Table Of ContentOther Pergamon Titles of Interest
ANDRESEN & MAELAND Hydrides tor Energy Storage
BLAIR et al Aspects of Energy Conversion
BOER Sharing the Sun
EGGERS-LURA Solar Energy for Domestic Heating and
Cooling
EGGERS-LURA Solar Energy in Developing Countries
IAHE Hydrogen in Metals
MCVEIGH Sun Power
VEZIROGLU First World Hydrogen Energy Conference
Proceedings
VEZIROGLU Energy Conversion - A National Forum
VEZIROGLU & SEIFRITZ Hydrogen Energy System
DE WINTER Sun: Mankind's Future Source of Energy
Pergamon Related Journals
International Journal of Hydrogen Energy
Annals of Nuclear Energy
Progress in Nuclear Energy
Solar Energy
Sun World
Progress in Energy and Combustion Science
Energy Conversion
Energy
SOLAR-HYDROGEN
ENERGY SYSTEMS
An Authoritative Review of Water- splitting Systems
by Solar Beam and Solar Heat: Hydrogen Production,
Storage and Utilisation
edited by
TOKIO OHTA
Professor of Materials Science
and Energy System
Yokohama National University, Japan
PERGAMON PRESS
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Copyright ©1979 Pergamon Press Ltd.
All Rights Reserved. No part of this publication may be
reproduced, stored in a retrieval system or transmitted
in any form or by any means: electronic, electrostatic,
magnetic tape, mechanical, photocopying, recording or
otherwise, without permission in writing from the
publishers.
First edition 1979
British Library Cataloguing in Publication Data
Solar-hydrogen energy systems. -
1. Solar energy 2. Hydrogen as fuel
I. Ohta, Tokio
621.47*5 TJ810 79-40694
ISBN 0-08-022713-9
In order to make this volume available as economically
and as rapidly as possible the author's typescript has
been reproduced in its original form. This method un-
fortunately has its typographical limitations but it is
hoped that they in no way distract the reader.
Printed and bound at William Clowes & Sons Limited
Beccles and London
AUTHORS
CHAPTERS 1,2,6,9 and 10
Tokio OHTA, Ph.D.
Professor of Materials Science and Energy System
Faculty of Engineering, Yokohama National University
Yokohama, Japan
CHAPTER 3
Takehiko TAKAHASHI, Ph.D.
Professor of Chemistry of Industrial Inorganic Reactions
Department of Applied Chemistry,
Faculty of Engineering Nagaya University
Nagoya, Japan
CHAPTER 4 and APPENDICES
Seijiro IHARA, Ph.D.
Senior Research Staff
Energy Division, Electrotechnical Laboratory
Tokyo, Japan
CHAPTER 5
Shoichi SATO, M.Sc.
Senior Chemical Engineer
Takasaki Radiation Chemistry Establishment,
Japan Atomic Energy Research Institute
Tokai, Japan
CHAPTER 6
Nobuyuki KAMIYA, Ph.D.
Instructor of Energy Materials Institute
Faculty of Engineering, Yokohama National University
Yokohama, Japan
CHAPTER 7
Kenichi HONDA, Ph.D.
Professor, Department of Synthetic Chemistry
Faculty of Engineering, The University of Tokyo
Tokyo, Japan
VTl
Vlll Authors
CHAPTER 7
Akira FUJISHIMA, Ph.D.
Associate Professor, Department of Synthetic Chemistry
Faculty of Engineering, The University of Tokyo
Tokyo,Japan
Tadashi WATANABE, Ph.D.
Instructor, Department of Synthetic Chemistry
Faculty of Engineering, The University of Tokyo
Tokyo,Japan
CHAPTER 8
Akira MITSUI, Ph.D.
Professor of Marine Biochemistry and Bioenergetics
Division of Biology and Living Resources,
University of Miami
Florida, U.S.A.
CHAPTER 9
Shuichiro 0N0, Ph.D.
Chief of Second Section, Energy Chemistry Division,
National Chemical Laboratory for Industry
Tokyo, Japan
Masuhiro YAMAGUCHI, Ph.D.
Associate Professor of Materials Science
Faculty of Engineering, Yokohama National University
Yokohama, Japan
CHAPTER 10
William J.D. ESCHER, B.S. in Engineering
Owner of ESCHER TECHNOLOGY ASSOCIATES
Michigan, U.S.A.
