Solar facilities have long been anticipating this eclipse, mapping out step-by-step demand management for the day of and arranging substitute energy sources to dispatch depending on various demand scenarios. Thanks to the unusually wet winter in California, hydroelectricity is abundant this year, says Greenlee.

In the past few months, CAISO — which manages 80 percent of California’s electric flow — has been busy seeking advice from German solar facilities.

During a 2015 solar eclipse that passed over Europe, 80 percent of Germany’s sunlight was cut off. For a country whose electricity is 40 percent powered by solar, it was hit hard. But despite the dramatic seesawing of solar production, the eclipse came and went without major disturbance. As I wrote for NOVA Next, Germany stabilized its grid and electricity supply by dialing up its fossil fuel, nuclear, and hydro power, while also asking four energy-hogging aluminum smelters to dial down their power use temporarily.

The California Public Utilities Commission (CPUC) is similarly encouraging user reduction from 9 to 11 am on the day of the eclipse. In a recent press release, CPUC stated that consumer cooperation would mean CPUC wouldn’t have to rely on inefficient, expensive, and often fossil fuel–dependent peakers (or “last resort” power plants) to make up for the imbalance of supply and demand.

However, Michael Picker, president of CPUC, doesn’t believe the eclipse will have a serious impact on CPUC’s ability to provide service on the morning of August 21. “We have been planning and thinking about it for a while to come, so I don’t think there will be any surprise,” he says. “I think this is well within the range of the many scenarios that the Independent System Operator actually models.”

Thankfully, the time at which the eclipse is expected to hit California is not the time of peak electricity use. Usually, peak usage curves from 4 to 9 pm. Picker hopes this eclipse will instead start a conversation about what it means have a grid that’s heavily reliant on fitful natural resources.

California isn’t the only state anticipating the eclipse’s impact on its solar capacity, though. The eclipse will cut through a total of 14 states, many of which have also become dependent on solar generation. At the time of highest impact — 1:40 EDT (10:30 PDT) when the eclipse is passing through Wyoming — the MDA solar forecasting system predicts solar generation potential across the country will decrease to less than 50 percent of capacity.

Georgia, Tennessee, Missouri, Idaho, and Oregon in the path of totality have all added a sizable amount of solar into their electricity markets. According to the EIA, Oregon has 17 utility-scale solar PV generators, mostly in the eastern part of the state, that will be impacted by the eclipse.

North Carolina — second only to California in installed capacity — powered 371,000 homes with solar energy this past year, and it is expecting a drop in solar output from 2.5 GW to 0.2 GW for 1.5 hours around the time of the eclipse. In a blog post, Duke Energy, which handles more than three-quarters of the nearly 3.3 GW of solar power generated in North Carolina, said that “operators will have natural gas plants ready to step in during the eclipse. In addition to replacing the lost energy with a flexible fuel source, operators can gradually decrease solar production before the sky darkens depending on weather conditions.”

Over the years, CAISO and other electricity operators have been trying to resolve the obvious limitations the industry faces during major events like eclipses. Francis O’Sullivan, research director at the MIT Energy Initiative, predicts that following the eclipse, there will be an “increased focus on ensuring that we have backup that’s more flexible.” And while the upcoming eclipse will inevitably test the US solar economy, hopefully it will give experts a better understanding of whether the intermittencies will impede solar expansion across the country.

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