Concentrator Photovoltaics (CPV) is one of the most promising technologies to produce solar electricity at competitive prices. High performing CPV systems with efficiencies well over 30% and multi-megawatt CPV plants are now a reality. As a result of these achievements, the global CPV market is expected to grow dramatically over the next few years reaching cumulative installed capacity of 12.5 GW by 2020. In this context, both new and consolidated players are moving fast to gain a strategic advantage in this emerging market.
Written with clear, brief and self-contained technical explanations, Handbook of Concentrator Photovoltaic Technology provides a complete overview of CPV covering: the fundamentals of solar radiation, solar cells, concentrator optics, modules and trackers; all aspects of characterization and reliability; case studies based on the description of actual systems and plants in the field; environmental impact, market potential and cost analysis.
CPV technology is at a key point of expansion. This timely handbook aims to provide a comprehensive assessment of all CPV scientific, technological and engineering background with a view to equipping engineers and industry professionals with all of the vital information they need to help them sustain the impetus of this encouraging technology.
Key features:
- Uniquely combines an explanation of the fundamentals of CPV systems and components with an overview of the market place and their real-life applications.
- Each chapter is written by well-known industry specialists with extensive expertise in each particular field of CPV technology.
- Reviews the basic concepts of multi-junction solar cells and new concepts for CPV cells, highlighting the key differences between them.
- Demonstrates the state of the art of several CPV centres and companies.
- Facilitates future cost calculation models for CPV.
- Features extensive case studies in each chapter, including coverage of CPV modules and systems.
Table of Contents
List of Contributors xix
Preface xxiii
1 Direct Normal Radiation 1
Daryl R. Myers
1.1 Concepts and Definitions 1
1.1.1 Orbital and Geometrical Considerations 1
1.1.2 The Solar Constant 2
1.1.3 Temporal Variations in Extraterrestrial Radiation (ETR) 3
1.1.4 Extraterrestrial Radiation Spectral Power Distribution 4
1.1.5 The Atmospheric Filter 6
1.2 Measuring Broadband Direct Solar Radiation 8
1.2.1 Pyrheliometers 8
1.2.2 Rotating Shadow Band Radiometers 11
1.2.3 Reference Standards, the World Radiometric Reference (WRR) 13
1.2.4 Calibration of Pyrheliometers 16
1.2.5 Accuracy and Uncertainty 17
1.2.6 Summary of Guide to Uncertainty in Measurement (GUM) Approach 18
1.2.7 Measurement Data Quality 20
1.3 Modeling Broadband Direct Solar Radiation 21
1.3.1 Models for Direct Beam Irradiance 21
1.3.2 Atmospheric Component Transmittance 22
1.3.3 Estimating Direct Beam Radiation from Hemispherical Data 25
1.4 Modeling Spectral Distributions 26
1.4.1 Bird Simple Spectral Model (SPCTRL2) 27
1.4.2 Simple Model for Atmospheric Transmission of Sunshine (SMARTS) 28
1.4.3 Spectral Distributions from Broadband Data 28
1.5 Resources for Broadband Estimates of CPV Performance 29
1.5.1 Broadband Direct Beam Radiation Data Resources 29
1.5.2 Typical Meteorological Year Data for CPV Performance Estimates 31
1.5.3 CPV Spectral Performance Issues 33
1.6 Sunshape 33
1.6.1 The Solar Disk 33
1.6.2 Circumsolar Radiation 36
1.6.3 Recent Circumsolar Radiation Research 39
1.7 Direct Solar Radiation Climates 40
1.7.1 Measurement Networks and Data 41
1.7.2 Concentrating Solar Power Site Selection 41
1.7.3 Concentrating Solar Power Resource Map Examples 43
1.7.4 Solar Resource Maps and Data Internet Resources 47
