What happens to solar power generators during the eclipse?

As Americans get ready for their first total solar eclipse in 38 years, solar utilities in its path Monday are preparing for the moment their power source will disappear.

With 1,900 solar power plants expected to be fully or partially offline when the sun will be obscured by the moon, electric utilities have backup power sources covering from 1:30 p.m. to 3:40 p.m. to prevent any blackouts.

According to the U.S. Energy Information Agency, only about 17 utility-scale solars are located on the path of the total eclipse, known as totality. Most of those are in eastern Oregon. Hundreds more in North Carolina and Georgia will be at least 90 percent obscured, totaling about 4,000 megawatts of capacity. Another 2,200 to 4,000 megawatts are in areas that will be 80 and 70 percent obscured. (A megawatt is enough electricity to power about 1,000 homes).

Power companies and grid operators feel confident they can meet demand. PJM Interconnection, which operates the grid in 13 states and the District of Columbia, will need to make up 2,500 megawatts of power.  California’s grid operator, the California Independent System Operator, will need to dispatch 6,000 megawatts

North Carolina-based Duke Energy, the largest utility in the Carolinas, is expecting solar production to plummet from 2,500 megawatts to about 200 megawatts.

“What we’ve been doing is running various scenarios of what the weather conditions could be that day,” said spokesman Randy Wheeless in an interview. “In the most extreme example would be a very sunny day with low humidity where we are probably getting 2,500 megawatts of solar during that time of the day.”

The U.S. has grown more dependent on solar energy in recent years. The country’s total solar energy capacity has increased from just 5 megawatts in 2000 to 42,619 megawatts last year, according to the North American Electric Reliability Corporation. Demand is expected to remain strong as prices for solar panels continues to drop.

Though California isn’t in the path of totality, it will experience the biggest impact from the eclipse, which is expected to affect about 75 percent of the state’s solar capacity in northern California and about 60 percent in southern California. California ISO, which operates much of the state’s power grid, said it had enough energy stored to make up for the lost production during the eclipse.

“I am confident in the technology of our market and grid, and in the expertise and abilities of our staff,” said Steve Berberich, CAISO’s chief executive.

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