Photovoltaics

A comprehensive tutorial on photovoltaic technology now fully updated to include solar storage and the latest methods for on-site plant measurementsStarting with the basic principles of solar energy, this fully updated, practical text explains the fundamentals of semiconductor physics and the structure and functioning of the solar cell. It describes the latest measurement techniques for solar modules, and the planning and operation of grid-connected and off-grid PV systems.It also looks at other thin film cells, hybrid wafer cells, and concentrator systems. Additionally, this Second Edition covers solar modules and solar generators; system technology of grid connected plants; the storage of solar energy; photovoltaic measurement technology; the planning and operation of grid-connected systems; economic efficiency of PV systems; and the future development of PV.* Presents the latest advances in PV R&D and industry deployment* Updated illustrations and tabular data reflect current state-of-the-art and PV technology efficiencies* Offers expanded tutorial sections to aid teaching and self-study* Includes a brand-new chapter on Solar Energy Storage* Features two enlarged chapters--one on up-to-date photovoltaic metrology and the other on the future developments in photovoltaics* Comes along with the accompanying website textbook-pv.org which offers free downloadable figures of the book, solutions of exercises, additional free PV software etc.Developed to prepare engineering students for the PV industry, this practical text is an essential PV primer.

Preface to the First International Edition xvPreface to the Second International Edition xviiAbbreviations xix1 Introduction 11.1 Introduction 11.1.1 Why Photovoltaics? 11.1.2 Who Should Read This Book? 21.1.3 Structure of the Book 21.2 What Is Energy? 31.2.1 Definition of Energy 31.2.2 Units of Energy 41.2.3 Primary, Secondary, and End Energy 51.2.4 Energy Content of Various Substances 61.3 Problems with Today's Energy Supply 71.3.1 Growing Energy Requirements 71.3.2 Tightening of Resources 81.3.3 Climate Change 91.3.4 Hazards and Disposal 111.4 Renewable Energies 111.4.1 The Family of Renewable Energies 111.4.2 Advantages and Disadvantages of Renewable Energies 121.4.3 Previous Development of Renewable Energies 131.5 Photovoltaics - The Most Important in Brief 131.5.1 What Does "Photovoltaics" Mean? 131.5.2 What Are Solar Cells and Solar Modules? 141.5.3 How Is a Typical Photovoltaic Plant Structured? 141.5.4 What Does a Photovoltaic Plant "Bring?" 151.6 History of Photovoltaics 161.6.1 How It all Began 161.6.2 The First Real Solar Cells 171.6.3 From Space to Earth 191.6.4 From Toy to Energy Source 202 Solar Radiation 232.1 Properties of Solar Radiation 232.1.1 Solar Constant 232.1.2 Spectrum of the Sun 232.1.3 Air Mass 252.2 Global Radiation 252.2.1 Origin of Global Radiation 252.2.2 Contributions of Diffuse and Direct Radiation 262.2.3 Global Radiation Maps 282.3 Calculation of the Position of the Sun 302.3.1 Declination of the Sun 302.3.2 Calculating the Path of the Sun 322.4 Radiation on Tilted Surfaces 352.4.1 Radiation Calculation with the Three-component Model 352.4.1.1 Direct Radiation 352.4.1.2 Diffuse Radiation 362.4.1.3 Reflected Radiation 372.4.2 Radiation Estimates with Diagrams and Tables 382.4.3 Yield Gain through Tracking 412.5 Radiation Availability and World Energy Consumption 412.5.1 The Solar Radiation Energy Cube 412.5.2 The Sahara Miracle 453 Fundamentals of Semiconductor Physics 473.1 Structure of a Semiconductor 473.1.1 Bohr's Atomic Model 473.1.2 Periodic Table of Elements 493.1.3 Structure of the Silicon Crystal 493.1.4 Compound Semiconductors 493.2 Band Model of a Semiconductor 513.2.1 Origin of Energy Bands 513.2.2 Differences in Isolators, Semiconductors, and