Impact of different brush designs in robotic cleaning on the degradation of anti-soiling coatings

Cleaning solar PV panels' surface is a standard method for mitigating soiling-related losses. The cleaning process may result in the abrasion of any coatings on the surface of the glass. We have developed a cleaning cycle simulator to emulate the various stressors that influence abrasion during cleaning events in the field. Using this simulator, we investigated the effect of abrasion caused by two different types of brush designs (linear and rotary cleaning brushes) used in robotic cleaning on coated (with anti-soiling coatings) and not-coated solar glass samples. Coated samples (A, B, C and D) that went through linear abrasion cycles showed higher degradation than rotary abrasion. This is shown to be due to the higher weight applied by the linear brush on the surface of the sample compared to the rotary brush bristles. The not-coated sample shows an increase in contact angle and roughness after 3700 linear and rotary abrasion cycles. This is demonstrated by XPS analysis to be due to the deposition of nylon on the glass during cleaning. The brush bristles' tips show significant damage to its shape after linear and rotary abrasion. Bristle diameter of the linear brush bristle decreased significantly after 3700 cycles of linear abrasion. The hardness of the brush bristles' tips showed a significant decrease after undergoing 3700 abrasion cycles, with more severe damage in the case of linear abrasion. Brush designs may have to be accordingly modified to account for these observations.