As Texas continued rotating power outages on Wednesday (Feb. 17), power industry experts found themselves battling misinformation about the root cause of the problems.

Texas Gov. Greg Abbott (R) and Rep. Dan Crenshaw (R) were quick to blame renewable energy, especially wind power, for the supply crunch the region has faced since Sunday night (Feb. 14).

"This shows that the Green New Deal would be a deadly deal for the United States," Abbott said in an interview on Fox News. "Texas has multiple energy sources, such as natural gas, oil, nuclear, as well as solar and wind. But ... our wind and solar were shut down ... putting Texas into a statewide power shortage."

However, data from the state's grid operator clearly shows that most of the outages were caused by constrained natural gas supplies and a massive spike in demand. Although no power resource performed perfectly, power industry experts rejected the claim that renewables alone caused the outages.

Still, many questions remain unanswered: Was Texas' grid operator prepared? How should power generators have planned better for this kind of extreme weather? And what should be done in the future? Can future rotating outages be minimized?

"This outage was not the fault of wind power," said Emily Grubert, assistant professor of civil and environmental engineering at Georgia Tech. "That doesn't mean that the wind system as it exists would have performed better if wind were a larger share of the grid. It means we need to be more prepared for emergencies. We need to think about how to design a grid that may face more extreme weather than in the past due to climate change. This is really not a fuel problem, it's a grid design problem."

What caused the outages?

The Electric Reliability Council of Texas (ERCOT) triggered rotating outages Sunday night (Feb. 14) after demand spiked and supply dropped simultaneously, hitting its system. Fuel delivery and plant operation problems worsened the supply-demand imbalance, preventing the grid operator from fully restoring power this week.

Last Thursday (Feb. 11), ERCOT issued a press release warning of potentially "record" electricity demand due to the winter storm brought by the polar vortex, urging generators to check fuel supplies and planned outages to prepare for the weather. By Sunday (Feb. 14), ERCOT urged users to reduce electricity use due to record demand and "higher-than-normal generation outages"—including frozen wind turbines and constrained natural gas supplies.

On Wednesday (Feb. 17), Dan Woodfin, senior director of system operations at ERCOT, clarified that the megawatts of offline thermal generation were "significantly" higher than renewables—about 28,000 MW of thermal generation was offline, while about one-third of the expected 18,000 MW of wind capacity was offline. Although ERCOT did not break down thermal generation by source, most of its winter peak capacity relies on natural gas, and most thermal issues were related to frozen natural gas wells and pipelines, with one nuclear reactor going offline on Monday (Feb. 15), accounting for about 1,300 MW of thermal outages.

"The storm caused a large number of generating units to go offline," ERCOT CEO Bill Magness told reporters Wednesday (Feb. 17). Frozen wind turbines, natural gas pipelines, gas wells and other critical equipment forced the grid operator to implement outages to avoid "catastrophic outages" and an "indefinite end date."

Ultimately, the grid operator was dealing with a peak demand of 69,150 MW on Sunday (Feb. 14), far above its winter forecast peak of 57,699 MW and above the record of 65,915 MW set in January 2018. Meanwhile, ERCOT's "extreme" outage scenario predicted a peak thermal outage of 13,953 MW, while actual outages on Sunday were more than double that forecast.

"This is the root of the disaster," Princeton assistant professor and energy systems engineering expert Jesse Jenkins said on Twitter, adding that poor wind performance was "secondary." Examining ERCOT data, Jenkins found that wind and solar resources were sometimes about 4,000 to 5,000 MW lower than expected, but also often exceeded the expected 6,200 MW.

"The main problem remains the failure of thermal power plants—natural gas, coal and nuclear—that ERCOT counted on to perform when needed," he said. "They failed. Of about 70,000 MW of thermal capacity in ERCOT, about 25,000 to 30,000 MW have been offline since Sunday night. That's a big problem."

ERCOT officials noted that part of the problem is also the lack of cold-weather retrofits for generation resources, based on Texas' typical climate. Generators in colder climates typically invest in various de-icing measures to ensure wind farms operate at maximum capacity in winter. But in a warmer state like Texas, individual generators may be reluctant to invest in the same cold-weather protection. The same applies to thermal plants—in southern climates, facilities typically do not build enclosures to maximize efficiency and prevent units from overheating in summer heat, but this makes plants more vulnerable in cold weather.

Woodfin said this partly explains why all resources struggled during the storm. "In different ways, extreme cold, snow and so on affected every type of generator," he said.

