 million tonnes), and is correspond to 33% of CO2 emission amount (340 million tonnes) from the heat power plants. For the case of (b), the CO2 absorption by forests is 137 million tonnes which is increase of 70% over the current one, and is correspond to 40% of CO2 emission amount from the heat power plants. As to the case of (c), the CO2 absorption rate of the new species is assumed to be twice of that of the current one, and the CO2 absorption by forests is 218 million tonnes which is increase of 170% over the current one, and is correspond to 64% of CO2 emission amount from the heat power plants.

4 Summary In order to investigate regional absorption of CO2 by forests in Japan, first, focusing on the relation between photosynthetic rate of a tree and atmospheric CO2 concentration around the tree, the atmospheric CO2 concentration dependence of CO2

Y. Watanabe et al. CO2 emission and absorption (million tonnes)

30 150

Heat power plants

a 100

1000 ppm 40% Artificial 60% forests Natural forests 385 ppm

CO2 emission: 340 million tonnes

50

0

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CO2 absorption: 111 million tonnes

CO2 emission and absorption (million tonnes)

Operating region of each electric power company

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1000 ppm 80% Artificial 20% forests

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CO2 emission: 340 million tonnes

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c 100

1000 ppm 80% Artificial forests 20% (New species) Natural forests 385 ppm

50

CO2 emission : 340 million tonnes

0 CO2 absorption:

−50

Forests 218 million tonnes

Operating region of each electric power company

Fig. 4  Annual CO2 emission and absorption by heat power plants and forests for the three cases (a), (b) and (c)

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31

absorption rate of forests was described using a Michaelis–Menten type function. The CO2 absorption rate is an increasing function of atmospheric CO2 concentration, and becomes progressively saturated over 1,000 ppm. In addition, the absorption rate at around 1,000 ppm is more than twice of that at around 385 ppm. Secondly, using the described function, CO2 absorption by forests in the operating region of each electric power company was investigated with a simple model in which the atmospheric CO2 concentration around artificial forests was artificially increased up to 1,000 ppm, and the investigation was done for the following three cases: (a) Current forest land, (b) Forest land with twice artificial forest land area and (c) Forest land with new species of artificial forests. In the case of (a), the CO2 absorption by forests is 111 million tonnes that is increase of 39% over the current one (80 million tonnes). As to the case of (b), the CO2 absorption by forests is 137 million tonnes that is increase of 70% over the current one. And then, for the case of (c), the CO2 absorption by forests is 218 million tonnes that is increase of 170% over the current one. It follows from these arguments that the CO2 absorption by forests much depends on the atmospheric CO2 concentration around the forests, and will be effectively promoted by an easy artificial treatment. Those results here might be useful to design a biomass energy carbon capture storage system toward a sustainable society.

References 1. National Greenhouse Gas Inventory Report of Japan, Center for Global Environmental Research (CGER) and National Institute for Environmental Studies (NIES), April 2010 2. Monthly report on electric power statics, Japan Electric Association, 2004–2009 3. Monthly statics of agriculture, forestry and fisheries, Ministry of Agriculture, Forestry and Fisheries of Japan, 2007 4. Yazaki K et al (2004) Tree Physiol 24:941–994

2050 ASEAN Electricity Demand: Case Study in Indonesia and Cambodia Nuki Agya Utama, Keiichi N. Ishihara, Qi Zhang, and Tetsuo Tezuka

Abstract  ASEAN (Association of South-East Asian Nations) member countries are predicted to become a net importer of oil in the next 15–20 years. Therefore it is important to predict the future electricity demand in the region. However, predicting future electricity demand entail various issues and, one of them is its uncertainty. This study serves to reduce the uncertainties of predicting future electricity demand in the least and developing countries under ASEAN. Introducing the time-series relationship between economic and energy as an input in key parameters and GDP parameters on causality runs from economic to electricity and bi-directional economic and electricity. The result is then applied to predict the future electricity demand trend and is used as reference scenario. Policy, household size, power generation cost, etc are used as key assumption. Granger-causality test proves to be useful in order to predict the future electricity demand trend in Cambodia with the errors during 2005–2008 periods merely 5–7% compares to the actual data. While in Indonesia the error for 2000–2008 predictions compare to the actual demand which is accounted 8% in average. Keywords  Cambodia • Electricity • Indonesia • Supply–demand scenario

1 Introduction Although having more than 28,000 billion barrels of oil reserve, ASEAN (Association of South-East Asian Nations) member countries is predicted to become a net importer of oil in the next 15–20 years. Oil price boom in 2007–2008

N.A. Utama (*), K.N. Ishihara, Q. Zhang, and T. Tezuka Graduate School Energy Science, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan e-mail: [email protected]

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2050 ASEAN Electricity Demand: Case Study in Indonesia and Cambodia

33

was a crucial moment for the policy maker in ASEAN member countries, to consider how to swift its dependency from fossil fuel to other alternatives fuel. Moreover, according to the prediction by Asian Center of Energy (ACE) [1], the share of generation mix in the region will move towards non-oil fuels. In 2020, almost 45% of the fuel for mix generation in ASEAN will be coal, followed by 40% in natural gas and 1.5% is oil. The rest of the primary will be either renewable energy or nuclear. Thus, it is important to show a possible future energy scenario independent of fossil fuel in the member countries. The purpose of this study is predicting electricity demand and developing scenarios for ASEAN countries, the reference scenario development by utilizing the causality test on the time series of electricity demand and economical growth. Scenario planning frequently consists of three typical growth scenarios, high, low and medium (moderate); these types of scenarios sometimes are dangerous since most of the people thinks that the moderate one is most likely happens [2]. Moreover, to a great extent, forecast errors are led by wrong growth rate expectations, which have materially caused big forecast errors [3]. Yoo, emphasized that even there is a strong relationship between electricity consumption and economic growth it does not necessarily imply a causal relationship. The causal relationship may very well run from electricity to economic and/or economic to electricity [4].

2 Methodology In order to reduce the uncertainty and burden on the predicting the future using key assumption, some measures were used, such as Granger-causality test (describes below) and data gathering on the related organization. The diagram explaining the methodology of the study is shown in Fig. 1.

Fig. 1  Methodology graph on the predicting the future electricity demand

34

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2.1 Data Collection on GDP, Population and Electricity Consumption To test the causality relationship, the historical data in the countries, such as GDP, income per capita and electricity consumption are collected. The data were taken from the statistical sources such as Asian Development Bank (ADB) [5], World Bank [6], United Nation [7], and International Energy Agency [8]. Other micro parameters such as diffusion of home appliances and the yearly electricity consumption, data on electricity power generation such as reserve planning, load, fuel mix electricity generation, capacity etc. were also taken into account. Moreover, the Indonesian data was taken from [9] and [10].

2.2 Granger-Causality Test and LEAP Granger-causality test was performed to detect any presence of a causal relationship between electricity use and income (GDP per capita). Many evidences proved that the uni-directional causality does not always run from energy to economics. In case of Cambodia and Indonesia [11–14], energy demand are driven by their economic growths. Therefore the test can be used to check whether the electricity demand can be predicted by using the country’s economic trends. LEAP (Long-range Energy Alternative Planning) is a scenario-based energy-environment modeling tool. Its scenarios are based on comprehensive accounting of how energy is consumed, converted and produced in a given region [15]. In the development of the scenario LEAP is used, to predict the future electricity demand based on the current input on GDP (for uni-direction, I → E and E → I causality). The yearly growth for input such as the population and electricity demand is predicted. The growth prediction is crucial point in LEAP since the tools only calculate based on the input parameters. For the development of electricity demand scenarios the electricity consumption growth for appliances was also predicted.

3 Result and Discussion 3.1 Granger Causality Relationship Between Electricity Consumption and Income Growth (Represent by GDP Per Capita) The relationship between electricity consumption and economic growth in the region is calculated, such as uni-directional causality between electricity and economic growth (causality runs either way between both parameters; represent by ‘→’ sign),

2050 ASEAN Electricity Demand: Case Study in Indonesia and Cambodia

35

bi-directional causality (causality exist for both parameters; represent by ‘↔’ sign) as well as no causality at all (no influence between both parameters), which is summarized in Table 1 with reported values. The missing findings and unbalance result are filled by own calculation. There are a number of evidences to support bi-directional or uni-directional causality between electricity consumption and income (GDP per capita). The evidence shows for most of the least developing countries such as Myanmar, Cambodia and Lao PDR has the similar causality; income causes the increase of electricity consumption. Table 1 shows that electricity and income is bi-directional causality (means both have significant influence to effecting one to another [14]). Most of the evidence for Indonesia shows that the income is also influencing the electricity consumption except [16] and [17]. The share of the residential sector in the electricity consumption for Cambodia, Lao PDR and Indonesia is 47%, [8] 40% [18] and 42% respectively [9]. However in Myanmar, the empirical evidence proves that not literally income leads to electricity consumption even the residential electricity consumption share reach almost 40% [8]. The industrial share also plays important factors to predict

Table  1  Empirical result summary of the ASEAN member countries (E = Electricity/Energy; I = Income)

Brunei Darusalam [14] This study Cambodia This study Indonesia [11] [12] [17] [19] [13], [14]

Indu strial com merc ial

I

El. Share [%] resid entia l

I E

50 55 60 65 70 75 80 85 90 95 00 05

E

Sources

E

Countries

Causality

I

Study period (1950-2005)

13

19

68

47

16

37

42

40

18

This study [14] [13] [11]

40

39

10

20

50

30

[11] This study The Philippines [20] [12] [17] [19] [14] This study [11] Singapore [21] [13] This study Thailand [20] [22] [17] [19]

39

42

19

35

35

30

20

38

41

21

46

32

42

47

9

This study Lao PDR Malaysia

Myanmar

Viet Nam

[13] [14] This study

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the causality from energy to income as Myanmar share of electricity in industry reach 42% in total, therefore the relationship can be both ways (bi-directional). On the other hand, the most developed countries in the region (Brunei and Singapore) show the bi-directional cause [13, 14, 19]. It means that both parameters are influencing one to another, this is due to the high share of non-residential (industrial and commercial) electricity consumption in Singapore and Brunei 79 and 87% respectively [8] (Table 1). In some countries in the developing category such as Thailand, The Philippines and Malaysia the relationship on causality through empirical evidence is mostly bi-direction (energy and income are cause related each other), except [4] in Thailand (I → E) and [20] (E → I), [14, 21] in The Philippines (E → I), [20] (E → I) and [14] in Malaysia (I → E). The trend for bi-directional causality is attributable to the high share of industrial sector more than 30% and the low residential sector share less than 35%.

3.2 Case Study on Demand Scenarios; Cambodia The national GDP is predicted by ADB in average of 7% per year up to year 2020 and assuming to be steady 5.5% in the following years up to 2050. The percentage share of electricity in the base year (2006) is residential sector (more than 45% share) follows by commercial in 35% and the remaining is industrial sector. Cambodia’s current GDP reaches 16.39 billion US$, while the population in the same year reaches 13.28 million and creates the GDP per capita, 1,234 US$. With the average household size 5.25, the number of Cambodian household was about 2.53 million. The annual population growth accounts 1.7% and reduces up to 1.5% in year 2050 with the 14% household share in urban and the remaining 86% in rural. The electrification ratio in urban is higher than rural areas, 75% urban household get access to the electricity, while only 9% in rural have access. The use of electricity in urban areas is vary from air conditioning (AC) up to microwave, cooling fan has the biggest percentage share of the electricity consumption in the household follows with the lighting and AC [22]. In commercial sector the AC has the biggest share of electricity consumption and followed by lighting. Moreover, for the un-electrified areas, the biggest share of primary energy is kerosene use for lighting, whereas wood biomass and charcoal use for cooking. Same study shows the highest number of appliances use in household is cooling fan follows by entertainment appliances (TV, radio and computers). The AC reaches 2,571 kW h/household (HH)/year followed by lighting (1,110 kW h/HH/y) and cooling fan (833 kW h/HH/y). The efficiency scenario for lighting suggests to use fluorescent light bulb (currently accounted 5%) to replace incandescent bulb (currently accounted 95%), includes lighting management and automation in commercial and industrial sectors. The cooling scenario supports active and passive system for reducing cooling electricity consumption through; (1) green labeling appliances, (2) building codes; envelopes form and materials and interior improvement.

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Fig. 2  (a) Cost comparison on electricity demand scenarios in 2050 in Cambodia and (b) energy cost estimation for Indonesian supply scenarios in 2050

The result on cost estimation (Fig.  2a) in 2050 shows by improving building codes, utilizing green labeling for cooling appliances and implementing passive cooling for non air conditioned building will save 11 trillion US$ accumulatively up to 2050. In the same period by combining both scenarios the accumulated amount of money can be saved approximately 15 trillion US$.

3.3 Case Study on Supply Scenarios; Indonesia The future electricity demand growth is estimated using trend from economic growth in average of 6.84% up to 2050. Other key assumptions are used for the base year, such as 205 million populations with 1.12% growth, 52 million household, 79% living in urban by the end year estimation (United Nations). The base year electricity consumption on residential, commercial and industrial sectors is taken from IEA [8]. Current capacity is accounted to 21  GW and assumes to be increase up to 415.6 GW in 2050 (in line with the demand measurement). The transformation and distribution loses accounted 11.5% [9] and will reduce to 9% in 2050. The medium target of electricity generation mix from the Indonesian government is used as a reference up to 2025 [10], the electrification currently is 65% and will reach 100% in 2050, with assumption of 86% grid connection and 14% off grid. Current reserve margin accounts 9% and will increase (as the PLN target) up to 30% in 2050. The reference scenario was developed by utilizing the electricity mix and capacity based on the government energy roadmap in 2008. Moreover, the other scenarios are categorized as follows: (1) Coal scenario, uses mainly coal which assume that the percentage of coal power generation reach 80–90%. (2) Nuclear scenario, where 50–60% of electricity will be covered by nuclear power generation follows by 30% share of coal based power plant in and keep maintaining the percentage of renewable energy based power plant on 2025 roadmap. (3) Renewable energy

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scenario, by optimizing the renewable energy (RE) potential on 20% hydro and 32% (solar, biomass, geothermal and wind combined) and rely the remaining percentage with natural gas (NG) and coal (29% and 18% respectively). (4) Best cost scenario, by maximizing the RE potential (reducing solar potential to 10% compare to 15% in RE scenario) and utilizing more natural gas (40%) and reduce nuclear to 0%. As seen in Fig. 2b the best cost scenario has higher expenses (especially during investment cost) in the first 8 years in around 3.8 billion US$. However, the scenario will save approximately 24.7 billion US$ in total.

4 Conclusion Due to its economic development, increases of population and household in Cambodia leads to the high share of electricity demand comparing to commercials and industrial sectors; Moreover, low electricity consumption in industrial sector causes from high percentage of share for industry with low electricity intensity (agro and garment industry). Demand scenarios on lighting and cooling shows efficient to reduce the cost of electricity in the future. However, it needs huge investment to replace the current appliances as well as capacity building to introduce building codes in the country. In Indonesian case, the actual consumption and prediction (this study) (2000– 2008) shows 8% errors in average. The maximum utilization of RE potential proves to have relatively low cost; however its capacity could not fulfill the need of electricity demand in 2050. Comparing to the reference scenario, the best cost scenario results US$ 24.7 billion in total reduction, by increasing the share of NG and reducing the share of coal (from the RE scenario). The development of small to medium power generation is more beneficial rather than huge investment in one or two big power generation. Increasing the capacity for coal and NG based power plant can increase the potential for small to medium power generation with low cost investment. NG and coal based power plants are good option for long term plan option in the country, with the consideration of small capacity. For Nuclear, in order to reduce the cost the country should have its technology know how (particularly human resources) rather than ‘cradle to the grave’ imported human resources and technology.

References 1. ASEAN Center for Energy (ACE) (2005) Electricity and development in ASEAN. ASEAN Energy Bull 9:3–4 2. Soontornrangson W, Evans DG, Fuller RJ, Stewart DF (2003) Scenario planning for electricity supply. Energy Policy 31:1647–1659 3. Linderoth H (2002) Forecast errors in IEA-countries’ energy consumption. Energy Policy 30:53–61

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4. Yoo SH (2006) The causal relationship between electricity consumption and economic growth in the ASEAN countries. Energy Policy 34:3573–3582 5. Asian Development Bank (ADB) (2009) Cambodia: enhancing governance for sustainable development. Available at http://www.adb.org 6. World Bank Database (2009) Economy watch, data on GDP Available at http://www.economywatch.com/world_economy/. Accessed June 2009 7. The United Nations Statistics Division (UNSD) of the Department of Economic and Social Affairs (DESA) (2009) Data on population, electricity consumption and GDP. Available at http://data.un.org/ 8. International Energy Agency (IEA) (2008) Energy statistic of non-OECD countries, IEA Statistic 9. Stated Owned Electricity Company (PLN) (2009) Statistics. Available at http://www.pln. co.id 10. Ministry of Energy and Mineral (2009) National energy policy, Directorate General of Electricity and Energy Utilization, Ministry of Energy and Mineral Resources 11. Murry DA, Nan GD (1996) A definition of the gross domestic product – electrification interrelationship. J Energy Dev 19–2:275–283 12. Masih AMM, Masih R (1996) Electricity consumption, real income and temporal causality: results from a multicounty study based on co integration and error correction modeling techniques. Energy Econ 18:165–183 13. Yoo SH (2006) Electricity generation and economic growth in Indonesia. Energy 31:2890–2899 14. Chontanawat J, Hunt LC, Pierse R (2008) Does energy consumption cause economic growth?: evidence from a systematic study. J Policy Model 30:209–220 15. Long-range Energy Alternatives Planning System (LEAP) (2006) User guide, Stockholm Environment Institute, March 2006 16. Asafu-Adjaye J (2000) The relationship between energy consumption, energy prices and economic growth: time series evidence from Asian developing countries. Energy Econ 22:615–625 17. Fatai K, Oxley L, Scrimgeour FG (2004) Modeling the causal relationship between energy consumption and GDP in New Zealand, Australia, India, Indonesia, the Philippines and Thailand. Math Comput in Simul 64:431–445 18. Ministry of Energy and Mines LAO PDR (2006) Overview of energy subsector activities in the Lao PDR, Sub regional energy forum-2 HoChiMinh, Viet Nam, 22 November 2008 19. Glasure YU, Lee AR (1998) Cointegration, error-correction, and the relationship between GDP and electricity: the case of South Korea and Singapore. Resource Energy Econ 20:17–25 20. Masih AMM, Masih R (1998) A multivariate cointegrated modeling approach in testing temporal causality between energy consumption, real income and prices with an application to two Asian LDCs. Appl Econ 30–10:1287–1298 21. Yu SH, Choi JY (1985) The causal relationship between energy and GNP: an international comparison. J Energy Dev 10:249–272 22. Sovanndara N (2002) Household electricity use analysis and forecasting: the case of Phnom Penh, Cambodia. Unpublished Master Thesis, The Joint Graduate School of Energy and Environment (JGSEE), Thailand

Proposal of a Method for Promotion of Pro Environmental Behavior with Loose Social Network Saizo Aoyagi, Tomoaki Okamura, Hirotake Ishii, and Hiroshi Shimoda

Abstract  Recently, environmental and energy problems, which are typified by global warming, have grown into serious problems. In Japan, CO2 emission of residential sector however is relatively at high level. Consequently, decrease of CO2 emission by Pro Environmental Behavior (PEB) in households is necessary. The purpose of this study is proposal of a method for promotion of PEB in households, which consists of (1) presentation of appropriate PEB depending on place and time and (2) loose social network of PEB footprint communication using portable devices (iPhone). The proposed method was practiced in a Japanese home with a participant. From the result, we confirmed that the proposed method promote PEB through the experiment. Other experiments with several participants and long periods are planned now because the experiment had only one participant and the period of the experiment was too short to confirm continuance. Keywords  Awareness • Cellular phone • Loose social networks • Pro Environmental Behavior (PEB)

1 Introduction Recently, environmental and energy problems, which are typified by climate change, have grown into serious problems and CO2 emissions have to be decreased in various sectors in order to solve the problems [1]. In Japan, CO2 emission of industrial sector has been decreased, that of residential sector however is relatively at high level [2]. Consequently, decrease of CO2 emission by Pro Environmental Behavior (PEB) in households will contribute to solving environmental and energy problems greatly. S. Aoyagi (*), T. Okamura, H. Ishii, and H. Shimoda Graduate School of Energy Science, Kyoto University, Yoshida-honnmachi, Kyoto 606-8501, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_5, © Springer 2011

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There are some studies about promotion of PEB of people. Conventionally, such studies regard people’s environmental attitude or consciousness as a key factor to promote their PEB [3]. Nevertheless, recent studies revealed that cultivation or change of environmental attitude of people is not sufficient for promotion of their PEB [4, 5], and new approaches are necessary. Purpose of this study is proposal of a method for promotion of PEB, which is characterized by presentation of available PEB depending on place and time, and footprint communication in loose social network.

2 Proposal of a Method for Promoting Pro Environmental Behavior 2.1 Existing Studies of Promotion of PEB in Households There are some studies about what are needed for promotion of PEB in addition to cultivation of environmental attitude or concern. Blake [5] pointed out that there are three barriers between environmental concern and PEB, named individuality such as laziness or lack of interest, responsibility to PEB, and practicality such as lack of information. Based on the study of Blake, Yi proposed an approach of promote PEB of people and examples of the system as implementation of the approach, which consists of two parts [6]. First, the approach employs some computing devices which provide information to people in order to break barriers of responsibility and practicality. For example, the provided information is about energy consumption of people, which shows how much energy can be saved by PEB. Next, the approach employs social networking sites and online community such as Facebook (http://www. facebook.com) which is an area of exchange of information of PEB or mutual reporting of PEB experience of users in order to break the barrier of individuality through psychological bandwagon effect. Bandwagon effect is similar to conformity [7], and the fact that other people do PEB can work as the reason why people do PEB by the effect. The approach of Yi is considered to be effective for promotion of PEB. Nevertheless, there are some problems in the approach. First, these two parts, computing devices for energy information and online community are not integrated, users of these system therefore have to get information from the computing devices, and put the information to online community by themselves in addition to PEB. These behaviors bother people, and it may decrease people’s intention to do PEB rather than promote PEB. So integration of two parts, such as automatic information sending, is required as mentioned by Yi himself [7]. Second, we consider that information, which is given to people by devices are insufficient. These are just information about energy consumption, and are not information about what, how and when to do PEB. Therefore, users of the system have to determine their behavior by themselves.

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Components of the method

Purpose Promotion of PEB

Awaking available PEB Band wagon effect

Presentation of appropriate PEB depending on place and time Using portable devise Loose social network of PEB foot print communication

Fig. 1  An overview of the proposed method

2.2 The Proposed Method for Promotion of PEB Based on the above discussion, we propose a method for promotion of PEB, which includes two components as shown in Fig. 1. The first component is presentation of appropriate PEB depending on place and time using portable device such as iPhone. Using the system, an appropriate PEB is presented to users of the system in appropriate timing by a mobile device. For example, when a user starts to cook with gas stove, a mobile device of the user presents a PEB about saving gas. The information which is presented by the proposed method is so rich that users can know what, how and when to do PEB. The second component is loose social network of PEB footprint communication. PEB footprint means the fact a user did a PEB, which is communicated to other users in our definition. Loose social network means a kind of social networking system, which is characterized by dealing with only a few information such as twitter (http://www.twitter.com) in our definition. Therefore, loose social network of PEB footprint communication means a kind of social network where users communicate the fact they did PEB to other users. The social network will invoke bandwagon effect, which promote PEB of people. In addition, these two components of the proposed method are completely integrated. As mentioned above, presentation of appropriate PEB is conducted by a mobile device, loose social network is also accessed using a mobile device. Moreover, presentation of PEB and access to the loose social network can be integrated in dedicated client software which can tell the fact he/she do PEB to other users who use the system with just a single touch a button.

2.3 Implementation of the Method and System Configuration We implemented the proposed method as an integrated system as shown in Fig.  2. First, the system included an iPhone for each user, and dedicated client software is installed into the iPhone. Users take along iPhone in his/her home. Next, Bluetooth station stations are placed in places where PEB are available, such as sink, toilet or refrigerator in users’ home. Moreover, Wi-Fi station is set in user’s home for connecting

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Portable devise(iPhone) User’s home(example)

User

Web server

Toilet refrigerator Bluetooth stations Sink

Wi-Fi station

Fig. 2  An overview of system configuration

iPhone and web server with Wi-Fi network, and the system employs a web server which have dedicated server software with database of a list of PEB and its appropriate place and time, place information of Bluetooth stations, and log of user’s behavior. When the system presents an appropriate PEB to users, it works as follows: 1 . A user comes close and enter into an area of a Bluetooth station in daily life. 2. When iPhone recognizes entering, asks web server about what PEB is available in this place and this time. 3. Web server returns a PEB to iPhone, and iPhone present a PEB to the user. Next, the system provides loose social network of PEB footprint communication as follows: 1 . Many users concurrently use the system (for example, 1,000 users). 2. When a user do PEB, he/she can put a PEB footprint with just a single touch a button. Users can add some comments to a PEB footprint. 3. PEB footprints are shown to other users as timeline like twitter. PEB footprints are just declarations of PEB to all users, and there are no obligations to reply or “deep” communication.

3 Field Practice of the Proposed Method 3.1 Purpose and Method Purpose of the practice is to confirm that the proposed method promote PEB. We define “promotion of PEB” as “a participant starts to PEB or increases frequency of PEB through the practice” in this study. The period of practice was about a week

Proposal of a Method for Promotion of Pro Environmental Behavior 100%

1

1

90% 80%

16

70% 60% 50% 40% 30% 20% 10% 0%

10

1 2 7

had no occasions

8

Not do at all Less likely do

29

Sometimes do Often do Always do

5 Pre questionnaire

no answer

6

4 15

47

Post questionnaire

Fig. 3  Comparison of frequencies of 53 PEBs between pre questionnaire and post questionnaire

from 2010 August 3th to August 10th. Participant is a Japanese woman and ten confederate participants were played by one of the authors in the loose social network of the system. The system of the proposed method was set in her home and 53 PEBs were presented to the participant. Pre questionnaire and post questionnaire were conducted to reveal frequency of participants’ PEB. In addition, participant’s PEB footprints were recorded in order to confirm their actual PEB history.

3.2 Results and Discussion Figure  3 shows Frequencies of 53 PEBs between pre questionnaire and post questionnaire of the participant. We can find that the frequency increased through the practice. In particular, the number of PEBs that were answered as “always do” increased greatly and that of “Not do at all” dramatically decreased from 16 to 2. Figure 4 shows the number of PEB footprints of the participant in the experimental period. We can find sudden decrease in August 7th. This is because participant misunderstood how to use PEB footprint, before 7th. She put footprints without doing PEB. We therefore improved sentences for explanation of how to use PEB footprints in the system in order to avoid misunderstanding in 7th. After that, about ten footprints were recorded in a day.

4 Conclusion In this study, we proposed the method for promotion of PEB with loose social network and practiced with a participant in actual Japanese home. From the result, we confirmed that the proposed method promote PEB through the experiment.

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the number of PEB footprints 100 90 80 70 60 50 40 30 20 10 0

8/3

4

5

6

7

8

9

10

Date

Fig. 4  The number of PEB footprints in the experimental period

Other experiments with several participants and long periods are planned now because the experiment had only one participant and the period of the experiment was too short to confirm continuance.

References 1. IPCC (2007) IPCC fourth assessment report: climate change 2007 2. METI (2008) 2007 Annual energy report 3. Nishino S, Sumida K (2004) Scaling for measurement of attitude toward environmental education. J Home Econ Jpn 55(10):815–822 4. Hirose Y (1994) Determinants of environment-conscious behavior. Res Soc Psychol 10(1):44–55 5. Blake J (1999) Overcoming the ‘value-action gap’ in environmental policy: tensions between national policy and local experience. Local Environ 4(3):257–278 6. Yi B (2009) Persuasive technology in motivating household energy conservation, Business aspects of the internet of things seminar of advanced topics FS 2009, 52–58 7. Latane B (1981) The psychology of social impact. Am Psychol 3–4:343–356

Performance Analysis Between Well-Being, Energy and Environmental Indicators Using Data Envelopment Analysis Jordi Cravioto, Eiji Yamasue, Hideki Okumura, and Keiichi N. Ishihara

Abstract  Data Envelopment Analysis (DEA) has been applied to know the performance of 40 countries in terms of energy, environmental and well-being related indicators. The method used is a basic Charnes, Cooper and Rhodes (CCR) DEA model applied to countries treated as Decision Making Units (DMUs) with two energy related indicators as inputs and one well-being indicator as output. The variables were selected based on correlations between seven energy-environmental indicators, and eight well-being indexes. From the correlations, two DEA models were constructed and compared. The first one, named “Production” DEA model, using electricity consumption per capita and CO2 emissions per capita as inputs and GDP per capita as output. The second one, “Development” DEA model using the same inputs but Human Development Index (HDI) as output. Results show that most developed countries compared to the others have low efficiency in the production model and even lower results in the development one. Among the “best” performing countries were Costa Rica, Ghana and the Philippines for the production model, and Tanzania and Nigeria for the development one. Keywords  CO2 emissions • DEA • Electricity consumption • Well-being indicators

1 Introduction During the past 25  years, alternative measures have been proposed to substitute GDP as a proxy to measure well-being. The theoretical idea behind some is that the link to limited amount of resources and environmental degradation is not accounted

J. Cravioto, E. Yamasue, H. Okumura, and K.N. Ishihara (*) Graduate School of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto, 606-8501, Japan e-mail: [email protected]; [email protected]; [email protected]; [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_6, © Springer 2011

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within the production measurements. Others believe that the level of well-being cannot be measured through production proposing alternative indexes more related to variables involved with development (HDI) or direct surveying quality of life or satisfaction (LSI). In any case, current societies utilise resources and energy as supply for the production of goods necessary for daily life, and these goods have an effect on the level of well-being of the individuals and their community. The relationship between these well-being indexes and energy consumption is therefore complex and not straightforward, and the assessment of performance from communities is a difficult task to undertake. In recent years, however, a mathematical programming technique called Data Envelopment Analysis (DEA) has proved to be useful to compare performance among similar decision making units (DMU) based on efficiency relationships of correlated inputs and outputs. It has been applied in a range of studies exploring the efficiency of energy provision [1], consumption [2] or environmental performance [3], but fewer works have explored socio-economic performance [4] or well-being performance in terms of energy resources use. This research is therefore intended to provide a performance comparison among a set of countries in terms of energy consumption and CO2 emissions to production and well-being levels.

2 Method 2.1 Sample and Index Selection The selection of the sample included 40 countries representative of the five continents. This sample is intended to be symbolical in terms of cultural and size diffe­ rences. Table 1 shows the selected countries. From several economical indicators and well-being indexes, Table 2 shows those selected based on data availability for the sample. Energy related indicators are also included in the table.

2.2 Correlation Analysis A correlation analysis applied to the sample with data for 2007 showed that the strongest correlations were found for production and energy supply: GDP with energy related indicators. However, some correlations were also found among HDI, GINI and QLI with electricity consumption per capita (Electricity/pop) and CO2 emissions per capita (CO2 /pop). Table 3 shows an outline of selected correlations coefficients. For this paper, two relations have been selected. The first one, GDP/pop with Electricity/pop and CO2 /pop forming what will be described later as the “Production” DEA model. And second, HDI with Electricity/pop and CO2 /pop forming the “development” DEA model.

Performance Analysis Between Well-Being, Energy and Environmental Indicators Table 1  Countries in sample Asia/Oceania Europe Uzbekistan Spain India Russia Indonesia Poland China Greece Japan Bulgaria Korea Turkey Malaysia Germany Philippines France Thailand UK Australia Italy New Zealand Sweden Norway

Africa/Middle East Morocco Nigeria Tanzania South Africa Ghana Iran Saudi Arabia Israel

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Americas United States Mexico Canada Brazil Argentina Venezuela Chile Jamaica Costa Rica

Table 2  Well-being, environmental and energy indexes and indicators Well-being related Energy related Environment related indicators/indexes [5] indicators/indexes [6] indicators/indexes [6] Total Primary Energy CO2 emissions Gross Domestic Product (GDP) Supply (TPES) GDP per capita (GDP/pop) Electricity consumption CO2 emissions per capita (CO2 /pop) Human Development Index (HDI) [7] Electricity consumption per CO2 emissions per GDP capita (Electricity/pop) (CO2 intensity) Satisfaction with Life Index (LSI) [8] Energy Depletion Index CO2 emissions per TPES (EDI) [5] Quality of Life Index (QLI) [9] Happy Planet Index (HPI) [10] GINI Index

Table 3  Correlation coefficients between selected indexes and indicators HDI QLI GINI LSI 0.67 0.69 −0.56 0.42 Electricity/pop CO2 /pop 0.66 0.49 −0.39 0.32

GDP/pop 0.87 0.72

2.3 Data Envelopment Analysis Models Data Envelopment Analysis (DEA) is the mathematical tool used in this paper to evaluate the performance of countries in terms of how they use inputs to generate an output. By creating a linear programming model from efficiency relations of the inputs and the output, the relative efficiency can be calculated for each country. The ground concept is the efficiency factor where each output is related to the input as shown in (1) [11].

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max(Em ) =

∑v j =1

jm

y jm

I

∑u i =1

x

im im

subject to J

0≤

∑v j =1

jm

y jn

I

∑ uim xin

≤ 1; n = 1,2...N

i =1



v jm , uim ≥ 0; i = 1,2...I ; j = 1,2...J ;1 ≤ m ≤ n

(1)

Where Em is the efficiency of the mth country, yjm the jth output of the mth country, vjm is the weight of that output, xim is ith input of the mth country, uim is the weight of that input, yjn and xin the jth output and ith input respectively of the nth country and N the total number of countries. When evaluating the problem the efficiency of the mth country can be obtained. When some outputs are undesired in the performance, like the case of pollution or emissions, the simplest case is to treat them as an input as described by Cooper et al. [12] and valuate performance. This approach is adopted in this paper to deal with emissions as a product of electricity production. 2.3.1 Production DEA Model If for each country, electricity consumption per capita and CO2 emissions per capita are treated as inputs and GDP per capita as the only output, as an example (2) shows the mathematical expression for country A. max E A =

3.79vGDP , A 13.6uElect ., A + 19.10uCO2 , A

subject to 0≤ 0≤ 0≤ 0≤

37.9vGDP , A 1.36uElect ., A + 19.10uCO2 , A 11.1vGDP , A 0.2uElect ., A + 4.14uCO2 , A

≤1

31.7vGDP , A 1.69uElect , A + 17.37uCO2 , A 7.6 vGDP , A 0.23uElect , A + 4.57uCO2 , A

… n = 40

≤1

≤1 ≤1

(2)

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Where EA is the efficiency of country A, 37.9 the output (GDP/pop) in thousands of USdls per capita, 1.36 input No.1 (Electricity/pop) in MW h per capita, 19.10 input No.2 (CO2 /pop) in tons of CO2 per capita, vGDP,A the weight of the output, uElect,A the weight of input No.1 and uCO ,A the weight of input No.2. The aim of the 2 problem is to find vGDP,A, uElect,A, uCO ,A such that EA is maximum subjected to the 2 constraints of efficiencies of the other 40 countries (n=40). To obtain the efficiency of each of the other countries the same linear programming model is used until the valuation of the 40th country (when m=n). Results are named “production” performance. 2.3.2 Development DEA Model In this model, HDI takes the place of the country’s output while electricity consumption per capita and CO2 emissions per capita remain as inputs. The mathematical expression for country A does not change from (2) except for the factors used in the numerator for each country. The output is 0.955 (HDIA) for country A, 0.849 (HDIB) for country B, etc. The performance results are named “development” results. 2.3.3 Assumptions in the Model The general assumption when using a DEA model is that if one DMU is the most efficient to obtain outputs from inputs, the others should be able to do it in the same way. Therefore, this comparison between countries assumes that all are equally capable of obtaining their production outputs or development achievements using their inputs. Other assumptions are those implied when using the basic CCR model.

3 Results and Discussion Figure 1 shows a graph with performance results from both DEA models. In the graph except for Sweden, Norway and France most developed countries have efficiencies below 60% in the production model and lower in the development one perhaps associated with lower CO2 emissions and electricity consumption of these countries. Only two countries had performance over 70% in both models (Nigeria, Tanzania) which means their electricity consumption and CO2 emission is the smallest compared to their achievements in economic growth and development. This effect not only suggests that electricity consumption and emissions in all low efficiency countries are less significant for production, but also less meaningful to their development as measured with HDI. Future policy measures therefore should aim at reducing inputs to attain a better performance in both models.

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Development DEA Performance [%]

100

Tanzania Uzebekistan Jamaica Russia Bulgaria S. Africa Venezuela Canada Australia USA Malaysia

80

60

40

Korea China Iran Polonia New Zealand Chile Thailand Japan Greece Germany

Spain Turkey UK Italy Mexico Argentina

Nigeria

Ghana Indonesia India

20

Morocco France

0 0

20

40

60

Philippines Brazil Norway 80

Costa Rica Sweden 100

Production DEA Performance [%]

Fig. 1  Development to production performance in country sample

4 Conclusion The best performing countries in the production model were Costa Rica, Ghana and the Philippines whereas Tanzania and Nigeria were for the development one. Other countries show lower efficiency performance in both DEA models meaning less significant impact of electricity and CO2 emissions to wealth or development achievements. Acknowledgement  The authors would thank Japan’s MEXT and Kyoto University Global COE Program “Energy Science in the Age of Global Warming” for their financial support.

References 1. Hu J-L, Wang S-C (2006) Total-factor energy efficiency of regions in China. Energy Policy 34:3206–3217, Elsevier 2. T-l Yeh, T-y Chen, P-y Lai (2010) A comparative study of energy utilization efficiency between Taiwan and China. Energy Policy 38:2386–2394, Elsevier 3. Zhou P, Ang BW, Poh KL (2008) Measuring environmental performance under different environmental DEA technologies. Energy Economics 30:1–14, Elsevier 4. Golany B, Thore S (1997) Restricted best practice selection in DEA: an overview with a case study evaluating the socio-economic performance of nations. Ann Oper Res 73:117–140, J.C. Baltzer AG, Science Publishers 5. The World Bank (2009) World development indicators 2009. CD-Rom

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6. IEA (2009) Energy statistics of OECD and non-OECD countries 2009. IEA Publications 7. United Nations Development Programme (2009) Human Development Report 2009. Overcoming barriers: human mobility and development. ISBN 978-0-230-23904-3, UNDP 8. White A (2007) A global projection of subjective well-being: a challenge to positive psychology? Psychtalk 56:17–20, The data on SWB and SWLS were extracted from a meta-analysis by Marks, Abdallah, Simms and Thompson 9. Economist Intelligence Unit (2005) Quality of life index. The World in 2005, The Economist Newspaper Ltd 10. Marks N, Abdallah S, Simms A, Thompson S et al (2006) The Happy Planet Index 1.0. New Economics Foundation 11. Ramanathan R (2003) An introduction to data envelopment analysis, a tool for performance measurement. Sage, Thousand Oaks. ISBN 0-7619-9761-X 12. Cooper WW, Seiford LM, Tone K (2007) Data envelopment analysis: a comprehensive text with models, applications, references. Springer ISBN 978387452814

Municipal Solid Waste Management with Citizen Participation: An Alternative Solution to Waste Problems in Jakarta, Indonesia Aretha Aprilia, Tetsuo Tezuka, and Gert Spaargaren

Abstract  The verity that ascertains waste as one of the contributors to CO2 emission leads the discourse to enter the limelight. Formulating suitable waste management scheme for developing countries such as Indonesia would require careful considerations that take into account the specific local context. This paper argues that in view of decentralization planning in Indonesia, the roles of local government and citizens in waste management are more imperative than ever. It provides an overview of current practices in waste management that takes the perspectives of the citizens as the end-users and the government as the regulator. The practices of solid waste management in Jakarta are observed at the municipality and community level in order to suggest further approaches to enable the initiative as a sustainable long-term solution. Keywords  Community • Indonesia • Municipal solid waste • Public participation • Waste management

1 Introduction Waste is one of the sources of greenhouse gas emissions that contributes 1.4 Gt or 3% of the total CO2 emissions [1]. Although minor levels of emissions are released through waste treatment and disposal, the prevention and recovery of wastes avoids emissions in all other sectors of the economy [2]. Developing country

A. Aprilia (*) and T. Tezuka Department of Energy Science, Graduate School of Energy Science, Kyoto University, Kyoto, Japan e-mail: [email protected] G. Spaargaren Department of Environmental Policy, Wageningen University, Wageningen, The Netherlands e-mail: [email protected]

T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_7, © Springer 2011

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governments are facing various constraints in MSW management, therefore active public participation to support the household waste management is prerequisite. Currently there are 94 areas in Jakarta that already operate waste management with ‘3R program’. These areas can reduce waste of up to 485 t per day, which is around 7% of the total waste generation [3]. Among the areas that already undertake 3R program, there are several communities that are actively supporting the neighborhood-based waste management, such as Rawajati community. The purpose of this paper is to provide an overview of the current existing condition of municipal solid waste management with the particular focus on household wastes. For the purpose of this research, the three main actors behind the community-supported neighborhood based waste management in Rawajati were interviewed and the waste management practices at the community level are observed.

2 Operational System of Community Waste Management in Rawajati Rawajati ward is located in Pancoran district, South Jakarta. The ward has been successful in motivating the community to implement the autonomous community waste management program [4]. The organic wastes that are produced by the ten neighborhood units within one neighborhood clusters in which 686 households reside at Rawajati ward that are involved in the community-based waste management scheme is around 2.67  kg/ household. It consists of 60% organic waste, 28% inorganic waste, 2% hazardous waste, and 10% paper waste [5]. Based on field observation and discussion with the main actors of waste management in the community level, the operational flow of waste management in Rawajati is presented in Fig. 1 below.

Home Transfer station

Organic Communal Inorganic

Hazardous & chemical

Final disposal site

Waste residues

Recycled

Collection bin

Collected by Cleansing Department

Fig. 1  Household waste management flow in Rawajati community (Source: Analysis)

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3 Barriers of Community-Supported Neighborhood Based Waste Management 3.1 Barriers on Policy Citizen participation is an increasingly important factor in planning and development policies following the decentralization legislation in Indonesia. The capacity of citizens to plan and deliver services have immediate relevance as the country moves to a decentralized planning model following Law No. 22 and Law No. 25, passed in 1999, which were followed up with Law No. 32 year 2004 on Regional Governance. The enactment of these laws has changed Indonesia from a highly centralized state, with governance, planning, and fiscal management partially ‘de-concentrated’ to provincial government offices, to a decentralized state with autonomous power over these responsibilities ‘devolved’ to lower levels of government. From a policy perspective, successful decentralization rests on the assumption that citizens through their participation in civil society organizations will undertake many planning and service-delivery functions previously the responsibility of various levels of government [6]. The same notion of decentralization applies to MSW management in Indonesia, in which the laws that are devised by the state government are to be followed by regional regulations as guidelines for the technical implementation. Currently, the implementation of MSW management in Indonesia does not refer to any specific guidelines or require any regulations compliance since the policy formulation is still at early stage. The follow up of the laws that should be translated into regional policies are still underway, which are expected to provide effective baseline for devising regional policy that largely depends on specific regional context. According to the Government Regulation no. 03 year 2001, the regional government has the main authority to manage the wastes in their respective jurisdiction area [7]. The master plan of waste management in Jakarta is mainly based on two major laws: Law No. 18 year 2008 and the Medium Term Development Plan Jakarta Province year 2007–2012. In 2006, The Minister of Public Works issued a National Regulation no. 21/ PRT/M/2006 on the National Policy and Strategies for the Development of Waste Management System. This regulation addressed that the communities are potential to be involved in the waste management; however it is not yet systematically developed. Under this regulation, there are several policies that were devised; among others are the minimization of wastes optimally from the source and improvement of active roles of the society and private sectors as waste management partners. Further to this, the President of Republic of Indonesia enacted the Law No. 18 year 2008 on Waste Management, which defines wastes as the remaining of daily human activities and/or natural process in solid formation. This law was established considering the waste management to date that is not yet according to the methods and techniques of sustainable waste management, therefore resulted in negative impacts

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upon public and environmental health. It is stated in the law that waste has been a national issue so that the management should be done comprehensively and in integrated manner in order to give benefits economically, health benefits for the public, and environmentally safe, as well as to enable behavioral shift in the society. Article 3 of the law specifically mentions that waste management is conducted based on various principles, including sustainability, benefits, togetherness, awareness, and economic values. With regard to sorting, it is regulated under article 13, which states that the managers of residential areas, among others, must provide facilities for waste sorting. The Government Regulation that serves as the regulation for implementation of waste management, which is to be issued following the Law No. 18/2008 on waste management, is not yet released. Due to the unavailability of regulation, the municipalities continue to operate waste management scheme without proper mechanism or guidance. There are no stringent measures or law that regulates the sanctions against illegal dumping, improper treatment and disposal of waste. According to Law No. 18/2008, waste generation must be minimized from the source to reduce the burden of waste transport and disposal. The law also highlighted the importance of community in undertaking measures for waste reduction to minimize the burden of management and treatment. However, as these initiatives are still voluntary, not many communities are willing to apply the initiative. Financing the municipal solid waste management (SWM) operation would require hefty funds; however the government failed to impose retribution for waste management from the households. The financing of SWM largely relies on the Regional Budgets and based on the Regional Budget of Jakarta in 2010, the allocated funds for Cleansing Department is only 2.9% of the total Budget [8]. The communities are reluctant to pay retribution as they have already pay the monthly community waste management fee. There is little awareness on the role of Cleansing Department in MSW management.

3.2 Barriers on Technical Operations Cleansing Department encounters problems with regard to infrastructure, such as lack of waste trucks and 40% of the existing trucks are obsolete [9]. This condition results in the service cover that cannot reach all Jakarta residents. Another constraints encountered by the department is the lack of available financing for promotion of 3R and community waste management for the reduction of waste generation. The people of Jakarta have little or no awareness on the existing problems on waste, and as the case of any mega-urban, the population relies heavily on disposable goods for convenience purposes. In the case of Rawajati, due to rapid urbanization some of the residents are what is termed as ‘seasonal residents’ or temporary residents. The residents’ mobility is therefore high, which leads to the urgent need to frequent socialization of the community waste management initiative. The initiative to promote the activities would

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also require the commitment and willingness of the community, especially the community leaders, to approach the new residents to participate. However based on the interview with the leaders, the decreasing commitment is encountered, which hinders the attempts to sustain the initiative. This condition is partly due to the fact that their involvements are voluntary; therefore no incentives are available to reward their activities. Another aspect that hinders the operation of this initiative is due to some of the householders that are not willing to participate. The majority of households that are not participants are mostly those who are working full-time and claim for not having the luxury of time and energy to sort and recover their wastes for composting and recycling. It is also observed that due to the small reward for undertaking such initiative, householders with good socio-economic status tend to resent the invitation to participate. At the same time, the rest of the householders that are already participate in the initiative also faces reluctance to continue such practice due to the little incentives obtained from producing compost and recycled handicrafts. The production of goods are not rewarded with compensation that commensurate their time and energy to produce them. The women group also faces problems with regard to the marketing of handicrafts. The society still has reluctance on using recycled products due to esthetical reasons. Therefore there is a very limited niche market for selling such products in Indonesia. In regards to composting, there is also an issue due to the seasonal needs of compost, which is mostly during nursery or planting period. That said, composts are not always marketable all-year round, and there is the need to have storage facilities during non-planting period.

3.3 Prospects for Sustainability of Initiative The success and sustainability of community waste management largely depend on the commitment and dedication of the community leaders and members. The underlying reasons for householders to be involved in the initiative are comprised of several pull and push factors. The pull factors for the proactive involvement of the community leaders and members to manage their wastes, in addition to environmental concerns, is also compensation or incentives to commensurate their involvement. The sales of compost and recycled products generate revenues to the householders although the amount is relatively small. Additionally, the push factors are including the conditions of environment that is threatened by the improper treatment of wastes. The community has been facing several problems in the past due to the improper waste management. The burning of waste and the use of incinerators within the premises created major air pollution that reaped complaints from concerned citizens. Based on the observation, the commitment and involvement of community leaders and members is decreasing subsequent to the relatively successful operation since 2001. One of the solutions to address this issue is to enable successors to step in and lead the operations for a certain period of time. There is also the need to raise the awareness of the society on the current waste crisis faced by Jakarta in order to

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encourage voluntary measures on the reduction of waste at households. Several measures to ensure the sustainability of initiative may include the creation of incentives to be incorporated in the Regional Regulation, which could be direct such as additional income, or indirect incentives such as the provision of waste sorting bins, waste shredders, etc. To address the issue on the limited market availability, government and private sectors may take part in marketing of recycled goods. For instance is to establish regulation for manufacturers to take back packaging of their produced goods and to assist in exporting the recycled handicrafts.

4 Conclusions This research emphasizes on the importance of community support in the current waste management scheme in order to ease the burden of high volume of waste to be disposed at the landfill. Indonesia has applied decentralization planning model that signifies the major roles of local governments and citizen participation in the planning and delivery of public services. In terms of municipal waste management, the development of policy remains in its take-off stage. The state government already devised the national law that is yet to be translated into local regulations that serve as implementation guidelines on municipal waste management. The current implementation of waste management is lacking clear guidelines and is based on self-regulating mechanisms within the neighborhood units. Retribution from the citizens cannot be imposed due to unawareness on the roles of government in terms of waste management as the self-provisioning scheme occurs. Moreover, retribution is yet to be incorporated in the law and is not treated as a regulatory instrument. As such, the government relies heavily on Regional Budgets as the source of financing. Given the constraints of the government to provide full service to all aspects of the waste flows, the current mechanism to involve citizen participation is prerequisite and needs to be improved. The community waste management practices has demonstrated the possibility of active involvement of the community in reducing waste generation through various schemes. While collective citizen-participation evolves in the typically low-to-medium income community, it cannot prevail without the existence of market mechanism and appealing stimulus. Acknowledgments  The authors are grateful to the Global Centre of Excellence (GCOE) Program of Kyoto University’s Graduate School of Energy Science for the financial support of this research.

References 1. Stern N (2006) Stern Review: The Economics of Climate Change, UK Treasury 2. UNEP IETC (2010) Waste and Climate Change: Global trends and strategy framework, Osaka/ Shiga

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3. Cleansing Department (2010) 3R programme at neighbourhood and regional scales 4. Department of Public Works (2008) Best practices of solid waste management in Indonesia 5. Waste Management Task Force (2008) Integrated waste management in Rawajati ward, Pancoran, South Jakarta 6. Beard V (2005) Individual determinants of participation in community development in Indonesia. Environ Plann C Gov Policy 23:21–39 7. Jakarta Regional Government (2010) Regulation of the Jakarta Regional Government No. 03 Year 2001 8. Jakarta Provincial Government (2010) Regional Budget. Available online: http://www.jakarta. go.id/jakv1/apbd/browse/2010#browse 9. Cleansing Department (2010) Master plan of waste management in Jakarta

The Influence of the Electrification in Erdos Grassland in Inner Mongolia, China Wuyunga and Tetsuo Tezuka

Abstract  This paper is based on the questionnaire and interview of the nomadic family in Erdos Grassland of Inner Mongolia. This survey analyzes the change in nomadic lifestyle and culture by comparing daily activities and ethnic cultures between electrification and non-electrification families. Although a variety of activities in life have changed after electrification, the basic nomadic sense of value seems to have been preserved. Keywords  Electrification • Erdos grassland • Lifestyle change • Nomadic family

1 Introduction Inner Mongolia is in the north of China mainland. It is known as the largest pasture area in China. The dispersed residence peculiar to the nomadism in this large area has kept 75,000 people in non-electrified lifestyle [1]. Due to the disperse lifestyle and the volume of the renewable energy in local area, the local government started to introduce the independent power plant such as WHS (wind power home system) and SHS (solar energy home system) in order to improve the nomadic life by electrification in 1980 [1]. Thus, the electrical appliances such as radio, television, washing machine, refrigerator, rice cooker have become available for nomadic family. The use of the electrical appliance has not only improved their lives but also had a profound influence on the society and culture in various perspectives. Especially the information and communication appliances such as radio, television, computer and cell phone have changed the ethnic culture drastically with the information flow from modern society.

Wuyunga (*) and T. Tezuka Graduate School of Energy Science, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_8, © Springer 2011

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This paper investigates the change in lifestyle, society structure and ethnic culture in Erdos grassland with the electrification mainly based on the results of the survey about the way of living and thinking of the local people during two periods; one is from August 4 to 14 and the other is from August 17 to 25 in 2009. The samples of the survey are 40 nomadic families. Half of the samples are located 10  km or more away from the village. Since the family leader answered the questionnaire, the age of the sample in the questionnaire means the age of the leader. The survey also includes interviews for the local government in the period of August 17 to 19 in 2009.

2 The Possession of Electrical Appliance Table 1 shows the possession of electrical appliance. The battery-powered radio has also been applied in non-electrification area. It is verified that the television, light bulb and cell phone are possessed by all of the electrified families. The rice cooker is possessed by all families with the grid power or WHS of 300 W, while the washing machine prevails in all of the families with grid power. Young families of 20s, 30s are apt to possess every type of electrical appliances.

3 Changes in Lifestyle In order to clarify the changes in nomadic lifestyle, activities and ethnic culture, six non-electrification samples have been removed, and the number of available samples is 34.

3.1 Changes with the Introduction of the Television All answerers indicate that they have got more opportunities to get new information after electrification. The answer, “quite much more information”, accounts for 73.5% and the answer, “much more”, accounts for 26.5%. They get the information mainly from television or radio. Young families of 20s or 30s get most of their information from television while the elder families of 50s rely on the radio. Generally speaking, however, questionnaire results say that the radio is most important appliance for the families with or without electrification to get information. Nomadic people consider watching TV as a common activity in their daily life after the electrification. The average time of watching TV is around 4 h in summer, while 3 h in winter. The answer to the question about new information and knowledge obtained by TV says that 80% of samples choose “Learning Chinese”. Questionnaire results conclude that Chinese language has prevailed in nomadic area by the introduction of the television, that is, by electrification (See Table 2).

Table 1  Possession rate of home electric appliance (multiple-answer style, total samples: 40) Unit: % Electrification type Age structure Grid WHSWHSOverall Nonelectric electricity 100 W 300 W 20s 30s 40s Lamp   85.0   0.0 100.0 100.0 100.0 100.0 100.0   93.3 TV   85.0   0.0 100.0 100.0 100.0 100.0 100.0   93.3 Radio 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Washing 60.0   0.0 100.0   27.3   83.3 100.0 100.0   66.7 machine Refrigerator 32.5   0.0   63.6   9.1   41.7 100.0   50.0   33.3 Rice cooker 77.5   0.0 100.0   72.7 100.0 100.0 100.0   86.7 Cell phone 85.0   0.0 100.0 100.0 100.0 100.0 100.0   93.3 Computer 10.0   0.0   27.3   0.0   8.3   33.3   33.3   6.7

Over 60s   50.0   50.0 100.0   16.7   0.0   16.7   50.0   0.0

50s   80.0   80.0 100.0   40.0   20.0   80.0   80.0   0.0

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Table 2  Information and knowledge obtained by TV (multiple-answer style, the number of samples: 34)

Item

Unit: families Age structure Overall 20s 30s 40s

50s

Over 60s

Chinese language study Government policy Professional know-how on live-stock raising Health knowledge Information of overseas societies Others

27 13 18 12 21  2

3 2 2 2 1 0

1 0 0 1 0 0

3 1 2 3 3 0

6 2 3 2 5 1

14  8 11  4 12  1

Table 3  Roles of lighting (multiple-answer style, the number of samples: 34) Unit: families Age structure Item Overall 20s 30s 40s 50s Extending study hours 30 3 6 14 6 Facilitating moonlighting such as handiwork 22 1 4 11 5 Extending recreation hours 21 3 6 9 3 Facilitating cares for live-stock delivery 28 3 4 12 7 Others 2 1 0 0 1

Over 60s 1 1 0 2 0

Table 4  Income of the average live-stock farmer [2] Sales of livestock Sales of Kashmir Moonlighting Share in overall household income (1982) 24.2% 73.8% 0.8% Share in overall household income (2007) 20.0% 76.4% 3.4%

3.2 Changes with Residential Lamp All families who answered the questionnaire say that the use of electric lamps is the most useful for improving their nomadic life. Time of using lamp in a day is around 4 h in summer and 3 h in winter. The answer to the question “which is the most important function of the residential lamp?” is shown in Table 3. Since the residential lamp can increase time for studying by 2 or 3 h in the evening, it is considered as an important factor for improving the children’s life. The use of lamp has made it possible for the Nomadic people to help the delivery of the livestock even at night. The birth rate of livestock has increased after electrification. Women have had more time to make dairy products and, therefore, they could purchase more residential lamps (See Table 4).

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Table 5  Consumption of major foods per capita of live-stock farmer in Inner Mongolia [3] Unit: kg 1978 1998 2007 Actual Actual Actual consumption % consumption % consumption Item % Wheat 77.67 44.0 79.08 34.5 81.97 32.9 Rice 21.10 11.9 42.34 18.5 49.06 19.7 Fresh vegetable 41.00 23.2 57.01 24.9 55.35 22.2 Meat 23.84 13.5 36.11 15.8 44.48 17.8 Poultry   0.00   0.0   0.17   0.0   1.21   0.5 Animal fat   2.22   1.3   0.30   0.0   0.24   0.0 Vegetable oil   0.00   0.0   2.61   1.1   2.79   1.1 Egg   0.49   0.2   0.54   0.2   1.13   0.5 Milk and processed 10.40   5.9 11.08   5.0 13.25   5.3 products

3.3 Changes with Rice Cooker and Refrigerator The possession rate of the rice cooker is 77.5% and that of refrigerator is 32.5%. Young families of 20s, 30s are the main users of both rice cooker and refrigerator. Over 80% of the answers indicate that they become able to eat rice in daily life with the rice cooker while 60% think they become able to eat vegetables with the refrigerator. Table 5 shows the ratios of principal food consumption in 1978, 1998 and 2007. It is shown that the food has been diversified since the rice cooker and the refrigerator began to prevail, that is, electrification started.

4 Comparison of the Ethnic Culture of Electrified Area with that of Non-Electrified Area Sense of values about daily life shapes the lifestyle and determines daily activities. The sense of value can be a mixture of changeable one and stable basic one that does not easily change with the effect of environment of life. In this study both senses are investigated through interviews to local people (See Table 6). (a)  From the results of the items from No. 10 to 12, it is considered that the market economy has much influence on “values of money” of the local people. Thus, it is concluded that “values of money” has been easily changed with the electrification. (b)  From the results of the items, No. 7 and 8, the ways of education of the local people has been changing from the experience-based education in grazing life to the modernized education style. It is also the results of the electrification.

