California Prepares For An Eclipse Of Its Solar Power | KUOW News and Information

California Prepares For An Eclipse Of Its Solar Power

Aug 18, 2017
Originally published on August 18, 2017 12:29 pm

Spectators around the country are gearing up, eclipse glasses at the ready, for the solar eclipse on Monday. 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.

It's unprecedented because solar power has been booming in California. Some days, it makes up as much as 40 percent of the state's power supply.

While the full totality lasts only a few minutes, the moon's shadow will partially obscure the sun for several hours. California expects the solar power output to be cut roughly in half over that time.

During the eclipse, hundreds of thousands of buildings — both residential and commercial — that normally count on rooftop solar will need to switch to grid power instead.

Add that to the loss from big utility-scale solar farms and California will need to fill a power gap equal to what 6 million homes use.

"Luckily, we had a really good water year this year," Lyon says. "So we'll have some pretty good flexibility on the hydro." That wasn't the case during the past few summers, when reservoirs were low due to the drought.

What hydropower dams can't make up, natural gas power plants will. That includes large power plants that can respond quickly, as well as smaller "peaker" plants. The California ISO is scheduling extra power ahead of time to try to ensure the needs are met and that power prices don't spike.

The tricky part is that the sun will disappear and reappear two to three times faster than normal, which means the grid will have to be balanced carefully. Supply always has to meet demand, otherwise you get blackouts.

Grid operators say they're prepared because, with renewable energy on the rise, they've learned to deal with power dips every day. In recent years, the California ISO has beefed up its modeling and forecasting to handle the swings.

Other leading solar states will see an effect, too. Duke Energy in North Carolina expects to lose about 90 percent of its solar supply, though it has about a quarter of what California uses. It plans to use natural gas power plants to fill in the gap. NV Energy in Nevada expects to see an even smaller dip.

The next total eclipse, in 2024, could be an even bigger challenge for California and other states, when even more solar is in the mix.

"It'll be a major thing for the people running the grid at that time to manage," Lyon says. "It won't be me. I'll be retired for hopefully several years by then."

Energy officials are asking Californians to turn off lights and conserve energy for several hours on the morning of Aug. 21, just to give the grid a little extra help.

A version of this story also appeared on KQED's website.

Copyright 2017 KQED Public Media. To see more, visit KQED Public Media.

AILSA CHANG, HOST:

People across the country are gearing up for the solar eclipse on Monday - and not just spectators - energy supply managers, too, especially where you are, David.

DAVID GREENE, HOST:

Yeah, that's right. Almost half the solar power in the United States is generated right here in the state of California. And as Lauren Sommer of member station KQED explains, the eclipse will mean a dip for the power grid.

LAUREN SOMMER, BYLINE: Solar power already comes with ups and downs in the form of clouds, of course. Just ask Jan Klube of the company Enphase, which monitors solar farms around the country day in and day out.

JAN KLUBE: So this was a particular cloudy day.

SOMMER: Klube pulls up a graph showing the solar output from one California home. In the morning, the sun comes up. The power starts flowing. But in the afternoon...

KLUBE: All right, you see the big drop. So there's a cloud coming and going. That's why you see the zigzag.

SOMMER: It drops by about a third. But say your solar panels are getting no sun at all because they're in the path of totality during the eclipse.

KLUBE: It will go all the way to zero.

SOMMER: Effectively, nighttime. California isn't in the full path, but the state will lose 90 percent of the sun in the north down to nearly 60 percent in the south, more than enough to cause some anxiety for the people who have to keep California's lights on.

DEANE LYON: We're doing a lot of coordination and a lot of preparation. It's probably the most work this company has done to prepare for a three-hour event in our history.

SOMMER: Deane Lyon works at the California Independent System Operator, which runs most of the state's electric grid. Solar has been booming in California. Some days, it's as much as 40 percent of the state's power supply. The eclipse will mean solar output is cut roughly in half over the course of several hours.

LYON: We're also going to see a demand increase from the loss of the commercial and residential rooftop solar.

SOMMER: All those buildings that normally use rooftop solar will need the grid instead. Add that to the loss from big solar farms, and California will need to fill a power gap equal to what 6 million homes use. Other leading solar states, like North Carolina and Nevada, will also see a hit to a smaller degree. But Lyon says not to worry.

LYON: Luckily, we had a really good water year this year, so we'll have some pretty good flexibility on the hydro.

SOMMER: And what hydropower dams can't make up for, natural gas power plants will. Supply always has to meet demand. Otherwise, you get blackouts. Grid operators say they're prepared because with renewable energy on the rise, they already deal with power dips every day and have improved their forecasting. But Lyon says the next eclipse in 2024 could be an even bigger challenge with even more solar in the mix.

LYON: It'll be a major thing for the people running the grid at that time to manage. It won't be me. I'll hopefully be retired for several years by then.

SOMMER: Energy officials are asking Californians to turn off lights and conserve on Monday just to give the grid a little extra help. For NPR News, I'm Lauren Sommer in San Francisco.

(SOUNDBITE OF MONO/POLY'S "INTERGALACTIC") Transcript provided by NPR, Copyright NPR.