Predicting Warranty Risk of PV Modules

Photovoltaic devices degrade during their lifetime, just like any other technology. Degradation rates, and thus the lifetime of products, are currently not well understood. This lack of understanding results in stakeholders being exposed to unquantified risks and subsequently insufficient securities being set aside. It is shown that one cannot rely on a singular degradation rate of module's datasheet when it comes to assessing potential failure rates or warranty risks. Aging rates will vary in the field due to normal production variability. The existing approach that accepts a module type as reliable when a single certification test is passed cannot explain failures seen in the field nor provide any quantitative prediction. To address this problem, a methodology is developed that, in principle, predicts the likelihood of warranty claims in different operating environments. The method generates probability distributions of module performance for 25 years with typical degradation patterns seen for different degradation modes. The risk of failure is calculated from these distributions according to warranty conditions typical in the industry. The results show that over a quarter of the modules may be at risk of warranty failure at the end of warranty period. Furthermore, when the calculation is made considering that the degradation is exponential rather than linear, there is a risk of observing roughly five times more warranty cases five years after installation. Unlike current practices, this probabilistic warranty risk calculation approach can provide quantitative results, and help stakeholders better assess likely performance reduction of photovoltaic (PV) assets.