The state is expected to lose almost 4,200 megawatts during the eclipse, which will partially darken the state from about 7:45 am to 12:45 pm local time, with peak occlusion happening from 10:19 am to 10:30 am local time on Aug. 21, according to the ISO. To put that in perspective, 1 megawatt powers about 1,000 typical homes, so the eclipse could affect the equivalent of about 4.2 million homes, Greenlee said.
In addition, units that rely on power from rooftop solar panels will go offline, "which means that those mostly residential units will then look to the grid for their power support," Greenlee said.
When these units are added to the expected loss of 4,200 megawatts, the total estimated demand on the power grid will be about 6,000 megawatts, or the equivalent of about 6 million homes, according to the ISO. (California had a population of about 39.2 million people in 2016, according to the US Census.)
"[The 6,000 megawatts] is the amount of megawatts that we expect that we'll have to generate to make up for the effect of the solar ellipse," Greenlee said. "For us here at the ISO, we're going to need to make sure that we have our reserves properly procured," which involves having 100 percent of the expected demand plus an additional 6 percent in reserves, just in case, he said.
The ISO is talking with other energy providers, particularly natural gas, which provides about 53 percent of California's energy resources, Greenlee said. This way, the generators will know that they'll need to acquire more natural gas for the morning of the eclipse.
In addition, the ISO will have to properly time the fading out and sudden return of the sun's light. As the eclipse begins passing over California, solar-energy collection will decrease at 70 megawatts per minute until the sun is fully blocked by the moon. Then, as the eclipse ends, it will return at 90 megawatts per minute, which is "very fast," Greenlee said.
"The challenge on our end is going to be able to time bringing up the resources, the natural gas or the hydro-generation that we're going to need, as the solar is ramping down," he said. "And then, we're going to have to ramp the gas and hydro-generation down as the solar is ramping up."
Original article on Live Science.
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