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Table 6  Questionnaire on sense of values in daily life [4] Unit: % Question items Q1 Inner Mongolia is the place of residence of Before Mongolian After Q2 Mongolian is nomadic ethnicity Before After Q3 Grazing is the best lifestyle in prairie Before After Q4 Water should be carefully and efficiently Before utilized After Q5 Horses are important friends for Before Mongolians After Q6 Desertification is the penalty handed down Before by God After Q7 Children must help in housework Before After Q8 Children must take care of infant liveBefore stocks After Q9 Children are expected to succeed Before After Q10 Income in the form of money is desired Before After Q11 Shopping is preferred to saving money Before After Q12 If salary is promising, working in cities is Before attractive After

Agree 100.0 100.0 100.0 100.0   83.3   94.1 100.0 100.0 66.7 88.2 66.7 88.2 66.7 58.8 66.7 44.1 50.0 88.2 33.3 94.1 16.7 94.1 0.0 52.9

Neither agree nor disagree   0.0   0.0   0.0   0.0 16.7   5.9   0.0   0.0 33.3   5.9 33.3   3.0 16.7   5.9   0.0   8.8 50.0   5.9 33.3   0.0 16.7   0.0   0.0   0.0

Disagree   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   5.9   0.0   8.8   16.7   35.3   33.3   47.1   0.0   5.9   33.3   5.9   66.7   5.9 100.0   47.1

The use of electric appliances has improved their quality of life and then the number of answers to want their children to succeed the stockbreeding in Erdos. This means that the way of thinking about education has also been changed by the electrification. (c)  From the results of the items, No. 5 and 6, the awe of “animal” and “god” also has changed and diversified a little. However, most of the answers about “animal” and “god” with both of electrification and non-electrification show that the awe of “animal” and “god” has been kept in the nomadic life. (d)  From the results of the items from No. 1 to 4, the sense of value about “the grassland and animals” and about Mongolians’ lives in Inner Mongolia” changes only a little and has been kept in the nomadic life.

5 Conclusion This paper shows the results of the comparative study of the nomadic lifestyles and sense of values about daily life between the electrified and non-electrified families in Erdos. The results show that obvious changes have occurred in some daily

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activities and some sense of value about daily life after the electrification. The comparative study, however, shows also that nature-oriented way of thinking has been kept in nomadic people. Thus, more attention should be paid to taking advantage of the tradition nature-oriented lifestyle in order to expand the renewable energy system in the electrification process.

References 1. GEF and United Nations Development Programme (2009) Renewable energy based chinese un-electrified region electrification 25:29 2. National Bureau of Statistics of Erdos, China (2008) Erdos statistical yearbook. China Statistics, Beijing 3. National Bureau of Statistics in Inner Mongolian, China (2008) Inner Mongolian statistical yearbook. China Statistics, Beijing 4. Gao L, Taoketao (2007) Grassland culture and modern civilization. Inner Mongolia Education Press, pp 43–70

Part II

Renewable Energy Research and CO2 Reduction Research

The Potential of Biodiesel with Improved Properties to an Alternative Energy Mix Gerhard Knothe

Abstract  Fuels derived from renewable biological sources (biomass) are prominent among the sustainable energy sources. Biodiesel, the mono-alkyl esters of vegetable oils or animal fats, is one of the significant biomass-derived fuels. It is obtained from vegetable oils or other triacylglycerol feedstocks by transesterification with an alcohol giving glycerol as co-product. While biodiesel is technically competitive with petrodiesel fuel, problems that have beset biodiesel include poor cold flow and oxidative stability. These problems are to a great extent due to most biodiesel fuels containing mainly the same five C16 and C18 fatty acid esters. Five methods, including fatty acid profile modifications, exist for overcoming these problems. Properties of neat esters show that enriching acids such as decanoic or palmitoleic acids in feedstocks may improve biodiesel properties. The alcohol also plays a role with esters other than methyl imparting more favorable properties to biodiesel. The technical problems of biodiesel also afflict feedstocks, perhaps more severely, with claimed high production potential. Thus, algae-based biodiesel fuels would likely possess worse cold flow and oxidative stability than most vegetable oil-based biodiesel. Hydrodeoxygenation of vegetable oil feedstocks yields renewable diesel, whose composition thus resembles petrodiesel. Properties, including mass and energy balance of biodiesel and renewable diesel are compared as are potential uses. Biodiesel has a favorable balance compared to other biomass-derived fuels, also when including co-products. For fuels such as biodiesel and others to be more competitive, fuel properties as well as economics and production potential need to be improved. Keywords  Biodiesel • Energy balance • Feedstocks • Fuel properties • Renewable diesel example

G. Knothe (*) U.S. Department of Agriculture, National Center for Agricultural Utilization Research, Peoria, IL 61604, USA e-mail: [email protected]

T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_9, © Springer 2011

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1 Introduction Continuing and increasing world-wide concerns regarding the availability of petroleum and other “conventional” sources of energy have sparked the search for sustainable sources of energy. Liquid fuels obtained from biological sources (biomass) such have found considerable in this connection and several have been commercialized. Biodiesel [1, 2], defined as the mono-alkyl esters of vegetable oils or animal fats or other triacylglycerol feedstocks, is among these fuels. Standards have been developed for biodiesel, notably the American standard ASTM D6751 [3] and the European standard EN 14214 [4]. This fuel is technically competitive with conventional petroleum-derived diesel fuel (petrodiesel). Advantages of biodiesel include domestic origin, renewability of most carbon atoms, compatibility with the existing fuel distribution infrastructure, reduction of most regulated exhaust emissions, low or no sulfur and aromatics content, biodegradability, safer handling due to high flash point, inherent lubricity, and a positive energy balance (>4:1). Problems associated with biodiesel include oxidative stability due to its content of unsaturated fatty acid chains, poor cold flow and a slight increase of nitrogen oxides (NOx) exhaust emissions in many emissions tests, although this problem may fade with time as increasing market penetration of new exhaust emissions technologies alleviates this effect. Therefore, the issue of improving biodiesel fuel properties, especially oxidative stability and cold flow is of great significance. Specific fatty acids, especially decanoic or palmitoleic acids, may be targets for enrichment in triacylglycerol feedstocks in order to improve biodiesel properties [5, 6]. Overall, five approaches to these problems exist [6]. Renewable diesel [7, 8] is another fuel that can be obtained from triacylglycerolbased feedstocks, albeit through a different process, namely hydrodeoxygenation instead of transesterification as in the case of biodiesel. This fuel more closely resembles the composition of petrodiesel as alkane-type hydrocarbons are its primary constituents. Thus its properties also more closely resemble that of petrodiesel of the (ultra-)low sulfur type. Both biodiesel and renewable diesel are thus prime examples of liquid fuels derived from biological sources and contribute to the mix of alternative energy sources that now exit. This article briefly discusses, with an emphasis on biodiesel, this contribution.

2 Discussion 2.1 Overview of Biodiesel Properties The major components of biodiesel are the esters of fatty acids, usually methyl esters, as methanol is the most common alcohol used to prepare biodiesel. The most common fatty acid methyl esters found in biodiesel are methyl palmitate (hexadecanoate;

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C16:0), methyl stearate (octadecanoate; C18:0), methyl oleate (octadecenoate; C18:1 D9), methyl linoleate (octadecadienoate; C18:2 D9, D12) and methyl linolenate (octadecatrienoate; C18:3 D9, D12, D15). The unbranched long-chain nature of fatty esters is the reason why biodiesel can be used in a diesel engine. They resemble the long-chain hydrocarbons, i.e. alkanes, that “ideally” constitute petrodiesel. For example, hexadecane is the high-quality reference compound on the cetane scale (cetane number = 100) used for diesel fuel ignition quality. Especially the saturated fatty acid methyl (or other) esters C16:0 and C18:0 have high cetane numbers comparable to those of hexadecane or other long-chain alkanes. Cetane number decreases with increasing unsaturation and decreasing chain length [9]. Thus the cetane number of methyl oleate is around 55–58, that of methyl linoleate around 40–42 and that of methyl linolenate around 25 [10]. Minimum cetane numbers prescribed in biodiesel standards are 47 in the American biodiesel standard ASTM D6751 [3] and 51 in the European biodiesel standard EN 14214 [4]. The low temperature properties of biodiesel are affected by compound structure in a similar fashion. The melting points of fatty esters increase with increasing chain length and increasing saturation. The melting point of methyl stearate is 37.7°C, that of methyl palmitate 28.5°C, that of methyl oleate −20°C, methyl linoleate −43°C and methyl linolenate around −45°C [11]. The high melting points of the saturated esters affect the cloud point, the temperature at which the first solids form when cooling a fuel, and pour point, the temperature at which the fuel no longer flows, of biodiesel. For example, the cloud point of methyl soyate, which contains about 10–11% C16:0 methyl ester and 4–5% C18:0 methyl ester is around 0°C [12]. The cloud point of biodiesel from a feedstock containing even greater amounts of saturated esters, for example methyl esters of palm oil (>40% C16:0 methyl esters) is considerable higher. The cloud and pour point are affected by the amount and nature of the saturated esters with the nature of the lower-melting unsaturated esters not playing a role [13]. Minor constituents of biodiesel such as monoacylglycerols [14] (from the production process) and sterol glucosides [15] also affect cold flow. Similarly, oxidative stability, i.e., the tendency to react with oxygen in air, is also affected by compound structure. The saturated fatty esters are oxidatively stable. Increasing unsaturation leads to decreasing oxidative stability. Relative reaction rates of oxidation when assigning methyl oleate a relative rate of 1 are 41 for methyl linoleate and 98 for methyl linolenate [16]. Thus the C18:2 and C18:3 esters are oxidatively very unstable. The so-called Rancimat test is prescribed in biodiesel standards to assess oxidative stability. The minimum induction time using this test is 3 h in the ATSM D6751 and 6 h in EN 14214. However, even methyl oleate in the neat form does not meet the 3 h requirement [4]. This means that antioxidant additives will always be necessary to meet the oxidative stability requirements in biodiesel standards. Kinematic viscosity is another fuel property affected by the fatty ester components. This property increases with increasing chain length and increasing saturation [17]. However, most biodiesel fuels meet the viscosity ranges prescribed in biodiesel standards which are 1.9–6.0 mm2/s in ASTM D6751 and 3.5–5.0 mm2/s in EN 14214.

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Decreasing kinematic viscosity is the major reason for the production of biodiesel from triacylglycerol feedstocks as the high viscosity of vegetable oils leads to engine deposits and other problems when using them as fuels. Other important properties and performance issues not addressed in biodiesel standards are lubricity and exhaust emissions, the latter being dealt with by a variety of regulations. For sake of brevity they are not discussed here.

2.2 Improvement of Biodiesel Properties The brief discussion above shows that the task of improving biodiesel properties faces difficult obstacles. Improving cold flow by reducing saturated fatty esters reduces oxidative stability, improving oxidative stability by reducing unsaturated fatty esters worsens the cold flow behavior. Cetane number (and emissions) is affected negatively by reducing the amount of saturated esters. Five methods have been identified for improving the fuel properties of biodiesel [6]. These are: (a) the use of additives, (b) producing esters other than methyl, (c) changing the fatty acid profile through physical procedures, (d) the use of feedstocks with an inherently different fatty acid profile (e) or modifying the fatty acid profile of existing feedstocks through, say, genetic modification. The use of additives is straightforward. Issues to consider are additive compatibility if additives serving different purpose are used, influence of additives on other properties (for an example, See [18]), additive cost and the observation that many additives may not be as effective as claimed. Esters other than methyl appear to have advantageous properties. For example, ethyl esters generally have lower melting points than methyl esters [11] while not affecting oxidative stability or cetane number [10]. Branched esters such as isopropyl esters have been shown to possess lower crystallization temperatures (for example, isopropyl soyate crystallized at temperatures 7–11°C lower than methyl soyate, See [19]) while again not affecting oxidative stability or cetane number. The major disadvantage to this approach is that alcohols other than methanol are usually considerably more expensive and that changes to the transesterification reaction yielding biodiesel may be necessary. Physical procedures for modifying the fatty acid profile are based on winterization, i.e., repetitive application of cooling cycles with removal of higher melting components [20]. The effect on the fatty acid profile is to enrich the lower-melting polyunsaturated fatty acid chains. While this procedure improves the low-temperature properties, oxidative stability and cetane number are lowered. An interesting issue is to define biodiesel components that exhibit lower melting points and acceptable oxidative stability simultaneously while not comprising properties such as cetane number and kinematic viscosity. It has been discussed that palmitoleic acid (9(Z)-hexadecenoic acid; C16:1) and, when considering saturated chains, decanoic acid, are candidates fatty acid for enrichment in the fatty acid

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profiles of vegetable oils. The prime advantage is that their methyl esters possess lower melting points (approximately −34°C for methyl palmitoleate and −13°C for methyl decanoate [11]) while offering acceptable cetane numbers (51 to 56 for methyl palmitoleate and 51.6 for methyl decanoate [5]) and oxidative stability, although in the case of methyl palmitoleate no advantage over methyl oleate exists in this respect. Indeed, methyl esters produced from an oil, cuphea oil, enriched in decanoic acid (approximately 65%) showed improved cold flow properties (cloud point −9 to −10°C) with a cetane number around 55−56 and oxidative stability per Rancimat of approximately 3−3.5 h [21]. On the other hand, an oil moderately enriched in palmitoleic acid (15−20%) did not lead to a biodiesel fuel with improved properties, likely due to the presence of small amounts of highmelting esters of C20 and C22 saturated fatty acids [22]. It may be noted that the potential exhaust emissions of biodiesel from such oils were extrapolated from other studies [23, 24] and no disadvantages are likely, rather, exhaust emissions are likely more favorable than in the case of biodiesel fuels with more conventional fatty acid profiles. Oils obtained from algae have been finding increasing attention as potential biodiesel feedstocks (for example, See [25]), although critical voices have also been raised (for example, See [26]). The composition of numerous algal oils as compiled in some literature [27], however, raises concern that properties of biodiesel from these feedstocks may possess poor cold flow and oxidative stability simultaneously as may such oils exhibit high amounts of saturated and polyunsaturated fatty acids. It may be noted that biodiesel derived from other, inedible oils such as jatropha [28] does not offer any advantages in terms of fuel properties as many of these oils consist of the same C16 and C18 fatty acid as the conventional commodity oils. Feedstocks consisting largely of materials other than triacylglycerols may also pose a potential source of biodiesel [29–32]. The conversion (by microbiological procedures) to fatty acids may be tailored to enrich the fatty acid profile in acids with advantageous properties.

2.3 Renewable Diesel As mentioned above, petrodiesel ideally consists of long-chain unbranched hydrocarbons, i.e. alkanes. Recently, procedures to produce such compounds from triacylglycerol feedstocks have found attention [7, 8]. The resulting product is best termed renewable diesel [8]. It has been stated that the procedure can be tailored to yield renewable diesel with different properties to, for example, with different cold flow properties. Thus this process is of interest for turbine ( jet) fuels as they are used for aviation purposes. Renewable diesel, its composition simulating petrodiesel, therefore has properties similar to petrodiesel.

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2.4 Comparison of Biodiesel and Renewable Diesel Regarding fuel properties, the observations made above for biodiesel vs. petrodiesel largely hold for the comparison of biodiesel vs. renewable diesel due to the similarity of the latter with petrodiesel. The processes used to prepare biodiesel and renewable diesel vary considerably. This also leads to varying mass balances. This is illustrated in Fig. 1 using neat triolein, the triacylglycerol of oleic acid, as feedstock. When using triolein as feedstock, methyl oleate is the product of transesterification and heptadecane is the product of hydrodeoxygenation. Glycerol is the co-product of biodiesel production and propane a co-product of renewable diesel production. As both CO2 and propane are liberated during renewable diesel production, while during biodiesel production the glycerol ester moiety is “replaced” by the methyl ester moiety from methanol, the mass balance of renewable biodiesel production is lower than that of biodiesel. However, some of the energy used to produce renewable diesel is stored in the hydrocarbon product, leading to a higher energy content of the renewable diesel on a molar basis. The production of biodiesel from the triacylglycerol feedstock and alcohol generally is conducted at 60–65°C for 1  h at ambient pressure with a catalyst such as sodium methoxide while renewable diesel production requires more drastic conditions such as elevated temperature (around 300°C) and pressure in the presence of hydrogen and a catalyst (typically sulfided NiMo/g-Al2O3 or CoMo/g-Al2O3). The more unsaturated the feedstock, the greater the hydrogen requirement is for producing renewable diesel. While the energy balance of overall biodiesel production is known to be positive, that of renewable diesel production has not been definitively established, but is likely less favorable due to the more severe conditions required for its production. Another issue to consider in this connection is that glycerol, a common commodity compound, is obtained “free” when producing biodiesel, eliminating the petrochemical route using propene as starting material. Otherwise, when using the same feedstocks, the other factors influencing the energy balance are the same. Biodiesel - Methyl oleate from triolein: C57H104O6 + 3 CH3OH MW 885.453

3 C19H36O2 + C3H8O3 3 x 296.495 = 889.458 = 100.5% mass app. 40000 kJ/kg = 39547 kJ/L

Renewable Diesel - Heptadecane from triolein: C57H104O6 + 6 H2 MW 885.453

3 C17 H36 + 3 CO2 + C3H8 3 x 240.475= 721.425= 81.5% mass app. 47500 kJ/kg = 41310 kJ/L

Fig. 1  Production and mass balance of biodiesel and renewable diesel production as shown for triolein

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Thus, a possibility seems to be to use biodiesel and renewable in the applications where each offers the most benefits. For biodiesel these would be ground applications taking advantage of its better environmental properties and safer handling while for renewable diesel this would be aviation applications due to the possibility of producing a fuel with improved cold flow properties.

3 Outlook Developing alternative fuels for liquid fuels to power compression-ignition engines, including turbine (jet) engines, as well as burners and heaters is essential in light of the problems associated with dwindling petroleum reserves. Both biodiesel and renewable diesel are interesting alternatives, each with its one advantageous applications. Both fuels, and other biomass-derived fuels not discussed here, are affected by the issue of feedstock availability and supply. In the case of biodiesel, in order to enhance its contribution to an alternative energy mix, improvement of fuel properties, especially cold flow and oxidative stability is important. Modifying the fatty acid profile of the feedstocks to give inherently better properties is a long-term but promising approach to achieving this goal.

References 1. Knothe G, Van Gerpen J, Krahl J (eds) (2010) The biodiesel handbook, 2nd edn. AOCS Press, Urbana, IL 2. Mittelbach M, Remschmidt C (2004) Biodiesel – the comprehensive handbook. M Mittelbach, Graz 3. American Society for Testing and Materials (ASTM) (2009) Standard specification for biodiesel fuel blend stock (B100) for middle distillate fuels. ASTM, West Conshohocken, PA 4. European Committee for Standardization (CEN) (2008) Automotive fuels – fatty acid methyl esters (FAME) for diesel engines. Requirements and test methods. CEN, Brussels, Belgium 5. Knothe G (2008) “Designer” biodiesel: optimizing fatty ester composition to improve fuel properties. Energy Fuels 22:1358–1364 6. Knothe G (2009) Improving biodiesel fuel properties by modifying fatty ester composition. Energy Environ Sci 2:759–766 7. Huber GW, Corma A (2007) Synergies between bio- and oil refineries for the production of fuels from biomass. Angew Chem Int Ed 46(38):7184–7201 8. Knothe G (2010) Biodiesel and renewable diesel: a comparison. Prog Energy Combustion Sci 36:364–373 9. Harrington KJ (1986) Chemical and physical properties of vegetable oil esters and their effect on diesel fuel performance. Biomass 9:1–17 10. Knothe G, AC Matheaus, Ryan TW III (2003) Cetane numbers of branched and straight-chain fatty esters determined in an ignition quality tester. Fuel 82:971–975 11. Knothe G, Dunn RO (2009) A comprehensive evaluation of the melting points of fatty acids and esters determined by differential scanning calorimetry. J Am Oil Chem Soc 86:843–856

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12. Dunn RO, Bagby MO (1995) Low-temperature properties of triglyceride-based diesel fuels: transesterified methyl ester and petroleum middle distillate/ester blends. J Am Oil Chem Soc 72:895–904 13. Imahara H, Minami E, Saka S (2006) Thermodynamic study on cloud point of biodiesel with its fatty acid omposition. Fuel 85(12–13):1666–1670 14. Yu L, Lee I, Hammond EG, Johnson LA, Van Gerpen JH (1998) The influence of trace components on the melting point of methyl soyate. J Am Oil Chem Soc 75:1821–1824 15. Moreau RA, Scott KM, Haas MJ (2008) The identification of steryl glucosides in precipitates from commercial biodiesel. J Am Oil Chem Soc 85:761–770 16. Frankel EN (2005) Lipid oxidation, 2nd edn. The Oily Press, PJ Barnes and Associates, Bridgwater 17. Knothe G, Steidley KR (2005) Kinematic viscosity of biodiesel fuel components and related compounds. Influence of compound structure and comparison to petrodiesel fuel components. Fuel 84:1059–1065 18. Schober S, Mittelbach M (2005) Influence of diesel particulate filter additives on biodiesel quality. Eur J Lipid Sci Technol 107(4):268–271 19. Lee I, Johnson LA, Hammond EG (1995) Use of branched-chain esters to reduce the crystallization temperature of biodiesel. J Am Oil Chem Soc 72:1155–1160 20. Dunn RO, Shockley MW, Bagby MO (1997) Winterized methyl esters from soybean oil: an alternative diesel fuel with improved low-temperature flow properties. SAE (Society of Automotive Engineers) Technical Paper Series 971682 21. Knothe G, Cermak SC, Evangelista RL (2009) Cuphea oil as source of biodiesel with improved fuel properties caused by high content of methyl decanoate. Energy Fuels 23:1743–1747 22. Knothe G (2010) Biodiesel derived from a model oil enriched in palmitoleic acid, macadamia nut oil. Energy Fuels 24:2098–2103 23. McCormick RL, Graboski MS, Alleman TL, Herring AM (2001) Impact of biodiesel source material and chemical structure on emissions of criteria pollutants from a heavy-duty engine. Environ Sci Technol 35:1742–1747 24. Knothe G, Sharp CA, Ryan TW III (2006) Exhaust emissions of biodiesel, petrodiesel, neat methyl esters, and alkanes in a new technology engine. Energy Fuels 20:403–408 25. Chisti Y (2007) Biodiesel from microalgae. Biotechnol Adv 25(3):294–306 26. van Beilen JB (2010) Why microalgal biofuels won’t save the internal combustion machine. Biofpr 91:41–52 27. Hu Q, Sommerfeld M, Jarvis E, Ghirardi M, Posewitz M, Seibert M, Darzins A (2008) Microalgal triacylglycerols as feedstocks for biofuel production: perspectives and advances. Plant J 54(4):621–639 28. Foidl N, Foidl G, Sanchez M, Mittelbach M, Hackel S (1996) Jatropha curcas L. as a source for the production of biofuel in Nicaragua. Bioresour Technol 58:77–82 29. Kalscheuer R, Stölting T, Steinbüchel A (2006) Microdiesel: Escherichia coli engineered for fuel production. Microbiology 152:2529–2536 30. Keasling JD, Hu Z, Somerville C, Church G, Berry D, Friedman L, Schirmer A, Brubaker S, del Cardayré SB (2007) Production of fatty acids and derivatives thereof, WO/2007/136762, November 29, 2007. http://www.wipo.int/pctdb/en/wo.jsp?WO = 2007136762 31. Wackett LP (2008) Biomass to fuels via microbial transformations. Curr Opin Chem Biol 12:187–193 32. Stöveken T, Steinbüchel A (2008) Bacterial acyltransferases as an alternative for lipase-catalyzed acylation for the production of oleochemicals and fuels. Angew Chem Int Ed 47:3688–3694

Net Energy Calculations for Production of Biodiesel and Biogas from Haematococcus pluvialis and Nannochloropsis sp. Luis F. Razon

Abstract  Microalgae have been proposed as possible alternative feedstock for the production of biodiesel because of their high photosynthetic efficiency. However, the high energy input required for microalgal culture and oil extraction may negate this advantage. There is a need to determine whether microalgal biodiesel can deliver more energy than is required to produce it. Using the Cumulative Energy Demand method in Simapro®, net energy calculations were done on systems to produce biodiesel and biogas from two microalgae species: Haematococcus pluvialis and Nannochloropsis sp. In spite of very optimistic assumptions, the results show a large energy deficit for both systems. Largest contributions came from the energy required to culture the microalgae and the energy required to either dry the microalgae or to disrupt the cell wall. Recommendations are made to develop wet extraction and transesterification technology to make microalgal biodiesel systems viable from an energy standpoint. Keywords  Biodiesel • Energy balance • Haematococcus pluvialis • Microalgae • Nannochloropsis

1 Introduction Biodiesel, the accepted name for fatty acid methyl esters derived from the oils of living things, has emerged as an immediately available, environmentally friendly alternative to petroleum-derived diesel fuel. However, some simple calculations would show that even if all of the vegetable oil in the world were converted to

L.F. Razon (*) Department of Chemical Engineering, De La Salle University, 2401 Taft Avenue, Manila, Philippines e-mail: [email protected]

T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_10, © Springer 2011

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biodiesel, the resulting production would fill only 18% of transport diesel fuel demand [1]. Hence, there is a need to develop alternative sources for biodiesel feedstock. Microalgae have a higher photosynthetic efficiency than terrestrial plants and would need less land to fill demand [2]. On the other hand, harvest and conversion of the algal oils to biodiesel is more complicated and expensive since the algal culture has inherently greater water removal requirements since the algal biomass concentration is only in the order of g L−1. While the microalgae are photosynthetic, algal culturing systems like photobioreactors and raceway ponds continuously use energy for agitation and supply of carbon dioxide. Because of this, Reijnders [3] suggested that energy gain from using photosynthetic microalgae for biodiesel might be less than energy demand. This was refuted by Chisti [4], however. In this study, we apply the Cumulative Energy Demand method from Simapro® 7.2.2 for two scenarios for obtaining biodiesel and biogas from microalgae. The data for key inputs like electricity and chemicals were obtained from the ecoinvent® database. Previous studies have made similar but not identical analyses [5–10].

2 Haematococcus pluvialis Haematococcus pluvialis is a fresh-water, photosynthetic microalga that has been mentioned as a potential source of lipids for conversion into biodiesel [11] or for CO2 sequestration [12]. Figure 1 shows the proposed process flow diagram.

Fig. 1  Process flow diagram for the production of methyl esters and biogas from H. pluvialis

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To control alien species, a photobioreactor is used to periodically feed an axenic slurry into the raceway pond [12]. A flat-plate photobioreactor consumes 50–70 W m−3 [13]. The hydraulic power requirement for the raceway pond is estimated using the following equation [14]:

P=

r QD d 102e

(1)

where P = power (kW), Q = the quantity of water in motion (m3 s−1), r = the specific weight of water (kg m−3), e = the efficiency of the paddle wheel and Dd is the head loss in m. For a channel with a rectangular cross-section, Q = w • v • d where w = width, d = depth and v is the velocity of the water. In this paper, the dimensions of the pond in [12] are used: w = 5.5 m and d = 0.12 m. Typical values for the water velocity, efficiency and head loss are v = 0.25 m s−1, e = 0.17 and Dd = 0.06 m, respectively [14]. These numbers result in a power estimate of 0.57  kW which is rounded up to 0.60 kW. For biomass productivity, the highest observed biomass concentration was 432 g m−3 and a fat content of 25% [12] were used. CO2 and nitrogen requirements were estimated using an elemental composition of H. pluvialis reported in [15]: 45.6% C, 8.2% H, 6% N, 0.58% S, 39.6% O (assumed, by balance). Nitrogen requirements are to be supplied by potassium nitrate. Phosphorus requirements from single superphosphate are estimated with the Redfield N:P ratio of 16 [16]. Energy for pumping CO2 into the pond was estimated by assuming 80% absorption of the CO2 into the water and a compressor head and efficiency of 58 cm and 30%, respectively. Electricity is provided by a nearby natural-gas fired combined heat and power (CHP) plant and the allocations are distributed according to the energy content of the heat and electricity. This source of electricity is used for all electrical power. The algal slurry from the pond is concentrated by via two stages: gravitational settling and microfiltration. The gravitational settling is accomplished without the use of flocculants because of the large size of H. pluvialis (19–29 um) [17]. Power requirements for thickeners are negligible [18]. The algal concentration in the underflow and the overflow are assumed to be ten times the original concentration and 0.2 times the original concentration respectively. The overflow is used as a feed to the biogas process. The power requirements to concentrate an algal slurry using a cross-flow microfilter by a factor of 48 is about 1.37 MJ m−3 [19]. The retentate is fed into a cracking bead mill to release the oil from H. pluvialis cysts [20, 21]. The bead mill requires 10.15  MJ • (kg dry weight)−1 [22]. Eighty percent recovery of oil in biomass was assumed. The cracked slurry is fed into a decanter, which is assumed to consume a negligibly small amount of power and recovers 80% of the oil. Process inputs for transesterification are taken to be similar to soybean biodiesel [23]. The theoretical biogas yield from the thickener overflow and the depleted algal slurry was computed using the elemental composition in [15] and the following equation [24]:

a b   n a b  n a b C n H a Ob +  n − −  H 2 O →  + −  CH 4 +  − +  CO2   2 8 4  2 8 4 4 2

(2)

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Sixty percent conversion was assumed, which is indicated in [24] as a reasonable assumption for more particulate substrates. Elemental nitrogen is also assumed to be 60% converted to ammonia compounds which can be recovered in a biofilter and used to augment pond fertilizer. Allocations are done on a dry solids basis and are indicated in Fig.  1. Three displacements were done: (1) filtrate from the microfilter displaces fresh water; (2) glycerin from transesterification displaces glycerin from palm oil and (3) the ammonium compounds from biogas displaces NH4NO3. Net energy calculations show that 1 kg of methyl esters from H. pluvialis oil, accompanied by 2.6  m3 of biogas at standard temperature and pressure (STP), requires 222 MJ of primary energy input (4 MJ for methyl esters and 218 MJ for the biogas). Since the energy derived from the biodiesel and the corresponding biogas are 37 and 51 MJ, respectively, the total energy output from the process is 88 MJ. There is an energy deficit. This conclusion is obtained despite optimistic assumptions throughout the analysis. The direct process contributions to produce the biodiesel and the biogas are summarized in Table 1. The three largest contributors are: (1) the electricity for the bead mill (70 MJ, 32%); (2) the electricity required for the photobioreactor (57 MJ, 26%) and (3) fertilizer (39 MJ, 18%). Another possible tactic for a more favorable energy balance is to recycle the thickener overflow to the raceway pond, thus minimizing or eliminating the need for the initial photobioreactor. Both of these alternatives (wastewater and thickener overflow) are insufficient however to eliminate the energy deficit.

3  Nannochloropsis sp. Other microalgae that have been proposed as feedstock for biodiesel are those of the genus Nannochloropsis because of their high oil content and high biomass productivity [7]. The genus grows in salt water. While this means that specialized pumps and fittings need to be used because of the higher corrosivity of the salt water, this may be an advantage because fresh water use will be minimized. Figure 2 shows the proposed process. The dimensions and energy requirements of the raceway pond are assumed to be the same as the pond for H. pluvialis. Biomass yield is computed from an areal productivity of 16 g (dry weight) · m−2 d−1 [25] and a cell concentration of 0.35 g (dry weight) · L−1 [26]. The proximate composition is taken as: protein = 30.1%, fat = 30.2%, carbohydrate = 9.7%, moisture = 3.1% and ash = 26.9% [27, 28]. Elemental composition is taken from the empirical formula of carbohydrates, protein and fat which are C6H10O5, C5H7NO2 and C57H104O6 respectively [24]. From these data, oil yield, CO2 and fertilizer requirements are computed. Power requirements for CO2 injection and pond agitation are computed in a manner similar to that of the H. pluvialis case. Control of other species is achieved by chlorination with 4  ppm of sodium hypochlorite [25]. Electricity for the energy needs are provided by a natural-gas fired CHP plant with the energy burden allocated according to the amount of energy

Net Energy Calculations for Production of Biodiesel and Biogas Table 1  Direct process contributions to of biogas at STP from H. pluvialis Process Photobioreactor KNO3 P2O5 Electricity Raceway pond KNO3 P2O5 Electricity Microfilter Allocation for thickener underflow Electricity from CHP plant Credit for “fresh” water Bead mill Electricity Transesterification Allocation for oil Methanol NaOH NaOCH3 Electricity from CHP plant Heat from CHP plant Credit for glycerin Total for methyl esters Biogas generation Allocation for depleted algal cake Allocation for thickener overflow Electricity from CHP plant Treatment (sewage) Credit for ammonium compounds Total for biogas

87

produce 1 kg of methyl esters and 2.6 m3 Amount

Energy equivalent (MJ)

0.032 kg 0.018 kg

2.9 0.9 57

0.34 kg 0.10 kg

30 4.7 27

1,200 kg

100 2.2 −6.0

−1,100 kg

70

0.2 kg 0.002 kg 0.01 kg

−0.2 kg

28 kg 13,000 kg 13 m3 −0.013 kg

5.7 15 0.2 1.3 0.1 2.8 −21 4.0 160 22 3.3 33 −0.7 218

provided as electricity and heat. The algal slurry is concentrated using a gravity thickener to recover 90% of the biomass. Al2(SO4)3 flocculant is necessary because of the small size of Nannochloropsis (2–4 um) [7]. The thickened slurry is dried to a cake (90% solids) using a sewage sludge belt drier, which consumes 3.35 MJ kg−1 of evaporated water [29]. The oils are extracted at 96% efficiency by leaching with hexane and transesterified using processes similar to soybean [23]. Biogas conversion of the depleted algal cake is assumed to proceed in the same manner as the one for H. pluvialis. The same allocation and displacement practices as that for the H. pluvialis case are adopted. Energy demand calculations for the process show that the primary energy input to produce 1 kg of methyl esters from algal oil and 1.5 m3 of biogas at standard temperature and pressure is 290  MJ, which is allocated as 66 MJ for the methyl

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Fig.  2  Process flow diagram for the production of methyl esters and biogas from Nannochloropsis

esters and 224 MJ for the biogas. The net energy output that may be expected from the 1 kg of methyl esters and the corresponding 1.5 m3 of biogas at STP are 37 and 25 MJ respectively. A net energy deficit again results. The direct process contributions to produce the biodiesel and the biogas are summarized in Table 2. The largest contributors to the energy usage are: (1) heat from the CHP plant for the dryer (120 MJ, 42%) and (2) sewage treatment for the biogas residue (72 MJ, 25%).

4 Conclusions Neither of the systems would be practicable as purely energy generation systems; i.e., systems to take advantage of photosynthesis to produce more energy. Detailed full-chain energy analysis of methyl esters from jatropha [30] and palm oil [31] showed very favorable energy balances. The results from this paper do not the possibility that these systems would be desirable from a GHG-reduction viewpoint as concluded by Campbell et al. [6]. It is also possible that the energy products may be considered as by-products for more valuable products, as is the case for astaxanthin from H. pluvialis [12]. For the reasons discussed in the Introduction, fuel from algal biomass may still be the most viable long term source of renewable fuel. However, Zemke et  al. [32] states that the theoretical thermodynamic limit of microalgal lipid production is only 14.5  kg m−2 a−1. In this study, the microalgal production rates used correspond to 13.3 kg m−2 a−1 for H. pluvialis and 5.8 kg m−2 a−1 for Nannochloropsis. It seems that very little improvement can be expected in this direction. Perhaps, the search for species to cultivate can de directed towards finding species that have thin cell walls and require minimal energy for disruption. Postharvest dewatering technology must be improved or perhaps eliminated altogether. A direct transesterification of fungal lipids using acid catalysts has been reported recently [33]. Such approaches would most likely be the ones to help microalgal biodiesel become viable.

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Table 2  Direct process contributions to produce 1 kg of methyl esters and 1.5 m3 of biogas at STP from Nannochloropsis Process Amount Energy equivalent (MJ) Raceway pond KNO3 0.05 kg 5.9 P2O5 0.04 kg 1.8 NaOCl 0.09 kg 1.6 Electricity 15 Thickener Al2(SO4)3 1.5 kg 13.9 HCl (15%) nil nil Algal biomass dryer Allocation for underflow 30 kg 35 Heat from CHP plant 120 Oil extraction Hexane 2.7 g 0.2 Electricity from CHP plant 20 Transesterification Allocation for oil 1 kg 67 Methanol 0.2 kg 15 NaOH 0.02 kg 0.2 NaOCH 3 0.01 kg 1.3 Electricity from CHP plant 0.5 Heat from CHP plant 2.8 Credit for glycerin −0.2 kg −20.9 Total for methyl esters 66.0 Biogas generation Allocation for depleted algal cake Allocation for thickener overflow Electricity from CHP plant Treatment (sewage) Credit for ammonium compounds Total for biogas

2.8 kg 10,600 kg 29 m 3 −0.2 kg

157 3.9 1.9 72 −11 224.0

Acknowledgements  The advice and assistance of Dr Raymond Tan, Dr John Benneman and Mr. Long The Nam Doan is gratefully acknowledged. The University Research Coordination Office and College of Engineering of De La Salle University are thanked for the grant of a sabbatical leave. Lastly, the grant of a free license for Simapro® by Pre’ Consultants bv is most highly appreciated.

References 1. Razon L (2009) Alternative crops for biodiesel feedstock. CAB Rev Perspect Agric Vet Sci Nutr Nat Resour 4:056 2. Schenk PM, Thomas-Hall SR, Stephens E, Marx UC, Mussgnug JH, Posten C, Kruse O et al (2008) Second generation biofuels: high-efficiency microalgae for biodiesel production. Bioenergy Res 1:20–43

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3. Reijnders L (2008) Do biofuels from microalgae beat biofuels from terrestrial plants? Trends Biotechnol 26:349–350 4. Chisti Y (2008) Response to Reijnders: do biofuels from microalgae beat biofuels from terrestrial plants? Trends Biotechnol 26:341–352 5. Kadam K (2002) Environmental implications of power generation via coal microalgae cofiring. Energy 27:905–922 6. Campbell PK, Beer T, Batten D (2011) Life cycle assessment of biodiesel production from microalgae in ponds. Bioresour Technol 102:50–56 7. Jorquera O, Kiperstok A, Sales EA, Embiruçu M, Ghirardi ML (2010) Comparative energy life-cycle analyses of microalgal biomass production in open ponds and photobioreactors. Bioresour Technol 101:1406–1413 8. Clarens AF, Resureccion EP, White MA, Colosi LM (2010) Environmental life cycle comparison of algae to other bioenergy feedstocks. Environ Sci Technol 44:1813–1819 9. Lardon L, Helias A, Sialve B, Steyer J-P, Bernard O (2009) Life-cycle assessment of biodiesel production from microalgae. Environ Sci Technol 43:6475–6481 10. Sander K, Murthy GS (2010) Life cycle analysis of algae biodiesel. Int J Life Cycle Assess 15:704–714 11. Damiani MC, Popovich CA, Constenla D, Leonardi PI (2010) Lipid analysis in Haematococcus pluvialis to assess its potential use as a biodiesel feedstock. Bioresour Technol 101:3801–3807 12. Huntley ME, Redalje DG (2007) CO2 mitigation and renewable oil from photosynthetic microbes: a new appraisal. Mitig Adapt Strateg Glob Change 12:573–608 13. Lehr F, Posten C (2009) Closed photo-bioreactors as tools for biofuel production. Curr Opin Biotechnol 20:280–285 14. Borowitzka M (2005) Chapter 14: Culturing microalgae in outdoor ponds. In: Andersen RA (ed) Algal culturing techniques. Elsevier Academic, San Diego, CA, pp 205–217 15. García-Malea MC, Acién FG, Fernández JM, Cerón MC, Molina E (2006) Continuous production of green cells of Haematococcus pluvialis: modeling of the irradiance effect. Enzyme Microb Technol 38:981–989 16. Geider RJ, La Roche J (2002) Redfield revisited: variability of C:N:P in marine microalgae and its biochemical basis. Eur J Phycol 37:1–17 17. López MCG, Sánchez EDR, Casas López JL, Fernández FGA, Sevilla JMF, Rivas J et  al (2006) Comparative analysis of the outdoor culture of Haematococcus pluvialis in tubular and bubble column photobioreactors. J Biotechnol 123:329–342 18. Genck WJ, Dickey DS, Baczek FA, Bedell DC, Brown K, Chen W et al (2008) Liquid–solid operations and equipment. In: Perry’s chemical engineers handbook, 8th edn. 19. Danquah MK, Gladman B, Moheimani N, Forde GM (2009) Microalgal growth characteristics and subsequent influence on dewatering efficiency. Chem Eng J 151:73–78 20. Mendes-Pinto MM, Raposo MFJ, Bowen J, Young AJ, Morais R (2001) Evaluation of different cell disruption processes on encysted cells of Haematococcus pluvialis: effects on astaxanthin recovery and implications for bio-availability. J Appl Phycol 13:19–24 21. Lorenz RT, Cysewski GR (2000) Commercial potential for Haematococcus microalgae as a natural source of astaxanthin. Trends Biotechnol 18:160–167 22. Doucha J, Lívanský K (2008) Influence of processing parameters on disintegration of chlorella cells in various types of homogenizers. Appl Microbiol Biotechnol 81:431–440 23. Huo H, Wang M, Bloyd C, Putsche V (2008) Life-cycle assessment of energy and greenhouse gas effects of soybean-derived biodiesel and renewable fuels. Argonne National Laboratory, Argonne, IL. http://www.transportation.anl.gov/pdfs/AF/467.pdf. Accessed December 2009 24. Angelidaki I, Sanders W (2004) Assessment of the anaerobic biodegradability of macropollutants. Rev Environ Sci Biotechnol 3:117–129 25. Zmora O, Richmond A (2004) Microalgae production for aquaculture. In: Richmond A (ed) Handbook of microalgal culture. Blackwell, Oxford, pp 365–379 26. Richmond A (2004) Biological principles of mass cultivation. In: Richmond A (ed) Handbook of microalgal culture. Blackwell, Oxford, pp 125–177

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27. Sukenik A, Zmora O, Carmeli Y (1993) Biochemical quality of marine unicellular algae with special emphasis on lipid composition. II. Nannochloropsis sp. Aquaculture 117:313–326 28. Rebolloso-Fuentes MM, Navarro-Pérez A, García-Camacho F, Ramos-Miras JJ, GuilGuerrero JL (2001) Biomass nutrient profiles of the microalga Nannochloropsis. J Agric Food Chem 49:2966–2972 29. SIEMENS (2008) Sludge dryers (company brochure EPS-SLUDGEDRY-USA-BR-0908). http://www.water.siemens.com/SiteCollectionDocuments/Product_Lines/Dewatering_ Systems/Brochures/EPS-SLUDGEDRY-USA-BR-1008.pdf Accessed 8 July 2010 30. Prueksakorn K, Gheewala SH, Malakul P, Bonnet S (2010) Energy analysis of Jatropha plantation systems for biodiesel production in Thailand. Energy Sustain Develop 14:1–5 31. Pleanjai S, Gheewala SH (2009) Full chain energy analysis of biodiesel production from palm oil in Thailand. Appl Energy 86:S209–S214 32. Zemke PE, Wood BD, Dye DJ (2010) Considerations for the maximum production rates of triacylglycerol from microalgae. Biomass Bioenergy 34:145–151 33. Vicente G, Bautista LF, Gutiérrez FJ, Rodríguez R, Martínez V, Rodríguez-Frómeta RA, Ruiz-Vázquez RM, Torres-Martínez S, Garre V (2010) Direct transformation of fungal biomass from submerged cultures into biodiesel. Energy Fuels 24:3173–3178

Characterization of Oligosaccharides with MALDI-TOF/MS Derived from Japanese Beech Cellulose as Treated by Hot-Compressed Water Kazuchika Yamauchi and Shiro Saka

Abstract  Japanese beech was treated with two-step hot compressed water (first step, 230°C/10 MP/15 min: second step; 270°C/10 MP/15 min) and obtained various cellulose-derived compounds in the second step with relatively high molecular weights were characterized by MALDI-TOF/MS. As a result, cellulose-derived products such as cello-triose, cello-tetraose, cello-pentaose, cello-hexaose, celloheptaose, cello-octaose, and cello-nonaose, and their dehydrated compounds were identified. In spite of the fact that for these cellulose-derived products, supercritical water treatment in our previous study resulted in the dehydration and fragmentation reactions at the reducing end, two-step hot-compressed water treatment resulted only in dehydration reaction. This suggests that hot-compressed water treatment would be milder than that of supercritical water. These results indicate further that the MALDI-TOF/MS is a powerful tool to analyze the molecular structures of hydrolyzed oligosaccharides and evaluate decomposition pathway of lignocellulosics as treated with hot-compressed water. Keywords  Cello-oligosaccharides • Hot-compressed water • Japanese beech • MALDI-TOF/MS

1 Introduction Bioethanol from lignocellulosics has recently been attracted as an alternative liquid fuel for gasoline engine. Since lignocellulosics is the most abundant biomass resource on the earth, bioethanol from lignocellulosics can play an important role

K. Yamauchi (*) and S. Saka Graduate school of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan e-mail: [email protected]; [email protected]

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in mitigating the greenhouse gas emission [1, 2] and developing the sustainable society for the future [3]. Lignocellulosics is a composite material of cellulose, hemicellulose encrusted with lignin [4] which can be converted into fermentable sugars for ethanol production. Cellulose, however, is a crystalline polysaccharide composed of glucose linked together by (1 → 4)-glycosidic bonds making up about 40–50% of the dry wood mass. Acid hydrolysis with sulfuric acid has been used most frequently for saccharification of lignocellulosics to ferment for ethanol production [5–8]. In this process, water-soluble sugars are separated from lignin. However, conventional yeast fermentation is able to convert hexoses such as glucose and mannose etc to ethanol, but neither pentoses such as xylose and arabinose, nor oligo-/polysaccharides. Therefore, it is necessary efficiently to hydrolyze lignocellulosics into hexoses. In our previous study, a new process of bio-ethanol production from lignocellulosics, by hot-compressed water treatment followed by acetic acid fermentation and hydrogenolysis has been developed [9]. The first stage of this process is based on two-step semi-flow hot-compressed water treatment. This stage can hydrolyze and decompose hemicellulose and cellulose separately without any catalysts used. The second stage is based on acetic acid fermentation in which not only hexoses and pentoses, but also uronic acids, oligosaccharides, dehydrated and fragmented products from saccharides were found out to be all converted to acetic acid by Clostridium thermoaceticum and Clostridium thermocellum. The final stage of this process is hydrogenolysis of the obtained acetic acid to ethanol. In this paper, cellulose-derived oligosaccharides from Japanese beech obtained by two-step semi-flow hot-compressed water treatment were analyzed with Matrix assisted laser desorption ionization combined with time-of-flight mass spectrometry (MALDI-TOF/MS) to characterize for its molecular structures, and elucidate decomposition pathway of lignocellulosics as treated with hot-compressed water. The elucidated pathway will be useful to study the potential of the following acetic acid fermentation in the new ethanol production process.

2 Materials and Methods 2.1 Two-Step Hot-Compressed Water Treatment Japanese beech (Fagus crenata) wood flour (18 mesh-passed) was used for hotcompressed water treatment. The wood flour was, therefore, extracted with ethanol– benzene (1:2 v/v) mixture by using Soxhlet apparatus, and dried at 105°C for 24 h before use. The conditions of the two-step semi-flow hot-compressed water treatment were 230°C/10 MPa/15 min for the first step and 270°C/10 MPa/15 min for the second step as reported in the previous paper [10]. In this study, however, the hot-compressed water-soluble portion collected at the second step mainly composing of the cellulose-derived oligosaccharides was analyzed with MALDI-TOF/MS.

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2.2 MALDI-TOF/MS Analysis The obtained water-soluble portion was then studied by using MALDI-TOF/MS (Axima Performance, Shimadzu, Japan) equipped with a nitrogen laser (337 nm) after being mixed with matrix (DHB; 2,5-dihydroxy benzoic acid) solution, applied to a stainless steel sample slide and dried under vacuum. The obtained data is an average of 20 laser shot analyses. Cello-triose (Glc3), cello-tetraose (Glc4), cellopentaose (Glc5) and cello-hexaose (Glc6) (SEIKAGAKU CORPORATION, Japan) were used as standards of oligosaccharides. Mass spectrum is shown by m/z (mass to charge ratio). It calculates from mass number (m) of ion, and the number of its elementary charge (z). In case of the singly charged ion, the z value equals to one, and the m/z value shows directly mass number. Since saccharide ions have a high affinity with alkali metal ions, sodium ion (Na+: m/z 23) and potassium ion (K+: m/z 39) in the matrix reagent are associated with these saccharide ions during ionization [11].

3 Results and Discussion In our previous study, the decomposition behavior of Japanese beech was studied in two-step semi-flow hot-compressed water treatment (first step: 230°C/10 MPa/ 15 min, second step: 270°C/10 MPa/15 min) [10]. As a result, hemicellulose and cellulose were, respectively, decomposed at the first and second stages. In the first step, xylo-oligosaccharides and xylose, glucuronic acid and acetic acid derived from a major hemicellulose of the hardwood, O-acetyl-4-O-methylglucuronoxylan were found. In addition, monomeric and dimeric lignin derived products were also found in the first step. While in the second step, various hydrolyzed and decomposed products, such as glucose, mannose as isomerized product of glucose, cellooligosaccharides, levoglucosan, were obtained from cellulose. Monosaccharides and other low-molecular weight compounds were able to be characterized [10]. However, it is difficult by these technologies to analyze high molecular weight products, such as oligosaccharides and polysaccharides. Therefore in this study, MALDI-TOF/MS was utilized for characterization of these oligosaccharides and polysaccharides. Figure  1a shows MALDI-TOF/MS spectra of the standard mixture of cellooligosaccharides such as cello-triose (Glc3), cello-tetraose (Glc4), cello-pentaose (Glc5), and cello-hexaose (Glc6). Molecular weights of these compounds are 506, 668, 830 and 992, respectively. Because of the Addison of sodium ion (Na+: m/z 23) in the matrix reagent, corresponding four peaks that show m/z 529.1 (506 + 23), 691.1 (668 + 23), 853.1 (830 + 23), and 1014.9 (992 + 23) were identified. In addition, potassium ion (K+: 39) is also associated with these saccharide ions instead of sodium ion (arrows in Fig. 1a). Figure  1b shows MALDI-TOF/MS spectra of hot-compressed water-soluble portion. The cello-triose (Glc3; m/z 529.2) cello-tetraose (Glc4; 691.3), cello-pentaose

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(Glc5; 853.3), cello-hexaose (Glc6; 1015.2), cello-heptaose (Glc7; 1177.1), cellooctaose (Glc8; 1338.9), and cello-nonaose (Glc9; 1500.7) were identified. Moreover, potassium ion (K+: m/z 23) associated cello-oligosaccharide (Glc3, Glc4, Glc5, Glc6 and Glc7) were also identified as corresponding peaks at m/z 545.2 (506 + 39), 707.3 (668 + 39), 869.2 (830 + 39), 1031.2 (992 + 39) and 1193.1 (1,154 + 39). In addition, additional peaks were appeared as shown by asterisks in Fig. 1b. These peaks must be corresponding to dehydrated cello-oligosaccharides such as cello-tricyl-levoglucosan, cello-tetracyl-levoglucosan, and cello-pentacyl-levoglucosan at m/z 673.3 [691.3 − 18.0], 835.3 [853.3 − 18.0] and 997.2 [1015.2 − 18.0]. Ehara et al., however, demonstrated that the glucose at the reducing end of cellooligosaccharide decompose to levoglucosan by dehydration, erythrose, and glycolaldehyde by fragmentation as treated with supercritical water under the condition of 380°C/40 MP/0.24 s [12]. Such fragmentation reaction did not take place in this hot-compressed water treatment. Therefore, hot-compressed water treatment must be milder than that of supercritical water. Detected peaks in MALDI-TOF/MS analysis derived from oligosaccharides show their parent peaks without any fragmentation. Therefore, the molecular weights of these peaks indicate the intact hydrolyzed compounds themselves by hot-compressed water. Through these lines of evidence on hydrolyzed and dehydrated

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compounds, decomposition pathway of cellulose as treated by the hot-compressed water can be elucidated and the molecular structures of hydrolyzed oligosaccharides can be identified. Such information would be useful to study the potential of the following acetic acid fermentation in the new ethanol production process. These results clearly indicate that the MALDI-TOF/MS is a powerful tool to analyze the molecular structures of hydrolyzed oligosaccharides and decomposition pathway of lignocellulosics as treated with hot-compressed water.

References 1. Yuan JS, Tiller KH, Al-Ahmad H, Stewart NR, Stewart CN (2008) Plants to power: bioenergy to fuel the future. Trends Plant Sci 13(8):421–429 2. Farrell AE, Plevin RJ, Turner BT, Jones AD, O’Hare M, Kammen DM (2006) Ethanol can contribute to energy and environmental goals. Science 311:506–508 3. Hoogwijk H, Faaij A, van den Broek R, Berndes G, Gielen D, Turkenburg W (2003) Exploration of the ranges of the global potential of biomass for energy. Biomass Bioenergy 25:119–133 4. Saka S (2000) Chemical composition and distribution. In: Hon DNS, Shiraishi N (eds) Wood and cellulosic chemistry, 2nd edn. Marcel Dekker, New York, pp 51–81 5. Wyman CE (1994) Ethanol from lignocellulosic biomass: technology, economics, and opportunities. Bioresour Technol 50:3–16 6. Kim KH, Tucker MP, Nguyen QA (2002) Effects of pressing lignocellulosic biomass on sugar yield in two-stage dilute-acid hydrolysis process. Biotechnol Prog 18:489–494 7. Galbe M, Zacchi G (2002) A review of the production of ethanol from softwood. Appl Microbiol Biotechnol 59:618–628 8. Kumar S, Singh SP, Mishra IM, Adhikari DK (2009) Recent advances in production of bioethanol from lignocellulosic biomass. Chem Eng Technol 32(4):517–526 9. Saka S, Phaiboonsilpa N, Nakamura Y, Masuda S, Lu X, Yamauchi K, Miyafuji H, Kawamoto H (2009) Eco-ethanol production from lignocellulosics with hot-compressed water treatment followed by acetic acid fermentation and hydrogenolysis. In: Proceedings of the 17th European biomass conference & exhibition, pp 1952–1957 10. Lu X, Yamauchi K, Phaiboonsilpa N, Saka S (2009) Two-step hydrolysis of Japanese beech as treated by semi-flow hot-compressed water. J Wood Sci 55(5):367–375 11. Gross JH (2004) Mass spectrometry: a textbook. Springer, Berlin 12. Ehara K, Saka S (2002) A comparative study on chemical conversion of cellulose between the batch-type and flow-type systems in supercritical water. Cellulose 9:301–311

Microwave/Infrared-Laser Processing of Material for Solar Energy Taro Sonobe, Kyohei Yoshida, Kan Hachiya, Toshiteru Kii, and Hideaki Ohgaki

Abstract  Several approaches have been studied for microwave material processing for solar energy utilization such as upgrading the photocatalytic activity of TiO2, and improvement of efficiency in polymer solar cell. Recently, we observed the emission of zinc and oxygen plasmas from ZnO ceramics during intense absorption of microwaves as well as the deposition of zinc and zinc oxide films. This finding may lead to development of simple microwave-based methods for preparing thinfilm ZnO, an alternative of ITO thin-film, from ZnO ceramics. The mid-infrared free electron laser-based system is also proposed to investigate the mechanism of interaction between microwave and wide-gap semiconducting materials. Keywords  Free electron laser • Microwave material processing • TiO2 • ZnO

1 Introduction Microwave heating has been progressively applied to research and development in material professing so as to achieve energy conservation and efficiency improvement in conventional industrial processes, since it has several unique advantages such as rapid and selective heating over conventional methods. To date, numerous studies have addressed a novel capability of microwave processing such as the sintering of ceramics [1] and metal powder [2]. Sato et al. have reported that highly pure pig irons are obtained in a 2.45 GHz microwave reactor from powder iron ores with carbon as reducing agent [3]. We have also studied several approaches for microwave material processing toward solar energy utilization

T. Sonobe (*), K. Yoshida, K. Hachiya, T. Kii, and H. Ohgaki Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_12, © Springer 2011

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such as upgrading the photocatalytic activity of TiO2 [4], and improvement of efficiency in polymer solar cell [5]. Recently, we observed the emission of zinc and oxygen plasmas from ZnO ceramics during intense absorption of microwaves as well as the deposition of zinc and zinc oxide films [6]. This finding may lead to development of simple microwave-based methods for preparing thin-film ZnO, an alternative of ITO thin-film, from ZnO ceramics. In this paper, we focus on the mechanism of interaction between microwave and ZnO to emit zinc and oxygen plasmas. A mid-infrared free electron laser based system is also proposed to investigate the mechanism of interaction.

2 Experimental Commercially available ZnO powder (99.9%) was used as the starting material. The powder (1 g) was pressed into a rectangular pellet (27.0 × 6.7 × 1.5 mm3) and then sintered in air in a furnace at 973 K (700°C) for 2 h before microwave heating respectively. The rectangular pellet of ZnO were placed on the quartz wool base in the quartz tube, the inside of the reactor was evacuated continuously using a rotary pump (~103 Pa), and then the samples were heated at the maximum position of the microwave electric field with 500 W of microwave power for 10 min under vacuum. During microwave heating, optical emission spectra from the chamber were measured using a CCD spectrometer from 400 to 1,050 nm in the wavelength. The detail configuration of microwave heating system was reported in the previous work [7]. X-ray diffraction (XRD) analyses were performed on a powder diffractometer (Rigaku RINT-2100). The ultraviolet–visible–near-infrared (UV–vis–NIR) diffuse reflectance spectra of pellets were obtained with a spectrophotometer (JASCO V-670 spectrophotometer) in the wavelength range from 200 to 2,400 nm. PL spectra was obtained by He–Cd laser (325/442 nm, Kimmon) excitation using a monochromator (Zoliz Omni-l 300) and a CCD detector (INTEVAC Mosir 350).

