Utilities across the country are looking to develop natural gas generation projects at existing coal plant sites, with the advantage of existing infrastructure at those sites being among the key selling points for utilities.
On June 10, investor-owned Ameren Missouri said that it filed an application with the Missouri Public Service Commission to build an 800-megawatt simple-cycle natural gas energy center. The Castle Bluff Energy Center “is designed to bolster grid reliability and would be used to deliver energy on the hottest summer days, the coldest winter nights, and complement the increasing amount of renewable energy generation being added to the grid.”
The utility said the identified site already has existing infrastructure and transmission line access, reducing overall construction time and cost to customers.
The site previously hosted similar on-demand generation as part of the Meramec Energy Center, a coal-fired plant retired in 2022.
With timely regulatory approval, construction is scheduled to begin in 2026, with the energy center expected to be ready to serve customers in 2027.
TVA
Meanwhile, the Tennessee Valley Authority on April 2 said it had made the decision to retire its Kingston Fossil Plant and build a state-of-the-art energy complex at the site by the end of 2027.
TVA will retire the nine coal-fired units at Kingston by the end of 2027. To replace that generation, TVA will build an energy complex that will house at least 1,500 megawatts of combined cycle and dual-fuel Aeroderivative natural gas combustion turbines with 100 megawatts of battery storage and up to 4 megawatts of solar generation at the Kingston location.
This will be a first-of-its-kind facility at TVA. The natural gas generation will be in operation prior to Kingston Fossil Plant retirement to maintain reliable, uninterrupted power to customers.
Also in April, TVA celebrated the dedication of new state-of-the-art natural gas units at the Paradise Combustion Turbine Plant in Kentucky.
TVA’s Paradise Fossil Plant was located in western Kentucky on the Green River near the village of Paradise. The plant had three units and three large natural-draft cooling towers. Paradise was TVA’s only coal-fired plant with cooling towers.
Units 1 and 2 went online in 1963, each with a generation capacity of 704 megawatts. At the time, they were the largest operating units in the world. A third unit became operational in 1970, with a summer net generating capacity of 971 MW.
Paradise units 1 and 2 were retired in 2017. After a detailed review of fuel, transmission, economic and environmental impacts, as well as reviewing public input, on Feb. 14, 2019, the TVA Board of Directors approved the retirement of Paradise Unit 3, which ceased operation in February 2020, effectively closing the plant.
TVA invested approximately $1 billion to build a gas-fired plant to replace Paradise units 1 and 2. The new combined cycle plant was opened in April 2017.
Santee Cooper
South Carolina’s Santee Cooper has identified a need for additional generation, including additional natural gas generation to provide reliability “and help us integrate a significant amount of new solar also in our plans,” Mollie Gore, Director of Corporate Communications and External Affairs at Santee Cooper, told Public Power Current.
“Our needs align with those of Dominion Energy SC, and we are discussing the possibility of jointly building a new NGCC unit on the site of a former Dominion coal plant.”
As a state-owned utility, Santee Cooper would need legislative authority to pursue such a joint build, “and we are pursuing that authority,” she noted.
“We are very early in this process, which would require all the normal regulatory approvals and processes if we are able to move forward. Our IRP calls for new natural gas generation in the early 2030s,” Gore said.
In 2022, public power utility Colorado Springs Utilities shuttered its Martin Drake coal-fired power plant.
Six modular natural gas generation units -- located adjacent to the Martin Drake plant site -- were commissioned into service on May 30, 2023.
The 157-MW modular units serve as replacement, peak-demand generation while the utility builds a new transmission line and conducts other upgrades to its electric grid, it noted on its website.
The generators are dual-fuel capable with natural gas as the primary fuel and diesel fuel for backup.
Wisconsin Utilities Eye Gas Plants at Coal plant Sites
Investor-owned utilities in Wisconsin are also planning to build gas-fired generation at coal plant sites in the state.
In May, Alliant Energy announced plans for filing a request to convert its coal-fueled Edgewater Generating Station to natural gas.
Transitioning Edgewater from coal to natural gas, in part, takes into consideration the complexities of the Midcontinent Independent System Operator’s newly advanced seasonal construct and TC Energy’s announced plans to upgrade and extend its gas pipeline in parts of Wisconsin, including the Sheboygan area, where the Edgewater Generating Station is located, providing a unique opportunity to convert the facility, the utility said.
