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Image: Courtesy of the researchers

Large solar parks are often located in deserts. There is plenty of space here and the sunlight needed to generate solar power is guaranteed all year round. But there is another problem: dust. Because dust accumulates on the solar modules, their performance can be reduced by almost 30 % within a month. In addition, as dust storms caused by climate change increase, the efficiency of solar panels can drop rapidly unless they are cleaned several times a month. A common method of cleaning is to blast the panels under high pressure with water. To avoid re-contaminating or damaging the glass of the panels, only pure, demineralised water can be used. The cost of transporting the water to the often remote desert regions accounts for about 10 % of the total operating and maintenance costs. It is estimated that up to 10 billion gallons of potable water would be used each year just for cleaning solar panels, an amount of water that could meet the annual needs of about 2 million people in developing countries.

The inefficiency of current cleaning methods prompted Kripa Varanasi, a professor of mechanical engineering at the Massachusetts Institute of Technology (MIT), and his PhD student Sreedath Panat to develop a touchless cleaning system that can remove dust from solar panels automatically and without water. The system uses electrostatic repulsion to remove dust particles from the surface of the solar cells. The researchers had found that although dust itself is not electrically conductive, the particles can be charged by an electrode that runs directly over the surface of the solar panel. A transparent film (similar to that used on smartphones and laptops) is then given an opposite charge and applied to the panel. With the result that the glass surface of the panel repels the annoying dust particles. The system, which works with a small amount of solar energy, could be used in conjunction with a separate cleaning robot or retrofitted to the panels, they said.

While the MIT engineers want to make their new system scalable, other researchers are working on developing a coating technology for solar panels inspired by the self-cleaning properties of the lotus leaf. For example, German researchers at Ben Gurion University tried to develop a hydrophobic coating for silicon-based solar cells that would prevent dust from collecting on the surface.

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