Multi-stress durability testing to better predict outdoor performance of PV modules

Photovoltaic modules in the outdoor environment are subjected to a wide range of stresses which can operate simultaneously and sequentially and can vary based on climate and installation. These stresses can include temperature, temperature variation, localized heating, humidity, moisture (rain, snow, humidity, condensation), weathering, mechanical stress, abrasion and internal electric fields. These multiple stress make prediction of service lifetime challenging. Frequently resistance to an extended single stress is improperly used to assess durability. We have used sequential and simultaneous multistress exposure of materials and modules to better predict the synergistic effects of these stresses on module performance. We have also assessed the change in component materials properties to better understand performance changes. Finally, we compare these results to inspection of modules from the field to validate the test methods proposed.