Evaluation of the Impacts of Various Cleaning Techniques on Photovoltaic Module Glass

The cleaning of PV-module glass to remove soiling and other contaminants can alter the surface physical and optical properties. To assess the impacts of mechanical cleaning, we examined the effects of several PV-cleaning processes used in Brazil PV installation. Specifically, we evaluated modules and module glass covers that were exposed to natural soiling during a 90-day period and cleaned twice daily. With this accelerated timeframe, a controlled artificial soiling method was used to mimic the local soiling conditions. The surface roughness, optical transmittance, and PV-panel short-circuit current (I
sc
) were measured at regular intervals during the cleaning processes. The cleaning techniques included water spraying, compressed air, brushes with various bristles used in the field (thick nylon, soft-thin nylon, silicone foam) with water, polyurethane sponge with water, and abrasive synthetic resin sponge with water, and rubber squeegee to remove the water. For this region in Minas Gerais, Brazil, (characterized by moderate soiling conditions during the dry season), the water-only and compressed-air techniques provided the best results, with minimal detected damage to the surfaces and changes in the measured I
sc
after the 90-day period of experiment. The methods using the synthetic brushes were the most harmful to the glasses. For situations of higher dirt adhesion (e.g., caking) or thicker soiling layers on the module glass, the methods with a nylon brush and polyurethane bushing were more effective.