On the importance of ground-mounted reference systems for evaluating module degradation in emerging photovoltaic applications

Emerging photovoltaic (PV) applications, such as floating PV (FPV), subject modules to non-conventional operating conditions, complicating reliable degradation assessment and highlighting the need for appropriate ground-mounted reference systems. This study investigates the degradation of monofacial glass-backsheet and bifacial glass-glass monocrystalline silicon PERC modules under three conditions over 18 months: installed in an FPV system, installed in a ground-mounted PV (GPV) reference system, and stored as unexposed control samples. For the specific module type analyzed, the FPV-installed bifacial modules showed higher degradation than the FPV-installed monofacial modules. However, the GPV bifacial reference module showed degradation comparable to the bifacial FPV modules, whereas the GPV monofacial reference module showed lower degradation than the monofacial FPV modules. These findings indicate that FPV environment may accelerate degradation in monofacial modules while having limited additional impact on bifacial modules. Additionally, these results indicate that GPV reference modules are valuable for interpreting degradation trends and avoiding misleading conclusions in emerging PV applications.