Solar Cell Array Design Handbook: The Principles and Technology of Photovoltaic Energy Conversion

549 Pages·1980·6.93 MB·English

by  Hans S. Rauschenbach (auth.)

Solar Cell
Array Design
Handbook
The Principles and Technology 01
Photovoltaic Energy Conversion
Solar Cell
Array Design
Handbook
The Principles and Technology of
Photovoltaic Energy Conversion
H. s. Rauschenbach
Special Assistant for Advanced Technology
TR W Defense and Space Systems Group
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LONDON TORONTO MELBOURNE
Van Nostrand Reinhold Company Regional Offices:
New York Cincinnati Atlanta Dallas San Francisco
Van Nostrand Reinhold Company International Offices:
London Toronto Melbourne
Copyright © 1980 by Litton Educational Publishing, Inc.
Softcover reprint of the hardcover 1s t edition 1980
Library of Congress Catalog Card Number: 79-9389
ISBN-13: 978-94-011-7917-1 e-ISBN-13: 978-94-011-7915-7
DOI: 10.1007/978-94-011-7915-7
All rights reserved. No part of this work covered by the copyright heroon may
be reproduced or used in any form or by any means-graphic, electronic, or
mechanical, including photocopying, recording, taping, or information storage
and retrieval systems--without permission of the publisher.
Manufactured in the United States of America
Published by Van Nostrand Reinhold Company
135 West 50th Street, New York. N.Y. 10020
Published simultaneously in Canada by Van Nostrand Reinhold Ud.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
library of Congress Cataloging in Publication Data
Rauschenbach, Hans S
Solar cell array design handbook.
Includes index.'
1. Solar batteries. 2. Photovoltaic power
generation. I. Title.
TK2960.R35 621.47'5 79-9389
IDreface
Solar cells and solar cell arrays-photovoltaic tematized, computer-aided process. While it
converters of solar energy into electric energy has not been possible to adequately define or
are a reality. In a time period of two decades, improve, or otherwise influence the creative
solar cell arrays have grown in size from less than design activity, all other aspects of the design
1 watt to hundreds of kilowatts of electrical process have been formalized and, for good rea
output in terrestrial applications and to over 10 son, subjected to documentation, control, and
kilowatts of output in space. New designs are verification.
on the drawing boards and in development lab As the 1970's draw to a elose, we find our
oratories all over the world for terrestrial and selves engulfed by flurrying activities in photo
space arrays having hundreds and thousands of voltaics. While we stand at the threshold of an
kilowatts of electric power output. Solar cell unprecedented economical exploitation of this
efficiency has increased from just a feeble re particular solar energy conversion technology,
sponse to sunlight to nearly 20%, surpassing the we should also realize that all the "easy" in
luminous efficiency of the incandescent light ventions have perhaps been made already.
bulb on the way. Solar cell array costs are de From here on, the going can be expected to get
creasing rapidly, making photovoltaic electric tougher. It is hoped that this book will be he1p
energy affordable and competitive today in re ful to those who are going to keep on working
mo te areas. for the benefit to all of use who consume energy .
In the same two-decade time span, the solar
cell array design effort has matured from a spir
ited pioneering effort into a sophisticated, sys- Hans S. Rauschenbach
v
Purpose and Scope
of this Handbook
This handbook intends to diseminate as much ranging from the illustrative and introductory
current and practical information relating to to the detailed technical. Most of the text
photovoltaic energy conversion technology for should be understandable to advanced high
earth and space applications as practical. The school students and senior technicians. Few
emphasis is on the presentation of many differ- sections, if any, are expected to pose difficulties
ent concepts and detailed techniques for several for college graduates or practicing engineers.
reasons: The mathematical treatment has been held
simple. Differential and integral equations are
• To introduce non-technical persons to the used sparingly, but are included to permit com
subject puter programming. Most mathematical prob
• To aid students of the subject and younger lems can be handled with today's scientific
workers in this field in mastering it pocket calculators.
This handbook recounts some of the more
• To help specialists already working in the field
important historical events that led to today's
to get their jobs done more effectively
advanced solar cell array technology and in
• To inspire the creativity of advanced designers
cludes sufficient re fe rene es for loeating more
• To document those concepts, data, and infor detailed accounts. Subjects that are treated else
mation that are of interest today but are not where and readily available, such as general
readily available in the open literature structural design, heat transfer and thermody
• To define the entire field of solar cell array namics, civil engineering, and electrical wiring
design and its multidisciplinary nature. codes and practices, are not included here.
Rather, only the special considerations for solar
This handbook is written on several levels, cell arrays are treated.