Conductors 533.2.3 Intrinsic Carrier Concentration 533.3 Charge Transport in Semiconductors 553.3.1 Field Currents 553.3.2 Diffusion Currents 563.4 Doping of Semiconductors 573.4.1 n-Doping 573.4.2 p-Doping 583.5 The p-n Junction 593.5.1 Principle of Method of Operation 593.5.2 Band Diagram of the p-n Junction 613.5.3 Behavior with Applied Voltage 623.5.4 Diode Characteristics 633.6 Interaction of Light and Semiconductors 643.6.1 Phenomenon of Light Absorption 643.6.1.1 Absorption Coeffcient 653.6.1.2 Direct and Indirect Semiconductors 653.6.2 Light Reflection on Surfaces 673.6.2.1 Reflection Factor 673.6.2.2 Antireflection Coating 694 Structure and Method of Operation of Solar Cells 714.1 Consideration of the Photodiode 714.1.1 Structure and Characteristics 714.1.2 Equivalent Circuit 734.2 Method of Function of the Solar Cell 734.2.1 Principle of the Structure 734.2.2 Recombination and Diffusion Length 744.2.3 What Happens in the Individual Cell Regions? 754.2.3.1 Absorption in the Emitter 754.2.3.2 Absorption in the Space Charge Region 764.2.3.3 Absorption Within the Diffusion Length of the Electrons 764.2.3.4 Absorption Outside the Diffusion Length of the Electrons 764.2.4 Back-surface Field 774.3 Photocurrent 774.3.1 Absorption Efficiency 784.3.2 Quantum Efficiency 794.3.3 Spectral Sensitivity 794.4 Characteristic Curve and Characteristic Parameters 804.4.1 Short-circuit Current ISC 814.4.2 Open-circuit Voltage V OC 824.4.3 Maximum Power Point (MPP) 824.4.4 Fill Factor (FF) 824.4.5 Efficiency eta 834.4.6 Temperature Dependence of Solar Cells 834.5 Electrical Description of Real Solar Cells 854.5.1 Simplified Model 854.5.2 Standard Model (Single-diode Model) 864.5.3 Two-diode Model 864.5.4 Determining the Parameters of the Equivalent Circuit 884.6 Considering Efficiency 904.6.1 Spectral Efficiency 914.6.2 Theoretical Efficiency 944.6.3 Losses in Real Solar Cells 964.6.3.1 Optical Losses, Reflection on the Surface 964.6.3.2 Electrical Losses and Ohmic Losses 984.7 High-efficiency Cells 994.7.1 Buried-contact Cell 994.7.2 Point-contact Cell (IBC Cell) 994.7.3 PERL and PERC Cell 1015 Cell Technologies 1035.1 Production of Crystalline Silicon Cells 1035.1.1 From Sand to Silicon 1035.1.1.1 Production of Polysilicon 1035.1.1.2 Production of Monocrystalline Silicon 1055.1.1.3 Production of Multicrystalline Silicon 1065.1.2 From Silicon to Wafer 1075.1.2.1 Wafer Production 1075.1.2.2 Wafers from Ribbon Silicon 1075.1.3 Production of Standard Solar Cells 1085.1.4 Production of Solar Modules 1115.2 Cells of Amorphous Silicon 1125.2.1 Properties of Amorphous Silicon 1125.2.2 Production Process 1135.2.3 Structure of the Pin Cell 1135.2.4 Staebler-Wronski Effect 1155.2.5 Stacked Cells 1165.2.6 Combined Cells of Micromorphous Material 1185.2.7 Integrated Series Connection 1195.3 Further Thin Film Cells 1205.3.1 Cells of Cadmium-Telluride 1205.3.2 CIS Cells 1215.4 Hybrid Wafer Cells 1235.4.1 Combination of c-Si and a-Si (HIT Cell) 1235.4.2 Stacked Cells of III/V Semiconductors 1245.5 Other Cell Concepts 1255.6 Concentrator Systems 1265.6.1 Principle of Radiation Bundling 1265.6.2 What Is the Advantage of Concentration? 1275.6.3 Examples of Concentrator Systems 1285.6.4 Advantages and Disadvantages of Concentrator Systems 1285.7 Ecological Questions on Cell and Module Production 1295.7.1 Environmental Effects of Production and Operation 1295.7.1.1 Example of Cadmium-Telluride 1295.7.1.2 Example of Silicon 1295.7.2 Availability of Materials 1305.7.2.1 Silicon 1305.7.2.2 Cadmium-Telluride 1315.7.2.3 Cadmium Indium Selenide 1315.7.2.4 III/V Semiconductors 1325.7.3 Energy Amortization Time and Yield Factor 1325.8 Summary 1356 Solar Modules and Solar Generators 1396.1 Properties of Solar Modules 1396.1.1 Solar Cell Characteristic Curve in All Four Quadrants 1396.1.2 Parallel Connection of Cells 1396.1.3 Series Connection of Cells 1416.1.4 Use of Bypass Diodes 1426.1.4.1 Reducing Shading Losses 1426.1.4.2 Prevention of Hotspots 1446.1.5 Typical Characteristic Curves of Solar Modules 1476.1.5.1 Variation of the Irradiance 1476.1.5.2 Temperature Behavior 1476.1.6 Special Case Thin-film Modules 1496.1.7 Examples of Data Sheet Information 1506.2 Connecting Solar Modules 1506.2.1 Parallel Connection of Strings 1506.2.2 What Happens in Case of Cabling Errors? 