A full solar eclipse, like the one sweeping across North America on Monday, will prevent solar power generation for facilities in the path of totality. This could particularly affect the parts of Texas in that path, as the Lone Star State has ramped up solar installation since 2017, the year of the last eclipse on the continent.
In the case of an anticipated event like an eclipse, utilities and grid operators are able to prepare in advance to make up for the loss and keep the lights on. But the actions they’re taking to gird the grid against the eclipse offer a preview of a more complex problem that stretches beyond the short time the sun will be blocked.
The path of totality is set to affect a swath of the U.S. from Texas to Maine with a collective solar power generation capacity of 6.5 gigawatts, according to the U.S. Energy Information Administration (EIA). While the moon will only directly block sunlight for about four minutes, sunlight in the path of totality could be limited for up to two hours, according to the EIA.
The agency projects Texas, due to its position in the path of totality, will lose between 90 and 99 percent of solar power generation during the eclipse.
Although solar power accounts for just a fraction of the energy generated in Texas, both generation and capacity in the state have expanded dramatically in recent years. A recent report from the nonprofit Climate Central indicates that the state’s solar capacity grew 37 percent last year compared to 2022, and that it was the number-two state for solar generation, behind California, with 31,700 gigawatt-hours.
“What’s different between now and 2017 is in 2017, the country had very little solar generation and now the country has a quite a bit and a lot of that solar generation is in Texas,” Thomas Overbye, director of the Smart Grid Center (SGC) and professor in the Department of Electrical and Computer Engineering at Texas A&M University, told The Hill in an interview.
“On a clear day we could get 25 percent of our generation from solar,” Overbye added. “If it weren’t for the eclipse we would get about 50 percent of our maximum solar and when the eclipse comes through that’s going to drop down to close to zero, maybe seven, eight percent maximum.”
Texas has enough battery storage to make up for about 25 percent of capacity, Overbye said, and the loss is offset by the role of natural gas in the grid’s energy mix.
It’s particularly fortunate, he added, that the eclipse is occurring during the spring, when the burden to the grid is lower.
Overall U.S. battery storage is also up considerably since the last eclipse, with the EIA estimating the U.S. has about 15.4 gigawatts of storage compared to just 0.6 in 2017.
Ultimately, however, the contingencies the Energy Reliability Council of Texas (ERCOT), which oversees the state grid, has taken for the eclipse point to a broader hurdle for adoption of renewables like solar and wind.
Detractors of renewable energy have frequently pointed to its dependence on weather conditions.
Former President and presumptive GOP nominee Donald Trump, for instance, said on the campaign trail in 2020 that solar and wind “would mean that America’s seniors have no air conditioning during the summer, no heat during the winter, and no electricity during peak hours.”
“As we transition the grid to one that is more dependent on solar and wind, we do become more weather dependent and that’s a challenge for us engineers, to operate a grid where a lot of your generation is weather dependent,” Overbye said. That’s already an issue engineers are actively researching, not only for rare, predictable events like eclipses, but also for more mundane scenarios like overcast conditions and low-wind sunsets.
But criticisms of this aspect of renewable energy often elide the role of battery storage.
Adapting that storage to handle these so-called renewable resource droughts is a major focus of renewables research, Overbye said.
“We’re looking at the ramifications those situations have on operating the grid. Looking at historical weather patterns… there are situations where that has occurred,” he said. “What we’re trying to figure out is how bad they would be if we had a renewable-dependent grid.”
Concerns surrounding Texas’s power generation in particular also touch on a variable that sets the state apart from the rest of the country: its self-contained grid. In early 2021, extreme winter weather killed 246 and knocked out the ERCOT grid. The grid was similarly taxed during extreme heat last summer.
While such scenarios are far less likely during an expected, short-term phenomenon like the eclipse, they illustrate what critics say are the pitfalls of a self-contained grid.
Rep. Greg Casar (D-Texas) has introduced legislation to incorporate ERCOT into the national grid, and specifically pointed to Texas’ solar capacity as an opportunity to also reduce the nation’s carbon emissions.
Ultimately, Overbye said, “my takeaway on the eclipse is the grid’s going to be fine. Yes, the eclipse is impacting solar and it’s going to go way down, but we’re prepared and It’s a once-in-a-generation event.”
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