Researchers at Israel's Ben Gurion University of the Negev claim to have developed an efficient self-cleaning solution for dust removal from solar panels.
The solution, presented in the study Self-Cleaning Mechanism: Why Nanotexture and Hydrophobicity Matter, published by ACS Publications, consists of an hydrophobic coating that repels water, which is said to reduce the friction between water droplets and the surface, thus allowing water to slide clean particles from surfaces.
Inspired by nature
The scientists said they conceived their invention by observing how lotus leaves are not affected by dust and other pathogen due to their nanotextured surface – which is also a water-repellent hydrophobic coating – with water rolling down the leaves and removing contamination.
By wet-chemically etching the surface, the research team created nanowires on the solar modules, while also adding a hydrophobic coating. They prepared four silicon-based samples relevant to solar panels: (1) smooth hydrophillic (2) nanotextured hydrophilic surfaces and (3) smooth hydrophobic (4) nanotextured hydrophobic surfaces. Hydrophillic materials are those with a special affinity for water, while hydrophobic are those which naturally repel water, causing droplets to form.
Stronger particle removal
“Particle removal increased from 41% on hydrophilic smooth Si wafers to 98% on superhydrophobic Si-based nanotextured surfaces,” the report notes. These results were achieved by the researchers measuring the adhesion of a micron-sized particle to the flat and nanotextured substrate using an atomic force microscope. The research team also claims that the adhesion in water on the panel’s surface was reduced by a factor of 30.
The researchers suggest that the stronger particle removal came not from low friction between the droplets and the superhydrophobic surfaces, but instead due to the increase in the forces that can detach particles from the modules. “The experimental methods we used and the criterion for particle removal we derived can be implemented to engineer self-cleaning surfaces exhibiting different chemistries and/or textures,” a scientist further explained.
The scientists also said, however, that these forces and the effect of nanotextures on these forces were not fully understood in the experiment.
In recent years, anti-soiling coatings have gained ground commercially, as project developers have a stronger understanding of how they can boost a project's power output while keeping operations and maintenance costs to a minimum.
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