3 Results and Discussion 3.1 Zinc Plasma Emission from Zinc Oxide Ceramics The sintered ZnO pellet showed a marked absorption of the microwave under vacuum at the maximum point of the electric field. During microwave absorption, the sample started to glow intensely and emitted a blue-violet plasma continuously in the quartz tube. In contrast, the intense plasma emissions disappeared immediately when the microwave power was turned off, while red glow of the sample gradually faded. Figure 1 shows the optical emission spectra at 1, 60, 300 s and immediately after MW power off subsequent to the start of the plasma emission. The important spectral features observed are the transition at 458, 472, 481, and 636 nm, which are indentified

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as arising from neutral zinc; the transitions at 589 and 773 nm, which are identified as arising from singly ionized zinc [8]; and the transitions at 777 and 845 nm, which correspond to neutral oxygen [8]. In addition, a broad peak at approximately 500–1,000 nm that gradually increased in intensity was observed after 30 s; it can possibly be attributed to some different luminescence induced by the microwave electric field. This broad luminescence can be still observed for several seconds after the microwave power was turned off. Moreover, the same luminescence can be induced without any plasma emission when microwave is irradiated on the sample at high temperature. Figure  2 show the microwave power dependence of the broad

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luminescence from ZnO and its peak intensity at 695 nm over applied microwave electric field. It is found that the peak intensity is monotonically increased with increasing the applied microwave electric field. The peak positions are not shifted while increasing temperature. This suggests the distinct behavior from black body radiation. After the emission of microwave plasma, black metallic films as well as white films were deposited on the inner wall of the quartz tube. Figure 3 shows Photograph of the quartz tube reactor after MW plasma emission and XRD patterns of (a) black product on the quartz wall, and (b) white product on the quartz wall. It is interesting that zinc phase is identified at 36.0° (002), 38.7° (100), and 42.8° (101) in the black metallic film, while the white film exhibits the wurtzite structure of ZnO [9]. These results clearly indicate that one part of the zinc plasma was reoxidized by the atomic oxygen plasma after emission in the microwave electric field, while the other was deposited to form zinc and zinc oxide films outside the microwave electric field in the tube reactor. Figure  4 shows the PL spectra of black product on the quartz wall and white product on the quartz wall. A green emission band of photoluminescence at 2.0–2.8 eV was observed, while the near-band-edge peak at 3.25 eV was observed only in black product. The former green luminescence at 2.0–2.8 eV is characteristic of the localized electronic states of lattice defects such as oxygen vacancies, zinc vacancies, so on in ZnO [10], and the latter at 3.25 eV is of near-band-edge luminescence from excitation, which is barely observed. Therefore, it is suggested that thin film fabrication from ZnO ceramics can be feasible after the optimization of microwave applied condition. Figure  5 shows the UV–vis–NIR absorption coefficients obtained from the diffuse reflectance spectra using the Kubelka–Munk relationship for the material sintered at 700°C and subjected to microwave irradiation. As expected from their

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Wavelength [nm] Fig.  5  UV–Vis–NIR absorption coefficient obtained from diffuse reflectance spectra with the Kubelka–Munk relationship for ZnO pellets (a) sintered in air at 700°C, and MW heating in vacuum [6]

white color before microwave irradiation, the sintered pellets display little absorption at a wavelength of 410 nm. On the other hand, the sample exposed to the microwave plasma displays marked absorption from 400 to 2,400 nm. This suggests the emergence of numerous electronic states in the bandgap of ZnO during the time that the microwave plasma was glowing.

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PL intensity (arb. unit)

(a) sintered in air at 700°C (b) MW heating in vacuum

2

2.5

3

3.5

Photon Energy [eV] Fig. 6  PL spectra of ZnO pellets (a) sintered in air at 700°C and (b) MW heating in vacuum [6]

This modification of the electronic states in the bandgap can also be observed in Fig.  6, which shows a green emission band of photoluminescence at 2.0–2.8  eV after microwave irradiation, in contrast to the broad and weak emission bands observed at 1.7–2.7 eV before microwave heating. These bands are characteristic of the localized electronic states of point defects, such as oxygen vacancies, zinc vacancies, zinc interstitials, oxygen interstitials, and oxygen anti-sites [10]. In addition, the near-band-edge UV emission at 3.0–3.4 eV was clearly separated into two peaks after plasma emission, compared with the single overlapped peak before microwave irradiation. A computational study partially demonstrated that the electronic states in the bandgap of ZnO were modified distinctly because of the introduction of defects [11], and it suggests that such variety of defect electronic states yield broad PL band during the emission of zinc and oxygen plasma under microwave irradiation. The distinct reaction of microwave with TiO2 (Rutile) and ZnO [6, 7], which have an almost similar value of bandgap energy and its offset [12], is possibly caused by the different localized electronic states of point defects in TiO2 and ZnO. We can clearly observe that zinc and oxygen plasma were produced directly from the ceramic by microwave irradiation in vacuum, suggesting the occurrence of plasma emission from the ceramics under microwave electric field [6, 7]. As a result, zinc and zinc oxide films were produced directly from the ceramics without using zinc metal and oxygen gas as source materials. Thus, this finding may lead to the development of simple microwave-based methods for preparing thin film ZnO from ceramics, which can contribute to solve the shortage of ITO production.

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Fig. 7  Schematic diagram of MIR-FEL based PL measurement system (color figure online)

3.2 Mid-Infrared Free Electron Laser Based System It is well known that an infrared region light has a good resonance with phonon in some solid compounds such as metal oxides. In particular, ZnO of wide bandgap semiconducting materials shows unique electrical and optical properties through coupling of phonon with electronic structures, resulting in photochemical phenomena with microwave irradiation [6, 7]. The broad and long life time luminescence from ZnO in Figs. 1 and 2 is, possibly, the trace of interaction between microwave and wide-gap semiconducting materials. However, the direct mechanism of interaction between microwave and ZnO to increase a temperature is not clear, since the frequency of microwave is too low to directly couple with phonon and electron. Therefore, direct excitation of phonon by mid-infrared free electron laser based PL measurement system has been developing to investigate the mechanism (Fig. 7).

4 Conclusion We studied the effects of microwave irradiation on ZnO ceramics under vacuum to clarify emission of zinc and oxygen plasmas from ceramics, while focusing on the optical properties of the samples. We observed the production of atomic zinc and

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oxygen plasmas from the ceramic during intense absorption of microwaves under vacuum, which is similar to what was observed with TiO2 [6], and we obtained the films composed of zinc metal and zinc oxide. We also investigated the changes in the optical properties of sample surfaces. The UV–vis–NIR absorption coefficient spectra displayed a marked absorption from 400 to 2,400 nm for the sample after plasma emission. In addition, the PL spectra showed a green emission band at 2.0–2.8 eV as well as two separated peaks near the band-edge. We suggest that zinc and oxygen plasma can be produced from the ceramic by microwave irradiation under vacuum. As a result, we were able to produce films composed of zinc metal and zinc oxide without using zinc metal or oxygen gas as a source material. This finding may lead to development of simple microwavebased methods for fabricating thin films from ceramics. In order to investigate the mechanism of interaction between microwave and ceramics, a mid-infrared free electron laser based PL measurement system was proposed. Acknowledgement  The authors would like to express their gratitude to Professor Naoki Shinohara and Dr. Tomohiko Mitani at Research Institute for Sustainable Humanosphere, Kyoto University for their support of microwave equipment. A part of this study was supported by the Kyoto University Global COE program on Energy Science in the Age of Global Warming and a Grant-in-Aid for Young Scientists B (20760468) from the Japan Society for the Promotion of Science.

References 1. Jida S, Suemasu T (1999) J Appl Phys 86:839 2. Roy R, Agrawal D, Cheng J, Gedevanishvili S (1999) Nature 399:668 3. Sato M, Matsubara A, Takayama S, Sudo S, Motojima O, Nagata K, Ishizaki K, Hayashi T, Agrawal D, Roy R (2006) In: Proceedings of the 5th Sohn international symposium on advanced processing of metals and materials, p 157 4. Sonobe T, Jitputti J, Hachiya K, Mitani T, Shinohara N, Yoshikawa S (2008) Jpn J Appl Phys 47:8460 5. Yoshikawa O, Sonobe T, Sagawa T, Yoshikawa S (2009) Appl Phys Lett 94:083301 6. Sonobe T, Mitani T, Hachiya K, Shinohara N, Ohgaki H (2010) Jpn J Appl Phys 49:080219 7. Sonobe T, Mitani T, Shinohara N, Hachiya K, Yoshikawa S (2009) Jpn J Appl Phys 48:116003 8. Sansonetti JE, Martin WC (2005) J Phys Chem Res Data 34:1559 9. Li Y, Meng GW, Zhang LD, Phillipp F (2000) Appl Phys Lett 76:2011 10. Lin B, Fu Z, Jia Y (2001) Appl Phys Lett 79:943 11. Catlow CRA, French SA, Sokol AA, Al-Sounaidi AA, Woodley SM (2008) J Comput Chem 29:2234 12. Roy Morrison S (1980) Electrochemistry at semiconductor and oxidized metal electrodes. Plenum, New York

Pongamia pinnata as Potential Biodiesel Feedstock Fadjar Goembira and Shiro Saka

Abstract  A review study was done for recent research on Pongamia pinnata, which has mostly emphasized on its potential as fuel feedstock. Regarding the raw Pongamia oil characteristics, seed oil-content is mostly considered. Some biodiesel production methods have been applied, but not the relatively novel process, such as supercritical treatment. Fuel properties and engine performances were also considered by some researchers, although the research results were so much varied. This could be due to the possible existence of varied species, indicated by various scientific names, which are all considered as Pongamia pinnata. Keywords  Biodiesel feedstock • Oil characteristics • Pongamia pinnata

1 Introduction The use of biodiesel as diesel engine fuel is nowadays increasing rapidly. This is due to the depletion of fossil-fuel reserves that makes petrodiesel price increased significantly, and some considerations towards some environmental issues, e.g., global warming due to CO2 emissions from fossil-fuel combustion. In order to fulfill biodiesel demands, various feedstock is being used, such as soybean in the United States, rapeseed in Europe, and palm oil in some Asian countries. However, they are all edible oils, which could create a new problem, i.e., competition between food and energy utilization of the oils. Therefore, some inedible feedstock has started to be taken into consideration, such as Jatropha curcas, and Pongamia pinnata. In this paper, the potential of Pongamia pinnata has been reviewed as biodiesel feedstock and evaluated from the research achievements to clarify the subjects for further study.

F. Goembira and S. Saka (*) Graduate School of Energy Science, Kyoto University, Kyoto, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_13, © Springer 2011

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2 Taxonomical Classification of Pongamia pinnata Pongamia pinnata (L.) Pierre, hereinafter mentioned as Pongamia, is a nitrogen fixing tree that is native to India. This tree grows up to the average height of 8 m in 4 or 5 years with more than 50 cm of trunk diameter [1], and starts to produce seeds that could have initial moisture content around 8.56% [2] at the age of 4–7 years [3]. It survives on most soil types, and can withstand in the highest ambient temperatures of 27–38°C and the lowest of 1–16°C. Moreover, it is highly tolerable to drought and salinity [1, 4]. Pongamia breeding can be done by generative, vegetative [4, 5], and micropropagation methods [6, 7]. Pongamia trees are used as ornamental and shade trees that can also control soil erosion [4]. The wood is used for cooking fuels, and the ash is for dyeing, while the leaves and roots are used as poison sources for fish spears [3]. Extracted seed-oil is traditionally used for soap production, external medications, pesticide, and fuel for lamps or cooking [1]. The seed-cake is used as fertilizer and cattle fodder in spite of containing toxic compounds [8], which could however be pre-treated to minimize the risks [9]. Pongamia was found out in this study to be called Pongamia pinnata (L.) Merr., Pongamia glabra Vent., Milletia pinnata (L.) Panigrahi, Derris indica (Lam.) Bennet, Milletia novo-guineensis Kane & Hat., and Cytisus pinnaus (L.) in literatures [1, 3, 10–12]. Such several scientific namings suggest that Pongamia tree includes some different species or sub-species. As discussed later, fuel characteristics of Pongamia biodiesel are varied very much. This might be due to such different species or sub-species studied as Pongamia pinnata. The potential of Pongamia as biodiesel feedstock is due to its seed-oil content, which has been reported to be varied [2, 10, 13–15], but could be as high as 56% [10]. Furthermore, Pongamia’s productivity is up to 2,250  kg oil/ha/year [13], higher than that of soybean and rapeseed, i.e., 400 and 600  kg/ha/year, respectively. However, Pongamia has to compete with Jatropha curcas that can produce higher yield up to 2,500 kg oil/ha/year [16].

3  Pongamia pinnata as Diesel Engine Fuel 3.1 Straight Pongamia Oil as Biodiesel Blends Although the use of straight Pongamia oil in diesel engine is constrained by its high viscosity, blending it with petrodiesel up to 10 vol% [17] and 50 vol% [18] have been proven to be technically feasible. However, the experiments did not consider some important factors, i.e., long term oxidative stability of the blends, effects of the blends on engine, and the cold flow properties of the recommended fuel blends.

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3.2 Fatty Acid Methyl Esters (Biodiesel) from Pongamia Oil Biodiesel can be produced from Pongamia oil by various methods, as reported by various researchers and summarized in Table  1. As can be seen from Table  1, various biodiesel production methods ended up with different yields. The main issue encountered in biodiesel production from Pongamia oil is high free fatty acid (FFA) content [21, 23–28]. However, at present, no reported research results were found on the use of supercritical treatment, which could handle the high FFA content issue [29, 30]. With regard to the fuel standards, there are two standards that could be referred to, i.e., European (EN-14214), and the United States (ASTM-D6751) standards. Based on the reviewed publications, there are some differences of compliance with the standards, which can be seen in Table 2. Most researchers reported compliance with both standards, although very few researchers measured all parameters. Table 1  Pongamia biodiesel production by various methods Method Reaction temp (°C) Reaction time (min) Yield (%) Ref. One-step catalyzed • • • • • • • • •

Alkali (CH3ONa) Alkali (KOH) Alkali (KOH) + tetrahydrofuran Alkali (KOH) Alkali (solid-Li/CaO) Alkali (CH3ONa) Alkali (solid-ZnO) Alkali (solid-montmorillonite) Alkali (solid-Hb Zeolite)

70 60 60 65 65 60 120 120 120

60 90 90 180 480 60 1,440 1,440 1,440

84 92 95 98 94.9 97.6 47 59 83

[19] [13] [13] [20] [21] [22] [13] [13] [13]

30 30 300 360 120 210 No data No data

89.5

[23]

90.4

[24]

91

[25]

97

[26]

Two-step catalyzed • Acid (H2SO4) +     Alkali (KOH) • Acid (H2SO4) +     Alkali (NaOH) • Acid (ortho-phosphoric) +     Alkali (KOH) • Acid (H2SO4) +     Alkali (NaOH)

45 45 45 45 66 66 65 65

Table 2  Compliance of pongamia biodiesel with some fuel standards Compliance with Method EN-14214 ASTM-D6751 Both standards Viscosity at 40°C – [19, 31] [13, 23, 25–27, 32–34] Acid value – – [19, 26, 31–34] Iodine value [32, 33] Not regulated – Flash point – – [13, 19, 26, 27, 31–36] Cetane number – [19] [22, 26, 27, 31–34]

Incompliance with both standards [22, 35] [13] – [22] –

114 Table 3  Engine test results as reported by various researchers Parameter Drawn conclusion Corrosion Not significant and better than Jatropha biodiesel Engine power Lower than petrodiesel at higher engine speed Thermal efficiency Lower than petrodiesel Fuel consumption Higher than petrodiesel Smoke density Lower than petrodiesel CO emission Lower than petrodiesel Hydrocarbon emission Lower than petrodiesel NOx emission Lower than petrodiesel Higher than petrodiesel Engine noise Lower than petrodiesel

F. Goembira and S. Saka

Ref. [31] [36] [32, 37, 38] [32, 39] [32, 33, 36, 38, 39] [32, 33, 35, 36, 38, 39] [35, 36, 38] [35, 39] [32, 33, 36] [33]

Viscosity is related to the fuel atomization, and potential clogging problem at fuel injectors, while acid value shows the fatty acid content of biodiesel, which is related to the potential of engine corrosion and deposit formation at injectors. As for iodine value, it corresponds to the level of fatty acid unsaturation of biodiesel, which is further related to the fuel oxidative stability. Flash point is connected to fuel volatility that influences safety during storage and transport, while cetane number is used to ensure that complete combustion takes place inside the engine combustion chamber. Further consideration is on the engine test result of Pongamia biodiesel, as summarized in Table  3. From Table  3, it could be concluded that most engine performance parameters show better performance than petrodiesel. Lower engine power and thermal efficiency, together with higher fuel consumption compared to those of petrodiesel are due to lower calorific value of biodiesel than that of petrodiesel [19, 22, 33, 39, 40]. Further, the different results on NOx emission data should be noted, since the higher oxygen content in biodiesel provides higher combustion temperatures together with the higher cetane number of bio­ diesel compared to petrodiesel, i.e., longer residence time in reaction chamber, which will result in promoting more NOx formation during the combustion process.

4 Conclusions Pongamia pinnata has been proven to be one of potential energy crops for biodiesel production based on the results of various research activities. However, there is a lack of consistency of research results related to some fuel properties. This could be due to the possible existence of different sub-species of the plant. Therefore, further research activities on the aspect of plant taxonomy and fuel properties are very important to be done in order to complete the research projects that have been done earlier.

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References 1. Daniel JN (1997) Pongamia pinnata – a nitrogen fixing tree for oilseed. In: NFT highlights. NFTA 97–03 2. Pradhan RC, Naik SN, Bhatnagar N, Swain SK (2008) Moisture-dependent physical properties of Karanja (Pongamia pinnata) Kernel. Ind Crops Prod 28:155–161 3. Duke JA (1983) Pongamia pinnata (L.) Pierre, handbook of energy crops. Purdue University 4. Mukta N, Sreevalli Y (2010) Propagation techniques, evaluation and improvement of the biodiesel plant Pongamia pinnata (L.) Pierre – a review. Ind Crops Prod 31:1–12 5. Kesari V, Krishnamachari A, Rangan L (2009) Effect of auxins on adventitious rooting from stem cuttings of candidate plus tree Pongamia pinnata (L.), a potential biodiesel plant. Trees 23:597–604 6. Sugla T, Purkayastha J, Singh SK (2007) Micropropagation of Pongamia pinnata through enhanced axillary branching. In Vitro Cell Dev Biol Plant 43:409–414 7. Sujatha K, Hazra S (2007) Micropropagation of mature Pongamia pinnata Pierre. In Vitro Cell Dev Biol Plant 43:608–613 8. Singh P, Sastry VSB, Garg AK, Sharma AK, Singh GR, Agrawal DK (2006) Effect of long term feeding of expeller pressed and solvent extracted Karanj (Pongamia pinnata) seed cake on the performance of lambs. Animal Feed Sci Technol 126:157–167 9. Vinay BJ, Sindhu-Kanya TC (2008) Effect of detoxification on the functional and nutritional quality of proteins of Karanja seed meal. Food Chem 106:77–84 10. Ramadan MF, Wahdan KMM, Hefnawy HTM, Kinni SG, Rajanna S, Seshagiri M, Rajanna LN, Seetharam YN, Seshagiri M, El-Sanhoty RMES, Morsel JT (2009) Chromatographic analysis for fatty acids and lipid-soluble bioactives of Derris indica crude seed oil. Chromatographia 70:103–108 11. Scott PT, Pregelj L, Chen N, Hadler JS, Djordjevic MA, Greshoff P (2008) Pongamia pinnata: an untapped resource for the biofuels industry of the future. Bioenergy Resour 1:2–11 12. USDA, ARS, National Genetic Resources Program. Germplasm resources information network – (GRIN) (online database). National Germplasm Resources Laboratory, Beltsville, MD. http://plants.usda.gov/java/profile?symbol=MIPI9. Accessed 24 November 2009 13. Karmee SK, Chadha A (2005) Preparation of biodiesel from crude oil of Pongamia pinnata. Bioresour Technol 96:1425–1429 14. Kaushik N, Kumar S, Kumar K, Beniwal RS, Kaushik N, Roy S (2007) Genetic variability and association studies in pod and seed traits of Pongamia pinnata (L.) Pierre in Haryana, India. Genet Resour Crop Evol 54:1827–1832 15. Mukta N, Murthy IYLN, Sripal P (2009) Variability assessment in Pongamia pinnata (L.) Pierre germplasm for biodiesel traits. Ind Crops Prod 29:536–540 16. Razon LF (2009) Alternative crops for biodiesel feedstock, CAB reviews: perspectives in agriculture, veterinary science, nutrition, and natural resources 2009, 4 No. 056. CAB Int 17. Bajpai S, Sahoo PK, Das LM (2009) Feasibility of blending Karanja vegetable oil in petrodiesel and utilization in a direct injection diesel engine. Fuel 88:705–711 18. Agarwal AK, Rajamanoharan K (2009) Experimental investigations of performance and emissions of Karanja oil and its blends in a single cylinder agricultural diesel engine. Appl Energy 86:106–112 19. Srivastava PK, Verma M (2008) Methyl ester of Karanja oil as an alternative renewable source energy. Fuel 87:1673–1677 20. Meher LC, Kulkarni MG, Dalai AK, Naik SN (2006) Transesterification of Karanja (Pongamia pinnata) oil by solid basic catalysts. Eur J Lipid Sci Technol 108:389–397 21. Meher LC, Dharmagadda VSS, Naik SN (2006) Optimization of alkali-catalyzed transesterification of Pongamia pinnata oil for production of biodiesel. Bioresour Technol 97:1392–1397 22. Sarma AK, Konwer D, Bordoloi PK (2005) A comprehensive analysis of fuel properties of biodiesel from Koroch seed oil. Energy Fuels 19:656–657

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23. Sharma YC, Singh B (2008) Development of biodiesel from Karanja, a tree found in rural India. Fuel 87:1740–1742 24. De BK, Bhattacharyya DK (1999) Biodiesel from minor vegetable oils like Karanja oil and Nahor oil. Fett/Lipid 101:404–406 25. Sahoo PK, Das LM (2009) Process optimization for biodiesel production from Jatropha, Karanja, and Polanga oils. Fuel 88:1588–1594 26. Naik M, Meher LC, Naik SN, Das LM (2008) Production of biodiesel from high free fatty acid Karanja (Pongamia pinnata) oil. Biomass Energy 32:354–357 27. Das LM, Bora DK, Pradhan S, Naik MK, Naik SN (2009) Long-term storage stability of biodiesel produced from Karanja oil. Fuel 88:2315–2318 28. Karmee SK, Chandna D, Ravi R, Chadha A (2006) Kinetics of base-catalyzed transesterification of triglycerides from Pongamia oil. J Am Oil Chem Soc 83:873–877 29. Kusdiana D, Saka S (2004) Effects of water on biodiesel fuel production by supercritical methanol treatment. Bioresour Technol 91:289–295 30. Warabi Y, Kusdiana D, Saka S (2004) Reactivity of triglycerides and fatty acids of rapeseed oil in supercritical alcohols. Bioresour Technol 91:283–287 31. Kaul S, Saxena RC, Kumar A, Negi MS, Bhatnagar AK, Goyal HB, Gupta AK (2007) Corrosion behavior of biodiesel from seed oils of Indian origin on diesel engine parts. Fuel Process Technol 88:303–307 32. Baiju B, Naik MK, Das LM (2009) A comparative evaluation of compression ignition engine characteristics using methyl and ethyl esters of Karanja oil. Renew Energy 34:1616–1621 33. Nabi MN, Hoque SMN, Akhter MS (2009) Karanja (Pongamia pinnata) biodiesel production in Bangladesh, characterization of Karanja biodiesel and its effect on diesel emissions. Fuel Process Technol 90:1080–1086 34. Sarin A, Arora R, Singh NP, Sarin R, Malhotra RK, Kundu K (2009) Effect of blends of palm– Jatropha–Pongamia biodiesels on cloud point and pour point. Energy 34:2016–2021 35. Sureshkumar K, Velraj R, Ganesan R (2008) Performance and exhaust emission characteristics of a CI engine fueled with Pongamia pinnata methyl ester (PME) and its blends with diesel. Renew Energy 33:2294–2302 36. Sahoo PK, Das LM, Babu MKG, Arora P, Singh VP, Kumar NR, Varyani TS (2009) Comparative evaluation of performance and emission characteristics of Jatropha, Karanja, and Polanga based biodiesel as fuel in a tractor engine. Fuel 88:1698–1707 37. Kalbande SR, More GR, Nadre RG (2008) Biodiesel production from non-edible oils of Jatropha and Karanj for utilization in electrical generator. Bioenergy Resour 1:170–178 38. Rao TV, Rao GP, Reddy KHC (2008) Experimental investigation of Pongamia, Jatropha, and Neem methyl esters as biodiesel on C.I. engine. Jordan J Mech Ind Eng 2(2):117–122 39. Raheman H, Phadatare AG (2004) Diesel engine emissions and performance from blends of Karanja methyl ester and diesel. Biomass Energy 27:393–397 40. Sahoo PK, Das LM (2009) Combustion analysis of Jatropha, Karanja, and Polanga based biodiesel as fuel in a diesel engine. Fuel 88:994–999

Construction of a Novel Strictly NADPHDependent Pichia stipitis Xylose Reductase by Site-Directed Mutagenesis for Effective Bioethanol Production Sadat Mohammad Rezq Khattab, Seiya Watanabe, Masayuki Saimura, Magdi Mohamed Afifi, Abdel-Nasser Ahmad Zohri, Usama Mohamed Abdul-Raouf, and Tsutomu Kodaki Abstract  Xylose reductase (XR) is one of the key enzymes for bio-ethanol production from lignocellulosic biomass. Intercellular redox imbalance, caused by different coenzyme specificity of XR and Xylitol dehydrogenase (XDH), has been thought to be one of the main factors of xylitol excretion. We previously succeeded by protein engineering to improve the ethanol production by reverse the XDH dependence from NAD+ to NADP+. In this study, we employed protein engineering to construct a novel strictly NADPH dependent XR from Pichia stipitis by site directed mutagenesis, in order to effective recycling of cofactor between XR and XDH, which subsequently reduce xylitol accumulation. Double mutant E223G/ S271A showed strictly NADPH dependent with 90% of wild-type activity. Keywords  Coenzyme specificity • Site-directed mutagenesis • Xylose reductase

1 Introduction Recombinant S. cerevisiae can ferment xylose through a fungal pathway involving two heterologous oxidoreductase genes. In this pathway, Pichia stipitis xylose reductase (PsXR), which prefers NADPH, reduces xylose to xylitol followed by Pichia stipitis xylitol dehydrogenase (PsXDH), which exclusively requires NAD+, oxidizes xylitol into xylulose. S. cerevisiae xylulokinase (XK) naturally phosphorylates xylulose to xylulose-5-phosphate, which is then metabolized by the glycolytic

S.M.R. Khattab, S. Watanabe, M. Saimura, and T. Kodaki (*) Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan e-mail: [email protected] S.M.R. Khattab, M.M. Afifi, and U.M. Abdul-Raouf Faculty of Science, Al-Azhar University, Assiut Branch, Assiut 71524, Egypt A.A. Zohri Faculty of Science, Assiut University, Assiut 71515, Egypt T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_14, © Springer 2011

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pathway via the pentose phosphate pathway. Overexpression of XK improves the efficiency of xylose fermentation [1, 2]. Although this fungal pathway is highly expressed in S. cerevisiae, the efficiency of ethanol production is somewhat obstructed by the unfavorable accumulation of xylitol due to the redox imbalance of coenzyme specificities between XR and XDH. Protein engineering has been widely used to address this issue. Since PsXDH accepts only NAD+, many researchers have changed the preference of XR to NADH in order to achieve effective recycling of NAD+/NADH pathway [3–5]. We previously succeeded to improve the fermentation process and ethanol production by convert the cofactor usage of XDH to NADP+ dependent [6]. In this study, site-directed mutagenesis of PsXR was performed to construct a strictly NADPH-dependent XR, in order to effective recycling of NADPH cofactor between XR and XDH.

2 Materials and Methods 2.1 Cloning of PsXR Gene and Mutants Construct The plasmid pQE-81L (Qiagen, Hilden, Germany), a plasmid for conferring N-terminal (His)6 -tag on the expressing proteins, was used for protein expression. The plasmid vector was constructed by introducing BamHI and PstI digestion sites to the gene using the following primers: XR Forward (5¢-CATACGGATCCTTCTATTAAGTTGAAC-3¢) and XR-Reversal (5¢-CTTGGCTGCAGTTAGACGAAGATAGG-3¢) [Bold letter for introducing BamHI and PstI digestion sites]. The amplified DNA fragment was introduced into the BamHI/PstI sites in pQE-81L. All XR mutations were introduced by site-directed mutagenesis, which was performed using PfuTurbo DNA polymerase (Stratagene) and PCR Thermal Cycler PERSONAL (TaKaRa, Otsu, Japan). The codons used for mutations which introduced in this study were as follows: E223G (GAA→GGA), E237A (GAG→GCG), E237D (GAG→GAC), E237G (GAG→GGG), S271T (TCC→ACC), S271A (TCC→GCC) and N272D (AAC→GAC). The PCR products were treated with DpnI enzyme to avoid cloning of the template plasmid. The mutations were confirmed by DNA sequencing and verified XR mutants were transferred in Escherichia coli DH5a for further use.

2.2 Expression and Purification of PsXR Enzymes E. coli DH5a cells harboring the expression plasmids were grown at 37°C until 0.6 at 600 nm on super broth medium (per liter: 12 g tryptone, 24 g yeast extract, 5 ml glycerol, 3.81 g KH2PO4 and 12.5 g K2HPO4; pH 7.0) containing 50 mg ampicillin l−1. Protein expressions were induced by added 1 mM IPTG after cooling and incubate further 24  h at 18°C. The cells were then harvested and sonicated in 20  ml

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buffer A (50  mM sodium phosphate, pH 6.0, containing 0.3  M NaCl, 10  mM xylose, 5 mM 2-mercaptoethanol and 10 mM imidazole) per liter of culture for a total of 4–5 min, with cooling intervals on ice. Cell debris was removed by centrifugation. Ni2+-chelating affinity method (Ni-NTA-6xHis Spin Columns, QIAGEN) was used for purification of PsXR mutants after equilibration with buffer A, the cell lysate was loaded, washed four times by buffer B (buffer A containing 10%, v/v, glycerol and 50  mM instead of 10  mM imidazole), and the enzymes were then eluted by buffer C (buffer B containing 250  mM instead of 50  mM imidazole). Purified enzymes were confirmed by 10% acrylamide SDS-PAGE.

2.3 Enzyme Assays and Kinetic Parameters Enzymes assays was described previously [7] and the kinetic parameters were calculated by Line weaver–Burk plots. Protein concentrations were determined using the Bio RAD Quick Start Bradford 1x Dye Reagent (Bio-Rad Laboratories, CA, USA) and measured the absorbance at 280 nm.

3 Results and Discussion Although the differences between the two bindings sites of NAD(P)H are subtle and unclear [8], residues that can potentially increase NADPH dependency were selected. The first residue was Glu223, which is located at the end of the short rigid helix b7 of Candida tenuis XR crystal structure and has a critical effect on the contact of hydrogen bonds with both 2¢- and 3¢-hydroxyl groups of the adenosine ribose [9]. E223G was constructed and the enzyme activity with NAD(P)H were determined. XR activity with NADH was completely lost (Fig. 1). These results are in agreement with those of a previous study on other AKR enzymes in which analogous interactions were observed and there were no obvious potential contacts that precluded the absence of a 2¢ phosphate allowing for NADH binding [8]. Furthermore, this residue was subjected to a mutation trial and the result revealed that alteration of this site inhibits NADH binding [4]. In 3D structure model of PsXR, it has been reported that Glu223 and Phe236 can form three and two hydrogen bonds with NAD+, respectively [10]. As shown in Fig. 1, the specific activity of E223G mutant with NADPH was 39% compared to WT; catalytic efficiency was 12% compared to WT (Table 1). Although there were a decrease in the activity and catalytic efficiency compared to WT, E223G showed strict NADPH dependency. The second selected residue for single mutation was Glu237. This residue was selected from the 3D structure modeling and has one hydrogen bond that interacts with NAD+ but not with NADP+ [10]. This residue did not show any positive results for NADPH preference. Their NADPH/NADH ratio of WT, E237A, E237D, and E237G were 1.42, 1.6, 1.7, and 1.5 respectively as shown in Fig.  1. Although,

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Activity(U/mg)

16 14 12 10 8 6 4 2 0 WT

E223G E237A E237D E237G S271A S271T N272D

GD

GA

Fig. 1  Enzyme activities of PsXR wild-type and mutated enzymes. Black and grey bars indicated the activities with NADPH and NADH respectively; Values are average ±SD, n = 3

Table 1  Kinetic parameters of PsXR wild-type and mutants Kinetic parameters Enzymes Cofactor Km xylosea (mM) Kmb (mM) kcatb (min−1)

kcat/Km (mM−1/min−1)

XR WT NADPH 97.1 ± 4.8 16.2 ± 1.4 622 ± 22 38.6 ± 2.9 S271A NADPH 70.6 ± 8.7 30.1 ± 3.7 874 ± 50 29.0 ± 0.3 E237A NADPH 74.6 ± 9.1 60.3 ± 0.9 562 ± 27 9.31 ± 0.50 E223G NADPH 92.4 ± 8.5 57.4 ± 8.5 269 ± 36 4.71 ± 0.21 NADPH 270 ± 25 26.6 ± 1.2 528 ± 13 19.9 ± 0.6 GA♣ XR WT NADH 170 ± 23 30.6 ± 1.0 449 ± 22 14.7 ± 1.4 S271A NADH 180 ± 12 53.3 ± 4.4 480 ± 42 9.00 ± 0.40 E237A NADH 135 ± 14 9.97 ± 2.94 309 ± 23 33.1 ± 8.5 E223G NADH ND* ND ND ND GA♣ NADH ND ND ND ND a Xylose concentration was 400 mM *ND: Not detected, ♣Double mutant E223G/S271A b Six different concentrations of NAD(P)H between 50 and 300 mM were used

E237A mutant didn’t reveal any improvement toward NADPH, E237A showed positive results in terms of improved NADH preference as its catalytic efficiency increased by 2.26-fold with NADH and decreased by 4.14-fold with NADPH compared to WT (Table 1). For the second round of mutations, we investigated the binding sites of PsXR with NAD(P)H results. Mutations of Lys270 of PsXR improved the preference of NADH, while that of S271A increased the preference of NADPH [11]. S271A showed increase activity of NADPH with 126% of WT and decrease activity of NADH with 82% of WT. An increase of the activities in N272D with both NAD(P)H were observed [11], where the activity were 130% for both NADPH and NADH.

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Based on these results, a combination of S271A or N272D mutants with Glu223 mutants is expected to increase the activity of XR with NADPH. Double E223G/N272D (GD) showed small improvement in NADPH dependent and much improvement with NADH, where the activity increased 127% compared with mutant E223G with NADPH and the activity restored from zero to two with NADH (See Fig. 1). S271A mutant had greater NADPH preference as shown in Fig. 1. The activities with NADPH and NADH were 126% and 85% compared to WT, respectively. On the other hand, the activity of S271T mutant with NAD(P)H was nearly abolished as shown in Fig. 1, although this choice was selected by sequence alignment of Hypocrea jecorina XR, which has a strong NADPH preference. These data reflected the importance of this residue for NADPH preference and encouraged us to perform further investigations by combining S271A and Glu223 mutants. A combination of site-directed mutations of the residues Glu223 and S271A produced unique results. The double mutant E223G/S271A (GA) showed improvement in activity with NADPH compared to single Glu223 mutant. Figure 1 shows the specific activity of the double mutant GA. Its activity was 90% compared to WT. As shown in Table  1, the kcat of WT, and GA were 622, and 528  min−1, respectively; their Km for xylose were 97.1, and 270 mM, respectively; and their catalytic efficiencies were 38.6, 19.9 mM−1/min−1, respectively. We previously succeeded in improving xylose fermentation and ethanol production by combining PsXR WT with the mutated PsXDH which accepts only NADP+ (i.e., quadruple ARSdR mutant) [7], and overexpression of XK [12, 13]. It may provide further clues for understanding of importance of coenzyme specificities of XR and XDH, using the strictly NADPH-dependent PsXR of this study with the strictly NADP+-dependent PsXDH. It could be expected that more efficient xylose fermentation is achieved by an effective recycling of coenzymes of NADPH between XR and XDH. Acknowledgment  This work was supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan. It was also supported by a Grant-in-Aid for Young Scientists (B) (no. 21760636 to S.W.) and the Global Center of Excellence (GCOE) program for the “Energy Science in the Age of Global Warming,” a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports, and Culture, Japan.

References 1. Eliasson A, Christensson C, Wahlbom CF, Hahn-Hägerdal B (2000) Anaerobic xylose fermentation by recombinant Saccharomyces cerevisiae carrying XYL1, XYL2, and XKS1 in mineral medium chemostat cultures. Appl Environ Microbiol 66:3381–3386 2. Matsushika A, Inoue H, Kodaki T, Sawayama S (2009) Ethanol production from xylose in engineered Saccharomyces cerevisiae strains: current state and perspectives. Appl Microbiol Biotechnol 84:37–53 3. Bengtsson O, Hahn-Hägerdal B, Gorwa-Grauslund MF (2009) Xylose reductase from Pichia stipitis with altered coenzyme preference improves ethanolic xylose fermentation by recombinant Saccharomyces cerevisiae. Biotechnol Biofuels 2:9

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4. Liang L, Zhang J, Lin Z (2007) Altering coenzyme specificity of Pichia stipitis xylose reductase by the semi-rational approach CASTing. Microb Cell Fact 6:36 5. Petschacher B, Nidetzky B (2008) Altering the coenzyme preference of xylose reductase to favor utilization of NADH enhances ethanol yield from xylose in a metabolically engineered strain of Saccharomyces cerevisiae. Microb Cell Fact 7:9 6. Watanabe S, Saleh AA, Pack SP, Annaluru N, Kodaki T, Makino K (2007) Ethanol production from xylose by recombinant Saccharomyces cerevisiae expressing protein engineered NADP+-dependent xylitol dehydrogenase. J Biotechnol 130:316–319 7. Watanabe S, Kodaki T, Makino K (2005) Complete reversal of coenzyme specificity of xylitol dehydrogenase and increase of thermostability by the introduction of structural zinc. J Biol Chem 280:10340–10349 8. Wilson DK, Kavanagh KL, Klimacek M, Nidetzky B (2003) The xylose reductase (AKR2B5) structure: homology and divergence from other aldo-keto reductases and opportunities for protein engineering. Chem Biol Interact 143–144:515–521 9. Kavanagh KL, Klimacek M, Nidetzky B, Wilson DK (2003) Structure of xylose reductase bound to NAD+ and the basis for single and dual co-substrate specificity in family 2 aldo-keto reductases. Biochem J 373:319–326 10. Wang JF, Wei DQ, Lin Y, Wang YH, Du HL, Li YX, Chou KC (2007) Insights from modeling the 3D structure of NAD(P)H-dependent D-xylose reductase of Pichia stipitis and its binding interactions with NAD and NADP. Biochem Biophys Res Commun 359:323–329 11. Watanabe S, Pack SP, Saleh AA, Annaluru N, Kodaki T, Makino K (2007) The positive effect of the decreased NADPH-preferring activity of xylose reductase from Pichia stipitis on ethanol production using xylose-fermenting recombinant Saccharomyces cerevisiae. Biosci Biotechnol Biochem 71:1365–1369 12. Matsushika A, Inoue H, Watanabe S, Kodaki T, Makino K, Sawayama S (2009) Efficient bioethanol production by a recombinant flocculent Saccharomyces cerevisiae strain with a genome-integrated NADP+-dependent xylitol dehydrogenase gene. Appl Environ Microbiol 75:3818–3822 13. Matsushika A, Watanabe S, Kodaki T, Makino K, Sawayama S (2008) Bioethanol production from xylose by recombinant Saccharomyces cerevisiae expressing xylose reductase, NADP+dependent xylitol dehydrogenase, and xylulokinase. J Biosci Bioeng 105:296–299

Evaluation of Different Methods to Determine Monosaccharides in Biomass Harifara Rabemanolontsoa, Sumiko Ayada, and Shiro Saka

Abstract  Sulfuric acid, trifluoroacetic acid (TFA) and acid methanolysis methods for hydrolysis were evaluated and compared using standard monosaccharides and standard oligosaccharides. As a result, sulfuric acid hydrolysis was found to be suitable to determine crystalline cellulosic and amorphous xylanic saccharides. TFA method, however, could not achieve complete hydrolysis of cellooligosaccharides and xylooligosaccharides, while acid methanolysis was considered appropriate to determine monosaccharides in amorphous hemicellulose. Based on these lines of evidence, a combination of sulfuric acid hydrolysis and acid methanolysis methods was concluded to be appropriate to get accurate monosaccharides determination in biomass species, and the application of this combined method to Japanese beech, bamboo and rice husk samples presented reasonable results. Keywords  Acid methanolysis • Biomass • Monosaccharide • Sulfuric acid • TFA

1 Introduction Biomass resources being abundant and available have high prospectives for different applications such as biofuels, biochemicals and biomaterials. For those matters, one of the most interesting constituents of biomass is carbohydrate. Accurate determination of the monosaccharides is often needed to evaluate the potential of a given biomass for a specific application, to monitor processes or to improve them in an efficient way. Several methods are available to determine monosaccharides, and sulfuric acid hydrolysis method is one of the mostly used ones for its convenience as it can be

H. Rabemanolontsoa, S. Ayada, and S. Saka (*) Graduate School of Energy Science, Kyoto University, Kyoto 606-8501, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_15, © Springer 2011

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combined with lignin determination [1]. Some authors, however, stated that sulfuric acid hydrolysis decomposes labile sugars but it has never been reported which kinds of monosaccharides are decomposed. Trifluoroacetic acid (TFA) hydrolysis and acid methanolysis are yet other widely used methods to depolymerize biomass polysaccharides. Although there are few comparisons of these methods [2], their potentials were not deeply evaluated. Therefore, the present work aims to evaluate those three most commonly used methods to determine monosaccharides in biomass. For that purpose, standard monosaccharides and oligosaccharides were studied for their hydrolysis behaviors and the obtained information was applied to different biomass species such as Japanese beech (Fagus crenata), rice husk (Oryza sativa) and bamboo (Phyllostachys pubescens). Based on these comparisons, an improved combined methodology was proposed for an accurate determination of monosaccharides in biomass.

2 Materials and Methods Japanese beech (Fagus crenata), husk and straw of rice (Oryza sativa) as well as bamboo (Phyllostachys pubescens) samples were firstly milled with Wiley mill (1029-C, Yoshida Seikakusho Co., Ltd.) and sieved. The fractions containing particles 150–500 mm in size were extracted with acetone. The extractive-free samples were, then, used for the monosaccharides determinations through sulfuric acid hydrolysis and acid methanolysis methods. As for TFA method, holocellulose was used, prepared with sodium chlorite according to Wise et al. [3]. Sulfuric acid hydrolysis was carried out according to the method described by Saeman et al. [4], with minor modifications. In brief, 5 ml of 72% sulfuric acid was added to 0.3 g of extractive-free samples and left to pre-hydrolyze at 20–25°C for 2  h. The samples were, then, transferred to a 500  ml flask with addition of 186 ml of water to bring sulfuric acid concentration to around 3%. The flasks were, then, autoclaved at 121°C for 30  min. Subsequently, the samples were cooled, brought into 500  ml and filtered with 0.45  mm Millipore membrane filter. The filtrate was neutralized using Dionex OnGuard II A cartridge and analyzed with high-performance anion-exchange chromatography (HPAEC) using CarboPac PA1 as column. For TFA hydrolysis, 30 ml of 2 M TFA was added to 300 mg of holocellulose, and the mixture was autoclaved for 1 h at 121°C [5]. TFA was, then, evaporated and dried. The obtained monosaccharides were, then, diluted with 250 ml of deionizer water and analyzed with HPAEC using CarboPac PA1 as column. Acid methanolysis was performed following the method of Sundberg et al. [6] according to which 2 ml of 2 M HCl in anhydrous methanol was poured to 10 mg of extractive-free sample for methanolysis at 100°C for 3 h, followed by neutralization with 100 ml of pyridine, cooling and sylilation using 150 ml HMDS (hexamethyldisilazane) with 80 ml TMCS (trimethylchlorosilane) overnight. The samples were, then, analyzed with gas chromatography.

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3 Results and Discussion 3.1 Evaluation of Sulfuric Acid Hydrolysis As shown in Table 1, sulfuric acid hydrolysis applied to standard monosaccharides engendered sugar decomposition mostly for rhamnose (Rhm, 66.2 wt% degraded), mannose (Man, 9.5 wt%), arabinose (Ara, 8.1 wt%) and galactose (Gal, 8.1 wt%). Those monosaccharides are therefore very sensitive to the treatment, whereas xylose (Xyl) and glucose (Glc) are quite stable. The results for xylose and glucose from sulfuric acid hydrolysis are, thus, reliable. Hence, sulfuric acid hydrolysis is appropriate for neutral monosaccharides determination in cellulose and xylan.

3.2 Evaluation of TFA Hydrolysis TFA hydrolysis was evaluated using rice straw and bamboo extractive-free samples as well as cellooligosaccharides (Cel5 and Cel4) and xylooligosaccharides (Xyl6). As represented in Table 2, the hydrolysates from rice straw, bamboo and cellotetraose (Cel4) still had some oligosaccharides. The 95 wt% xylose yielded

Table 1  Monosaccharides recovery after sulfuric acid treatment Recovery (wt% of standard monosaccharides) Glc Man Gal Rhm Xyl Ara Standards 1 100.0 87.2 89.4 36.7 99.4 84.1 Standards 2 100.0 97.2 94.7 35.0 99.0 91.6 Standards 3 100.0 87.2 91.7 29.8 100.0 100.0 Mean 100.0 90.5 91.9 33.8 99.5 91.9 Glc glucose, Man mannose, Gal galactose, Rhm rhamnose, Xyl xylose, Ara arabinose

Table  2  Monosaccharides and oligosaccharides yield from 2  M TFA hydrolysis of rice straw, bamboo and standard oligosaccharides Yield (wt% of oven-dried samples and oligosaccharides) Hexoses Pentoses Oligosaccharides Glc Man Gal Rhm Xyl Ara Xyl2 Xyl4 Cel2 Cel4 Cel5 Rice straw 17.9 0.4 2.3 0 29.6 0.2 0.04 0.99 0.43 0.06 0 Bamboo 8.5 0.4 0.4 0 27.1 2.5 0.15 0 0 0 0.02 Xyl6 0 0 0 0 95.0 0 0 0 0 0 0 Cel5 98.0 0 0 0 0 0 0 0 0 0 0 Cel4 97.0 0 0 0 0 0 0 0 0 1.98 0 Glc glucose, Man mannose, Gal galactose, Rhm rhamnose, Xyl xylose, Ara arabinose, Xyl2 xylobiose, Xyl4 xylotetraose, Xyl6 xylohexaose, Cel2 cellobiose, Cel4 cellotetraose, Cel5 Cellopentaose

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from xelohexaose (Xyl6) corresponds actually to 83.6 wt% of dehydrated xylose, which is lower than the purity given by the supplier (>95%). Those results demonstrate that 2  M TFA hydrolysis cannot achieve complete hydrolysis of the oligosaccharides.

3.3 Evaluation of Acid Methanolysis Acid methanolysis was evaluated by Bertaud et al. [7] using different aldo-uronic acid, oligosaccharides, polysaccharides and thermomechanical pulp. For aldo-uronic acid analyses, they discovered that the glucuronosyl linkage between methylglucuronic acid and xylose was cleaved only to the extent of 70–80%. That finding might explain the slightly lower xylose yielded from acid methanolysis of Japanese beech and rice husk as compared with the data by sulphuric acid hydrolysis shown in Table 3. As for the oligosaccharide and polysaccharide model compounds, the amount of monosaccharides resulting from the acid methanolysis corresponded well to the quantity given by the suppliers [7]. Therefore, acid methanolysis is considered appropriate for the determination of hemicellulosic monosaccharides.

Table  3  Carbohydrate composition of three biomass species determined by three hydrolysis methods and the combined method Yield (wt% of original oven-dried biomass basis) Hexoses Pentoses Acid sugars Biomass Glc Man Gal Rhm Xyl Ara Gal-A Glc-A S Hol Japanese beech H2SO4 hydrolysis 41.7 1.4 0.5 0.4 21.3 0.3 0 0 58.6 TFA hydrolysis 1.7 0.7 0.2 0.2 14.0 0.1 0 0 14.9 Acid methanolysis 0.5 1.4 3.6 2.3 19.2 0.9 1.7 0.3 26.5 Combined method 41.7 1.4 3.6 2.3 21.3 0.9 1.7 0.3 65.5 Bamboo H2SO4 hydrolysis TFA hydrolysis Acid methanolysis Combined method

40.2 2.3 1.4 40.2

0.4 0 0.5 0.5

0.5 0.1 3.2 3.2

0 0 0.3 0.3

20.3 10.6 23.4 23.4

0.9 0.6 4.2 4.2

0 0 0.3 0.3

0 0 0.6 0.6

55.6 12.0 30.0 64.9

Rice husk H2SO4 hydrolysis TFA hydrolysis Acid methanolysis Combined method

34.9 3.5 0.5 34.9

0 0 0.2 0.2

0.9 0.2 1.7 1.7

0.1 0.0 0.3 0.3

17.8 4.2 17.6 17.8

1.5 0.4 2.1 2.1

0 0 0.3 0.3

0 0 0.1 0.1

49.3 7.4 20.1 51.3

Glc glucose, Man mannose, Gal galactose, Rhm rhamnose, Xyl xylose, Ara arabinose, Gal-A galacturonic acid, Glc-A glucuronic acid, S Hol saccharides in holocellulose S Hol = 162/180 S Hexoses + 132/150 S Pentoses + 176/194 S Acid sugars

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3.4 Comparison of Different Hydrolysis Methods The monosaccharides compositions of three biomass samples subjected to different methods are represented in Table 3. Note that neither the amounts of acetyl groups nor other functional groups were determined. For that reason, the calculated saccharides in holocellulose lack those functional residues to correspond to the actual holocellulose. The high glucose yields obtained from sulfuric acid method represent mostly the crystalline cellulosic saccharides. If starch, other hemicellulosic glucose or both are present in the sample, they will also be included into the determined glucose. The results clearly show that neither methanolysis nor 2  M TFA hydrolysis can manage to cleave crystalline polysaccharides. The glucose contents obtained through those methods represent hemicellulosic glucose or amorphous parts of cellulose. TFA and sulfuric acid methods presented low hemicellulosic saccharides when applied to biomass samples. Therefore, those results from the biomass samples are in accordance with the results from the standard samples. Acid methanolysis gave high values of galactose (Gal), rhamnose (Rhm), mannose (Man) and arabinose (Ara), confirming its ability to cleave hemicellulosic and pectic glycosidic bonds. Although xylose (Xyl) yields for Japanese beech and rice husk are slightly lower by acid methanolysis, the results are still comparable to those of sulfuric acid hydrolysis. Consequently, both methods are valid for xylose determination in biomass. These lines of evidence can suggest that only one simple method to determine complete carbohydrate composition does not exist. Thus, combination of sulfuric acid hydrolysis method for glucose determination and acid methanolysis method for other types of simple sugars is proposed for an appropriate determination of monosaccharides in biomass species. For the particular case of xylose, the higher value between the ones from sulfuric acid hydrolysis and acid methanolysis is chosen. The obtained results by such a combined method is reasonably good as shown in Table 3.

4 Conclusions Sulfuric acid and TFA hydrolyses as well as acid methanolysis were evaluated. As a result, TFA method was discovered to be insufficient for a complete oligosaccharides hydrolysis. The inability of acid methanolysis to cleave xylose–glucuronic acid bonds in xylan is suggested but the xylose contents obtained from acid methanolysis were still comparable to those from sulfuric acid hydrolysis. Both methods are, therefore, considered reasonable for xylose determination. Furthermore, for its capacity to depolymerize crystalline cellulose without decomposition of the resulting glucose, sulfuric acid hydrolysis can be appropriate for glucose determination. Although acid methanolysis represented a slight drawback in the xylose determination, it is still superior to the other two methods for hemicellulosic and pectic sugar

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determinations. Therefore, the combination of sulfuric acid hydrolysis and acid methanolysis is proposed for an appropriate determination of monosaccharides in biomass. The glucose content is suggested to be determined by sulfuric acid hydrolysis, whereas the other monosaccharides by acid methanolysis. In the case of xylose, the higher value obtained between the two methods is taken as the xylose content. Acknowledgement  This work was accomplished under financial support from Kyoto University Global Center of Excellence (GCOE) Energy Science Program.

References 1. Sluiter A, Hames B, Ruiz R, Scarlata C, Sluiter J, Templeton D, Crocker D (2008) Determination of structural carbohydrates and lignin in biomass. In: Laboratory analytical procedure (LAP). National Renewable Energy Laboratory (NREL), Golden, CO 2. Willför S, Pranovich A, Tamminen T, Puls J, Laine C, Suurnäkki A, Saake B, Uotila K, Simolin H, Hemming J, Holmbom B (2009) Carbohydrate analysis of plant materials with uronic acidcontaining polysaccharides-A comparison between different hydrolysis and subsequent chromatographic analytical techniques. Ind Crops Prod 29(2–3):571–580 3. Wise LE, Murphy M, Daddieco AA (1946) Chlorite holocellulose, its fractionation and bearing on summative wood analysis and on studies on the hemicelluloses. Pap Trade 122(2):210–218 4. Saeman JF, Moore WE, Mitchell RL, Millet MA (1954) Techniques for the determination of pulp constituents by quantitative paper chromatography. Tappi 37(8):336–343 5. Albersheim P, Nevins DJ, English PD, Karr A (1967) A method for the analysis of sugars in plant cell-wall polysaccharides by gas-liquid chromatography. Carbohydr Res 5(3):340–345 6. Sundberg A, Sundberg K, Lillandt C, Holmbom B (1996) Determination of hemicelluloses and pectins in wood and pulp fibres by acid methanolysis and gas chromatography. Nord Pulp Pap Res J 11(4):216–220 7. Bertaud F, Sundberg A, Holmbom B (2002) Evaluation of acid methanolysis for analysis of wood hemicelluloses and pectins. Carbohydr Polym 48(3):319–324

Pyrolysis and Secondary Reaction Mechanisms of Softwood and Hardwood Lignins at the Molecular Level Mohd Asmadi, Haruo Kawamoto, and Shiro Saka

Abstract  Primary pyrolysis and secondary reactions of Japanese cedar (Cryptomeria japonica, a softwood) and Japanese beech (Fagus crenata, a hardwood) wood lignins were studied with open-top and closed-ampoule reactors in N2 at 400–600°C. Milled wood lignins (MWL) isolated from these wood samples were used along with several model aromatic compounds (guaiacol and syringol and their pyrolysis intermediates). Although the low molecular weight products from beech MWL included more syringyl-type of aromatic rings in primary pyrolysis, in the secondary reaction step, the yields of syringyl-characteristic products were quite lower than those of guaiacyl-characteristic products. Contrary to this, the beech MWL and syringol produced more coke. These results suggest that the syringyl-characteristic products are converted preferentially into coke, instead of other low MW products. The molecular mechanisms of these tar conversions are also discussed with the model compound data. Additional OCH3 group in syringylunit enhances the coke formation through double opportunity of the OCH3 rearrangement pathway, which includes o-quinonemethide as a key intermediate step for coke formation. Keywords  Coke formation • Guaiacol • Lignin • Pyrolysis • Syringol

1 Introduction Softwood and hardwood lignins have different aromatic nuclei compositions, i.e. guaiacyl– (4-hydroxy-3-methoxyphenyl)–type in softwood and guaiacyl– + syringyl– (3,5-dimethoxy-4-hydroxyphenyl)–types in hardwood. Such structural differences would make the pyrolysis behaviors of softwood and hardwood lignins

M. Asmadi, H. Kawamoto (*), and S. Saka Graduate School of Energy Science, Kyoto University, Kyoto, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_16, © Springer 2011

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different. In our previous study, some different features were identified in the pyrolysis behaviors of Japanese cedar (Cryptomeria japonica, a softwood) and Japanese beech (Fagus crenata, a hardwood) wood samples with an ampoule reactor (N2/600°C/40–600 s) [1]. Coke formation from the volatile products was more extensive in beech than cedar. Although lignin-derived tar components were different just after devolatilization, these became similar at longer pyrolysis time. In this paper, primary pyrolysis and secondary reactions behaviors of Japanese cedar and Japanese beech milled wood lignins (MWLs) were compared and discussed at the molecular level.

2 Experimental Milled wood lignins were isolated from Japanese cedar and Japanese beech wood samples, and guaiacol, syringol and other aromatic compounds were purchased from Nacalai Tesque co. As an indicator of syringyl/guaiacyl (S/G) ratio, the syringaldehyde/vanillin (S/V) ratio obtained by alkaline nitrobenzene oxidation was 2.3 to the beech MWL. Two types of reactors were used in this study, namely open-top and closed ampoule reactors. Open-top reactor was used to study primary pyrolysis, since the volatile (tar) products are cooled down on the upper-side of the glass-wall before suffering from the secondary reactions. On the other hand, secondary reactions of the volatile products are expected in the closed ampoule reactor, became the volatiles are heated further at the set temperature. Sample (10 mg) was put in the bottom of a Pyrex glass ampoule (internal diameter: 8.0 mm; length, 120 mm; glass thickness, 1.0 mm). After exchanging the air inside the reactor with N2, the ampoule was closed (case of closed ampoule reactor) and heated in a muffle furnace at 600°C for 40–600  s. After pyrolysis, the ampoule was cooled by flowing air for 60 s, and the non-condensable gases produced were analyzed by Micro GC with thermal conductivity detector (TCD). Then, inside of the ampoule was extracted with methanol (2.0 ml), and the soluble fraction was analyzed by GC/MS to determine the lignin-derived low molecular weight (MW) products. The insoluble residues were obtained at the bottom of the reactor and on the glass wall at the upper side of the reactor are defined as “primary char” and “secondary char (coke)”, respectively. The amounts of gaseous, tar and char factions were determined by weight difference after gas collection or extraction. Pyrolysis and products analysis were similarly conducted with the open-top reactor, which consists of a glass tube reactor (10 mm in diameter and 300 mm long) attached with a nitrogen bag. Sample was placed at the bottom of the tube reactor and about two third of the reactor from the bottom was heated in muffle furnace at 400°C for 180 s. Thermogravimetric (TG) analysis was also conducted with 1 mg sample at the heating rate: 10°C/min and N2 flow rate: 10 ml/min.

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3 Results and Discussion 3.1 Primary Pyrolysis of Milled Wood Lignins Primary pyrolysis behavior is discussed with the results obtained with the open-top reactor and TG analysis. As a result, the total char (primary + secondary char) yields were lower in beech MWL, and this indicates that the devolatilization efficiency is much higher in beech than cedar. This would arise from the lower content of the condensed-types of the interphenylpropane-unit-linkages in hardwood lignins. It is reported that the ether-types of the linkages are cleaved much more easily in pyrolysis, although the condensed-types are resistant for pyrolytic depolymerization [2]. Gas yields and compositions were not so different for these MWLs. In TG analysis, the DTG peak temperature (326°C) of the beech MWL was lower than that of cedar MWL (353°C). Thus, the pyrolytic devolatilization of beech MWL occurs at lower temperature than that of cedar MWL. These results suggest that the ether linkages with syringyl-moiety in hardwood lignin were cleaved at lower temperature, although further study is necessary to confirm this hypothesis. With the open-top reactor, in which the volatile products were stabilized for secondary reactions, the beech MWL gave 4-substituted syringols with various >C=C< and >C=O types of side-chains as well as the corresponding 4-substituted guaiacols. The cedar MWL gave only the guaiacol-type products. Thus, the primary pyrolysis pathways and reactivities were found not so different for the syringyl- and guaiacyl-types of lignins.

