Correlational Study on the Impact of Harsh Environment Stress Factors on the Ageing Effects of Several Encapsulation Materials for PV Modules

The composition of encapsulation materials for photovoltaic (PV) modules was, is, and will be continuously optimized, partly due to longer life time targets, and partly for the necessity of compatibility with novel and future cell technologies. As a consequence, a considerable decrease of outdoor-related failures to this bill of material component and process was noticed in the last decades. Yet, particularly for PV modules installed in harsh environments, such as hot and humid or desert climates, the natural stress factors pose a significant challenge for these encapsulation materials (depending on location, one or a combination of factors such as: high UV irradiation doses, high relative humidity, high temperature, high temperature differences for day-night). Therefore, to understand the ageing mechanism of encapsulation formulations and the interaction with their interfaces under environmental stress, an accelerated stress sequence comprised of damp heat test (DHT), temperature cycling test (TCT) and UV irradiation ageing was defined. Furthermore, two pertinent features were selected to be monitored during ageing at this experiment for an uncomplicated and effective characterization using spectroscopic transmission and adhesion strength (to solar glass and to backsheet foil), which are affected by transmission changes, bond weakening and delamination effects.