Eclipse Aftermath How California Survived The Solar Crash

by Anna Gretz
August 24, 2017

The day of the Great American Solar Eclipse was long awaited, and carefully planned for, in the state of California. Utility scale solar loss was 3,400 MW (enough to power millions of homes), with a crash and rebound generation rate up to 70 MW per minute.

So… did the California grid pull through the first major test of solar power loss?


But how did they do it? Many different components went into the successful maintenance of electrical supply on the day of the eclipse. We’ll highlight some of the major players, then ask one of the questions on everyone’s mind.

Careful Planning The great thing about solar eclipses is that we can see them coming… for years. California’s Independent System Operator (CAISO), which oversees the operation of 80% of the state’s electrical power system, transmission lines, and electricity market, has spent months planning for the sudden loss, then return of solar power in California. This was the first eclipse with solar making up a significant piece of the energy landscape, so there wasn’t a huge precedent telling California how to cope with what was about to happen. For the most part, the state relied on hydro-electric power and thermal sources like natural gas to make up for the discrepancy, but the state tapped into some other, less obvious resources as well.

Smart Thermostats Roughly 1 million homes across the US are equipped with smart thermostats--some nest-equipped homes had already given their local utilities permission to pre-cool their houses to reduce power during peak demand hours, and other received messages before the eclipse offering similar services. All together, smart thermostats could reduce power by roughly 1,000 MW during eclipse hours, putting a major dent in the level of power California had to compensate for.

Favorable Weather For an August morning in California, the weather was relatively cool--no summer heatwaves to encourage people to crank up the AC. And even though the Bay Area fog bummed out some hopeful eclipse viewers, it kept temperatures low, and electricity demand lower than usual as well. The lower demand helped out the California grid exactly how you would think-- by demanding less power, utilities had less lose solar power to make up for.

Energy Storage The California grid had something at its disposal that utilities historically have never had: energy storage. Before the eclipse, CAISO said that it planned to use the energy storage at their disposal “to the maximum extent possible.” And to the fullest extent possible, energy storage delivered. The biggest issue? There just isn’t enough of it installed yet. With more energy storage, California’s grid would be even stronger than ever, and could handle even more solar power brought online.

Handa Yan, a PhD candidate at the Center for Energy Research at UC San Diego, studied the eclipse closely, and had her own conclusion about Monday’s results: more solar wouldn’t cause any problems for California’s grid.

“I think the grid can handle a surprising amount of solar penetration -- more so than we originally thought -- and it will be able to handle more once we get more battery storage online,” Yang said. The impact of solar power generation is only going to grow, playing a bigger and bigger role in energy production in California, and across the country. That means energy storage deployments have to grow along with it.

First, we asked whether or not an electrical grid reliant on solar power could survive an expected period of major solar loss. The answer? Yes. But what about an unexpected one?

This year’s solar eclipse came and went without any major hiccups in electricity delivery--thanks to CAISO conducting an orchestra of different energy sources working together to make up for solar loss. But in the case of an unexpected loss in solar power, CAISO’s careful planning wouldn’t be available.

But energy storage could be. With energy storage, the employment of backup power would be seamless… albeit less dynamic. But that’s a good thing.

The power and flexibility of energy storage as a large-scale tool is pretty appealing, especially when evaluated next to the alternative--expensive, greenhouse-gas-pumping generators. Most of the areas that experienced solar capacity shortfalls during the eclipse switched on gas generators to make up for the missing electrons, but there are additional disadvantages on top of the pollution and expense of this solution. Big gas generators use huge metal turbines to churn out electricity, and they take a while to ramp up, as well as cool back down after additional electricity is no longer needed. This means that a lot of natural gas plants have a minimum amount of time that they have to run if you want to justify the cost of starting them up, and burning additional fuel. Even though the level of solar energy caught up in the afternoon the day of the eclipse, the gas generators had to keep running.

The efficiency and simplicity of energy storage can enable the grid to avoid ramping up generators all together. Battery-stored energy can be deployed at a moment’s notice--way faster and more efficient than a generator. As California’s capacity stands, however, the state won’t be able to go generator-free anytime soon.

The eclipse is basically a perfect example of why we need energy storage… and it’s one of many. The solar eclipse got a lot of hype, but electricity supply and demand are always fluctuating, even on a normal day. Energy storage has the potential to strengthen and enhance our utility system 356 days a year.

“Being reliable, being dependable and continuing to build this reputation of being there when needed is really what comes out of this for the [energy storage] industry,” said Matt Roberts, VP of the Energy Storage Association. In other words, if energy storage keeps showing up and doing its job, it’s going to get more gigs in the future.