Fifteen Years Under the Sun: Real-Field Degradation Analysis of Veteran PV Modules

This study presents a 15-year performance analysis of photovoltaic (PV) modules installed at CEA’s outdoor test site in Cadarache, southern France. Three PV technologies – polycrystalline silicon (p-Si), amorphous silicon (a-Si), and monocrystalline silicon (m-Si) – have been continuously monitored under real-field conditions to assess their long-term degradation rates and aging mechanisms. The p-Si modules exhibited the highest degradation rate, averaging 2% per year, significantly exceeding the manufacturer’s warranty expectations of 0.8% per year. Laboratory flash tests confirmed power losses ranging between -33% and -70% over 15 years. Infrared (IR) imaging identified a single hot spot, but degradation appeared uniformly distributed across all modules. Electroluminescence (EL) analysis revealed extensive microcracks and inactive cell regions, while visual inspections highlighted discoloration, light corrosion, and early signs of delamination. Despite these findings, no critical failures were detected in bypass diodes or electrical connectors. The study underscores the necessity of long-term real-field monitoring to refine predictive models for PV degradation and enhance module durability. Further detailed material analysis is ongoing to confirm intrinsic aging mechanisms and provide deeper insights into PV module reliability over time.