1.8 Consensus Standards for Direct Solar Radiation Applications 48
1.8.1 World Radiometric Reference 48
1.8.2 Solar Radiometric Instrumentation Calibration 48
1.8.3 Spectral Calibration Standards 49
1.8.4 Standard and Reference Spectral Distributions 49
Glossary 50
List of Acronyms 50
List of Symbols 51
References 53
2 Concentrator Multijunction Solar Cells 59
Ignacio Rey-Stolle, Jerry M. Olson, and Carlos Algora
2.1 Introduction 59
2.2 Fundamentals 60
2.2.1 Fundamentals of Photovoltaic Cells 60
2.2.2 Fundamentals of Multijunction Solar Cells 63
2.3 Multijunction Solar Cell Structures 67
2.3.1 Historical Development of Multijunction PV Converters 68
2.3.2 Designing Multijunction Solar Cell Structures 73
2.4 Multijunction Solar Cell Modeling 79
2.4.1 Numerical Modeling of Multijunction Solar Cell Structures 79
2.4.2 Analytical Modeling of Multijunction Solar Cells 81
2.4.3 Further Steps: Distributed Circuit-based Modeling 98
2.5 Concentrator Requirements 103
2.5.1 High Efficiency 103
2.5.2 Series Resistance. Grid Designs 107
2.5.3 Tunnel Junctions 110
2.5.4 Distributed Effects 113
2.5.5 Atmospheric Spectral Variations and Impact on Energy Yield 116
2.5.6 Temperature Effects 118
2.6 Description of Different Cell Approaches 118
2.6.1 Lattice-matched GaInP/GaAs/Ge 118
2.6.2 Metamorphic GaInP/GaInAs/Ge 119
2.6.3 Inverted Metamorphic GaInP/GaAs/GaInAs 120
2.6.4 Double Sided Epi 122
2.6.5 Lattice Matched GaInP/GaAs/GaInNAs 122
2.6.6 Quantum Dot and Quantum Well Multijunction Solar Cells 123
2.6.7 More Junctions (4, 5, 6) 123
2.6.8 Stacked Multijunction Cells 124
2.6.9 III-Vs on Silicon 124
2.6.10 Epitaxial Liftoff 126
Acknowledgements 127
Glossary 127
List of Acronyms 127
List of Symbols 127
References 129
3 Emerging High Efficiency Concepts for Concentrator Solar Cells 137
Ignacio Tobías and Antonio Luque
3.1 Introduction 137
3.2 Thermodynamic Efficiency Limits 138
3.2.1 Disequilibria and Energy Conversion in Solar Cells 140
3.2.2 Thermodynamic Efficiencies 142
3.3 Detailed Balance Modeling of Solar Cells 143
3.3.1 Shockley–Queisser Model of a Solar Cell 144
3.3.2 The System with Infinite Monochromatic Solar Cells 146
3.4 Solar Cell Concepts Exceeding the Single Junction Shockley–Queisser Limit 148
3.4.1 Multijunction Solar Cells 148
3.4.2 Hot Carrier Solar Cells 149
3.4.3 Carrier Multiplication or Multi-Exciton Generation Solar Cells 152
3.4.4 Intermediate Band Solar Cells 155
3.5 Other Concepts 159
3.5.1 Light Management for High Efficiency Photovoltaics 160
3.5.2 Spectrum Conversion 161
3.6 Nanostructures in Solar Cells 162
3.6.1 Electron States in Nanostructures 162
3.6.2 Light Absorption by Nanostructures 173
3.6.3 Relaxation, Capture and Recombination in Nanostructures 176
3.6.4 Nanostructures for Multijunction Solar Cells 177
3.6.5 Fabrication Techniques 178
Glossary 179
List of Acronyms 179
References 179
4 CPV Optics 187
Rubén Mohedano and Ralf Leutz
4.1 Introduction 187
4.2 Light, Optics and Concentration 188
4.2.1 Light and Optics 189
4.2.2 Optics for Concentration Photovoltaics 190
4.3 Optical Background 192
4.3.1 Basic Concepts in Geometrical Optics 192
4.3.2 Basic Concepts in Nonimaging Optics 196
4.4 Design of the Optical Train: Calculation of Surfaces 202
4.4.1 Types of Concentrators as a Function of Concentration Level 203
4.4.2 Design Examples 204
4.4.3 Secondary Optical Elements: Design Details 210
4.5 Performance Analysis and Optimization of the Optical Train 213
4.5.1 Efficiency. Sources of Losses 215
4.5.2 Ray Trace Modeling 220
4.6 Optics Manufacturing 224
4.6.1 Optical Materials for CPV 224
4.6.2 Tolerance Budget 226
4.6.3 Manufacturing of Primary Optical Elements 227
4.6.4 Manufacturing of Secondary Optic Elements 231
