With abundant sunlight and plenty of open space, deserts are an obvious place to put large solar arrays, but there’s a downside: lots of dust, and not enough rainfall to wash it off. A buildup on solar panels can reduce efficiency by anywhere from 7 to 40 percent, according to various research efforts. Cleaning them takes manpower and usually water, which raises costs. Now a handful of startups are aiming to do for the solar industry what the Roomba has done for people who hate vacuuming: Turn the job over to robots.

Ecoppia, a company founded last year in Israel, has been operating nearly 100 of its panel-cleaning robots at the Ketura Sun solar array in Israel’s Negev desert. Using