** FILE ** The Tennessee Valley Authority's Cumberland Fossil Plant near Clarksville, Tenn., is shown in this 2002 file photo. (AP Photo/TVA, Ron Schmitt)

The Tennessee Valley Authority is proposing to replace its biggest coal plant, at least in part, with natural gas generation to both cut its carbon emissions and operating costs while maintaining reliable electric service.

But environmental groups and TVA's biggest long-term customer claim the federal utility could do more to save money and the environment by abandoning any fossil fuels in favor of renewable generation, power storage and energy efficiency programs.

The latest power battle for TVA focused last week on the environmental review TVA is completing this summer for the future of the Cumberland Fossil Plant. After 54 years of operation as TVA's biggest coal plant, the twin-unit Cumberland Plant on Lake Barkley is nearing the end of its useful life. To replace part of the 2,470 megawatts of power generation from the aging plant, TVA is conducting an environmental impact study and in April utility officials said the preferred option was to build a 1,450-megawatt combined-cycle, natural gas-powered plant on the Cumberland site.

The gas plant is projected to cut carbon emissions to less than a fourth of what the current coal plant emits and the study said it would be "beneficial" for the environment and reliability of power service. TVA's environmental review said a new gas plant would allow for the future integration of 10,000 megawatts of solar generation that TVA plans to install by 2035 and help accelerate the retirement of the Cumberland coal-fired units.

But a new gas plant would require the construction of a 32-mile pipeline and would continue at least some carbon emissions into the atmosphere. Such greenhouse gases have been linked with global climate change by environmental scientists.

A study commissioned by the Sierra Club calculates that TVA could get cheaper and cleaner generation by a mix of solar, wind, battery storage and energy conservation measures. The Sierra Club retained Synapse Energy Economics, Inc. to model TVA's system and the study found that a clean portfolio approach would save TVA $3 billion more over the next two decades than building new gas generation to replace part of the Cumberland coal plant.

The 32-page economic analysis said building gas to replace coal is "risky" since declining costs for renewable energy generation and power storage and higher natural gas prices are likely to make gas plants uneconomical and unnecessary in the future.

"Any new gas-fired capacity constructed in the next decade is likely to result in stranded assets in which a generator with remaining depreciable life has been rendered uneconomic to consumers," the Synapse Energy study concluded. "This finding supports resource planning that procures solar, wind, storage and energy efficiency as early as possible in the 2020s."

The study said for TVA to achieve White House targets to build a carbon-free electric system by 2035, the federal utility needs "to move decisively to retire existing coal, minimize reliance on new gas and commit to increased volumes of renewables, storage and demand-side resources."

"Synapse, a well-respected energy analysis firm, finds what we have long believed – TVA can quickly shift coal plants to renewable energy to more fully meet its charter for environmental stewardship and affordable energy for the Tennessee Valley." Amy Kelly of the Sierra Club's Beyond Coal campaign, said in a summary of the new study.


TVA received final public comments last week on the future of its Cumberland Fossil Plant. TVA's preliminary finding was that some natural gas generation is needed on the site to help ensure power delivery when the sun doesn't shine, the wind doesn't blow or other TVA power plants may be idled by weather, refueling or equipment challenges.

To meet wintertime peak demands on frigid winter mornings before the sun comes up and solar generation begin requires power production that can be quickly put on the grid. TVA is planning to add more battery and potentially more hydro pumped storage generation, but those are not yet as cost-effective as combined cycle gas plants, according to TVA President Jeff Lyash.

"We are driving toward a cleaner system, but we are being very mindful not to sacrifice power reliability or resilience," Lyash said in an interview with the Times Free Press earlier this year. "It's in all of our best interests to remember that in addition to being clean, the system has to be affordable, reliable and resilient. If you sacrifice anyone of those, it is not a sustainable solution."

For more than two decades, TVA has delivered its power more than 99.999 percent of the time, avoiding major power outages like those that left 4.5 million people without power last year during a winter storm in Texas or the Northeast and Midwest blackout in 2003 that cut off electricity to 50 million Americans.

TVA currently generates about 26% of its power from natural gas plants, but most of TVA's power now comes from relatively carbon-free nuclear power, hydroelectric dams and solar farms.


Environmental groups and others argue that with more energy efficiency programs, time-of-day pricing plans and investments in power storage facilities, TVA can shift to a carbon-free portfolio without sacrificing reliability.

"A diverse and customer-focused clean energy system is a win-win-win," Maggie Shober, research director at the Southern Alliance for Clean Energy, said in a statement submitted to TVA about Cumberland's future. "It lowers customer bills, reduces pollution and greenhouse gas emissions, and improves resilience in the face of extreme weather. TVA must adopt a clean energy portfolio to replace Cumberland rather than lock customers into continued volatile fossil fuels."

Shober said TVA has the second-highest planned gas development of all major utilities with 4 gigawatts of new gas capacity planned by 2030.

"TVA is being horrifically irresponsible," Sudeep Ghantasala with the Sunrise Movement Nashville chapter said in an announcement of the group's opposition to TVA's plans for more natural gas generation. "The permitting process for the gas pipeline started months ago. TVA claims this was to speed up the process should they pick the gas combined cycle plant. Why haven't they started the same process for the solar alternative, and better yet, looked at distributed solar, energy efficiency, and demand response which could come on board sooner and even reduce demand for large-scale projects?"

Robin Brandon, a retired shift operations manager at TVA who is now mayor of Stewart County where the Cumberland Fossil Plant is located, said he thinks most local residents understand that the 54-year-old coal plant is nearing the end of its useful life and will eventually be shut down.

"We are concerned about the job losses the shutdown of Cumberland will bring, but we understand that natural gas will likely continue generation there, keeping some jobs and our TVA tax equivalent payments," Brandon said in a telephone interview.

But earlier this month, TVA's biggest long-term customer, Nashville Electric Service, and Nashville Mayor John Cooper sent letters and resolutions to TVA urging the federal utility to pursue renewable fuels rather than natural gas to replace the power generated by the Cumberland Fossil Plant when the coal facility is shut down.

"Any plan that would establish a new gas pipeline or conscript Nashville into decades of carbon polluting methane is unacceptable," Cooper wrote in the letter to TVA. "The city of Nashville calls on TVA to serve as a leader in addressing the existential threat of climate change."

Contact Dave Flessner at or at 423-757-6340. Follow on Twitter at @dflessner1