The California Department of Transportation (Caltrans) is buying 11 portable EV ARC solar-powered electric-vehicle chargers from Envision Solar of San Diego for almost $750,000. In July, Envision Solar received a one-year contract, with two one-year extensions, to supply state and local offices and departments with its moveable solar chargers. Each one fits inside a regular vehicle parking space and generates enough solar energy each day to power 150 miles of EV driving. The system maximizes its exposure to the sun through a tracking system that enables the solar-panel array to follow the sun, generating 18-25 percent more electricity than a fixed unit. Built-in batteries store the free energy, allowing electric vehicles to re-charge during the day or night.