Durability and Reliability of Polymers and Other Materials in Photovoltaic Modules (Plastics Design Library)

Description

Durability and Reliability of Polymers and Other Materials in Photovoltaic Modules describes the durability and reliability behavior of polymers used in Si-photovoltaic modules and systems, particularly in terms of physical aging and degradation process/mechanisms, characterization methods, accelerated exposure chamber and testing, module level testing, and service life prediction. The book compares polymeric materials to traditional materials used in solar applications, explaining the degradation pathways of the different elements of a photovoltaic module, including encapsulant, front sheet, back sheet, wires and connectors, adhesives, sealants, and more. In addition, users will find sections on the tests needed for the evaluation of polymer degradation and aging, as well as accelerated tests to aid in materials selection. As demand for photovoltaics continues to grow globally, with polymer photovoltaics offering significantly lower production costs compared to earlier approaches, this book will serve as a welcome resource on new avenues. Provides comprehensive coverage of photovoltaic polymers, from fundamental degradation mechanisms, to specific case studies of durability and materials failure Offers practical, actionable information in relation to service life prediction of photovoltaic modules and accelerated testing for materials selection Includes up-to-date information and interpretation of safety regulations and testing of photovoltaic modules and materials 0 Front-Mat_2019_Durability-and-Reliability-of-Polymers-and-Other-Materials-in DURABILITY AND RELIABILITY OF POLYMERS AND OTHER MATERIALS IN PHOTOVOLTAIC MODULES Series-Pa_2019_Durability-and-Reliability-of-Polymers-and-Other-Materials-in Series Page Copyrig_2019_Durability-and-Reliability-of-Polymers-and-Other-Materials-in-P Copyright Contribut_2019_Durability-and-Reliability-of-Polymers-and-Other-Materials-in Contributors 1 1. Overview: Power Degradation and Failure of PV Systems Chapter Points 1.1 Introduction 1.2 Photovoltaic Technology Development, Insertion, and Growth 1.3 PV Technology Development Campaigns and Initiatives 1.3.1 The JPL Flat-Plate Solar Array Project: 1975–1985 1.3.2 Carrisa Plains PV Power Plant: 1984–1991 1.3.3 The Photovoltaics for Utility Scale Applications (PVUSA) Project: 1986–1996 1.3.4 International Energy Agency (IEA): 1974–Present and Photovoltaic Power Systems Programme (PVPS): 1993–Present 1.3.5 21st Century PV Module Cost Reduction 1.4 PV Module Degradation 1.5 Moving Towards Terawatt PV Energy Acknowledgments References 2 2. Overview: Durability and Reliability of Common PV Module and Polymers/Materials 2.1 Background 2.2 Fundamentals for Durability and Reliability of PV Materials 2.2.1 Basic Structure and Materials for a PV Module 2.2.2 Functional Requirements of PV Module Materials 2.2.2.1 Superstrate (Front Sheet) 2.2.2.2 Encapsulants 2.2.2.3 Substrate (Backsheet) 2.2.3 Reliability Versus Durability 2.2.4 Theoretical Background for the Durability and Reliability Study 2.2.4.1 Solar Irradiance 2.2.4.2 Thermal Process 2.2.4.3 UV Crosslinking and Degradation Reaction 2.2.4.4 Physical Aging Process 2.2.4.5 Moisture Ingress Process 2.2.4.6 Polymers/Materials Flammability 2.2.5 Experimental Setup for the Durability and Reliability Study 2.2.5.1 Accelerated Testing Conditions 2.3 Observed Issues for Durability/Reliability of PV Materials on the Field 2.3.1 Major Types