10 year performance and degradation analysis of different photovoltaic panels in the Istanbul Türkiye environment

This study investigated the long-term degradation rates and mechanisms of thin-film, monocrystalline and polycrystalline photovoltaic (PV) panels in the temperate climate of Istanbul, located at the crossroads of Europe and Asia. Over a monitoring period of more than a decade, degradation phenomena such as EVA encapsulation degradation, moisture ingress, snail marks, and hot spots were identified through visual and imaging analyses. Characterization tests showed that polycrystalline panels exhibited a constant degradation rate of 2 % per year, while monocrystalline and thin-film panels showed rapid degradation in the first five years (4.4 % and 4.26 %, respectively) and stabilized at 2 % thereafter. After 5 and 10 years, the electrical power loss was 21.3 % and 28.5 % for thin-film panels, 21 % and 30 % for monocrystalline panels, and 9 % and 21.25 % for polycrystalline panels. Electroluminescence (EL) and infrared (IR) imaging identified defects such as inactive cells, manufacturing defects, broken and cracked cells, and hot spots, highlighting their impact on efficiency. These findings highlight the need for climate-resilient PV panel designs and advanced manufacturing techniques to ensure long-term performance.