In the ancient world a solar eclipse meant one thing: a disruption of the established order. And so it is today, again. The U.S. is using so much solar power that it will have to prepare for the solar eclipse that will hit the country in August. As the shadow of the moon passes over North America, the eclipse is expected to knock out about 70 megawatts a minute. That’s not unmanageable, but it has prompted U.S. utilities to look for a solution to a new—and, in fact, welcome—problem: managing grids increasingly reliant on solar power.