Mechanisms of dust agglomeration and self-cleaning on a superhydrophobic surface during condensation

Dust accumulation on a photovoltaic (PV) surface hinders sunlight transmission, reduces photoelectric efficiency, and poses security risks. Although condensation affects dust agglomeration, self-cleaning superhydrophobic surfaces can effectively remove dust accumulated on a PV surface. However, the mechanism of agglomeration and adhesion of dust particles on the superhydrophobic surface remains unclear. The mechanism of particles carried by jumping droplets on a superhydrophobic surface has not been well understood. Therefore, we performed dust particle agglomeration and self-cleaning experiments on a superhydrophobic surface during condensation. The agglomeration process of dust particles on the superhydrophobic surface was observed using a three-dimensional microscope. We analyzed the causes that facilitate dust removal by droplets jumping away from the superhydrophobic surface. The particle agglomeration process primarily entailed four processes: coalescence of two droplets, coalescence of partially wetted particles and droplets, agglomeration of partially wetted particles, and coalescence of droplets wrapped with multiparticles. We analyzed the mechanisms of condensation-induced droplet jumping and particle agglomeration on the superhydrophobic surface. Droplets jumping away from a superhydrophobic surface can induce the formation of stacked spherical agglomerates. These agglomerates exhibited reduced contact areas and adhesion forces between the agglomerates and superhydrophobic surfaces, which facilitated the removal of dust particles from the surface. The smaller the particles, the better the dust cleaning effectiveness of the droplet jumping phenomenon. In addition, outdoor self-cleaning and wind cleaning simulation experiments were performed to confirm the self-cleaning effect of superhydrophobic surfaces. The obtained results provide a theoretical guidance for the optimal design of self-cleaning surfaces.