Survey of Material Degradation in Globally Fielded PV Modules

Material durability is a critical factor in designing systems to sustain decades of continuous operation in terrestrial environments. As service lifetime expectations of PV modules continue to grow, it is important that we understand the implications of durability on module performance and safety so that manufacturers can make informed decisions on materials selection. Of particular interest are polymeric components— encapsulants and backsheets—that must withstand decades of exposure to sunlight and other terrestrial forces, often in aggressive climates. While investigations of polymer degradation due to individual stressors—such as irradiance, temperature, humidity, and external forces—have been widely investigated in the literature, the interdependency of these stressors as encountered in the field is not well characterized. To better understand the collective impact of environmental stressors on module durability, DuPont has developed an unprecedented global program for evaluating and assessing degradation of module components and materials in the field. Our database includes over 355 installations that account for nearly 2 GW of power, with module service lives ranging from years to decades. We present here results and analysis of our field survey through 2019, in which correlations between operational lifetime and degradation are established and recurring instances of severe backsheet degradation are highlighted. Our findings illustrate the temporal nature of backsheet degradation and highlight the importance of materials selection in mitigating financial risk.