Several companies are developing or selling robots to aid in installation or cleaning, including the Swiss outfit Serbot, which makes robots that can wash the windows of glass skyscrapers as well as clean solar arrays.

Another start-up based in California, QBotix, has developed a robot that controls tracking operations, moving along an array and tilting the panels to follow the sun and maximize their output. Getting as much as 40 percent more electricity out of each panel than in a fixed-tilt system, said Wasiq Bokhari, the company’s chief executive, allows developers to build smaller, cheaper systems to meet their energy production targets.

“The solar market is very competitive, and people literally fight over single cents per watt, so by allowing such a dramatic decrease in overall power plant costs, we are bringing a lot of value to the market,” he said. The systems are now installed in five farms in the United States and Japan, with more scheduled to go in before the end of the year.

Alion’s installation system is designed to work on uneven ground, executives said, cutting down on the need to level acres of fields. First, a machine used to lay sidewalks and gutters spits out a long concrete track. After the track sets, Rover, which resembles an industrial warehouse cart on caterpillar tracks, installs the panels and glues them in place. Human workers then wire the panels into the system.

Spot can be controlled with a smartphone and runs on a solar-powered battery. It rolls along the rails beneath the panels, squirting water and passing over them with a spinning brush and a squeegee. It also has a standard hedge trimmer attachment that can cut vegetation from the ground.