The Tennessee Valley Authority board of directors voted to retire the remaining 1,150 megawatt (MW) coal-fired unit at its Paradise Fossil Plant in Muhlenberg County, Kentucky, by December 2020.

It also voted to close the 881 MW Bull Run station, the only single-generator, coal-fired power plant in the TVA system. Bull Run opened in 1967.

TVA earlier had said that with less need for base load electric generating resources, power plants that have relatively high projected future maintenance cost and environmental compliance expenditures, high forced outage rates and a "poor generation portfolio fit" were the focus of more detailed study for potential retirement. It said that its Paradise Unit 3 fell into that category of assets.

Declining coal use

In early December, the Energy Department (DOE) said that coal consumption in the U.S. was on track to fall to 691 million short tons (MMst), a 4% decline from 2017 and the lowest level since 1979.

U.S. coal consumption has been falling since its peak in 2007. DOE forecasts that 2018 coal consumption will be 437 MMst (44%) lower than 2007 levels, mainly driven by declines in coal use in the electric power sector.

The electric power sector is the nation’s largest consumer of coal, accounting for 93% of total U.S. coal consumption between 2007 and 2018. The decline in coal consumption since 2007 is the result of both the retirements of coal-fired power plants and decreases in the capacity factors, or utilization, of coal plants as increased competition from natural gas and renewable sources have reduced coal’s market share.

Trouble in Paradise

TVA's Paradise generating station currently has one operating unit. Units 1 and 2 entered service in 1963 and were replaced with natural gas generation in the spring of 2017. Unit 3 entered service in 1970. In 1985, a barge-unloading facility was added so that coal could be delivered by barge as well as by train and truck.

In late 2018, TVA prepared an environmental assessment of the site-specific impacts of the potential retirement of Paradise Unit 3. On Feb. 11, TVA issued its Finding of No Significant Impact on the potential retirement.

The natural gas plant at the Paradise site consists of three trains each with a GE 7FA.05 gas turbine-generator and a Vogt heat recovery steam generator (HRSG). Each HRSG is equipped with natural-gas supplemental duct firing. The steam generated from the HRSGs provides steam to a Toshiba steam turbine/generator.

Plant design allows for simple cycle operation with a summer capacity of 600 MW, or combined cycle operation with a baseload capacity of 1,025 MW and additional supplemental duct-firing operation of 1,130 MW.

The Paradise Combined Cycle Plant can operate in 1x1, 2x1, or 3x1 mode or operate in simple cycle mode as needed. The flexibility is intended to help accommodate increasing amounts of renewable energy resources.