Comparative investigation and analysis of delaminated and discolored encapsulant degradation in crystalline silicon photovoltaic modules

Abstract

Delamination and discoloration are the most commonly observed encapsulant degradations in crystalline silicon photovoltaic (PV) modules under field conditions. In this work, a comparative analysis of brown discoloration and front side grey appearing delamination of ethylene vinyl acetate (EVA) has been presented, to understand their basic effects and modes of degradation. For this purpose, both type of degraded EVA samples from field-aged PV modules have been investigated, for finding the difference in their spectral response, chemical constituents, structural change, and impact on module electrical performance. These investigations have been performed using quantum efficiency (QE) measurement, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). In addition, electrical analysis was performed using PSpice circuit simulator. The distinct effect of discolored and delaminated EVA degradations, on incident radiations was identified mainly in absorption and reflection loss respectively, under different wavelengths. Also, the impact of these degradations on module performance, due to mismatch loss within the module has been presented. The chemical constituent investigation, supported presence of delamination in grey degraded sample due to absence of interfacial adhesive agent, in contrast to discolored sample. Findings from the structural investigation, corroborated a decrease in crystalline behaviour of both degradations. Furthermore, impressions from etched silicon cell were observed only in delaminated sample, which can be the reason of its grey appearance and more reflection. This work highlights the comparative effects and impact of dominant EVA degradations in terms of their characteristic aspects, which can be instrumental in improvement of EVA formulation.