Winter Freeze Testing Texas Power Grid Reforms

Parts of Texas have suffered localized, distribution-level power outages as an Arctic outbreak sent temperatures plummeting across the state, but its heavily scrutinized grid is largely prepared to weather the storm, state entities said.

Frigid temperatures stemming from a large dome of Arctic high pressure are sending temperatures into the single digits and below zero throughout the Great Plains, with some short-lived cold temperature anomalies “Deep in the Heart of Texas.” But anxiety about the storm’s effect on the power grid has ramped up, given the historic, deadly power crisis that overwhelmed Texas and the south-central U.S. during Winter Storm Uri a year ago. Winter Storm Uri’s unprecedented reach prompted an average 34,000 MW of unplanned generation losses across the Electric Reliability Council of Texas (ERCOT) grid for more than two consecutive days, from Feb. 15, 2021, to Feb. 17, 2021. The generation losses were equivalent to nearly half of ERCOT’s all-time winter peak electric load of 69,871 MW. The Southwest Power Pool and the Midcontinent Independent System Operator also suffered widespread generator outages.

ERCOT on Feb. 2, 2022, issued a winter watch effective through Sunday, Feb. 6, forecasting high energy demand for the duration of the winter weather. However,  it suggested it has about 2.3 GW of additional capacity to address tight grid conditions and was ready to issue conservation notices to reduce demand as needed. The grid operator said that as part of preparations for the extreme weather, it issued an operating condition notice for the potential for extreme weather conditions on Jan. 28. On Feb. 2, it also called on the Texas Commission on Environmental Quality (TCEQ) to exercise its enforcement discretion with respect to generator exceedances of TCEQ air permit limitations to maximize generation availability until Feb. 6.

ERCOT’s November-issued 2021-2022 winter seasonal assessment of resource adequacy projected peak demand would be 62,001 MW based on average weather conditions, and a high winter peak load of 72,772 MW based on 2011 weather and an August 2020 economic forecast. Nearly 85,000 MW of resource capacity is expected to be available for the winter peak, it said. At 8 a.m. on Friday morning (Feb. 4)—at the peak of the day-ahead forecast and with temperatures hovering just above 25F in Houston—ERCOT was serving 68,325 MW of demand. Operating reserves were at 6.4 GW, and 82,511 MW of capacity had been committed.

An Exhaustive List of Checks

Since last year’s winter storm debacle, and under considerable scrutiny from state regulators, ERCOT has cleared a lengthy list of legislative mandates to boost reliability. Along with proposing new market rules requiring generators to report all forced outages and provide operational updates more frequently, it has revised market processes to continuously run planning assessments needed to bring resources back online when grid conditions are tight. It says its assessments of extreme low-probability, high-impact weather scenarios—including temperatures, durations, precipitation, humidity, and wind—have also improved. So far, it has also proposed updated methodologies for its Seasonal Assessment of Resource Adequacy (SARA) and other resource adequacy studies.

In addition, it has added short-term solar forecasts into existing models as solar power expands in Texas, and it is working to identify periods of high variability. And, along with completing an evaluation that required inverter-based resources to provide additional reliability attributes—such as grid-forming capability—it said it has reviewed the reliability of the current and projected resource mix, as well as evaluated market changes to incentivize sufficient dispatchable resources.

To address winter conditions, and specifically implement extreme weather controls for this winter, ERCOT conducted onsite inspections at 302 generation units during December—representing 85% of the outage-related megawatt-hours lost during Winter Storm Uri last February. All but three facilities, representing 533 MW, showed they had corrected “deficiencies.” All 22 transmission facilities inspected also cleared deficiencies, it said. ERCOT said it has also obtained CEO attestations of weather readiness from “all market participants who own or operate generation resources and/or transmission/distribution power lines,” as required by Texas’s new weatherization mandates.