ACKNOWLEDGEMENTS
The editor should like to express his cordial thanks to
Dr. Seiji Kaya, Dr. Kodi Hushimi, Dr. Hideo Akamatsu and
Dr. T. Nejat Veziroglu for their heart warming encouragements
and supports in every respect.
Hearty thanks are also due to the Ministry of Education,
Science and Culture,the Japan Society for Promotion of Science»
The Yoshida Science Foundation, and the Nihon Securities
Scholarship Foundation for their financial supports.
The editor would like to mention also that Dr. M.V.C. Sastri,
professor of Indian Institute of Technology and currently a
visiting professor of Yokohama National University, has kindly
given some valuable comments and Mr. S. Tanisho has assisted
to prepare the clean manuscripts for this book.
ix
PREFACE
Photosynthesis is the process fundamental to all life on the Earth. Plant-roots
absorb water from the soil and the chlorophyll splits it into hydrogen and oxygen
using solar energy. The oxygen is released to the atmosphere while the hydrogen
is combined with carbon dioxide extracted by the plant from the atmosphere
producing carbohydrates, the basic substance of plants. And, of course, plants
provide the food source directly or indirectly for all living organisms.
When plant material is combusted for energy purposes, or metabolized otherwise,
water and carbon dioxide are created and usually released to the atmosphere, thus
completing a natural cycle.
But with more than 4 billion people living on the Earth and demanding a reasonable
or high quality of living, we have seen a dramatic scale-up of supporting industrial
developments. Often this scale-up proceeds in almost a "run-away" manner. Various
adverse effects have accrued which interrupt or counter this natural cycle, e.g.,
environmental pollution.
More significantly, the consumption of valued resources of traditional kinds,
those that are maidistributed on the Earth produces an unstable supply system.
The resulting stresses on the techno-economic operation of many nations, especially
highly developed internationally-tied countries has been dramatic. The resulting
impacts on internal affairs and international relationships have escalated markedly
in recent years.
It is apparent that the ultimate remedy to the basic problems we now face in this
regard is to develop those technologies which, in essence, accelerate the natural
cycles. For example, we must learn to produce hydrogen and oxygen from water using
solar energy processes. We might also fix atmospheric carbon, but at the present
stage of consideration, hydrogen production seems more fundamental.
To be more specific, the strong sunlight falling upon the tropical zone (ocean
and desert) must be used to split seawater or underground water to produce hydrogen
and oxygen. Hydrogen is a clean, efficient fuel which can be used, for example, to
power aircraft. It is also an important, even basic, chemical intermediary for the
production of fertilizers and commodities of high market value. Thus the energy,
the water and the food can all be provided by this system.
— From my thesis "Technologies Today and Tomorrow" published
in International Journal of Hydrogen Energy, Vol. 1, p.241,
(1976) —
xi
XI1 Preface
The feasibility study on such hydrogen energy systems has been undertaken since the
autumn of 1972 in Japan. As one of the working groups, the small round-table
conferences had been frequently held by the Japan Society for the Promotion of
Science in 1973 and 1974. Since then, the main participated scientists have been
organized as Academic Association for Hydrogen Energy (A.A.H.E.) and which has
continued to study this issue to date.
This book contains selected papers presented at the A.A.H.E.-conferences. Most of
them are concerned with "How to split water by sunlight". Along with them, the long
period storage of solar energy using metal hydrides and a system-level "concept
paper" on direct solar energy conversion at sea are included. These two chapters
address the potentially important subjects of using desert- and ocean-based solar
energy conversion facilities.
I believe that this book does contain an up-to-date and top level contents. It is
my sincere hope that the readers looking for new areas to enter professionally
may find some in this book and join this interdisciplinary field.