LEGAL NOTICE
This handbook attempts to document the knowl testing, including solar cells, other materials,
edge, data, and information which may be of processes, components, arrangements, and de
current significance to solar cell array design. signs. Some of these patents have been de
However, it is emphasized that there exists a scribed herein, but many more have not been
large number of patents which relate to all as referred to. The description in this handbook
pects of solar cell array design, fabrication, and of any component, process, apparatus, material,
vii
viii PURPOSE AND SCOPE OF THIS HANDBOOK
design, composition, or any other feature of parers, editors, approvers, or publishers of this
any article may fall within a claim of an existing or the earlier document; nor any other person:
patent. It is not the intent of any of the au
thors, editors, and publishers of and contribu 1. Makes any warranty or representation, ex
tors to this handbook-nor is it the intent of pressed or implied, with respect to the
any of the sponsoring or performing organiza accuracy, completeness, or usefulness of
tions involved in the preparation of this or the the information contained in this docu
original handbook-to induce anyone to infringe ment, or that the use of any information,
upon any existing patent. It is the responsibil apparatus, method, or process disclosed in
ity of the prospective user of any of the infor this document may not infringe upon pri
mation, material, data, and descriptions herein vately owned rights;
to determine -whether such usage constitutes in-' 2. Assumes any liabilities with respect to
fringement or noninfrigement of any patent or the use of, or for damages resulting from
otherwise legally protected or proprietary right. the use of, any information, apparatus,
Specifically, neither the United States, the method, or process disclosed in this
National Aeronautics and Space Administration, document;
the California Institute of Technology, the Jet 3. Sanctions, approves or recommends any
Propulsion Laboratory, nor the TRW Defense designs, practices, selections, or proce
and Space Systems Group; nor any of the em dures contained in this document for a
ployees of these organizations; nor the pre- specific purpose, use, or project.
SAFETY NOTICE
Solar cell assemblies, modules, panels, or arrays A larger array, when exposed to bright sun
are sources of electric power and may, under light and short-circuited with a conductor having
certain circumstances, constitute a potential 'inadequate cross-section, may start a fire.
hazard. Even under conditions of low ambient Any solar cell assembly, even in low ambient
lighting, a sufficient number of solar cells con light, when accidentally short-circuited, may
nected in series may produce voltages and cur cause a spark that is capable of igniting explo
rents that may cause electrocution. Appropriate sive atmospheres, such as may be found in
safety procedures for handling and installing solvent cleaning operations.
such assemblies must be used and followed (see
also the entries under Safety in the Index).
Acknowledg ments
This handbook is a completely revised, updated, are the many contributors to the original manu
and expanded issue of an earlier, space technol script drafts and their extensive reviews by nu
ogy oriented document published in October merous personnel in industry and government,
1976 and now available as NASA CR-149365 especially by L. Slifer of the NASA Goddard
[N77-14193 (Vol. 1) and N77-14194 (Vol. 2)]: Space Flight Center. The typing and editing of
Solar Cell Array Design Handbook, from the the many drafts by M. J. Gustetto, M. C. Winn,
National Technical Information Service, Spring and E. A. Harper of TRW, and by my wife
field, Virginia 22151. Marianne are also greatly appreciated. A special
The earlier handbood was prepared by the word of appreciation and thanks goes to my re
Power Sources Engineering Department of sourceful wife and understanding children,
TRW Defense and Space Systems Group, Space Christian, Isabella, Angelina, and David, who
Vehicles Division (author and editor, H. S. provided a horne environment that not only
Rauschenbach), under Contract No. 953913 made the preparation of this book possible, but
with the California Institute of Technology, Jet also made it a unique experience.
Propulsion Laboratory, Pasadena, California. Credit goes also to the literally thousands of
The active support in the creation of the original workers who, over the years, have created the
document of E. Cohn at NASA Headquarters, large body of photovoltaic knowledge and tech
J. V. Goldsmith and R. Josephs at JPL, and the nology from which this author has drawn, and
following at TRW is gratefully acknowledged to the institutions of higher learning, private in
and appreciated: dustry, and government which contributed to it
W. R. Brannian and P. Goldsmith, editing in some indispensable way. Since a book of
and review; A. Kaplan, material properties, stress this nature cannot name them all, and naming of
and fatigue; R. M. Kurland, mechanical systems only a few would be highly inequitable, names
and components; W. Luft, solar cell and array of individuals and organizations have been de
technology and analysis; A. N. Munoz-Mellows, leted entirely, except where essential, from the
thermo-dynamics and heat transfer; H. Riess, text. Those included in the references were not
electrical systems and array analysis; D. W. selected according to the significance of their
Rusta, electrical systems, array and orbital anal work, but rather to provide the researcher with
ysis; W. R. Scott, corrosion; R. K. Yasui, array leads for a greater in-depth pursuit of a partic
technology and material properties. ular topic.