3.2 Secondary Reactions of Volatile (tar) Components Guaiacol and syringol were used as model aromatic nuclei of lignin in order to know the decomposition pathways of these aromatic nuclei and their reactivities, focusing on the role of additional OCH3 group in syringyl-unit, before discussing the secondary reactions mechanism of MWLs. The coke yields were significantly larger in syringol than guaiacol at 600°C in the closed ampoule reactor. Contrary to this, the yields of low MW products were generally lower in syringol. These results are consistent with the earlier observation, i.e., more extensive coke formation in beech MWL which have syringyl-units as well as the guaiacyl-units. Thus, the syringyl-units are suggested to form more coke instead of the low MW products. Low MW tar components which were identified by GC/MS are shown in Fig. 1. Pyrocatechol (1), 4-methylcatechol (2), 2,4-xylenol (3), o-cresol (4) and phenol (5) were identified from guaiacol, while syringol gave 3-methoxycatechol (6), pyrogallol (7), 5-methylpyrogallol (8), 3-methylcatechol (9), 2-methoxy-6-­ methylphenol (10), 2,6-xylenol (11) and 2,4,6-trimethylphenol (12). Accordingly,

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Syringyl-characteristic products CH3

CH3

O–CH3− Homolysis products

OH

OH OH

Pyrocatechol (1)

H3CO

OH

OH

HO

OH

OH

OH

CH3

3-Methylcatechol (9)

CH3

OH

CH3

2,4-Xylenol (3)

OH OH

4-Methylcatechol 3-Methoxycatechol Pyrogallol 5-Methylpyrogallol (2) (6) (7) (8) HO

OCH3− Rearrangement products

HO

OH

OH

H3CO

CH3

o-Cresol (4)

OH

Phenol (5)

OH

CH3 H3C

2-Methoxy-6methylphenol (10)

OH

CH3 H3C

CH3

OH

CH3

2,6-Xylenol 2,4,6-Trimethylphenol (11) (12)

Fig. 1  GC/MS-detectable tar components from guaiacol and syringol

compounds 1–5 and 6–12 were suggested as guaiacyl- and syringyl-characteristic products, respectively. Formation of these products was explained with the two-types of reactions, i.e. O–CH3 homolysis (H) and OCH3 rearrangement (R) types-reactions as shown in Fig. 2 (case of syringol). The O–CH3 bond homolysis forms phenoxy radicals and methyl radical which are further converted into catechols and methane, respectively, by abstracting hydrogen. Pyrogallols were the products in this pathway from syringol. In addition, syringol produced more methane than guaiacol. This would be explained with additional OCH3 group in syringol. There is more opportunity for O–CH3 homolysis in syringol. The 4-methylated products 2, 3, 8 and 12 may be formed through coupling of conjugated radicals formed from phenoxy radicals with methyl radical. In contrast, the OCH3 rearrangement pathway gives aromatic-CH3 structures such as cresols and xylenols. Hosoya et al. also suggested that o-quinonemethides are key intermediates for coke formation [3]. Additional OCH3 group in syringol makes the chance of this rearrangement reaction twice. This double opportunity for coke formation may increase the coke yield, while decrease the low MW tar components in pyrolysis of syringol. This was also supported by the pyrolysis results of 3-methoxycatechol (6) and 2-methoxy-6-methylphenol (10) as pyrolysis intermediates from syringol. Both compounds with OCH3 group produced large amount of coke even in the early stage of pyrolysis such as 80 s, while other intermediates 1–5, 7–9, 11 and 12, which do not have OCH3 group, did not form any coke at 80 s. Although the reactivity was not so high, demethoxylation reaction was also observed for syringol. This causes the structural change from syringol to guaiacol. Thus, guaiacyl-characteristic products 1–5 were also observed from syringol, although their yields were only very low. Demethoxylation mechanism in the course of OCH3 rearrangement pathway was proposed (not shown in this paper).

Pyrolysis and Secondary Reaction Mechanisms

133 Coke

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Coke

Fig.  2  A proposed mechanism of pyrolytic conversion of syringol based on two-types of r­ eactions, i.e., O–CH3 bond homolysis (H) and OCH3 rearrangement (R)

As observed with the open-top reactor, the 4-substituted syringols and guaiacols with various >C=C< and >C=O types of side-chains were also observed after a short heating time as 80 s at 600°C in the closed ampoule reactor. However, these primary products disappeared quickly in the closed ampoule reactor where all volatile products are heated further. This changed the GC/MS-detectable tar composition dramatically. As for the secondary products, compounds 1–12, which were identified from guaiacol and syringol, were found to be the major GC/MS-detectable tar components from the beech MWL; the cedar MWL gave the guaiacyl-characteristic compounds 1–5. Figure  3 shows the time-course changes of the GC/MS-detectable tar components from the MWLs as compared with those from guaiacol and syringol. The yields from MWLs were much lower (less than one tenth) than those from guaiacol and syringol. This can be explained with the loss in the primary pyrolysis (as char) and the side-chains attached to the 4-positions of guaiacol and syringol in the chemical structures of primary pyrolysis products. Nakamura et al. [4] and Hosoya et al. [5] reported that guaiacol derivatives with >C=C< types of side-chains underwent the condensation reaction before OCH3 homolysis and rearrangement reactions took place.

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Fig.  3  Formation and decomposition behaviors of GC/MS-detectable low MW tar products in pyrolysis of beech and cedar MWLs (N2/600°C) as compared with those of guaiacol and syringol. Solid-circle: guaiacyl-characteristic products, open-circle: syringyl-characteristic products; O–CH3 homolysis products: 1 and 2 (guaiacyl-characteristic), 6–9 (syringyl-characteristic); OCH3 rearrangement products: 3–5 (guaiacyl-characteristic), 10–12 (syringyl-characteristic)

Syringol produced smaller amount of the GC/MS-detectable tar products than guaiacol. Besides the reasons described above, the pyrolysis experiments with the intermediates showed that the syringyl-characteristic products 6–12 were more reactive than the guaiacyl-characteristic products 1–5 for further decomposition reactions. Additional OCH3, OH and CH3 groups increase the pyrolytic reactivities of the intermediates. Such inherent nature of syringyl-moiety may be a reason for much smaller yields of the syringyl-characteristic products in pyrolysis of MWLs. Interestingly, the yields of syringyl-characteristic O–CH3 homolysis products were especially lower in beech MWL. Pyrolysis results of a mixture of guaiacol and syringol suggested that the interactions between these two aromatic moieties may be a reason. The yields of the O–CH3 homolysis products, especially 3-methoxycatechol (6), were significantly lowered at short heating time as 40 or 80 s by mixing.

4 Conclusions Devolatilization in primary pyrolysis step was more effective in Japanese beech MWL than Japanese cedar MWL. This may arise from the lower content of condensed type interphenylpropane-unit-linkage in beech MWL. In primary pyrolysis step, the GC/MS-detectable tar components were 4-substituted syringols and guaiacols with >C=C< and >C=O side-chains for beech MWL, while those from cedar MWL were only corresponding guaiacols. In the secondary reaction step, the syringyl-characteristic products disappeared quickly, and hence, the compositions were changed into only guaiacyl-characteristic products even in beech MWL. Based on the results of model aromatic nuclei, i.e., guaiacol and syringol, such observation was explained with the different reactivities of these aromatic moieties. Syringol produced more coke instead of the GC/MS-detectable low MW products.

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This was explained with additional OCH3 group in syringol. Double opportunity of the OCH3 rearrangement reaction was proposed for such higher coke yield, since o-quinonemethide formed in this reaction sequence is a key intermediate in coke formation. Although the reactivity was not so high, demethoxylation of syringol into guaiacol was also observed. As for the reactivities of the intermediates, the syringyl-characteristic products were found to be more reactive for further decomposition into gas and coke than the guaiacyl-characteristic ones. For these reasons, syringyl-moiety inherently produces much less amount of GC/MS-detectable low MW products. Interactions between guaiacyl and syringyl moieties were also suggested to reduce the low MW products, especially syringyl-characteristic O–CH3 homolysis products, from beech MWL. Acknowledgement  This work was supported by the Kyoto University Global COE program of “Energy Science in the Age of Global Warming”, and a Grant-in-aid for scientific research (B)(2) (No. 20380103, 2008.4-2011.3).

References 1. Asmadi M, Kawamoto H, Saka S (2010) Pyrolysis reactions of Japanese cedar and Japanese beech woods in a closed ampoule reactor. J Wood Sci 56(4):319–330 2. Kawamoto H, Horigoshi S, Saka S (2007) Pyrolysis reactions of various lignin model dimers. J Wood Sci 53(2):168–174 3. Hosoya T, Kawamoto H, Saka S (2009) Role of methoxyl group in char formation from ligninrelated compounds. J Anal Appl Pyrol 84:78–87 4. Nakamura T, Kawamoto H, Saka S (2007) Condensation reactions of some lignin related compounds at relatively low pyrolysis temperature. J Wood Chem Technol 27:121–133 5. Hosoya T, Kawamoto H, Saka S (2008) Secondary reactions of lignin-derived primary tar components. J Anal Appl Pyrol 83:78–87

Fractionation of Japanese Cedar and Its Characterization as Treated by Supercritical Water Mahendra Varman and Shiro Saka

Abstract  Supercritical water treatment (380°C/100  MPa/8  s) was applied to extractive-free sapwood portion of Japanese cedar (Cryptomeria japonica) and the fractionated products were comparatively characterized, for water-soluble portion and water-insoluble portion composed of methanol-soluble portion and methanolinsoluble residue. As a result, the water-soluble portion was determined to be composed of carbohydrate-derived products such as organic acids, sugar-decomposed products, lignin-derived products, etc. The methanol-soluble portion was, on the other hand, mainly composed of lignin-derived products, whereby it consisted of solely guaiacyl-type lignin, representing the nature of softwood. The methanol-insoluble residue was also mainly composed of lignin to be 92.0% in its content. Moreover, the phenolic hydroxyl content determined by aminolysis method was 36.3 PhOH/100 C9. Furthermore, an alkaline nitrobenzene oxidation analysis indicated that, the methanolinsoluble residue was less in oxidation products compared to untreated sample. These lines of evidence suggest that methanol-insoluble residue is composed of lignin with more condensed-type of linkages with high phenolic hydroxyl groups. In addition, the water-soluble portion could be utilized for organic acid production, whereas the methanol-soluble portion and its insoluble residue for phenolic chemical production. Keywords  Carbohydrate-derived products • Japanese cedar • Lignin-derived products • Phenolic hydroxyl content • Supercritical water treatment

1 Introduction Wood is one of the most abundant biomass resources with waste continuously being generated from forest thinning, lumbering, etc. These wastes are lignocellulosics which could be efficiently converted and utilized for meeting the future fuel and

M. Varman and S. Saka (*) Graduate School of Energy Science, Kyoto University, Kyoto 606-8501, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_17, © Springer 2011

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chemical needs. In order to convert these biomass resources, an environmentally clean and rapid process is preferred. In this work, therefore, supercritical water treatment was chosen and Japanese cedar (Cryptomeria japonica), as an abundantly available lignocellulosics in Japan, was investigated.

2 Experimental Extractive-free sapwood portion of Japanese cedar (Cryptomeria japonica) was utilized in this study. The supercritical water biomass conversion system used in this study was associated with a batch-type reaction vessel made of Inconel-625 with a volume of 5 ml [1]. The supercritical water treated (380°C/100 MPa/8 s) product was fractionated by filtration into water-soluble portion and water-insoluble residue after 12 h refrigeration. The water-insoluble residue was washed with methanol to fractionate it further by filtration into methanol-soluble portion and methanol-insoluble residue. These fractionated portions were characterized separately. Characterization of the water-soluble portion was conducted with high performance liquid chromatography (HPLC), ion chromatography (IC), capillary electrophoresis (CE) and ultraviolet–visible (UV–Vis) spectrophotometry. Meanwhile, characterization of the methanol-soluble portion was conducted with gas chromatography–mass spectrometry (GC–MS) for qualitative analysis of low molecular weight products. The conditions of these instruments are elaborated in our previous paper [2]. For characterization of the methanol-insoluble residue, the determinations of lignin content, phenolic hydroxyl content and alkaline nitrobenzene oxidation products were conducted and compared with those of the untreated sample. The methods employed here are described in [2–5].

3 Results and Discussion 3.1 Fractionation of the Products Table 1 shows the obtained yields for fractionated water-soluble portion and waterinsoluble residue after supercritical water treatment (380°C/100  MPa/8  s). The yield of water-soluble portion was the highest. It is known that the water-soluble Table 1  Yields of fractionated water-soluble portion and water-insoluble residue for Japanese cedar as treated by supercritical water at 380°C/100 MPa/8 s Yield (wt%) Water-insoluble Water-soluble Methanol-soluble Methanol-insoluble 74.8 20.4 4.8

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portion contains more carbohydrate-derived products [1]. Compared with subcritical water treatment [1], supercritical water treatment is more efficient for decomposing the carbohydrate portion. The water-insoluble residue, on the other hand, contains more lignin-derived products.

3.2 Characterization of Water-Soluble Portion The yields of products in the fractionated water-soluble portion are shown in Table  2. Decomposed products of saccharides such as dihydroxyacetone (DA), levoglucosan (LG), furfural (FR), organic acids and so on were detected apart from lignin-derived products (LP). The yields of organic acids are more than 10% in Japanese cedar. Due to the long temperature rising time of approximately 22 s for the reaction vessel to reach 380°C, the carbohydrate portion in Japanese cedar has been decomposed into organic acids during the subsequent 8 s supercritical water treatment. Organic acids are valuable chemicals and could be converted into methane by anaerobic fermentation [6]. Even though the yield of unknowns are higher compared with organic acids, there is a potential for the yield of organic acids to be increased further by prolonging treatment time [6].

Table 2  Yields of products in the fractionated water-soluble portion of Japanese cedar Water-soluble (wt%) DA LG MG FR AA GA LA LP UNK 7.6 1.6 0.3 0.6 5.0 4.9 1.9 8.4 44.5 DA dihydroxyacetone, LG levoglucosan, MG methylglyoxal, FR furfural, AA acetic acid, GA glycolic acid, LA lactic acid, LP lignin-derived products, UNK unknowns

3.3 Characterization of Methanol-Soluble Portion For the methanol-soluble portion, GC–MS analysis was performed. The total-ion chromatogram of the methanol-soluble portion obtained by GC–MS analysis is shown in Fig. 1. Based on the GC–MS analysis, the molecular weight (MW), the mass fragmentation pattern obtained by electron ionization and the peaks identified from Fig. 1 are shown in Table 3. Identification of the peaks was conducted with the retention times and mass fragmentation patterns compared with those of the authentic compounds. However, peaks 9 and 10 were determined from the mass fragmentation pattern reported by [7]. It could then be elucidated that these identified phenolic compounds must be mainly derived from lignin and the obtained guaiacyl-type lignin-derived products represent the nature of softwood. As a result, the methanol-soluble portion shows the potential for many phenolic chemicals to be recovered, as treated by supercritical water.

Fractionation of Japanese Cedar and Its Characterization as Treated by Supercritical Water

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Fig. 1  Total-ion chromatogram for the methanol-soluble portion in GC–MS analysis Table  3  Identified products in the methanol-soluble portion by its mass fragments in GC–MS analyses Peak no. MW Major mass fragments Compound 1 124 109, 124, 81 Guaiacol 2 138 123, 138, 95 4-Methylguaiacol 3 152 137, 152, 122 4-Ethylguaiacol 4 166 137, 166, 122, 94 4-Propylguaiacol 5 146, 118, 117, 123, 161 Unknown 6 164 149, 164, 132, 103, 77 Eugenol 7 164 164, 149, 131 cis-Isoeugenol 8 164 164, 149, 103, 77 trans-Isoeugenol 9 162 147, 162, 119, 91, 77 4-Propynylguaiacol 10 162 162, 147, 119, 91, 77 1-(4-Hydroxy-3-methoxyphenyl)allene 11 166 151, 166, 123 Acetoguaiacone 12 180 137, 179, 122 Guaiacylacetone 13 174, 132, 160, 146, 116 Unknown 14 178 178, 135, 108, 77 trans-Coniferylaldehyde 15 176, 204, 177, 161, 148 Unknown 16 189, 146, 174, 116 Unknown 17 194 194, 167, 139, 111, 177 Ferulic acid 18 188, 202, 160, 145, 132 Unknown Peak numbers are corresponding to those depicted in Fig. 1

3.4 Characterization of the Methanol-Insoluble Residue Table 4 shows the lignin content for the methanol-insoluble residue. It shows that the lignin content was 92.0% after ash correction of Klason lignin. This suggests that the methanol-insoluble residue is mostly composed of lignin and thus cellulose

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M. Varman and S. Saka Table  4  Lignin contents and the number of phenolic hydroxyl groups over 100 phenylpropane (C9) units of lignin (PhOH/100 C9) determined by aminolysis method for the methanol-insoluble residue and untreated sample Methanol-insoluble residue (wt%) Untreated sample (wt%) Yield of lignin upon Lignin untreated sample PhOH/100 C9 Lignin PhOH/100 C9 92.0

4.4

36.3

28.0

20.1

and hemicellulose are thought to be degraded to various compounds with low molecular weights as collected to be water-soluble portion shown in Table 2. Lignin is, thus, recovered mainly as the methanol-insoluble residue as well as methanolsoluble portion. Table 4 also shows the number of the phenolic hydroxyl groups (PhOH) upon 100 phenylpropane (C9) units of lignin for the methanol-insoluble residue. It is apparent that the methanol-insoluble residue has more phenolic hydroxyl groups (36.3 PhOH/100 C9) than the untreated sample (20.1 PhOH/100 C9). Previously, it was demonstrated with lignin model compounds that the condensed-type linkages, such as 5-5 linkage, were stable during supercritical water treatment, whereas the noncondensed-type ether linkages such as b-O-4 linkage, were easily cleaved by supercritical water hydrolysis [1]. After the cleavage of the noncondensed-type linkages, phenolic hydroxyl groups increased. This explains the reason for the higher phenolic hydroxyl content observed in methanol-insoluble residues and it suggests that many noncondensed-type linkages are cleaved and that the residues are rich in condensed-type linkages. From alkaline nitrobenzene oxidation analysis, the yield of oxidation products in untreated sample is around 23% upon lignin as a result of rather high condensedtype lignin in softwood, compared with hardwood [8]. However, the methanol-insoluble residue shows even smaller amount of nitrobenzene oxidation products, as shown in Fig. 2. These results were expected because nitrobenzene oxidation products are mainly derived from the degradation of the noncondensed-type lignin and the fact that most of these linkages are already cleaved under supercritical water treatment as mentioned above. It also suggests that methanol-insoluble residues are rich in condensed-type lignin.

Methanol-insoluble Untreated 0

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4 Conclusions The characteristics of Japanese cedar after fractionation with supercritical water treatment has been presented. The supercritical water treatment showed the potential as the rapid and nontoxic conversion process of Japanese cedar into organic acids and the possibility for many phenolic chemicals to be recovered. In addition, this line of study will be very useful to optimize further the recovery of useful chemicals from wood wastes of Japanese cedar. Acknowledgement  The authors are grateful for the financial support provided under the GCOE program, Kyoto University.

References 1. Ehara K, Saka S, Kawamoto H (2002) Characterization of the lignin-derived products from wood as treated in supercritical water. J Wood Sci 48:320–325 2. Varman M, Miyafuji H, Saka S (2010) Fractionation and characterization of oil palm (Elaeis guineensis) as treated by supercritical water. J Wood Sci 56:488–494 3. Whiting P, Favis BD, St-Germain FGT, Goring DAI (1981) Fractional separation of middle lamella and secondary wall tissue from spruce wood. J Wood Chem Technol 1:29–42 4. Lai YZ (1992) Determination of phenolic hydroxyl groups. In: Lin SY, Dence CW (eds) Methods in lignin chemistry. Springer, Berlin, pp 423–433 5. Katahira R, Nakatsubo F (2001) Determination of nitrobenzene oxidation products by GC and H-1-NMR spectroscopy using 5-iodovanillin as a new internal standard. J Wood Sci 47:378–382 6. Yoshida K, Miyafuji H, Saka S (2009) Effect of pressure on organic acids production from Japanese beech treated in supercritical water. J Wood Sci 55:203–208 7. Ralph J, Hatfield RD (1991) Pyrolysis–GC–MS characterization of forage materials. J Agric Food Chem 39:1426–1437 8. Chen CL (1992) Nitrobenzene and cupric oxide oxidations. In: Lin SY, Dence CW (eds) Methods in lignin chemistry. Springer, Berlin, pp 301–320

Two-Step Hydrolysis of Japanese Cedar as Treated by Semi-Flow Hot-Compressed Water with Acetic Acid Natthanon Phaiboonsilpa and Shiro Saka

Abstract  Japanese cedar (Cryptomeria japonica) as one of the softwoods was treated by two-step semi-flow hot-compressed water with 3.0  wt% acetic acid at 210 and 260°C/10  MPa/15  min, for the first and second stages, respectively. Totally, 85.0% of Japanese cedar could be solubilized into the hot-compressed water, while the rest of 15.0% remained as residue composed mainly of 11.7% lignin with 3.3% cellulose being incompletely hydrolyzed. In comparison with the two-step treatment of Japanese cedar without acetic acid addition reported previously, it was revealed that this current two-step treatment with acetic acid could be performed at lower temperatures with comparable yields of hydrolyzed products from hemicellulose and cellulose as well as lignin-derived products. The addition of acetic acid has shown a possibility to improve the hydrolysis and decomposition of wood cell wall components. However, due to decomposition reaction caused by acetic acid applied, the most appropriate optimum treatment conditions should be studied further. Keywords  Acetic acid • Hot-compressed water • Hydrolysis • Japanese cedar • Softwood

1 Introduction In our previous work, the two-step semi-flow hot-compressed water treatment of Japanese beech (Fagus crenata) as one of the hardwoods and Japanese cedar (Cryptomeria japonica) as one of the softwoods has been conducted [1–5]. It was reported that, at the first stage (230°C/10 MPa/15 min), amorphous hemicellulose and para-crystalline cellulose, whose crystalline structure is somewhat disordered,

N. Phaiboonsilpa and S. Saka (*) Graduate School of Energy Science, Kyoto University, Kyoto 606-8501, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_18, © Springer 2011

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were found to be selectively hydrolyzed into hot-compressed water as well as lignin being decomposed in part, while crystalline cellulose was hydrolyzed at the second stage (270–280°C/10 MPa/15–30 min). In addition to various hydrolyzed products recovered in water-soluble portion, their decomposed compounds were obtained. In such studies, a substantial production of decomposed compounds was, however, realized in the second stage due to its relatively high treatment temperature. These decomposed compounds could end up with loss of saccharides and inhibitory effect on the subsequent fermentation step, resulting in a lower yield of ethanol. As a consequence, the hot-compressed water treatment with acetic acid has become of interest as an alternative mean to improve the conversion yield of saccharides with minimizing the decomposed compounds by reducing the treatment temperatures. In addition, the presence of acetic acid in the treatment has no drawback effect to the subsequent process steps in our newly-developed ethanol production process via acetic acid fermentation and hydrogenolysis [5]. Softwoods are generally recognized as being much more resistant to hydrolysis than hardwoods or agricultural residues. This is due to the fact that softwoods have more rigid structure caused by their relatively high content of lignin and abundant condensed-type linkages in its structure. Also, the number of acetyl groups is lower in their hemicellulose than hardwoods, resulting in lesser extent of autohydrolysis to occur [6]. In this work, therefore, two-step hydrolysis of Japanese cedar as treated by semi-flow hot-compressed water with acetic acid has been investigated in order to study the effect of acetic acid for improving its hydrolysis.

2 Experimental Extractive-free wood flour of Japanese cedar (Cryptomeria japonica) was used [4]. The two-step semi-flow hot-compressed water treatment of Japanese cedar with 3.0 wt% acetic acid aqueous solution was performed at 210 and 260°C/10 MPa/15 min for the first and second stages of the treatment, respectively, to study the effect of acetic acid for hydrolysis. All the detailed experiments and analyses were conducted according to the procedures described in our papers [1, 2].

3 Results and Discussion 3.1 Decomposition of Major Cell Wall Components As treated by two-step semi-flow hot-compressed water with 3.0 wt% acetic acid at 210 and 260°C/10  MPa/15  min, various products from Japanese cedar were obtained. In the first stage, the hydrolyzed products were glucomanno-saccharides such as mannose, glucose and oligomeric glucomannan, galactose and acetic acid from

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the major softwood hemicellulose, O-acetyl-galactoglucomannan; xylo-saccharides such as xylose and xylo-oligosaccharides, arabinose, glucuronic acid and methanol from the minor softwood hemicellulose, arabino-4-O-methylglucuronoxylan; and coniferyl alcohol from guaiacyl unit of softwood lignin. In the second stage, on the other hand, those products from cellulose were cellosaccharides such as glucose, cello-oligosaccharides and fructose, as an isomerized product of glucose. In addition, dehydrated compounds (furfural, 5-hydroxymethylfurfural (5-HMF) and levoglucosan), fragmented compounds (glycolaldehyde, methylglyoxal and erythrose) and organic acids (lactic acid, glycolic acid and formic acid) were recovered in the water-soluble portion. Totally, 85.0% of Japanese cedar could be solubilized into the hot-compressed water, while the rest of 15.0% remained as residue composed mainly of 11.7% lignin with 3.3% cellulose being incompletely hydrolyzed.

3.2 Effect of Additional Acetic Acid on Hydrolysis Figure  1 shows a comparison of various product yields from Japanese cedar as treated by two-step semi-flow hot-compressed water with and without acetic acid. In comparison with the treatment without acetic acid addition performed at 230 and 270°C/10 MPa/15 min, it was revealed that, by adding 3 wt% acetic acid, the twostep treatment could be performed at lower temperatures (210 and 260°C/10 MPa/ 15  min) with comparable yields of hydrolyzed products from hemicellulose and cellulose, as well as, lignin-derived products. Slightly greater solubility of Japanese cedar into hot-compressed water was also perceived as seen from the lesser yield of residue. Although the treatment was performed at lower temperatures, more extensive decomposition reaction was realized in the treatment with the addition of acetic 100

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Fig. 1  Comparison of various product yields from Japanese cedar as treated by two-step semiflow hot-compressed water without acetic acid at 230 and 270°C/10  MPa/15 min and two-step semi-flow hot-compressed water with 3.0 wt% acetic acid at 210 and 260°C/10 MPa/15 min

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acid, as indicated by a drastic increase in yields of dehydrated and fragmented compounds as well as organic acids, which were collectively reported in terms of decomposed compounds. The concentration of acetic acid solution applied at 3.0 wt% in this present work might be too high, so that the excessive amount of acid played a significant role in the decomposition reaction rather than improvement of the hydrolysis. Moreover, because there still remained some content of incompletely hydrolyzed cellulose left in the residue and its amount was comparable to that from the treatment without acetic acid (See Fig. 1), it does not seem that acetic acid at higher concentrations would help to decompose cellulose more effectively. In other words, it may cause more extensive decomposition to the hydrolyzed products. The most appropriate optimum treatment conditions should be, therefore, studied further. Table 1 shows that, as a result of acetic acid addition, the hydrolyzed saccharides from Japanese cedar were found to be recovered more in monomeric forms, whereas those from the treatment without acetic acid were mainly in oligosaccharides. Monomeric and oligomeric glucose are hydrolyzed products derived mainly from the cellulose hydrolysis in the second stage, while the other saccharides are from hemicellulose in the first stage. For a particular case of fructose, it was generated from isomerization of monomeric glucose, so only its monomeric form was obtained. As the same observations were realized in all saccharides from both hemicellulose and cellulose, it is reasonable to infer that the additional acetic acid can help catalyze the hydrolysis of soluble oligosaccharides obtained in both stages.

Table  1  Comparison of various saccharides from Japanese cedar recovered in monomeric and oligomeric forms as treated by two-step semi-flow hot-compressed water with and without acetic acid addition Yield (wt%) Two-step treatment without Two-step treatment with 3.0 wt% Hydrolyzed acetic acid (230 and acetic acid (210 and saccharides 260°C/10 MPa/15 min) from hemicellulose 270°C/10 MPa/15 min) Monomeric Oligomeric Monomeric Oligomeric and cellulose Glucose 5.5 27.9 18.0 14.9 (16.5) (83.5) (54.7) (45.3) Mannose 0.5 7.7 1.4 5.9 (6.1) (93.9) (19.2) (80.8) Galactose 0.4 1.0 0.7 0.9 (28.6) (71.4) (43.8) (56.2) Xylose 1.2 4.5 3.7 3.2 (21.1) (78.9) (53.6) (46.4) Arabinose 0.4 0.4 0.6 0.1 (50.0) (50.0) (85.7) (14.3) Fructose 0.5 – 2.1 – The numbers in parentheses indicate the proportion of monomeric and oligomeric saccharides compared to their total recovery (%)

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4 Conclusions The addition of acetic acid has shown a possibility to improve the hydrolysis and decomposition of cell wall components in Japanese cedar (softwood) as treated by two-step semi-flow hot-compressed water. It was elucidated that the two-step treatment with 3.0 wt% acetic acid could be performed at 10–20°C lower temperatures (210 and 260°C/10  MPa/15  min) with comparable yields of hydrolyzed products from hemicellulose and cellulose, as well as, lignin-derived products, compared to the treatment without acetic acid addition performed at 230 and 270°C/10 MPa/15 min. In addition, the hydrolyzed products were found to be highly recovered as in monosaccharide forms, whereas those from the treatment without acetic acid were mainly in oligosaccharides. However, due to more decomposition reaction caused by acetic acid applied in this present work, the most appropriate optimum treatment conditions should be explored. This line of information could reveal a decomposition behavior of wood cell wall under hot-compressed water and would be very useful to develop the technology to utilize efficiently woods for biochemicals and biofuels. Acknowledgements  This work has been done under the NEDO project and under a partially financial support by the GCOE Program, Kyoto University.

References 1. Lu X, Yamauchi K, Phaiboonsilpa N, Saka S (2009) Two-step hydrolysis of Japanese beech as treated by semi-flow hot-compressed water. J Wood Sci 55:367–375 2. Phaiboonsilpa N, Yamauchi K, Lu X, Saka S (2010) Two-step hydrolysis of Japanese cedar as treated by semi-flow hot-compressed water. J Wood Sci 56:331–338 3. Phaiboonsilpa N, Lu X, Yamauchi K, Saka S (2010) Chemical conversion of lignocellulosics as treated by two-step hot-compressed water. In: Yao T (ed) Zero-Carbon Energy Kyoto 2009, Springer, Tokyo, pp 166–170 4. Phaiboonsilpa N, Lu X, Yamauchi K, Saka S (2009) Chemical conversion of lignocellulosics as treated by two-step semi-flow hot-compressed water. In: Proceedings of the world renewable energy congress 2009–Asia, pp 235–240 5. Saka S, Phaiboonsilpa N, Nakamura Y, Masuda S, Lu X, Yamauchi K, Miyafuji H, Kawamoto H (2009) Eco-ethanol production from lignocellulosics with hot-compressed water treatment followed by acetic acid fermentation and hydrogenolysis. In: Proceedings of the 17th European biomass conference and exhibition, pp 1952–1957 6. Galbe M, Zacchi G (2002) A review of the production of ethanol from softwoods. Appl Microbiol Biotechnol 59:618–628

Liquefaction Behaviors of Japanese Beech as Treated in Subcritical Phenol Gaurav Mishra and Shiro Saka

Abstract  The liquefaction of Japanese beech (Fagus crenata) was investigated as treated by subcritical phenol using a batch-type reaction vessel. As treated by 270–350°C/1.8–4.2 MPa/3–30 min, Japanese beech was fractionated into phenolsoluble portion and phenol-insoluble residue. It was found that, under the reaction condition of 270°C/1.8  MPa, lignin was mainly liquefied into phenol-soluble portion with some extent of hemicellulose and less cellulose being decomposed, whereas, at 350°C/4.2  MPa, a complete liquefaction of three main cell wall components was realized. The changes observed in liquefaction behaviors of the lignin, hemicellulose and cellulose as treated by subcritical phenol could reveal a prospect in various applications of the obtained liquefied products for biofuels and biochemicals. Keywords  Cellulose • Japanese beech • Lignin • Phenol • Subcritical fluid

1 Introduction The global climate change and the decline in the world oil production have put emphasis on the search for other potential alternatives to fossil fuels [1]. Biomass, which is carbon-neutral and environment-friendly, can be used as an alternative to the continuously-depleting fossil fuels. Sub/supercritical fluid science is one of such technologies which are used for the chemical conversion of the biomass into liquefied substances and other valuable products. Japanese beech has been tried and treated with various sub/ supercritical alcohols previously in our laboratory and has showed prospects to obtain

G. Mishra and S. Saka (*) Graduate School of Energy Science, Kyoto University, Kyoto 606-8501, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_19, © Springer 2011

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the liquid fuel [2]. It was reported in previous works that more than 90% of wood could be decomposed and liquefied when treated with methanol at 350°C/43  MPa. However, it took prolonged treatment time of about 30 min for almost all kinds of alcohols applied. Hence, it is expected that phenol due to its low dielectric constant can dissolve relatively high molecular weight products from cellulose, hemicellulose and lignin. The possibility of wood liquefaction with phenol is also investigated at subcritical conditions to achieve high conversion rate within shorter treatment times [3]. In this study, therefore, phenol was used as a solvent at its subcritical conditions in order to decompose and liquefy Japanese beech, and liquefaction behaviors under various subcritical phenol conditions were investigated.

2 Experimental Extractive-free wood flour of Japanese beech (Fagus crenata) with particles passed through the mesh size of 280  mm was used in the experiments. As described in Fig. 1, approximately 150 mg of the oven-dried wood flour and 4.9 ml of phenol were fed into a 5-ml reaction vessel made of Inconel-625. It was then subjected to phenol (Tc = 421.2°C, Pc = 6.13  MPa) treatment at subcritical condition (270– 350°C/1.8–4.2 MPa/3–30 min) by immersing it in molten salt bath preheated at a designated temperature. After the treatment, the reaction vessel was dipped in water bath to stop the reaction. The resulted reaction mixture was then filtered with 0.2-mm membrane, and phenol-soluble portion was separated from phenolinsoluble residue. The phenol-insoluble residue was then studied for its chemical composition. In addition, oven-dried phenol-insoluble residue was studied by X-ray diffractometry (RINT 2200V, Rigaku Denki). The apparent crystallinity was then estimated according to the method [4].

Beech wood 150 mg

Phenol 4.9 ml

Subcritical Phenol Treatment

Phenol-Soluble

Phenol-Insoluble

Sulfuric Acid Hydrolysis

Hydrolyzate

Residue

Fig. 1  Fractionation scheme of Japanese beech as treated in subcritical phenol

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3 Results and Discussion 3.1 Liquefaction Behaviors of Japanese Beech in Subcritical Phenol Figure 2 shows the changes in the phenol-insoluble residues of Japanese beech as treated by subcritical phenol at various conditions. Under the condition of 270°C/1.8 MPa, Japanese beech was liquefied to some extent with around 40% of phenol-insoluble residue left after the treatment for 30  min. At higher treatment temperatures of 310°C/3.1  MPa and 330°C/3.6  MPa, Japanese beech has been decomposed and liquefied more, around 20% and 3% of phenol-insoluble residues were left after the treatments for 30  min, respectively. On the other hand, at 350°C/4.2 MPa, more than 90% of wood was quickly decomposed and liquefied into the subcritical phenol within only 4 min of treatment time. After 30 min of treatment, only 1.1% of wood was left as phenol-insoluble residue.

3.2 Decomposition of Wood Cell Wall Components Figure 3 shows the chemical composition of the phenol-insoluble residues observed in Fig.  2, on cellulose, hemicellulose and lignin as treated at 270–350°C/1.8– 4.2 MPa/3–30 min. From the figure, the phenol-soluble portion can be seen as the area above the lignin. At 270°C/1.8 MPa, within a few minutes of treatment time,

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Fig.  3  Chemical composition of the phenol-insoluble residue of Japanese beech as treated by subcritical phenol at (a) 270°C/1.8  MPa, (b) 310°C/3.1  MPa, (c) 330°C/3.6  MPa and (d) 350°C/4.2 MPa

lignin was almost completely decomposed and liquefied into the phenol-soluble portion, whereas hemicellulose was solubilized to some extent. Cellulose was found to remain in the phenol-insoluble portion, which was not decomposed completely even with longer treatment time as shown in Fig.  3a. At 310°C/3.1  MPa (Fig. 3b), it can be seen that the hemicellulose portion has started to be decomposed and liquefied leaving only cellulose in the phenol-insoluble portion, at all treatment time. Upon the increase in treatment conditions to 330°C/3.6  MPa, the cellulose portion could be liquefied, as seen in Fig. 3c. Its complete liquefaction was realized after 20  min of treatment time. On the other hand, at 350°C/4.2  MPa (Fig.  3d), lignin, hemicellulose and cellulose were almost completely liquefied into subcritical phenol within 10 min. These different liquefaction behaviors of cellulose, hemicellulose and lignin in subcritical phenol showed a prospect for various applications of the obtained liquefied products. The 270°C/1.8  MPa treatment condition has suggested the almost complete solubilization of lignin just after 3 min treatment in phenol-soluble portion, without decomposing cellulose and hemicellulose. On the other hand, at 350°C/4.2 MPa, all the three cell wall components were decomposed effectively in all treatment times.

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3.3 X-Ray Diffractometry of Phenol-Insoluble Residues The amorphous portion in wood in general corresponds to the presence of hemicellulose and lignin, whereas the crystalline portion is represented by cellulose. The relative degree of crystallinity commonly termed as crystallinity-index or apparent crystallinity is used to show a relative intensity of crystalline portion compared to the amorphous one in wood. It was calculated by the following (1): I −I  ApparentCrystallinity =  002 am  × 100  I002 



(1)

where, I002 = Maximum intensity of 002 lattice diffraction at 2q = 22.5° Iam = Intensity of the diffraction in the same unit at 2q = 18° As seen from Fig. 4, the apparent crystallinity of the original wood was 37%. It was found to be increased to around 55–60% due to the partial removal of the amorphous portion, mainly lignin and some extent of hemicellulose, as treated at 270°C/1.8  MPa for 3  min and longer. At higher treatment temperatures, 310– 350°C/3.1–4.2 MPa, however, a significant change in the apparent crystallinity was realized to become around 70–80% in its crystallinity due to the complete removal of amorphous portion. Because of the complete liquefaction of three cell wall components in the treatment at 330–350°C/3.6–4.2 MPa, the apparent crystallinity of the phenol-insoluble residues were no longer seen after 10 min of treatment time. These observations from Fig.  4 are in good agreement with the results shown in Fig. 3. Hence, the relative increase in the crystalline portion from cellulose can be achieved on removal of hemicellulose and lignin. It is obviously seen that the treatment at 270–310°C/1.8–3.1 MPa suggests the appropriate treatment parameters for lignin removal and its solubilization, whereas the treatment at 330–350°C/3.6–4.2 MPa can be used as the treatment conditions for the complete solubilization of the wood cell wall.

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4 Conclusions The liquefaction of Japanese beech was studied in subcritical phenol at various conditions. As a result, under 270°C/1.8 MPa, lignin was decomposed and liquefied within a few minutes, with almost no hemicellulose and cellulose decomposition, suggesting that its treatment condition is appropriate for lignin solubilization, whereas the treatment at 330–350°C/3.6–4.2 MPa, all cell wall components were decomposed and solubilized, suggesting it to be good for the whole wood solubilization. These lines of evidence stipulates that separate treatment conditions can be used for selective liquefaction of lignin as well as whole wood liquefaction for various applications pertaining to lignin and whole wood respectively. Acknowledgement  The authors are grateful for the financial support provided under the GCOE program, Kyoto University.

References 1. Dongsheng W, Jiang H, Zhang K (2009) Supercritical fluids technology for clean biofuel production. Prog Nat Sci 19(3):273–284 2. Minami E, Yamazaki J, Saka S (2006) Liquefaction of beech wood in various supercritical alcohols. J Wood Sci 52:527–532 3. Lee SH, Ohkita T (2003) Rapid wood liquefaction in supercritical phenol. Wood Sci Technol 37(1):29–38 4. Segal L, Creely JJ, Martin AE Jr, Conrad C (1959) An empirical method for estimating the degree of crystallinity of native cellulose using the X-ray diffractometer. Text Res J 29:786–793

Glycerol to Value-Added Glycerol Carbonate in the Two-Step Non-Catalytic Supercritical Dimethyl Carbonate Method Zul Ilham and Shiro Saka

Abstract  A new non-catalytic two-step supercritical dimethyl carbonate method for fatty acid methyl esters (FAME) production has been previously established. The whole method consists of the hydrolysis of triglycerides by subcritical water (270°C/27 MPa/25 min) and subsequent esterification of hydrolyzed fatty acids by supercritical dimethyl carbonate (300°C/9  MPa/15 min) to FAME. High yield of FAME (96 wt%) and high quality of FAME in compliance with the international biodiesel standard could be resulted from this method. However, glycerol is still being produced as a by-product. Therefore, the potential to convert this glycerol to a value-added product, glycerol carbonate, has been studied. This reaction is, then, evaluated for its potential to be coupled with the two-step supercritical dimethyl carbonate by comparison with conversion of glycerol from other methods. Keywords  Biodiesel • Dimethyl carbonate • Fatty acid methyl esters • Glycerol carbonate • Supercritical method

1 Introduction Current environmental issues, fluctuating fuel price and energy security have led to an increase in worldwide biodiesel production. However, the current commercial biodiesel production method produces large surplus of unpurified glycerol as by-product, creating a glut in glycerol market. Without new applications, glycerol Z. Ilham University of Malaya, Kuala Lumbur 50603, Malaysia S. Saka (*) Graduate School of Energy Science, Kyoto University, Kyoto 606-8501, Japan e-mail: [email protected] Present address: Z. Ilham Graduate School of Energy Science, Kyoto University, Kyoto 606-8501, Japan T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_20, © Springer 2011

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price plunged and industrial plants are closing down. Therefore, it is superior if biodiesel production produces higher value-added by-products rather than glycerol. In line with this concept, one-step supercritical dimethyl carbonate method has been established as a new method for biodiesel production without producing glycerol [1]. In order to reduce the severe reaction condition in the one-step method, the two-step supercritical dimethyl carbonate method was introduced [2]. In this study, the glycerol from the two-step method was treated in supercritical dimethyl carbonate to obtain glycerol carbonate and evaluated for its effective production process.

2 Experimental Chemicals and various authentic compounds for standards were obtained from Nacalai Tesque Inc., all of which are of highest purity available. For glycerol from the two-step supercritical dimethyl carbonate method (hereinafter described as glycerol from the two-step method), glycerol from supercritical methanol method and unpurified glycerol from alkali-catalyzed method were studied just for comparison. Those were, then, treated in the batch-type supercritical biomass conversion system [3] to have a reaction at supercritical conditions with dimethyl carbonate (Tc:274.9°C/Pc:4.63  MPa) in a molar ratio of 1:10. All the experiments and analysis were conducted in compliance with the procedures described in our previous papers [1–3].

3 Results and Discussion 3.1 Glycerol Carbonate Formation in Supercritical Dimethyl Carbonate The two-step supercritical dimethyl carbonate method still yields glycerol as a by-product from triglycerides hydrolyzed with subcritical water to fatty acids [2]. In order to check the potential towards a 100% non-glycerol method, glycerol from this two-step method was treated in supercritical dimethyl carbonate at 300°C/12 MPa/15 min without any catalyst applied. When analyzed and compared to several authentic compounds, the resulted compound was found to be glycerol carbonate (4-hydroxymethyl-1,3-dioxolan-2-one), a value-added derivative of glycerol, as depicted in the chromatogram of Fig. 1. As depicted in Fig. 2, the glycerol from the two-step method was also treated in supercritical dimethyl carbonate at various reaction conditions. It could be seen that the best condition for high yield of glycerol carbonate is at the range of 280–300°C/9–12  MPa/15  min. Treatment in temperatures higher than 300°C as presented by the treatment at 350°C/12  MPa resulted in loss of yield due to the decomposition of glycerol carbonate, even in high-pressurized condition.

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The reaction scheme for the conversion could be expected to proceed in a manner described in Fig. 3. Dimethyl carbonate reacted with the primary OH group of glycerol, with higher reactivity than the secondary OH group, contributing to the formation of thermodynamically stable five-member cyclic carbonate. Methanol, also being formed from this reaction was removed by evaporation. This route is in agreement with several previous studies describing a similar method in a catalytic manner [4, 5].

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Fig. 4  Yield of glycerol carbonate from various glycerol resources treated in supercritical dimethyl carbonate at 300°C/12 MPa

3.2 Utilization of Glycerol Produced from Other Methods Glycerol from other methods (glycerol from supercritical methanol and unpurified glycerol from alkali-catalyzed methods [3]) were also treated in supercritical dimethyl carbonate at 300°C/12 MPa to check for the possible conversion of glycerol to glycerol carbonate. Comparison is presented in Fig. 4. As presented, glycerol from alkali-catalyzed method showed lower yield of glycerol carbonate than the ones produced by supercritical methods. This might be due to the amount of impurities in glycerol from alkali-catalyzed method and its complicated separation procedures. It is known that the glycerol from alkali-catalyzed method is not pure, contaminated with alkaline catalyst impurities such as sodium salts and soaps [6]. Therefore, utilization of pure glycerol from supercritical methods is better for higher conversion to glycerol carbonate.

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Fig. 5  Schematic diagram of the two-step supercritical dimethyl carbonate method coupled with the production of value-added glycerol carbonate

3.3 Two-Step Supercritical Dimethyl Carbonate to Produce Glycerol Carbonate Based on results presented beforehand, the two-step supercritical dimethyl carbonate is coupled with the treatment of the obtained glycerol in supercritical dimethyl carbonate (280–300°C/9–12 MPa/15 min) to achieve glycerol carbonate, as a valueadded by-product. Glycerol carbonate is a stable, colorless liquid currently used industrially as a solvent, additive and chemical intermediate [7]. The whole schematic diagram of the two-step method is presented in Fig. 5.

4 Conclusions The results presented in this study showed that glycerol could be converted to value-added glycerol carbonate in supercritical dimethyl carbonate (280– 300°C/9–12 MPa/15 min) without any catalyst applied. In addition, utilization of glycerol produced from supercritical methods showed higher conversion to glycerol carbonate due to its high purity. The two-step supercritical dimethyl carbonate method coupled with this conversion method is, therefore, a mild method, offering better prospect for scale-up application and produces value-added glycerol carbonate as a by-product. Acknowledgement  This study is partly funded by Japan Science and Technology Agency (JST) and Global-COE Program “Energy Science in the Age of Global Warming”, Kyoto University, supported by Ministry of Education, Culture, Sports, Science and Technology-Japan, for all of which the authors highly acknowledge.

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References 1. Ilham Z, Saka S (2009) Dimethyl carbonate as potential reactant in non-catalytic biodiesel production by supercritical method. Bioresour Technol 100:1793–1796 2. Ilham Z, Saka S (2010) Two-step supercritical dimethyl carbonate method for biodiesel production from Jatropha curcas oil. Bioresour Technol 101:2735–2740 3. Kusdiana D, Saka S (2004) Effects of water on biodiesel fuel production by supercritical methanol treatment. Bioresour Technol 91:289–295 4. Ochoa-Gomez JR, Gomez-Jimenez-Aberasturi O, Maestro-Madurga B, Pesquera-Rodriguez A, Ramirez-Lopez C, Lorenzo-Ibaretta L, Torrecilla-Soria J, Villaran-Velasco MC (2009) Synthesis of glycerol carbonate from glycerol and dimethyl carbonate transesterification: catalyst screening and reaction optimization. Appl Catal A Gen 366:315–324 5. Climent MJ, Corma A, Frutos PD, Iborra S, Noy M, Velty A, Concepcion P (2010) Chemicals from biomass: synthesis of glycerol carbonate by transesterification and carbonylation with urea with hydroxite catalyst. The role of acid-base pairs. J Catal 269:140–149 6. Hara M (2009) Environmentally benign production of biodiesel using heteregenous catalysts. Chem Sus Chem 2:129–135 7. Pagliaro M, Rossi M (2010) The future of glycerol. Royal Society of Chemistry, Cambridge

Prospect of Nipa Sap for Bioethanol Production Pramila Tamunaidu, Takahito Kakihira, Hitoshi Miyasaka, and Shiro Saka

Abstract  The current study was initiated to study the chemical composition of nipa sap and its prospect for bioethanol production. Chemical characterization of its sap yielded in sugars content of 14.5 wt%. In addition, the elemental analysis of nipa sap gave 0.5 wt% in ash content with Na, K and Cl being its main inorganic constituents. Batch fermentative assays were made using Saccharomyces cerevisiae to evaluate the fermentability of nipa sap in comparison to sugarcane sap. Almost 85% of total sugars in nipa sap were converted to ethanol within 20–28 h with nutrient supplementation. The fermentation trend of nipa sap was similar to sugarcane sap with a yield of 0.42 and 0.46 g ethanol/g sugars, respectively. Furthermore, nipa sap could be easily fermented without nutrient supplement which makes it an interesting feedstock for bioethanol production. Keywords  Bioethanol • Chemical characterization • Inorganic constituents • Nipa sap • Sugarcane sap

1 Introduction The increasing demand for food and fuel often positions energy crops in a conflict of interest. Yet, the global bioethanol supply is still produced mainly from sugar and starch feedstock. The production and use of ethanol from sugarcane in Brazil is the global model for bioethanol production, distribution and use [1]. Sugarcane in the form of juice and molasses which contain high levels of glucose, fructose and sucrose, are the easiest to be converted to ethanol [2]. Unlike sugarcane,

P. Tamunaidu and S. Saka (*) Graduate School of Energy Science, Kyoto University, Kyoto 606-8501, Japan e-mail: [email protected] T. Kakihira and H. Miyasaka Environmental Research Center, The Kansai Electric Power Co., Inc, Kyoto 619-0237, Japan T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_21, © Springer 2011

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the major carbohydrate in corn grain is starch. Common starchy materials used around the world for bioethanol production include potato and cassava. These crops are capable of producing valuable substrates for the production of renewable fuels and bio-products. However, production of fuel from these feedstock are limited as they are used as food for human or animal consumption. Besides common sugar and starch feedstock, palms have been a sugar-prospective from the ancient days. Main sugar yielding palms like palmyra palm (Borassus flabellifer), sugar palm (Arenga pinnata) and nipa palm (Nypa fructicans) are believed to produce more nutritious sugars than cane sugars [3]. As well as being used as edible sugars, interests on the production of alcohol fuel also emerged from these resources. Among these palms, Food and Agricultural Organization of the United Nations (FAO) described nipa palm as a non-threatened and underutilized palm in South Asia with certain exceptions in Bangladesh [4]. Nipa palm is a type of sugar yielding palm and the only thriving palm found in mangrove forests. Nipa produces an easily fermentable sap which is tapped from its inflorescence continuously for up to 100 years. Hamilton and Murphy reported that nipa palm is believed to produce 6,480–15,600 l of ethanol per hectare. This is twice compared to sugarcane which is 3,350–6,700 l [5]. The current study was initiated to explore the prospect of nipa sap for bioethanol production. Fermentative assays were made to evaluate nipa sap in comparison to sugarcane sap on the basis that each crop produces a functionally equivalent product. Further studies on the influence of inorganic constituents in their sap towards the ethanol productivity were made.

2 Experimental 2.1 Collection and Characterization The nipa sap used in this study was collected from Terengganu, Malaysia. On the other hand, the sugarcane sap was obtained from Miyakojima Island, Japan. Individual sugars and ethanol were quantified by high performance liquid chromatography (HPLC) LC-10A (Shimadzu, Japan) and Shodex SUGAR KS-801 column (Showa Denko, Japan) with water as the eluent. The ashes of the nipa sap samples by incineration at 600°C for 2 h were also determined. Elements were then detected through SEM–EDX analysis by scanning electron microscope JSM-5800 (JEOL Ltd., Japan) equipped with energy-dispersive X-ray instrument (EDAX Corp., USA), at an accelerating voltage of 20 kV.

2.2 Organism, Media and Culture Conditions The yeast Saccharomyces cerevisiae NBRC 0203 (NITE, Japan) was inoculated in Erlenmeyer flasks containing autoclaved medium of glucose 10 g/l, peptone 5 g/l,

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yeast extract 3 g/l and malt extract 3 g/l (Nacalai Tesque, Japan) and incubated in shaker at 120 rpm for 24 h at 28°C. Nutrient broth peptone 200 g/l, yeast extract 120 g/l and malt extract 120 g/l was also prepared to assist fermentation and was autoclaved at 121°C for 20 min prior to its use.

2.3 Batch Fermentations Fermentation experiments were conducted by batch in 50 ml shaking flasks using Saccharomyces cerevisiae. Fermentations were conducted on the same conditions among nipa sap, sugarcane sap and sucrose as a control with initial sugar content of 14.4 wt%. Duplicate experiments for the same samples were run parallel without nutrient supplementation. Fermentations were done in incubator at 28°C for a period of 28 h with samples taken aseptically at selective time periods.

3 Results and Discussion 3.1 Chemical Composition Table 1 shows the chemical composition of nipa and sugarcane saps on an average of three random samples. Nipa sap was rich in sugars and predominantly high in sucrose followed by glucose and fructose contents as observed in sugarcane saps. The ash content was slightly higher in nipa saps with 0.5 wt%.

3.2 Elemental Characterization The ash content described in Table  1 is lower in the sugarcane sap than nipa sap. Figure 1 shows a direct comparison of spectra obtained by energy-dispersive X-rays (EDX) analyses of the ash obtained from nipa and sugarcane sap, ­respectively. The main constituents were found to be Na, K and Cl in nipa saps, as it grows in

Table 1  Chemical composition of nipa and sugarcane saps Yield (wt%) Chemical composition Nipa sap Sugarcane sap Total chemical composition 15.0 15.0 Sugars 14.5 14.6 Sucrose 10.2 14.4 Glucose   2.3   0.1 Fructose   1.5   0.1 Others   0.5   0.0 Ash   0.5   0.4

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Energy (KeV) Fig. 1  Direct comparison of EDX spectra of inorganic constituents obtained as ash from nipa and sugarcane saps

swampy saline soils along seashores whereby elements like NaCl or KCl naturally exists in this habitat. Other minor constituents detected were Ca, Mg, Si, P and S. Conversely, major constituents detected in sugarcane saps were K, Mg, Ca, P and S.

3.3 Ethanolic Fermentation Figure 2 shows the obtained ethanolic fermentation of nipa sap, sugarcane sap and sucrose as a control. With nutrient supplementation, over 94% of sucrose available in all substrates was efficiently hydrolyzed to glucose and fructose to be further converted to ethanol. Similar trends in ethanol production were observed for all substrates, even though ethanol yield of pure sucrose was only 0.29 wt% compared to 0.42 and 0.46 wt% in nipa and sugarcane saps respectively. Detail fermentation results are shown in Table 2. Without nutrient supplementation, fermentation did occur for both nipa and sugarcane saps but the ethanol yields were as low as 0.35 and 0.15 wt% respectively. Conversely, significant difference was observed in the fermentation of pure sucrose, with only 0.01 wt% of ethanol yield was obtained after 28 h. Therefore in nipa and sugarcane saps, the microorganisms did not require any external nutrient for self growth or fermentation and probably utilized naturally available ­nutrients in the form of inorganic constituents from saps. The presence of these constituents may have supplemented the growth and metabolism of the microorganism and further assisted in the ethanolic fermentation process. Some nutrients such as Na, K, Mg and Ca are required in millimolar concentrations to satisfy ­cellular growth requirements to improve the ethanol fermentation and enhance ethanol productivity [6]. Therefore, this characteristic makes nipa sap a good alternative feedstock for ­bioethanol production.

Ethanol / Total sugars (wt/wt)

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0.5

Sugarcane sap 0.4

Nipa sap

0.3

Sucrose

0.2 0.1 0 0

10

20

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Fermentation time (h) Fig.  2  Ethanol yields from fermentation of nipa sap, sugarcane sap and sucrose under the same incubation conditions at 28°C with (filled symbols) and without (open symbols) nutrient supplement

Table 2  Ethanol productions from nipa sap, sugarcane sap and sucrose with and without supplementation of nutrients using Saccharomyces cerevisiae incubated at 28°C for 28 h Sucrose hydrolysis Ethanol yield Conversion efficiency (%) (wt/wt) efficiency (%) With nutrient Nipa sap 98.6 0.42 85.1 Sugarcane sap 98.7 0.46 89.2 Sucrose 94.7 0.29 56.8 Without nutrient Nipa sap Sugarcane sap Sucrose

92.0 56.0 20.5

0.35 0.15 0.01

67.6 28.4 1.4

4 Conclusions Nipa sap is mainly composed of sugars rich in sucrose, glucose and fructose with a total chemical composition of 15 wt%. The ash content was as low as 0.5 wt% with Na, K and Cl as its main inorganic constituents. Its habitual environment along the river estuaries and sea directly corresponds to the inorganic constituents ­available in the sap. Furthermore, it showed good ability to be fermented with or without nutrient supplementation with high yields of ethanol. These results ­indicated that inorganic constituents naturally available in nipa sap may have assisted the fermentation ­process. On the whole, nipa sap showed a good prospect for bioethanol production.

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Acknowledgements  We would like to thank Dr Naohiro Matsui and Dr Yasuyuki Okimori from The General Environmental Technos Co. Ltd, Osaka, for their generous contribution towards this research.

