t's a model that appears to be paying off. Solar is now a $15 billion business in the U.S., employing more people than coal mining, even as costs continue to decrease. Solar panels, for example, are twice as cheap as they were four years ago. In 20I4, solar energy accounted for 36% of the country's installed new energy capacity, according to the Solar Energy Industries Association. "It's hard to convey how this industry has gone from being like a small jewelry business to a bricks-and-mortar paving business," Atwater says. "And when Desert Sunlight was conceived, think people thought it was this ambitious California thing to do and wasn't very economical. But now it's economical