California Prepares For An Eclipse Of Its Solar Power

Spectators around the country are gearing up, eclipse glasses at the ready, for the solar eclipse on Aug. 21. But another group — perhaps more anxious than eager — is preparing as well: the people who run California’s electric grid.

California is home to almost half of all the solar power in the country. So, even a partial loss of the sun will mean a major dip in the energy supply.

“We’re doing a lot of coordination, a lot of preparation,” says Deane Lyon, a manager at the California Independent System Operator (ISO), which manages about 80 percent of the state’s electric grid. “It’s probably the most work this company has done to prepare for a three-hour event in our history.”

Solar power already comes with up and downs, in the form of clouds.

“So this was a particularly cloudy day,” says Jan Klube of Enphase, pulling up a graph showing the solar output from one California home. The Petaluma-based company monitors rooftop solar systems around the country day in and day out.

To show how a single cloud can make a difference, he points to the afternoon hours, when the output dips by about a third. “You see the big drop, so there’s a cloud coming and going,” he explains. “That’s why you see the zigzag.”

If your solar panels are in the path of totality during the eclipse, “it will go all the way to zero,” he says.

California isn’t squarely in the path, but the moon’s partial shadow will obscure 90 percent of the sun in the north, down to nearly 60 percent in the south. That’s more than enough to cause some anxiety for the people who have to keep California’s lights on.

Read more at NPR