Optimizing Combined Accelerated Stress Testing for Solar Backsheet Qualification

The combination of multiple accelerated stress conditions is critical to understanding and predicting the performance of PV module materials and designs over the > 30 year expected lifetime of the product. Several research groups have investigated this topic using either a multi-stress sequential stress approach or simultaneous stress approach with some success in predicting field performance. This paper describes an accelerated test approach that combines elements of both methods guided by modelling of temperature and moisture concentration in the module structure that best matches the outdoor environment. The total duration of the exposure and the correlation to field performance are key considerations in the test protocol method development. The effectiveness of this approach is demonstrated in modules with backsheets with known outdoor durability issues.