September/October 2010

No water required: Keeping solar panels clean

One of the best places to put a solar panel is in the desert, but deserts are dusty, which means the panels have to be washed frequently so the dust does not stop them from capturing sunlight. New technology could provide a solution and allow solar panels to clean themselves.

According to Technology Review, the technology was developed for future rover missions to Mars, but it could work here on Earth to keep solar panels operating at peak capacity. It uses electrostatic charge to repel dust and force it to the edges of the panels. It can remove 90% of the dust on a solar panel in a two-minute cycle, said Malay Mazumder, a research professor at Boston University who led the work. "With this new technology, solar panels can be automatically cleaned without water or labor," Mazumder said.

The system takes advantage of the fact that most dust particles, particularly in dry environments, have an electric charge. A transparent electrode material such as indium tin oxide delivers an alternating current to the top surface of the panel. As it swings between being positively and negatively charged, it creates an electric field that repels positively and negatively charged particles. The electric field also helps to impart a charge to uncharged dust particles, allowing them to be quickly repelled as they come in contact with the panel. The researchers have designed the system so the electric field works its way from one side of the solar panel to the other, gradually moving the dust along until it falls off.

The system does not use much energy; electrical current is small, and typically it only needs to be on between two and five minutes a day, Mazumder said. The system could include a sensor to determine when the panel needed cleaning. The technology does not work if the dust gets wet and muddy, so it should be triggered to remove dust before it rains.

Mazumder's technology is one of two approaches NASA has funded for cleaning off solar panels. The other vibrates the entire panel to shake dust loose. It is still not clear which will prove more practical for space missions. Using vibrations is simpler and requires fewer modifications to the solar panel. But it does not remove fine particles as well as the electrical field approach. For terrestrial applications, Mazumder's technology will have to compete with other potential approaches to cleaning off solar cells without using water, such as blowing air on them or adding a nonstick layer.