The water footprint of solar power may rarely come to mind. It should because cleaning the dust off of photovoltaic panels requires hundreds of millions of gallons of water per year. In a bid to come up with a solution, MIT scientists have recently invented an alternative cleaning system that replaces water with electrostatic repulsion.

Solar farms are often installed in desert regions, where they can benefit from long sun exposure and large swaths of flat land. Such arid places also have a lot of dust and sand in the air that accumulates on solar panel surfaces, interfering with their efficiency at producing renewable energy.

The problem with cleaning solar panels 

The surfaces then are often rinsed with fresh water to get rid of that layer of dust and sand. All too often that water has to be transported from far away, further exacerbating the technology’s environmental footprint. Not only that, about 2.7 billion people around the world experiencing water scarcity, and all that water could instead be used for drinking or irrigation.

Some smaller-scale solar farms brush off the dust from the solar panel surfaces without water, which can cause irreversible scratching damage on top of the solar panel surface, compromising the technology’s performance over time. That’s where MIT’s new cleaning system comes in.

Solar panels “power” washing themselves

The technology features an electrode in the form of a panel-wide motorized metal bar, together with an ultra-thin conductive surface coated with aluminum dipped in zinc oxide. The transparent film is designed to be layered on top of the sun-facing surface of a solar panel.

When there’s too much dust on the surface, the electrode sends an electrical charge to the bar, which passes closely over the panel’s surface on a set of rails. The electrical charge produces an electrical field that charges the dust particles. An opposite charge is then applied to the transparent conductive layer, repelling the particles.

The entire process can be operated automatically, powered by the solar panel itself. One caveat is that for the process to work smoothly the ambient humidity needs to be above 30 percent — which the researchers say can be found in most deserts throughout the most part of the day. On the other hand, compared to previously developed electrostatic-repulsion systems, MIT’s system can function at an ambient humidity as high as 95 percent.

Source study: Science Advances — Electrostatic dust removal using adsorbed moisture–assisted charge induction for sustainable operation of solar panels