Long-term Evaluation of the Effects of Physical Deterioration on Electrical Performances of Silicon Photovoltaic (PV) Modules

The long-term evaluation of a 3.12 kW grid-connected PV system installed approximately 20 years ago at KMUTT, Bangkok, Thailand. Annual testing was conducted on all modules following the IEC61215 standard, encompassing visual inspection and performance at standard test condition (STC) from 2012 to 2023. Visual inspection results revealed defects on both the superstrate and substrate materials of the modules. A closer examination of these defects is provided. STC measurements were performed by a class AAA solar simulator at the CES Solar Cells Testing Center (CSSC). The power degradation rate (R_d) at the end of the 20^th year was determined to be 2.4%/year, surpassing the average observed in previous research for crystalline silicon modules for 0.8%/year. Therefore, this study emphasizes the necessity of a comprehensive investigation into the physical deterioration of silicon PV modules. The decrease in electrical performance was closely related to the extent of physical deterioration. Corrosion areas were identified, with ribbon growth rates ranging from 10-17% over three years. Delamination areas were also identified, with PV cell growth rate explanations ranging from 8-30% over four years.