The state grid passed its latest test this week when an arctic freeze blasted Texas and, once the sun rose, a record amount of solar power helped keep the heat on through the season’s coldest days so far.
The amount of solar Tuesday was more than three times what was available during the deep freeze of February 2021, when a near failure of the grid operated by the Electric Reliability Council of Texas (ERCOT) led to mass outages and the deaths of 246 Texans. And before the sun started shining, another key change played a role: The state’s coal and gas plants suffered only about half the amount of outages they had during the last statewide deep freeze in December 2022. That kept Texans’ power on during the peak demand period from 7 a.m. to 8 a.m.
“It’s a pretty significant data point that phase-two weatherization is working,” Doug Lewin, an energy analyst with Austin-based Stoic Energy Consulting, said of work done since 2021 to keep the state’s traditional power plants operating. “But it’s not like, ‘Great, we’re done. Everything is fine.’”
This week’s success — which came with back-to-back requests for Texans to turn down their thermostats and shut off major appliances to help make ends meet — doesn’t mean the grid could necessarily stand up to another Winter Storm Uri. And this winter could still bring more challenging tests. ERCOT’s own analysis shows a deep freeze this month still brings a 20.6 percent chance of a grid emergency that could lead to blackouts. Such weather in February brings an 11.4 percent chance of emergency conditions.
Still, Lewin says, there’s been progress, especially in terms of weatherproofing plants. About 7,000 megawatts of generating capacity from coal- and gas-powered plants was out of action when energy use peaked Tuesday morning at about 78,000 megawatts. In similar conditions during Winter Storm Elliott on Dec. 23, 2022, coal and gas plant outages took 14,000 megawatts of capacity off the grid.
Under the guidance of the Public Utility Commission (PUC) in the aftermath of the 2021 winter storm, ERCOT increased plant inspections to ensure generating plants wouldn’t again fall to the cold.
New criteria went into action last month — as a second phase to the plan — to further weatherproof power plants ahead of this winter.
ERCOT also told generators what level of average windchill temperatures their plants must be prepared to operate through for a 72-hour period based on their region’s weather patterns. In South Texas, that temperature average is 16.3 degrees; in South Central Texas it’s 8.4 degrees; in the Rio Grande Valley, it drops to -20 degrees.
At one point during 2021’s Winter Storm Uri, more than half the state’s natural gas supply was shut down because cold temperatures froze equipment amid power outages. Because the grid was in such disarray, the exact total of demand during that storm is unknown, but estimates range from 77,000 to 87,000 megawatts.
It takes about one megawatt to power 200 Texas homes on an unusually hot or cold day.
ERCOT’s reserves of power stayed well above emergency levels through Monday and Tuesday, but both days’ forecasted demands were roughly 10,000 megawatts higher than what the grid operator actually faced. Though Wednesday’s morning power demand neared record levels, capacity remained well above what was needed.
ERCOT still has to do a better job forecasting demand, Lewin said.
“There is a lack of understanding of homes and buildings and how they do in the cold,” he said, referring to the millions of homes in the state that are poorly insulated and have back-up heating systems that suck up more power. “They need energy-efficiency experts.”
The state also continues to deal with overcrowded transmission lines — such as the line that spawned issues and a grid emergency in September.
As a result, power gets stranded in portions of the state because it cannot make it across or it is curtailed away to avoid emergency. Experts say to think of power transmission lines as a highway. Too many electrons crowding the pathway could lead to an accident.
Cheaper power — often wind, but also natural gas and other sources — gets stranded in South Texas where it’s plentiful but unable to move across to areas that have the demand.
CPS Energy and other utilities have plans approved by the PUC to build up transmission to ease the issue, but that construction will take several years.
CPS Energy, San Antonio’s city-owned utility, reported its own preliminary winter demand record of 5,374 megawatts Tuesday morning. The utility said its customers’ conservation efforts also contributed to grid reliability through this week’s tightest periods.
“Your conservation efforts, along with additional grid reliability tools, helped us get through record-breaking peak times,” ERCOT said in a statement Tuesday.
Wind power also played a bigger role this week. Overnight Monday to Tuesday, the spinning turbines kept power supply high and power prices relatively low.
Also, a little more than 1,000 megawatts of battery power was deployed onto the grid Monday and Tuesday as Texans were hitting the snooze buttons on their alarm clocks.
On Wednesday, San Antonio-based OCI Solar Power reported sunny weather allowed its solar farms to be deploying near full capacity. A little after 10 a.m., Texans were using about 9,100 megawatts of solar energy to help power their homes through the dregs of the cold snap.
Solar and battery systems continue to lead in the amount of new generation coming onto ERCOT’s grid, helping to keep up with booming demand from increasingly severe weather and the state’s growth. That makes today’s grid far more diverse than the one that failed Texans in 2021.
And solar, despite not being available at all times, continues to be a lifeline year-round in Texas — and is growing rapidly. As of Sept. 30, ERCOT said it had nearly 18,400 megawatts of solar capacity, topping California for the first time as the nation’s leader in such generation. On Tuesday afternoon, 14,800 megawatts of that power was online.
“Solar is really a release valve,” Lewin said. “It takes a lot of pressure off thermal power plants if they’re having problems and to get ready for the evening.”
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