From Optical Attenuation to Thermal Amplification: Multi-Physics Impacts of Environmental Soiling on Photovoltaic Module Performance

Abstract The accumulation of natural and anthropogenic deposits on photovoltaic (PV) panels causes performance losses that extend beyond simple optical attenuation. This study investigates the coupled optical, thermal, and electrical impacts of three representative soiling materials, fly ash, organic wood debris, and sand dust, on PV module performance under real outdoor conditions in El Haouizia (El Jadida, Morocco). We introduce a coupled thermo-electrical model validated against high-precision experimental measurements. The model demonstrates high predictive accuracy across all surface conditions, with root mean square errors (RMSE) consistently below 0.25 °C and coefficients of determination (R2) exceeding 0.997, confirming the model’s reliability under heterogeneous soiling conditions. Critically, our analysis reveals that soiling materials significantly alter the module's temperature coefficient of power (β). From a clean-state reference of -0.42 %/°C, β degrades to -0.48 %/°C with sand, -0.52 %/°C with organic debris, and most severely to -0.62 %/°C with fly ash deposition. This material-dependent sensitivity indicates that soiling-induced heating, driven by the particulates’ optical properties, can amplify power losses beyond what is predicted by shading alone. By quantifying the strong coupling between soiling composition, thermal stress, and electrical degradation, this work provides new, critical insights for accurate performance modelling. It highlights the need for material-specific strategies to mitigate soiling.