First Results from a High Precision Indoor & Outdoor PV Module Monitoring Campaign

To aid the design and parameterization of risk models used in insurance solutions for the PV industry, we introduced an innovative combination of repeated laboratory measurements and ongoing test field monitoring. This approach aims at the relationship between the real life experience and the STC based performance warranties. Each four samples of ten different module brands and types have been exposed for five years now. In this contribution, we compare the results of indoor module characterization to module parameters derived from outdoor operation, where IV curves are acquired in regular intervals. Dependent on the time scale, this comparison needs different approaches. When looking at the major influences on a PV module’s long term yield, a clear ranking is visible after 5 years of exposition. Deviations from rated values as given in the data sheet have the biggest influence on long-term yield, followed by initial degradation. Differences in cell and module technology are next in the ranking: low light behaviour, angular response and spectral response may help some products to perform better than others. Finally, long term degradation may cause different life time yields, as this (typically small) effect will increase differences in module characteristics with time. In this experiment, degradation rates between 0% and 1% per year have been deduced.