Long-term EVA degradation simulation: Climatic zones comparison and possible revision of accelerated tests

摘要

The increasing demand of photovoltaics installations, also in harsh climatic conditions, requires the accurate comprehension of module lifetime and durability. Accelerated environmental tests (damp heat, thermal cycling, and humidity freeze) are performed as pass/fail criteria to determine whether modules are suitable for sale, while do not accurate predict durability in all possible climates. Recently, we proposed a computational model to study the thermo-oxidative degradation of EVA encapsulant. This model was suitable to describe effects of temperature fluctuations on degradation, while neglecting dramatic changes of outdoor exposure in different climatic zones. To investigate the correlation between climatic zones and EVA degradation, we completed the existing degradation model by adding the UV exposure dependency. This model, for the first time, simulates EVA thermo-photo-oxidation in accelerated and environmental conditions. We compared results of simulated standard accelerated tests and outdoor exposure, observing a significant mismatch of results. The low prediction capability of standard tests pushed us to analyze modified accelerated tests, by adding an internal UV source. Modified test simulations show a better matching with outdoor long-term weathering. The modified setup will enable novel accelerated tests with predictive behavior of long-term EVA degradation and a more accurate PV module lifetime.