of Field Failures for PV Components 2.3.1.1 Corrosion 2.3.1.2 Solder Bond Failures 2.3.1.3 Cell or Interconnect Break 2.3.1.4 Encapsulant Discoloration 2.3.1.5 Junction Box Failures 2.3.1.6 Delamination 2.3.1.7 Hot Spots 2.3.1.8 Mechanical Damage/Glass Breakage 2.3.1.9 Defective Bypass Diodes 2.3.1.10 Arcing 2.3.1.11 Inverter 2.3.1.12 PV Connector 2.3.2 Polymer Materials Related Problems 2.3.2.1 EVA Discoloration 2.3.2.2 Creep 2.3.2.3 Embrittlement 2.3.2.4 Interfacial Adhesion 2.3.2.5 Thermal Expansion 2.3.2.6 Sealant Degradation 2.4 PV Materials Performance and Service Life Prediction: Challenges and Future Perspective 2.4.1 Development of Improved or New Materials 2.4.2 Qualification Test Methods 2.4.3 Correlation Between Outdoor Performance and Laboratory Accelerated Testing 2.4.4 Correlation Between the Degradation of PV Materials and Module Failure Modes 2.4.5 PV Service Life Prediction Appendix I Acknowledgments References Further Reading 3 3. Degradation Science and Pathways in PV Systems 3.1 Introduction 3.2 Polymer-Related Failures in PV Modules 3.2.1 Delamination and Mechanical Failures 3.2.2 Discoloration 3.2.3 Potential-Induced Degradation 3.2.4 Discussion 3.3 The Drawbacks of Standardized Testing 3.4 The Lifetime and Degradation Science Approach 3.4.1 Statistical Data Analytics for Lifetime and Degradation Science 3.4.1.1 netSEM Modeling Approach 3.4.1.2 Fixed, Random, and Mixed Effects Regression Modeling Approach 3.4.1.3 Multivariate Multiple Regression Modeling Approach 3.4.1.4 Parallel Factor Analysis Modeling Approach 3.4.2 L&DS Case Studies 3.4.2.1 PV Degradation Pathway Model under Damp Heat Exposure 3.4.2.2 Mini-Module PV Degradation Pathway Model under Damp Heat Exposure 3.4.2.3 netSEM Modeling of PET Degradation 3.4.3 Fixed and Mixed Effects Regression Modeling of PET Degradation 3.4.4 Multivariate Multiple Regression Modeling of PET Degradation 3.4.5 Parallel Factor Analysis of Fluorescence Spectra for PET Degradation 3.5 Conclusions Acknowledgments References 4 4. Degradation Processes in Photovoltaic Cells Chapter Points 4.1 Introduction to the Physics of Photovoltaic Devices 4.1.1 Semiconductor Growth and Doping 4.1.2 pn-Junctions and Photovoltaics 4.2 Characterization Techniques 4.2.1 Current versus Voltage Characteristics 4.2.2 Imaging and Spectral Techniques 4.3 Potential-Induced Degradation 4.3.1 Description of Phenomena 4.3.2 Mechanistic Investigations 4.3.3 Possible Mitigation Schemes 4.4 Light-Induced Degradation 4.4.1 Description of Phenomena 4.4.2 Mechanistic Investigations 4.4.3 Possible Mitigation Schemes 4.5 Solar Cell Cracking 4.5.1 Description of Phenomena 4.5.2 Mechanistic Investigations 4.5.3 Possible Mitigation Schemes 4.6 Cell Metalization Corrosion 4.6.1 Description of Phenomena 4.6.2 Mechanistic Investigations 4.6.3 Possible Mitigation Schemes 4.7 Conclusions References 5 5. Degradation and Failure Mechanisms of PV Module Interconnects 5.1 Introduction to PV Modules Interconnection, Degradation, and Failures 5.2 Front-Side Silver Grid Corrosion 5.2.1 Mechanisms 5.2.2 Characterization 5.3 Thermo-Putative Degradation and Mechanical Failure of Solder Joints 5.3.1 Mechanisms 5.3.2 Characterization 5.4 Ribbon Fatigue 5.4.1 Mechanisms 5.4.2 Characterization 5.5 Electrically Conductive Adhesives in Novel Cell Interconnection Strategies 5.5.1 Wrap-Through Cells and Their Interconnection 5.5.2 Shingled Cells and Subcells Interconnected With ECAs 5.5.3 Performance of PV Modules Utilizing ECAs 5.5.4 Qualification and Reliability of ECA Materials