March 1979 Tokio Ohta
Yokohama, JAPAN
CHAPTER 1
INTRODUCTION - A REVIEW OF
THE SCOPE
1-1 SIGNIFICANCE OF SOLAR HYDROGEN ENERGY SYSTEMS
Fossil fuel can be denoted as ^1^, where n carbon atoms C are combined with m hy-
drogen atoms H. Coal, for instance, has a formula in which n is 1 and m is zero. In
the case of hydrogen, n is zero and m is 2. A natural trend in fossil hydrogen carbon
utilization is shown in Fig. 1.1. On the vertical axis is the number of carbons and
on the horizontal axis the ratio of the number of hydrogen atoms to the number of
carbon atoms (m/n). It is clearly noted that the trend is toward utilization of heavy
oil, light oil, kerosene, naphtha, gasoline, propane, and methane in this order. On
the vertical axis of the right hand side are indicated the boiling points measured
in the absolute temperature of these fractions. As is known, the boiling point drops
as the number of hydrogen atoms rises in generous tendency. Propane and methane,
which are gases at room temperature, can be transported and stored as liquefied.
This means that cryogenics has an important role to play in advanced energy systems.
It should be also noted that the order of boiling points corresponds to that of per-
mole heating value.
There are grounds for this trend in hydrocarbon utilization. Firstly, fossil fuel
with high carbon content almost always contains a high level of impurities such as
sulfur and emits polluting gases upon burning. Secondly, high-carbon hydrocarbons
are heavy, highly viscous and therefore difficult to handle. The thought that m/n
will reach an infinitely large value at C0H2 as it keeps increasing agrees with thé
concept of the energy-economy taking the environmental problems into consideration.
To stabilize and optimize energy economy, at least the following two measures are
basically necessary
(1) Diversification of energy sources. Besides coal, natural gas, tar sand, .oil shale,
and nuclear power, as much natural energy sources as possible, such as hydraulic,
solar, geothermal, and oceanic power should be utilized. It is preferable to overcome
the exclusive dependence upon petroleum energy by many kinds of competitive energies.
(2) Organized multiple use of secondary energy. One of the forms of clean secondary
energy being supplied to users is electricity. However, losses are inherent to elect-
ric power transport. High-voltage transmission is subject to corona discharge loss
and large current transmission to Joulian loss. These losses average 4~9%. Besides,
highly urbanized society in limited land space has made it impossible to erect higher
voltage and larger scale electric transport facilities. Storage of large electric
power is presently depending upon pumping-up power generation, which is said to have
a 70% efficiency. The pumping-up system involves siting difficulties, so that the
power station, consumers, and reservoirs are often located far apart; hence the cost
if erecting towers in the transmission network will be enormous.
Considering these difficulties along with the fact that about 65% of end usage of
1
2 Solar-Hydrogen Energy Systems
τ(κ)
20 Β
iLight oil 573
\
Fossil hydrocarbons
15 II
^Kerosene
Naphtha 473
10
I Isooctane 373
363
I Gasoline 343
k N-pentane _ 309
Butane 273
\' VPropane 223
sÄEthane _ 184
v^,Jle thane
112
JL _L
5 -
Fig. 1.1 Utilization-trends in fossil hydrocarbon as plotted
n vs. m/n in Cfl and boiling temperature T (K) [1].
r m ß
energy in advanced industrial nations today is in the form of heat, one would readily
realize the significance of introducing hydrogen - which is a fuel as clean as elect-
ricity and which, on combustion, produces almost only water - as another secondary
energy. Diversified secondary energies must not be used independently as they are now.
They should be organically linked. Figure 1.2 is a conceptual diagram of a post pet-
roleum energy system.
Water is dissociated by means of natural or nuclear energy. Hydrogen is produced in
a closed cycle at a proper temperature range, then electricity is generated at a dif-
ferent temperature range. Electric power system and hydrogen energy system are the
two subsystems with organized links. There are two main links with few moving parts,
quiet, labor-saving and automatic in operation. These are realized when hydrogen/air
fuel cells are used to convert hydrogen to electricity. Another electric storage
method that meets the above conditions is to store hydrogen produced by water elect-
rolysis. From the above, the reader should be able to understand the importance of a
"solar-hydrogen energy system11. This is the ideal and ultimate technological innova-
tion in this field. It will be the most preferable form of energy utilization by
human beings.
It is well-known that hydrogen is used as an important chemical raw material for
various substances as well as an excellent energy medium. The basic functions of hy-
drogen in the atmosphere will be described below. Air is composed of 79% of nitrogen
(N ), 21% of oxygen (O2), 0.034% of carbon dioxide (CO2), and small amounts of other
2
gases. If hydrogen is released into atmosphere and reacts with nitrogen, this will
