Every night once the sun sets on a solar field in south Israel, robots go to work cleaning panels. They awaken at the same time each evening and work without human intervention.

For the emerging solar power industry, keeping panels clean is incredibly important and will be a significant business. Research has found a solar panel can lose 40 percent of its ability to collect energy if covered in dust. In areas prone to sand and dust storms, keeping panels clean is a constant battle.

Hiring humans to clean panels with water is expensive, especially in a desert, where solar fields are often located due to a wealth of available land and sun exposure. Traditional manpower was the solution Arava Power CEO Jon Cohen had to rely on when Ketura Sun — a solar field in the Negev desert — opened in 2011.

“It’s very primitive. Obviously [it’s] having to work very cautiously because you’re talking about three- to four-meter poles with a squeegee attached to the end,” Cohen said. “If you do a full swing with them you could crack and damage a panel.” At times a sand storm would hit immediately following a cleaning, wiping out days of work.

In March of this year, Arava Power begin cleaning its 18,200 panels at Ketura Sun with 84 robots from Ecoppia, an Israeli start-up. The robots finish the task in under 60 minutes a night, charge themselves with solar energy and don’t require water to operate. In case the weather is cloudy, they maintain enough energy to work for three days. Cohen says the robots are more cost effective than cleaning by hand, and he plans to install them on six additional solar fields Arava Power will be opening.

While the robots are programmed to run automatically, an operator can intervene if needed.

“You can be in San Francisco and you can easily control your solar parks in Ghana, Namibia, India and Saudi Arabia,” Ecoppia chief executive Eran Meller said.

The Ecoppia E4 isn’t the only example of a company using robots to clean solar fields, but its ability to function without water or human oversight helps it stand out.

Serbot, a Swiss company, has a robot that cleans rows of solar panels with water and requires a human operator. Watch it in action below:

The massive Ivanpah Solar Electric Generating System in California relies on robots from BrightSource to clean panels. And solar energy company SunPower recently acquired Greenbotics, which makes a robot that cleans panels.

The rise of robots in solar energy speaks to a larger trend, the automation of work as computer and machines do jobs humans once did. While coal, natural gas and nuclear power plants require significant staffs, solar fields can nearly run themselves.