Investigations into the Adhesion and Detachment of Dust Particles to Characterize the Reversibility of Photovoltaic Panel Soiling

Abstract

As the use of renewable energy is spreading, the degrading effects of pollutant accumulation on the surface of photovoltaic (PV) panels become more apparent, especially in arid climates. Dust deposition reduces light transmittance to the panel and decreases the energy output. Cleaning of PV modules can cost millions of dollars per year; therefore, it is important to study the reversibility of the soiling process. Mitigation strategies would not only increase energy production and revenues, but also the attractiveness of more PV installations due to lengthened optimal performance. Hence, soiling losses are widely monitored to understand the complex process driven by several factors, such as system design, soiling material, or environmental conditions. This work aims to fill the gap in knowledge on how the reversibility of solar panel fouling varies with the composition of dust in the atmosphere and panel surface features. The primary objectives of this study were to (1) characterize the attachment efficiency of dust particles at different locations; (2) determine whether particle composition influences particle-surface interactions through direct adhesion force measurements; (3) relate particle adhesion to particle detachment through centrifugation; (4) evaluate the feasibility of the centrifugal detachment technique to analyze PV panel coating performance and durability. The experimental methods were first tested using model pollutants that represented the major classes of soiling material, followed by dust samples obtained from the field. In addition to the laboratory studies, the impact of prolonged outdoor exposure was also tested to consider the complex mechanisms relevant to PV panel soiling. The comparison of predicted soiling loss based on a dust deposition model with collected soiled mass revealed that the attachment efficiency of dust varies seasonally and spatially, which could be influenced by changes in dust composition. This was confirmed by adhesion and detachment studies, as organic and carbon-based materials exhibited a significantly larger adhesion force to the glass surface than the rest of the samples. The centrifugal detachment technique could successfully measure the soiling rate on coated solar panels both with model pollutants and outdoor exposure. Coatings significantly differed in their ability to decrease particle accumulation on the surface, but all treatments lost at least 30% of their original hydrophobicity at the end of the 34-week exposure period. The results suggest that local dust composition influences solar panel soiling and should be considered for predictive models and maintenance needs. In addition, detachment studies could be used to establish a metric to quantitatively describe the efficiency of various PV panel surface treatments.