Cleaning solar panels without water
They predict solar power to account for 10% of worldwide electricity output by 2030. Much of it is concentrated in desert areas where daylight is abundant. Yet, dust deposition on solar panels or mirrors is already a big concern — so such installations need regular cleaning.
Estimations show that washing solar panels consumes roughly 10 billion gallons of water every year. Which is enough to supply drinking water to up to 2 million people. Attempts at waterless cleaning are time-consuming and can result in irreparable surface scratching. As a result, scratching reduces efficiency. A group of MIT researchers has developed a dry, no-contact technique for cleaning solar panels or solar mirrors. They claim it might reduce the dust problem.
Cleaning solar panels without water or brushes, the innovative method employs electrostatic repulsion. This technique induces dust particles to detach and almost leap off the panel’s surface. The electrode passes above the solar panel’s surface to activate the system. Charging the dust particles with electricity, which are then repelled by a charge provided to the panel. You can use a simple electric motor and guide rails along the edge of the panel to automate the mechanism. Sreedath Panat, an MIT graduate student, and Kripa Varanasi, a professor of mechanical engineering, published a study in the journal Science Advances today.
“A basic problem like the dust may actually put a major dent in the whole thing,” Varanasi says.
Despite intensive efforts throughout the world to produce ever more efficient solar panels. Their lab studies show that the panels’ loss of energy production begins at the start of the dust build-up process. This effect can approach a 30% reduction after one month without cleaning. They projected that a 1% drop in power may result in a $200,000 loss in annual revenue for a 150-megawatt solar plant. According to the experts, a 3% to 4% decline in solar plant output would result in a loss of $3.3 billion to $5.5 billion globally.
Many of the world’s largest solar power plants are in desert areas. Including those in China, India, the United Arab Emirates, and the United States. For pressurized jets to be operational, the pure water needs to be transported from afar. Dry scrubbing can also be used, but it is an ineffective way of doing things because it can lead to permanent scratches on the panel surface.
Solar installations’ water cleaning costs account for around 10% of their total operating costs. But the researchers claim that the new approach might lower these expenses while increasing power output. This can be possible thanks to the more frequent automatic cleaning.
“The solar industry’s water footprint is mind-boggling,” Varanasi adds. Adding that it will continue to grow as these installations spread over the world. “As a result, the industry must be cautious and thoughtful about how to make this a long-term solution.”
Other groups have attempted to develop electrostatic-based solutions. But they have depended on an electrodynamic screen made up of interdigitated electrodes. According to Varanasi, these screens can have flaws that allow moisture to enter and lead them to break. While they would be helpful on a planet like Mars, where moisture isn’t an issue, he thinks they can be a severe problem even in dry regions on Earth.
Cleaning solar panels without water requires an electrode to pass over the panel creating an electric field. So the field then charges the particles and repels them with an opposite charge applied to a transparent conductive layer. The layer is a few nanometres thick and deposited on the glass covering of the solar panel. The researchers were able to find a voltage range strong enough to overcome gravity and adhesion forces and cause the dust to lift away.
Experiments on a laboratory-scale test installation confirmed that the technique works. The testing revealed that air humidity supplied a thin coating of water on the particles, which was vital to the effect’s success. “We did studies at different humidities ranging from 5% to 95%,” Panat explains. “You can remove all the particles off the surface as long as the ambient humidity is greater than 30%, but as humidity drops, it gets more difficult.”
“The good news is that when you get to 30 percent humidity, most deserts actually fall into this regime,” Varanasi adds. Even dryer deserts have increased humidity in the early morning hours resulting in good conditions for cleaning.
The researchers claim that their system can function at a humidity even as high as 95 percent. Which was the problem for many prior works on electrodynamic screen technologies.
In practice, each solar panel might have railings on both sides and an electrode spanning the entire panel at scale. A belt system driven by a small electric motor would move the electrode from one end of the panel to the other. While clearing the dust a small amount of the panel’s output would be used for the operation. We can automate the whole procedure or manage it from afar. Or in place of moving elements, small strips of transparent conductive material could be positioned above the panel.
Technologies like this have the potential to improve the efficiency and reliability of solars. By eliminating water usage and dust build-up and effectively cutting the operational expenses.
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