How should grid operators respond to "unprecedented" weather?

Michael Craig, assistant professor of energy systems at the University of Michigan, said the challenge of planning for outages as widespread as those ERCOT experienced this week is that grid operators tend to prepare for winter and summer peak loads based on historical data, but as climate change makes weather more unpredictable, those forecasts will no longer apply.

"If you only plan based on historical events ... that's not enough," he said. "We thought that in five, ten, or fifteen years, planning based on historical events would be insufficient. But we quickly realized—like California this summer and other events—that it's already insufficient now."

This summer, California's record heat wave caused demand to surge, while generation was lower than expected and electricity imports were constrained, forcing the state's grid operator to implement rotating outages. In Texas, the winter weather over the past week was the coldest in decades, triggering different generation problems, but the end result was similar: rotating outages under extreme weather.

"What we've seen this week is a historic, unprecedented weather event that has spiked the demand side of the grid balancing equation," Magness told reporters Tuesday (Feb. 16), adding that these events "basically broke" ERCOT's previous winter records. "We saw ... winter demand higher than ever before, almost comparable to summer peaks," he said.

Craig said such extreme temperatures are difficult to plan for. "We could spend billions, tens of billions of dollars to make sure nothing goes wrong. But we don't want to waste money," he said. "We don't want to overspend, because those costs are borne either by private investors or, in many markets, by users." The key is balancing reliability with spending, but "climate change makes that balance very complex."

Moreover, Grubert said, breaking down system failures by generation source does miss the point when considering broader planning. Although natural gas was the main factor this time, in both Texas and California, "in both cases, the major systems that make up the majority of the grid also struggled under extreme conditions," she said. "Recognizing that the conditions we're seeing would make it difficult for any system to cope is important and a key consideration for planning."

In 2011, Texas also experienced "unusual" cold weather, when 210 generators across the state experienced outages or failed to start, leading to more than 5,000 MW of load shedding over three days. These events triggered federal investigations by the North American Electric Reliability Corporation (NERC) and the Federal Energy Regulatory Commission (FERC).

Ultimately, according to Woodfin, NERC adjusted its recommended "best practices" into non-binding "guidelines" for generators. Generators within ERCOT submit their cold-weather plans to the Public Utility Commission of Texas, and ERCOT regularly "spot checks" about 100 of the roughly 600 units in its jurisdiction to ensure these best practices are implemented.

Woodfin said these practices have worked during the cold weather events the region has experienced since then, "but as the more extreme cold weather event over the past few days has shown, clearly, these practices were not enough to keep those generators online."

FERC and NERC announced they would again launch investigations into the affected regions, which include the Southwest Power Pool and the Midcontinent Independent System Operator's territory.

"In the coming days, we will investigate the root causes of these reliability events," FERC Chairman Richard Glick said in a statement. "But for now, the focus must be on restoring power as quickly as possible and keeping people safe during this extremely challenging situation."

Casualties

According to PowerOutage.US data, nearly 2.4 million customers in Texas were still without power as of Wednesday evening (Feb. 17), with about 500,000 customers without power as of Thursday morning (Feb. 18), after outages peaked at nearly 4.5 million customers in the state. According to The Weather Channel, at least 17 deaths had been attributed to the storm and the resulting outages as of Wednesday evening (Feb. 17).

Grubert said that in assessing ERCOT's and the overall power system's response, it's easy to overlook the human element in system planning—that is, keeping people safe.

"I think, in some ways, asking 'How do we make sure the power doesn't go out?' is the wrong question," she said. "The question should be 'How do we make sure people still have safe temperatures during events like this?' The answer to that question may partly be 'Don't let the grid collapse.' But focusing solely on keeping the grid running, I think, goes in the wrong direction in several ways."

Extreme events are difficult to plan for and replicate, she said, especially as weather patterns change and become more variable. "Another very important point in this conversation is that even if the power doesn't go out, many people are exposed to very dangerous conditions."

According to Magness, as of Wednesday afternoon (Feb. 17), ERCOT was still shedding 14,000 MW of load to prevent "catastrophic outages" and an "indefinite end date." ERCOT could not provide a timeline for restoration, but officials said they could not stop the outages until supply and demand returned to balance.

"We've been working hard to restore balance so we can operate the system reliably and safely going forward," Magness said. "Unfortunately, that has meant we've had to maintain many outages for far longer than anyone would have hoped. The terrible consequences are obvious. It's dangerous for people to be without power in Texas' coldest weather. When we have problems like this, the essential nature of this service becomes very clear."