SPLTRAK Abstract Submission
Extended Accelerated Stress Testing (EAST) of Glass/Glass, Glass/Backsheet and Glass/Transparent Backsheet PV Modules: Influence of EVA and POE Encapsulants
Akash Kumar1, Ashwini Pavgi 1, Peter Hacke2, Kaushik Roy Choudhury3, GovindaSamy TamizhMani1
1Photovoltaic Reliability Laboratory, Arizona State University, Mesa, AZ, United States
/2National Renewable Energy Laboratory, Golden, CO, United States
/3DuPont, Central Research and Development, Wilmington, DE, United States

Abstract— Glass/Glass (GG) photovoltaic modules are claimed to offer several advantages compared to the conventional glass/backsheet (GG) modules and the percentage of market share for GG modules has also steadily increased over the recent years. By having glass as both superstrate and substrate, the modules are reported to offer better mechanical support and humidity/temperature tolerance [1]. Considering an estimated market share of over 35% by 2030 [2], it becomes critical for the industry to understand the reliability of GG modules compared to glass/backsheet (GB) modules with common encapsulants such as EVA and POE. This paper presents the indoor extended accelerated stress testing (EAST) results of glass/glass (GG), glass/backsheet (GB) and glass/transparent backsheet (GT) modules having identical cells and two different encapsulant types, ethyl-vinyl-acetate (EVA) and polyolefin-elastomer (POE). Six 4-cell modules having the above-mentioned construction combinations were subjected to extended ultraviolet (UV; 600 kWh/m2), damp-heat (DH; 2000 hours) and thermal-cycling (TC; 600 cycles) tests. The post-stress UV fluorescent imaging, electroluminescent imaging, reflectance spectrophotometry and colorimetry results indicated that the major degradation modes in the new generation GG modules are grid finger degradation and encapsulant browning. The UVF images indicated the presence of ring browning in GB and edge browning in GG after UV 600 kWh/m2. An increase in Yellowness Index was observed in the non-cell area of all different constructions after UV 600 and DH 2000h. The YI and reflectance results indicated minor signs of encapsulant browning on the cell edge and cell center DH2000h, suspected to be due to moisture ingress. TC600 results indicated severe grid finger degradation in GG EVA modules thought to originate due to the rigidity in GG modules. The post-stress IV test results indicated, in general, that the GG/EVA modules tend to perform inferior to the GG/POE modules with EAST evaluation. 
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