Lotus effect and super-hydrophobic coatings for concentrated solar power systems (CSP)

CSP reflectors are a key component for CSP technology and are characterized by their specular reflectance (SR), the degree to which a mirror is capable of transferring directed radiation to a target receiver surface. The accumulation of dust on the surface of the reflectors can decrease the ability of their mirrors in reflecting the radiation to the receiver causing an important decrease in the power plant efficiency and an increase of electricity production cost. The aim of this paper is to identify polymeric super hydrophobic coating materials in order to create lotus effect on the CSP reflectors with self-cleaning, anti-icing and anti-contamination properties on the CSP reflectors, especially that the CSP power plants are usually installed in desert area, which brings out the issue of water resources. In this study, the lotus effect will be presented alongside with different hydrophobic coating techniques. Later, a comprehensive analysis of the applications, advantages and disadvantages of hydrophobic coating for CSP mirrors will be presented. A comparative study will be conducted to choose the most suitable Nano-coating material for CSP in terms of cost to efficiency ratio as well as the future work and research in this specific field. It is crucial to develop super-hydrophobic coatings that will keep the panels clean and retain reflectivity with minimal maintenance and water requirements. Super-hydrophobicity is defined by the geometry of a water droplet on a surface. The lotus effect occurs when the apparent water contact angle (CA) is higher than 150° and when the water contact angle hysteresis (CAH) is lower than 10° to create a self-cleaning effect.