To keep solar panels clean and working efficiently, they are sprayed multiple times a month with water, a precious commodity in the dry, sunny locales where most large solar farms are likely to be located.
Researchers now present a water-less way to clean solar panels. The technique, presented in the journal Science Advances, relies on static electricity and removes dust instantly without damaging the surface of the panel.
The Energy Information Administration projects that 10 percent of the world’s power will come from solar energy by 2030. Some of the world’s biggest solar power projects, located in China, India, Saudi Arabia and the United States, sit in deserts. These regions have abundant land and sunlight—and abundant dust and sand that can accumulate on solar panels. This can shrink the output of solar panels by a third in a month if not cleaned.
“There is so much work going on in solar materials,” said mechanical engineering professor Kripa Varanasi in a press release. “They’re pushing the boundaries, trying to gain a few percent here and there in improving the efficiency, and here you have something that can obliterate all of that right away.”
Solar panels are cleaned multiple times a month today using pressurized water spray. In desert regions, water has to be transported from elsewhere. Based on a global solar power capacity of over 500 GW, Varanasi and graduate student Sreedath Panat estimate that cleaning these panels used about 10 billion gallons of water per year, enough to supply drinking water for up to 2 million people in developing and underdeveloped countries. Plus, they write “water-based cleaning contributes up to 10% of the operation and maintenance cost of solar farms based on cleaning frequency.”
The novel method they propose makes dust particles fly off the surface of solar panels. The technique relies on electrostatic repulsion, the repulsive forces between charged particles. When the researchers pass an electrode above a panel, the electric field causes the dust particles to get charged. Then, they apply the same charge to the panel itself, which makes the dust particles leap off their surface.
While others have also developed similar electrostatic cleaning systems, the new one is simpler. Past designs have relied on mesh-like arrays of electrodes that can be embedded in a film integrated in the solar panel or installed on top of it.
The new system only needs an electrode. Implementing it automatically should be easy, the duo says. Guide rails could be installed on the edges of solar panels, and an electric motor could be used to periodically move the electrode over the panels using the rails.
A lab-scale prototype of the system worked for particles of different sizes, but it required a relative humidity of at least 30 percent. That’s because moisture absorbed by the dust particles is essential to make them more conductive for charging.
The good news, said Varanasi, is that most deserts actually fall in this humidity regime. And even drier deserts have higher humidity in the early morning hours, so the cleaning could be timed for those hours.
Source: Sreedath Panat and Kripa K. Varanasi. Electrostatic dust removal using adsorbed moisture–assisted charge induction for sustainable operation of solar panels. Science Advances, 2022.
Image: Courtesy of the researchers