Provides practical guidance on the latest quality assurance and accelerated stress test methods for improved long-term performance prediction of PV modules
This book has been written from a historical perspective to guide readers through how the PV industry learned what the failure and degradation modes of PV modules were, how accelerated tests were developed to cause the same failures and degradations in the laboratory, and then how these tests were used as tools to guide the design and fabrication of reliable and long-life modules.
Photovoltaic Module Reliability starts with a brief history of photovoltaics, discussing some of the different types of materials and devices used for commercial solar cells. It then goes on to offer chapters on: Module Failure Modes; Development of Accelerated Stress Tests; Qualification Testing; and Failure Analysis Tools. Next, it examines the use of quality management systems to manufacture PV modules. Subsequent chapters cover the PVQAT Effort; the Conformity Assessment and IECRE; and Predicting PV Module Service Life. The book finishes with a look at what the future holds for PV.
- A comprehensive treatment of current photovoltaic (PV) technology reliability and necessary improvement to become a significant part of the electric utility supply system
- Well documented with experimental and practical cases throughout, enhancing relevance to both scientific community and industry
- Timely contribution to the harmonization of methodological aspects of PV reliability evaluation with test procedures implemented to certify PV module quality
- Written by a leading international authority in PV module reliability
Photovoltaic Module Reliability is an excellent book for anyone interested in PV module reliability, including those working directly on PV module and system reliability and preparing to purchase modules for deployment.
Table of Contents
Acknowledgments xi
1 Introduction 1
1.1 Brief History of PVs 2
1.2 Types of PV Cells 4
1.3 Module Packaging - Purpose and Types 8
1.4 What Does Reliability Mean for PV Modules? 12
1.5 Preview of the Book 13
References 15
2 Module Failure Modes 17
2.1 Broken Interconnects 17
2.2 Broken/Cracked Cells and Snail Trails 21
2.3 Delamination 24
2.4 Corrosion of Cell Metallization 26
2.5 Encapsulant Discoloration 28
2.6 Failure of Electrical Bonds Particularly Solder Bonds 31
2.7 Glass Breakage 33
2.8 Junction Box Problems 35
2.9 Loss of Elastomeric Properties of Back Sheets 36
2.10 Reverse Bias Hot Spots 37
2.11 By-Pass Diodes 39
2.12 Structural Failures 41
2.13 Ground Faults and Open Circuits Leading to Arcing 43
2.14 Potential Induced Degradation 46
2.15 Thin-Film Specific Defects 48
2.15.1 Light-Induced Degradation 48
2.15.2 Inadequate Edge Deletion 49
2.15.3 Shunts at Laser Scribes and Impurities in Thin Film 49
2.15.4 Failure of Edge Seals 50
References 51
3 Development of Accelerated Stress Tests 55
3.1 Thermal Cycling or Change in Temperature 57
3.2 Damp Heat 58
3.3 Humidity Freeze 59
3.4 Ultraviolet (UV) Light Exposure 60
3.5 Static Mechanical Load 61
3.6 Cyclic (Dynamic) Mechanical Load 62
3.7 Reverse Bias Hot Spot Test 63
3.8 Bypass Diode Thermal Test 63
3.9 Hail Test 64
References 65
4 Qualification Testing 67
4.1 JPL Block Buy Program 68
4.2 Evolution of IEC 61215 Qualification Test Sequence 75
4.3 IEC 61215 Test Protocol 80
4.3.1 MQT 01 - Visual Inspection 82
4.3.2 MQT 02 - Maximum Power Determination 82
4.3.3 MQT 03 - Insulation Test 82
4.3.4 MQT 04 - Measurement of Temperature Coefficients 83
4.3.5 MQT 05 - Measurement of NMOT 83
4.3.6 MQT 06 - Performance at STC and NMOT 84
4.3.7 MQT 07 - Performance at Low Irradiance 84
4.3.8 MQT 08 - Outdoor Exposure Test 85
4.3.9 MQT 09 - Hot Spot Endurance Test 85
4.3.10 MQT 10 - UV Preconditioning Test 88
4.3.11 MQT 11 - Thermal Cycling Test 88
4.3.12 MQT 12 - Humidity-Freeze Test 89
4.3.13 MQT 13 - Damp-Heat Test 89
4.3.14 MQT 14 - Robustness of Termination 90
4.3.15 MQT 15 - Wet Leakage Current Test 91
4.3.16 MQT 16 - Static Mechanical Load Test 91
4.3.17 MQT 17 - Hail Test 92
4.3.18 MQT 18 - Bypass Diode Test 92
4.3.19 MQT 19 - Stabilization 94
4.4 How Qualification Tests have been Critical to Improving the Reliability and Durability of PV Modules 95
4.5 Limitations of the Qualification Tests 97
4.6 PV Module Safety Certification 98
4.6.1 Construction Requirements: IEC 61730-1 99
4.6.1.1 Components 99
4.6.1.2 Mechanical and Electromechanical Connections 101
4.6.1.3 Materials 103
4.6.1.4 Protection Against Electric Shock 105
4.6.2 Requirements of Testing IEC 61730-2 110
4.6.2.1 MST 01 - Visual Inspection 113
4.6.2.2 MST 02 - Performance at STC 113
4.6.2.3 MST 03 - Maximum Power Determination 114