4.7 Impact of CPV Optics in a Nutshell 232
Glossary 233
List of Acronyms 233
List of Symbols 234
References 235
Annex 4-I: Étendue Calculation 239
Annex 4-II: 2D Treatment of Rotational and Linear 3D Optical Systems 241
Annex 4-III: Design of the XR Concentrator 242
5 Temperature Effects on CPV Solar Cells, Optics and Modules 245
Iván García, Marta Victoria, and Ignacio Antón
5.1 Introduction 245
5.2 Effects of Temperature on CPV Solar Cells 246
5.2.1 Dependence of the Bandgap on Temperature 246
5.2.2 Dependence of the Solar Cell Parameters on Temperature 248
5.2.3 Influence of Concentration on the Sensitivity to Temperature 260
5.2.4 Experimental Measurements on Real Solar Cells 261
5.2.5 Summary of Temperature Effects in CPV Multijunction Solar Cells 264
5.3 Temperature Effects and Thermal Management in CPV Optics and Modules 266
5.3.1 Temperature Effects on CPV Optics and Modules 266
5.3.2 Thermal Coefficients of CPV Modules 270
5.3.3 Heat Extraction Strategies 274
Glossary 286
List of Acronyms 286
List of Symbols 286
References 287
6 CPV Tracking and Trackers 293
Ignacio Luque-Heredia, Pedro Magalhães, and Matthew Muller
6.1 Introduction 293
6.2 Requirements and Specifications 294
6.3 Basic Taxonomy of CPV Trackers 297
6.4 Design of CPV Trackers – Structural Considerations 300
6.5 Sun Tracking Control 307
6.5.1 Background 307
6.5.2 The Autocalibrated Sun Tracking Control Unit 311
6.6 Sun Tracking Accuracy 315
6.6.1 The Tracking Accuracy Sensor 315
6.6.2 The Monitoring System 316
6.6.3 Accuracy Assessment: Example of the Autocalibrated Tracking Strategy 318
6.7 Designing for Optimal Manufacturing and Field Works 322
6.7.1 Manufacturing Considerations 322
6.7.2 Field Works Considerations 324
6.8 Description and Performance of Current Tracker Approaches 327
6.8.1 Parabolic Trough 327
6.8.2 Single-Pole Az.-El. Trackers 328
6.8.3 Tilt-Roll Trackers 330
6.8.4 Carrousel Trackers 331
6.8.5 Variations to Main Architectures in the Field 332
6.9 International Standards for Solar Trackers 334
References 337
7 CPV Modules 339
Stephen Askins and Gabriel Sala Pano
7.1 Introduction 339
7.2 What is a CPV Module? 339
7.3 Definition, Functions, and Structure of a CPV Module 341
7.3.1 Functions of a CPV Module 342
7.3.2 General Terms and Definitions 343
7.3.3 Structure of a CPV Module 343
7.4 Design Process and Prototyping Stages 349
7.5 Concentration Ratio and Cell Size 353
7.5.1 Concentration Ratio 353
7.5.2 Cell Size Selection 353
7.5.3 Module Size and Length 356
7.5.4 Market Survey 357
7.6 Opto-Mechanics of CPV Modules 359
7.6.1 Acceptance Angle 359
7.6.2 Acceptance Angle Budget 361
7.6.3 External Tolerances 362
7.6.4 Internal Tolerances 363
7.7 Electrical Design 372
7.7.1 Module Voltages and Dielectric Strength 372
7.7.2 Series Connections and Bypass Diodes 373
7.7.3 Parallel Connections and Blocking Diodes 374
7.8 Thermal Design 375
7.8.1 Target Cell Temperature 376
7.8.2 Simplified Thermal Model 377
7.9 Venting Considerations 389
7.10 Manufacturing Processes for CPV Modules 390
7.10.1 Chassis and Backplane Fabrication 390
7.10.2 Heat Sink Fabrication 395
7.10.3 Module Assembly 398
7.11 Standards Applicable to CPV Modules 399
Glossary 401
References 403
Annex 7-I: Abengoa’s CPV Modules and Systems 406
José A. Pérez, Sebastián Caparrós, Justo Albarrán, and Antonio de Dios
Annex 7-II: CPV Modules and Systems from Daido Steel 413
Kenji Araki
Annex 7-III: Soitec CPV Modules and Systems 419
Francisca Rubio, Sven T. Wanka, and Andreas Gombert
Annex 7-IV: Suncore Photovoltaics’ CPV Modules 426
James Foresi
8 CPV Power Plants 433
María Martínez, Daniel Sánchez, Francisca Rubio, Eduardo F. Fernández, Florencia Almonacid, Norman Abela, Tobias Zech, and Tobias Gerstmaier
