Houston — Grid operators across the US shed loads amid a bitter cold snap that triggered widespread power outages and emergency measures to limit and prevent them.
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As of midday Feb. 15, more than 4 million customer accounts were without power across the US as frigid Arctic air blanketed the nation, according to poweroutage.us, which aggregates US utility outage data. Most of those accounts, 3.4 million, were in Texas. Meanwhile, some 325,000 customers in Oregon, 117,800 customers in Louisiana and 108,000 in Virginia were left in the dark. (Customer accounts can include more than one person).
The Electric Reliability Council Of Texas Inc., which operates the grid for most of Texas, was hit particularly hard, with state officials, grid operators and regulators pleading with residents to reduce consumption after more than 30 GW was forced offline, the worst blackouts in the state in decades. ERCOT issued an emergency alert as reserve margins, the difference between total power supply and demand, dropped below 1,000 MW. At its highest point, the grid shed about 10.5 GW of customer load, enough to power 2 million homes.
"Every grid operator and every electric company is fighting to restore power right now," ERCOT President and CEO Bill Magness said in a statement.
In the early hours of Feb. 15, generators began tripping offline in ERCOT. Natural gas generators faced low gas supplies, while ice froze wind turbines, grid officials said in a Feb. 15 call. In turn, transmission providers faced difficulties balancing supply and demand. The majority of plants that went offline overnight were thermal generators, officials said.
Texas by far leads the nation in wind generation capacity and is experiencing a solar power boom that could bring hundreds of megawatts of new capacity online in the next few years. The culprit in the current shortfalls is not a surfeit of variable renewables, though, but the inability of conventional fossil fuel generation to keep up.
"Total wind output is slightly below expectations, but the main supply issue is lack of available thermal generation (both gas and coal) due to freezing conditions" in Texas, said ICF International Inc., a consulting firm. Gas production dropped at least 16% because of well freeze-offs and shutdowns of processing plants, ICF said. ERCOT's extreme peak load scenario anticipated wintertime demand of up to 67.5 GW, but the day-ahead forecast for 8 am Central Time (1400 GMT) Feb. 15 was 74.5 GW.
The "magnitude of the forecast error was massive," ICF said. "While ERCOT's forecasts are largely indicative since they lack a capacity market mechanism, nevertheless many observers reference ERCOT's forecasts for their own planning purposes."
President Joe Biden on Feb. 14 declared an emergency in Texas and authorized the Department of Homeland Security to coordinate disaster relief efforts "to save lives and to protect property and public health and safety, and to lessen or avert the threat of a catastrophe in all 254 Texas counties." The Texas Public Utility Commission called for consumers to reduce electricity use through Feb. 16.
"This record cold is not only compelling customers to increase their power usage to stay warm, it's also icing wind turbines and straining our natural-gas powered resources," Commissioner Arthur D'Andrea said in a statement. "With the grid pinched like that, 'demand response' in the form of reduced consumption is an essential shared action."
"Our system is designed to meet summer air conditioning load in the afternoon, and we're just going to have to pay more attention to the winter now," said Joshua Rhodes, a research fellow at the Webber Energy Group at the University of Texas at Austin and a founding partner of IdeaSmiths LLC.
ERCOT issued a news release before 5 pm CT Feb. 15 stating that power had been restored to about 500,000 customers, but it had continued instructions to transmission owners to shed about 14 GW of load, down from 16.5 GW earlier. At that time, poweroutage.us listed about 3.6 million customers as lacking electric service in Texas.
Catastrophic winter storms are not unheard of in Texas. In 2011, natural gas plants went offline as intake pipes for cooling water froze, Rhodes said. But the magnitude of the present outages surpassed that winter's.
"It's just an unprecedented, black swan event " he said, noting the irony of climate change causing warmer Arctic air, which in turn weakens the jet stream, sending blasts of frigid air southward.
SPP's first rolling blackouts
The Southwest Power Pool said Feb. 15 that electricity use exceeded generation in its 14-state balancing authority area. The grid operator declared an emergency alert just after 10 am CT and instructed transmission system operators to reduce demand while utilities determined how to curtail use.
"In our history as a grid operator, this is an unprecedented event and marks the first time SPP has ever had to call for controlled interruptions of service," Lanny Nickell, SPP's executive vice president and chief operating officer, said in a statement. "It's a last resort that we understand puts a burden on our member utilities and the customers they serve, but it's a step we're consciously taking to prevent circumstances from getting worse, which could result in uncontrolled outages of even greater magnitude."
The Midcontinent ISO in a Feb. 15 statement said, "Sustained frigid temperatures and winter weather impacting the Midcontinent Independent System Operator (MISO) South Region contributed to the loss of generation and transmission."
"This led to emergency actions in the region's western portion to avoid a larger power outage on the bulk electric system," the 15-state grid operator said. "Periodic power outages began early Monday morning for some customers in Southeast Texas."
Entergy spokesman Neal Kirby said around 3 pm CT Feb. 15 that about 300,000 of its customers were without power in its service area, which includes parts of Arkansas, Louisiana, Mississippi and Texas.
"In the days ahead, we will examine the root causes of these events and what we can do to prevent them in the future," said Richard Glick, chairman of the Federal Energy Regulatory Commission, in a statement. "But, for now, all our efforts must go toward restoring power during these incredibly challenging times."