Also acknowledged and deeply appreciated
ix
Contents
Preface I v 1-17. Spinning Space Arrays / 21
Purpose and Scope of This Handbook I vii 1-18. Space Concentrator Arrays / 22
Legal Notice I vii 1-19. Space Array Orbital
Safety Notice I viii Performance / 22
Acknowledgments I ix
2 Array Analysis 30
PART I SOLAR CELL ARRA YS 1
Analytical Concepts / 30
2-1. The Role of Analysis / 30
1 Array Systems 3
2-2. Atoms and Electrons / 30
Array Concepts / 3 2-3. Electric Charge / 31
1-1. Arrays and Batteries / 3 2-4. Conductors / 31
1-2. Arrays, Panels, Parts, and 2-5. Insulators / 32
Components / 3 2-6. Current / 32
1-3. Array Types / 3 2-7. Electric Field / 33
1-4. The Array as Part of the Power 2-8. Potential and Voltage / 34
System / 4 2-9. Electrical Circuits / 34
1-5. The Array as a System I 6 2-10. Sources and Generators / 35
1-6. Hybrid Systems / 6 2-11. Current Flow Convection / 35
Historical Developments / 6 2-12. Resistance and Resistors / 36
1-7. History of Terrestrial Arrays / 6 2-13. Ohm's Law / 37
1-8. History of Space Arrays / 8 2-14. Power / 38
1-9. The Future of Solar Cell 2-15. Energy / 38
Arrays / 12 2-16. Capacitance and Capacitors / 38
Array Applications / 15 2-17. Magnetism / 39
1-10. Terrestrial Applications / 15 2-18. Inductance and Inductors / 40
1-11. Space Applications / 15 2-19. AC and DC Current / 40
1-12. Power from Space / 15 2-20. Impedance / 40
Array Systems Performance / 16 Circuit Analysis / 41
1-13. Array Ratings / 16 2-21. Circuit Modelling / 41
1-14. Terrestrial Flat-Plate Arrays / 18 2-22. Circuit Simplifieations / 43
1-15. Terrestrial Concentrator 2-23. Circuit Responses / 45
Arrays / 20 2-24. Cireuit Equations / 45
1-16. Space Flat-Plate Arrays / 20 2-25. Operating Points / 47
xi
xii CONTENTS
Semiconductors and Solar cen Models / 48 2-58. Terrestrial Array Operating
2-26. Quantum Mechanics / 48 Temperatures I 98
2-27. Semiconductor Materials / 50 Reliability I 98
2-28. Semiconductor Junctions / 50 2-59. Reliability and Failure Rates / 98
2-29. Solar cen Operation / 51 2-60. Failure Modes and Effects I 99
2-30. Solar cen Equation I 52 2-61. Reliability Models I 10 1
2-31. Solar cen DC Model I 55 Orbital Analysis I 102
2-32. Distributed Parameter Solar cen 2-62. Spacecraft Motion in Orbit I 102
Model I 56 2-63. Simplified Orbit Theory I 102
2-33. Analytical Models for Computer 2-64. Altitude in Elliptic Orbits I 104
Work I 56 2-65. Location in Space I 104
2-34. Non-Analytical Computer 2-66. Illumination of the Orbit
Models I 59 Plane I 106
2-35. Selecting the Proper Model I 60 2-67. The Sun Angle I 107
2-36. Solar cen AC Model / 60 2-68. Solar Eclipses I 108
2-37. Solar cens in Parallel and
Series I 64 3 Array Design 111
2-38. Illuminated Arrays I 65
2-39. Partially Shadowed cens in Design Concepts I 111
Parallel I 67 3-1. The Design Process I 111
2-40. Partially Shadowed cens in 3-2. Design Phases I 111
Series I 68 3-3. Design Personnel I 112
2-41. Solar cen Strings with Shunt 3-4. Uncertainties and Risks I 112
Diodes I 69 3-5. Design Optimization / 112
2-42. Shadowing Factors I 72 3-6. Design Requirements, Criteria and
2-43. Nonilluminated Array Interfaces I 113
Models I 74 3-7. Policy Constraints I 115
2-44. Blocking Diode Models I 74 3-8. Design Review I 116
2-45. Reverse-Biased Solar Cells I 74 3-9. Producibility and Cost I 117
2-46. Power Dissipation in Reverse- 3-10. Human Engineering I 117
Biased Solar Cells I 76 Photovoltaic System Design I 117
Array Performance Prediction I 77 3-11. Load Profile Development I 117
