How did renewables fare during Winter Storm Elliott?
Wind turbines in Schlewswig, Iowa. MISO, which manages the flow of electricity in all or part of 15 U.S. states, was able to export power to its southern neighbors in part because its wind turbines produced enough energy during the storm. (Photo by Christopher A. Jones/Getty Images)
A day after Christmas, as parts of the country were still digging out from Winter Storm Elliott, the Wall Street Journal’s editorial page, undeterred by the absence of much concrete data, already knew where to cast the blame for rolling blackouts implemented in parts of the South to keep the grid from collapsing.
“While there wasn’t a single cause for the power shortages, government policies to boost renewables snowballed and created problems that cascaded through the grid,” the editorial board wrote.
However, more than a month after the storm and the power cuts it triggered for customers of the Tennessee Valley Authority and Duke Energy in North Carolina, wind and solar energy — which made up just 9.2% and 3%, respectively, of U.S. power generation in 2021 — appear to have met, and, in some cases, exceeded, expectations, according to presentations by grid operators and utilities.
A joint Federal Energy Regulatory Commission and North American Electric Reliability Corporation inquiry into the power system’s performance during the storm is ongoing.
But the picture that’s emerged in the month since Elliott is one of inaccurate forecasting of how much electricity would be needed to weather the storm and large-scale fossil fuel plant failures and gas shortages that left grid operators scrambling to find enough power to meet demand.
“Almost no one got the load forecast right during Elliott, which was quite surprising,” said Joshua Rhodes, a research scientist at the University of Texas at Austin who focuses on the bulk power system. He added that, generally speaking, grid managers rely chiefly on thermal resources (power plants that convert heat into electricity like nuclear, coal and natural gas plants) in their planning for severe winter weather because of the intermittent nature of solar and wind.
“If you’re going to call yourself reliable baseload, you better be able to turn on and produce electricity when you’re called on,” he said.
In North Carolina, where about 500,000 Duke Energy customers for the first time ever had service cut to save the broader electric grid, company executives told the state’s public utility commission earlier this month that the company thought it had adequate reserve power to weather the storm.
But as electric demand grew well beyond forecasts, natural gas and coal power plants began to experience freezing instruments and other problems (a total loss of about 1,300 megawatts of generation) and power purchases from out of state didn’t show up, the utility was forced to cut power to avoid causing a larger grid collapse.
“All of our neighbors were tight,” Sam Holeman, a Duke executive, told the commission.
The company’s modest solar generation, which performed “as expected” during the storm, wasn’t much of a factor because the electric shortfall happened overnight. As of 2021, wind, solar and hydroelectric power made up just 7% of Duke’s electrical generation.
“We own what happened. We have set out on a path to ensure that if we are faced with similar challenges, we will see a different outcome and provide a better customer experience,” said Julie Janson, executive vice president and CEO of Duke Energy Carolinas, in a statement.
In the Tennessee Valley Authority’s service area, which includes 10 million people in most of Tennessee and parts of Kentucky, Mississippi, Alabama, Georgia, Virginia and North Carolina, actual electric demand surged well past forecasts, with TVA breaking its all-time record for single-day electric demand. At the same time, TVA’s 2,500 megawatt Cumberland power coal plant went offline early on Dec. 23, the authority said, because of frozen instrumentation. Other gas plants went offline “due to the cold,” a spokesman said, though more details will be available after a full internal review is completed.
Just 3% of TVA’s generation portfolio is wind and solar, but according to preliminary data from the federal Energy Information Administration, the relatively small amount of solar TVA has performed consistently during the storm.
“Our crews worked 24/7 to successfully restore some of the impacted generating units to service during the event,” spokesman Scott Fiedler wrote in an email. “We also purchased and imported generation from neighboring markets as much as we could, however, these efforts were challenged as surrounding utilities and market operators were also experiencing high demand.”
TVA was able to pull power from the Midcontinent Independent System Operator, which manages the flow of electricity in all or part of 15 U.S. states (Arkansas, Illinois, Indiana, Iowa, Kentucky, Louisiana, Michigan, Minnesota, Mississippi, Missouri, Montana, North Dakota, South Dakota, Texas and Wisconsin). Despite its own unplanned generation outages, MISO was able to export power to its southern neighbors in part because its wind energy production remained high during the storm.
“Wind saved the day,” said Simon Mahan, executive director of the Southern Renewable Energy Association, a nonprofit trade organization. “Had there not been nearly as much wind I think things might have been more severe.”
The situation forced TVA to cut power to thousands of customers, though an exact number hasn’t been released. Fiedler said TVA has also created a “Blue Ribbon Panel” that includes the former CEO of the Electric Power Research Institute, a former U.S. senator and the president of the American Public Power Association, to provide an independent perspective and insight on TVA’s internal review.
“This review will be transparent and will move with a sense of urgency as we identify gaps, lay out corrective action plans and make the necessary changes to allow us to better respond to such challenging events in the future,” he said. “We know there is work to do to fully restore confidence in TVA’s ability to reliably provide the energy 10 million people count on every day, and we are committed to meet that expectation for the future.”
When PJM, the nation’s largest grid operator responsible for coordinating the movement of electricity in all or parts of 13 states and Washington, D.C — a territory that numbers 65 million people — issued a call for customers to conserve power during Elliott, it set off alarm bells for people in the power industry.
After all, PJM had been under fire from consumer advocates who argued it was saddling customers in its territory with too much electric generation capacity.
Going into the storm, PJM had a forecast for electric demand of nearly 127,000 megawatts and called nearly 156,000 megawatts of capacity into action.
“We believed we had almost 29 gigawatts of reserve capacity available to absorb load and generation contingencies and to support our neighboring systems,” PJM staff wrote in a preliminary report earlier this month.
But as temperatures started to plummet, “a significant portion” of that generation fleet failed to perform, with as much as 46,000 megawatts of power offline by Christmas Eve as a result of fuel problems, equipment failures and other issues, PJM reported. That severely limited the ability of PJM to send electricity to its neighbors, like Duke and TVA. On Dec. 23, “PJM began curtailing exports as our capacity position deteriorated due to the generation failures that we were having.”
Most of those failures were natural gas power plants, followed by coal power stations. About 6,000 megawatts that went offline was listed in the “other” category, which includes renewables and nuclear, but a PJM spokesman declined to provide a more detailed breakdown due to what he said were confidentiality restrictions. PJM says the power generators that failed to perform when called upon face between $1 and $2 billion in penalties.
“I can tell you that wind and solar resources performed as the near-term forecasts projected based upon wind speed and solar irradiance,” PJM spokesman Jeff Shields said. At the end of 2021, renewables made up about 6% of the total generation mix.
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