References 1. Nass L, Arraes P, Ellis D (2007) Biofuels in Brazil: an overview. Crop Sci 47:2228–2237 2. Badger P (2002) Ethanol from cellulose: a general review. In: Janick J, Whipkey A (eds) Reprinted from: Trends in new crops and new uses. ASHS Press, Alexandria, VA, pp 17–20 3. Dalibard C (1999) The potential of tapping palm trees for animal production. Livestock Feed Resources within Integrated Farming Systems 11:61–82 4. FAO – Food and Agriculture Organization of the United Nations (1998) Tropical palms. ­Non-wood forest products 10, 166 pp. Available online at http://www.fao.org/docrep/X0451E/ x0451e00.HTM. Accessed Jan 2009 5. Hamilton L, Murphy D (1988) Use and management of Nipa Palm (Nypa fruticans, Arecaceae): a review. Econ Bot 42:206–213 6. Robinett R, George H, Herber W (1995) Determination of inorganic cations in fermentation and cell culture media using cation-exchange liquid chromatography and conductivity detection. J Chromatogr A 718:319–327

Dissolution of Cerium Oxide in Sulfuric Acid Namil Um, Masao Miyake, and Tetsuji Hirato

Abstract  The dissolution behavior of CeO2 in sulfuric acid was examined using a batch reactor with various acid concentrations (8–14 M) at different temperatures (75–130°C). The dissolution of CeO2 was slow and it took more than 3 days to dissolve 4 mmol of a CeO2 powder completely in 100 mL of 12 M sulfuric acid at 90°C. The dissolution rate increased with increases in the temperature and the sulfuric acid concentration. The dissolution rate could be expressed by a shrinking sphere kinetics model. The variation of the dissolution rate constant with temperature obeyed the Arrhenius equation with the activation energy of 120 kJ mol−1. The reaction rate constant was a function of the acid concentration as C6.5. Keywords  Cerium oxide • Cerium polishing powder waste • Extraction • Hydrometallurgy • Sulfuric acid

1 Introduction Cerium oxide (CeO2) has been commonly used as an abrasive for glass polishing. It is also used in the chemical mechanical polishing process for intermetal dielectric planarization in the semiconductor industry [1–4]. Thus, a large quantity of polishing powder wastes (PPWs) containing CeO2, SiO2, Al2O3 and so on is generated from the industries. However, the PPWs do not undergo any recovery process, but they are just landfilled. Today, with the increasing demand of rare earth metals in the world, the recovery of rare earth metals from waste materials is required [5]. Therefore, it is important to develop a recovery process for the cerium oxide from PPWs. There are a few papers reporting the separation of CeO2 from PPWs using solvent extraction [6, 7], ion

N. Um, M. Miyake, and T. Hirato (*) Department of Energy Science and Technology, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 611-0011, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_22, © Springer 2011

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exchange [8] and electrochemical separation [9–11]. Despite these studies, the d­ issolution rate of CeO2 in acids has not been sufficiently studied. In this study, the dissolution kinetics of CeO2 in sulfuric acid was investigated. The effects of reaction temperature and acid concentration on the dissolution rate were examined.

2 Materials and Methods The CeO2 powder (Sigma Aldrich, Ltd.) with the particle size of below 5 mm was used. Dissolution experiments were carried out by putting 4  mmol of the CeO2 powder into 100  mL sulfuric acid solution in a batch glass reactor heated at a desired temperature. The solution was stirred by a magnetic stirrer at 650  rpm. After a given reaction time (4–168  h), the solution containing undissolved CeO2 was filtered. The amount of the remaining CeO2 was determined by measuring the weight of the residue after drying at 45°C for over 24 h. The parameters examined in this study were reaction temperature and acid concentration.

3 Results and Discussion The CeO2 powder was dissolved in 12 M sulfuric acid at 75, 90, 110 and 130°C to examine the effect of the reaction temperature on the dissolution rate (Fig.  1). The dissolution of CeO2 was quite slow even in such a high concentration acid. 1.0

Dissolution

0.8 130oC 110oC o 90 C 75oC

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At 75°C, only 20% of CeO2 dissolved after the reaction for a week. The dissolution rate increased as the temperature rose, and all the CeO2 could be dissolved in 8 h at 130°C. The effect of acid concentration on the dissolution rate was examined by using different sulfuric acid concentration of 8, 10, 12 and 14 M at 90°C. Figure 2 shows the results of these experiments. As expected, the dissolution rate increases with an increase in the sulfuric acid concentration. From the view point of thermodynamics, the overall dissolution process of CeO2 in an acid solution can be ascribed to the partial reduction of cerium(IV) to cerium(III) [12]: 4CeO 2(s) + 12H + (aq) = 4Ce 3 + (aq) + 6H 2 O(l) + O2(g)



(1)

All of the dissolution data obtained in this study could be expressed by a nonporous shrinking sphere kinetic model [13–15] described by (2). 1 − (Wt / W0 )1/3 = kt



(2)

where W0 and Wt represent the initial and residual amounts of CeO2 at time t, respectively, and k represents the apparent rate constant. This model assumes the surface reaction of CeO2 with the reactant, H+, in the solution, and a decrease in the surface area due to the decrease in the initial particle radius with time t. As shown in Figs. 3 and 4, 1 − (Wt /W0 )1/3 plotted against reaction time t are almost on a straight line for each experimental condition, indicating that the dissolution data reasonably followed the shrinking sphere model. The rate constants k (h−1), which were determined by the slopes of the strait lines in Figs.  3 and 4, are plotted against reciprocal of temperature (1/T) and logarithm of sulfuric acid ­concentration 1.0

Dissolution

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0.6 14 12 10 8

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M M M M

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Time /h Fig. 3  Plots of 1 − (Wt/W0)1/3 versus reaction time for different temperatures

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Time/h Fig. 4  Plots of 1 − (Wt/W0)

1/3

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(ln C) in Figs. 5 and 6, respectively. As shown in Fig. 5, the increase in the dissolution rate constant with increasing temperature obeyed the Arrhenius equation with the activation energy of 120 kJ mol−1. The relationship between the rate constant and the acid concentration can be expressed as k = k¢ C6.5 (Fig. 6). The large coefficient of 6.5 indicates a strong effect of acid concentration on the ­dissolution rate of CeO2.

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−1 −2

ln(k /h−1)

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Ea = 120 kJ mol−1

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)10−3/

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ln(k /h−1)

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n=6.5 −6

−7

−8 2.0

2.2

2.4

2.6

ln (C /M) Fig. 6  Effect of acid concentration on the dissolution rate constant

4 Conclusions The dissolution rate of CeO2 in sulfuric acid increased with increasing reaction temperature and acid concentration. The dissolution behavior could be described by the shrinking-sphere model with surface chemical reaction control. The activation

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energy of the dissolution was 120 kJ mol−1. The reaction rate constant could also be expressed as a function of acid concentration as k a C6.5.

References 1. Cook LM (1990) Non-Cryst Solids 120:152 2. Hoshino T, Kurata Y, Terasaki Y, Susa K (2001) Non-Cryst Solids 283:129–136 3. Sabia R, Stevens HJ, Varner JR (1999) Non-Cryst Solids 249:123–130 4. Ong NS, Venkatesh VC (1998) Mater Process Technol 83:261–266 5. Kosynkin VD, Arzgatkina EN, Ivanov EN, Chtoutsa MG, Grabko AI, Kardapolov AV, Sysina NA (2000) J Alloys Compd 303–304:421–425 6. Zhang Z, Li H, Guo F, Meng S, Li D (2008) Sep Purif Technol 63:348–352 7. Xinghua L, Xiaowei H, Zhaowu Z, Zhiqi L, Ying L (2009) J Rare Earths 27:119 8. Li X, Sun Y (2007) Hydrometallurgy 87:63–71 9. Vasudevan S, Sozhan G, Mohan S, Pushpavanam S (2005) Hydrometallurgy 76:115–121 10. Balaji S, Chung SJ, Thiruvenkatachari R, Moon IS (2007) Chem Eng J 126:51–57 11. Song X, Xu D, Zhang X, Shi X, Jiang N, Qiu G (2008) Trans Nonferrous Met Soc China 18:178–182 12. Preston JS, Cole PM, Preez AC, Fox MH, Fleming AM (1996) Hydrometallurgy 41:21–44 13. Abdel-Aal EA, Rashad MM (2004) Hydrometallurgy 74:189–194 14. Lee IH, Wang YJ, Chern JM (2005) J Hazard Mater B123:112–119 15. Ozdemir M, Cetisli H (2005) Hydrometallurgy 76:217–224

Utilization of Magnetic Field for Photocatalytic Decomposition of Organic Dye with ZnO Powders Supawan Joonwichien, Eiji Yamasue, Hideyuki Okumura, and Keiichi N. Ishihara

Abstract  The discovery of magnetic field effects (MFEs) on homogeneous chemical reactions have led to leads many reports on these effect, however a few have been applied on heterogeneous systems. The aim of this work, therefore, is to investigate the MFEs on photocatalytic decomposition of methylene blue (MB) using ZnO particles. The UV–VIS–NIR spectrometer was used to monitor the MB concentrations. The dependence of the reaction rate under UV irradiation on light intensity, the kept time between preparation of MB solution and before dispersing catalyst powders, so called settling duration, are studied. It is clear that the magnetic field enhances the decomposition rate of MB using ZnO. In case of zero magnetic field, the results show that the photocatalytic decomposition rate followed a first-order model. On the other hand, the decomposition rate of MB using ZnO did not follow first-order reaction under magnetic field. Furthermore, base on the results it is suggested that the condition of the MB solution is an important factor for MFEs on the photodegradation rate. Keywords  Magnetic field effect • Methylene blue • Photocatalytic decomposition • ZnO

1 Introduction Since 1976, the studies of MFEs on chemical reaction has been started. Most of the works published before 2000 were generally concerned the MFEs on photochemical reactions in homogeneous solutions [1]. There are, however, only several works that have focused the effect of magnetic field on a heterogeneous photocatalytic reaction.

S. Joonwichien (*), E. Yamasue, H. Okumura, and K.N. Ishihara Department of Socio-Environmental Energy Science, Graduate School of Energy Science, Kyoto University, Yoshida Honmachi, Sakyo-ku, Kyoto 606-8501, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_23, © Springer 2011

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Especially, TiO2 has gained much attention because of the strong photocatalytic abilities to purify pollutants in air and water under UV irradiation [2]. When the photocatalyst TiO2 absorbs the light at the wavelength less than 360 nm, it creates electron–hole pairs, promoting electrons to the conduction band and leaving positive holes in the valence band. The generated electron–hole pairs initiate a complex series of chemical reactions [3, 4]. Therefore, it is expected that the photocatalytic reaction might be accelerated or decelerated by external magnetic field. Furthermore, by considering electron transfer processes, it has been documented that magnetic field can affect the recombination process of cation and anion radicals [5]. In 1983, Kiwi reported the MFEs on the photosensitized electron transfer reaction in the presence of TiO2 and CdS loaded particles [6]. Also, there was a report on magnetic field influenced on the heterogeneous photocatalytic degradation of benzene by Pt/TiO2 [7]. Most of investigations of MFEs on heterogeneous photocatalytic reaction, so far studied only on TiO2 catalyst. Therefore, the aim of this work is to study the influence of applied magnetic field on the photodecomposition rate of organic dye compound using ZnO powders. ZnO has recently attracted a lot of attention because of its direct wide band gap of 3.37 eV at room temperature and the large exciton binding energy (~60 meV) [8], and its ability to decompose many chemical compounds [9] in both acidic and basic medium [10]. The decomposition of MB is used in order to assess the photocatalytic degradation reaction, the related mechanism will be clarified.

2 Experimental A photocatalyst, zinc oxide (purity 99.9%, surface area of 3.8 g/m2, less than 5 mm) was purchased from Wako Pure Chemical Ind. Ltd., and methylene blue (MB) powder was received from Nacalai Tesque, Inc, Kyoto, Japan. For the photocatalytic measurement, the decomposition of methylene blue was used in order to evaluate the photocatalytic reaction of ZnO powders. The specimens were irradiated by ultraviolet (UV-LED) lamp (OMRON, ZUV-L8V, Kyoto, Japan) with wavelength of 365 nm. The light is irradiated from the bottom and the distance from the UV light source to the specimen is approximately 10 mm. The experimental setup is schematically shown in Fig. 1. Moreover, the specimen container is sealed with cap in order to prevent evaporation. The experimental setup of a small reaction cell with the photocatalyst powders submerged in a 4 ml MB solution, were prepared as follows: The solid MB powder was dissolved into distilled water, and shaking for 5 min. Then, 0.005 g of catalyst powders was put into MB solution. After settling in the dark for another 5  min, UV light was irradiated to the specimen from the bottom. The UV–VIS–NIR spectrometer (Perkin–Elmer lambda 900) was used to monitor the MB concentrations. All the experiments were performed two or three times to confirm the reproducibility. Thus, all the values of photocatalytic degradation shown in this study are averaged. The results shown here are the normalized values after irradiation.

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Fig.  1  Schematic representation of experimental setup: (1) permanent magnet, (2) specimen, (3) UV-LED light source

3 Results 3.1 Influences of Light Intensity In this work, the experimental were carried out at the three light intensities corresponding to the three power levels for the lamp. The UV light intensity of 500, 600, 700 mW/cm2, under constant MB concentration of 0.08 mmol/L, the amount of ZnO powder is about 0.005  g. The influence of light intensity on the rate of photocatalytic decomposition has been examined. Figure  2 represents the photodegradation rate of MB using ZnO powders under different light intensities. In case of zero magnetic field, the light intensity effect showed a little in the photodecomposition rate. While, with magnetic field strength of 0.7 T, the reaction rate revealed the significant change and the reaction rate under the light intensity of 700 mW/cm2 was faster than 600, and 500 mW/cm2, respectively.

Fig. 2  The effect of light intensity on photocatalytic decomposition of MB using ZnO powder, (a) without magnetic field, (b) applying magnetic field

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3.2 Influences of Settling Duration In the experimental, two samples with different duration of time were prepared. Both have MB solution with same concentrations of 0.08 mmol/L. The first one is settled for only 5 min, while the second one is settled for 3 h. After that, catalyst powders were added to the MB solution. Hereafter, the kept time of MB solution after preparation and before dispersing catalyst power will be called the settling duration. Then, a light intensity of 600 mW/cm2 was applied to both samples and the pattern of UV irradiation in time is explained in Fig. 3. For settling duration of 5 min, the MFEs on photodecomposition take place. On the other hand, the experiment was performed under the same condition but MB solution was kept for 3 h before adding catalyst. The small MFEs on photodecomposition were observed at the settling duration of 3 h.

Fig. 3  The settling duration effect of MB solution using ZnO, (a) 5 min, (b) 3 h

4 Discussion The light intensity effect on photocatalytic decomposition of MB is discussed in terms of kinetics of reaction and MFEs. In order to find the degradation kinetics, the first-order reaction model is applied. The kinetic model is expressed by the equation:

ln (C0 / C) = kt,



(1)

where C0, C, t, and k are initial dye concentration, dye concentration at t (min), UV irradiation time, and rate constant (1/min), respectively. It revealed that the light intensity affected on photodecomposition rate. In case of a zero magnetic field (Fig. 2a), it is shown that the rate seems to be less affected and the decomposition rate was independent of light intensity. Moreover, the kinetics reaction rate follows the first-order

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reaction. In case of applied magnetic field of 0.7 T, the photodecomposition rate is extremely dependent on light intensities (Fig. 2b) and did not follow the first-order kinetic reaction. The dependencies of the reaction rates on the light intensity are reported to be attributed to the increased rate of the recombination of photogenerated electron–hole pairs [11]. One possibility is, an increase in the light intensity leads to more excitation and more electron–hole pair generation, along with increasing in OH species creation [12]. Therefore, magnetic field might be affects on hydroxyl radical and/or super oxide species. The settling time effect is also investigated in both cases of presence/absence magnetic field of 0.7 T. The result shows that MFEs become negligible when the same photodecomposition experiment is carried out after settlement of MB solution for 3 h. However, the detail of the mechanism is still not clear. Further investigation is needed to clarify.

5 Summary The photocatalytic decomposition of MB by ZnO particles under UV irradiation presence and absence magnetic field was investigated. When no magnetic field is applied, the decomposition rate become independent of light intensity, and light intensity seems to influence on the reaction rate of the first-order reaction. On the other hand, in the case of 0.7 T magnetic field, MFEs on the decomposition rate of MB were observed, and the reaction kinetics under magnetic field cannot be explained by the first order mechanism. Furthermore, the condition of MB solution is suggested as one important factor for MFEs on photodecomposition. The further study is needed to explain the full mechanism. Acknowledgement  This work was supported by Global Center of Excellence (GCOE) Program and Grant-in-Aid for Scientific Research (B) by MEXT, Japan.

References 1. Ulrich ES, Thomas U (1989) Magnetic field effects in chemical kinetics and related phenomena. Chem Rev 89:51–147 2. Karen JB, Richard DN, Carl AK, William AJ (1999) Investigation of the effects of controlled periodic illumination on the oxidation of gaseous trichloroethylene using a thin film of TiO2. Ind Eng Chem Res 38(3):892–896 3. Dindar B, Icli S (2001) Unusual photoreactivity of zinc oxide irradiated by concentrated sunlight. J Photochem Photobiol A Chem 140:263–268 4. Marto J, Sao MP, Trindade T, Labrincha JA (2009) Photocatalytic decoloration of orange II by ZnO active layers screen-printed on cereamic tiles. J Hazard Mater 163:36–42 5. Wakasa M, Suda S, Hayashi H, Ishii N, Okanp M (2004) Magnetic field effect on the photocatalytic reaction with ultrafine TiO2 particles. J Phys Chem B 108:11882–11885

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6. Kiwi J (1983) Magnetic field effects on photosensitized electron transfer reactions in the presence of titanium dioxide- and cadmium sulfide-loaded particles. J Phys Chem 87:2274–2276 7. Zhang W, Wang X, Fu X (2003) Magnetic field effect on photocatalytic degradation of benzene over Pt/TiO2. Chem Commun 17:2196–2197 8. Bretagon T, Lefebvre P, Valvin P, Gil B, Morhain C, Tang X (2006) Time resolved photoluminescence study of ZnO/(Zn, Mg)O quantum wells. J Cryst Growth 287:12–15 9. Yeber MC, Rodriguez J, Freer J (2000) Photocatalytic degradation of cellulose bleaching effluent by supported TiO2 and ZnO. J Chemosphere 41:1193–1197 10. Curri ML, Comparelli R, Cozzoli PD, Mascolo G, Agostiano A (2003) Colloidal oxide nanoparticles for the photocatalytic degradation of organic dye. Mater Sci Eng C 23:285–289 11. Upadhya S, Ollis DF (1997) Simple photocatalysis model for photoefficiency enhancement via controlled, periodic illumination. J Phys Chem B 101:2625–2631 12. Nagakura S, Hayashi H, Azumi T (1998) Dynamic spin chemistry. Kodansha and Wiley, Tokyo and NY

Hybrid Offshore Wind and Tidal Turbine Power System to Compensate for Fluctuation (HOTCF) Mohammad Lutfur Rahman, Shunsuke Oka, and Yasuyuki Shirai

Abstract  The hybrid system proposed in this study involves an offshore-wind turbine and a complementary tidal turbine that supplies grid power. The hybrid wind–tidal system consistently combines wind power and tidal power to guarantee the continuous availability of grid power. The power output from the offshore-wind is complemented by tidal power to maintain the grid power. The wind power is subject to short-term fluctuations, and the tidal power is used to compensate for these variations. This indicates that the tidal turbine must be able to increase production very quickly in order to supply grid power. Therefore, a performance analysis is necessary to determine the effective contributions from the tidal and wind turbine generators, and their contributions to the load system. Keywords  Flywheel • Hybrid system • Offshore-wind turbine • Tidal turbine

1 Introduction Offshore wind turbine models have played critical roles in understanding system performance and conducting grid integration studies. Likewise, the development of a tidal system converter model is a nontrivial problem, particularly for studying large scale ocean (tidal) power systems. The development and utilization of the various renewable energy sources represented by offshore-wind has become a strategic choice of energy problem solving. The offshore-wind turbine load is complicated

M.L. Rahman (*), S. Oka, and Y. Shirai Department of Energy Science and Technology, Graduate School of Energy Science, Kyoto University, Kyoto, Japan e-mail: [email protected]; [email protected]; [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_24, © Springer 2011

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because the load of the offshore-wind turbine fluctuates during the day. These fluctuations create imbalances in the power distribution that can affect the frequency and voltage of the power system. Laboratory scale experiments were carried out to show the feasibility of the system and to propose new control strategies using the bi-directional converter and MPPT (Maximum Power Point Tracking) grid connection converter [1, 2]. In the proposed system, in order to compensate for wind fluctuation, a tidal system is operated as a flywheel motor/generator system. In other words, when the power fluctuation exceeds a certain level, the tidal system works as a motor to store the excessive power as rotational energy. Conversely, when the wind power dips to a certain level, the tidal system works as a generator to complement it. The tidal turbine will help to balance the distribution of power in the power system. Figure 1a, b show a photo and conceptual image of the small laboratory-based hybrid power system model that designed and fabricated. The system has two types of generation, the tidal motor/generator and the offshore wind turbine generator. The tidal turbine (induction machine) can act as either a motor or generator, depending on the need. The tidal generator provides smooth output power, whereas the output power of a wind turbine depends on the wind velocity.

Fig. 1  (a) Photo of laboratory scale prototype model of hybrid offshore-wind and tidal turbine system with flywheel. (b) HOTT conceptual image

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2 Offshore Wind Turbine Generator Figure  2 shows an experimental model of the offshore-wind turbine generator system [2]. It consists of a coreless synchronous generator and a servo-motor. The offshore-wind turbine is simulated by the servo-motor. In this model system with the small servo-motor, the rated rotating speed is 2,500 rpm and the gear ratio is 10.5:1. In the real system, the wind turbine would have a slower rotating speed without the step-down gear. The rotating speed or the torque of the servo-motor is controlled by a computer. The electrical energy depends on the rpm (rotations per minute) of the servo-motor that rotates the coreless generator. Wind turbine generated AC power is converted to DC power with the 6-pulse diode rectifier. The parameters of the servo-motor and the coreless synchronous generator are listed in Tables 1 and 2, respectively.

Fig. 2  Offshore-wind turbine generator Table 1  Rating of main components (offshore-wind servo motor) Parameter Value Rated power 3.0 kW Rated voltage 200 V Rated frequency 60 Hz Rated speed 2,500 rpm Gear ratio 10.5:1 Table 2  Rating of main components (coreless synchronous generator) Parameter Value Rated power 1.5 kW Rated voltage 200 V Rated frequency 60 Hz Rated speed 200 rpm

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3 Tidal Turbine Figure 3 shows the experimental model of a tidal turbine induction generator/motor and a servo-motor [2]. The main concept in this project is to apply and control a bi-directional (two way) energy flow scheme, so that energy is injected into the offshore wind turbine or stored as kinetic energy from/to the tidal system (induction machine). Tidal turbine flywheel energy systems, in comparison with conventional batteries, present some interesting characteristics when used as an energy source to compensate for voltage sags and momentary power interruptions. The induction machine is used for bi-directional energy conversion from/to the tidal turbine. The servo-motor is used as an input model of tidal energy to the induction generator, which converts the mechanical energy into electrical energy. The induction machine can work as a motor by using the bi-directional IGBT converter and a one-way clutch. When the induction machine’s rotational speed is larger than that of the servo-motor, the servo-motor clutch turns to the off-state. The design parameters of the servo-motor and the induction machine are listed in Tables 3 and 4, respectively. A speed of 1,110 rpm is selected for the induction machine to store the rotational kinetic energy. In a real system, the tidal turbine rotational speed should be much lower than that of the servo-motor, and a step-up gear will be necessary.

Fig. 3  Tidal turbine generator/motor Table 3  Rating of main components (tidal servo motor) Parameter Value Rated power 1.5 kW Rated voltage 200 V Rated frequency 60 Hz Rated speed 2,500 rpm

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Table 4  Rating of main components (induction machine) Parameter Value Rated power 750 W Rated voltage 200 V Rated frequency 60 Hz Rated speed 1,110 rpm

Fig. 4  HOTCF circuit configuration

4 HOTCF System This paper presents an experimental study of how wind power can be complemented by tidal power. A conceptual framework is provided for a tidal power that produces almost stable power output without the intermittent fluctuations inherent when using wind power. The goal of this paper is intended to identify the best technological match between tidal as flywheel and offshore-wind turbines in order to build a new offshore-wind hybrid system [2]. This hybrid design makes system stable, flexible, reliable, durable and easy to scale. Figure 4 shows a schematic configuration of proposed wind & tidal hybrid generation system (HOTCF) model experimental output is simply rectified by a 6-pulse diode bridge to charge a DC capacitor. The tidal turbine induction generator/motor output is connected to the DC capacitor through a 6-pulse IGBT dual way converter.

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The DC link capacitor is connected to the commercial grid through a grid-connected inverter of single-phase and 3-wire. The grid-connected inverter is of a transformerless half-bridge type with a boost-up chopper circuit. The voltage-source inverter output current is controlled by PWM controller under the MPPT (Maximum Power Point Tracking) control. The MPPT control searches and keeps the DC link capacitor voltage which gives the maximum output power by controlling the output AC current. It gives the DC voltage perturbations of 4 V up and down (2 V/s) every 4 s and checks how to change the output power due to them, and then decides the DC-voltage reference at next stage to give more power. Several small controllers are implemented at both ends to provide the required performance to the system.

5 Experimental Results and Discussion In this section, one example of the hybrid operation is shown to demonstrate the availability of the proposed system. For the initial operating conditions, the offshore-wind only generates 0.2 kW. The tidal induction machine works in the motor

Fig. 5  Rotating speed of servo-motors and generators

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mode with a rotating speed of 1,190 rpm, while that of the tidal turbine servo-motor is 1,120 rpm (clutch is OFF). Figure 5 shows, the rotating speeds of the offshore-wind generator, tidal induction machine, and tidal servo-motor. The wind fluctuation was simulated by a step down change in the servo-motor rotating speed, as shown in the figure. The tidal system turned to the generator mode at 5  s to boost the tidal servo-motor speed higher than the rotating magnetic field speed (1,200  rpm) to compensate for the change in the wind generator output. The clutch turned to the ON-state and the servo-motor (tidal turbine) started to drive the induction machine. The instantaneous waves of the terminal voltage, current, and powers of the coreless generator (wind) are shown in Fig.  6. As the servo-motor (wind) speed fluctuated, the offshore wind generation power (P2, Fig. 6) decreased at 2.0 s and was shutdown at 8.3 s. To overcome this drawback, a hybrid energy system is needed to produce tidal power (P1, Fig. 7). As shown in Fig. 7, the tidal generation system was first used

Fig. 6  Voltage, current and output of offshore-wind generator system

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Fig. 7  Voltage, current and output of tidal generator system

as a flywheel for storing the rotational energy with small loss (P1 = −22 W). At 5 s, the induction machine changed from the motor to the generator mode and started to produce an active power of 100 W, and then 250 W at 7 s. Figure 8 shows DC link voltage Vdc, currents Idc1 and Idc2 from the bi-directional converter and diode-bridge, and Idc3 at the grid inverter. The powers, Pdc1 and Pdc2 from the tidal and wind generation systems, and Pdc3 at the power grid, are also shown. The power flows in the hybrid operation are clearly seen in the figure. While the wind generator output was decreasing, the tidal generator output was built up to compensate for it, and to recover the grid power to the initial value. Note that the MPPT control maintained the DC link capacitor voltage, which gave the maximum output power by controlling the output AC current during the operation. Figure 9 shows the voltage, current, and power at the AC side terminal of the grid connected inverter. In general, the grid power was kept stable according to the DC

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Fig. 8  Voltage, current and powers of DC side (color figure online)

side power, Pdc3. However, transient phenomena in the current and power were observed at the beginning of the tidal generation. The total coordination of the control system, including the MPPT control, should be investigated in the next study.

6 Conclusion The proposed HOTCF prototype is a HOTT system with an energy storage (flywheel) function. The control flexibility and the system stability can be much improved. A wind-tidal power generation system has a very high power-generating potential because of the abilities of wind and tidal resources to complement each other. This system is going to be economical in the future. Besides the cost, the

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Fig. 9  Experimental result of load side

environmental benefits are likely to facilitate the widespread use and acceptance of these systems. The performance of modular hybrid energy systems can be improved through the implementation of advanced control methods in bi-directional and MPPT system controllers. Optimum resource allocation, based on load demand and renewable resource forecasting, promises to significantly reduce the total operating cost of the system. The hybrid system method is considered to be one of the best techniques for converting tidal energy and wind energy into electricity.

References 1. Rahman ML, Oka S, Shirai Y (2010) DC connected hybrid offshore-wind and tidal turbine (HOTT) generation system. Springer, Academic Journals, pp 141–150 2. Rahman ML, Oka S, Shirai Y (2010) Hybrid power generation system using offshore-wind turbine and tidal turbine for power fluctuation compensation (HOT-PC). IEEE Trans Sustain Energy 1(2):92–98

Beam Stabilization by Using BPM in KU-FEL Yong-Woon Choi, Heishun Zen, Keiichi Ishida, Naoki Kimura, Satoshi Ueda, Kyohei Yoshida, Masato Takasaki, Ryota Kinjo, Mahmoud Bakr, Taro Sonobe, Kai Masuda, Toshiteru Kii, and Hideaki Ohgaki

Abstract  A Mid-Infrared Free Electron Laser (MIR-FEL) facility has been constructed for developing energy materials in Institute of Advanced Energy (IAE), Kyoto University. Since high brightness electron beams are crucial for the FELs, stabilization of the electron beam (beam energy, beam current, bunch spacing and beam trajectory) is very important for a stable FEL operation. For these reasons, the electron beam position which includes the electron beam energy information should be monitored precisely to realize the highly stable electron beam. We have been developing a feedforward and a feedback system using 4-pickup electrode type Beam Position Monitor (BPM) in Kyoto University FEL (KU-FEL) to generate a stable FEL light. A basic design of the BPM readout system has been completed and we have installed BPMs with accuracy of 10  mm for non-destructive measurement in the KU-FEL linear accelerator. BPM signals were observed successfully and a phase stabilized electron beam has been generated by a feedforward system. A feedback system using BPM to stabilize the beam position is under development. Keywords  Beam stabilization • BPM • Feedback control • Feedforward control • MIR-FEL

Y.-W. Choi (*), K. Ishida, N. Kimura, S. Ueda, K. Yoshida, M. Takasaki, R. Kinjo, M. Bakr, T. Sonobe, K. Masuda, T. Kii, and H. Ohgaki Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan e-mail: [email protected] H. Zen UVSOR, Institute for Molecular Science, Okazaki, Aichi, Japan T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_25, © Springer 2011

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1 Introduction Stabilization of an electron beam’s energy plays crucial role in a stable FEL ­operation. Energy variations can significantly affect transmission through beam line elements that transport the beam to the experimental area. Instability can result from various reasons in circumstances related to experimental room. Furthermore, FEL power becomes unstable because of these environmental problems. For this reason, we need to develop an energy feedback system using BPMs. In our facility, the instability of the electron beam energy is occurred owing to the fluctuation of the body temperature of the thermionic RF gun, the surface temperature of the cathode because of a back-bombardment effect [1], the surface temperature of accelerator tube, the high-electric noise by the klystron and so on. As mentioned before, this instability brings about the instability of FEL power as shown in Fig. 1. The power stability during 30 min. is about 14% (RMS). So, we have to improve the power ­stability for FEL applications.

2 Experiment A new BPM system was introduced to the KU-FEL [2] linac in Kyoto University in 2009. The six BPMs were installed at each position. The structure of the BPM is 4-pickup electrodes type as shown in the left side of Fig. 2. The diameter of the electrode of the BPM is 15 mm. When an electron beam passes through a beam duct, a signal whose amplitude is determined by the beam charge and the beam position of the electron beam is induced by each electrode of the BPM as shown in the left side of Fig. 2. Then a beam position is calculated in aspect of the left, the right, the top and the bottom by processing these

Output Power [a.u.]

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Voltage Charge

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SMA Connector Electron Beam Vacuum Chamber

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Fig. 2  4-pickup electrodes type BPM

#1 #2

Low E section High E section

#3

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# BPM number

#6

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#5

Fig. 3  Schematic drawing BPMs in KU-FEL

signals. This pickup electrode type BPM is superior in high frequency property. In  ­addition, a technique to measure a bunch length of the electron beam by measuring the strength ratio of the high-frequency component of the evoked signal is also suggested [3]. The basic frequency of the signal evoked by the electron bunch is the same as the electron beam repetition frequency (2,856 MHz) shown in the right side of Fig. 2. The locations of the each BPM installed in KU-FEL are shown in Fig. 3. The BPM #1 and #3 are used to measure the RF phase of the electron beam to keep the bunch spacing in constant by controlling phase of the input RF signal fed into the RF-gun as well as the accelerator tube. The BPM #1 and #2 in the low energy section and BPM #3 and #4 in the high energy section are used to measure electron beam position owing to the electron beam energy in each section. To stabilize the beam energy in each section, we will install feedback loops by controlling input RF powers fed into the RF gun and the accelerator tube, respectively. The BPM #5 and #6 are used to put electron beam at the center in the undulator by controlling bending magnets and steering magnets. The functions of each BPM are summarized in the Table 1. The speed of the feedback control system would be a few seconds to stabilize a long time fluctuation in KU-FEL. To ensure this feedback system, we will use a software feedback system developed by the LabView package.

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Table 1  Functions of each BPM in KU-FEL BPM # Control object Measured object 1 and 2 Energy (low energy Position section) 3 and 4 Energy (high energy section) Position 5 and 6 1 and 3 5

Position RF phase (low energy section, high energy section) Bunch length

Position RF phase Bunch length

Control knob RF power fed into RF gun RF power fed into accelerator tube Steering magnets Phase of RF power fed into RF gun and accelerator tube Quadrupole strengths

Klystron No.2 TV2019B6 PFN1

Signal Generator 2856MHz

RF Gun ~200W Klystron No.2 PV-3030A1 PFN2

BPM 1 Accelerator Tube

~500W Out Phase Test Detector

Function Generator

PC

BPM 3

Ref Oscillo -scope

Phase Test Out Detector Ref

Fig. 4  Schematic diagram of RF system

3 Results We succeeded in measuring a change of electron bunch phase by using a high ­frequency signal output from BPM #1. We also succeeded in keeping a fixed electron bunch phase using a voltage control type high speed phase shifter as shown in Fig. 4. Each phase shifter in this figure is used to compensate the bunch phase shift measured by BPM #1 and #3, respectively. We need an electron beam with constant RF phase for FEL lasing. As shown in the Fig. 5a, the bunch phase was not constant during the macro-pulse because a time varying RF power was fed into the RF gun to compensate the time varying beam loading which was induced by backbombardment effect in thermionic RF gun. After installation of feedforward phase control system indicated as red part in the Fig. 4, we can improve the phase shift

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from 16° to less than 2° during the macro pulse as shown in the Fig.  5b. A preliminary­ result of the beam position readout measurement by using BPM #3 is shown in Fig. 6a on the horizontal axis for showing in the aspect of the left and right side in the beam duct and Fig. 6b on the vertical axis for showing in the aspect of the top and bottom side in the beam duct. These plots show the response owing to the steering magnet currents. The signals from the pickup electrode were calculated by different-over-sum processing. We observed non-linear response in this measurement because of the strong quadrupole field located near-by BPM #3. The basic design of the beam position feedback system by using BPM is shown in Fig.  7. Our overall system is as like the below. The signals from BPMs will be clipped by NIM clipping modules and be AD converted with CAMAC ADC system connected with PC (LabView). And then, we can achieve the beam stabilization as adjusting power supply of bending magnet or steering magnet through feedback loop by using LabView feedback library.

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Fig. 6  BPM #3 signal owing to steering magnet current

Steering Magnet Current [A]

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Signal processing NIM

CAMAC

Clipping Module (8 ch)

Charge ADC (16 ch)

BPM

Power supply

Feedback Fig. 7  Beam feedback system by using BPM

4 Conclusions We have installed six BPMs designed by KEK-ATF group with an accuracy of 10 mm for non-destructive measurement in KU-FEL linear accelerator. And then, we could measure a change of electron bunch phase and compensate electron bunch by using BPM #1 for additional acceleration in accelerator tube. The signal observation by using BPM #3 was complimented successfully. As a result the RF phase drift during the macro pulse was successfully improved from 16° to less than 2°. A new feedback system using BPMs to stabilize the beam position of each part, the beam energy in the low energy and the high energy section has been designed to improve stability of KU-FEL. The linac energy can be determined by measuring the beam position displacement at a location with a large dispersion. Information of electron beam energy derived from the electron beam positions may include noise, a part of which is caused by an electric noise induced by high-power klystrons. This problem can be reduced by integrating the BPM signals, beam currents and cathode surface temperature of RF-gun.

References 1. McKee CB et al (1990) NIM A296:716–719 2. Ohgaki H et al (2008) Lasing at 12 mm mid-infrared free-electron laser in Kyoto University. Jpn J Appl Phys 47:8091–8094 3. Kuroda R et al (2004) Jpn J Appl Phys 43(No. 11A):7747–7752

Analysis of Transient Response of RF Gun Cavity Due to Back-Bombardment Effect in KU-FEL Mahmoud Bakr, Heishun Zen, Kyohei Yoshida, Satoshi Ueda, Masato Takasaki, Keiichi Ishida, Naoki Kimura, Ryota Kinjo, Yong-Woon Choi, Taro Sonobe, Toshiteru Kii, Kai Masuda, and Hideaki Ohgaki

Abstract  Thermionic RF guns have advantageous features, such as compactness and high brightness of output beam, against electrostatic guns because of their high acceleration fields. For these reasons, thermionic RF gun has been ­chosen as electrons injector for Kyoto University free electron laser facility. The most critical issue of the thermionic RF gun is the transient cathode heating due to the electron back-bombardment when the gun is used as a driver linac of an MIR–FEL oscillator, which requires macropulse duration of more than 5 ms and bunch charge of more than 20  pC. Under the condition, the transient cathode heating results in rapid increase of beam current and rapid decrease of beam energy during a macropulse. Several important parameters, such as cathode temperature, current density of the cathode surface, are difficult to be measured during the experiment. A numerical simulation is the best way to expect the behaviour of such parameters. Numerical calculations were carried out to evaluate the cathode temperature and current density during the macropulse, by a simulation code which was developed at Kyoto University. The code simultaneously solves two differential equations; the differential equation of the equivalent circuit of the RF gun and one dimensional thermal equation of the thermionic cathode which includes the heat input from  back-bombardment electrons. The results of transient response of the RF cavity due to the back-bombardment effect are presented with conclusions. Keywords  Back-bombardment • FEL • Numerical simulation • RF cavity • Thermionic cathode

M. Bakr (*), K. Yoshida, S. Ueda, M. Takasaki, K. Ishida, N. Kimura, R. Kinjo Y.-W. Choi, T. Sonobe, T. Kii, K. Masuda, and H. Ohgaki Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan e-mail: [email protected] H. Zen UVSOR, Institute for Molecular Science, Okazaki, Aichi 444-8585, Japan T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_26, © Springer 2011

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1 Introduction Thermionic RF guns are quite attractive because of its simple configuration with no high voltage stage, in addition, the beam emittance is possibly low and the bunch length can be compressed to have sufficient peak current to drive free electron laser (FEL) [1]. Due to the economical, compact configuration and high brightness of output beam, thermionic RF gun has been chosen to drive Kyoto University free electron laser (KU-FEL) facility. However, currently there are not so many linac devices with thermionic RF guns are used in FEL applications; because of the great challenges against the back-bombardment (BB) affect, while, strongly restrains further development as the electron source. Some methods to mitigate BB effect [2–4] have been invented without so much success. The mechanism of the BB effect in thermionic RF gun can be simply explained as follows: because the cavity fields oscillate in time, electrons that are emitted late in the RF period does not have the chance to cross the cavity before the accelerating field reverses its direction. A number of these electrons are accelerated back towards the cathode. If these electrons hit the cathode, its kinetic energy transfers to the cathode material and heat it up. Under normal operating conditions, some BB electrons are necessary for the proper operation of the gun. However, since the heating is presented only during the macropulse, the temperature of the cathode is increased during the macropulse. The increasing of cathode temperature causes a ramp in the macropulse current; as one can see from Fig. 1a. Due to the increases of the beam current the beam loading increases, as a result the cavity voltage decreases, and consequently, the beam energy decreases. To reduce the heat transferred by the BB electrons, an external transverse magnetic field has been commonly applied on the cathode surface. However, even with the applying of the transverse magnetic filed the beam current increases and beam energy decreases during the macropulse when the macropulse length is longer than 2  ms and the output beam current is higher than 200 mA [5], which are not sufficient for various

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FEL applications. In KU-FEL facility two methods to compensate the energy beam decrease due to the BB electrons were conducted; by controlling input RF power and frequency cavity detuning, more details can be found in [6]. KU-FEL thermionic RF is S-band RF gun having 4.5-cell, side-coupled cavities with a thermionic cathode at the first half cell, which is driven by 10 MW RF power, to provide electron beam up to 10  MeV. Figure  1b shows schematic for KU-FEL thermionic RF gun with LaB6 cathode. In this paper, we proposed a developed numerical simulation code to study the transient cathode heating problem­due to the BB effect in thermionic RF gun. And determine the change in the cathode temperature and current density during the macropulse.

2 Analysis Method The BB effect depends on the cavity voltage in the RF gun and current density at the cathode surface. We performed a transient analysis in the thermionic RF gun taking into account the time evolution of the beam loading depends on the cavity voltage and the cathode current density by using an equivalent circuit for RF cavity model and a thermal conduction model. The beam loading is calculated from the cavity voltage by solving the equivalent RF gun circuit and the current density was calculated from the thermal conduction in the cathode by solving one dimensional thermal diffusion equation. The energy distribution and the total power from the BB electrons were determined by simulation codes taking into account the stopping range and deposited heat from the BB electrons inside the cathode.

2.1 Analysis of the RF Cavity Response The interaction between an RF resonant cavity and an electron beam can be represented by equivalent circuit [7]. In this circuit, the RF power source is expressed by a source Ig, the RF gun is expressed by LCG resonant circuit, and the beam loading is expressed as beam admittance part Yb, which can be divided in the circuit into real part beam conductance Gb and imaginary part beam susceptance Bb. The Gb and Bb depend on the current density on the thermionic cathode surface Jc and the acceleration voltage of the cavity Vc. The circuit constants (external ­conductance Gex, cavity inductance Lc, cavity capacitance Cc, and cavity conductance Gc) are given as: Cc =

2 π f0 1 1 , Lc = , Gc = , Gex = b Gc 2 π f0 ( R / Q ) ( R / Q) Q0 ( R / Q )

(1)

where f0 denotes the resonant frequency of the RF resonant cavity, Q0 the unloaded quality factor, (R/Q) the (R/Q)-factor of the cavity, and the coupling coefficient b of the input waveguide to the cavity. The source current Ig is described as

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Ig = (8GexPin)1/2. The beam admittance Yb is defined as Yb = Ib/Vc, where Ib denotes the beam loading (induced) current.

2.2 Analysis of the Cathode Current Density In this analysis, following three assumptions are considered; I- Radiative heat emission occurs only on the surface of the cathode. II- Heat input to the cathode is only from the cathode heater and BB electrons. III- Heat flows only on the beam axis in a macropulse. Under these consedrations, the heat transfer in the cathode is given by one dimensional thermal diffusion equation as:



CrV

∂T ( z, t ) ∂ 2 T ( z, t ) =l + Qb ( z, t ,) ∂t ∂z 2

(2)

where C (J/kg/K) denotes the specific heat capacity, r (kg/m3) the mass density, V (m3) the cathode ­volume, l (W/m/K) the thermal conductivity, t the time, z the depth of cathode from the surface, T(z, t) the cathode temperature and Qb(z, t) the heat input due to the BB electrons. It is impossible analytically solve (2), since the heat input is time dependent and not uniform. Thus the cathode is divided into 20,000 thin disks, and ­difference method is used to calculate the heat transfer. The time evolution of the temperature is calculated in each disks of the cathode. The range, R of electrons inside a material is useful for evaluation of effects associated with penetration of electrons in the material, such as BB electrons. The range R of electrons in the energy region 0.3  keV–30  MeV for the absorbers of atomic number 6–92 has been found to be expressed by a single semiempirical equation TIO of the form [8]. R=

a3 ( γ − 1)  a1  ln(1 + a2 ( γ − 1) −   ρ a2 1 + a4 ( γ − 1)a5 

(3)

where, R (m) is the stopping range of the electrons, g is the incident kinetic energy in the units of the rest energy of the electron, a1,2,….5 are parameters depend on the atomic number and atomic weight of the absorber material; parameters, definitions and more details can be found in ref [9]. It well known that the stopping power of the particles inside material can be defined as the decreases of the particles energy relative to the change the stopping range as dE/dR, hence the stopping power can be determined.

3 Results and Discussion The simulation was carried out in the same conditions of normal operation at KU-FEL of initial cathode temperature, input RF power, frequency, cavity voltage and electron beam energy. The cathode material is a single crystal of LaB6 with

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radius and thickness 1 and 2 mm respectively, density r = 4,720 kg/m3, specific heat C = 122 J/kg/K, l = 147 W/m/K. RF gun parameters which are used in the calculations are listed in Table 1.

3.1 RF Cavity Response The beam conductance and beam susceptance in the equivalent circuit depend on the cavity voltage and the current density on the cathode surface, due to that the beam conductance and susceptance depend on energy consumed by the electron beam and riding RF phase of the beam. The beam conductance and beam susceptance of the electron beam were calculated at different cavity voltage and cathode current density by using particle simulation code KUBLAI [10]; the results are depicted at Fig.  2. As shown in Fig.  2, the beam admittance increases when the current density on the cathode surface increases. And the partial differential coefficients of the beam conductance and of the beam susceptance with respect to the current density are positive and negative, respectively. Table 1  Parameters of the RF gun which have been used in the numerical simulation code Resonant frequency (MHz) 2,856 Coupling coefficient (b) 2.79 Q value 12,500 R/Q (W) 980 Accelerating mode p Cathode material LaB6 Initial cathode temperature (°C) 1,562

Fig.  2  (a) Beam conductance and (b) susceptance as a function of the current density Jc with different cavity voltage, which are derived by numerical simulations (KUBLAI code)

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3.2 Analysis of the Cathode Current Density In order to evaluate the effect of BB electrons on the time evolution of the cathode temperature, at first the energy distribution and deposited heat of BB electrons were calculated at different current density and cavity voltage by using the particle ­simulation code PARMELA [11]. Figure 3a, shows the deposited heat at different BB electron beam energies. However, Fig.  3b shows the energy distribution of the BB electrons inside the cathode material at different cavity voltages and at fixed current density 50 A/cm2 as an example. As shown in Fig.  3, BB electrons hitting the cathode surface have energy distribution­. The energy distribution and the total power of BB strongly depends on the cavity voltage and current density on the cathode surface. One can see from Fig. 3a that with increase the electrons energy the depth of the deposited energy

Fig. 3  (a) Energy deposition of BB electrons in cathode material at different electron beam energies, (b) energy distribution of BB electrons at 50  A/cm2, current density at different cavity voltage derived by PARMELA

Fig.  4  (a) The range and stopping power of BB electrons in cathode material calculated by using TIO equation, (b) the change of the cathode temperature and current density during the macropulse (color figure online)

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increase, and the maximum deposition occurred just before electrons stop. Moreover, the total power of BB electrons gets higher when a thermionic RF gun is operated with the condition of higher current density or higher cavity voltage as shown in Fig. 3b. Then, the range and stopping power of BB electrons inside the cathode material were determined by the results from the PARMELA code and (3). Figure 4a shows the range and stopping power as a function of BB electrons energy. Finally, to analyze the BB effect and determine the change in the cathode ­temperature and current density during the macropulse, a numerical simulation code  has been developed at Institute of Advanced Energy, Kyoto University. The code calculates the transition state of a thermionic RF gun from fed RF pulse shape and initial cathode temperature. In this simulation, a differential equation of equivalent circuit of a thermionic RF gun and a differential equation of heat transfer in a thermionic cathode are simultaneously and numerically solved. Figure 4b shows the results of the simulation code which describe the change in the cathode temperature and current density. The change in the cathode temperature and current density were obtained from the time evolution. Demonstration for the simulation code is required to compare the simulation and experimental results.

4 Conclusions We have developed a numerical simulation code for deep understanding of the back-bombardment effect. The code starts with calculate the energy distribution and the total power of the back-bombardment electrons by using PARMELA, and beam admittance and beam loading by KUBLAI code. Then the range and the stopping power of the BB electrons were calculated to determine the deposited heat by using semiempirical equation TIO. Finally, the change in the cathode temperature and current density were determined by the solving of the differential equation of thermionic RF gun equivalent circuit and a one dimensional thermal diffusion equation of heat transfer in a thermionic cathode. As next step demonstration is required to realize the simulation code. Acknowledgment  The author wish to thank the GCOE program, Graduate School of Energy Science in the age of Global Warming Kyoto University, for financial support.

References 1. Yokoyama M et al (2001) Nucl Instr Meth A475:38 2. MacKee CB, Maday JMJ (1990) Nucl Instr Meth A296:716 3. Kii T et al (2007) AIP Conf Proc 879:248–251 4. Zen H et al (2009) IEEE Trans Nucl Sci 56(3):1487 5. Oda F et al (2001) Nucl Instr Meth Phys Res A A475:583–587

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6. Zen H (2009) Doctor Thesis, Institute of Advanced Energy, Kyoto University 7. Cheo BR et al (1991) IEEE Trans Elec Dev 38(10):2264–2274 8. Tabata T et al (1972) Nucl Instr Meth 103:85–91 9. Bakr M et al (2010) Green energy and technology, part III, 202–210 10. Masuda K (1998) Doctor Thesis, Institute of Advanced Energy, Kyoto University 11. Young LM, James H (2002) Billen: LA-UR-96-1835

Part III

Advanced Nuclear Energy Research

(i)

Contributed Papers

Nuclear Characteristics Transition Depend on the Position of External Source on the Accelerator-Driven System Using KUCA and FFAG Accelerator Jae-Yong Lim, Cheolho Pyeon, Tsuyoshi Misawa, and Ken Nakajima

Abstract  By combining the Fixed Field Alternating Gradient (FFAG) ­accelerator with the A-core of the Kyoto University Critical Assembly (KUCA), ­accelerator-driven system (ADS) experiments are accomplished successfully using (p, n) reaction on the tungsten target which is located at core outside. In order to increase spallation neutron injection into this core, numerical analyses are performed by adapting the neutron or proton beam duct and the change of tungsten target position. When the tungsten target is moved into core closely, the neutron multiplication calculated by the ratio of neutrons by fission and supplied neutrons from external source increases gradually in inverse proportion to the distance between core and target. When this distance is changed from 70 to 20 cm, 430% reaction rate gain is observed relatively by comparing with 115In(n, n¢)115mIn reaction. Keywords  Accelerator-driven system • Fixed field alternating gradient ­accelerator • Kyoto University Critical Assembly • MCNPX Monte-Carlo code • Neutron multiplication

1 Introduction As a new option of nuclear power plant, a concept of accelerator-driven system (ADS) suggested and has studied for transmutation of high level radioactive material, energy production and neutron source applications [1, 2]. Since an additional neutron supplied from several types of external source could be maintained neutron multiplication in a subcritical core, this concept possesses the highest reliability in

J.-Y. Lim (*), C. Pyeon, T. Misawa, and K. Nakajima Nuclear Engineering Science Division, Research Reactor Institute, Kyoto University, Kumatori, Sennan, Osaka 590-0494, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_27, © Springer 2011

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safety aspect by cutting the supply of neutrons off. Hence the characteristics of external source become the main issues for developing ADS concept. In order to verify the characteristics of typical ADS, the experimental investigations were ­performed in several facilities globally such as MASURCA reactor in France, YALINA facilities in Belarus, and Kyoto University Critical Assembly (KUCA) in Japan [3–5]. At a new ADS with the FFAG accelerator, on 4th March 2009, the high-energy neutrons generated by spallation reactions with 100 MeV proton beams, which was contrasted with other external sources such as deuterium–deuterium (D–D), ­deuterium–tritium (D–T) and Californium in previous mentioned experiments, were successfully injected into a solid-moderated and -reflected core (A-core) in thermal neutron field of KUCA. Unfortunately, the quality of injected proton beams was not satisfied the target goal of FFAG accelerator and the tungsten target for producing spallation neutrons was located at core outside. Especially, a few pA proton beam intensity was not effective for irradiation experiments and was not a sufficient external­neutron source for maintaining neutron flux inside critical assembly. In this study, we investigated to increase the amount of injected neutrons into core by numerical simulations and two approaches were proposed. Firstly, the flight path of spallation neutrons was modified like a beam tube in order to collimate it at active core region. Second changes was that a tungsten target was moved close to core for focusing dispersed neutrons by scattering after spallation at target.

2 ADS Experiments and Calculation Methods 2.1 Configuration of ADS Experiments The FFAG accelerator complex consists of four main facilities: (1) Ion source, (2) Ion-beta, (3) Booster and (4) Main. Ion source produces protons with 100 keV energy and produced protons accelerates up to 2.5  MeV through second facility named with Ion-beta. Using Booster located inside of Main ring, protons with 2.5  MeV and 1.17  m injected radius varies that of 20  MeV energy and 1.65  m extracted radius. Finally, Main ring can make 20 MeV proton supplied by Booster accelerate up to maximum 150 MeV proton energy, 1 mA average beam current and 120 Hz pulse repetition rate [6]. In order to transport accelerated protons from Main ring of FFAG accelerator to KUCA, various magnets for bending and focusing were used, because the distance by ~30 m exists between Innovation Research Laboratory (IRL) and KUCA which are set up FFAG accelerator and KUCA A-core respectively. KUCA building is divided four sections and each sections contains comprises solid-moderated and -reflected type-A and -B cores, a water-moderated and -reflected type-C core and Cockcroft–Walton-type pulsed neutron generator. For  the proton

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injection experiment, the solid-moderated and -reflected type-A core was combined with a FFAG accelerator at opposite surface of Cockcroft–Walton-type accelerator. The A-core (A3/8″P36EU(3)) was composed of a combination of 23 fuel rods that were loaded on the grid plate. The materials used in the critical assemblies were always in the form of a rectangular parallelepiped, normally 2″ square with thickness ranging between 1/16″ and 2″. The upper and lower parts of the fuel region were polyethylene reflector layers of more than 50  cm length. The fuel rod, a 93% enriched uranium–aluminum (U–Al) alloy, consisted of 36 cells of polyethylene plates 1/8″ and 1/4″ thick, and a U–Al plate 1/16″ thick and 2″ square. The functional height of the core was approximately 40 cm [5].

2.2 Calculation Methods For the simulations considered with charged particle transport and neutron ­transport in same time, a Monte-Carlo transport code – MCNPX 2.5.0 was employed [7]. In  order to consider the interaction between high energy proton/neutron above 20  MeV and materials, two libraries were compared; the newest ENDF library series – ENDF/B-VI.6 with LAHET physics model and JENDLE High Energy File (JENDL/HE) which was released in 2007 to respond the requirements of reaction data in high energy range up to several GeV [8]. Using these calculation tools, reactivity and Indium irradiation measurement about reference core were accomplished. The difference of reactivity showed only 23 ± 18 pcm using 20 million histories. Thermal neutron flux distribution was estimated through the horizontal measurement of 115In(n, g)116m1In reaction rates by the activation analysis of an indium wire with 1.0 mm diameter. The In wire was set in an aluminum guide tube, from the tungsten target to the center of fuel region, at the center position of fuel assembly axially. In these static ­experiments conducted at 5th march, 2009, the subcritical system was made by the full insertion of C1, C2 and C3 rods as the same as the kinetic experiments, and the subcriticality was experimentally deduced to be 0.76%Dk/k. The neutron source information for a MCNPX calculation was not taken a isotopic source option and also calculated directly by describing tungsten target with 80  mm j and 10  mm thickness and mono-direction proton beam with 100 MeV energy. Since the effect of the reactivity­ is not negligible, the In wire was included from tallies taken in the indium wire setting region. The radial reaction distribution by Indium reaction rate in fixed source calculation also showed a good agreement as shown in Fig. 1. Even though ENDF/B-VI.6 library which contains cross-section data about only less 20 MeV of neutron energy was adapted, it was confirmed that the difference between two libraries was negligible because KUCA A-core made well thermalized neutron spectrum by a lot of polyethylene moderators. However, JENDL/HE was selected for a detailed description about high-energy in this study.

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3 Numerical Analyses for the Core Configuration Changes 3.1 Effect of the Beam Steaming Duct The core and neutron source configuration of FFAG/KUCA ADS is slightly different from that of general ADS concept. For the one of main objective of ADS – the transmutation of high-level waste such as minor actinides as well as the effective utilization of generated neutron, a neutron spallation target located at the center of subcriticality system. However, for the safety aspects, KUCA A-core could not be allowed to insert a additional heavy metal inside core. Therefore, the introduction of a neutron guide is requisite for effectively directing the high-energy neutrons generated from the tungsten target to the core center. The neutron guide, which is very similar to the neutron shield and the beam duct, (1) is composed of several shielding materials, including lead (Pb), iron (Fe), boron (B), polyethylene, the beam duct, and a special fuel assembly with a void. For other core configurations are presented here: a core without the neutron guide (Fig. 2a Case 1); a core including only Streaming Void (SV) in the fuel region (Fig. 2b Case 2); a core with the neutron guide with large window including SV (Fig. 2c Case 3), and a core with the neutron guide substituted from Iron to Lead including SV (Fig. 2d Case 4). In case of last two core configurations, based on reference core, the effect of large window on core surface and the reflecting effect by material changes were investigated respectively. By the modification of core configuration, the criticality mass should be changed and different fuel assemblies with the numerals 12, 14 and 20 correspond to fuel plates in the partial assembly in order to compensate changed reactivity.

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The calculated 115In(n, n¢)115mIn reaction rate distribution in arbitrary units for Cases 1 through 4 showed a 27% increase in neutron yield between Cases 1 and 2 in the fuel region as shown in Fig. 3. Only the presence of steaming void inside of core is different between these two core geometries. Since a streaming effect of favoring the external neutron to reach the center of fuel region, the increase in the neutron yield between reaction rate distributions in Cases 1 and 2 demonstrated consequently. Depending on the existence of neutron guide or not, the neutron yield at core region showed extremely differences between reference core and Case 2.

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This comparison proves that the introduction of neutron guide is effective as a meaning of improving the neutron yield in the core region. A few % of the neutron yield changes was observed between reference core and Case 3 and 4 which were modified slightly with reference core for wide windows and neutron reflector with high atomic number respectively.

