Degradation Analysis of 38-Year-Old PV Modules Under the Weather Conditions of Sana'a-Yemen

In this article, a degradation analysis of seventeen 38-year-old PV modules is conducted to estimate the degradation rates of P_Peak, I_SC, V_OC, and fill factor, and identify the degradation modes that affected these modules. The modules under investigation were degraded under two different conditions: 16 modules were operated in the field, for 38 years, as a part of an off-grid photovoltaic system that was installed on the roof of the Faculty of Science, Sana'a University in Yemen, and one module was stored in a warehouse for the same period (exposure period<48 h). Visual inspection, I–V curve measurement, infrared thermal imaging, electroluminescence imaging, and insulation test have been carried out for each module. Upon comparing with reference values as given by the manufacturer, the median peak power degradation rate of the field-exposed modules over the outdoor exposure period was found to be 25.37%. While the peak power degradation rate of the warehoused module was found to be 14.30%. Encapsulant delamination from cells along grid fingers, corrosion of cell fingers, and hot spots were detected in the warehoused module. On the other hand, encapsulant discoloration, shunting defect, humidity corrosion, front delamination, cell fingers corrosion, interconnect ribbons corrosion, hot spots, and finger interruptions were the principal causes of performance degradation of the field-exposed modules. A description of the detected degradation modes includes a brief discussion of the limitations and benefits of the design of these modules.