Tennessee Valley Authority lost power to 38 of its 232 generating units due to Winter Storm Elliott, mostly due to instrumentation that froze.

TVA released an after-action report detailing its actions during and since the December storm, which brought frigid temperatures, high winds and heavy rain to the Tennessee Valley and other parts of the U.S.

Record-shattering demand for electricity forced TVA to impose rolling blackouts for the first time in its history. The nation’s largest public utility said it anticipated and prepared for Elliott, but the “storm’s speed and intensity exceeded forecasts and TVA’s efforts.”

According to the after-action report, in the early morning on Friday, Dec. 23, temperatures in the Tennessee Valley region fell rapidly, resulting in a significant increase in projected demand.

At the same time, the rapid drop in temperatures and other weather-related conditions caused freezing issues at some generators, resulting in the loss of some 20% of TVA’s available energy production. TVA said it needed about 17% more power than was available.

TVA employees worked to keep generating units online and restore unit outages during the storm. This included placing additional temporary structures, insulation, and heaters around equipment at impacted units. The federal utility said 14 of the 38 generating units lost were recovered and returned to service within 48 hours.

TVA’s nuclear and hydro assets were not affected by the extreme weather and operated without issue, according to the report.

TVA said the utility has completed more than 250 actions post-Elliott.

These include strengthening and increasing the operational resilience at TVA’s generating facilities, placing more robust enclosures at generating facilities, and enhancing insulation around instrumentation.

The after-action report also says TVA is developing design modification plans for impacted generating units – to address both winter and summer peaks.

TVA estimated facing a total financial impact of approximately $170 million from Winter Storm Elliott, including increased fuel and purchased power costs, asset repair and hardening and lost revenues.

Read TVA’s after-action report here

The utility’s generation mix in 2022 was made up of nuclear (39%), gas (33%), coal (15%) and hydro (9%). Wind and solar consist of approximately 4%.

TVA is currently building about 3,800 MW of new generation capacity, including natural gas, solar and energy storage.

In June 2022, TVA issued a 5,000 MW request for clean energy. The utility anticipates starting to award bids for approximately 6,000 MW of solar and storage within the next couple of months, which could double the amount of solar energy on TVA’s system.

TVA’s goal is to add 10,000 MW of solar by 2035. 

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