3.2 Effect of the Tungsten Target Position As another way to increase neutron supply in the fuel region, the tungsten target which could produce spallation neutrons by interacted with protons moved three closer positions with fuel regions and core characteristics caused by these changes were compared with each other. The tungsten target in the reference case is located at 71.3 cm apart from core center and at the proton beam line which is under the vacuum condition. For assuming a real experiments condition, the tungsten target inside proton beam line was eliminated and it moved three different neutron guide assemblies which were installed at KUCA-A core for the construction of neutron/ proton guide. These neutron guide assemblies consisted of iron cubes, polyethylene and polyethylene with boron for the neutron reflection and shielding and three aluminum cube cans were located at the center of assembly for securing the vacant space as a neutron/proton flight path. The tungsten target eliminated from the ­proton beam line was inserted in the aluminum can which is located at the straight position with the direction of proton beam. Three selected positions of tungsten

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target were fourth, sixth and eighth guide assemblies and they distanced 19.9, 31.1 and 42.2 cm from core center respectively. By different tungsten target positions, the transitions of neutron multiplication were measured using the two kinds of In wire reaction rate. For the thermal neutron distribution, 115In(n, g)116m1In reaction was used and the fast neutron distribution was tallied by 115In(n, n¢)115mIn reaction with 0.32 MeV threshold energy. When the tungsten target was moved from original position (71.3 cm from core center) to 42.2, 31.1 and 19.9 cm, the amount of protons injected at the tungsten target decreased 50.4%, 29.4%, 12.9% respectively by scattering with the flange of proton beam line and the structure materials such as aluminum, polyethylene and so on. Moreover, we confirmed that the amount of spallation neutron with fast neutron energy also decreased by comparing the peak as shown in the left area of Fig. 4. However, the indium reaction rate by fast neutrons at fuel region increased extremely because of higher neutron efficiency caused by closer distance between the target and fuel region even though the produced spallation neutrons were reduced up to 12.9%. Figure  5 shows the 115In(n, g)116m1In reaction rate distribution depend on the change of tungsten target position. Because this reaction rate caused by the interaction with thermal neutrons, the reaction rate peak was not observed like Fig. 4 but the similar phenomenon that the closest target was more effective was ascertained in the fuel region and the thermal peak region.

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4 Conclusions The numerical analyses were carried out about ADS experiments using KUCA with FFAG accelerator to evaluate the increase of spallation neutron amount into ­subcritical core. Two modifications were suggested for this purpose and the calculation results by MCNPX 2.5.0 Monte-Carlo code with JENDL/HE revealed the following. Firstly, it was confirmed that the collimation effect by adapting a neutron/proton guide tube was very effective by reducing spallation neutron scattering out. Second approach – the change of tungsten target showed that closer target was more profitable for the neutron multiplication even though the protons after leaving from beam tube could not reached to spallation target effectively. The present experiments and numerical analyses could be expected to contribute to determining experiment plans and further researches related with subcriticality measurement and the nuclear design in ADS at KUCA. Acknowledgement  This work was partly supported by a “Energy Science in the Age of Global Warming” of Global Center of Excellence (G-COE) program (J-051) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. A part of this study was supported by the Grant-in-Aid for Scientific Research form MEXT from Japan.

References 1. Salvatores M (1999) Accelerator driven systems (ADS), physics principles and specificities. J Phys IV 9(7):17–33 2. Rubbia C et al (1995) Conceptual design of a fast neutron operated high power energy amplifier, CERN/AT/95-44 (ET), CERN

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3. Millebaud A et  al (2007) Prompt multiplication factor measurements in subcritical systems: from MUSE experiment to a demonstration ADS. Prog Nucl Energy 49(2):142–160 4. Kiyavitskaya H (2007) Yalina subcritical facility to investigate neutronics of ADS: Yalinathermal benchmark, Yalina-booster benchmark. In: IAEA technical meeting, Rome, Italy, 12–16 Nov 5. Pyeon CH et  al (2008) Static and kinetic experiments on accelerator-driven system with 14  MeV neutrons in Kyoto University Critical Assembly. J Nucl Sci Technol 45(11): 1171–1182 6. Yonemura Y et al (2007) Development of RF acceleration system for 150 MeV FFAG accelerator. Nucl Instr Methods Phys Res Sect A 576:294–300 7. Pelowitz DB (2005) MCNPX user’s manual, version 2.5.0. Los Alamos National Laboratory 8. Sasa T et  al (2008) Continuous energy cross section library for MCNP/MCNPX based on JENDL high energy file 2007 -FXJH7-. Japan Atomic Energy Agency

High Performance Computing of MHD Turbulent Flows with High-Pr Heat Transfer Yoshinobu Yamamoto and Tomoaki Kunugi

Abstract  The large-scale direct numerical simulations (DNS) of a MagnetoHydro-Dynamics (MHD) turbulent heat transfer have been executed on the massively parallel processing supercomputer systems. The maximum computational speed was measured up 4.35 Tflops and the sufficiently parallelization efficiency was achieved. It has been confirmed that present DNSs have the sufficient spatial resolution. Definitely, we can succeed to establish the DNS data of MHD heat transfer under the high-Reynolds (Re = 14,000) and high-Prandlt number conditions (Pr = 25). Keywords  DNS • High-Pr • High-Re • MHD • Parallel computing

1 Introduction FLiBe which is the molten salt mixture of LiF and BeF is one of the coolant candidates in the first wall and blanket of the fusion reactors, and has several ­advantages which are little Magneto-Hydro-Dynamics (MHD) pressure loss, good chemical stability, less solubility of tritium and so on. In the contrast, the low thermal­diffusivity and high viscosity are the key issues of the FLiBe utilization as a coolant [1]. Moreover, the development of MHD turbulence model with high accuracy is highly demanded to predict the MHD pressure loss and the heat transfer for the fusion reactor designs. A direct numerical simulation (DNS) of turbulent flows is one of the most powerful methods to understand turbulent structures and heat transfer. Molten salt fluids such as FLiBe are the higher Pr fluids (Pr = n/a:Prandtl number = 20–40, n is

Y. Yamamoto (*) and T. Kunugi Department of Nuclear Engineering, Kyoto University, Sakyo Yoshida, Kyoto 611-0011, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_28, © Springer 2011

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the kinetic viscosity, a is the thermal diffusivity), however the previous DNS studies have conducted at the only lower Pr condition. Therefore, MHD turbulent heat transfer on higher Pr fluids hasn’t been understood well. Furthermore, a problem of DNS studies limited to lower-Re (:= Ub2h/n is the bulk Reynolds number, Ub is the bulk mean velocity, h is the channel height) and -Pr conditions would be depended on the computational resources limitation.

2 Numerical Methods 2.1 Basic Equations and Boundary Condition The target flow is the incompressible MHD turbulent flows at the low magnetic Reynolds number (Rem = Ub2h/h,h is the magnetic diffusivity) with passive scalar transport. The objective flow geometry and coordinate system are shown in Fig. 1. Basic equations of the present DNS were the continuity equation (1), the momentum equations (2) with the electric field described using the electrical potential approach [2], Poisson equation (3) of the electrical potential, and the energy equation (4), respectively.



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Non-slip and periodic conditions were imposed for boundary conditions of ­velocity and the constant temperature at top and bottom boundaries (qtop > qbed, qtop: top wall temperature, qbed: Bottom wall temperature), and the periodic conditions were imposed for a passive scalar field. Total electric current in the flow domain was kept zero and the boundary condition of the electric potential was non-conducting condition at all walls and the periodic condition imposed on the horizontal directions.

2.2 Numerical Procedures The spectral method is used to compute the spatial discretization in the stream (x) and spanwise (z) directions. Nonlinear terms were computed with 1.5 times finger grids in horizontal (x and z) directions to remove the aliasing errors (Padding method). The derivative in the wall normal (y) direction is computed by a secondorder finite difference scheme at the staggered grid arrangement. Time integration method is 3rd-order Runge–Kutta scheme for the convection terms, Crank–Nicolson scheme for the viscous terms and Euler Implicit scheme for the Pressure terms, respectively. The Helmholtz equation for the viscous (diffusion) terms and the Poisson equations of the pressure and the electrical potential are solved by a TriDagonal Matrix Algorithm, TDMA in Fourier space.

2.3 Parallelization In this DNS study, the Message Passing Interface (MPI) was adapted for a distributed memory parallel programing tool. Domain decomposition in the y direction was used in order to calculate 2D-FFTs for the horizontal directions (x,y). Before performing the TDAM along the y direction, we need to transpose the data form the

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domain decomposition along the y axis to the one along the z axis. In this process, we implemented the following two methods to treat the discontinuous data transfer. (a) Data transposition by MPI_ISEND/IRECIVE with the derivative data type ­discontinuous data. (b) Data transposition by remote memory access (RMA), called one-sided ­communication with the packed 1D continuous data. Since the global memory function [3] for the data transfer by the MPI library was implemented in the SX-9 [4], faster data transfer by used MPI_PUT based on RMA, called one-sided communication, can be expected. To avoid the excessively concentration of the data communication between the specified rank and others, scheduling [5] the multi-stages internode data communications via the single-stage crossbar network, were implemented as shown in Fig. 2. To reduce the data communication traffics, a hybrid parallelization by MPI and Microtasking was implemented. Furthermore, to obtain the sufficient parallelization efficiency, the phase shift method, in which a convolutional sum is obtained for a shifted grid system as well as for the original grid system, was adapted instead by the padding method. Using the phase shift method, we can reduce the load of memory copy in the padding method.

2.4 Numerical Condition Numerical conditions of DNS for 2-D fully-developed turbulent channel flows imposed wall-normal magnetic field, were tabulated in Table 1, where super-script + denotes the nondimensional quantities normalized by the friction velocity and the kinematic viscosity. In the computations, thermal properties of the FLiBe

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3 Results and Discussions 3.1 Performance of Parallel Computation Using the program information of MPI/SX [3], computational speed has been measured for the calculation of 10 time steps. This computational speed taken in initialization was included from the measurement. The corresponding numbers of nodes (CPUs) taken up in the SX-9 were 4(64), 8(128) and 16(256) and 4 microtasking process per node were adapted in all cases. Parallelization method (b) with the scheduling inter-node communication was applied in case of the SX-9, because the performance loss in the parallelization method (a) was sensible when using 4 nodes (64CPUs). Figure  3a shows the elapsed time normalized by one when using 4 node (64CPUs) and Fig.  3b shows the computational speed [Tflops] as a function of numbers of CPUs in case of the Padding algorithm. Using parallelization method (b) with the scheduling inter-node communication and the padding algorithm,

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computational speed was 4.11 Tflops, parallel efficiency was 74.3%, parallelization rate was 0.99865, and vector operation ratio was 99.71%, when using 16 nodes (256CPUS) of the SX-9. Elapsed time per one time step was about 3.1 [s] when using 4nodes (64CPUs). On the other hands, computational speed in case of the phase shift algorithm was measured up 4.35 Tflops when using 16nodes (256CPUs). The phase-shift algorithm was about 6% faster than the Padding algorithm in this study. This effective computational speed was corresponded to 17% of the theoretical peak performance.

3.2 Validation of Grid Resolution Figure 4a, b shows the one-dimensional streamwise pre-multiplied energy spectra of streamwise velocity and temperature near channel center in Ha = 0, where kx is the streamwise wave number and energy spectra were normalized by Kolmogorov scale (:lK) and energy dissipation rate (:e ) and Batchelor scale (:lB) and temperature energy dissipation rate (:eqq ). In the high-accuracy DNS, it was pointed out [6] that more than 1 kx lK and kx lB of grid resolution were required for velocity and temperature field, respectively. In this DNS, it can be confirmed that more than 1 kx lK and kx lB of grid resolution were resolved for velocity and temperature field, respectively. Figure 5a, b shows the instantaneous streamwise turbulent velocity and turbulent temperature in Ha = 0. In the high-Pr temperature field, fine small turbulent fluctuations were observed compared with the velocity field. Eventually, we had established the high-accuracy DNS database of MHD heat transfer in the high-Re and -Pr.

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(k x lK )2E uu/( lK /t K )

a

0.03

0

0

0.5

k x lK

1

0.2

0.1

0

0

0.5

1

k x lB

Fig. 4  1D-streamwise pre-multiplied energy spectra near channel center in Ha=0, (a) streamwise velocity and (b) temperature

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Fig. 5  Visualization in, Ha = 0, near channel center, top view, (a) streamwise turbulent velocity, −0.1 (black)
b

5 4

q

k

3

Ha=0 Ha=20 Ha=28

20

Ha=0 Ha=20 Ha=28

+ rms

a

2

10

1 0

100

101 y+

102

0

100

101 y+

102

Fig. 6  MHD effects on turbulent kinetic energy and temperature intensity, (a) Turbulent kinetic energy, (b) temperature intensity

3.3 MHD Effects Figure 6a, b shows the turbulent kinetic energy and temperature intensity profiles in all cases. Due to the MHD effects, the turbulent kinetic energy was decreased,

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but the temperature intensity was increased. This indicates that turbulent effects might be more dominant on the MHD heat transfer, despite the turbulent motion was restricted by the MHD effects.

4 Conclusion In this study, DNSs of MHD heat transfer under the high-Re (= 14,000) and high-Pr (Pr = 25) condition have been executed on the massively parallel processing supercomputer systems. Present DNS achieved that the maximum grid number was O(109) and the maximum computational speed was measured up 4.35 Tflops. It has been confirmed that present DNSs have the sufficient spatial resolution. Definitely, we can succeed to establish the DNS database of the MHD turbulent flows with high-Pr heat transfer. Acknowledgement  Present DNSs were conducted by using the SX-9 supercomputer system at the Cyber Science Center, Tohoku University. This study was supported by the Global COE program “Energy Science in the Age of Global Warming” and a Grant-in-aid for Young Scientists (B), KAKENHI (21760156) MEXT, Japan.

References 1. Sagara A, Motojima O, Watanabe K, Imagawa S, Yamanishi H, Mitarai O, Sato T, Chikaraishi H, FFHR Group (1995) Blanket and divertor design for force free helical reactor (FFHR). Fusion Eng Des 29 III:51 2. Simomura Y (1991) Large eddy simulation of magnethydrodynamic turbulent channel flows under a uniform magnetic field. Phys Fluids A 3:3098 3. NEC Corporation (2008) SUPER-UX – MPI/SX RIYO NO TEBIKI (SUPER-UX –MPI/SX Operation Guide) 4. SX-9 supercomputer at Tohoku University’s Cyber Science Center (2008). http://www.isc. tohoku.ac.jp/HTML/ 5. Kobayashi H et  al (2006) Performance evaluation of the SX-7 supercomputer on HPCC (in Japanese). http://www.ss.isc.tohoku.ac.jp/refer/senac.html#2006_1 6. Eswaran V, Pope SB (1988) An examination of forcing in direct numerical simulations of turbulence. Comput Fluids 16:258–278

Comparison Between Microbubble Drag Reduction and Viscoelastic Drag Reduction Li-Fang Jiao, Tomoaki Kunugi, and Feng-Chen Li

Abstract  Both microbubble drag reduction (MBDR) and viscoelastic drag reduction (VEDR) are an effective method to reduce the frictional resistance of a turbulent boundary layer. The synergy effect of the combination of MBDR and VEDR puts more significance on the observation of the surfactant microbubbly flow. This paper reviews the main influencing factors, the velocity distribution, turbulence characters and possible mechanisms of MBDR flows and VEDR flows based on the past experimental and numerical researches on these fields. Then, through comparing the above context, some possible hypotheses and observe methods about the combination of MBDR and VEDR are proposed. Keywords  Drag reduction • Microbubble • Synergy effect • Viscoelastic fluid

1 Introduction Microbubble injection is a very effective method to reduce the frictional resistance (as much as 80%) of a turbulent boundary layer, which is called microbubble drag reduction (MBDR). MBDR can be achieved by direct injection of gas through slots or porous skins [1–4] or from the generation of hydrogen by electrolysis at the wall [5]. The primary parameters, independent of gas type and Reynolds number, appear to be the actual gas flow rate mainly referenced to injector conditions of temperature

L.-F. Jiao (*) and T. Kunugi Department of Nuclear Engineering, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan e-mail: [email protected] F.-C. Li School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, China T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_29, © Springer 2011

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and pressure [6, 7], and the location of the bubbles in the flow [8–11]. Merkle and Deutsch provided a comprehensive review of skin friction reduction by microbubble­ injection in 1990 [12]. A spectacular reduction of energy losses in turbulent flows can also be achieved by the addition of small amounts of certain polymers or surfactants [13–16]. For polymer solutions, it seems like the elongational viscosity, caused by high molecular structures, can depress the turbulence to reduce frictional drag; at another hand, surfactant drag reduction is uniquely found for systems containing wormlike micelles, whose structures are similar with that of polymer moleculars. But the detail mechanism for polymer and surfactant drag reduction may be different as described below. Here, considering both polymer and surfactant drag-reducing solution expresses high viscoelasticity, we define both polymer and surfactant drag reduction as viscoelastic drag reduction (VEDR) for short. To make things interesting, Malyuga et al. [17] and Philips et al. [18] found that there was a mutual intensification of polymers and microbubbles for drag reduction. Then, Fontaine et  al. [19], through injecting microbubbles to homogeneous polymer solutions, provided the following correlation of the absolute drag reduction for the combination of polymers and microbubbles,

(C

f

/ Cf0

)

absolute

(

= Cf / Cf0

)

polymer only

(

× Cf / Cf 0

)

microbubble only



(1)

This suggests that the two processes of drag reduction act independently of each other. Furthermore, if injecting microbubbles and polymer solutions to the turbulent boundary layer together, they can produce even higher drag reduction and create a synergistic effect [17, 18, 20], which puts more significance on the observation of the combination of MBDR and VEDR.

2 Comparison Between MBDR and VEDR 2.1 Location of the Additives Both microbubbles [8–11, 21] and surfactant [22, 23] own most effective drag reducing ability when they are near the buffer region of high Reynolds stress, turbulent production, and momentum transfer. So, both MBDR and VEDR reduce drag mainly based on the control of turbulence inside the boundary layer.

2.2 Amount of the Additives The amount of microbubbles or surfactant in the boundary layer is separately described by void fraction and concentration generally.

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The definition of the average void fraction a: a = Qa / (Qa + Qw )



(2)



here, Qa is the injecting air flow rate, and Qw is the water flow rate. In general, the magnitude of the drag reduction increases as the volume of bubbles in the boundary layer is increased until a maximum skin friction reduction of typical 80–90% of the undisturbed skin friction level is reached [19, 24, 25]. However, surfactant flows just own high efficient drag reducing ability at certain concentration range. The minimum value of effective drag-reducing concentration corresponds to the critical concentration (Ct, which increases very rapidly with temperature [26]) to form rod-like micelles. Then, with the increase of surfactant concentration, the drag reduction increases monotonously to the symposium maximum drag reduction [27], and continue increase of the surfactant concentration will just result in the increase of the apparent viscosity of the fluid, which reversely decreases the drag-reducing ability until zero [28]. Obviously, the optimal dragreducing concentration corresponds to the values at symposium maximum drag reduction. It was also found that this most effective concentration increases with the increase of pipe size, which may partly due to the adsorbing effect of the pipe walls. Virk et al. [29] examined drag-reduction data for a large number of “concentrated” polymer solutions and proposed a maximum drag-reduction asymptote (MDRA) as follow (4,000 < Re < 40,000):

1/

f = 19.0 log Re f − 32.4 or

f = 0.58Re −0.58

(3)

Zakin et al. [27] represented an MDRA for surfactants and aluminum disoaps which lies significantly below (3):

f = 0.32Re −0.55

(4)

2.3 Additives and Solvent Properties For MBDR, the size of bubbles is another essential issue [30, 31] through affecting bubble trajectories and thus bubble location and amount in the boundary layer [1]. The most significant characteristic of the bubble sizes is their diameter in comparison to the turbulence scales. According to the size of the bubbles against turbulence scale, it can be classified to mainly two kinds, large bubbles whose size is larger than turbulence scale, and small bubbles whose size equal to or are smaller than turbulence scale. The bubbles in MBDR mainly belong to small bubbles. As for small bubbles, the turbulence intensity of the flow decreases monotonically according to the amount of the microbubbles. As for large bubbles, the wake after bubbles reversely enhance the turbulence intensity at low bubble density; however, some successful drag reduction cases were also reported [31], during which high bubble deformation and high void fraction always companies.

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Regarding the VEDR, as mentioned at the beginning, the existence of the microstructures (high molecular structures or the rod-like micelles) is the main reason of the drag reduction [32]. And their length is directly associated with their drag-reducing abilities while longer length corresponds higher and more stable drag reduction, by providing more chances for entanglement and interaction with the flow [26, 32, 33]. It has also been confirmed that the extension of the microstructures is critical for drag reduction. The most effective drag reducers are essentially in linear structure, with maximum extension for a given microstructure length [32]. Under the observation of electric birefringence, it was found that the length of rod-like micelles decreases with rising temperature and increases with rising surfactant concentration, and can be stabilized by adding counter-ions which prevent the aggregation of the microstructures [34]. Based on the above information, it is possible to explain the synergy effect of the combination of MBDR and VEDR from the interaction of bubbles and viscoelastic microstructures, which may include the changes of the length and extension of the viscoelastic microstructures and the location, amount and size of the bubbles in the boundary. Ferrante et  al. [35] also observed the influence of solvent surface tension on MBDR through observing the drag-reducing effect of microbubbles injection into homogeneous surfactant flow with a moderate (50%) decrease in surface tension comparing to water flow [19]. It was found that such decrease in surface ­tension had little to no effect on the drag reducing characteristics of microbubble injection. However the influence of the viscoelasticity on MBDR is still not reported, which maybe very important for turbulence control and is meaningful to be further studied in the future.

3 Flow Behaviors in MBDR and VEDR Flows 3.1 Velocity Distribution Changes (a) Streamwise velocity:  In the near wall area, both MBDR and VEDR flows show a reduction of streamwise velocity near the wall, and a clear decrease in velocity gradient which directly expressed the decrease of the shear stress in drag reducing flows comparing to water flow [36–38]. (b) Wall-normal velocity:  For VEDR flows, the mean wall-normal velocity equals to zero similar with water flows. But for MBDR, the condition is a little complex according to the difference of bubble amount in the boundary layer. Here we cite the results of Javier et  al. [37] to depict the detail situation. In their experimental results, the mean wall-normal velocity was slightly suppressed while “a = 1.5%, DR = 10.1%”, but it turned to become positive while a is increased to 5.1% and DR increased to 41.9%. As to the reason of this positive mean normal wall velocity, Ferrante et al. related this with the bubbles concentration

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grade near the wall [39]. At high bubble void fraction, the appearance of such a positive wall-normal velocity may, in turn, reduce the mean streamwise velocity and displace the quasi-streamwise longitudinal vortical structures away from the wall as described in Sect. 2.3. (c) Non-dimensional streamwise velocity distribution:  In the near wall area of both MBDR and VEDR flows, the increasing of the viscous sublayer can also be got from the logarithm velocity curve [6, 37, 40], and it is also found that the buffer layer becomes expanded and the slope of the velocity profile in the logarithmic layer increases.

3.2 Turbulent Flow Characteristics (a) Turbulent intensity (TI):  TI = u ′ / U or urms / U , here, U is the mean velocity of the flow. It is known that the wall-normal component of turbulent intensity appreciably decreases for both drag-reducing flows [40–42]. While the changes for the streamwise component of turbulence intensity are not so clear, both slightly increase and decrease is reported. (b) Reynolds shear stress:  In both MBDR and VEDR flows, the Reynolds shear stress is significantly decreased in fully drag-reducing flow as a result of the depress of the wall-normal turbulent intensity and the de-correlation of the two components of velocity fluctuation [40, 43]. For VEDR, an additional viscoelastic shear stress is produced by viscoelasticity comparing to MBDR, to partly compensate the deficit of the Reynolds shear stress [40]. (c) Vortex field changes:  The main character of turbulent flow is the existence of the hairpin vortex structures in the near-wall region, where they generate turbulence bursting events – important events of turbulence production and mixing [44]. The suppression of turbulence bursting events and the increase of the spanwise gaps between the wall streaks is obvious in velocity visualization tests in both MBDR and VESR flows comparing to that in water flows [39, 40, 43, 45–47]. Not only the magnitude of turbulence was decreased as mentioned above, but also the turbulent structure was changed. In VEDR flow, it was also found that the vortex tubes or the hairpin vortex leg(s) inclined toward the wall and the asymmetrical hairpin vortices were the dominant vortex structure [48, 49]. In bubbly flow, Ferrante and Elghobashi [39] numerically certificated that microbubbles can displace quasi-streamwise longitudinal vertical structures away from the wall at high void fraction. (d) Possible mechanisms:  Though the mechanism of turbulent drag reduction has not yet been fully investigated for either MBDR or VEDR, here, based on the above analysis, the following possible mechanisms are concluded: For MBDR, at low void fraction, the turbulence is highly depressed through the interaction between microbubbles and turbulence. At high void fraction, the decrease of the effective density and the increase of the effective density due to

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the appearance of bubbles may be the steady effect of drag reduction. And the ­presence of bubble concentration gradient in the near wall area create a positive mean wall-normal velocity which, in turn, reduces the mean streamwise velocity and displaces the quasi-streamwise longitudinal vertical structures away from the wall, finally results in drag reduction. These effects combined with the interaction between microbubbles and turbulence acts as the dynamic effects of MBDR. Combination of the dynamic effects and the steady effects may be the basic mechanism of microbubble drag reduction. For VEDR, high extensional viscosity appears to be the key property of dragreducing flows; at the same time, the microstructures are aligned along the flow direction, interacts with the growth and bursts of small turbulent eddies and ­vortices, finally result in turbulent drag reduction. Both polymer solutions and microbubbles appear to have very strong effects on dynamics of turbulence separately through the interaction between microbubbles or the viscoelastic microstructures with the turbulent flow in the buffer layer. (e) Surfactant and bubbles:  As analysis in Sect. 2.3, the influence of viscoelasticity to bubble behavior is very important for the further research on the combination of MBDR and VEDR, which mainly contains the influence on bubble size and shape, bubble distribution in turbulent flows, the forces acting on the bubbles and so on [50, 51]. Surfactants have a strong tendency to adsorb on the bubble interface. For a rising bubble in surfactant solution, the existence of the Marangoni effect [52] impedes bubble rising through reducing the drag force acting on the bubble [53, 54] and changes the distribution of bubbles through changing the lift force acting on the bubbles [54–56] comparing to that in pure water And it is also reported that polymer/surfactant can prevent the bubble coalescence. At another hand, it was found that elasticity can also significantly reduce the drag coefficient of rising solid sphere [57, 58] and its effect becomes more pronounced as the shear-thinning anomaly increases [59].

4 Summary In this article, the detail comparison between MBDR and VEDR is done, which contains the main influencing factors, the velocity distribution, turbulence changes and possible mechanisms. Based on the commonness and difference between these two drag reducing technology, the possible ways to observe the mechanism of the synergy effect for the combination of MBDR and VEDR are proposed. The observation of microbubble behavior in fully viscoelastic drag reducing flows should be done, and mainly focus on the bubble distribution and bubble size changes ­comparing to pure microbubbly flow, in the macroscopic research. In microscopic observation, the interaction between microbubbles, the microstructures and turbulence should be highly notified, which may be recovered through the changes of fluid properties and the turbulence strength and structures.

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In the paper, the possible changes of drag force and lift force acting on bubbles are also proposed. As both drag force and lift force are very important for the simulation of microbubble drag reduction, it is meaningful to clear their detail expressions in viscoelastic drag reducing flows for the further observation of the mechanism of the synergy effect for the combination of MBDR and VEDR.

References 1. Merkle CL, Deutsch S (1989) Frontiers in experimental fluid mechanics (A90-26059 10-34). Springer, Berlin, pp 291–335 2. Migirenko GS, Evseev AR (1974) In: Problems of thermophysics and physical hydrodynamics (in Russian). Novosibirsk, Nauka 3. Bogdevich VG, Evseev AR (1976) In: Investigations of boundary layer control, p 49 4. Bogdevich VG, Malyaga AG (1976) In: Investigations of boundary layer control, p 62 5. McCormick ME, Bhattacharyya R (1973) J Nav Eng 85:11–16 6. Madavan NK, Deutsch S, Merkle CL (1985) J Fluid Mech 156:237–256 7. Fontaine AA, Deutsch S (1992) Exp Fluids 13:128–136 8. Pal S, Deutsch S, Merkle CL (1988) Phys Fluids 31:744–751 9. Legner HH (1984) Phys Fluids 27:2788–2790 10. Marie JL (1987) J Phys Chem Hydrodyn 13:213–220 11. Madavan NK, Deutsch S, Merkle CL (1985) J Fluids Eng 107:370–377 12. Merkle CL, Deutsch S (1990) Progr Astronaut Aeronaut, AIAA 123: 351–412 13. Toms BA (1948) In: Proceedings of the 1st international Rheology Congress, North-Holland, Amsterdam 14. Gyr A, Bewersdorff HW (1995) Drag Reduction of Turbulent Flows by Additives, Kluwer Academic Publishers, the Netherlands 15. Bonn D et al (2005) J Phys Condens Matter 17:S1195 16. L’vov VS et al (2004) Phys Rev Lett 92:244–503 17. Malyuga A, Mikuta V, Nenashev A (1989) In: Proceedings of the 6th National Congress of theoretical and applied mathematics, Varna, Bulgaria, 25–30 Sep, 74-1–6. 18. Philips R, Castano J, Stace J (1998) Seawater drag reduction, Newport, RI, 22–23 July 1998, pp 335–340 19. Fontaine AA, Deutsch S, Brungart TA et al (1999) Exp Fluids 26:397–403 20. Deutsch S, Fontaine AA, Money MJ et al (2006) J Fluid Mech 556:309–327 21. Pal S, Deutsch S, Merkle CL (1989) Phys Fluids A1:1360–1362 22. Tiederman WG, Luchik TS, Bogard DG (1985) J Fluid Mech 156:419–437 23. Smith RE, Tiederman WG (1990) Report PME-FM-90-1. Purdue University, West Lafayette, Indiana 24. Guin MM, Kato H, Yamaguchi H (1996) J Mar Sci Technol 1:241–254 25. Madavan NK, Merkle CL, Deutsch S (1985) ASME J Fluids Eng 107(3):370–377 26. Ohlendorf D, Interthal W, Hoffmann H (1986) Rheol Acta 25:468–486 27. Zakin JL, Myska J, Chara Z (1996) AIChE J 42:3544–3546 28. Zhang HX, Wang DZ, Chen HP (2009) Arch Appl Mech 79:773–778 29. Virk PS, Mickley HS, Smith KA (1970) ASME J Appl Mech 37:488–493 30. Wu SJ, Hsu CH, Lin TT (2007) Ocean Eng 34:83–93 31. Murai Y, Fukuda H, Oishi Y et al (2007) Int J Multiph Flow 33:147–163 32. Lu B, Li X, Scriven LE, Davis HT et al (1998) Langmuir 14:8 33. Hoyt JW (1986) In: Encyclopedia of polymer science and engineering, vol 5, p 129 34. Lin Z, Lu B, Talmon Y et al (2001) J Colloid Interface Sci 239:543 35. Ferrante AA, Elghobashi S (2005) J Fluid Mech 543:93–106

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36. Li FC, Kawaguchi Y, Segawa T, Hishida K (2004) In: Proceedings of the 4th international conference on fluid mechanics, Dalian, China, 28–31 July 37. Javier OV, Yassin AH (2006) J Fluids Eng 128:507–519 38. Michael D, Gavin MS, Thomas JH (1999) J Fluid Mech 388:1–20 39. Ferrante AA, Elghobashi S (2004) J Fluid Mech 503:345–355 40. Yu B, Li FC, Kawaguchi Y (2004) Int J Heat Fluid Flow 25:961–974 41. Kitagawa A, Hishida K, Kodama Y (2005) Exp Fluids 38:466–475 42. Kato H, Iwashina T, Miyanaga M, Yamaguchi H (1999) J Mar Sci Technol 4:155–162 43. Pang MJ, Wei JJ, Yu B (2010) In: ICMF-2010, Possion section one, 31 May 2010, P2.94 44. Schoppa W, Hussain F (1997) Adv Fluid Mech Ser 15:385–422 45. Gutiérrez-Torres CC, Hassan YA, Jimenez-Bernal JA (2008) J Fluids Eng 130:1113041–111304-8 46. Li FC, Kawaguchi Y, Hishida K, Oshima M (2006) Chin Phys Lett 23(5):1226–1228 47. Li FC, Kawaguchi Y, Hishida K, Segawa K (2004) In: Proceedings of IMECE, Anaheim, California, USA, IMECE2004-61023, 13–19 Nov 48. Li FC, Kawaguchi Y, Hishida K, Oshima M (2004) In: Proceedings of HT-FED 2004, Charlotte, NC, USA, HT-FED2004-56119, 11–15 Jul 49. Li FC, Kawaguchi Y, Hishida K et al (2006) Exp Fluids 40:218–230 50. Dewsbury KH, Karamanev DG, Margaritis A (2000) AIChE J 46(1):46–51 51. Tanasawa I, Yang WJ (1970) Awl Phys 41:4526 52. Frumkin A, Levich VG (1947) Zh Fiz Khim 21:1183–1204 53. Fdhila RB, Duineveld PC (1996) Phys Fluids 8:310–321 54. Takagi S, Ogasawara T, Fukuta M, Matsumoto Y (2009) Fluid Dyn Res 41(065003):1–17 55. Fukuta M, Takagi S, Matsumoto Y (2008) Phys Fluids 20:040704 56. Cuenot B, Magnaudet J, Spennato B (1997) J Fluid Mech 339:25–53 57. Chhabra RP, Uhlherr PHT, Boger DV (1980) J Non-Newtonian Fluid Mech 6:187–199 58. Satrape JV, Crochet MJ (1994) J Non-Newtonian Fluid Mech 55:91–111 59. Kawase Y, Moo-Young M (1985) Rheol Acta 24:202–206

Numerical Study on Bubble Growth Process in Subcooled Pool Boiling Yasuo Ose and Tomoaki Kunugi

Abstract  Three dimensional numerical simulations based on the MARS (­Multi-interface Advection and Reconstruction Solver) with a boiling bubble growth/ condensation model which consisted of the improved phase-change model and the relaxation time based on the quasi-thermal equilibrium hypothesis have been ­conducted for the subcooled pool boiling phenomena, especially subjected to bubble growth process. The numerical results regarding the bubble growth process of the subcooled pool boiling show in good agreement with the experimental results and the existing analytical equations among Rayleigh, Plesset and Zwick and Mikic et al. Keywords  Bubble growth process • Numerical simulation • Phase-change model • Relaxation time • Subcooled pool boiling

1 Introduction The nuclear power is very important to clean energy system for the zero CO2 emission. Boiling phenomena is a key to remove the heat from the fuel rods in nuclear reactors such as BWR (Boiling Water Reactor) because the boiling heat transfer has most distinguished efficiency which can be enormous heat transfer coefficient compared to the convection of single-phase flows. It will also play a significant role of the power generation efficiency in nuclear reactors. Therefore, the mechanism of boiling phenomena has been studied extensively over the decades. This study focuses on the subcooled boiling phenomena. Since the subcooled pool boiling is occurred under a condition below the saturation temperature, it is the most complex phenomenon which includes not only the convective heat transfer but also the evaporation and condensation processes. Although the subcooled boiling is very important phenomena, the essential mechanism has not yet been clarified until Y. Ose (*) and T. Kunugi Department of Nuclear Engineering, Kyoto University, Sakyo, Yoshida, Kyoto 606-8501, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_30, © Springer 2011

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now, because the bubble nucleation and growth processes are too fast to observe even by means of the very high-speed camera. Another approach to understand these processes is a numerical simulation. In this study, in order to clarify the heat transfer characteristics of the subcooled pool boiling and to discuss its mechanism, the boiling bubble growth/condensation model for numerical simulation on subcooled boiling phenomena has been developed [1]. In this paper, three dimensional numerical simulations based on the MARS (Multi-interface Advection and Reconstruction Solver) [2] with the bubble growth/condensation model which consisted of the improved phase-change model and the relaxation time based on the quasi-thermal equilibrium hypothesis have been conducted for a nucleated bubble growth process in the subcooled pool boiling, and then the results of the numerical simulations were compared with the existing analytical equations among Rayleigh, Plesset and Zwick and Mikic et al. and also with the experimental observation results.

2 Boiling Bubble Growth/Condensation Model The boiling bubble growth/condensation model for the subcooled pool boiling phenomena was improved by introducing the following models based on the quasithermal equilibrium state: (a) an improved phase-change model which consisted of the enthalpy method for the water-vapor system, (b) a relaxation time derived by considering the unsteady heat conduction. The detail of these models is described in the reference [1].

3 Numerical Simulation Three dimensional numerical simulations based on the MARS with the improved boiling bubble growth/condensation model based on the quasi-thermal equilibrium hypothesis were performed and compared to the visualization experiments in case of the degree of subcooling of 10.3  K for the bubble growth process in the subcooled pool boiling.

3.1 Computational Domain The computational domain for the bubble growth process of the nucleation bubble is shown in Fig.  1. In order to represent the nucleate boiling bubble, smaller computational grid must be needed: the grid size was set to 1  mm in x-, y- and z-directions, respectively. The computational domain size was set to 60  mm (Length) × 65  mm (Width) × 60  mm (Height). The periodic boundary conditions were imposed at the x- and z-directions. The non-slip velocity condition was applied to the wall, and the upper boundary condition in y-direction was set to a

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235

Fig. 1  Computational domain for bubble growth process at DTsub = 10.3 K

constant pressure. The heat flux at the wall was set to 0.25  W/mm2. The initial system pressure was set to an atmospheric pressure and the degree of subcooling in the water pool was set to 10.3  K. The gravitational force was considered as the same as the experimental condition. The hemisphere shaped embryo was put at the center of the heated surface as the initial condition. The superheated limit TSH was set to 383 K (110°C) which was estimated by using the waiting time of the bubble generation cycle obtained from the experiment and the analytical solution of the unsteady heat conduction, so that the critical diameter of the embryo was obtained about 6 mm. Time increment in the computation was set to 10 ns.

4 Results and Discussions Figure 2 shows the time variation of the bubble volume change as a double logarithmic plot regarding the bubble growth process. The square symbols depict the experimental results at DTsub = 10.3 K. The solid line denotes the numerical results. Here, the limitation of the bubble volume change existed because of the limitation of the computational domain size. Since the bubble growth is very fast, the experimental results in the beginning of the bubble growth process can be considered as the inertia-controlled one. It was also known as the Rayleigh equation [3] regarding a spherical bubble growth in the homogeneous superheated liquid as follows: 1/ 2



 2  T − Tsat  hlv rg  R (t ) =   ∞    3  Tsat  rl 

t

(1)

here, R is bubble radius, T∞ is temperature of the superheated layer, Tsat is saturation temperature, hlv is latent heat, r is density and t is time. The suffixes of g and l denote gas and liquid phases, respectively. The dotted line in Fig.  2 denotes the Rayleigh equation. It seems that the beginning of the bubble growth process obtained by the experiment can be predicted by the Rayleigh equation. The present numerical result (the solid line) is also in good agreement with the Rayleigh

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Experiment (∆Tsub =10.3K) Rayleigh Eq. (1) Present

Bubble volume [mm3]

10−1 10−2 10−3 10−4 10−5 10−6 10−7 10−5

10−4

10−3

10−2

10−1

Time [ms]

Fig. 2  Time variation of bubble volume in bubble growth process at DTsub = 10.3 K

e­ quation. This suggests the present bubble growth/condensation model may have a potential to predict the bubble growth process. Since the numerical simulations performed throughout the bubble growth process was very difficult because of the spatial- and temporal-scale changes during the bubble growth process, it requires a tremendous computational time and memory if the fix grid size (1  mm) is used for the whole computation. Therefore, in order to further progress the numerical simulations for the bubble growth process, the patch-work computations with changing the grid size were performed in this paper as follows: (1) The computation for the beginning of the bubble growth process using the ­finest grid size of 1 mm at first. (2) In next the bubble volume obtained from the final result of the previous computation puts a sphere as the initial bubble on the larger computational domain with the grid size of 5 mm. Here, the initial temperature field is recalculated without the bubble. (3) To proceed the computation until the top of the bubble reaches to the ceiling of the computational domain. (4) The same procedure repeats on much larger computational domain with the grid size of 10 mm. On the other hand, according to the previous studies, the later stage of bubble growth process can be considered as the heat-transfer controlled bubble growth process. It was also known that the existing analytical equation proposed by Plesset and Zwick [4] as follows:

R (t ) = 2

(T∞ − Tsat )rl C pl 3 Ja a l t , Ja = p rv hlv

here, Cpl is specific heat at constant pressure and al is thermal diffusivity.

(2)

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In addition, the approximation equation containing both equations of 1 and 2 were proposed by Mikic et al. [5] as follows: R+ =

(

) ( )

3/ 2 2 + t +1 − t+ 3 

3/ 2

 2 [T − Tsat ]hlv r v  A= ∞  3rl Tsat  

R t − 1 , R + = 2 , t+ = 2 2 ,  B /A B /A

1/ 2



 12  , B =  Ja 2 α l  π 

1/ 2



(3)

In this paper, the numerical results by the patch-work computation were ­compared with the experimental results and the existing analytical equations among Rayleigh (1), Plesset and Zwick (2) and Mikic et al. (3) in bubble growth process. Figure 3 shows the time variation of bubble volume change as a single logarithmic plot regarding the bubble growth process. The square symbol shows the experimental results and the solid line denotes the numerical results by the patch-work computations with changing the grid size of 1, 5 and 10 mm in all directions. The dotted line denotes the Rayleigh equation (1), the single-dotted dashed line denotes the Plesset and Zwick equation (2) and the double-dotted dashed denotes the equation of Mikic et al. (3). In the existing analytical equations, since the influence of the degree of subcooling on the bubble growth process was appeared in the later stage because the nucleate bubble was in the superheated layer near the wall, the temperature of superheated layer T∞ was estimated by using the experimental results, i.e., 383 K by (1), 386 K by (2) and 393 K by (3). The summary of the comparison results in Fig. 3 are as follows: (1) The numerical results with the grid size of 1 mm for the beginning of the bubble growth process as the inertia-controlled process as shown in Fig. 3a are in good agreement with the equations of Rayleigh and Mikic et al.

Bubble volume [mm3]

10−1

c

10−2 10−3

b

10−4 10−5

Experiment (∆Tsub =10.3K) Rayleigh Eq. (1) Plesset and Zwick Eq. (2) Mikic et al. Eq. (3)

a 0

Patchwork computations (Grid size=1, 5, 10µm) 0.05

0.1

0.15

Time [ms]

Fig. 3  Comparison of numerical results with experimental results and existing analytical equations in bubble growth process as DTsub = 10.3 K

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(2) The numerical results with the grid size of 5 mm as shown in Fig. 3b are in good agreement with the experimental results and the equation of Mikic et al. and show a little bit apart from the Rayleigh equation. This means that the bubble growth process is gradually changed from the inertia-controlled process to the heat-transfer controlled one. (3) The numerical results with the grid size of 10 mm as shown in Fig. 3c are also in good agreement with the experimental results and the equation of Mikic et al. and are close to the Plesset and Zwick equation as the heat-transfer controlled bubble growth process. Consequently, it was found that the present boiling bubble growth/condensation model can retrieve the experimental results and the existing analytical equations for both the beginning and the later stages of the bubble growth process.

5 Conclusions The numerical simulations based on the MARS with the improved boiling bubble growth/condensation model based on the quasi-thermal equilibrium hypothesis were conducted for the bubble growth process. The results of numerical simulations were compared with the experimental results and the analytical equations among Rayleigh, Plesset and Zwick, and Mikic et al. As the results, the numerical results of both the beginning and the later stages of the bubble growth process were in good agreement with the experimental results and the existing analytical equations. Therefore, it is concluded that the improved boiling bubble growth/condensation model with the relaxation time consideration can predict the bubble growth process of the subcooled pool boiling phenomena. Acknowledgement  This work was partly supported by a “Energy Science in the Age of Global Warming” of Global Center of Excellence (G-COE) program (J-051) of the Ministry of Education, Culture, Sports, Science and Technology of Japan.

References 1. Ose Y, Kunugi T (2010) In: Yao T (ed) Zero-carbon energy Kyoto 2009. Springer, Japan, pp 354–359 2. Kunugi T (2001) MARS for multiphase calculation. Comput Fluid Dyn J 9:563–571 3. Rayleigh L (1917) On the pressure developed in a liquid during the collapse of a spherical cavity. Philos Mag 34:94–98 4. Plesset MS, Zwick SA (1954) The growth of vapor bubbles in superheated liquids. J Appl Phys 25:493–500 5. Mikic BB, Rohsenow WN, Griffith P (1970) On bubble growth rates. Int J Heat Mass Transf 13:657–666

Towards Gyrokinetic Simulations of Multi-Scale Micro-Turbulence in Tokamaks Simulation Code Development Paul P. Hilscher, Kenji Imadera, Jiquan Li, and Yasuaki Kishimoto

Abstract  Drift wave micro-turbulence at ion or electron scale has been ­extensively studied to understand the transport property over the years. It has been shown that the ion temperature gradient (ITG) driven turbulence with zonal flow dynamics­ seems to be responsible for the ion heat transport with neoclassical level in Tokamaks. However, high electron transport observed in experiments could not be successfully explained through the conventional electron temperature gradient (ETG) driven turbulence theory. While various alternative mechanisms, including the trapped electron mode (TEM) have been proposed, multi-scale micro-turbulence covering ion and electron scales may also provide a new fluctuation source and transport channel in plasmas. To simulate the nonlinear evolution of such a multiscale ITG–ETG turbulence involving both kinetic ion and electron dynamics, a new gyrokinetic Vlasov code on high performance architectures is developed, aiming to use more than several thousands CPUs. At the first stage of the large-scale gyrokinetic simulation, the code performance is benchmarked through the calculations of the short wavelength ITG mode comparing with the theoretical results. Keywords  ETG • Gyrokinetics • High performance computing • ITG

1 Introduction Tokamaks are very promising to supply mankind’s future energy demand. But, present day Tokamaks fail to achieve a positive energy balance mainly because plasma confinement is lost due to various instabilities in the plasma, ranging from the MHD scale down to micro-turbulences gyroradius scale of particles. Single-scale micro-turbulences are now mainly well explored, by scale separation assuming an

P.P. Hilscher (*), K. Imadera, J. Li, and Y. Kishimoto Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_31, © Springer 2011

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a

b

Growth rate including FLR

Growth rate excluding FLR

Fig. 1  Analytically calculated growth rates of the electrostatic dispersion relation [4]. For b = 2´10-4, ri/Ln = 2Ö2´10–2, ri/Lti=Ö2´10–1, r/Lte=Ö2´10–1, kxri=Ö2´10–1, k║ri=2Ö2´10–3, t=1 and ld=1 ⁄ Ö300. For the ETG-ai/ITG-ae mode an adiabatic ion/electron response is assumed, respectively. For ITG-ke we assumed kinetic electrons

adiabatic response of the opposite charged species, e.g. Lee [1] or Jenko [2]. But taking also multi-scale interaction into account may strongly alter simulation results obtained from pure single-scale simulations – e.g. Smolyakov [3] discovered that linearly, a short wavelength ITG instability may be excited due to a nonadiabatic kinetic electron response. Figure 1 shows the linear growth of the ETG-ai and ITG-ae with an adiabatic ion/electron response, respectively. In contrast, for an kinetic electron response, the ITG-ke mode is shifted to lower ky, thus in linear mixing theory the heat flux increases. Also, if we exclude finite Larmor radius (FLR) effects, the short-wavelength ITG mode does not appear.

2 Calculation Model The equations governing the ETG–ITG cross-scale turbulence are the electrostatic gyrokinetic equations in shearless slab geometry. We apply the local approximation, where the distribution function fs is split into a Maxwellian part and a small, nonMaxwellian perturbation fs = fMs + dfs; density ns and temperature Ts is assumed to be constant for each species s. The 5-dimensional phase space function fs (X, v║, m) – where X is the guiding center position, v║ the parallel velocity, m the magnetic moment and s the species, which for a simplified fusion plasma model consisting of protons and electrons – is advanced according to  qs u d〈f 〉  ms u / 2 + m B0 3   ddfs (1) dd f = d〈f 〉 w n + w Ts −   f Ms − f Ms − u .  df dy  T 2 T d z dz    s s wn, wTs are defined as w n = L⊥ / Ln and w Ts = L⊥ / LTs , where Ln is the density scale length, LTs the temperature scale length of the governing species and L⊥ the

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problem’s scale length. The electro-static potential f is calculated from Poisson’s equation

∇ 2f − ∑ s

T f− f l D2 s

(

) = −4p ∑ q s

f d 3 ( X + r − x )d 6 Z ,

s s

(2)

2 where l Ds is the corresponding Debye length, Ts is the temperature ratio Ts/T0 and 6 d Z = ms2 B0 d m dv da dX; with the x particle coordinate and r is the Larmor radius. f or ááfññ are the single or double averaged electrostatic potentials, which are defined as



f = ∫ d 6 Z d 3(X + r − x ) f = ∑ fk J0 ( k⊥ rs ),

(3)

k



f

= ∫ d 6 Z d 3(X + r − x ) f

fs 0 n = ∑ sk G 0 (k⊥2 rs2 ). ns 0 k ns 0

(4)

In local approximation, the gyro-averaging can be relatively easily calculated by multiplying in Fourier space J 0 (k⊥ r ), the modified zeroth-order Bessel function of first kind and∞ G0, the double gyro-average weighted by exponential factor G 0 (k⊥2 r s2 ) = ∫ dxe − x J 02 (k⊥2 r 2 x ) . This integro-differential equation is then solved 0 by a Runge–Kutta fourth-order time stepping using Morinishi [5] spatial discretization. For a study of the cross-scale ETG–ITG turbulence in a simple proton–electron plasma with t = Ti/Te = 1, we estimate the computational time by • • • • •

To avoid turbulence correlation the minimum box size is Lx,y = 32ri To resolve the electron turbulence, we require four grid-points/re The cutoff of the Maxwellian velocity-tail must be negligible To resolve Larmor radius effects at least 16 point are required in m The velocity resolution needs to be at least Nv = 64 in Liv = 5 to ensure sufficient energy conservation • Around 50,000 time steps are required for a linear simulations for sufficiently advancing the proton species This would result in a computational time of several billion CPUh per simulation, far too high for present day supercomputers but feasible for the upcoming generation of peta- and exascale supercomputers. The above estimation can be somewhat relaxed by artificially raising the electron mass to me = mi/400, without strongly altering the physical results; as is shown in Fig. 2, where the growth rates in respect of mie are plotted.

3 The Computational Code We developed our own computational code, where we used a modular design with interfaces to hide implementation details of the various libraries we use (e.g. Fast Fourier Transformation, Messaging Passing). This allows us to quickly adjust and

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Fig. 2  Theoretical mode spectra of the ITG-ke mode vs. the ion–electron mass ration mie (color figure online)

optimize for different supercomputing environment and quickly adapt to new supercomputing trends, e.g. GPU accelerators. The modularized code is sketched in Fig. 3. Development of the multi-species, gyrokinetic code was finished and it was successfully benchmarked and optimized. In the current stage, parallelization for the Vlasov- and Poisson part is handled differently. As the Poisson equation is solved in Fourier space, parallel decomposition depends on the FFT library. We use p3dfft [6], which supports decomposition in 2-dimensions x–y or kx–ky. The Vlasov solver, 6-dimensional, is decomposed using the MPI [7] library command MPI_CART for all 6-dimensions, where in x–y direction an equal decomposition as for the Fourier solver is used. Boundary communication is performed using MPI_IRecv and MPI_ISend.1 Additionally, the Vlasov equation can be decomposed in v , m and s direction. In this case, only a subset of all nodes are used for the solution of the Poisson equation, synchronization is then achieved using MPI_Allreduce and MPI_Bcast. The overall parallelization efficiency is shown in Fig. 4. The scaling efficiency strongly depends on the problem size and the chosen decomposition. For large scale simulation an average scaling of 60% can be achieved. Further scaling is mainly limited by MPI_Alltoall operations.  Non-blocking function can be used because the Poisson solver does not require boundary values of the Poisson equation. 1

Towards Gyrokinetic Simulations of Multi-Scale Micro-Turbulence in Tokamaks

Vlasov

Fortran03 CUDA

Poisson

FEM

libMesh

Parallel

MPI MPI-RMA shmem

Helios

FFT

fftw-mpi p3dfft ACML

HDF-5

Analysis

Data I/O

243

Fig. 3  The numerical simulation code Helios and its modules. Each module has an interface to various third party libraries, which can be extended quickly or new libraries can be added. Underlined text are future planned interfaces

Fig. 4  Strong scaling of an ETG-ai simulation. The values right to the dots refer to the chosen decomposition in ( x : y : z : v : m : s ). (Measurements were performed on the Kyoto university supercomputer, a Fujitsu HX600)

4 Summary We showed the importance of cross-scale and multi-scale turbulence for a detailed understanding of a Tokamak plasma. We estimated that performing cross-scale turbulence simulation with kinetic ions and electrons will require huge computational resources, thus a highly parallelized code is necessary. We developed and

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optimized our simulation code to run efficiently on up to O (103 ) CPUs. The next step is to study the physical properties of the cross-scale coupling between the ETG and ITG mode. To increase the accuracy of our simulation, we will also have to increase the mass-ratio mie to more realistic values as well as include toroidal geometry effects; this will require to further optimize and extend the code to make efficiently use of CPUs at the order of O (10 4 − 105 ) But higher scalability is limited by FFT method, so a more scalable Finite-Element method needs to be used to solve Poisson’s equation, See [8]. Acknowledgments  The author (P.H.) is grateful for joining the Kyoto University Global COE program and thanks Monbukagakusho (MEXT) for funding this research. He also thanks the Academic Center for Computing and Media Studies of the Kyoto University for providing the necessary supercomputing access for developing this code.

References 1. Lee GS, Diamond PH (1986) Phys Fluids 29(10):3291 2. Dorland W, Jenko F, Kotschenreuther M, Rogers BN (2000) Phys Rev Lett 85(26):5579 3. Smolyakov AI, Yagi M, Kishimoto Y (2002) Phys Rev Lett 89(12):125005 4. Lee YC, Dong JQ, Guzdar PN, Liu CS (1987) Phys Fluids 30:1331 5. Morinishi Y (1998) J Comput Phys 143:90 6. Pekurovsky D. P3dfft homepage. http://code.google.com/p/p3dfft/ 7. Open-mpi. http://www.open-mpi.org 8. Nishimura Y, Lin Z, Lewandowski J, Ethier S (2006) J Comput Phys 214(2):657

Study of a Particle Confinement in Helical Type Reactor by GNET Code Yoshitada Masaoka and Sadayoshi Murakami

Abstract  Confinement of high energy a particles is an important topic in fusion reactor research. High energy a particles are indispensable to sustaining a high temperature fusion plasma, and lost high energy a particles might damage the first wall. We study the confinement of a particles in a helical type reactor based on the LHD (Large Helical Device) configuration. The GNET (Global NEoclassical Transport) code is used to study a particle confinement with energy diffusion and pitch angle scattering. Recent experimental results of LHD suggest the possibility of a high density reactor. We analyze the velocity space distributions and the energy loss rate for varying plasma density and temperature, keeping the total fusion power constant. It is found that the energy loss rate depends strongly on the plasma density in the configuration which optimizes neoclassical transport. Keywords  GNET • Helical plasma • High-density plasma • a Particle confinement • a Particle heating

1 Introduction In a helical type reactor, the magnetic field is generated mainly by the coil current. This system has several advantages, such as the possibility of steady state plasma and no plasma disruption caused by plasma current. However, the plasma behaviors in three-dimensional magnetic confinement are more complex than that in tokamaks. Several physics and technical problems remain to be studied and solved, such as the behavior and confinement of high energy a particles in helical plasma.

Y. Masaoka and S. Murakami (*) Department of Nuclear Engineering, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan e-mail: [email protected]; [email protected]

T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_32, © Springer 2011

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The Large Helical Device (LHD) [1], a helical type reactor, was built at NIFS (National Institute for Fusion Science) in Toki City, Gifu Pref. The major goals of LHD are to obtain good confinement, high temperature, and high beta plasma for steady state operation. LHD has superconducting coils, which generate a magnetic field of up to ~3 T. The typical plasma major radius is 3.60 m. Simulations for the magnetic configuration optimization for the neoclassical transport have been performed [2]. In addition, based on physics and engineering results from LHD experiments, various designs for the Force Free Helical Reactor (FFHR) [3] have been studied. One of the major goal of FFHR is to achieve a force-free-like configuration, in which the current density is everywhere parallel to the magnetic field. FFHR requires a magnetic field of 6 T, and a plasma major radius of 14 m. In devices such as FFHR, when DT (deuterium–tritium) experiments are performed, the confinement of high energy a particles is very important issue. High energy a particles are necessary to heat plasma and to keep the temperature high. It is necessary for these particles to confine until the thermalization. If high energy a particles are lost, not only the heating power is reduced, but the first wall would be damaged locally. Therefore, it is important to understand the behavior and the confinement of high energy a particles. Recently, the ignition scenario of high-density LHD type reactor has been ­proposed [4]. This scenario has the advantage of reduced the divertor heat flux due to an enhanced radiation loss rate. In this paper, based on the proposed high-density scenario, we have chosen to investigate the high energy a particle confinement in dense plasma, assuming the helical type reactor extending the LHD magnetic configuration, and anticipating the next fusion reactor such as FFHR.

2 Simulation Model In this study, we assumed the fusion reactor extending the LHD magnetic configuration. This reactor has the NC (NeoClassical transport optimized) configuration (Fig. 1) which is based on the configuration Rax = 3.53 m in LHD, where Rax is the magnetic major axis. This reactor has the plasma volume of 1,000 m3 and the magnetic strength of 5 T. The drift kinetic equation for the a particles in five dimension phase space, with pitch angle and energy scattering is described as follow;

∂f + ( v + v D )·∇f + v ·∇V f = C coll ( f ) + Lparticle ( f ) + Sa ∂t

(1)

where f is the distribution function of a particles, v is the velocity parallel to magnetic line, vD is the drift velocity, Ccoll is the collision operator, Lparticle is the loss term from the last closed flux surface, and Sa is the source term of the a particle generated by fusion reaction. We solve (1) using the GNET (Global NEoclassical Transport) code, which uses a Monte Carlo technique to calculate the distribution function of a set of test particles [5].

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247

Fig. 1  Flux contour for the NC configuration

Fig.  2  The relation between ne0 (core density) and Te0 (core temperature), keeping the total fusion power constant

We use the following radial profile for the temperature and density,

ne ( r ) = ne 0 (1 − r 8 ) + ne1 

(2)



Te ( r ) = Te 0 (1 − r 2 ) + Te1 

(3)

where ne and Te are the electron density and temperature respectively, the subscript 0 means the value at the magnetic axis, the subscript 1 means the value at the last closed flux surface, and r is the normalized minor radius. We evaluate the source term Sa according to the fusion reaction rate. We vary ne0 over the range 1.9 × 1020– 10.0 × 1020 m−3, adjusting Te0 to keep the total fusion power P constant.

P=∫

1

0

1 {ne 0 (1 − r 8 ) + ne1}2 σ T (Te 0 ,Te1 , r )dr = const.  4

(4)

where sT is the total reaction cross section. The relation between ne0 and Te0 is plotted in Fig. 2. The initial radial profile of the a particles is plotted in, Fig. 3.