1526.2.3 Losses Due to Mismatching 1536.2.4 Smart Installation in Case of Shading 1536.3 Direct Current Components 1566.3.1 Principle of Plant Construction 1566.3.2 Direct Current Cabling 1566.4 Types of Plants 1586.4.1 Ground-mounted Plants 1586.4.2 Flat-roof Plants 1616.4.3 Pitched-roof Systems 1626.4.4 Facade Systems 1647 System Technology of Grid-connected Plants 1657.1 Solar Generator and Load 1657.1.1 Resistive Load 1657.1.2 DC/DC Converter 1667.1.2.1 Idea 1667.1.2.2 Buck Converter 1667.1.2.3 Boost Converter 1697.1.3 MPP Tracker 1717.2 Construction of Grid-connected Systems 1727.2.1 Feed-in Variations 1727.2.2 Plant Concepts 1737.3 Construction of Inverters 1747.3.1 Tasks of the Inverter 1757.3.2 Line-commutated and Self-commutated Inverter 1757.3.3 Inverters Without Transformers 1757.3.4 Inverters with Mains Transformer 1777.3.5 Inverters with HF Transformer 1787.3.6 Three-phase Feed-in 1797.3.7 Further Clever Concepts 1807.4 Efficiency of Inverters 1817.4.1 Conversion Efficiency 1817.4.2 European Efficiency 1847.4.3 Clever MPP Tracking 1857.5 Dimensioning of Inverters 1867.5.1 Power Dimensioning 1867.5.2 Voltage Dimensioning 1877.5.3 Current Dimensioning 1887.6 Requirements of the Grid Operators 1887.6.1 Prevention of Stand-Alone Operation 1887.6.2 Maximum Feed-in Power 1907.6.3 Reactive Power Provision 1917.7 Safety Aspects 1947.7.1 Earthing of the Generator and Lightning Protection 1947.7.2 Fire Protection 1948 Storage of Solar Energy 1978.1 Principle of Solar Storage 1978.2 Batteries 1988.2.1 Lead-acid Battery 1998.2.1.1 Principle and Build-up 1998.2.1.2 Types of Lead Batteries 2018.2.1.3 Battery Capacity 2038.2.1.4 Voltage Progression 2038.2.1.5 Summary 2048.2.2 Charge Controllers 2048.2.2.1 Series Controller 2048.2.2.2 Shunt Controller 2058.2.2.3 MPP Controller 2058.2.2.4 Examples of Products 2068.2.3 Lithium Ion Battery 2068.2.3.1 Principle and Build-up 2078.2.3.2 Reactions During Charging and Discharging 2088.2.3.3 Material Combinations and Cell Voltage 2098.2.3.4 Safety Aspects 2108.2.3.5 Charging Procedures 2118.2.3.6 Battery Design 2118.2.3.7 Lifespan 2128.2.3.8 Application Areas 2138.2.3.9 Summary 2138.2.4 Sodium Sulfur Battery 2138.2.4.1 Principle and Build-up 2138.2.4.2 Peculiarities of the High Temperature Battery 2148.2.4.3 Sodium Sulfur Batteries in Practice 2158.2.4.4 Summary 2168.2.5 Redox Flow Battery 2168.2.5.1 Principle and Build-up 2168.2.5.2 Behavior in Practice 2188.2.5.3 Concrete Applications 2198.2.5.4 Summary 2208.2.6 Comparison of the Different Battery Types 2208.3 Storage Use for Increase of Self-consumption 2208.3.1 Self-consumption in Domestic Households 2218.3.1.1 Solution Without Storage 2228.3.1.2 Solution with Storage 2238.3.1.3 Examples of Storage Systems 2238.3.1.4 How Much Cost a Kilowatt-Hour? 2258.3.1.5 The Smart Home 2268.3.2 Self-consumption in Commercial Enterprises 2278.3.2.1 Example Production Factory 2278.3.2.2 Example Hospital 2278.4 Storage Deployment from the Point of View of the Grid 2288.4.1 Peak-shaving with Storages 2298.4.2 Governmental Funding Program for Solar Storages 2298.5 Stand-alone Systems 2328.5.1 Principal Structure 2328.5.2 Examples of Stand-alone Systems 2328.5.2.1 Solar Home Systems 2328.5.2.2 Hybrid Systems 2348.5.3 Dimensioning Stand-alone Plants 2358.5.3.1 Acquiring the Energy