As of September 2010, the Tennessee Valley Authority had 14,573 MW (summer net) of coal-fired generation, which will be reduced to 9,098 MW (summer net) after a series of past and future shutdowns are completed that are being caused by clean-air needs.
“TVA is planning to balance its coal-fired generation with lower-cost and cleaner energy generation technologies,” the federal utility said in its Nov. 18 annual Form 10-K report. “TVA’s long-range plans will continue to attempt to balance the costs and benefits of significant environmental investments at its remaining coal-fired plants that do not have scrubbers and/or [selective catalytic reduction (SCR)]. TVA expects to decide whether to control, convert, or retire its remaining coal-fired capacity on a unit-by-unit schedule.”
Transmission upgrades may be required to maintain reliability when some coal units are shut. TVA said it invested $130m in such upgrades between 2011 and 2013, and estimates future expenditures for transmission upgrades to accommodate inactive coal units to be about $350m for the 2014-2020 period. Upgrades may include enhancements to existing lines and substations or new installations as necessary to provide adequate power transmission capacity, maintain voltage support, and ensure generating plant and transmission system stability.
TVA considers units to be in an active state when the unit is generating, available for service, or is temporarily unavailable due to equipment failures, inspections, or repairs. As of Sept. 30, 2013, which was the end of its latest fiscal year, TVA had 10 coal-fired plants consisting of 46 active units, accounting for 12,901 MW of summer net capability. As of Sept. 30, 2013, TVA had 14 inactive units. Inactive units may be in three categories: retired, mothballed, or inactive reserve.
- Retired units are unavailable for service and are not expected to return to service in the future. TVA currently has four retired coal units: John Sevier Units 1 and 2 and Widows Creek Units 3 and 5.
- Mothballed units are unavailable for service but can be brought back into service after some maintenance with an appropriate amount of notification, typically weeks or months. As of Sept. 30, 2013, TVA had nine mothballed coal units: Shawnee Unit 10, Johnsonville Units 7 and 8, Widows Creek Units 1, 2, 4, and 6, and John Sevier Units 3 and 4.
- Inactive reserve units are unavailable for service but can be brought back into service after some repairs in a relatively short time, typically days. As of Sept. 30, 2013, TVA had one unit in inactive reserve: Colbert Unit 5. On Oct. 1, 2013, four additional units were mothballed — Johnsonville Units 5, 6, 9, and 10 — and the status of Colbert Unit 5 was changed from inactive reserve to mothballed.
Under agreements with the U.S. EPA, several nearby states and certain environmental groups, TVA must retire certain units, with this being the status of those actions:
- John Sevier (two affected units in this category), agreement is to retire both units no later than the end of 2012, with those retirements having taken place;
- Johnsonville (ten affected units), retire six units by end of 2015 and four more by the end of 2017, with the actual retirements to occur by those deadlines, and with six of the affected units already idled in 2012 and 2013;
- Widows Creek (six affected units), agreement is to retire two of Units 1-6 by end of July 2013, retire two more by the end of July 2014, and the last two of this group of six units by the end of July 2015. Units 7 and 8 have scrubbers and SCR and aren’t part of this retirement scenario. TVA idled Units 1-6 in October 2011 and retired Units 3 and 5 in July 2013.
Other actions that TVA is required under the agreements to take are:
- Allen (three affected units in this category, all equipped with SCRs), install scrubbers or retire by the end of 2018, with TVA still evaluating what it will do;
- Bull Run (one affected unit, equipped with scrubber and SCR), agreement and plan is to continuously operate emissions control equipment;
- Colbert (five affected units, with SCR on Unit 5), agreement to shut, add emissions controls or convert to biomass Units 1-4 by the end of June 2016 and Unit 5 by end of 2015. TVA idled Unit 5 in October of this year, and will retire Units 1-5 no later than the end of June 2016.
- Cumberland (two affected units, both with SCR and scrubbers), agreement and current plan is to continuously operate the emissions control equipment.
- Gallatin (four affected units), add emissions controls, convert to biomass or retire all four units by the end of 2017. Plan is to add scrubbers and SCR on all four units by the end of 2017.
- John Sevier (two affected units), remove these units from service by the end of 2012 and add emissions controls, convert to biomass or retire them by the end of 2015. Idled Units 3 and 4 in December 2012 and plans are to retire them by the end of 2015.
- Kingston (nine affected units, with scrubbers and SCRs on all nine), agreement and current plan is to continuously operate emissions control equipment.
- Paradise (three affected units, with scrubbers and SCR on all three), agreement was to upgrade scrubbers on Units 1 and 2 by end of 2013 and then to continuously operate all emissions equipment. Units 1 and 2 scrubbers were actually upgraded in 2012, but the TVA board recently approved a plan to shut both of those units at the still-unfixed point in time when a new gas-fired power plant at the site is completed. The larger, newer Unit 3 would keep operating.
- Shawnee (two affected units), control, retire or convert to biomass Units 1 and 4 by the end of 2017. Still evaluating what to do with those units. Did idle Shawnee Unit 10 in October 2010.
- Widows Creek (two affected units, with scrubbers and SCR on both), agreement was to continuously operate this emissions control equipment on Units 7 and 8. TVA plans to do so, with plans at an unspecified time to retire Unit 8.