2-47. Array Output Analysis I 77 3-12. Illumination Profile
2-48. Sequence of Shifting 1-V Development I 119
Curves I 80 3-13. Preliminary Array Sizing-Area
2-49. Calculation of Angle of Method I 123
Incidence I 81 3-14. Preliminary Array Sizing-Cen
2-50. Calculation of Effective Solar Efficiency Method I 123
Intensity I 82 3-15. Preliminary Array Sizing-Cen
2-51. Calculation of cen and Array 1-V Power Method I 124
Curves I 82 Detailed Array Design I 124
Shadow Analysis I 84 3-16. Detailed Array Sizing I 124
2-52. Shadows I 84 3-17. Space Array Configuration
Thermal Analysis I 89 Selection I 126
2-53. Heat Flow and Temperature I 89 3-18. Number of Required Solar
2-54. Heat Transfer by Conduction I 92 cens I 126
2-55. Heat Transfer by Convection I 93 3-19. Array Layout I 129
2-56. Heat Transfer by Radiation I 94 3-20. Array Wiring I 130
2-57. Electrical Heat Transfer 3-21. Hot Spot Design
Analogy I 96 Considerations I 131
CONTENTS xiii
3-22. Designing for Reliability / 132 4-7. Classification According to
3-23. High Voltage Design / 132 Application / 160
Thermal Design / 132 4-8. Classification According to
3-24. Temperature Control in Materials / 161
Space / 132 4-9. Classification According to
3-25. Temperature Control on Construction / 163
Earth / 133 4-10. Classification According to
3-26. Decreasing Absorptance / 134 Optical Features / 164
3-27. Increasing Emittance / 134 4-11. Contemporary Silicon Solar Cell
3-28. Increasing Convection / 135 Types for Space Use / 165
3-29. Improving the Geometry / 135 4-12. Contemporary Silicon Solar Cells
3-30. Minimizing Eclipse Exit for Terrestrial Use / 165
Temperatures / 136 Electrical Characteristics / 167
Radiation Shielding Design / 136 4-13. Solar Cell Polarity / 167
3-31. Solar Cell Radiation 4-14. Current-Voltage
Shielding / 136 Characteristics / 167
3-32. Damage-Equivalent Fluence in 4-15. Series Resistance / 168
Orbit / 137 4-16. Shunt Resistance / 170
3-33. Shielding Thickness '-(4-17. Energy Conversion
Determination / 137 Efficiency / 170
3-34. Procedure for I-MeV Fluence 4-18. Curve and Fill Factors / 171
Analysis / 140 4-19. Effects of Solar Intensity / 172
3-35. Shielding Against Low Energy 4-20. Reversible Effects of
Protons / 142 Temperature / 173
3-36. Absorbed Dose in Cover and 4-21. Temperature Coefficients / 173
Adhesive / 144 4-22. Irreversible Temperature
Electromagnetic Design / 145 Effects / 178
3-37. Electrostatic Shielding / 145 4-23. High-Intensity, High-Temperature
3-38. Magnetic Cleanliness / 146 Operation / 178
3-39. Minimizing Magnetic 4-24. Low-Intensity, Low-Temperature
Moments / 147 Operation / 179
3-40. Electrostatic Charging 4-25. Reverse Characteristics / 179
Control / 149 Optical Characteristics / 180
4-26. Effects of Optical Characteristics
on Cell Efficiency / 180
PART 11 ARRAY BUILDING BLOCKS 4-27. Spectral Response Defmed / 181
4-28. Spectral Response of Solar
Cells / 183
4 Solar CeUs 155
Mechanical Characteristics / 184
Photovoltaics / 155 4-29. Solar Cell Sizes and
4 -1. Solar CeU Devices / 155 Shapes / 184
'\j
4-2. Direct Energy Conversion / 155 4-30. Cell Thicknesses / 185
4-3. Discovery of the Photovoltaic 4-31. Active Area / 186
Effect / 156 Contacts / 187
"4-4. History of Contemporary Silicon 4-32. Solar Cell Contact Types / 187
I
CeUs / 156 4-33. Contact Configurations 188
4-5. History ofNon-Silicon 4-34. Contact Strength / 189
Cells / 159 Radiation Effects / 190 "
Solar Cell Types / 160 4-35. Solar Cell Radiation
4-6. Solar Cell Classification / 160 Damage / 190