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 a 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 c-Si wafer types (multi-crystalline, mono-crystalline), different silicon solar cell technologies (p-type multi-crystalline silicon, mono-crystalline silicon, PERCand n-type mono-crystalline silicon), as well as thin-film types (largely CdTe). The database was further classified by climate zones (within the tropical classification), module types (mono-facial vs. bi-facial), installation types (rooftop vs. ground-mounted), and module configurations (full cell vs. half cell).. 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 shows that there is a trend towards accelerating performance losses with system age, indicating that studies of newer systems may underestimate long-term degradation. This work serves as a solid foundation for further studies into the root causes of the higher PLRs in tropical climates, which then would enable the development of suitable strategies for optimizing the long-term performance and reliability of PV systems in the challenging environmental conditions of the tropics.