Nanophysics of Solar and Renewable Energy

T his easily accessible textbook provides an overview of solar to electric energy conversion, followed by a detailed look at one aspect, namely photovoltaics, including the underlying principles and fabrication methods. Professor Wolf, an experienced author and teacher, reviews such green technologies as solar–heated–steam power, hydrogen, and “artificial leaf” approaches, as well as nuclear fusion. The energy generation in the sun is explained and applied to terrestrial fusion reactors. The book is self–contained so as to be suitable for students with introductory calculus–based courses in physics, chemistry, or engineering. It introduces concepts in quantum mechanics, atomic and molecular physics, plus the solid state and semiconductor junction physics needed to attain a quantitative understanding of the current status of this field. With its comments on economic aspects, it is also a useful tool for those readers interested in a career in alternative energy.

Preface XIII 1 A Survey of Long–Term Energy Resources 1 1.1 Introduction 1 2 Physics of Nuclear Fusion: the Source of all Solar–Related Energy 27 2.1 Introduction: Protons in the Sun’s Core 28 2.2 Schrodinger’s Equation for the Motion of Particles 30 2.3 Protons and Neutrons and Their Binding 35 2.4 Gamow’s Tunneling Model Applied to Fusion in the Sun’s Core 35 2.5 A Survey of Nuclear Properties 43 3 Atoms, Molecules, and Semiconductor Devices 49 3.1 Bohr’s Model of the Hydrogen Atom 49 3.2 Charge Motion in Periodic Potential 52 3.3 Energy Bands and Gaps 53 3.4 Atoms, Molecules, and the Covalent Bond 60 3.5 Tetrahedral Bonding in Silicon and Related Semiconductors 71 3.6 Donor and Acceptor Impurities; Charge Concentrations 73 3.7 The PN Junction, Diode I–V Characteristic, Photovoltaic Cell 80 3.8 Metals and Plasmas 84 4 Terrestrial Approaches to Fusion Energy 87 4.1 Deuterium Fusion Demonstration Based on Field Ionization 88 4.2 Deuterium Fusion Demonstration Based on Muonic Hydrogen 96 4.3 Deuterium Fusion Demonstration in Larger Scale Plasma Reactors 102 5 Introduction to Solar Energy Conversion 115 5.1 Sun as an Energy Source, Spectrum on Earth 115 5.2 Heat Engines and Thermodynamics, Carnot Efficiency 117 5.3 Solar Thermal Electric Power 119 5.4 Generations of Photovoltaic Solar Cells 122 5.5 Utilizing Solar Power with Photovoltaics: the Rooftops of New York versus Space Satellites 125 5.6 The Possibility of Space–Based Solar Power 126 6 Solar Cells Based on Single PN Junctions 133 6.1 Single–Junction Cells 133 6.2 Thin–Film Solar Cells versus Crystalline Cells 145 6.3 CIGS (CuIn 1–x Ga x Se 2 ) Thin–Film Solar Cells 147 6.4 CdTe Thin–Film Cells 151 6.5 Dye–Sensitized Solar Cells 153 6.6 Polymer Organic Solar Cells 155 7 Multijunction and Energy Concentrating Solar Cells 157 7.1 Tandem Cells, Premium and Low Cost 158 7.2 Organic Molecules as Solar Concentrators 169 7.3 Spectral Splitting Cells 171 7.4 Summary and Comments on Efficiency 172 7.5 A Niche Application of Concentrating Cells on Pontoons 172 8 Third–Generation Concepts, Survey of Efficiency 175 8.1 Intermediate Band Cells 175 8.2 Impact Ionization and Carrier Multiplication 177 8.3 Ferromagnetic Materials for Solar Conversion 182 8.4 Efficiencies: Three Generations of Cells 185 9 Cells for Hydrogen Generation; Aspects of Hydrogen Storage 187 9.1 Intermittency of Renewable Energy 187 9.2 Electrolysis of Water 187 9.3 Efficient Photocatalytic Dissociation of Water into Hydrogen and Oxygen 188 9.4 The “Artificial Leaf” of Nocera 193 9.5 Hydrogen Fuel Cell Status 194 9.6 Storage and Transport of Hydrogen as a Potential Fuel 195 9.7 Surface Adsorption for Storing Hydrogen in High Density 196 9.8 Economics of Hydrogen 200 10 Large–Scale Fabrication, Learning Curves, and Economics Including Storage 203 10.1 Fabrication Methods Vary but Exhibit Similar Learning Curves 203 10.2 Learning Strategies for Module Cost 205 10.3 Thin–Film Cells, Nanoinks for Printing Solar Cells 207 10.4 Large–Scale Scenario Based on Thin–Film CdTe or CIGS Cells 209 10.5 Comparison of Solar Power versus Wind Power 214 10.6 The Importance of Storage and Grid Management to Large–Scale Utilization 215 11 Prospects for Solar and Renewable Power 223 11.1 Rapid Growth in Solar and Wind Power 223 11.2 Renewable Energy Beyond Solar and Wind 225 11.3 The Legacy World, Developing Countries, and the Third World 226 11.4 Can Energy Supply Meet Demand in the Longer Future? 227 Appendix A: Exercises 231 Exercises to Chapter 1 231 Exercises to Chapter 2 232 Exercises to Chapter 3 233 Exercises to Chapter 4 234 Exercises to Chapter 5 236 Exercises to Chapter 6 236 Exercises to Chapter 7 237 Exercises to Chapter 8 238 Exercises to Chapter 9 238 Exercises to Chapter 10 238 Exercises to Chapter 11 239 Glossary of Abbreviations 241 References 245 Index 251

Edward L. Wolf is Professor of Physics at the Polytechnic University in New York City. His long–term teaching experience ranges from undergraduate courses to the direction of thesis research. His research activities cover solid state physics, scanning tunneling microscopy, electron tunneling spectroscopy and superconductivity. Edward Wolf holds industrial and academic appointments. The former Director of the National Science Foundation is Fellow of the American Physical Society. He has authored over 100 refereed publications as well as a monograph on Electron Tunneling Spectroscopy and two successful texts on Nanophysics.

“With its comments on economic aspects, it is also a useful tool for those readers interested in a career in alternative energy.”  ( ETDE Energy Database , 1 November 2012)