Harvesting with self-cleaning features: examining the role of wetting state in dust removal

The optical properties of protective surfaces used for solar photovoltaic (PV) are crucial for efficient solar energy harvesting. These surfaces must have high transmittance and low absorption to achieve maximum performance. However, environmental factors such as temperature, humidity, and dust settlement can cause severe damage and lower system efficiency for solar thermal and solar PV systems. When the dust settles on protective covers, it scatters and diffuses incident solar radiation, negatively impacting solar receiver performance. Despite efforts to mitigate the effects of dust particles on protective covers and reflective surfaces, the cost-effective removal or self-cleaning of these surfaces remains challenging. Dust particles in humid air collect water vapour and produce mud on solid surfaces, creating a chemically active fluid layer through condensation. This layer can dissolve alkaline (K, Na) and alkaline earth metal (Ca) compounds, causing selective surfaces to lose optical transparency. Therefore, dust must be removed before chemically active layer development. Creating a hydrophobic state on a surface is one method for facilitating the removal of dust particles. Nano/micropillars can trap air and reduce surface dust particle interaction. Therefore, the wetting state of a surface plays a significant role in the self-cleaning application of surfaces, with droplet dynamics being the preferred method for dust particle removal. Experimental evaluations have been conducted on the optical properties of self-cleaning surfaces and the influence of dust on water droplets. Water droplets remove the accumulated dust from the hydrophobic surface; however, the primary mechanism for environmental dust cleaning is the fluid cloaking over the particles.