Optical Transmission Losses of a TiO2-based Anti-soiling Coating for Use in Outdoor Photovoltaic Applications

Soiling can be a major challenge for photovoltaic (PV) installations, depending on their location, as it reduces transmission and can lead to significant losses. Anti-soiling coatings have been demonstrated to reduce soiling losses and thereby increase PV power production. This article investigates the applicability of a titanium-dioxide-based anti-soiling coating developed by Photocat under the name “ShineOn” for use with PV installations. The main parameter examined is the optical transmission losses, as this directly translates to performance losses during non-soiled operations. Measurements of transmittance are carried out using both indoor laboratory setups as well as outdoor PV installations, including measurements of the short-circuit current (Isc), incidence angle modifier (IAM) and spectral transmittance. Investigated samples include both full-sized modules and custom-made mini-modules containing a single solar cell. Both indoor and outdoor measurements show minor transmission losses in the range of 0.3 to 0.6 % and negligible effects on the IAM. Additionally, observations indicate that samples should be coated after lamination, as losses for samples coated before lamination are slightly higher. As the transmission losses due to the ShineOn coating are small and no additional angular- dependent losses were observed, the coating is deemed not to be detrimental for PV applications. Proper assessment of the usefulness requires investigations of the anti-soiling properties, for example, through test installations in regions with high soiling rates.