Here is a water-free robot that can clean solar panels to maintain their efficiency. The ECOPPIA E4 moves on a rigid aluminum frame using polyurethane coated wheels and doesn’t put any load on your solar panels. It is powered by 5 motors, one for microfiber elements and 4 for moving up and down and along the panel row.
The E4 has two flexible coated silicon rubber wires. It has a cleaning rate of 54 square feet per 30 seconds.