By operating Edgewater past 2025, the facility retains more than 350 MW of capacity.
Additionally, the project will avoid an estimated $60 million in customer costs through 2030, it said.
The conversion of Edgewater Generating Station from coal to natural gas generation is projected to take place during 2028 after receiving the necessary regulatory approvals. Once converted, the company expects to operate Edgewater to complement its renewable fleet.
In a February filing made at the Wisconsin Public Service Commission, Wisconsin Electric Power Company and Wisconsin Public Service Corporation, units of WE Energies, said they would seek:
- Certificates of Public Convenience and Necessity for two new natural gas generation projects in the near future: an approximate 130 MW RICE facility located near the existing Paris Generating Station with an anticipated commercial operation date by summer 2026; and
- The construction of simple-cycle natural gas combustion turbine units totaling approximately 1,100 to 1,200 MW at the Oak Creek Power Plant campus with anticipated commercial operation dates for the units occurring from fall 2027 through June 2028.
These are in addition to the future planned addition of 100% gas capability at the Elm Road Generating Station and Weston Unit 4, which is coal-fired.
The Oak Creek generating site is comprised of two power plants: Oak Creek Power Plant and Elm Road Generating Station. The Oak Creek Power Plant is a coal-based, baseload plant. The Elm Road units are supercritical coal-based, baseload units.
Texas
Texas is also seeing plans announced to develop natural gas-fired generation at coal plant sites in the state.
Independent power producer Vistra Corp. in May announced its intention to add up to 2,000 MW of dispatchable, natural-gas-fueled power capacity in West, Central, and North Texas.
Vistra noted that its coal-fired Coleto Creek Power Plant near Goliad is set to retire in 2027 to comply with federal Environmental Protection Agency rules. The company intends to repower it as a gas-fueled plant, enabling up to 600 MW of additional capacity after the coal facility retires.
In February, Sandow Lakes Energy Company announced its plans to pursue the construction of a 1,200-MW, ultra-efficient, natural gas-fueled power plant.
The plant, located on Sandow Lakes property in Lee County, Texas, will be developed and owned by a Sandow Lakes Energy Company, LLC, subsidiary and will operate within the Electric Reliability Corporation of Texas.
Sandow Lakes was formerly the site of a 1950s-era integrated industrial enterprise with 1,200-MW of coal-based power generation.
The legacy coal facilities and industrial facilities are in the process of being partially demolished and repurposed, paving the way for the more contemporary and progressive combined cycle power plant, Sandow Lakes Energy said in February.
Construction is expected to begin in 2025, with the plant generating power by 2028.
North Carolina
In North Carolina, investor-owned Duke Energy Carolinas in March filed an application with state utility regulators for a Certificate of Public Convenience and Necessity to construct and operate two advanced-class, simple-cycle gas combustion turbine units that will be approximately 425 megawatts each, for the generation of electricity at the site of its existing Marshall Steam Station in Catawba County, North Carolina.
Siting the Proposed Facility at Marshall helps to accomplish a goal of repurposing infrastructure at existing power stations as Duke Energy continues to meet load growth and transition towards carbon neutrality by 2050. The CT units will be able to efficiently utilize significant portions of existing plant infrastructure currently supporting Marshall coal-fired Units 1 and 2, the filing said.
EIA Details Trend of Converting Coal Plants to Gas Plants
In 2020, the Energy Information Administration reported that 121 U.S. coal-fired power plants were repurposed to burn other types of fuels between 2011 and 2019, 103 of which were converted to or replaced by natural gas-fired plants.
At the end of 2010, 316.8 gigawatts of coal-fired capacity existed in the United States, but by the end of 2019, 49.2 GW of that amount was retired, 14.3 GW had the boiler converted to burn natural gas, and 15.3 GW was replaced with natural gas combined cycle. “The decision for plants to switch from coal to natural gas was driven by stricter emission standards, low natural gas prices, and more efficient new natural gas turbine technology,” EIA said.
Two different methods are used to switch coal-fired plants to natural gas, EIA said at the time. The first method is to retire the coal-fired plant and replace it with a new natural gas-fired combined-cycle (NGCC) plant. The second method is to convert the boiler of a coal-fired steam plant to burn other types of fuel, such as natural gas.
