Coal-Fired Mill Creek Generating Station Readies for New 7HA.03 Gas-Fired Unit

Louisville Gas and Electric Co. and Kentucky Utilities Co. (LG&E and KU) will replace two aging coal generation units at Mill Creek Generating Station in Kentucky—a combined 600 MW—with a 645-MW GE Vernova hydrogen-ready 7HA.03 gas turbine.

GE Vernova announced the order for the heavy-duty gas turbine—the most advanced of its HA-class models—from the two regulated PPL Corp. subsidiaries on April 11. The new natural gas combined cycle plant, Mill Creek Unit 5, will be built at the Louisville site by TIC (The Industrial Company), a subsidiary of engineering and construction giant Kiewit.

A Diversification Driven by Environmental Rules

According to LG&E and KU, the new unit is part of a least-cost plan to modernize their 8-GW fleet. The utilities currently operate 11 coal units with a total net summer capacity of 4,867 MW, a 662-MW natural gas combined cycle unit, and 17 load-following simple cycle combustion turbine (SCCT) peaking units with a combined capacity of 2 GW.

In 2022, the utilities, however, moved to retire four of their 11 coal units: the 300-MW Mill Creek 1 in 2024 and the 300-MW Mill Creek 2 in 2024; the 412-MW Brown 3 in 2028, and the 485-MW Ghent 2 in 2028.

The utilities proposed to retire Brown 3 owing to $26 million in major maintenance the unit would need in 2027. Meanwhile, they said Mill Creek 1, Mill Creek 2, and Ghent 2 are not currently equipped with SCR, and it was economical to retire Mill Creek 2 and Ghent 2 rather than outfitting them with selective catalytic reduction (SCR) controls as required by the Environmental Protection Agency’s (EPA’s) Good Neighbor Plan. The utilities also moved to retire Mill Creek 1 in 2024, given that the unit would require a cooling tower under the EPA’s Effluent Limitations Guidelines and Standards (ELGs) and require the addition of an SCR due to the Good Neighbor Plan. The utilities, in addition, moved to retire three of their 17 gas SCCT units, along with three small natural gas-fired units—Haefling 1 and 2, and Paddy’s Run 12—a combined capacity of 47 MW.

To replace that capacity, LG&E and KU in January 2023 filed a joint application asking the Kentucky Public Service Commission (KPSC) to approve certificates of public convenience and necessity (CPCN) to build two natural gas combined cycle units (Mill Creek 5 and Brown 12). It also moved to build a solar generation facility, acquire another one, and construct a battery storage facility.

In March 2023, however, Kentucky enacted a law that requires jurisdictional utilities to get approval from the KPSC before retiring an electric generating unit. In an order issued on November 2023, the KPSC allowed LG&E and KU to retire Mill Creek 1 and 2, but it conditioned Mill Creek 2’s retirement on the operation start of Mill Creek 5 by 2027. It also approved the utilities’ request to retire the three SCCTs.

However, the commission denied the utilities’ request to retire Ghent 2 and Brown 3, citing the need for additional clarity surrounding the EPA’s environmental rules. It also denied a CPCN for Brown 12, finding no need to construct the second combined cycle plant, given its denial of the Ghent 2 and Brown 3 retirements. The commission ultimately acknowledged that it expects the status of the three generating units to “come up again in the near future when LG&E/KU have a better idea of what the [EPA] Greenhouse Gas rules will look like and when they will be implemented.” (The EPA issued its final Carbon Pollution Standards on April 25.)

The KPSC also approved LG&E and KU plans to build a 120-MW solar array in Mercer County and acquire another solar pV array in Marion County, and a 125-MW battery storage unit.

A Big Change for a Fleet Still Dominated by Coal Generation

Despite the KPSC’s denials, construction of Mill Creek 5 is expected to prompt a dramatic shift in the LG&E and KU power profile. “Today, our generation energy mix is: 84% coal, 15% natural gas and 1% renewable energy,” the companies noted in November. “Once our planned unit retirements occur and our replacement generation is in service, our generation energy mix will change to: 62% coal, 29% natural gas and 9% renewable energy.”

GE Vernova in April noted the new gas plant will feature advanced technology. Only two  7HA.03 gas turbines—the largest 60-Hz heavy-duty gas turbine in the world and the most efficient in GE’s fleet—are currently operational at Florida Power & Light’s (FPL’s) newly inaugurated 1,260-MW Dania Beach Clean Energy Center (DBEC) in Broward County. 

GE Vernova told POWER it has so far bagged 23 total orders globally for the 7HA.03. While the two units have been operating at Dania Beach since 2022, another unit (KOSPO Shinsejong in South Korea) is slated to achieve commercial operation later this year.

GE Vernova noted that when built, Mill Creek 5 will be fueled initially by natural gas, but it will have “the ability to utilize up to 50% hydrogen (by volume) as hydrogen becomes more available in the future.”

For LG&E and KU, the priority will be to replace its Mill Creek workhorses with power technology that will offer more certainty. “We’re proud to serve the communities in which our employees live and work at the lowest reasonable cost, and the addition of a new NGCC at our Mill Creek Generating Station—which has provided ‘round the clock’ energy to our customers for decades—is an important part of how we’re continuing to plan for Kentucky’s energy future in a responsible, affordable and reliable way,” noted Lonnie Bellar, senior vice president, Engineering and Construction. 

GE Vernova suggested the performance of the new 7HA.03 gas turbine could provide LG&E and KU with much needed flexibility. The gas turbine includes “a highly flexible ramp rate of 75MW/min as validated at GE Vernova’s Test Stand 7 in Greenville, South Carolina,” the company said.

As part of the order announced in April, GE Vernova will also provide an STF-D650 steam turbine along with a W86 generator, a Vogt Heat Recovery Steam Generator (HRSG), and its integrated Mark* VIe control system for gas turbine performance management. GE Vernova said it wil also provide “services to help increase operational efficiency, expected to generate key savings in maintenance costs due to less unplanned maintenance for the combustion turbines.” In addition, data collected from sensors throughout the facility will be monitored and analyzed 24/7 at GE Vernova’s Monitoring & Diagnostics (M&D) Center in Atlanta, it said.

—Sonal Patel is a POWER senior editor (@sonalcpatel, @POWERmagazine).