Scientists in Morocco have conceived an experimental–numerical model to quantify how fly ash soiling affects photovoltaic (PV) modules, capturing both optical losses and thermal effects. Their findings show that while dust layers can reduce panel temperature, fly ash significantly degrades efficiency in a non-linear way, highlighting the need for predictive models for real-world solar performance.
The experimental setting
Image: Science Engineer Laboratory for Energy (LabSIPE), Next Energy, CC BY 4.0
A research team from Morocco has quantified the impact of fly ash accumulation on PV modules using a combined experimental and numerical approach. In coupling experimental validation with numerical modeling, the group could provide a framework for assessing and predicting soiling-induced thermal and optical effects.
“Our paper synthesizes experimental validation, realistic simulation, and coupled optothermal-electrical modeling, while demonstrating practical operational applicability,” corresponding author Kamal Fadil told pv magazine. “This work not only advances our scientific understanding of the fouling mechanisms of photovoltaic cells but also contributes to the development of sustainable, intelligent, and energy-efficient maintenance strategies for future solar energy systems.”
Fadil highlighted that their model has specifically characterized fly ash, a very fine particulate dust produced mainly by combustion processes, such as road traffic emissions and industrial discharges. “Our framework undertakes a comprehensive evaluation of the influence of diverse fouling types, considering their optical attenuation and specific thermal effects on photovoltaic performance. This facilitates a more representative interpretation of real-world operating conditions encountered in urban, industrial, and highway environments, among others,” he added.
The study started with a test bench containing two identical monocrystalline silicon PV panels of 0.54 m², with a tilt angle of 35° and an azimuth angle of 0°. Coal fly ash was applied to one of the panels in three experiments, each with a different particle size: up to 20 μm, 20–45 μm, and 45–63 μm. Both panels were exposed to sunlight outdoors during sunny periods, from 09:00–17:00.
Image: Science Engineer Laboratory for Energy (LabSIPE), Next Energy, CC BY 4.0
At the same time, the researchers built a two-dimensional thermal model of the PV modules. It included solar radiation on the front glass, natural convection on the front and rear surfaces, and heat conduction through the internal layers caused by photon thermalization. Predicted temperatures were compared with thermocouple measurements from the test bench and showed excellent agreement, with a Pearson correlation of 0.997, a coefficient of determination (R²) of 0.994, a root mean square error (RMSE) of 0.79 C, and a mean absolute error (MAE) of 0.62 C.
“The numerical framework is strengthened by the integration of experimentally measured environmental and operational parameters, including climatic conditions, geometric configuration, thermophysical properties of photovoltaic modules, optical characteristics of the deposited particles, and varying fouling densities,” said Fadil. “This enhancement of the model’s physical representativeness leads to an improvement in its applicability to photovoltaic engineering tasks, including energy yield prediction, degradation assessment, loss estimation, and the sizing of mini-photovoltaic power plants operating in polluted environments and future installation areas.”
According to the experimental results, the clean panel reached higher temperatures of 70–72 C, while the fly-ash panel stabilized at 60–62 C due to the insulating effect of the deposited particles. However, despite being cooler, the dirty panel performed worse: its efficiency started at 14% compared to 16.5% for the clean panel at 25 C, and both dropped to about 8% at high operating temperatures.
“A salient finding of this research was the strong thermal amplification effect associated with fly ash accumulation. Whilst the prevailing wisdom attributes losses in electrical efficiency solely to optical losses, the results demonstrated that thermal accumulation can significantly intensify the degradation of this efficiency,” concluded the researcher. “Another salient observation reported in this study is that the relationship between fouling density and photovoltaic losses is not strictly linear under certain operating conditions, particularly when thermal effects become predominant.”
The research work was presented in “Quantitative assessment of fly ash–induced soiling in photovoltaics: Experimental validation and predictive modeling,” published in Next Energy. Scientists from Morocco’s Science Engineer Laboratory for Energy (LabSIPE), National School of Applied Sciences, and Chouaib Doukkali University have contributed to the research.
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