Detailed Analysis of Degradation Rates of Operating PV Assets in Tropical Climate Conditions

This study presents an evaluation of photovoltaic system performance loss rates in tropical climates. We analysed the current dataset of 35 sites totalling 22.3 MWp installations across seven countries, spanning residential, commercial, and industrial applications. Data collection periods ranged from two to 11.7 years. Meteorological and power data were recorded at one-minute to 15 minutes intervals, enabling both sensor-based performance calculations and modelled clearsky irradiation analysis. The study includes different solar cell technologies including multi-crystalline silicon, mono-crystalline silicon, PERC and n-type mono-crystalline silicon and thin-film types. The database was further classified by tropical climate zones, module types (monofacial vs. bifacial), installation types (rooftop vs. ground-mounted), and module configurations (full cell vs. half-cell). The environmental stressors on-site are also presented to understand the factors driving the performance loss rate differences. The analysis identified mean and median performance change across systems of -1.41 %/year and -1.10 %/year, respectively, with degradation accelerating over time. This is higher than typically assumed in PV system design and financial modelling (often using 0.7-1.0%/year for the tropics). The analysis reveals accelerating performance losses with system age, indicating that studies of newer systems may underestimate long-term degradation. This work serves as a foundation for expanding the current database and developing suitable strategies for optimizing the long-term performance and reliability of PV systems in the challenging environmental conditions of the tropics.