Consumption 2358.5.3.2 Dimensioning the PV Generator 2368.5.3.3 Selecting the Battery 2389 Photovoltaic Metrology 2419.1 Measurement of Solar Radiation 2419.1.1 Global Radiation Sensors 2419.1.1.1 Pyranometer 2419.1.1.2 Radiation Sensors from Solar Cells 2439.1.2 Measuring Direct and Diffuse Radiation 2449.2 Measuring the Power of Solar Modules 2459.2.1 Build-up of a Solar Module Power Test Rig 2459.2.2 Quality Classification of Module Flashers 2469.2.3 Determination of the Module Parameters 2479.3 Peak Power Measurement at Site 2489.3.1 Principle of Peak Power Measurement 2489.3.2 Possibilities and Limits of the Measurement Principle 2489.4 Thermographic Measuring Technology 2499.4.1 Principle of Infrared Temperature Measurement 2509.4.2 Bright Thermography of Solar Modules 2519.4.3 Dark Thermography 2549.5 Electroluminescence Measuring Technology 2549.5.1 Principle of Measurement 2549.5.2 Examples of Photos 2559.5.3 Low-cost Outdoor Electroluminescence Measurements 2579.6 Analysis of Potential Induced Degradation (PID) 2599.6.1 Explanation of the PID Effect 2609.6.2 Test of Modules for PID 2629.6.3 EL Investigations to PID 26310 Design and Operation of Grid-connected Plants 26510.1 Planning and Dimensioning 26510.1.1 Selection of Site 26510.1.2 Shading 26510.1.2.1 Shading Analysis 26610.1.2.2 Near Shading 26610.1.2.3 Self-shading 26810.1.2.4 Optimized String Connection 26910.1.3 Plant Dimensioning and Simulation Programs 27010.1.3.1 Inverter Design Tools 27010.1.3.2 Simulation Programs for Photovoltaic Plants 27010.2 Economics of Photovoltaic Plants 27210.2.1 The Renewable Energy Law 27310.2.2 Return Calculation 27310.2.2.1 Input Parameters 27310.2.2.2 Amortization Time 27410.2.2.3 Property Return 27410.2.2.4 Profit Increase Through Self-consumption of Solar Power 27610.2.2.5 Further Influences 27610.3 Surveillance, Monitoring, and Visualization 27710.3.1 Methods of Plant Surveillance 27710.3.2 Monitoring PV Plants 27810.3.2.1 Specific Yields 27810.3.2.2 Losses 27910.3.2.3 Performance Ratio 27910.3.2.4 Concrete Measures for Monitoring 28010.3.3 Visualization 28010.4 Operating Results of Actual Installations 28110.4.1 Pitched Roof Installation from 1996 28110.4.2 Pitched Roof Installation from 2002 28210.4.3 Flat Roof from 2008 28311 Future Development 28511.1 Potential of Photovoltaics 28511.1.1 Theoretical Potential 28511.1.2 Technically Useful Radiation Energy 28511.1.2.1 Roofs 28611.1.2.2 Facades 28611.1.2.3 Traffic Routes 28711.1.2.4 Free Areas 28711.1.3 Technical Electrical Energy Generation Potential 28711.1.4 Photovoltaics versus Biomass 28811.2 Efficient Promotion Instruments 28911.3 Price and Feed-in Tariff Development 29011.3.1 Price Development of Solar Modules 29011.3.2 Development of Feed-in Tariffs 29211.4 Renewable Energies in Today's Power Supply System 29211.4.1 Structure of Electricity Generation 29311.4.2 Types of Power Plants and Control Energy 29311.4.3 Interplay Between Sun and Wind 29411.4.4 Exemplary Electricity Generation Courses 29511.5 Thoughts on Future Energy Supply 29811.5.1 Consideration of Different Future Scenarios 29811.5.2 Options to Store Electrical Energy 30111.5.2.1 Pumped Storage Power Plants 30111.5.2.2 Compressed Air Storage 30111.5.2.3 Battery Storage 30211.5.2.4 Electric Mobility 30211.5.2.5 Hydrogen as Storage 30211.5.2.6 Power to Gas: Methanation 30311.5.3 Alternatives to Storage 30411.5.3.1 Active Load Management by Smart Grids 30411.5.3.2 Expansion of the Electricity Grids 30411.5.3.3 Limitation of the Feed-in Power 30411.5.3.4 Use of Flexible Power Plants 30411.6 Conclusion 30512 Exercises 307A Solar Radiation Diagrams 317B Checklist for Planning, Installing, and Operating a Photovoltaic Plant 327C Physical Constants/Material Parameters 329References 331Further Information on Photovoltaics 339Index 341