A Total Eclipse of the Grid?

In most cases, claiming that an event which starts and finishes within a span of only three hours can rattle global energy markets would be a bit of a stretch.

Of course, a total solar eclipse isn’t an average occurrence.

And California, which was near the center of the eclipse’s path, does not have an average energy grid. While fossil fuels still play a critical role in keeping California’s lights on, the state now boasts roughly 10 gigawatts (GW) of solar generation capacity — roughly five times the capacity of its last remaining nuclear power plant.

As the solar eclipse moved in, that solar capacity was cut by more than 60 percent across the state before reversing, triggering serious headaches for those tasked with grid reliability. However, it also presents an interesting case study, as California’s ongoing push towards increased battery storage, demand response and natural gas peaking plants faced their toughest test to date.

According to CAISO, California’s grid operator, the state was up for the challenge. (See solar generation data, including the eclipse dip on Aug. 21, below.) Success under challenging conditions for a renewable-heavy grid is sure to garner some global attention.

The California example offers a window to the future. Europe has fully nine years to prepare for an eclipse that covers the region, but grid operators are already making plans.

The UK’s National Grid, for example, recognizes that solar will be a more important part of the energy mix by then.

Last time (in 2015), only 6 GW of solar capacity was in place and the effect was further mitigated by 90 percent cloud cover dampening solar generation potential. By 2026, estimates suggest that installed capacity could grow to 26 GW so renewable energy will have a far greater influence. However, by happy circumstance, the eclipse will happen around 7pm and the lower solar intensity means that a dip of only 2-4 GW is likely. Other countries such as Germany are further down the road on solar and face greater supply gaps.

Interestingly, forecasters are almost equally challenged by modeling human behavior around such events. How much will demand dip as people put on solar filter glasses and head outside to watch the show? And how significant will the subsequent pickup be as Brits switch on kettles en masse to discuss the event over their traditional cup of tea?

Eclipse related or not, however, it’s clear that grid operators have to integrate the intermittent nature of solar and wind power within their balancing and forecast models. Variations in cloud cover, solar intensity and wind speed occur throughout the day, week, month and season. And how these variations interact with demand results in growing, complex challenges.

So what’s in the toolbox to address these concerns?

On the generation side, gas-fired backup power stations or pumped-storage hydro offer fast response to short-term demand variations. The more interconnected a grid is, the greater the ability to smooth out weather variations across a larger geographic area. Increasingly though, technological and data developments will be key.

The evolution of energy storage at scale to capture excess energy and supplement the grid at times of tighter supply will be important. Tech-enabled demand-side response and distributed generation will also have an increasing role to play in responding to pricing signals to mitigate the effects of intermittent renewables, and indeed to turn them into an asset.

Delivering such innovation offers a future that is bright, even when the sun may not be.

Check out other posts on issues affecting energy supply and grid balancing.