Energy Security

TVA Urges Conservation as Cold Snap Sets All-Time Peak Demand Record

The Tennessee Valley Authority (TVA) has urged conservation as it grapples with record-high power demand amid extremely cold temperatures and near-zero wind chill over its seven-state region in the Southeast.

The federal corporation, a major generator that serves as a regional reliability coordinator, on Jan. 16 said “heavy snow and bitterly cold temperatures” were expected to create record high demand. TVA urged its 10 million customers to be aware of their consumption specifically between 6 a.m. and 10 a.m. CST on Wednesday.

As of 9 a.m. on Wednesday, the region marked a preliminary peak power demand of 34,526 MW. Set at a system average temperature of 4F, the figure is now effectively TVA’s all-time demand record—higher even than its record summer peak of 33,482 MW, which was set in Aug. 2007. “Extremely cold temperatures across the region continue to drive up the demand for electricity,” TVA warned, however. “The TVA electric grid is stable, and our generating facilities are performing well,” it said. 

Concerted Winter Readiness in Winter Storm Elliott’s Aftermath

The region has ramped up its extreme cold weather readiness following its load-shedding debacle during Winter Storm Elliott in December 2022. During that storm, which began on Thursday, Dec. 22, 2022, TVA marked its previous winter peak demand record of 33.4 GW on Friday, Dec. 23, 2022, as falling temperatures caused freezing issues at some power plants, resulting in the loss of about 20% of the region’s energy production.

In total, Winter Strom Elliott negatively impacted 38 of TVA’s 232 generating units, mostly due to instrumentation that froze. Outages and failure in the region escalated dramatically, and by 9 a.m. CST on Dec. 23, the region had lost 6,705 MW from coal, combined cycle gas, and independent power producers. 

On Saturday, Dec. 24, 2022, 19% of available TVA-owned and contracted power production remained out of service, and though the balancing authority acquired market power to cover forecasts with contingency, power system cuts in other markets forced the entity to direct local power companies to curtail power consumption, first by 5% and then by 10%. The TVA balancing authority endured nearly eight hours of load shedding, 3 GW at its worst point.

Immediately after Winter Storm Elliott, TVA set about to capture lessons from the debacle. The utility set up a “Blue Ribbon Commission,” a panel of independent experts, charged with a comprehensive review of actions taken before and after the storm. It also convened an “After-Action Technical Team” of internal experts charged with examining its preparation for and response to Winter Storm Elliott. In May 2023, it published a report chronicling its failures.

The efforts identified several opportunities for improvements, including accurate forecasting, coordination and visibility related to gas supply, pressure alignment and troubleshooting, and effective information sharing, both internally across the organization and externally with customers. TVA, notably, has partnerships with 153 local power companies across seven states, and industrial customers which assist the utility with ensuring system reliability. The entity has since set about improving site resiliency, including site-specific improvement plans to address gaps in design basis and redesign its energy market purchases to better communicate market liquidity risks.

The TVA has also had the benefit of a wider, in-depth analysis of Winter Storm Elliott, the fifth major reliability event in the past 11 years in which unplanned cold weather-related generation outages have jeopardized grid reliability. A report issued by the Federal Energy Regulatory Commission (FERC) and North American Electric Reliability Corporation (NERC) as part of their joint inquiry into the devastating December 2022 winter storm suggested incremental unplanned generation outages across the Eastern Interconnection spiked to 90.5 GW—significantly more than the 61.8 GW during Winter Storm Uri in 2021—representing 13% of the U.S. portion of anticipated resources in the Eastern Interconnection.

According to FERC/NERC’s November 2023–issued report, during Winter Storm Elliot, 1,702 individual generating units experienced 3,565 outages, derates, or failures to start. Of these, 825 units—nearly half— were natural gas-fired generators. Mechanical, electrical, freezing, and fuel issues accounted for 96% of the generating unit outages, derates, and failures to start. Nearly 7,500 MW of generation outages across the Eastern Interconnection were linked to gas delivery pressure issues, reflecting the difficulty natural gas pipelines and other distribution points faced in responding to production losses. Another 2,000 MW was linked to transportation constraints.

TVA Invested $123M Over Past Three Months to Ensure Winter Readiness

On Tuesday, TVA said it has so far invested nearly $123 million over the last three months alone to its system and “enhance the reliability and resiliency” at its four coal plants, its 122-unit gas-fired fleet, and its 29 hydropower plants. In addition, “Over the last several months, nearly 3,400 winter readiness activities were conducted across the Power Operations fleet. We’ve completed a majority of the activities with the final tasks on track for completion in January 2024 with the conclusion of the Ackerman Combined Cycle Plant maintenance outage,” it said

To address instrumentation freezing and other power plant freezing impacts, TVA has also “added and/or upgraded insulation, built enclosures around exposed and vulnerable equipment, and modernized heat trace technology, including installation of heated electrical cabling along pipes that prevents both the liquid inside and the critical instrumentation used to monitor the system from freezing,” it noted.

“In addition, TVA is in the process of installing state-of-the-art smart heat trace monitoring systems which send real-time readings to our control rooms, allowing operators to be more responsive to indications of potential freezing issues.” Finally, it conducted drills and tabletop exercises to prepare for any extreme weather in the upcoming winter season, it said.

TVA on Tuesday added that it is “confident” that its plan to improve its generation’s ability to “meet or exceed” NERC’s recently proposed extreme weather requirements. “As improvements are made, it is TVA’s intention for the entire fleet to be able to operate in extreme weather conditions of up to –20F with 20 mile-per-hour winds for at least 48 hours.”

While more improvements are expected over the coming five years, TVA’s current fleet is functioning with lessons incorporated after Winter Storm Elliott. TVA also noted it has added about 1.5 GW of new gas-fired generation over the past year.

These include three combustion turbine units, a combined 750 MW, at the Colbert Combustion Turbine site in North Alabama. In December 2023, it added another 750 MW with three new units at the Paradise Combined Cycle plant near Drakesboro, Kentucky. The new units were “built to the latest standards to ensure reliable operation during extreme weather,” TVA said. 

More units are slated to come online over the next few years. TVA plans to add 500 MW of peaking aeroderivative combustion turbines at Johnsonville in late 2024, 1,500 MW of combined cycle gas power at Cumberland in late 2026, and 300 MW of solar at Lawrence County and Shawnee by late 2028.

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

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