If the temporary blotting out of the sun next week magnifies an inherent weakness of solar power, it also plays to the strengths of energy storage.
Advanced energy storage technologies have the ability to charge or discharge at a moment’s notice to shore up the needs of the grid. Whether or not the market structures exist to fully capitalize on those abilities is another question.
There’s little grid storage to speak of directly on the path of totality, where the sun will be entirely covered for a period of 2.5 minutes on Monday. That swath cuts southeast from Oregon to South Carolina. Indianapolis Power & Light has a 20-megawatt system just off of the path. Farther from the line, the sun will be 60 to 80 percent obscuredabove many of the nation’s largest solar plants in California, Nevada and Arizona.
The California Independent System Operator expects this to cause a shortfall of 6,000 megawatts that otherwise would have been produced by solar power between 9 a.m. and noon.
California also wields considerable storage capacity: approximately 3,000 megawatts, said Alex Morris, policy director at the California Energy Storage Alliance. Some 2,600 megawatts of that are from old-school pumped hydro, with newfangled batteries making up the difference.
Members of the storage industry hope their response to the eclipse will demonstrate the flexibility of this tool and expand the opportunities for storage to help the grid in future challenges.
The grid response
Dealing with capacity shortfalls, especially ones with as much advance predictability as this one, is no trouble for grid operators. All they have to do is call up additional gas generators to pump out electrons when the sun starts to darken. This can get expensive, though, and involves a lot more greenhouse gas production than the solar would have.
The other trick is what happens on the back end. Gas generators spin large metal turbines to generate electricity, and there are physical limitations to how quickly those machines can stop spinning without damaging themselves. Many plants also have minimum run times they need to hit to justify the cost of starting up and burning fuel.
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