4.6.2.4 MST 04 - Insulation Thickness Test 114
4.6.2.5 MST 05 - Durability of Markings Test 114
4.6.2.6 MST 06 - Sharp Edge Test 114
4.6.2.7 MST 07 - Bypass Diode Functionality Test 114
4.6.2.8 MST 11 - Accessibility Test 114
4.6.2.9 MST 12 - Cut Susceptibility Test 115
4.6.2.10 MST 13 - Continuity Test of Equipotential Bonding 115
4.6.2.11 MST 14 - Impulse Voltage Test 115
4.6.2.12 MST 16 - Insulation Test 116
4.6.2.13 MST 17 - Wet Leakage Current Test 116
4.6.2.14 MST 21 - Temperature Test 116
4.6.2.15 MST 22 - Hot Spot Endurance Test 117
4.6.2.16 MST 24 - Ignitability Test 117
4.6.2.17 MST 25 - Bypass Diode Thermal Test 117
4.6.2.18 MST 26 - Reverse Current Overload Test 117
4.6.2.19 MST 32 - Mechanical Breakage Test 118
4.6.2.20 MST 33 - Screw Connections Test - Test for General Screw Connections MST 33a 118
4.6.2.21 MST 33 - Screw Connections Test - Test for Locking Screws MST 33b 119
4.6.2.22 MST 34 - Static Mechanical Load Test 119
4.6.2.23 MST 35 - Peel Test 119
4.6.2.24 MST 36 - Lap Shear Strength Test 120
4.6.2.25 MST 37 - Materials Creep Test 121
4.6.2.26 MST 42 - Robustness of Termination Test 121
4.6.2.27 MST 51 - Thermal Cycling Test 121
4.6.2.28 MST 52 - Humidity Freeze Test 121
4.6.2.29 MST 53 - Damp Heat Test 121
4.6.2.30 MST 54 - UV Test 122
4.6.2.31 MST 55 - Cold Conditioning 122
4.6.2.32 MST 56 - Dry Heat Conditioning 122
4.6.2.33 Recommendations for Testing of PV Modules from Production 122
References 123
5 Failure Analysis Tools 127
5.1 PV Performance - Analysis of Light I-V Curves 127
5.2 Performance as a Function of Irradiance 132
5.3 Dark I-V Curves 136
5.4 Visual Inspection 137
5.5 Infrared (IR) Inspection 143
5.6 Electroluminescence (EL) 145
5.7 Adhesion of Layers, Boxes, Frames, etc. 149
References 149
6 Using Quality Management Systems to Manufacture PV Modules 151
6.1 Quality Management Systems 151
6.2 Using ISO 9000 and IEC 61215 153
6.3 Why just Using IEC 61215 and ISO 9000 is No Longer Considered Adequate? 154
6.4 Customer Defined “Do It Yourself” Quality Management and Qualification Systems (IEC 61215 on Steroids) 156
6.5 Problems with the “Do It Yourself” System 157
References 163
7 The PVQAT Effort 165
7.1 Task Group 1: PV QA Guidelines for Module Manufacturing 167
7.2 Task Group 2: Testing for Thermal and Mechanical Fatigue 169
7.3 Task Group 3: Testing for Humidity, Temperature and Voltage 175
7.3.1 Corrosion 176
7.3.2 Delamination 177
7.3.3 PID 179
7.3.4 Delamination Due to Voltage Stress 181
7.4 Task Group 4: Testing for Diodes, Shading and Reverse Bias 182
7.5 Task Group 5: Testing for UV, Temperature and Humidity 186
7.6 Task Group 6: Communications of Rating Information 189
7.7 Task Group 7: Testing for Snow and Wind Load 189
7.8 Task Group 8: Testing for Thin-Film Modules 190
7.9 Task Group 9: Testing for Concentrator Photovoltaic (CPV) 190
7.10 Task Group 10: Testing for Connectors 190
7.11 Task Group 11: QA for PV Systems 191
7.12 Task Group 12: Soiling and Dust 191
7.13 Task Group 13: Cells 192
References 192
8 Conformity Assessment and IECRE 195
8.1 Module Conformity Assessment - PowerMark, IECQ, PVGAP, and IECEE 195
8.1.1 PV-1: “Criteria for a Model Quality System for Laboratories Engaged in Testing PV Modules” 196
8.1.2 PV-2: Model for a Third-Party Certification and Labeling Program for PV Modules 197
8.1.3 PV-3: Testing Requirements for a Certification and Labeling Program for PV Modules 197
8.1.4 PV-4: Operational Procedures Manual for the Certification Body of the PV Module Certification Program 197
8.1.5 PV-5: Application and Certification Procedures for the PV Module Certification Program 198
8.2 IECRE - Conformity Assessment for PV Systems 201
References 206
9 Predicting PV Module Service Life 209
9.1 Determining Acceleration Factors 210
9.1.1 Thermal Cycling 212
9.1.2 Discoloration of the Encapsulant 213
9.1.3 PET Hydrolysis 213
9.2 Impact of Design and Manufacturing on Failure or Degradation Rates for PV Modules 215
9.3 Impact of Location and Type of Mounting on Failure or Degradation Rates for PV Modules 216
9.4 Extended Stress Testing of PV Modules 221
9.5 Setting Up a True Service Life Prediction Program 226
References 227
10 What does the Future Hold for PV and a Brief Summary 229
10.1 Current Work on Updating Standards 229
10.1.1 Second Edition of IEC 61215 Series 229
10.1.2 Amendment 1 to Second Edition of IEC 61730-1 and IEC 61730-1 234
10.1.3 IEC TS 63126 - Guidelines for Qualifying PV Modules, Components and Materials for Operation at High Temperatures 234
10.2 Looking to the Future 237
10.2.1 Degradation Rates 237
10.2.2 Module Lifetime 238
10.3 Brief Summary 239
10.3.1 Personal Reflections 240
References 240
Index 243