and PV Modules 5.6 Conclusions Acknowledgments References 6 7 7. Degradation Processes and Mechanisms of Backsheets 7.1 Backsheet Construction and Materials 7.2 Backsheets in Field Modules 7.2.1 Observed Field Degradation 7.2.2 Differences in Degradation by Backsheet Type 7.2.3 Differences in Degradation by Climate 7.2.4 Differences in Degradation by Mounting Configuration 7.3 Laboratory Stress Exposures 7.3.1 Environmental Stressors of the Backsheet 7.3.2 Standardized Weathering Procedures 7.3.3 The Effect of Different Weathering Stresses 7.3.3.1 Effect of Light Intensity and Wavelength on Degradation 7.3.3.2 Effect of Temperature on Degradation 7.3.3.3 Effect of Water on Degradation 7.3.3.4 Effect of Other Stressors on Degradation 7.3.4 Sequential/Combined Testing and Other New Tests 7.4 Conclusions Acknowledgments References 8 8. Crystalline Silicon PV Module Field Failures 8.1 Introduction 8.2 Observed Field PV Module Failures: Visual 8.2.1 Field Failures Related to Glass 8.2.2 Field Failures Related to Encapsulants 8.2.2.1 Encapsulant Yellowing/Browning 8.2.2.2 Delamination of Encapsulant/PV Cells 8.2.2.3 Delamination Between Encapsulant and Glass 8.2.3 Field Failures Related to PV Cells 8.2.3.1 PV Cell Silver Finger Oxidation 8.2.3.2 PV Cell ARC Coating Degradation 8.2.3.3 PV Cell Cracks and Snail Trails 8.2.3.4 Cell Hotspots 8.2.3.5 Potential Induced Degradation (PID) 8.2.3.6 Light Induced Degradation (LID) 8.2.4 Field Failures Related to Cell-to-Cell Busbars and String-to-String Bussing Ribbons 8.2.5 Field Failures Related to Backsheet 8.2.5.1 Backsheet Cracks 8.2.5.2 Backsheet Yellowing/Browning 8.2.5.3 Backsheet Delamination and Bubble Formation 8.2.5.4 Backsheet Chalking Failures 8.2.5.5 Moisture Ingress from Backsheet 8.2.5.6 Backsheet Damage due to Lightning 8.2.5.7 Backsheet Physical Damage 8.2.6 Insulation Patch Failures 8.2.7 Field Failures Related to Sealant 8.2.8 Field Failures Related to Frame 8.2.9 Field Failures Related to Junction Box Sets 8.2.9.1 Failures Related to Electrical Connection Inside the Junction Box 8.2.9.2 Field Failures Related to JBox Base and Lid 8.2.9.3 Field Failures Related to Diode 8.2.9.4 Field Failures Related to Pottant 8.2.9.5 Field Failures Related to Cable 8.2.9.6 Field Failures Related to Connectors 8.2.9.7 Failures Due to Water Ingress Damage 8.3 Observed Field PV Module Failures: Power Degradation 8.3.1 Ranking of Failure Modes Affecting Power Degradation 8.3.2 Overall Annual Module Power Degradation Rate 8.3.3 Module Power Degradation Rate by Installation Years 8.3.4 Module Power Degradation Rate by Climate Zones References Further Reading 9 9. Degradation Processes and Mechanisms of PV Wires and Connectors 9.1 Introduction 9.2 PV Connectors 9.2.1 New Failure Modes—Withdrawal Force 9.2.2 Considerations for PV Connector Factory versus Field Assembly 9.3 PV Wire (Above Ground) 9.3.1 New Failure Modes—UV Robustness 9.3.2 New Failure Modes—Slip Force 9.3.3 New Failure Modes—Roundness of Cables (Filled vs. Unfilled) 9.3.4 New Failure Modes—Cable Subjected to Flexing 9.3.5 Approach for Determining Bend Radius—Various Competing Sources 9.4 PV Wire (Below Ground) 9.4.1 New Failure Modes—Termite Resistant Cables 9.5 Wire Splices and In-Line Fuse Holders 9.6 Combiner Box 9.7 Wire Management Devices 9.8 Conclusion Acknowledgment References 10 10. Degradation Processes and Mechanisms of PV System Adhesives/Sealants and Junction Boxes 10.1 Introduction 10.2 History 10.2.1 Cold Impact Toughness 10.2.2 Creep and Consolidation 10.2.3 Contact Corrosion 