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Fig. 3  The initial profile of a particles, for ne0 = 1.9 × 1020 m−3, the distributed a particles are 10,000

1.5 1 0.5 0 −2 −1.5 −1 −0.5 0 0.5 1 1.5 2 v/ / /v1MeV

v⊥/v1MeV

c

ln fα 9 8 7 6 5 4

2

ln fα

1.5

9 8 7 6 5 4

1 0.5 0 −2 −1.5 −1 −0.5 0 0.5 1 1.5 2 v/ / /v1MeV

b v⊥/v1MeV

2

2

d

ln fα

1.5

9 8 7 6 5 4

1 0.5 0

v⊥/v1MeV

v⊥/v1MeV

a

−2 −1.5 −1 −0.5 0 0.5 1 1.5 2 v/ / / v1MeV

2

ln fα

1.5

7 6 5 4 3 2 1 0

1 0.5 0 −2 −1.5 −1 −0.5 0 0.5 1 1.5 2 v/ / / v1MeV

( )

Fig. 4  Contours taking logarithm of the velocity space distribution log ∫ fdt ne 0 =1.9×1020 m −3 (a) overall average; (b) r = 0.2; (c) r = 0.5; (d) r = 0.97 (color figure online)

3 Simulation Results We run the GNET code with various plasma densities (ne0 = 1.9 × 1020–9.2 × 1020 m−3). Each case is run for 0.2 s at which time the distribution function of the a particles has reached a steady state. Figure 4 shows the velocity space distributions of a particles at various radius of r, and overall average for the ne0 = 1.9 × 1020(m−3). v is the velocity parallel to magnetic

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field and v⊥ is the velocity perpendicular to magnetic field. The volume of v and v⊥ are normalized by v0 (1 MeV). We see that the velocity space ­distribution of a particles varies with the radial position. Near the magnetic axis, at r = 0.2, the fraction of the trapped a particles is reduced compared with the passing particles. (An a is trapped if it has pitch angle of over 60°.) The fraction of trapped particles at r = 0.5, is not so much reduced. Near the last closed flux surface r = 0.97, the fraction of trapped particle is very high. The passing particles move along the magnetic field and collide with the background plasma without deviation from the magnetic flux and slow down. The trapped particles are trapped mostly by the helical ripples and transported outward the magnetic surface, moving complexly. Thus, the fraction of the trapped particle is changed by the flux of a particles. The initial particle density at r = 0.97 is very low (See Fig. 3), the modest value of fraction at r = 0.97 must be due to particles that have moved outward to r = 0.97. This suggests that the trapped particles are transported outward faster than the passing particles. For this reason, we can see that the lost particles are the trapped particles. Figures  5–7 show the energy distribution for each calculation. q is the angle between magnetic lines (the pitch angle); particles with q = 90°, 75° are trapped particles, particles with q = 15°, 30°, 45° are the passing particles, and particles with q = 60° are the transition particles which transit between a trapped particle state and

ln fα 9

ln fα

ρ=0.2 θ = 15° θ = 30° θ = 45° θ = 60° θ = 75° θ = 90°

8 7 6

ln fα

ρ=0.5 θ = 15° θ = 30° θ = 45° θ = 60° θ = 75° θ = 90°

7 6 5

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

v/v1MeV

3

ρ=0.97 θ = 15° θ = 30° θ = 45° θ = 60° θ = 75° θ = 90°

6 4 2 0

4

5 4

8

−2

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

v/v1MeV

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

v/v1MeV

Fig. 5  The velocity distributions of a particle in each pitch angles for ne0 = 1.9 × 1020 m−3 (color figure online)

ln fα 9

ln fα

ρ=0.2 θ = 15° θ = 30° θ = 45° θ = 60° θ = 75° θ = 90°

8 7 6

ln fα

ρ=0.5 θ = 15° θ = 30° θ = 45° θ = 60° θ = 75° θ = 90°

7 6 5

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

v/v1MeV

3

ρ=0.97 θ = 15° θ = 30° θ = 45° θ = 60° θ = 75° θ = 90°

6 4 2 0

4

5 4

8

−2

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

v/v1MeV

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

v/v1MeV

Fig. 6  The velocity distribution of a particle in each pitch angles for ne0 = 5.2 × 1020 m−3 (color figure online)

250 ln fα 9

Y. Masaoka and S. Murakami ln fα

ρ=0.2 θ = 15° θ = 30° θ = 45° θ = 60° θ = 75° θ = 90°

8 7 6

ln fα

ρ=0.5 θ = 15° θ = 30° θ = 45° θ = 60° θ = 75° θ = 90°

7 6 5

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

v/v1MeV

3

ρ=0.97 θ = 15° θ = 30° θ = 45° θ = 60° θ = 75° θ = 90°

6 4 2 0

4

5 4

8

−2

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

v/v1MeV

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

v/v1MeV

Fig. 7  The energy distribution of a particle in each pitch angles ne0 = 9.2 × 1020 m−3 (color figure online)

Fig. 8  The energy loss rates of a particle calculated until the energy loss rate are saturated for ne0 = 1.9 × 1020– 10.0 × 1020 m−3

a passing particle sate. The horizontal axis is the a particle energy, and the l­ongitudinal axis is the logarithm of velocity space distribution of a particles. We see that at every r, the fraction of high energy a particles decreases as the plasma density increases; the decrease in the fraction of high energy a particles is greater than near the edge of plasma. The slowing down time ts depends on the plasma density and temperature and becomes short in high density and low temperature plasma: 3



Te 2 ts ∝ ne

(5)

We see that, in the dense plasma, the fraction of trapped particles near the last closed flux surface decreases more than at other radial positions. This effect increases as particle energy increases. For the reasons mentioned above, it is expected to reduce the loss of high energy a particles in high density plasma. Figure 8 shows the energy loss rate of a particle

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for several the plasma densities. We can see that the loss rate decrease from 5.2 to 0.01% as plasma density increases from 1.9 × 1020 to 10.0 × 1020  m−3. The energy lost is seen to scale as ne−2.9 Thus, in dense plasma, the confinement of high energy 0 a particles improves, and the effect of a particle heating increases.

4 Summary We have investigated a particle confinement in a helical type fusion reactor with varying plasma density and temperature, keeping the total fusion power constant. We have found that the trapped particles are transported outward across magnetic surface. The fraction of trapped particles near the last closed magnetic surface decreases with increasing plasma density because; (1) an increase in the plasma density decrease the slowing down time ts, which (2) decreases the fraction of steady-state high energy a particle, which (3) decreases the flux of high energy a particle, which (4) decrease the fraction of trapped particles near the plasma edge. This, in turn, decreases the fraction of the a particle energy which is lost. We have found that the energy loss rate of a particle decreases in proportion to ne−2.9 in the dense plasma. 0 Acknowledgements  This work is supported by Grant-in-Aid for Scientific Research (C) (20560764) and (S) (20226017) from JSPS, Japan. The authors would like to gratefully acknowledge Mr. Raburn for English discussions.

References 1. Iiyoshi A et al (1999) Overview of the large helical device project. Nucl Fusion 39:1245 2. Murakami S et al (2002) Neoclassical transport optimization of LHD. Nucl Fusion 42:L19 3. Sagara A et  al (2007) Design integration toward optimization of LHD-type fusion reactor FFHR. In: Proceedings of ITC/ISHW2007 4. Ohyabu N et al (2006) Observation of stable superdense core plasmas in the large helical device. Phys Rev Lett 97:055002 (4 pages) 5. Murakami S et al (2006) A global simulation study of ICRF heating in the LHD. Nucl Fusion 46:S425

Study of the Mechanisms Leading to the Nonlinear Explosive Growth of Double Tearing Instabilities in Fusion Plasmas Miho Janvier, Yasuaki Kishimoto, and Jiquan Li

Abstract  In the recent decades, research in magnetic confinement fusion has intensified to achieve a better confinement of the plasmas necessary to obtain power generation. One of the solutions is the formation of internal transport barriers appearing when the magnetic shear is reversed. However, such configuration leads to current-driven instabilities such as the double tearing mode (DTM). In the present work, we study the nonlinear destabilization of the DTM occurring when the generated magnetic islands are close to each other so that the dynamics is enhanced. By choosing a configuration near marginal nonlinear stability for this nonlinear destabilization, we study the possibility for a secondary instability to be generated from the two-dimensionally deformed magnetic structure and to be a cause of the nonlinear destabilization. We find that from an equilibrium with severe deformation of islands, a new secondary instability with a large growth rate can be generated. A parametric dependency analysis shows that this new instability has the same characteristics as a modulational one. Keywords  Current-driven instability • Magnetic islands • Marginal stability • RMHD • Secondary instability

1 Introduction In our modern societies with a constantly growing need of energy, generating power without harming the environment has become a great issue. CO2 being one of the most important contributors to global warming, the use of fossil fuels has to be restrained. Among the possible solutions, nuclear fusion is a promising answer, as the generation of power is safe and sustainable. Research in fusion plasma confinement has been developed over many years, but still needs more insights to explain

M. Janvier (*), Y. Kishimoto, and J. Li Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_33, © Springer 2011

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sudden event leading to plasma disruption and termination. One major ­concern for a better confinement is the development of strong macroscopic instabilities due to magnetohydrodynamic (MHD) activities. Among them is the double tearing mode (DTM), which consists in the reconnection of magnetic field lines, leading to the formation of magnetic islands on two current layers [1]. In some cases explored here, the interaction between those islands becomes important so that the DTM dynamics in the nonlinear phase leads to a sudden explosive growth [2, 3]. Here, we investigate the mechanisms leading to such behavior.

2 Numerical Methods for the Nonlinear DTM The geometrical configuration is a slab geometry where the reduced and normalized MHD equations (flow incompressibility and strong guide field in the z-direction being assumed) is solved numerically:

∂ tY + [f ,Y ] = h∇ 2Y

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∂t ∇2f + [f , ∇2f ] = [Y , ∇2Y ]

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y and f respectively represent the flux and the flow functions B = e z × ∇ ⊥Y + Bz e z and v = e z × ∇⊥f , where ez is the unit vector in the z-direction). Finite difference method is used in the x-direction and we have a Fourier expansion in the y-­direction. No equilibrium flow is supposed ( f 0 = 0 ) and the equilibrium field configuration is the same as in [4]. There are conducting walls at x/a = ±5 and the total mesh number is 2,048 (equal spacing). We have a uniform space grid in the y-direction, with periodical conditions. In the following study, the rational surfaces are separated by a distance 2xs = 1.6 and the resistivity is h = 10−4. Changing the box size in the y-direction (=length) allows different dynamics: when it is increased, longer wavelengths which have a faster evolution are excited. Here, the length is set to 2p × Ly where Ly is changed from 0.5 to 1.2. Note that for Ly < 0.5, the configuration is completely stable. Table  1 summarizes the linear Table 1  Results of numerical runs corresponding to different Ly Ly Growth ratea Remarks 0.40 g < 0 Configuration is completely stable 0.70 5.58 × 10−3 Configuration unstable, saturation 0.75 8.40 × 10−3 Configuration unstable, saturation 0.76 8.54 × 10−3 Configuration unstable, nonlinear destabilization Configuration unstable, nonlinear destabilization 0.80 1.06 × 10−2 Configuration unstable, nonlinear destabilization 1.00 1.82 × 10−2 a Linear growth rate for the mode m = 1

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Fig. 1  Evolution of the kinetic energy for different Ly

Fig. 2  Total energy and islands evolution for Ly = 0.80

growth rate as well as the nonlinear dynamics for different Ly, and in Fig. 1, the nonlinear evolution of the kinetic energy Ek for different Ly is plotted. For Ly = 0.75, the energy Ek evolves from the linear phase to the nonlinear phase by reducing its growth rate and finally saturates (t ³ 15,000, Fig. 1). However, for Ly ³ 0.76, Ek does not saturate but follows instead an explosive growth. Figure  2 shows the evolution the total magnetic (plain curve) and kinetic energy (dotted curve) for Ly = 0.80 as well as the contour plots of the magnetic islands on each

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current sheets at different times of the simulation. The final stage (t = 11,750) c­ orresponds to the total reconnection of the magnetic field after the explosive growth, during which the magnetic islands have exchanged their position (t = 11,450). Therefore, there exists a critical value 0.75 £ Lyc < 0.76 above which the nonlinear evolution is terminated by an explosive growth. This critical threshold defines the marginal stability.

3 Secondary Analysis with Two-Dimensionally Deformed Equilibrium In this section, we present a new analysis for the investigation of the nonlinear destabilization mechanisms. This study focuses on the cases just above the marginal stability (such as Ly = 0.80). To gain more insights on the trigger mechanism of the explosive growth, we consider the development of small perturbations in an equilibrium deformed by magnetic islands. To make the problem consistent, we choose the same islands as what was obtained in the nonlinear development of the DTM (Fig. 2b). At different times of the original simulation, we define a new equilibrium and look at the linear development of the new perturbations. The resulting set of linear equations are as follows:

∂ tY + [feq ,Y ] + [f ,Yeq ] = η∇ 2Y

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where the subscript eq represents the equilibrium flux (resp. flow) now dependent on x and y (two dimensional deformation). The overall analysis can be considered as the magnetic islands themselves are evolving very slowly during the nonlinear phase, before the explosive growth (Fig. 2a).

4 Results and Discussion The following analysis is conducted for the case Ly = 0.80. We define new equilibria with developed magnetic islands of different size. Those correspond to the profiles shown in Fig. 2b. Thus, we refer to the different equilibria by the width of the equilibrium islands: bigger islands correspond to advanced times of the previous ­nonlinear simulation of the DTM. Note that the islands being similar, we will only refer to the size of one island (noted w). Equations (3) and (4) are solved numerically via an initial value problem, which gives for each equilibrium a specific linear growth rate. The different values obtained in function of the width of the equilibrium ­magnetic islands are reported in Fig. 3.

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Fig. 3  Evolution of the growth rate in function of the magnetic island size of the new equilibrium

• When the equilibrium magnetic islands are very small (up to t ~ 1,500 in the DTM simulation), we recover the linear growth rate of the DTM. This is consistent as the undeformed current sheets give rise to current-driven instabilities: the perturbation is actually a DTM instability. • When the magnetic islands are small but deform the current sheets (from t ~ 1,500 to 4,500 in the DTM simulation, corresponding to a width 0 < w £ 0.7), the linear growth rate of the perturbation decreases. It is understandable as the current layers start to deform and there is a flattening of the current profile: there is less free energy to give to the current driven instabilities, and the perturbations can be understood as double tearing instabilities evolving under a flattened ­current equilibrium. • However, up to w ³ 0.7 (critical size of the magnetic islands), the linear growth rate of the new perturbation discontinuously increases. As the current sheets are strongly deformed by the magnetic islands, one can understand that the perturbations are a new instability evolving with an energy source given from the deformation itself. • In Fig. 3, the linear growth rate of the perturbation has been reported in semilogaω rithmic scale, therefore yielding the following relation from ω ≥ 0.7 : g 2nd ~ e . On the other hand, the width of the island can be approximated as ω ~ Y so that γ 2nd ~ e Y . We remark that the characteristics of the secondary instability are similar to that of a modulational instability. This latter corresponds to a positive feedback between a seed field, a pump field and the corresponding side bands, and the linear growth rate of this instability has been found to be proportional to the amplitude of the pump field. A typical case would be the generation of macro-scale zonal flow that are nonlinearly produced from micro-scale turbulence. Here, the secondary insta-

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bility generation can be seen as a mechanism to accelerate the nonlinear flows in the final stage of the DTM.

5 Conclusion In this paper, we investigate the nonlinear destabilization occurring during the development of the DTM. For cases above marginal stability, macroscale MHD islands grow to a size for which the explosive growth can be triggered. In order to investigate the mechanisms at the origin of this trigger, we have set up a secondary analysis with a new numerical simulation. It consists in solving the traditional linear two-field reduced MHD equations but with an equilibrium that already has formed magnetic islands. This quasi steady-state has been taken from the original nonlinear simulation of the DTM. The equations are solved numerically and give the growth rate of the perturbation in function of the width of the equilibrium islands. We find that for little magnetic islands, the current sheet is flattened so that the strength of the instability is decreased. However, for larger islands, energy source from the deformation itself can produce a secondary instability which growth rate scales with the magnetic island width as: γ 2nd ~ e Y . This feature similar to a modulational one can explain the generation of very fast nonlinear flows during the explosive growth of the nonlinear DTM.

References 1. Chang Z et al (1996) Off-axis sawteeth and double-tearing reconnection in reversed magnetic shear plasmas in TFTR. Phys Rev Lett 77:3553–3556 2. Ishii Y, Azumi M, Kishimoto Y (2002) Structure-driven nonlinear instability of double tearing modes and the abrupt growth after long-time-scale evolution. Phys Rev Lett 89:205002 3. Wang ZX et  al (2008) Shear flows induced by nonlinear evolution of double tearing modes. Phys Plasmas 15:082109 4. Pritchett PL, Lee YC, Drake JF (1980) Linear analysis of the double-tearing mode. Phys Fluids 23:1368–1374

Remote Collaboration System Based on the Monitoring of Large Scale Simulation “SIMON”: A New Approach Enhancing Collaboration Akihiro Sugahara and Yasuaki Kishimoto

Abstract  Large scale simulation using super-computer, which requires long CPU time and produces large amount of data, has been introduced as a third pillar in various fields in science and technology. Such simulations are expected to bring scientific discoveries through elucidation of various complex phenomena, which are hardly studied by using conventional theoretical and experimental approaches. To assist such simulation studies in which many collaborators working at geographically different places participate, we developed a unique remote collaboration system, referred to as SIMON (SImulation MONitoring System). This system utilizes a client–server control introducing the idea of update processing, which is contrary to that of widely used post processing. As a key ingredient, we developed the trigger method, which transfers various requests for the update processing from the simulation (client) running on a super-computer to a workstation (server). The server that received requests from the simulation, such as data transfer, analysis and visualization, etc., performs the corresponding tasks. The server delivers the latest results on web, so that the collaborators can monitor the results at any place in the world. We confirmed that the system works well and plays an important role as a common platform. Keywords  Client–server control • Large scale simulation • Remote collaboration • Simulation monitoring • Update processing

1 Introduction Research of environmental subjects is significantly important for human being to service in future, where different types of many information have to be correctly gathered and handled. In recent years, computer simulation plays an essential role

A. Sugahara (*) and Y. Kishimoto Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_34, © Springer 2011

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in various science and technology fields and has been introduced as a third pillar in addition to exiting theoretical and experimental approaches. However, as the simulation becomes large scale and the problem becomes complex, the participation of many collaborators playing different roles, i.e. different tasks, fields, etc., becomes important besides scientists directly managing the simulation. In order to assist such simulation projects, here we propose a unique remote collaboration system referred to as SIMON (Simulation Monitoring System) [1, 2]. This system is based on a client–server control introducing a concept of update processing of simulation data with proper time intervals running on a super-computer. As a key ingredient of the system, we developed the trigger method, which exchanges various information of the simulation between super-computer (client) and workstation (server). By incorporating with the common internet technologies, the SIMON plays an important role as a simulation platform on which many collaborators can share the various information of simulation at any place in the world. We describe a concept of the SIMON in Sect. 2 and its key ingredients (That is trigger and hierarchical visualization methods) in Sect. 3. We provide an example in Sect. 4 and give concluding remarks in Sect. 5.

2 Concept of the SIMON Figure  1 illustrates the schematic view of the SIMON system. The SIMON is ­constructed as a client–server control that exchanges information between supercomputer (client) on which the simulation executing and an external workstation

Fig. 1  Schematic view of flowchart of various operations and functions in SIMON system

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(server). The SIMON-client requests the server to perform data transfer and ­analysis, visualization, etc., during the simulation (Fig. 1: trigger). According to the requests, the SIMON-server is triggered by the client and starts operation (Fig. 1: blue line, purple line). The SIMON-server sends the latest results to web during simulation, so that collaborators can monitor the simulation results at any place in the world. This approach is different from that of the post processing where data analysis is performed after the end of simulation and also from the real time monitoring [3, 4] where graphic routines is directly inserted in the main program and the results are simultaneously obtained synchronized with the ongoing simulation. Namely, it is more important to know the latest information and the results at appropriate times during simulation. We refer this concept as to update processing. To achieve this idea, we developed two methods, i.e., trigger and hierarchical visualization method.

3 Key Ingredient of the SIMON 3.1 Trigger Method Figure 2 illustrate a flowchart of the simulation and the role of trigger method. Here, we have installed two tasks (data transfer and visualization) between two computational loops 1 and 2. In the case of Fig. 2b, those two tasks are directory installed in the program. In this case, besides the increase of the execution time, once some trouble happens during these tasks, the simulation is interfered and/ or interrupted. On the other hand, in the case of Fig.  2c, the simulation only

Fig. 2  Loop of simulation and the role of Trigger method

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transfer the requests related to these tasks to an external server after the loop 1 and then the server performs the update processing according to these requests. It is noted that the time to transfer the requests to server is negligibly short, so that the simulation can move to the loop 2 immediately. Even if some trouble happens to the network and/or server machine, the simulation is not interfered. We refer this operation as to the trigger method in the sense that the simulation running on the super computer triggers an action requesting the update ­processing to an external server.

3.2 Hierarchical Visualization Method As we discussed in Sect. 3.1, once the external workstation (server) receives the trigger message of visualization from the simulation (client), the SIMON system automatically performs related tasks without affecting the execution of the simulation. In this case, the information of the visualization, e.g., the title of graphs, physical quantities in horizontal and vertical axes, maximum/minimum values, etc., has to be included in the message. On the other hand, in order for the collaborators to flexibly analyze the data according to their interest, it is desirable to keep various functions of visualization software. Therefore, we developed the SIMON system so that the collaborators can efficiently analyze the data using the function of visualization software and that of intercommunication of web. We refer this method as to the hierarchical visualization, which is divided into four layers depending on the user’s need, i.e., “basic analysis”, “web analysis”, “scenario” and “detail analysis”. Figure  3 illustrates an example of “web analysis”. In this case, the maximum value of vertical axis is not properly chosen. However, the user (collaborator) can change these values through web browser as shown in Fig.  3 (lower graph).

4 An Example Using SIMON System We applied the SIMON system to a project indicating lightning phenomena ­utilizing a three-dimensional relativistic particle code, EPIC3D [5–7]. Figure  4 shows the web page on which the latest results of analyses and visualization during simulation are indicated. Here, we performed the lightning simulation for compressed neon gas with a density of 1.2 × 1020 cm−3. A tiny ionization spot with Ne+2 is initially set to trigger a discharge and a high-voltage electric field, E = 2.5 × 106  V cm−1, is uniformly applied in the system. Figure  4(1) shows the time history of the ion density with different charge state q. Note that this graph updated while the simulation is executing. Figure 4(2) shows the snap data of the two-dimensional density distribution. This data is updated on web server about every 2 h.

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Fig. 3  Example of “Web layer” in Hierarchical visualization method

5 Concluding Remarks In order to perform the study of large scale simulation efficiently, we have proposed a remote collaboration system SIMON, by which many collaborators working at geographically different places can participate to the project. The collaborators can monitor the latest information and results of ongoing simulation via internet. The system is constructed based on a client–server control using trigger method, which is a key ingredient of the system. In this method, the simulation running on a supercomputer actively controls the timing of update processing by transferring the various requests to an external server, which performs the tasks in parallel to the main simulation. In addition, the collaborators are able to analyze the simulation data depending on their interest by using the hierarchical visualization method of the SIMON system which allows to interactively make graphs. It is noted that the system is designed based on conventional technologies ­without using special hard-ware and soft-ware applications. Therefore, the SIMON

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Fig.  4  Various information of simulation about lightning produced on a web page using the SIMON system

can be installed readily in any kind of client–server system. We applied the system to a large scale simulation project of lightning phenomena and confirmed that the system works well and plays an important role as a simulation platform on which many collaborators work together. We will develop the system by cooperating not only with simulation data but also with experiment one. Keeping the security is an important issue which will be discussed in different article. Acknowledgements  We acknowledge to Mr. M. Kawanobe, and Dr. T. Masaki for their encouragements to our work. About Sect. 5, the example of introducing the system is due to a collaboration research with Dr. M. Kato.

References 1. Sugahara A, Kishimoto Y (2008) J Plasma Fusion Res 84(1):51–61 2. Kishimoto Y, Sugahara A, Li JQ (2008) Fusion Eng Des 83(2–3):434–437 3. Ogasa A et al (2001) FPIGA 158:47–53. Vis Link http://jp.fujitsu.com/solutions/hpc/app/vislink/ 4. Ogasa A, Moriya K et al (2005) JSCES 10(1):93–94. Vis Trace http://jp.fujitsu.com/solutions/ hpc/app/vistrace/ 5. Kishimoto Y (2004) Annual Report of the Earth Simulator Center, vol 04, 199 6. Fukuda Y, Kishimoto Y, Masaki T, Yamakawa NK (2006) Structures and dynamics of cluster plasmas created by ultrashort intense laser fields. Phys Rev A 73(031201(R)):1–4 7. Kishimoto Y, Masaki T (2006) J Plasma Phys 72, Part 6:971–974

Target Design of High Heat and Particle Load Test Equipment for Development of Divertor Component Do-Hyoung Kim, Kazuyuki Noborio, Yasushi Yamamoto, and Satoshi Konishi

Abstract  The divertor of fusion reactor is expected to be influenced by high ­density load of 0.1–10 ms, 10 MW/m2 by particle radiation of disruption phenomenon and edge localized mode (ELM). It requires components which can tolerate this high temperature particle and heat flux. In this study, for the target design of high heat and particle load test equipment so as to develop the divertor component, we defined lithium lead (LiPb) as the coolant of divertor components at a temperature that allows efficient energy use. The outlet temperature of this coolant is aimed at 800°C. Flow condition of divertor coolant was numerically evaluated in the designed target made of silicon carbide (SiC) and tungsten (W). Experiment simulating the particle and heat load on the designed divertor component is also planned. The results of the numerical analysis are reflected in the development of the divertor component. Keywords  Divertor • Finite element method • High temperature particle load • Hydrogen ion beam

1 Introduction The divertor of International Thermonuclear Experimental Reactor (ITER) is expected to receive the greater amount of the heat flux (0.1–10 ms, ~10 MW/m2 in steady state) coming from the plasma in the strike point region by particle radiation of disruption phenomenon and edge localized modes (ELMs) [1]. It requires components which can tolerate this high temperature particle and heat flux. The divertor

D.-H. Kim (*), Y. Yamamoto, and S. Konishi Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan e-mail: [email protected] K. Noborio Institute of Sustainable Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_35, © Springer 2011

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cooled by coolant with the exception of water and helium have not currently been developed. We need a concept of divertor which can take high thermal energy from this heat flux when considering thermal efficiency. Divertors of ITER, Slim CS and European Power Plant Conceptual Study (PPCS) models have low heat flux or low coolant outlet temperature (Fig. 1). In this study, for the target design of high heat and particle load test equipment [2] so as to develop the divertor component, we selected lithium lead (LiPb) as the coolant of divertor components at a temperature that allows efficient energy use. The outlet temperature of this coolant is aimed at 800°C (Fig. 1). Flow condition of divertor coolant is numerically evaluated in the designed target made of silicon carbide (SiC) and tungsten (W). The main goal of this work was to select the suitable design of divertor components that meets these requirements by numerical analysis.

2 Concept of Design 2.1 New Model of Fusion Reactor ITER divertor is influenced by heat flux of about 9–10  MW/m2 at small area (Fig. 2a). Therefore, we suggested new model of small-scale fusion reactor which has divertor vertical target length of 0.8 m and receives heat flux of 10 MW/m2 at larger area to take higher heat energy than it (Fig. 2b).

2.2 Design of Divertor Component If the coolant in the continuing cooling pipe like ITER divertor receives continuously thermal energy from heat flux of 10  MW/m2 like Fig.  2b case, divertor ­materials on outlet side of coolant may not tolerate high temperature of coolant. Therefore, we selected a divertor component model which can take efficiently high thermal energy from heat flux at each mono-block (Fig. 3a).

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In the divertor design, W is usually considered as thermal shield and sacrificial layer for plasma-facing components due to its high resistance against sputtering. For the high temperature divertor, the requirement of a high thermal load also implies that W is most suitable as the structure material due to its excellent thermophysical properties: high melting point, high thermal conductivity, and low thermal expansion [4]. SiC ceramics are considered as functional materials of sustainable and advanced energy systems, because of their low thermal-expansion coefficient and good ­thermal-shock resistance as well as excellent physical and chemical stability at ­elevated temperature [5]. The liquid metal of LiPb is known that high temperature can be obtained and the radiation damage does not make a big difference [6]. Therefore, we chose W and SiC as the divertor materials and defined LiPb as the coolant of divertor component at a temperature that allows efficient energy use. Table 1 is the condition of divertor mono-block and LiPb flow. In this study, the inlet temperature of LiPb is 400°C and the outlet temperature of it is aimed at 800°C.

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Table 1  The condition of divertor mono-block and LiPb flow Heat flux 10 MW/m2 Mono-block size 500 × 500 mm Inlet temperature of coolant 400°C Aimed outlet temperature of coolant 800°C Cross-sectional area of coolant outlet 1.13 cm2 Depth of flow channel in SiC 4.7 mm Demanded flow rate 29 cc/s Demanded flow velocity on diameter 12 mm pipe 25.67 cm/s

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3 Analysis by Finite Element Method 3.1 Analysis Model The Ansys 10 Flotran of finite element method (FEM) was used for the suitability evaluation of divertor component design. Figure 4 shows four divertor component models for Ansys analysis.

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In these models, plasma-facing materials is W and parts except for W are made up of SiC. The Thickness of W in case 1 is 2 mm and it of SiC between W and LiPb flow channel is 2 mm. Case 2, 3 and 4 have the complex flow channel than Case 1. Those of W in case 3 and 4 are each 4 mm and 2 mm, but SiC panels between W and LiPb flow channel are not.

3.2 Results of Analysis and Discussion The distribution of temperature was numerically evaluated on aforementioned divertor component models by Ansys. The maximum temperature of W, SiC and LiPb is shown in Fig. 5 when each mono-block receives heat flux of 10 MW/m2 on flow velocity 25.7 cm/s of LiPb (Table 1). On the whole, the temperature of SiC exceeds the use limit (about 1,500°C). In case 1 (Fig. 5a), the gap between monoblock materials and LiPb temperature is wider than the others. Therefore, we ­carried out the analysis on two times (50  cm/s) of LiPb flow velocity with the

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exception of case 1 model. Figure 6 shows the distribution of temperature when the flow velocity of LiPb is 50 cm/s. In these cases, each material is enough to tolerate the high thermal energy. The model of Case 4 (flow velocity; 50 cm) had lower temperature on each mono-block material than the other cases in Fig. 6. In addition, the temperature of coolant outlet has better result than our goal. The temperature of coolant outlet depends on the thermal conductivity of mono-block materials, coolant flow velocity and distance between plasma-facing surface and cooling channel. An irradiation test by the high temperature particle load test equipment which we have designed and assembled in Kyoto University [2] will be carried out with the prototype model based on this study to verify the calculation.

4 Conclusions The target of high heat and particle load test equipment for the development of divertor components was designed as follows; W, SiC and LiPb were chosen as the mono-block materials and coolant of divertor components to take high thermal

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energy over 800°C from particle and heat load. The required design of divertor component was calculated by Ansys. The divertor component can tolerate high temperature particle and heat flux. The prototype of divertor component based on this study will be made and the irradiation test will be carried out by high temperature particle load test equipment.

References 1. Mazzone G, Brolatti G, D’Agata E, Iorizzo A, Lucca F, Marin A, Merola M, Petrizzi L, Pizzuto A, Roccella M, Semeraro L, Zanotelli G (2002) Design of plasma facing components for the ITER feat divertor. Fusion Eng Des 61–62:153–163 2. Yamamoto Y, Kim D-H, Park C-H, Konishi S (2009) Development of high temperature particle load test equipment by hydrogen ion beam for divertor. Proceedings of 23rd symposium on fusion engineering, San Diego, CA, 31 May–5 June 2009; SP3C-40 3. Federici G, Andrew P, Barabaschi P, Brooks J, Doerner R, Geier A, Herrmann A, Janeschitz G, Krieger K, Kukushkin A, Loarte A, Neu R, Saibene G, Shimada M, Strohmayer G, Sugihara M (2010) Key ITER plasma edge and plasma–material interaction issues. J Nucl Mater 313–316:11–22 4. Norajitra P, Boccaccini LV, Gervash A, Giniyatulin R, Holstein N, Ihli T, Janeschitz G, Krauss W, Kruessmann R, Kuznetsov V, Makhankov A, Mazul I, Moeslang A, Ovchinnikov I, Rieth M, Zeep B (2007) Development of a helium-cooled divertor: material choice and technological studies. J Nucl Mater 367–370:1416–1421 5. Park Y-H, Park J-S, Hinoki T, Kohyama A (2008) Development of manufacturing method for NITE-porous SiC ceramics using decarburization process. J Eur Ceram Soc 28:657–661 6. Kim D, Noborio K, Hasegawa T, Yamamoto Y, Konishi S (2010) Development of LiPb-SiC high temperature blanket. In: Zero-carbon energy Kyoto 2009. Springer, Heidelberg, pp 113–119

Experimental Investigation on Contact Angles of Molten Lead–Lithium on Silicon Carbide Surface Yoshitaka Ueki, Tomoaki Kunugi, Keiichi Nagai, Masaru Hirabayashi, Kuniaki Ara, Yukihiro Yonemoto, and Tatsuya Hinoki

Abstract  A contact angle database of a molten lead–lithium eutectic alloy (PbLi) droplet on a silicon carbide (SiC) is basic information for research and development both of magnetic confinement fusion (MCF) and inertia confinement fusion (ICF) blankets. PbLi coolant/breeder flows in the coolant channel made of the SiC walls will experience a flow slip at the wall, called as a magnetohydrodynamic (MHD) slip flow. An ICF blanket adopts a molten PbLi film flow along the SiC first wall. The PbLi contact angle database is necessary for numerically predicting the molten PbLi film flow behaviors. The present study is attempted to measure the contact angles formed between the molten PbLi and the various SiC surfaces, e.g. a chemical vapor deposition (CVD) SiC and a nano-infiltration and transient eutectic-phase (NITE) SiC/SiC composite in an inert atmosphere in order to examine an initial PbLi wettability. As the results, the molten PbLi contact angle database is obtained, which covers the PbLi temperature from 250 to 400°C on the surface-polished and unpolished SiC, respectively. Keywords  Contact angle • Lead–lithium • Silicon carbide

Y. Ueki (*) and T. Kunugi Department of Nuclear Engineering, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan e-mail: [email protected] K. Nagai, M. Hirabayashi, and K. Ara Advanced Nuclear System Research and Development Directorate, Japan Atomic Energy Agency, O-arai, Ibaraki, Japan Y. Yonemoto Applied Laser Technology Institute, Tsuruga, Fukui, Japan T. Hinoki Institute of Advanced Energy, Kyoto University, Uji, Kyoto, Japan T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_36, © Springer 2011

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1 Introduction A contact angle database of a molten lead–lithium eutectic alloy (PbLi) droplet on a silicon carbide (SiC) is basic information for research and development both of magnetic confinement fusion (MCF) and inertia confinement fusion (ICF) blankets. In general, when a flow has a very thin momentum boundary layer on a hydrophobic or superhydrophobic wall, the flow experiences a “flow slip” on the wall. In a MCF blanket such as a dual-coolant or self-cooling liquid metal blanket, a liquid metal flow under a strong plasma-confining magnetic field is affected by the magnetohydrodynamic (MHD) force, so that the very thin momentum boundary layers form on the walls of the flow channel perpendicular to the strong magnetic field (so called Hartmann layer), whose thickness dHa in a strong magnetic field scales as 1/Ha. Here, the Hartmann number squared Ha2 expresses the ratio between the electromagnetic and the viscous forces in the field. A theoretical and numerical study has indicated liquid metal flows bounded by hydrophobic walls under a strong magnetic field may experience the flow slip at the wall, called as a MHD slip flow [1]. Eventually, it will affect on MHD flow instabilities, MHD pressure drop and, the heat and mass transfers in the fusion reactor blanket. The PbLi flows in channels of SiC in a dual coolant lead–lithium (DCLL) blanket are the typical examples of the above case. There are several experimental studies regarding the wettability of the molten PbLi to a SiC plate, which has qualitatively demonstrated the poor wettability over a long period of time [2]. However, there has not been quantitative research on the PbLi wettability until now. The present study is attempted to measure contact angles formed between molten PbLi and various SiC in order to develop a molten PbLi contact angle database. In addition to contribution to the MCF blanket research, an ICF blanket adopts a PbLi film flow along the SiC first wall [3, 4]. The PbLi contact angle database is necessary for the numerical studies of the molten PbLi film flow behaviors.

2 Contact Angle Measurement 2.1 Test Materials Test materials employed in the present study were a chemical vapor deposition (CVD) SiC (Rohm & Haas Company), a nano-infiltration and transient eutecticphase (NITE) SiC/SiC composite [5, 6] and a NITE SiC and a titanium (Ti) plate. It is anticipated that a dense CVD SiC seal coat will be applied on any SiC composite components in a fusion reactor blanket [7, 8]. The NITE SiC/SiC composite was fabricated with reinforcement using TyranoTM-SA SiC fiber cloth woven in 90° crossing two-dimensional (Ube Industrial Ltd., Japan). Ti was chosen as a reference

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Table 1  Surface roughness measurement results Unpolished (nm) Polished (nm) CVD SiC 122 12.5 NITE SiC/SiC 72.5 (Matrix) 21.3 (Matrix) 660 (Fiber) 127 (Fiber) NITE SiC N/A 21.5 Ti 346 47.8

Table 2  PbLi chemical composition before and after the contact angle measurement Pb (at%) Li (at%) Before measurement 84.2 15.8 After measurement 84.2 15.8

material because it is a wetting material of high-temperature ultrasonic Doppler velocimetry (HT-UDV) probe for the molten PbLi flows, and it has been reported the molten PbLi wets to Ti [9]. The contact angles can be affected by the droplet size and the surface conditions including the surface roughness. Unpolished and polished surfaces of the test materials were prepared. Their surfaces were observed by optical microscope and their surface roughness was measured by atomic force microscope (AFM). The surface roughness measured by AFM was shown in Table 1.

2.2 PbLi Chemical Composition The PbLi eutectic alloy was prepared by the Atlantic Metals & Alloys, Inc. The chemical composition of the PbLi alloy was examined by inductively coupled plasma-mass spectrometry (ICP-MS) shown in Table  2. The chemical composite was almost on the Pb–Li eutectic point (84.3 at% Pb & 15.7 at% Li) revised by Ok amoto [10]. The impurities existed under the detection limit of the inductively coupled plasma-Auger electron spectrometry (ICP-AES).

2.3 Droplet Preparation, Image Acquisition, and Image Analysis Preparation and making of the molten PbLi droplets were performed in an argonfilled glove box, where oxygen and humidity were controlled less than 1 ppm. In the glove box, a PbLi ingot was melt in a melt pot before removing the oxides floating on the liquid surface by using a metallic mesh. Molten PbLi droplets were formed on a stainless steel plate at room temperature by pipette so that the globules immediately got solidified. Then some droplets of the appropriate size were

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Fig. 1  Molten PbLi droplet on a CVD SiC

selected for the following contact angle measurement. The solidified PbLi droplet was put on a test material heated from below with an electric heater so that the solidified PbLi droplet was melt and became a molten PbLi droplet on the test material. After confirming the PbLi melted, the PbLi droplets images were taken by a digital camera installed outside of the glove box. The bulk temperature of the PbLi droplet was determined by measuring the PbLi temperature by inserting a thermocouple into the PbLi droplet after taking the image. The digital images of the PbLi droplets were analyzed to measure the contact angles using the interface analysis software: FAMAS (Kyowa Interface Science Co., Ltd.). In this study, we employed the tangential line method to determine the contact angle; since the trace line of the droplet surface from the contact line where the three phases (gas, liquid and solid) meet was too steep, the q/2 method could not be applied to the PbLi images. The tangential trace line of the PbLi droplet was determined based on the circles calculated from three surface-tracing markers on the droplet surface. The tangential line was then used to determine the contact angle (e.g. Fig. 1). The errors in the contact angle measurements mainly resulted from the inaccuracies in the contact line location. The horizontal error bars in the measurement results were made based on ±1 pixel horizontal displacements from the most probable position. The vertical error bars in the measurement results were due to the initial measurement errors in the thermocouples. Even though the PbLi droplets were formed in the inert glove box, some very small solid particles got gathered on the droplet surface to form a solid shell about 5 min later. The solid particles significantly affect the contact angle measurement to prevent an accurate measurement. Therefore every PbLi droplet was replaced to another one after taking a droplet image.

3 Results and Discussion The contact angle formed between the molten PbLi and the various SiC as well as Ti was determined experimentally shown in Figs. 2–5. The molten PbLi does not wet to any kind of SiC in the present temperature range and the PbLi exposure time.

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Fig. 2  Contact angles for PbLi on NITE SiC

Fig. 3  Contact angles for PbLi on CVD SiC (Left: unpolished surface, Right: polished surface)

Fig. 4  Contact angles for PbLi on NITE SiC/SiC (Left: unpolished, Right: polished surface)

The contact angles are greater than 150° and therefore it is classified as a superhydrophobic. The present surface roughness has little effect on the contact angle in the present PbLi exposure time duration. In addition, the NITE SiC/SiC composite composition and microstructure have little effect on the contact angle shown in Fig. 2. It has been reported that a reactant adhesion layer was formed on the NITE SiC/SiC composite after the PbLi wetting at 900°C, for 1,000 h [2]. A contact angle formed between the molten PbLi and the reactant adhesion layer can differ from the

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Fig. 5  Contact angles for PbLi on Ti (Left: unpolished, Right: polished surface)

initial contact angle. It has been reported the molten PbLi wetted to Ti [9]. However, the initial PbLi wettability to Ti is almost the same as the wettability to the SiC surfaces. Smaller contact angle would be expected to form between the molten PbLi and Ti after longer-time PbLi exposure due to the PbLi corrosion.

4 Conclusion The contact angles formed between molten PbLi and various SiC were determined experimentally. 1. Any combinations of the molten PbLi and the various SiC show the superhydrophobic as the initial PbLi wettability in the present temperature range as well as the wettability to Ti. 2. The present surface roughness has little effect on the contact angle. However, it is expected that the contact angles would be affected by the surface roughness if the PbLi corrosion occurs. 3. The NITE SiC/SiC composite composition and microstructure have little effect on the contact angle in the present condition. However, it is also expected that the initial wettability may change after a longer-time/higher-temperature PbLi exposure because of the reactant adhesion layer. Acknowledgments  The authors were grateful for the support of the Ministry of Education, Culture, Sports, Science and Technology of Japan via “Energy Science in the Age of Global Warming” of Global Center of Excellence (G-COE) program (J-051).

References 1. Smolentsev S (2009) MHD duct flows under hydrodynamic “slip” condition. Theor Comput Fluid Dyn 23:557–570 2. Park C, Noborio K, Kasada R, Yamamoto Y, Nam G, Konishi S (2009) Compatibility of materials for advanced blanket with liquid LiPb, Fusion Engineering, SOFE 2009. 23rd IEEE/ NPSS symposium, pp 1–4

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3. Kozaki Y (2006) Power plant concepts and chamber issues for fast ignition direct-drive ­targets. Fusion Sci Technol 49:542–552 4. Kunugi T, Nakai T, Kawara Z, Norimatsu T, Kozaki Y (2008) Investigation of cascade-type falling liquid-film along first wall of laser-fusion reactor. Fusion Eng Des 83:1888–1892 5. Katoh Y, Dong SM, Kohyama A (2002) Thermo-mechanical properties and microstructure of silicon carbide composites fabricated by nano-infiltrated transient eutectoid process. Fusion Eng Des 61–62:723–731 6. Katoh Y, Kohyama A, Nozawa T, Sato M (2004) SiC/SiC composites through transient eutectic-phase route for fusion applications. J Nucl Mater 329:587–591 7. Pint BA, Moser JL, Tortorelli PF (2008) Liquid metal compatibility issues for test blanket modules. Fusion Eng Des 81:901–908 8. Jones RH, Giancarli L, Hasegawa A, Katoh Y, Kohyama A, Riccardi B et al (2002) Promise and challenge of SiCf/SiC composite for fusion energy application. J Nucl Mater 307–311:1057–1072 9. Ueki Y, Hirabayashi M, Kunugi T, Yokomine T, Ara K (2009) Acoustic properties of Pb-17Li alloy for ultrasonic Doppler velocimetry. Fusion Sci Technol 56:846–850 10. Okamoto H (1993) Li-Pb (lithium-lead). J Phase Equil 14:770

Comparison of Operation Characteristic in Radiation Detectors Made of InSb Crystals Grown by Various Methods Yuki Sato, Tomoyuki Harai, and Ikuo Kanno

Abstract  We grew InSb crystal by the zone melting (ZM) method, and fabricated a Schottky-type radiation detector with the ZM grown InSb crystal. The energy peak of 5.5 MeV alpha particles of 241Am was observed for the first time by using the ZM grown InSb crystal. In addition, the comparisons of response characteristics with the ones of previously fabricated detectors made of InSb crystals grown by liquid phase epitaxy method and Czochralski method for 5.5 MeV alpha particles are described. Keywords  InSb • Radiation detector • X-ray fluorescence analysis • Zone melting method

1 Introduction To maintain our modern life, industrial products have been manufactured with using mined metals. The waste products have been deposited in the land, except some kinds of metals such as iron. We should re-use the processed metals as much as possible, to preserve environment and to decrease CO2 exhaust. For these purpose, improvement of analysis technique of metals in waste products is very important. X-ray fluorescence analysis is a powerful and widely employed method for this purpose. Therefore, the performance improvement of the X-ray fluorescence analysis contributes to the increase of the recycling rate. As a result, the X-ray fluorescence analysis with high performance contributes to the reduction of CO2 exhaust. For the performance improvement of the X-ray fluorescence analysis, X-ray radiation detectors with higher energy resolution and higher detection efficiency Y. Sato (*), T. Harai, and I. Kanno Graduate School of Engineering, Kyoto University, Kyoto 606-8501, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_37, © Springer 2011

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than the ones of conventional Si detectors are necessary. Compound semiconductor InSb is a promising substrate due to its high atomic numbers (In: 49, Sb: 51), high density (5.78 g/cm3), and the smallest band gap energy (0.165 eV) among the developed semiconductors. These features predict higher photon absorption efficiency (more than 1,000 times higher than that of Si), and twice better energy resolution than those of Si detectors [1]. In the previous work, we described on the fabrication of Schottky-type InSb radiation detector using a liquid phase epitaxially (LPE) InSb crystal. The energy resolution of the Schottky-type LPE InSb detector was ~3% for 5.5  MeV alpha particles of 241Am [2]. In addition, we also observe the photopeak of gamma rays emitted by 133Ba [2]. Apart from the LPE InSb crystal, Schottky-type radiation detectors were fabricated by using the InSb crystal grown by zone melting (ZM) method. In this paper, the result of detecting alpha particles of 241Am by the detector is reported. We also describe the comparison of response characteristics of InSb radiation detectors made of InSb crystals grown by ZM, LPE and Czochralski method for 5.5 MeV alpha particles of 241Am.

2 Experiment 2.1 InSb Crystal Growth The InSb crystal was grown by zone melting method. The schematic drawings of the (a) purification process and (b) crystallization process are shown in Fig. 1. In the purification process, two quartz ampoules, i.e., the inner ampoule and outer ampoule were used. The In and Sb raw materials (Osaka Asahi Co., LTD., Japan) with the purity of 99.9999% were stacked in the inner quartz ampoule, and this ampoule was inserted in the outer ampoule with H2 at the pressure of 0.5 atm. The inner and outer diameters of the inner ampoule were 7 and 10 mm, and the ones of the outer ampoule were 15 and 17 mm, respectively. The ring heater moved horizontally along the outer ampoule with the heater velocity of 5 cm/h. The purification process was repeated 200 times. In the crystallization process, the ampoule was set in the vertical direction. The inner and outer diameters of the ampoule were 15 and 17 mm, respectively. The middle part of purified InSb crystal was sealed in the ampoule with Ar + H2 (5%) at the pressure of 0.5 atm. The ring heater moved up along the ampoule only once with the heater velocity of 1 mm/h.

2.2 Hall Measurements of the ZM InSb Crystal For the estimation of the electrical properties of the ZM InSb crystal, Hall measurements were carried out. The InSb crystal grown by ZM method was cut to the

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thickness of 2 mm. For rough lapping and the final lapping of InSb wafers, 9 mm and 3  mm diameter diamond slurries were used, respectively. After lapping, the InSb wafer was mounted on the BN plate, and was placed on a sample holder of a cryostat (Helitran LT3: Advanced Research Systems, Inc., U.S.A.). Four gold wires were In soldered to the InSb wafer as electric leads. These electrodes were arranged in the corners of a virtual rectangle. The gold wires were connected to four terminals on the sample holder. The measurements were performed using a Hall measurement system (ResiTest 8340: Toyo Corporation, Japan).

2.3 Detector Fabrication A radiation detector was fabricated using a InSb wafer with 2 mm thickness. The 1 mm diameter electrode was defined by photoresist. Both sides of the wafer were etched using a mixture of hydrogen fluoride, hydrogen peroxide and ethylene ­glycol (48%HF:H2O2:C2H6O2 = 1:1:10). As described below, the ZM InSb crystal showed a p-type conductivity at temperatures below 150  K. Therefore, Al was

Comparison of Operation Characteristic in Radiation Detectors Made of InSb Crystals Fig. 2  Schematic drawing of the ZM InSb detector

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deposited by heat evaporation to the thickness of approximately 300 Å as a ­rectifying contact. The other side of the wafer was heat evaporated with In to a thickness of about 120 nm as an Ohmic contact. The wafer was mounted on the BN holder. A schematic drawing of the InSb detector is shown in Fig. 2. The properties and fabrication process of previously fabricated InSb detectors are also shown in Table 1.

2.4 Alpha Particle Measurements For the measurements of the responses of the InSb detector to 5.5 MeV alpha particles from 241Am, the detector was mounted on the sample holder of a liquid-He flow cryostat that was used for the Hall measurements. A 241Am source (5 kBq) was installed on the inside of a cryostat window blank. The distance between this source and the detector was about 15 mm. The temperature of the sample holder with the detector was 4.3  K. The preamplifier output and energy spectrum for the 241Am alpha particles were measured by a digital storage oscilloscope and a multichannel analyzer, respectively. The detailed experimental setup was described in [2]. These measurements were carried out without applying bias voltage because of the electric noise.

3 Results and Discussion 3.1 Electrical Properties of the ZM InSb Crystal The electrical properties of the ZM InSb crystal are shown in Fig.  3, which also shows the ones of LPE InSb crystal and Czochralski (commercial) InSb crystal (Wafer Technology). The Hall measurements indicated that the ZM crystal and LPE crystal were p-type up to 100 K. Because of the holes with low drift mobility, the Hall mobilities of the ZM crystal and LPE crystal were smaller than the one of the

Table 1  Summary of the properties and fabrication processes of InSb detectors Growth method Conducting type Supplier Etchant ZM P (<150 K) Authors 48%HF:H2O2:C2H6O2 = 1:1:10 LPE P (<140 K) Authors 48%HF:H2O2:H2O = 1:1:3 Czochralski N W.T. 48%HF:H2O2:H2O = 1:1:3 W.T.: Wafer Technology, England Electrode diameter 1 mm 1 mm 3 mm

Rectifying contact metal Al Al Au

Ohmic contact metal In (heat evaporation) In solder In solder

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n-type Czochralski crystal as shown in Fig. 3a. The resistivity of the ZM crystal was more than one order of magnitude higher than ones of the other crystals up to 100 K as shown in Fig. 3b. The Hall mobility of the ZM crystal was, however, very low. It is expected that the ZM crystal contains a lot of defects, and has the incomplete crystallity. In addiation, the carrier concentration of the ZM crystal was larger than the ones of the other crystals as shown in Fig. 3c. The purification effect of zone melting method was not observed much.

3.2 Energy Spectra of Alpha Particles The energy spectra of the 5.5  MeV alpha particles measured by using the InSb detectors made of the (a) ZM InSb crystal, (b) LPE InSb crystal, and (c) Czochralski InSb crystal were shown in Fig. 4. The energy resolutions of these detectors were (a) 24%, (b) 1.6%, and (c) 5%, respectively. The fabrication process of the LPE InSb detector used in Fig. 4b is the same with the one of [2]. The energy resolution

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and the signal-to-noise ratio of the ZM InSb detector are worse than ones of other detectors. As a result of Hall measurements, it was suggested that the ZM crystal has the incomplete crystallity and a lot of impurities. Therefore, the generated electrons and holes by alpha particle irradiation are lost by trapping on defects and by recombination with thermal excited carriers.

3.3 Preamplifier Output Pulses Examples of preamplifier output pulses from the InSb detectors made of the (a) ZM InSb crystal, (b) LPE crystal, and (c) Czochralski InSb crystal are shown in Fig. 5. The output polarity of the InSb detector made of a n-type Czochralski crystal is different from the ones of other detectors made of p-type InSb crystals because the output signals are read out from the rectifying contact electrodes on n-type and p-type InSb crystals, respectively. The typical amplitude of the preamplifier output pulses of the 5.5 MeV alpha particles were approximately (a) 60 mV, (b) 100 mV, and (c) 50 mV, respectively. Clearly, the output pulse of the LPE detector can be identified in two parts, i.e., the rapid part (<50 ns) and the slower part (>50 ns). The rapid and slower part are due to the contribution of electrons and holes, respectively. In the Czochralski InSb detector and ZM InSb detector, however, the slower parts (>50 ns) are not exited. Therefore, there is a possibility that the holes with smaller mobility has disappeared by recombinations and captures.

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4 Conclusion We succeeded in the observation of 5.5 MeV alpha particles using the ZM grown InSb crystal for the first time. However, the experimental results show the grown ZM InSb crystal has the incomplete crystallity and greater amounts of impurities than the LPE InSb crystal and Czochralski InSb crystal. To improve the energy resolution and signal-to-noise ratio of the ZM InSb detector, establishing the control techniques of crystallity and decreasing the amounts of defects and impurities are necessary. Acknowledgment  This work was supported by the Kyoto University Global COE Program “Energy Science in the Age of Global Warming”.

References 1. McHarris Wm C (1986) Nucl Instrum Methods Phys Res A 242:373 2. Sato Y, Morita Y, Harai T, Kanno I (2010) Nucl Instrum Methods Phys Res A 621:383

Specimen Size Effects on Fracture Toughness of F82H Steel for Fusion Blanket Structural Material Byung Jun Kim, Ryuta Kasada, Akihiko Kimura, and Hiroyasu Tanigawa

Abstract  Fusion energy has been considered to contribute to reducing emission of carbon dioxide effectively. Understanding and evaluating the fracture toughness behavior of neutron-irradiated reduced-activation ferritic (RAF) steels are essential in the design and operation of fusion reactor. In order to produce an enough database of irradiation effects on materials, the reduction of the specimen volume is required to acquire an enough number of data points. In the ITER Broader Approach (BA) project, applicability of small specimen test techniques (SSTT) has been examined to evaluate irradiation-induced degradation of fracture toughness of F82H steel. The master curve method, which was provided by the American Society for Testing and Materials (ASTM), is specified as a standard test method for determination of reference temperature for ferritic steels in the transition range. Fracture toughness tests were carried out for F82H steel in order to evaluate the effects of specimen size on the shift of transition curve using the various sizes of specimens (1 CT, 1/2 CT and 1/4 CT). The master curve approach was made for evaluation of fracture toughness of F82H with subsized specimens with constraint loss by referring to the ASTM E1921. Small specimen tests can be applicable to evaluate the fracture toughness of F82H steel with no substantial effect of specimen size. Keywords  F82H • Fracture toughness • Master curve • Small specimen test techniques • Specimen size effect

B.J. Kim (*), R. Kasada, and A. Kimura Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan e-mail: [email protected] H. Tanigawa JAEA, Tokai, Ibaraki, Japan T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_38, © Springer 2011

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1 Introduction Fusion energy has been considered to contribute to reducing emission of carbon dioxide effectively. Understanding and evaluating the fracture toughness behavior of neutron-irradiated reduced-activation ferritic (RAF) steels are essential in the design and operation of fusion reactor. Reduced-activation ferritic (RAF) steels are the promising candidate structural material for fusion reactor blanket components. Understanding and evaluating the ductile to brittle transition behavior and fracture toughness of RAF steels are critical in the design and operation of the reactor. In order to effectively produce irradiation database, the reduction of the specimen volume is required. The development and application of small specimen test techniques (SSTT) has enabled the evaluation of fusion materials at limited irradiation space. In the ITER Broader Approach (BA) project, applicability of small specimen test techniques has been examined to evaluate irradiation-induced degradation of fracture toughness of F82H. In the most recent, SSTT have been pursued within the framework of the master curves-shift method, which was proposed by Odette and coworker [1–3] for bcc alloys and currently being considered as candidate method for fusion reactor structures. The master curve method [4] is specified as a standard test method for determination of reference temperature for ferritic steels in the transition range provided by the American Society for Testing and Materials (ASTM). The MC method is indexed at a reference temperature T0 at a specific toughness usually equal to 100  MPa m1/2. T0 is a material dependent parameter. The main advantage of the method is the reduction of the requirements for fracture toughness testing in terms of both the size and number of specimen. However, the application of the method to RAF steels may have some difficulty passing the requirement of method, for example, large constraint loss in small specimens of RAF steels and possible fracture mode change to intergranular due to precipitation of transmutation helium at grain boundaries [5–9]. In the present study, fracture toughness behavior was investigated for F82H with different size of specimen in order to evaluate the effects of specimen size on the shift of transition curve. We have discussed and determined the work flow to evaluate validity of master curve (MC) method for quantification of fracture toughness behavior of F82H using the different size specimen (1 CT, 1/2 CT and 1/4 CT).

