Experimental study of soiling type and environmental effects on the performance of solar photovoltaic panels

This study experimentally quantifies the soiling induced performance degradation of monocrystalline silicon photovoltaic panels under outdoor field conditions in Dhaka, Bangladesh, a tropical urban environment with diverse contaminant types underrepresented in the global soiling literature. A paired panel design was operated over 141 days (December 2024 to April 2025) and supplemented by a rural contaminant assessment in May 2025. Five soiling agents were evaluated sequentially: natural dust, construction dust, biological debris, wood powder, and domestic bird feathers. Domestic bird feathers imposed the greatest average performance loss of 40.70%, attributable to macroscopic optical obstruction and hygroscopic enhancement of feather keratin optical density. Wood powder caused a 29.00% average loss through dense, moisture absorbing layer formation. Natural dust, construction dust, and biological debris produced comparable losses of 15.80%, 16.20%, and 16.60%, respectively, consistent with a semitransparent particulate attenuation regime. Performance degradation was most pronounced in the 29°C to 35°C temperature range and at 41–70% relative humidity, escalating progressively from December through April. Combined measurement uncertainty was ± 2.1% (coverage factor k = 2). These findings demonstrate that organic and fibrous contaminants impose disproportionately severe and practically significant performance penalties relative to mineral particulates, providing an empirical basis for differentiated, condition responsive maintenance strategies in tropical South Asian photovoltaic deployments.