Photovoltaic Module Reliability

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.

Auteur

JOHN H. WOHLGEMUTH, PHD, is the Executive Director of PowerMark Corporation, VA, USA, and serves as the Technical Advisor to IEC Technical Committee 82 on Photovoltaics. Dr. Wohlgemuth has worked in PV for more than 40 years at Solarex, BP Solar and NREL. His PV experience includes cell processing and modeling, Si casting, module materials and reliability, and PV performance and standards. Dr. Wohlgemuth has been an active member of working group 2 (WG2), the module working group within IEC TC-82 since 1986.

Contenu
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 ...