Thermal endurance studies were performed on the major polymeric components used in a Low concentration photovoltaic (LCPV) module using a thermal gravimetric analysis (TGA) method. Activation energy of the various polymers was obtained, and lifetimes were predicted based on the assumption of 5% weight loss for 30 years. Oven aging was used to verify the TGA thermal endurance prediction. Reasonable agreement between TGA prediction and oven baking results were reached, with the exception of ethylene-vinyl acetate (EVA) encapsulant that demonstrated a second-order reaction inconsistent with TGA assumptions. As a result, a more LCPV-relevant way to characterize the degradation of EVA was developed and demonstrated a linear relationship between PV device short-circuit current degradation and yellowness index. For the purpose of this EVA degradation analysis, a 20% reduction in PV device short circuit current was selected as the failure criteria.
"Thermal endurance study of polymers used in low concentration photovoltaic modules," Journal of Photonics for Energy 2(1), 021803 (4 October 2012). https://doi.org/10.1117/1.JPE.2.021803