Comparison of Changes in the Parameters of Five PV Module Types after one Year in the Swiss Jura Mountains

The Photovoltaic Benchmark System Mont-Soleil (PV-Bench) pilot project was launched on Mont-Soleil at 1274 meters above sea level in the Bernese Jura in May 2023. Five PV module types, each consisting of six pieces, TOPCon, Heterojunction bifacial, Heterojunction monofacial, PERC, and PERC BIPV were operated on microinverters for 16 months. Before and after outdoor exposure on Mont-Soleil, the module performance was measured under standard conditions, and module degradation was analysed. Additionally, the time-dependent performance of the modules during the outdoor exposure on Mont-Soleil was studied. For this purpose, the IV-curve of each module was measured once every minute, and values such as current, voltage, and Pmpp were read and analysed from the characteristic curve. Based on these Pmpp and temperature measurements, the time-dependent temperature-corrected performance ratio of the modules was determined under irradiance between 900 W/m² and 1000 W/m². This paper identifies differences between the performance ratios measured indoors and outdoors and explains them. Furthermore, it outlines the challenges of determining outdoor module degradation. These challenges include natural factors, such as varying weather conditions during comparison periods, and technical factors, such as the influence of data filtering on the results, different IV curve scanning speeds indoors and outdoors, which can affect results due to capacitive effects, or software updates that may have impacted data filtering during the measurement period. Additionally, the annual and winter energy yields of the various module types are calculated, which is a relevant metric in connection with the Swiss Alpine System incentives. Based on this, estimates are made for the winter energy yield in an average year and with optimized system orientation. Mont-Soleil is also assessed for its suitability as a PV benchmark location. To this end, the spatial homogeneity of the average irradiance on the installation is examined using reference cells.