Performance degradation assessment of silicon solar cells under field operation in Jimma zone, Ethiopia

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Abstract This study investigates the aging and performance degradation of crystalline silicon photovoltaic (PV) modules installed in Jimma, Ethiopia, a region characterized by high solar irradiance (5–6 kWh m − 2 d − 1 ), elevated temperatures, and humidity levels up to 85%. Polycrystalline and monocrystalline PV modules, aged 4 to 28 years, were evaluated using a current–voltage measurements normalized to standard test conditions. All modules exhibited significant encapsulant discoloration, cell cracks, and delamination, along with browning and yellowing of ethylene vinyl acetate. The annual degradation rates of power output, short-circuit current, and open-circuit voltage were approximately 1.53%, 0.88%, and 0.67%,with an associated uncertainty of ± 0.32 % for polycrystalline modules, and 1.58%, 1.196%, and 0.616%,with an associated uncertainty of ± 0.0 .26 % for monocrystalline modules, respectively, which exceeds typical manufacturer warranty limits of 0.5% to 0.7% per year. Performance degradation was further worsened by an increase in series resistance, resulting from metalization corrosion, solder joint fatigue, and microcracks, which reduced the fill factor and maximum power output. Concurrently, a decrease in shunt resistance, associated with encapsulant browning, moisture ingress, and delamination, increased leakage currents and reduced carrier collection efficiency. Consequently, power loss was dominated by declines in short-circuit current, linking optical, physical, and resistive degradation to electrical performance deterioration. The fast degradation observed in Jimma highlights the strong influence of high temperature and humidity on PV module longevity, emphasizing the need for climate-specific energy yield predictions and the deployment of PV technologies with enhanced durability in tropical environments.

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