8.1 Introduction 433
8.2 Construction of CPV Plants 434
8.2.1 Preliminary Works 434
8.2.2 Basic Engineering Study 436
8.2.3 Detailed Engineering 437
8.2.4 Construction Phase 440
8.3 CPV Inverters: Configurations and Sizing 445
8.3.1 Types of Configurations 446
8.3.2 Sizing of the Inverter 448
8.4 Optimized Distribution of Trackers 450
8.4.1 State of the Art 451
8.4.2 Procedure for Optimizing the Distribution of Trackers 452
8.5 Considerations of Environmental Impact and Dual Use of the Land 456
8.6 CPV Plant Monitoring and Production Data Analysis 458
8.6.1 Monitoring System: Registering the Operating Parameters 459
8.6.2 Monitoring System: Controlling a CPV Plant 460
8.6.3 Analysis of Production Data 461
8.7 Operation and Maintenance 464
8.7.1 Operation 465
8.7.2 Maintenance 467
8.8 Power Rating of a CPV Plant 470
8.8.1 ISFOC Approach 470
8.8.2 International ASTM Standards 471
8.8.3 International IEC Standards 472
8.9 Modeling the Energy Production of CPV Power Plants 477
8.9.1 Basic Models 477
8.9.2 Input Data and Quality Checks 478
8.9.3 Loss Mechanisms 479
Glossary 484
List of Acronyms 484
List of Symbols 485
References 486
Annex 8-I: Software Tools for CPV Plant Design and Analysis 491
Annex 8-II: CPV Power Plants at ISFOC 501
María Martínez, Daniel Sánchez, Óscar de la Rubia, and Francisca Rubio
Annex 8-III: Soitec Power Plants 513
Andreas Gombert, Norman Abela, Tobias Gerstmeier, Shelley Bambrook, and Francisca Rubio
9 Reliability 521
Carlos Algora, Pilar Espinet-Gonzalez, Manuel Vázquez, Nick Bosco, David Miller, Sarah Kurtz, Francisca Rubio, and Robert McConnell
9.1 Introduction 521
9.2 Fundamentals of Reliability 521
9.2.1 Reliability Functions 522
9.2.2 Statistical Distribution Functions 524
9.2.3 Accelerated Life Tests 529
9.2.4 Reliability Versus Qualification 532
9.3 Reliability of Solar Cells 533
9.3.1 Issues in Accelerated Aging Tests in CPV Solar Cells 533
9.3.2 Types of Failure 538
9.3.3 Failures in Real Time Operation 539
9.3.4 Accelerated Life Tests 539
9.3.5 Reliability of Similar Devices 546
9.3.6 Links Among Degradation Studies, Reliability and Qualification Standards 548
9.4 Reliability of Modules 549
9.4.1 Introduction 549
9.4.2 Die-attach 549
9.4.3 CPV Encapsulation 552
9.4.4 CPV Optics 555
9.4.5 Other CPV Module Reliability Issues 562
9.5 Reliability of Systems and Plants 562
9.5.1 Performance Degradation in Power Plants 563
9.5.2 Failures of Components 568
9.5.3 Qualification Tests on Power Plants Components 572
9.5.4 Aging Tests 575
9.6 Standards Development for CPV 577
9.6.1 Standards as the Mark of a Mature Industry 577
9.6.2 History of CPV Standards Development 577
Acknowledgement 582
References 582
10 CPV Multijunction Solar Cell Characterization 589
Carl R. Osterwald and Gerald Siefer
10.1 Introduction 589
10.2 Basic Concepts About Multijunction Solar Cells for Characterization Purposes 590
10.2.1 Review of Multijunction Solar Cell Theory 590
10.2.2 Definition of CPV Cell Efficiency 592
10.2.3 Current-Voltage as a Function of Concentration 593
10.3 Spectral Matching and Adjustment 594
10.3.1 Isotype Method 594
10.3.2 Reference Cell Method 594
10.3.3 Rij Method and Linear Equation System Method 595
10.3.4 Effects of Subcell Mismatching 597
10.4 Flash Solar Simulators: Description and Limitations 600
10.4.1 Sources and Optics 600
10.4.2 Adjusting Total Intensity 600
10.4.3 Irradiance Versus Time 600
10.4.4 Spectral Irradiance Adjustment 601
10.4.5 Spectral Irradiance Measurement 602
10.5 Concentrator Solar Cell Characterization 603
10.5.1 Overview 603
10.5.2 Area Measurement 603
10.5.3 External Quantum Efficiency 604