2 Experimental The material used was a reduced activation ferritic steel, F82H-BA07, of which the chemical compositions and heat treatment conditions are shown in Table  1. The standard heat treatment for F82H-BA07 was two step normarizing at 1040°C for 40 min and 960°C for 30 min followed by an air cooling (normalization treatment). The fracture toughness tests were carried out in accordance with ASTM E 1921-02 standard test method for determination of reference temperature, T0, for ferritic steels in

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Table 1  The chemical compositions of tested materials in wt% Materials C Si Mn P S Cr F82H-BA07 0.09 0.11 0.16 0.002 0.002 8.00

W 1.88

V 0.19

Ta 0.02

Fig. 1  Configurations of the CT specimens used in this study

the transition range. The unloading compliance method was applied for measuring the J integral with a clip strain gage. In this study, the fracture toughness was measured for various size specimens (1 CT, 1/2 CT and 1/4 CT). The dimension of the CT specimen was shown in Fig. 1. Fatigue pre-cracking was induced to a ratio of the pre-crack length to specimen width of about 0.55, followed by side grooving by 20% of thickness. Master curve (MC) method is very useful to evaluate shift of ductile–brittle transition temperature by using limited number of small specimens. The following is a brief description of the master curve method. Values of J-integral at critical cleavage fracture instability, JC, were converted to their equivalent values in terms of stress intensity factor KJC by the following equation:

K Jc = J C

E 1 − v2

(1)

where E is Young’s modulus and v = 0.29 is Poisson’s ratio. The KJC value was considered invalid if it exceeded the validity limit:

K Jc(limit) =

Eb 0s YS M(1 − v2 )

(2)

where b0 is the ligament size, sYS is yield strength of the material and M is the constraint factor defined as M = 30 in the ASTM 1920. All JC data were converted to 1 T equivalence to KJC(1T), using the weakest link size adjustment procedure of ASTM E 1921:  BxCT 1/b    K = K + K − K (3) Jc(1T) min min     Jc (xT )  B1CT  where Kmin = 20 Mpa m1/2 is the minimum of KJC, BXCT the gross thickness of 1CT specimen and b = 4 is the parameter based on Weibull model [4]. The data were

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analyzed within the framework of statistical brittle fracture model that yield, for highly constrained specimens, the cumulative failure probability as a three-­ parameter Weibull distribution:   K − K  b  Jc min p 1 exp = − (4) −    f K K − min     0  The temperature dependence of the median toughness of 25.4 mm thick specimen (1 T) in the transition region of ‘ferritic’ steels is given by a so-called ASTM master curve as follow: K Jc(med) = 30 + 70 exp[0.019(T − T0 )]



(5)

where, the reference temperature T0 corresponds to the temperature where the median fracture toughness for a 25  mm thick specimen has the value 100 MPa m1/2. The T0 is estimated from the size adjusted KJC data using a multi-temperature randomly censored maximum likelihood expression (6).

4 n (K d i ·exp{0.019·[Ti − T0 ]} ICi − 20) ·exp{0.019·[Ti − T0 ]} − = 0 (6) ∑ ∑ 5 i = 1 11 + 77·exp{0.019·[Ti − T0 ]} i = 1 (11 + 77·exp{0.019[Ti − T0 ]}) n

The reference temperature (T0) is solved iteratively from (6). This method is well illustrated by ASTM E 1921 [4].

3 Results and Discussion F82H steels have been tested to evaluate the effect of specimen size in the transition region. Figure 2 shows the test temperature dependence of the KJC(1T) obtained for F82H for the 1 CT, 1/2 CT and 1/4 CT specimen. The KJC(for 1CT) were converted from KJC(1T) data of the 1/2 CT and 1/4 CT specimen by using (3). The figure also showed the calculated 5 and 95% tolerance bounds. The reference temperature, T0, for AS-TL specimen data for 1 CT data is determined to be −113.1°C in Fig. 2a. The reference temperature (T0,) of 1/2 CT and 1/4 CT were obtained by −100.2 and −107.9°C respectively in from Fig. 2b, c. ASTM limit curve is increased with specimen size due to increasing the ligament size (b0) in (2). Figure 2d shows the effect of specimen size for 1 CT, 1/2 CT and 1/4 CT specimen. The reference temperature (T0) of 1/4 CT which is the smallest specimen among different size samples (1CT, 1/2 CT and 1/4 CT) existed between 1 CT and 1/2 CT reference temperature. In our result, fracture toughness of F82H steels (as-received condition) is independent of specimen size. Small specimen tests can be applicable to evaluate the fracture toughness of F82H steel with no substantial effect of specimen size. Figure 3 shows the conventional master curve analysis of F82H data. The reference temperature (T0) was obtained by −107.6°C which has similar values to that

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Fig. 2  The KJC of F82H for 1CT converted from the data obtained with 1 CT, 1/2 CT and 1/4 CT and the corresponding master curve; (a) 1CT (AS-TL), (b) 1/2 CT (AS-TL), (c) 1/4 CT (AS-TL) and (d) specimen size effect (total)

Fig. 3  Conventional master curve analysis of F82H-BA07 data

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of previous data calculated by Odette and other people [9]. A large number of data points fall outside the 5% and 95% tolerance bounds; and at a lower temperatures many fall below the 5% bound.

4 Conclusions Fracture toughness behavior was investigated for F82H with different size of specimen (1 CT, 1/2 CT and 1/4 CT) in order to evaluate the effects of specimen size on the shift of transition curve. The conclusions are summarized as follows: 1. Small specimen test technique for F82H steels can be applicable to evaluate the fracture toughness properties due to no substantial effects of specimen size. 2. The reference temperature (T0) of F82H steels has similar values to that of ­previous data which is calculated by Odette and other people. Acknowledgements  The present study includes the result of “Broader Approach” project. The authors would like to express their gratitude to Kyoto University Global COE program “Energy Science in the Age of Global Warming” for funding to participate in the Second International Symposium on Global COE Program of Kyoto University.

References 1. Odette GR, Yamamoto T, Rathbun HJ, He MY, Hribernik ML, Rensman JW (2003) Cleavage fracture and irradiation embrittlement of fusion reactor alloys: mechanisms, multiscale models, toughness measurements and implications to structural integrity assessment. J Nucl Mater 323:313–340 2. Sokolov MA, Tanigawa H (2007) Application of the master curve to inhomogeneous ferritic/ martensitic steel. J Nucl Mater 367–370:587–592 3. Bonadé R, Spätig P, Baluc N (2007) Fracture toughness properties in the transition region of the Eurofer97 tempered martensitic steel. J Nucl Mater 367–370:581–586 4. ASTM E1921-02 (2002) Standard test method for determination of reference temperature, T0, for ferritic steels in the transition range. In: Annual book of ASTM standards, vol 03.01. ASTM, West Conshohocken 5. Tong Z, Dai Y (2009) Tensile properties of the ferritic martensitic steel F82H after irradiation in a spallation target. J Nucl Mater 385:258–261 6. Ando M, Tanigawa H, Wakai E, Stoller RE (2009) Effect of two-steps heat treatments on irradiation hardening in F82H irradiated at 573 K. J Nucl Mater 386–388:315–318 7. Klueh RL, Vitek JM (1991) Tensile properties of 9Cr-1MoVNb and 12Cr-1MoVW steels irradiated to 23 dpa at 390 to 550°C. J Nucl Mater 182:230–239 8. Mueller P, Spätig P (2009) 3D finite element and experimental study of the size requirements for measuring toughness on tempered martensitic steels. J Nucl Mater 389:377–384 9. Odette GR, Yamamoto T, Kishimoto H, Sokolov M, Spätig P, Yang WJ, Rensman J-W, Lucas GE (2004) A master curve analysis of F82H using statistical and constraint loss size adjustments of small specimen data. J Nucl Mater 329:1243–1247

Tensile Behavior of Transient Liquid Phase Bonded ODS Ferritic Steel Joint Sanghoon Noh, Ryuta Kasada, and Akihiko Kimura

Abstract  The oxide dispersion strengthened (ODS) steel is one of the candidate structural materials for Gen. IV systems and DEMO reactor systems because of its excellent elevated temperature strength, corrosion and radiation resistance. Joining technology development of ODS steels is unavoidable to realize these advanced nuclear systems with huge and complex structures. However, joining of ODS steels with conventional melting–solidification processes is considered to cause detrimental effects on joint regions because of the possible modification of the fine homogeneous microstructure to rather coarse and inhomogeneous microstructure. Therefore, suitable joining techniques need to be developed with such a process that these featured microstructures are reasonably maintained after the processes. In this study, tensile behavior of TLPB ODS steel joint was investigated. Thin pure boron insert material was deposited by electron beam physical vapor deposition (EBPVD) to join ODS steel (Fe–15Cr–2W–0.2Ti–0.35Y2O3) blocks using uniaxial hot press. ODS steel was successfully bonded with free of voids at bonding interface with EBPVD bond. Tensile strength of the joint is similar with the base materials, while total elongation is decreased at 700°C accompanied by fracturing at the joint interface. The fracture is considered to be due to partial discontinuous microstructures aligned along the interface. Keywords  Oxide dispersion strengthened steel • Pure boron • Tensile behavior • Transient liquid phase bonding

S. Noh (*) Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto, Japan e-mail: [email protected] R. Kasada and A. Kimura Institute of Advanced Energy, Kyoto University, Gakasho, Uji, Kyoto, Japan T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_39, © Springer 2011

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1 Introduction The oxide dispersion strengthened (ODS) steel is one of the candidate structural materials for Gen. IV fission systems and fusion DEMO reactors because of its excellent elevated temperature strength, corrosion and radiation resistance [1–3]. Welding and joining on ODS steels are considered to be an important issue to ­realize these advanced nuclear systems with huge and complex structure. However, joining of ODS steels with conventional melting–solidification processes is considered to cause detrimental effects on joint regions because of the possible modification of the microstructure from very small grain size with homogeneously distributed nano-oxide particles in the matrix to rather coarse and inhomogeneous microstructure. Therefore, suitable welding and joining techniques need to be developed with such a process that these featured microstructures are reasonably maintained after the processes [4]. Transient Liquid Phase Bonding (TLPB) is one of the potential joining processes to minimize the disruption of these microstructures at the interface. This process requires an insert material between two materials to be bonded and its joint is formed when a melting point depressant (MPD; B, Si, P, C and Hf in bonding steels) in the insert material diffuses into the base metal and localized melting and solidification occurred in the process [5]. In this study, TLPB was employed to join ODS steel blocks using a commercial amorphous insert foil based on Fe–3B–5Si compositions and electron beam ­physical vapor deposited (EBPVD) pure boron. Then, the microstructures and ­tensile behavior on the joint region were investigated to evaluate the applicability of TLPB to ODS ferritic steel joining.

2 Experimental The ODS ferritic steels (ODS-FS) used as base metal in this study is Fe (bal.)–15Cr– 2W–0.2Ti–0.35Y2O3. The ODS-FS was fabricated by mechanical alloying and hot extrusion process. As insert materials, commercial amorphous foil (Fe (Bal.)–3B–5Si, #2605S-2, 25 mm, METGLAS®) and pure boron were used for TLPB process. To determine the bonding temperature in using the amorphous foil, thermogravimetry-differential thermal analysis (TG-DTA) was carried out and its result is shown in the previous paper [6]. Thus, the temperature range showing maximum endothermic peaks is the melting point (Tm) of insert material, which means the insert material begins to transform to liquid phase above 1,180°C. Meanwhile, pure B thin layer was induced by electron beam physical vapor deposition (EBPVD) technique. A substrate (an ODS-FS block to be bonded) and target material (pure B grains, 99.5% purity, 3–7 mm, KOJUNDO Chem. Lab. co.) were vertically located in high vacuum atmosphere (<1.2 × 10−3 Pa). The electron beam was ­discharged to B target in a condition of 7  kV, 180  mA for 15  min. The test pieces were cut into 20 × 12 × 12 mm3 and surfaces to be bonded were buff-polished. Samples were stored in the acetone for cleaning and preventing the surface ­contamination. For diffusion

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bonding process, hydrostatic vacuum hot press was used in this study. Two ODS-FS blocks with an insert material were vertically placed and assembled with the carbon sleeves. This assemblage was located between pressing punches and linearly heated up to bonding temperature, 1,200°C in a heating rate of 30°C/min. Then, the bonding temperature was held for 1 h in a high vacuum atmosphere (<5 × 10−4 Pa) under hydrostatic pressure of 25 MPa in uni-axial compressive loading mode. After the bonding process, the hydrostatic pressure was relieved and the samples were cooled in the furnace. In this study, two ODS-FS were bonded in a longitudinal direction, so that the joint interface is perpendicular to the extruded direction. Tensile tests performed at a temperature range from room temperature to 700°C at a strain rate of 6.67 × 10−4 s−1 in a high vacuum atmosphere (5 × 10−5 torr).

3 Results and Discussions ODS-FS blocks were successfully diffusion bonded at 1,200°C for 1 h. The surfaces of the bonded sample showed no trace of macroscopic deformation under the hydrostatic pressure of 25 MPa, which is in agreement with the report that the threshold stress for the surface deformation of commercial ODS alloy, Inconel MA956, is about 60 MPa [7]. The cross sectional microstructures of TLPB ODS-FS joint region are shown in Fig. 1. In the TLPB joint with an amorphous foil, the residual insert material of about 15 mm thickness was found and located horizontally in the Fig. 1a. Amorphous insert material was melted and crystallized during bonding process. To investigate the diffusion behavior of elements, EPMA analysis was done for joint regions. Color maps show peaks of each element amount in the area for comparative intensity level, as indicated in Fig. 2. In Fig. 2a remarkable element map differences were observed between Si and B in TLPB joint with amorphous foil; Si was diffused out up to about 100 mm into base metals during bonding process and B was distributed homogeneously because of its rapid diffusion rate in Fe at the bonding temperature. It is interesting that Cr was also concurrently diffused from base metals to residual insert material. This means the

Fig. 1  Cross sectional microstructures of TLPB joint with (a) amorphous foil and (b) EBPVD B as the insert layer (note the different magnifications)

Fig. 2  Elemental distributions of (a) joint region of TLPB with amorphous foil, (b) bonding interface of TLPB with amorphous foil and (c) bonding interface of TLPB with EBPVD B

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homogenization on chemical composition at the joint interface has been completed ­during the TLPB process. Some precipitates exist at the interface of ODS-FS and insert material, although no grain growth occurred in joint region and base material. Some precipitates existed at the interface are considered to be Y–Ti–O complex based on the EPMA analysis, although the yttrium concentration is low and indistinguishable as shown in Fig. 2b. These precipitates come from dissolution of base metal due to diffusion of the melting point depressants during TLPB process. On the other hand, some recrystallized grains were observed at the bonding interface of TLPB ODS-FS with EBPVD boron as shown in Fig. 1b. It is evident that ODS-FS matrix near the interface was temporarily melted by diffusion of pure B into the base metal contacted with EBPVD boron during the bonding process. There is no trace of the existence of eutectic phase or metallic phase such as iron or chromium borides. However, some coarsened precipitates were observed in recrystallized grains at the bonding interface. These agglomerated precipitates are revealed as Y–Ti–O complex oxide by EPMA analysis in Fig. 2c. This indicates that the base metal was dissolved by holding MPD in solution, which was induced by diffusion of pure B into the base material. In the same manner with TLPB using Fe–3B–5Si amorphous foil, it is certain that these recrystallized grains and was fairly good on TLPB joint region with EBPVD B. The results of tensile tests of base metals and TLPB joints at elevated temperatures are shown in Fig. 3. Through the all temperature tested, TLPB joint regions showed high ultimate tensile strengths (UTS), which were up to 90% of base material. In TLPB joint with amorphous foil, the reduction of total elongation (TE) was also observed at elevated temperatures, which reduced to 30% of that of base metal at 700°C, even though TE of base metal increased slightly at 700°C. However, there was a similarity in the tensile behavior of the TLPB joint region of EBPVD boron with base material at 600°C, although it decreased at 700°C. In Fig. 4, fractography o­ bservation

Fig. 3  Tensile test results of base material and TLPB joints at elevated temperature

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Fig. 4  Fractographs of TLPB joint regions after tensile test

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revealed that base metals show typical necking behavior with significant reduction of area. As for TLPB joint with amorphous foil, all failures were occurred at the interface of base metal/insert material showing a mixture mode of micro-void coalescence and cleavage. It seems that Y–Ti–O precipitates at bonding interface triggers micro-void formation and cracks at joint region with deformation. These micro-cracks propagated to interface boundaries of ODS-FS/insert material in brittle fracture mode. However, TLPB joints with EBPVD boron show significantly different fracture behavior, which is similar to base material showing necking with typical ductile fracture mode even at a hundred mm far from bonding interface at below 600°C. In coincided with a result of 700°C, the interfacial fracture was occurred with lower TE than that of base metal. However, it has a lot of micro-void coalescence with dimple fracture. While EBPVD B TLPB joint was elongated by grain-boundary sliding mechanism without area reduction in the beginning of tensile at 700°C, it finally fractured at the interface, because coarsened precipitates aligned at bonding interface produced the micro-void and then it linked each other.

4 Summary A high Cr ODS ferritic steel was bonded by TLPB with an amorphous foil (Fe–3B– 5Si) and EBPVD boron in high vacuum uni-axial hot press. Tensile tests were ­carried out to investigate the relationship between microstructure and mechanical property of the joint region. The obtained main results are as follows: 1. The TLPB ODS steel with Fe–3B–5Si amorphous foil showed rather homogeneous elemental distribution in the joint region, while Y–Ti–O complex oxide precipitates and residual insert material were observed at the interface. 2. The joints had a fairly good tensile strength that was up to 90% of base metal at 700°C. However, it showed poor elongation compared to base metal with ­showing fractures at the interface between insert material and ODS-FS. 3. On the other hand, TLPB joint with EBPVD boron has excellent tensile properties comparable to base metal with showing favorable fracture behavior far from bonding interface.

References 1. Ukai S, Okuda T, Fujiwara M, Kobayashi T, Mizuta S, Nakashima H (2002) Characterization of high temperature creep properties in recrystallized 12Cr-ODS ferritic steel claddings. J Nucl Sci Technol 39:872–879 2. Cho HS, Ohkubo H, Iwata N, Kimura A, Ukai S, Fujiwara M (2006) Improvement of compatibility of advanced ferritic steels with super critical pressurized water toward a higher thermally efficient water-cooled blanket system. Fusion Eng Des 81:1071–1076 3. Yamashita S, Akasaka N, Ukai S, Ohnuki S (2007) Microstructural development of a heavily neutron-irradiated ODS ferritic steel (MA957) at elevated temperature. J Nucl Mater 367–370:202–207

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4. Lindau R, Möslang A, Rieth M, Klimiankou M, Materna-Morris E, Alamo A, Tavassoli AAF, Cayron C, Lancha A-M, Fernandez P, Baluc N, Schäublin R, Diegele E, Filacchioni G, Rensman JW, Schaaf Bvd, Lucon E, Dietz W (2005) Present development status of EUROFER and ODS-EUROFER for application in blanket concepts. Fusion Eng Des 75–79:989–996 5. McDonald WD, Eagar TW (1995) Transient liquid phase bonding process. In: The metal science of joining 93–100 6. Noh S, Kasada R, Oono N, Iwata N, Kimura A (2009) In: The proceedings of the 9th international symposium on fusion nuclear technology 7. Singer RF, Arzt E (1986) Processing, structure and properties of ODS superalloys. In: Reidel D (ed) Proceedings of high temperature alloys for gas turbines and other applications, Dordrecht, Holland, p 97

Helium Ion Irradiation Effects in ODS and Non-ODS Ferritic Steels Ryuta Kasada, Hiromasa Takahashi, Kentaro Yutani, Hirotatsu Kishimoto, and Akihiko Kimura

Abstract  Irradiation-resistant materials R&D are one of the key issues to realize fusion power reactor because 14  MeV fusion neutrons will give severe degradation to the structural materials through significant displacement damage with a large amount of transmutation helium up to several thousand appm. When these helium atoms diffuse onto grain boundaries, it can lead to degradation of toughness through intergranular fracture. The present paper describes superior resistance of oxide dispersion strengthened (ODS) ferritic steels to the intergranular fracture due to helium. Dual-beam ion-irradiation technique was applied to reveal the helium effect on the microstructural evolution and mechanical property change of the ODS ferritic steels as well as of the non-ODS ferritic steels. Keywords  Fusion reactor • Helium effect • Ion-irradiation • Irradiation effect • Structural materials

1 Introduction Oxide dispersion strengthened (ODS) ferritic steels are expected to be used for the first-wall component in the fusion reactors [1–3]. In D-T burning fusion reactor environments, 14  MeV neutrons produce severe displacement damage and also cause nuclear reaction which may produce considerable concentrations of transmutation elements in the materials. In particularly, transmutation helium may play an important role to decide the lifetime of the structural components. Transmutation

R. Kasada (*) and A. Kimura Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan e-mail: [email protected] H. Takahashi and K. Yutani Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan H. Kishimoto Muroran Institute of Technology, Muroran, Hokkaido 050-8585, Japan T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_40, © Springer 2011

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helium atoms generated in the materials can diffuse onto grain boundaries because the inert gas helium is unsolvable in metals. Helium on grain boundaries can lead to degradation of toughness through intergranular fracture. In fact, a reduced-activation ferritic (RAF) steel showed ductile-to-brittle transition temperature (DBTT) shift and fracture mode change to intergranular fracture at low temperatures after helium ion implantation up to 1,000  appm using 50  MeV a-particles from a cyclotron accelerator [4]. In contrast, ODS ferritic steels showed no DBTT shift or fracture mode change after the helium implantation at same condition. This superior resistance of the ODS ferritic steels against intergranular fracture under the helium implantation is likely to be due to trapping of helium at the nano-oxide particles dispersed in the matrix [5, 6]. The present paper describes the different response of ODS ferritic steel and non-ODS RAF steel against the helium implantation using a dual-beam ion irradiation technique.

2 Experimental Procedure 2.1 Materials The ODS ferritic steels used in the present study are 9Cr-ODS ferritic steel [7]. The ODS ferritic steels were fabricated by mechanical alloying of elemental powders and yttria into an attritor ball mill machine. The consolidation of the mechanically alloyed powder was performed by hot-extrusion in an evacuated steel can. The 9CrODS steel were normalized at 1,323 K for 3.6 ks followed by air cooling and tempered at 1,073 K for 3.6 ks followed by air cooling. The non-ODS ferritic steel is a reduced-activation ferritic (RAF) steel F82H (IEA-heat) [8]. The chemical compositions are also given in Table 1. The RAF steel was produced by conventional vacuum melting process. The F82H steel was normalized at 1,313 K for 2.4 ks followed by air cooling and then was tempered at 1,023 K for 3.6 ks followed by air cooling.

2.2 Ion-Irradiation Dual-beam ion-irradiation experiments were carried out using the DuET facility at the Institute of Advanced Energy, Kyoto University. The DuET facility consists of

Table 1  The chemical composition in wt% of 9Cr-ODS and F82H Materials C Si Mn Cr W V Ta N F82H 0.09 0.11 0.16 7.71 1.95 0.16 0.02 0.006 9Cr-ODS 0.14 0.048 0.05 8.67 1.96 – – 0.017

Ti 0.01 0.23

Y2O3 – 0.34

Fe Bal. Bal.

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Fig. 1  Calculated depth profiles of displacement damage and helium concentration for the present condition

a 1.7  MV tandem accelerator and a 1.0  MV single-end accelerator. The DuMIS (Dual-beam materials irradiation station) is located at the cross-point of the beam lines from the both accelerators in order to irradiate simultaneously two species of ion to a sample. A rotating thin-foil type beam energy degrader is installed on the single-end accelerator beam line in the DuMIS to obtain constant helium-to-dpa ratios within a certain range of the irradiated materials. In the present study, 6.4 MeV Fe3+ ions are introduced to give displacement damage into the target material and energy-degraded 1.0 MeV He+ ions are simultaneously implanted into the target. The irradiation temperature was controlled at 823 ± 5  K with the infrared thermal vision. Figure  1 shows depth-profiles of displacement damage and implanted helium-ion calculated by the TRIM-98 code (http://www.srim.org/) assuming average displacement threshold energy of 40 eV. The nominal dose rate and dose at a depth of 600 nm below the specimen surface were 1 × 10−4 dpa/s and 0.4  dpa, respectively. Helium implantations were controlled up to 10, 100, and 1,000 appm in the averages at depth from 500 to 1,500 nm.

2.3 Post-Irradiation Experiments Thin foil specimens for transmission electron microscopy (TEM) were prepared by the focused ion beam (FIB) method followed by flash electro-polishing to remove the surface layer damaged by FIB. TEM observations were performed with a JEM2010 operated at 200 kV. Nano-indentation hardness was measured by using the Elionix Inc. Model ENT1100a with a Berkovich type indentation tip. Indentation depth was controlled up

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to 300 nm. Load and displacement were measured to obtain unloading compliance. Calibration of blunting of the indentation tip and calculation of hardness were based on the procedure proposed by Oliver and Pharr [9].

3 Results and Discussion 3.1 Microstructural Evolution As shown in Fig. 2a, TEM examination revealed that the unirradiated specimen of the 9Cr-ODS ferritic steel had fine particles with the diameter of about 5  nm. Ohnuma et al. carefully determined the nature of the particles in the 9Cr-ODS ferritic steel as Y2Ti2O7 using small-angle neutron scattering and small-angle X-ray scattering [10]. The unirradiated F82H shows a well-known tempered martensite structure. The microstructure after ion-irradiation was remarkably different between

Fig.  2  TEM-micrographs showing (a) nano-oxide particles in 9Cr ODS ferritic steel and the evolution of cavities in (b) F82H and (c) 9Cr ODS ferritic steel

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9Cr-ODS and F82H. A well-developed cavity microstructure was observed in the F82H, as shown in Fig. 2b. The cavities were preferentially located at dislocations, surface of precipitates, and grain boundaries. In contrast, the 9Cr-ODS ferritic steel contains smaller cavities which are homogeneously distributed with no preferential formation on grain boundaries, as shown in Fig. 2c. The preferential formation of cavities on the grain boundaries in F82H can explain the intergranular fracture observed in our previous study [4]. The 9Cr-ODS ferritic steel shows that bubbles are refined and are homogeneously distributed in the matrix. Helium atoms implanted into the ODS ferritic steels are likely trapped at the interface between nano-oxide particles and matrix [5, 6].

3.2 Mechanical Properties Figure  3 shows results of nano-indentation hardness tests for the ion-irradiated samples. The hardness changes in both the steels after ion-irradiation is small up to 1,000 appm He implantation. Our previous investigations for high-Cr ODS ferritic steels irradiated with single-ions (only Fe3+ ion) up to 10 dpa show that irradiation hardening occurred at the irradiation temperature of 573 K but not of 773 K [11]. The irradiation hardening at 573 K was due to a formation of dislocation loops. In contrast, no significant change was observed in the microstructure of the ODS steels

Fig.  3  Nano-indentation hardness of 9Cr-ODS and F82H after He-implantation. Dashed lines shows the hardness of unirradiated samples

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irradiated at 773 K. We, thus, conclude that effect of helium on the hardness change is negligible in the present conditions and the present results well explain the superior resistance of the ODS ferritic steels to the He-related intergranular fracture.

4 Conclusion The 9Cr-ODS ferritic steel and non-ODS F82H steel were irradiated at 773 K by means of a dual-beam ion irradiation technique to a dose of 0.4 dpa with simultaneous helium implantation up to 1,000 appm. The results obtained show that despite a preferential formation of cavities at grain boundaries, precipitate interfaces and dislocations in F82H, the 9Cr-ODS ferritic steel contains a homogeneous and fine distribution of cavities in the matrix. The hardness changes in both the steels after the ion-irradiation were negligible. These results well explain the superior resistance of the ODS ferritic steels to the He-related intergranular fracture.

References 1. Kimura A, Kasada R, Kohyama A, Tanigawa H, Hirose T, Shiba K, Jitsukawa S, Ohtsuka S, Ukai S, Sokolov MA, Klueh RL, Yamamoto T, Odette GR (2007) Recent progress in US–Japan collaborative research on ferritic steels R&D. J Nucl Mater 367–370:60–67 2. Norajitra P, Bühler L, Fischer U, Malang S, Reimann G, Schnauder H (2002) The EU advanced dual coolant blanket concept. Fusion Eng Des 61–62:449–453 3. Reiser J, Norajitra P, Ruprecht R (2008) Numerical investigation of a brazed joint between W-1%La2O3 and ODS EUROFER components. Fusion Eng Des 83:1126–1130 4. Hasegawa A, Ejiri M, Nogami S, Ishiga M, Kasada R, Kimura A, Abe K, Jitsukawa S (2009) Effects of helium on ductile–brittle transition behavior of reduced-activation ferritic steels after high-concentration helium implantation at high temperature. J Nucl Mater 386–388:241–244 5. Yutani K, Kishimoto H, Kasada R, Kimura A (2007) Evaluation of helium effects on swelling behavior of oxide dispersion strengthened ferritic steels under ion irradiation. J Nucl Mater 367–370:423–427 6. Kasada R, Takahashi H, Kishimoto H, Yutani K, Kimura A (2010) Superior radiation resistance of ODS ferritic steels. Mater Sci Forum 654–656:2791–2794 7. Ukai S, Fujiwara M (2002) Perspective of ODS alloys application in nuclear environments. J Nucl Mater 307–311:749–757 8. Klueh RL, Gelles DS, Jitsukawa S, Kimura A, Odette GR, Van der Schaaf B, Victoria M (2002) Ferritic/martensitic steels – overview of recent results. J Nucl Mater 307–311:455–465 9. Oliver WC, Pharr GM (2004) Measurement of hardness and elastic modulus by instrumented indentation: advances in understanding and refinements to methodology. J Mater Res 19:3–20 10. Ohnuma M, Suzuki J, Ohtsuka S, Kim S-W, Kaito T, Inoue M, Kitazawa H (2009) A new method for the quantitative analysis of the scale and composition of nanosized oxide in 9Cr-ODS steel. Acta Mater 57:5571–5581 11. Yutani K, Kasada R, Kishimoto H, Kimura A (2007) Irradiation hardening and microstructure evolution of ion-irradiated ODS ferritic steels. J ASTM Int 4, JAI100701

Thermal Conductivity of SiCf /SiC Composites at Elevated Temperature Youngju Lee, Yihyun Park, and Tatsuya Hinoki

Abstract  Silicon carbide fiber reinforced silicon carbide composites (SiCf/SiC composites) are one of the candidate materials for fusion reactors such as first wall and divertor due to their low activation, mechanical and chemical stability at elevated tem­perature. SiCf/SiC composites are required high thermal conductivity at elevated temperature to reduce heat load and to provide high thermal conversion efficiency. The purposes of this study are development of SiCf/SiC composites and determine of the thermal conductivity at elevated temperature. SiCf/SiC composites were fabricated by hot-press method. Sintering temperature and pressure of SiCf/SiC composites were 1,900°C and 20  MPa. Tyranno-SA fibers were used as reinforce materials. The bulk density of fabricated SiCf/SiC composites was measured by the Archimedes method with an immersion medium of distilled water. Thermal conductivity was calculated from the measured bulk density, thermal diffusivity and specific heat capacity. Thermal diffusivities and specific heat capacities of SiCf/SiC composites were measured by the laser flash method using a thermal analyzer. Thermal conductivity of SiCf/SiC composites in vacuum was measured temperature ranging from 25 to 1,200°C. The thermal conductivity of fabricated SiCf/SiC composites at room temperature was approximately 60 W/mK. The lower dense materials such as CVI-SiC/SiC composites have low thermal conductivity approximately 15 W/mK at room temperature due to high porosity in composites despite high thermal conductivity of matrix. But, the fabricated SiCf/SiC composites have high thermal conductivity due to densification and high thermal conductive matrix. Thermal conductivity of SiCf/SiC composites deceased with increasing temperature, since the frequency of phonon scattering increases with increasing temperature. Keywords  Fusion reactor • SiCf/SiC composites • Thermal conductivity

Y. Lee (*) Graduate School of Energy Science, Kyoto university, Gokasho, Uji, Kyoto 611-0011, Japan e-mail: [email protected] Y. Park and T. Hinoki Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_41, © Springer 2011

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1 Introduction Silicon carbide fiber reinforced silicon carbide composites (SiCf/SiC composites) are one of the candidate materials for fusion reactors such as first wall and divertor due to their low activation, mechanical and chemical stability at elevated temperature [1, 2]. SiCf/SiC composites are required high thermal conductivity at elevated temperature to reduce heat load and to provide high thermal conversion efficiency for fusion reactor. High energy conversion efficiency (50% or more) in fusion power reactors is anticipated by using SiCf/SiC composites as structure materials [2]. However, the nanoinfiltration and transient eutectic (NITE) process is a developed technique for silicide ceramic matrix composites for thermo-structural components in various applications [3]. The purposes of this study are development of SiCf/SiC composites with high thermal conductivity and determine of the thermal conductivity at elevated temperature.

2 Experimental 2.1 NITE Process The NITE process was developed for the reduced porosity, advanced matrix quality control and strong fiber–matrix interface. The NITE process incorporates an appropriate coating to the fiber surfaces for the fiber protection and the interphase deposition, infiltration of nano-phase SiC powder-based mixed slurry to the coated fiber preform, and a pressure sintering of the matrix at a temperature slightly above melting point of the transient eutectic phase [3]. The development of SiC/SiC composites fabricated NITE process composites was oriented to overcome the weakness of composites through other process routes for the improved matrix cracking stress and thermal conductivity [4].

2.2 Fabrication of SiCf /SiC Composites b-SiC powder was prepared as starting materials. Al2O3 and Y2O3 for liquid phase sintering were used. b-SiC powder with Al2O3 and Y2O3 were mixed with ethanol, it was slurry for fabrication of prepreg sheets. The prepreg sheets were made of slurry and Tyranno-SA fiber was used as reinforcement materials. The properties of used Tyranno-SA fiber were shown in Table 1 [5]. SiCf /SiC composites were sintered by Hot-Press method. Table 1  The properties of Tyranno-SA fiber Other elements Mass density C/Si (mass %) (Mg/m3) Diameter

Crystallite size (nm)

Thermal conductivity (W/mK)

1.08

>200

65

<0.3% O <2% Al

3.02

10

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The bulk density of SiCf /SiC composites was measured by the Archimedes method with an immersion medium of distilled water. The porosity was calculated from the relative density and theoretical density, which were obtained by the rule of mixtures. Thermal conductivity was calculated using the measured bulk density, thermal diffusivity and specific heat capacity. Thermal diffusivities and specific heat capacities of SiCf /SiC composites were measured by the laser flash method using a thermal analyzer. Specimens for laser flash method were produced 6 mm (f) × 1 mm (t). Microstructure was observed by FE-SEM.

3 Results and Discussion Figure 1 shows microstructure of typical Chemical Vapor Infiltration (CVI) SiC/ SiC composites and microstructures of fabricated SiCf/SiC composites used in this study [6]. Both CVI-SiC/SiC and SiCf/SiC composites were designed cross-ply (CP) structure. In Fig. 1, (a) is transverse fiber tow; (b) is longitudinal fiber tow; (c) is SiC matrix; (d) is residual porosity. CVI-SiC/SiC composites typically contain porosity of about 15% because the matrix densification stops when the surface pores are closed. Such a large porosity severely spoils most important properties for thermo-structural materials; thermal conductivity [4]. In case of SiCf/SiC composites fabricated this study, densification surrounding fiber tow and matrix was confirmed from microstructures. Bulk density of fabricated SiCf/SiC composites was above 95%. Thermal conductivity of SiCf/SiC composites and various CVI-SiC/SiC composites was shown Fig. 2. Thermal conductivity of SiCf/SiC composites is 65 W/mK

Fig.  1  Comparison of microstructures with CVI-SiC/SiC composites; (A) Microstructures of CVI-SiC/SiC composites, (B) Microstructures of SiCf/SiC composite fabricated this study; (a) is transverse fiber tow; (b) is longitudinal fiber tow; (c) is SiC matrix; (d) is residual porosity

Thermal Conductivity of SiCf /SiC Composites at Elevated Temperature

Thermal conductivity (W/mK)

70

309

This study Pilot Grade#3

60

TySA/CVI-SiC HNLS/CVI-SiC

50

Tyr SA/ICVI-SiC Nic S/ICVI-SiC Hi Nic /ICVI-SiC

40 30 20 10 0

SiC /SiC composites

Thermal conductivity (W/mK)

Fig. 2  Thermal conductivity at room temperature of SiCf/SiC composites and various CVI-SiC/ SiC composites; Pilot Grade#3 is previous study; CVI is reference from Kaoth [7]; ICVI is reference from G.E. Youngblood [8] (color figure online)

70 60

this study TySA/CVI-SiC/SiC HNLS/CVI-SiC/SiC

50 40 30 20 10 0 0

200

400

600

800

1000

1200

Temperature (°C) Fig.  3  Thermal conductivity of SiCf/SiC composites and CVI-SiC/SiC composites at elevated temperature; CVI is reference from Y. Kaoth [7]

at room temperature. Thermal conductivity of this study was higher than various SiC/SiC composites because desificated internal structures. Figure 3 shows thermal conductivity of SiCf/SiC composites and CVI-SiC/SiC composites at elevated temperature. Thermal conductivity of SiCf/SiC composites decreased with increasing measured temperature since the frequency of phonon scattering increases with increasing temperature. Thermal conductivity of SiCf/SiC composites at 1,000°C was close to CVI-SiC/SiC composites.

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4 Conclusions The SiCf /SiC composites by NITE process was fabricated for high thermal conductivity at elevated temperature. Bulk density of fabricated SiCf /SiC composites was above 95%. SiCf /SiC composites was densificated surrounding fiber tow and matrix, and densification SiCf /SiC composites of affects to high thermal conduc­tivity. Thermal conductivity of SiCf /SiC composites was 65  W/mK at room temperature. Thermal conductivity of this study was higher than various SiC/SiC composites because desificated internal structures. Thermal conductivity of SiCf /SiC composites decreased with increasing measured temperature since the frequency of phonon scattering increases with increasing temperature. The results of this study were to be basic data on thermal conductivity of SiCf /SiC composites for fusion reactor system.

References 1. Riccrdi B, Giancarli L, Hasegawa A, Katoh Y, Kohyama A, Jones RH (2004) Issues and advances in SiC/SiC composites development for fusion reactor. J Nucl Mater 329–333:56–65 2. Jones RH, Giancarli L, Hasegawa A, Kotoh Y, Kohyama A, Riccardi B, Snead LL, Weber WJ (2002) Promise and challenges of SiCf/SiC composites for fusion energy applications. J Nucl Mater 307–311:1057–1072 3. Katoh Y, Dong SM, Kohyama A (2002) Ceram Trans 144:77 4. Katoh Y, Kohyama A, Nozawa T, Sato M (2004) SiC/SiC composites through transient eutectic-phase route for fusion applications. J Nucl Mater 329–333:587–591 5. Katoh Y, Kohyama A, Yang W, Hinoki T, Yamada R, Suyama S, Ito M, Tachikawa N, Sato M, Yamamura T (2000) Presented at the international town meeting on SiC/SiC design and material issues for fusion systems, Oak Ridge, TN, 18–19 January 6. Prouhet S, Camus G, Labrugere C, Guette A, Martin E (1994) Mechanical characterization of Si-C(O) fiber/SiC(CVI) matrix composites with a BN-interphase. J Am Ceram Soc 77(3):649–656 7. Katoh Y, Nozawa T, Snead LL, Hinoki T, Kohyama A (2006) Property tailorability for advanced CVI silicon carbide composites for fusion. Fusion Eng Des 81:937–944 8. Youngblood GE, Senor DJ, Jones RH, Kowbel W (2002) Optimizing the transverse thermal conductivity of 2D-SiCf/SiC composites. J Nucl Mater 307–311:1120–1125

Development of the Crack Detection Technique for NITE SiC/SiC Composite Applied to Fusion Blanket Kazuoki Toyoshima, Tomoaki Hino, and Tatsuya Hinoki

Abstract  Along with efforts to achieve CO2 reduction, one major challenge is the nuclear fusion generation. Highly crystalline and near-stoichiometric silicon carbide fiber-reinforced silicon carbide matrix (SiC/SiC) composites are attractive materials for nuclear fusion systems because high crystalline and near-stoichiometric SiC itself has inherently good chemical stability at high temperatures, strength retention, specific strength, and low activation/low after-heat properties. Of many composite types, new class “fusion-grade” SiC/SiC composites namely robust and dense SiC/SiC composites produced by the nano infiltration transient eutectic (NITE) phase-sintered process are promising. One of key features of fusion-grade SiC/SiC composites is high crack growth resistance and high gas tightness. When applying this class of composite materials, crack propagation behavior needs to be clarified because helium gas employed as coolant may leak into plasma through micro cracks, resulting in fuel dilution in the fusion blanket. The crack detection by the acoustic emission is very difficult due to high crack growth resistance of NITE composite. In this research, novel crack detection technique is developed. Helium gas permeation test was conducted in order to detect the micro crack, which is introduced by tensile test. The diameter of Helium molecular is so small that micro cracks are detected. The permeability was measured for SiC/ SiC composites after tensile test applied over proportional limit stress, in that case, some damage were introduced. Micro cracks were successfully detected by Helium gas permeation test. The Helium gas permeability through NITE SiC/SiC composites were from 10−8 to 10−10 m2/s, which was depending on the damage degree.

K. Toyoshima (*) Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan e-mail: [email protected] T. Hino Laboratory of Plasma Physics and Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo 060-8628, Japan e-mail: [email protected] T. Hinoki Institute of Energy Science and Engineering, Kyoto University, Uji, Kyoto 611-0011, Japan e-mail: [email protected] T. Yao (ed.), Zero-Carbon Energy Kyoto 2010, Green Energy and Technology, DOI 10.1007/978-4-431-53910-0_42, © Springer 2011

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Keywords  Ceramic composite • Crack propagation • Non-destructive evaluation • Nuclear generation • Structural material

1 Introduction SiC fiber reinforced SiC matrix (SiCf/SiC) composites are expected to be applied to not only airplanes and spacecraft but also advanced energy systems such as high thermodynamic efficiency gas cycles and fusion systems because of their superior mechanical properties at high temperature and good irradiation resistance [1]. Nano-infiltrated transient eutectoid (NITE) process enabled a production of nearly full-dense SiC matrix while protecting polycrystalline SiC fibers during the sintering procedure [2]. They have excellent gas permeability, high resistance of crack propagation depending on low matrix porosity, and excellent high temperature mechanical properties in comparison with composites made by other conventional processing techniques [3]. Therefore, NITE SiCf/SiC composites are one of the candidate structural materials for blanket and plasma facing materials of fusion reactors [4]. NITE SiCf/SiC composites have been extensively studied in recent years in our study owing to their improved mechanical properties in comparison with composites processed by other processing techniques. In cases of the application to aerospace or nuclear reactor, environmental effects are extremely important. If some cracks exist, inner oxidation causes easily, in addition the degradation of permeability or thermal conductivity occurs [5–7]. Comprehension of crack propagation behavior reads to expanding possibilities for further application. While in cases of NITE SiCf/SiC composite it is difficult to detect micro cracks since high resistance of crack propagation depending on dense matrix. In the present study, the gas permeability of several SiC/SiC composites was measured [8]. It is reported that permeability is related to the micro structure of pore and crack in the fiber bundle and the matrix [9]. Therefore, helium gas permeability measurement was employed in this study to evaluate the crack propagation behavior. Helium gas was suitable for high accuracy measurement because the diameter of helium atom is 1.5 Å. The aim of this study is to develop the crack detection technique by helium gas permeation measurement.

2 Experimental As the preparation methods for the SiC/SiC composites, nano-powder infiltration and transient eutectoid (NITE) processes were employed. This SiC/SiC composite consisted with layers of unidirectional SiC fiber bundle with SiC matrix. Tyranno

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SA fibers coated by pyrolytic carbon were used as for the reinforcement element of NITE SiCf /SiC composites. The diameter of SiC fiber was approximately 10 mm. The density of NITE SiCf /SiC composites was about 3.0 g/cm3. The volume fraction of fibers was about 45%. The shape of the specimens made by NITE was a flat plate with the size of 40 mm × 10 mm × 1.5 mm for tensile test and subsequent gas permeability measurement. The gauge length was 20 mm for tensile test. Tensile test was conducted prior to gas permeability test to introduce micro cracks to each specimen by applying over PLS. Tensile test was conducted on digital machine (5581, instron Corporation, Japan) in air at room temperature. Crosshead speed was 0.5 mm/min. The strain was measured by the strain gauges (FLK-6-11-1L, Tokyo Sokki Kenkyujo Co., Ltd, Japan) which had the gauge length of 6 mm (length) and 3 mm (width) located on the center of the both side of specimen, and adopt average value of both strain gauges as the strain of specimen. Based upon the stress–strain curve, after the onset of non-linear behavior was observed, loading stress was removed to zero and then specimen was got away from the fixture carefully not to introduce damages. In order to measure the helium gas permeability, a vacuum system is shown in Fig. 1. The device consists of low and high pressures chambers. The specimen was fixed between two chambers by using epoxy resin. The permeation was tested at room temperature. The direction of helium flow was taken perpendicular to the SiC bundle layers. The helium gas pressure of the high-pressure chamber was adjusted by using a mass flow controller and mercury manometer. The range of the pressure was from 102 to 5 × 105 Pa. After the adjustment of the pressure, an increase of the pressure in the low-pressure chamber was measured by using several vacuum gauges. A spinning rotor gauge (SRG), BA ionization gauge (BA) and quadruple mass spectrometer (QMS) were used for the pressure ranges from 10−5 to 1 Pa, from 10−6 to 10−5 Pa and lower than 10−6 Pa, respectively. The signal intensities of the BA ionization gauge and quadruple mass spectrometer were calibrated with the absolute pressure measured by the spinning rotor gauge.

high pressure chamber

He gas

epoxy resin sample

304 SS

Fig. 1  Schematic design of helium gas permeation ­measurement equipment

To pump low pressure chamber

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3 Results and Discussion Figure 2 shows the typical monotonic tensile stress–strain curve at room temperatures of NITE SiC/SiC composites. This figure also shows the corresponding curves for the same material from a previous study [10]. A summary of material properties from the monotonic tests are presented in Table 1. As you can be seen in Fig. 2 and Table 1, the different damage was introduced in each specimen. The stress–strain curves show initially a linear portion up to about 145–160 MPa, which represents the portion before any appreciable amount of matrix crack was developed in the composite. The stress–strain curves after the knee-point show a continuously decreasing slope due to further matrix cracks and associated non-linear displacement. The stress ratio (maximum applied stress/proportional limit stress) is indicative parameter for damage level. The result of the PH–PL relation measured for all the specimens is shown in Fig. 3. It was found that the pressure of the down-flow side for the NITE SiCf/SiC composite samples linearly increased with the pressure of the upper-flow side. Thus, it is regarded that the helium gas flows though sample are a molecular flow. 200

UD4

proportional limit stress 145MPa

Stress [MPa]

150

100

50

maximum applied stress: 176MPa(145x1.21) 0

0

0.02

0.04

0.06

strain [%] Fig. 2  Typical monotonic tensile stress strain curve of NITE SiC/SiC composite Table 1  ID UD1 UD2 UD3 UD4

Damage degree of each specimen Maximum applied stress (MPa) 163 175 186 176

Proportional limit stress (MPa) 148 157 163 145

Stress ratio 1.21 1.14 1.11 1.10

Development of the Crack Detection Technique for NITE SiC/SiC Composite

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Pressure of low pressure chamber PL [Pa]

10−2

ST : stress ratio 10−3

10−4

ST 1.21 10−5

10−6

10−7 103

ST 1.14

ST 1.11 ST 1.10 104 Pressure of high pressure chamber PH [Pa]

105

Fig. 3  Relation between pressure of low pressure chamber PL and high pressure chamber PH

The gas flow through the material is characterized by the ratio between the mean free path of helium lHe and the narrowest path way size D. When the gas flow is a molecular flow, following relation was described [11]:

λ He / D > 0.3

(1)

From this equation, the narrowest pathway size for helium gas is below 0.65 mm. It means that crack size in NITE SiCf /SiC composites is below 0.65 mm.

4 Conclusion The permeability was measured for damaged NITE SiC/SiC composites after tensile test applied over proportional limit stress. Micro cracks were successfully detected by Helium gas permeation measurement method. In the case of NITE SiC/ SiC composites, helium gas permeate specimen by molecular flow, it means that crack size is small enough compare with mean free path of helium atom. Crack radius in NITE SiC/SiC composites is below 0.65 mm even when applied stress is 1.2 times over proportional limit stress. Acknowledgement  This work was supported by Laboratory of Plasma Physics and Engineering, Hokkaido University. Special thanks are given to T. Hino for his experimental cooperation.

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References 1. Bamford M, Florian M, Vignoles GL, Batsale J-C, Cairo CAA, Maille L (2009) Global and local characterization of the thermal diffusivities of SiCf/SiC composites with infrared thermography and flash method. Comp Sci Technol 69:1131–1141 2. Katoh Y, Kohyama A, Nozawa T, Sato M (2004) SiC/SiC composites through transient eutectic-phase route for fusion applications. J Nucl Mater 329–333(5):87–591 3. Shimoda K, Park JS, Hinoki T, Kohyama A (2009) Microstructural optimization of hightemperature SiC/SiC composites by NITE process. J Nucl Mater 386–388:634–638 4. Nishitani T, Tanigawa H, Jitsukawa S, Nozawa T, Hayashi K, Yamanishi T, Tsuchiya K, Moslang A, Baluc N, Pizzuto A, Hodgson ER, Laesser R, Gasparotto M, Kohyama A, Kasada R, Shikama T, Takatsu H, Araki M (2009) Fusion materials development program in the broader approach activities. J Nucl Mater 386–388:405–410 5. Liu Y, Zhang L, Cheng L, Yang XLW, Zhang W, Xu Y, Zeng Q (2008) Preparation and oxidation resistance of 2D C/SiC composites modified by partial boron carbide self-sealing matrix. Mater Sci Eng A 498:430–436 6. Hino T, Hayashishita E, Kohyama A, Yamauchi Y, Hirohata Y (2007) Helium gas permeability of SiC/SiC composite after heat cycles. J Nucl Mater 367–370:736–741 7. Lee Y, Son SJ, Katoh Y, Kohyama A (2004) Damage evaluation of W-coated SiC by thermal conductivity measurement. J Nucl Mater 329–333:549–553 8. Hino T, Hayashishita E, Yamauchi Y, Hashiba M, Hirohata Y, Kohyama A (2005) Helium gas permeability of SiC/SiC composite used for in-vessel components of nuclear fusion reactor. Fusion Eng Des 73:51–56 9. Jinushi T, Hashiba M, Uamauchi Y, Hirohata Y, Hino T, Katoh Y, Kohyama A (2003) Helium gas permeability of low activation SiC/SiC composite. J Vac Soc Japan 46:567–570 10. Mei H, Cheng L (2009) Comparison of the mechanical hysteresis of carbon/ceramic–matrix composites with different fiber preforms. Carbon 47:1034–1042 11. Guthrie A, Wakerling RK (Eds.) (1949) Vacuum Equipment and Technique, Manhattan Project Technical Section Div. 1, vol. 1, McGraw-Hill, New York

Author Index

A Abdul-Raouf, U.M., 117 Afifi, M.M., 117 Aoyagi, S., 43 Aprilia, A., 56 Ara, K., 271 Asmadi, M., 129 Ayada, S., 123 B Bakr, M., 187, 193 C Choi, Y-W., 187, 193 Cravioto, J., 49 G Goembira, F., 111 H Hachiya, K., 100 Harai, T., 278 Hilscher, P.P., 239 Hino, T., 311 Hinoki, T., 271, 306, 311 Hirabayashi, M., 271 Hirato, T., 165 I Ilham, Z., 153 Imadera, K., 239 Ishida, K., 187, 193 Ishihara, K.N., 17, 25, 32, 49, 171 Ishii, H., 43

J Janvier, M., 252 Jiao, L-F., 225 Joonwichien, S., 171 K Kakihira, T., 159 Kanno, I., 278 Kasada, R., 286, 292, 300 Kawamoto, H., 129 Khattab, S.M.R., 117 Kii, T., 100, 187, 193 Kim, B.J., 286 Kim, D-H., 264 Kimura, A., 286, 292, 300 Kimura, N., 187, 193 Kinjo, R., 187, 193 Kishimoto, H., 300 Kishimoto, Y., 239, 252, 258 Knothe, G., 75 Kodaki, T., 117 Konishi, S., 25, 264 Kunugi, T., 214, 225, 233, 271 L Lee, Y., 306 Li, F-C., 225 Li, J., 239, 252 Lim, J-Y., 205 M Masaoka, Y., 245 Masuda, K., 187, 193 Mclellan, B., 17 Misawa, T., 205 Mishra, G., 147

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317

318 Miyake, M., 165 Miyasaka, H., 159 Murakami, S., 245 N Nagai, K., 271 Nakajima, K., 205 Noborio, K., 264 Noh, S., 292 O Ohgaki, H., 100, 187, 193 Oka, S., 177 Okamura, T., 43 Okumura, H., 49, 171 Ose, Y., 233

Author Index T Takahashi, H., 300 Takasaki, M., 187, 193 Tamunaidu, P., 159 Tanigawa, H., 286 Tezuka, T., 17, 25, 32, 56, 63 Toyoshima, K., 311 U Ueda, S., 187, 193 Ueki, Y., 271 Um, N., 165 Utama, N.A., 17, 32 V Varman, M., 136

P Park, Y., 306 Phaiboonsilpa, N., 142 Pyeon, C., 205

W Watanabe, S., 117 Watanabe, Y., 25 Wuyunga, 63

R Rabemanolontsoa, H., 123 Rahman, M.L., 177 Ramakrishna, S., 5 Razon, L.F., 83

Y Yamamoto, Y., 214, 264 Yamasue, E., 49, 171 Yamauchi, K., 95 Yonemoto, Y., 271 Yoshida, K., 100, 187, 193 Yutani, K., 300

S Saimura, M., 117 Saka, S., 95, 111, 123, 129, 136, 142, 147, 153, 159 Sato, Y., 278 Shimoda, H., 43 Shirai, Y., 177 Sonobe, T., 100, 187, 193 Spaargaren, G., 56 Sugahara, A., 258

Z Zen, H., 187, 193 Zhang, Q., 17, 32 Zohri, A.A., 117

Keyword Index

A Absorption, 25 Accelerator-driven system, 205 Acetic acid, 142 Acid methanolysis, 123 Atmospheric CO2 concentration, 25 Awareness, 43 B Back-bombardment, 193 Beam position monitor (BPM), 187 Beam stabilization, 187 Biodiesel, 75, 153 Biodiesel feedstock, 111 Bioethanol, 159 Biomass, 123 BPM. See Beam position monitor Bubble growth process, 233 C Cambodia, 32 Carbohydrate-derived products, 136 Carbon dioxide (CO2), 25 Cello-oligosaccharides, 95 Cellular phone, 43 Cellulose, 147 Ceramic composite, 312 Cerium oxide, 165 Cerium polishing powder waste, 165 Chemical characterization, 159 Client–server control, 258 Climate change, 5 CO2 emissions, 5, 49 Coenzyme specificity, 117 Coke formation, 129 Community, 56 Contact angle, 271

Crack propagation, 312 Current-driven instability, 252 D Data envelopment analysis (DEA), 49 Dimethyl carbonate, 153 Direct numerical simulations (DNS), 214 Divertor, 264 Drag reduction, 225 E Electricity, 32 consumption, 49 generation system, 17 Electric vehicle (EV), 17 Electrification, 63 Electron temperature gradient (ETG), 239 Energy, 5 Energy balance, 75, 83 Erdos grassland, 63 ETG. See Electron temperature gradient EV. See Electric vehicle Extraction, 165 F Fatty acid methyl esters, 153 Feedback control, 187 Feedforward control, 187 Feedstocks, 75 FEL. See Free electron laser F82H, 286 Finite element method, 264 Fixed field alternating gradient accelerator, 205 Flywheel, 177 Forest, 25

319

320 Fracture toughness, 286 Free electron laser (FEL), 100, 193 Fuel properties, 75 Fusion reactor, 300, 306 Future cities, 5 G Global neoclassical transport (GNET), 245 Glycerol carbonate, 153 Guaiacol, 129 Gyrokinetics, 239 H Haematococcus pluvialis, 75 Helical plasma, 245 Helium effect, 300 High-density plasma, 245 High performance computing, 239 High-Pr, 214 High-Re, 214 High temperature particle load, 264 Hot-compressed water, 95, 142 Hybrid system, 177 Hydrogen ion beam, 264 Hydrolysis, 142 Hydrometallurgy, 165 I Indonesia, 32, 56 Inorganic constituents, 159 InSb, 278 Ion-irradiation, 300 Ion temperature gradient (ITG), 239 Irradiation effect, 300 J Japanese beech, 95, 147 Japanese cedar, 136, 142 K Kyoto University Critical Assembly (KUCA), 205 L Large scale simulation, 258 Lead–lithium, 271 Lifestyle change, 63 Lignin, 129, 147

Keyword Index Lignin-derived products, 136 Loose social networks, 43 M Magnetic field effect, 171 Magnetic islands, 252 Magneto-hydro-dynamics (MHD), 214 MALDI-TOF/MS, 95 Marginal stability, 252 Master curve, 286 MCNPX Monte-Carlo code, 205 Methylene blue, 171 MHD. See Magneto-hydro-dynamics Microalgae, 75 Microbubble, 225 Microwave material processing, 100 Mid-infrared free electron laser (MIR-FEL), 187 Monosaccharide, 123 Municipal solid waste, 56 N Nannochloropsis, 75 Neutron multiplication, 205 Nipa sap, 159 Nomadic family, 63 Non-destructive evaluation, 312 Nuclear generation, 312 Nuclear power, 17 Numerical simulation, 193, 233 O Offshore-wind turbine, 177 Oil characteristics, 111 Oxide dispersion strengthened steel, 292 P Parallel computing, 214 a Particle confinement, 245 a Particle heating, 245 PEB. See Pro environmental behavior Phase-change model, 233 Phenol, 147 Phenolic hydroxyl content, 136 Photocatalytic decomposition, 171 Photosynthesis, 25 Photovoltaic (PV), 17 Pongamia pinnata, 111 Pro environmental behavior (PEB), 43 Public participation, 56

Keyword Index Pure boron, 292 PV. See Photovoltaic Pyrolysis, 129 R Radiation detector, 278 Relaxation time, 233 Remote collaboration, 258 Renewable diesel example, 75 RF cavity, 193 RMHD, 252 S Secondary instability, 252 SiCf /SiC composites, 306 Silicon carbide, 271 Simulation monitoring, 258 Site-directed mutagenesis, 117 Small specimen test techniques, 286 Softwood, 142 Specimen size effect, 286 Structural materials, 300, 312 Subcooled pool boiling, 233 Subcritical fluid, 147 Sugarcane sap, 159 Sulfuric acid, 123, 165 Supercritical method, 153 Supercritical water treatment, 136 Supply–demand scenario, 32 Synergy effect, 225 Syringol, 129

321 T Tensile behavior, 292 Thermal conductivity, 306 Thermionic cathode, 193 Tidal turbine, 177 TiO2, 100 Transient liquid phase bonding, 292 Trifluoroacetic acid (TFA), 123

U Update processing, 258

V Viscoelastic fluid, 225

W Waste management, 56 Well-being indicators, 49

X X-ray fluorescence analysis, 278 Xylose reductase (XR), 117

Z Zero-carbon, 17 ZnO, 100, 171 Zone melting method, 278