Raphael Thys
Illustration of dust removal from a solar panel using static electricity
Static electricity could remove dust from desert solar panels, saving around 45 billion litres of water every year.
Some of the largest solar farms in the world are in deserts, such as Mohammed bin Rashid Al Maktoum Solar Park in the United Arab Emirates and Desert Sunlight Solar Farm in California. These environments tend to be very dusty, with particles quickly accumulating on solar panels. One month’s dust build-up can cut a solar panel’s output by around 40 per cent.
One of the most common ways of removing this dust is to spray large amounts of distilled water onto the solar panels. With an estimated 45 billion litres of water being used every year just to clean solar panels, the process is costly and unsustainable, says Kripa Varanasi at the Massachusetts Institute of Technology.
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“That amount could provide water for over a million people [every year],” he says.
To help solve this issue, Varanasi and his colleagues created a water-free way of cleaning solar panels via static electricity in the laboratory.
Dust doesn’t ordinarily conduct electricity. This changes, however, when moisture in the air attaches onto the surface of a dust particle – a process known as adsorption. The thin glass sheets that cover solar panels also aren’t conductors. To change this, Varanasi’s team added a 5-nanometre layer of transparent zinc oxide and aluminium to a solar panel’s surface.
A metallic plate was then hovered above the dust-covered panel, and an electric field of around 12 kilovolts was applied between the plate and the panel. This caused both layers to become electrodes, conductors that make contact with a non-metallic part of a circuit.
The solar panel and dust then became positively charged, while the metallic plate became negatively charged. As the plate swept above the panel, dust particles started to repel each other, causing them to disperse.
At around 30 per cent relative humidity, the dust particles adsorbed enough moisture to be completely removed from the solar panel in the laboratory, restoring 95 per cent of its lost power output. Even the driest deserts have a relative humidity of about 30 per cent, says Varanasi.
“I think water is a precious commodity that is very undervalued,” he says. “What I’m hoping is this will spur more people to think about water issues.”