Still, ERCOT said it is now “taking a more conservative approach” to operating the grid. “ERCOT’s grid management is at its most aggressive since the market was created two decades ago. ERCOT is increasing operational reserves to ensure adequate generation is available to Texas homes and businesses and is bringing more generation online sooner if it is needed to balance supply and demand. The grid operator is also purchasing more reserve power, especially on days when the weather forecast is uncertain,” it said. In addition, ERCOT said it “has assessed the on-site fuel supply for some gas-fired generators,” though it provided few details of how many gas-generators have secured fuel supply.

Planning for Emergencies

In a Feb. 2-released energy emergency alert overview, the grid operator also detailed measures it could take to stabilize the grid if conditions turn for the worse. If operating reserves drop below 3 GW and weren’t expected to recover within 30 minutes, ERCOT plans to bring all available generation online and “release any unused reserves,” it said. It would also immediately deploy emergency response services, including to commercial/small industrial customers, which are contractually paid to curb their power use—a combined 1 GW—within 10 or 30 minutes. Transmission companies were also on standby if voltage reductions of 100 MW to 200 MW were warranted, it said.

In the event operating reserves fell below 2.3 GW, ERCOT said it would declare a level 1 energy emergency alert (EEA) and begin increasing generation supplies and boost demand response. Its plans involve importing 1.2 GW from neighborhood grids, deploying 568 MW of “switchable generation” that can serve multiple grids, and deploying any unused emergency response from commercial and industrial customers. At a level 2 EEA—if reserves fell below 1.7 GW—it would request conservation from the public and deploy 1.7 GW in operating reserves carried by large industrial customers. As a backup, it would deploy load management programs from transmission companies, which constitutes 211 MW for the winter season.

In the event of a level 3 EEA—the most critical level, which foresees an operating reserve drop below 1.4 GW—ERCOT said it would instruct transmission companies to shed load in controlled outages. During Winter Storm Uri, notably, the grid initiated 20 GW in controlled outages, the most of four times it has ever shed load, and far exceeding the 4 GW it shed during the Feb. 2, 2011, cold snap incident.

Tight grid conditions during the winter months may be caused by extreme cold weather combined with windy conditions and/or icing on wind turbine blades, ERCOT explained. Other factors may include gas restrictions and derates/outages at some power plants in North Texas during peak load periods. “During winter, load peaks in the early morning and then again in the early evening. Winter peak demand records generally occur after two to three consecutive days of cold build up in the ERCOT region and are driven largely by a combination of low temperatures across the region’s largest urban load centers,” it said.

“While grid conditions remain strong with enough capacity, our weather forecasts show there is potential for significant frozen precipitation behind this week’s cold front,” said ERCOT Interim CEO Brad Jones on Tuesday. “With frozen precipitation, there is always a chance for local outages caused by things like ice on wires or fallen tree limbs. These local outages are not related to the amount of available electricity generated and put on the grid. Texans should contact their utility in the event they experience a localized outage.”

‘Monumental Reforms’ to Ensure Reliability

The Public Utilities Commission of Texas (PUCT) this week said it was also closely monitoring the state’s energy grid preparedness and reliability, but it suggested current forecasts indicate there will be enough power generation statewide to meet the projected electric demand.

“The grid is ready, and the lights will stay on for Texans,” said PUC Chairman Peter Lake. “Working together with Governor Abbott, the Texas Legislature and ERCOT, we have in place monumental reforms requiring winterization of electric generation and transmission operations and programs that will make more power available more quickly when needed. Also, well before the storm, many generators began securing additional resources to ensure they have the fuel they need to generate electricity regardless of weather conditions.”

During a press conference on Feb. 3, Texas Gov. Greg Abbott said the Texas power grid “is fully functioning and continues to be reliable.” The governor said there was “plenty of power available, and even at expected peak demand there should still be over 10,000 MWs of extra power capacity—enough extra power to supply about two million homes.” The Railroad Commission of Texas has also “suspended all scheduled maintenance of natural gas resources out of an abundance of caution, and all pipelines are fully functioning,” the governor’s office said.

—Sonal Patel is a POWER senior associate editor (@sonalcpatel, @POWERmagazine).