Testing and degradation assessment of mono-crystalline silicon PV modules after 30 years of operation in a desert climate

This study provides rare and valuable insights into the long-term reliability of monocrystalline silicon photovoltaic (PV) modules through a post-aging assessment conducted after 30 years of continuous outdoor operation in a desert environment in Algeria. Unlike most published studies, which focus on short- or medium-term exposure periods, this work investigates the performance and degradation characteristics of PV modules after three decades of field operation. A total of 64 aged PV modules were evaluated using standardized testing procedures in accordance with IEC 61215. The assessment included current–voltage (I–V) and power–voltage (P–V) measurements under standard test conditions, insulation resistance and wet leakage current tests, and systematic visual inspections. The results indicate an annual degradation rate ranging from 1% to 2%, with an average degradation rate of approximately 1.5% over the 30-year operating period. Despite prolonged exposure to harsh desert conditions, most of the tested modules maintained acceptable electrical performance and remained largely compliant with the relevant IEC safety requirements. Several degradation mechanisms were identified, including cell browning, busbar discoloration, cell cracking, and junction-box detachment. These degradation modes exhibited different effects on the electrical characteristics and long-term performance of the modules. The experimental findings provide valuable evidence of PV module behavior at an advanced aging stage and contribute to a better understanding of long-term degradation under harsh climatic conditions. The results can support more realistic lifetime assessments, reliability modeling, and maintenance planning for PV systems operating in desert and other challenging environments.