10.3 PV Connectors 10.3.1 Incomplete Connector Engagement and Fretting Corrosion 10.3.2 Field Crimping Issues 10.3.3 Rodent and Insect Damage 10.3.4 Ground Faults 10.4 Bypass Diodes 10.4.1 Diode Evaluation 10.4.2 Perceived Gaps and PVQAT TG4 10.4.2.1 Junction Temperature 10.4.2.2 Thermal Runaway 10.4.2.3 Other Qualification Tests 10.4.2.4 Electrostatic Discharge Susceptibility 10.5 Junction Box Adhesion 10.5.1 Adhesive Change 10.5.2 Adhesive Creep References 11 11. Accelerated Environmental Chambers and Testing of PV Modules 11.1 Introduction 11.2 The Basics of Temperature and Humidity Chambers 11.2.1 Air Circulation 11.2.2 Temperature Control 11.2.3 Heating and Cooling 11.2.4 Humidity Control 11.3 Methods of Adding Humidity 11.3.1 Steam Generation (Boiler) 11.3.2 Heated Water Bath 11.3.3 Atomizing Spray 11.3.4 Ultrasonic Nebulizers 11.4 Methods of Removing Humidity 11.5 Measuring Relative Humidity in Environmental Chambers 11.5.1 Psychrometric Wet Bulb/Dry Bulb Sensors 11.5.2 Electronic Sensors 11.5.3 Chilled Mirror Dewpoint Hygrometer 11.6 Temperature and RH Control: Putting It all Together 11.6.1 Transitions Between Test Conditions: Step Versus Linear 11.6.2 Characterizing Environmental Chambers: Uniformity, Fluctuation (Stability), and Heating and Cooling Rates 11.7 Salt Mist and Corrosion Chambers 11.8 Weathering Chambers 11.8.1 Fluorescent UV Weathering Chambers 11.8.2 Xenon Arc Chambers 11.8.3 Metal Halide Light Sources 11.9 Climatic Tests in the PV Module Qualification Standards 11.10 Conclusions References Further Reading 12 12. Outdoor Field Testing: Environmental and System Stress Factors 12.1 Introduction to Outdoor Exposure of Photovoltaic Modules 12.1.1 Importance of Outdoor Exposure 12.1.2 Environmental Stress Factors 12.1.3 System Specific Stress Factors 12.1.4 Impact of Local Climate 12.2 Outdoor Testing 12.2.1 Equipment and Infrastructure 12.2.2 Test Methods and Analysis Techniques 12.2.2.1 Time-Series Data 12.2.2.2 Data Processing and Analysis 12.2.2.3 Complementary Characterization Techniques 12.2.2.4 Best Practices 12.3 Field Experience 12.3.1 Degradation Rate Analysis 12.4 Conclusion References 13 13. Service Life Prediction of PV Materials 13.1 Introduction 13.1.1 What Is Needed in the Industry? 13.1.2 Current Situation 13.1.3 How Did We Get to Here? 13.1.3.1 Durability Versus Reliability 13.1.3.2 Challenges of PV Module Durability Assessment 13.1.3.3 Polymeric Materials in Modules 13.1.3.4 Some Limitations of Accelerated Testing 13.1.4 Designing Accelerated Durability Tests 13.2 Predicting Functional Service Life 13.2.1 Step 1. Identify Degradation Modes and Pathways 13.2.2 Step 2. Quantitatively Define Failure (End of Functional Life) 13.2.3 Step 3. Define the In-Service Environment 13.2.4 Step 4. Quantify Effects of Weathering Stresses (E, T, H2O, Other) on Degradation Using Accelerated Weathering 13.2.5 Weathering Stress—Light 13.2.6 Weathering Stress—Temperature 13.2.7 Reciprocity 13.2.8 Weathering Stress—Moisture 13.2.9 An Example for Combined Weathering Stresses 13.2.10 Step 5. Initiate Long Term In-Service and Accelerated Natural Weathering for Future Use in Validating the Degradation Pathw ... 13.2.11 Step 6. Test to Failure 13.2.12 Step 7. Model Time-To-Failure as a Function of Weathering Stress 13.2.13 Step 8. Calculate Service Life Estimate Using Climate Data 13.2.14 Step 9. Validate SLP Model 13.2.15 Practical Limitations of SLP Annex A Annex B Acknowledgments References Further Reading 14 15 Index A B C D E F G H I J K L M N O P R S T U V W X