Researchers from the Massachusetts Institute of Technology (MIT) have developed a method that uses static electricity to keep solar panels free of dust, removing the need for cleaning with water.
The research showed that dust can inhibit solar panel operation by up to 30% in only a month without cleaning and a three to four percent reduction in power output from solar panels would equal a loss of $3.3 billion and $5.5 billion in revenue.
The MIT team’s waterless, no-contact system uses electrostatic repulsion to make dust particles effectively jump off the panel’s surface. To make this happen, an electrode in the form of a metal bar is passed over the panel’s surface, giving the dust particles an electrical charge. A charge is then applied to the solar panel, which repels the dust particles, causing them to leap off into the air and away from the panel.
The new system can be operated automatically on a timer using an electric motor and guide rails on the panel’s side that would pass the electrode over the panel without directly touching the surface.
In practice, each solar panel could be fitted with railings on each side, with an electrode spanning across the panel. Using a tiny portion of the output from the panel, a small electric motor could power the belt system to move the electrode from one end of the panel to the other to remove all the dust particles. The whole process could be automated or controlled remotely. Alternatively, thin strips of conductive transparent material could be permanently arranged above the panel, eliminating the need for moving parts.
Experiments proved that the process works effectively on a laboratory-scale test installation using specially prepared laboratory dust samples with a range of particle sizes. The tests showed that humidity in the air provided a thin coating of water on the particles, which turned out to be crucial to making the effect work. The researchers performed experiments at varying humidities from 5% to 95% percent. As long as the ambient humidity is greater than 30%, almost all particles from the surface can be removed. The process can get challenging as the humidity decreases.
Many of the largest solar power installations in the world, including ones in China, India, the UAE, and the U.S., are located in desert regions. The water used for cleaning these solar panels using pressurized water jets has to be trucked in from a distance, and it has to be very pure to avoid leaving behind deposits on the surfaces. Dry scrubbing is sometimes used but is less effective at cleaning the surfaces and can cause permanent scratching that reduces light transmission.
By eliminating the water dependency and the buildup of dust and lowering the overall operational costs, such systems can significantly improve the overall efficiency and reliability of solar installations.
Water resources in India have always been a challenge. The World Wide Fund (WWF), in a report, had said that 30 Indian cities face imminent water-related risks unless immediate actions are taken to mitigate and curb climate change.
Addressing water usage in solar projects, the Ministry of New and Renewable Energy (MNRE) had issued a letter recommending efficient water utilization for cleaning modules in utility-scale solar projects. The ministry has said that project developers were using too much water to clean solar modules, and they should try to minimize wastage. The application of waterless robotic cleaning solutions is gaining greater acceptance in India.