Scientists are borrowing a NASA dust-zapping trick to keep solar panels cleaner in dusty places like the American Southwest, India, and the Sahel, and the payoff could be cheaper power with less water and labor

Solar power is booming across the US, but a recent report from Carnegie Mellon University shows there is a quiet problem sitting on top of every solar panel: dust. The accumulation of dust, pollen and grime, or “soiling” as it’s called in the industry, can have a dramatic effect on the amount of power a panel produces. The problem is most acute in sunny, dusty areas like the American Southwest, India and the Sahel.

The solar industry’s quietly costly problem: dust
A 2016 review of dust research in Renewable and Sustainable Energy Reviews found that soiling can reduce a solar panel’s output anywhere from a couple percent to as much as half, depending on where the panel is located and how often it’s cleaned. That could mean lost revenue of as much as 60% in some areas, according to Provenzano. Most of the solar farms today are still cleaned by hand or with robotic equipment using water, which Provenzano said can cost solar farms hundreds of acres in size millions of dollars a year, which is why many operators put off cleaning and just let dust build up.

Borrowing a page from the Mars rovers
Enter Clear Solar, a startup from Pittsburgh, founded by Michael Provenzano, a Tepper School of Business graduate and member of CMU’s VentureBridge program, which helps startups founded by CMU alums with funding and mentorship. According to Provenzano, Clear Solar licensed a dust-clearing technology developed for space missions called an electrodynamic dust shield. NASA developed the technology at its Kennedy Space Center to keep equipment such as solar panels, camera lenses and spacesuits dust-free on the Moon and Mars, where there is no one around to wipe a panel clean by hand, the agency said.

Dust has always been one of the most persistent problems of space exploration. The urgency, it turns out, goes back to the Apollo era, when astronaut Gene Cernan wrote in his Apollo 17 mission debrief that dust was the one obstacle the crew never managed to fully surmount, according to NASA's own technology archives. More recently, NASA records show that the Opportunity rover's 14-year run on Mars came to an end in 2018 when a planet-wide dust storm covered the rover's solar panels and cut off its power. NASA officially declared the mission complete in February 2019. Provenzano, who learned about dust-shield technology while working at the aerospace company Astrobotic, says the same fix can be used on Earth. Provenzano says the shield removes 97 percent of the dust from the surface of a glass panel.

The zap, in simple terms
According to Provenzano, the process is multi-faceted: thin conductive lines are etched into the glass of a panel and then covered with a clear protective film. An electrical current charges the dust on the surface. A rapid change in the direction of the current kicks charged particles off the glass. There is a possibility of dust settling down, but the panels are usually tilted in such a way that gravity and wind keep them clean. Also, the system can run several times a day, so the current can be redirected to push dust down rather than onto neighboring panels, Provenzano said.

The system makes financial sense, too, Provenzano says. Costing about $0.14 to clean one megawatt of panel capacity, or roughly 2,000 panels, the dust shield slightly reduces a panel’s energy transmittance by about 1%, but the savings of not having to clean manually that frequently offset that loss. Clear Solar has 13 pilot projects under way around the world, including one near Pittsburgh, and larger field tests are scheduled to begin in July.

Why this could matter beyond the balance sheet
According to Stewart Isaacs, an assistant research professor at Carnegie Mellon University, African dust can cut power output by more than half in the dirtiest locations, which matters most in places that rely on solar as their only realistic power source. Isaacs uses computational models to study the effect of soiling on performance at different levels of severity and is also exploring how the physical form of a solar panel might interact with natural wind flows to extend the interval between cleanings.

Alan Scheller-Wolf, a professor at the Tepper School of Business who studies renewable energy supply chains, says that cleaning is part of the larger investment case for solar. Efficiently running expensive equipment preserves the value of a long-term asset. He also presents it as a sustainability issue: a panel’s useful life can be extended, meaning it needs to be replaced less often, cutting down on waste and resource use over time.

Dust may seem like a small thing, but as solar scales up across the country, figuring out how to keep panels clean cheaply may be just as important as building the panels themselves.