10.5.4 One-Sun Light I-V and One-Sun Short Circuit Current Calibration 607
10.5.5 Concentration I-V 608
10.5.6 Uncertainty Analysis 608
10.5.7 Open Challenges 610
Acknowledgments 611
Glossary 611
List of Acronyms 611
List of Symbols 611
References 612
11 Characterization of Optics for Concentrator Photovoltaics 615
Maikel Hernández
11.1 Introduction 615
11.2 Geometrical Characterization 616
11.2.1 Faceted Optics 617
11.2.2 Non-faceted Optics 620
11.3 Optical Characterization 624
11.3.1 Measurement of the Optical Efficiency 624
11.3.2 POE Scattering Basic Measurements 628
11.3.3 Acceptance Angle Measurement 629
11.3.4 Spectral Irradiance Distribution Measurement at the Solar Cell Plane 633
11.3.5 Angular Power Distribution at the Solar Cell Plane 634
11.3.6 In-line Characterization of Optics in Production 634
Glossary 636
List of Acronyms 636
List of Symbols 636
References 637
12 Characterization of CPV Modules and Receivers 639
César Domínguez, Rebeca Herrero, and Ignacio Antón
12.1 Introduction 639
12.2 Figures of Merit of PV Concentrators 640
12.2.1 Reporting CPV Module Performance 640
12.2.2 Performance Indicators for Concentrator Optics 642
12.3 Instruments and Methods for CPV Characterization 643
12.3.1 Indoors versus Outdoors 643
12.3.2 Operating Conditions Relevant to CPV 644
12.3.3 Tracker Requirements 650
12.3.4 Alignment Procedures 651
12.3.5 Rating CPV Module Performance 652
12.3.6 Spectral Characterization of CPV Modules and Receivers 656
12.3.7 Angular Transmission Curve 660
12.3.8 Uncertainties of Instruments and Methods for CPV Characterization 662
12.4 Indoor Measurements of CPV Modules 663
12.4.1 Solar Simulators for CPV Modules 663
12.4.2 Reference Sensor 668
12.4.3 Caveats on Indoor Measurements 672
12.4.4 Angular Transmission Curve: Direct and Inverse Methods 674
12.4.5 Uncertainties in the Indoor Measurement of I-V Curves 678
Glossary 678
List of Acronyms 678
List of Symbols 678
References 679
13 Life Cycle Analysis of CPV Systems 685
Vasilis Fthenakis
13.1 Introduction 685
13.2 Case Study Description 686
13.3 Methodology 687
13.4 Life-Cycle Inventory Analysis 688
13.4.1 Production of Materials and Associated Emissions 688
13.4.2 Solar Cell Manufacturing 690
13.4.3 Primary Energy Demand 692
13.4.4 End-of-Life Processing 693
13.5 System Performance Data and Estimates 694
13.6 Energy Payback Time 695
13.7 Greenhouse and Toxic Gas Emissions 696
13.7.1 Emissions in the Life-Cycle of Amonix 7700 696
13.7.2 Reduction of Emissions from PV Replacing Electricity from the Grid 697
13.8 Land and Water Use in CPV Systems 699
13.9 Discussion and Comparison with Other CPV and PV Systems 700
13.9.1 Comparison with Other CPV Systems 700
13.9.2 Comparison with Other PV Systems 701
Glossary 702
List of Acronyms 702
List of Symbols 702
References 703
Annex 13-I: Energy Flow Diagrams for Amonix 7700 System Components 705
14 Cost Analysis 711
Carlos Algora, Diego L. Talavera, and Gustavo Nofuentes
14.1 Introduction 711
14.2 Basic Concepts of Cost and Profitability Analysis 711
14.2.1 Elements of the Investment 712
14.2.2 Present and Future Worth of Sums. The Impact of Inflation 712
14.2.3 The Discount Rate 713
14.2.4 Effect of Inflation 713
14.2.5 Impact of Taxation 714
14.2.6 Financing 714
14.3 Review of Profitability Analysis 715
14.3.1 The Life Cycle Cost of a CPV System 715
14.3.2 The Present Worth of the Cash Inflows Generated by a CPV System 717
14.3.3 Assessment of the Profitability of a CPV System 718
14.3.4 Sensitivity Analysis on the Profitability of CPV Systems 720
14.4 The Cost of CPV 728
14.4.1 The Cost of CPV Systems 728
14.4.2 Levelized Cost of Electricity (LCOE) of CPV 735
14.4.3 Towards the CPV Grid Parity 746
Glossary 754
References 756
Index 759
