Anti-soiling performance of high reflective superhydrophobic nanoparticle-textured mirror

The anti-soiling (AS) performance of solar mirrors coated with a highly transparent, superhydrophobic nanoparticle-textured coatings has been characterized. The AS coatings were created on the mirror surface by depositing nano-textured silica nanoparticle layers with ~250 nm thickness using a draw-down coating process, followed by fluorination of the nanoparticles in a molecular vapor deposition process. Highly uniform surface features on the AS-coated mirrors (20×30 cm2, no measurable loss in specular reflectance, and water contact angle >165○) provided outstanding AS performance. A 4× reduction in the rate of dust accumulation as determined by gravimetric measurement of the accumulated dust on coated versus uncoated mirrors was observed. Additional evidence of a significant reduction in soiling rate was determined during measurements of specular reflectance in an outdoor environment test. The adhesion force between a model sand particle and nano-textured coatings having in the range of hydrophobic to superhydrophobic was also studied. A dramatic decrease in adhesive force acting on the particle was observed with increasing surface hydrophobicity. The results align well with observed dust accumulation on the AS coated mirrors. The AS-coated mirror maintains high reflectivity by shedding dust and resisting dust accumulation, providing a potential benefit when applied to mirrors in the solar field of a concentrating solar power generating plant.