The plan by Duke Energy Carolinas to add a 750-MW, gas-fired combined-cycle plant at its existing Lee Steam Station is part of a broader plan that is in part needed to make up for the shutdown of coal-fired capacity on the system, including at the Lee site.
This Duke Energy (NYSE: DUK) subsidiary filed Oct. 25 at the South Carolina Public Service Commission for a Certificate of Environmental Compatibility and Public Convenience and Necessity on the gas project.
Writing supporting testimony was Janice Hager, Vice President, Integrated Resource Planning and Analytics for Duke Energy Business Services LLC, the service company subsidiary of Duke Energy.
Hager noted that following the completion at the end of 2013 of the coal-fired Cliffside Unit 6 (825 MW) and the 620-MW Dan River Combined Cycle gas facility, and the recent retirements of the coal-fired Riverbend Units 4-7 (454 MW) and Buck Units 5-6 (256 MW), the Duke Energy Carolinas existing generation portfolio mix includes 7,172 MW of coal, 1,240 MW of combined cycle, 2,770 MW of combustion turbine, 5,965 MW of nuclear, 3,229 MW of hydro, 251 MW of purchases, 911 MW of demand side management and 185 MW of renewable energy.
In the current planning horizon, the coal-fired Lee Units 1-2 (200 MW) are projected to retire on or before April 15, 2015. Lee Unit 3 (170 MW) is projected to retire as a coal unit and to be converted to natural gas before the summer of 2015. The retirement of these units, as well as those already retired, is driven by the requirements of air permits for the company’s new coal and combined cycle units at Cliffside, Buck and Dan River, as well as the North Carolina Utilities Commission approval order on Cliffside Unit 6, and expected and known environmental regulations such as the federal Mercury and Air Toxics Standards. “It is the combination of unit retirements and load growth that is driving the 2017 need that the Lee Combined Cycle Project will satisfy,” Hager wrote.
The coal-fired Buck Steam Station Units 3 and 4 were retired in May 2011. The Cliffside Units 1-4 and Dan River Units 1-2 coal facilities were retired in October 2011 and April 2012, respectively, in advance of the initial testing of new generation at those locations. The remaining un-scrubbed coal units at Buck and Riverbend were retired in April 2013, nearly two years earlier than previously planned.
Duke picked its own bid from those offered in an RFP
In November 2012, Duke Energy Carolinas (DEC) received multiple proposals from twelve companies including a DEC self-build bid for the construction of a natural gas combined cycle facility at the existing Lee site in Anderson County, S.C. The bids were reviewed for compliance with request for proposals (RFP) guidelines and were ranked economically to determine the least cost options. The initial economic analysis identified the short-listed bidders to continue proposal discussions. In late February, DEC notified the short-listed bidders to provide refreshed proposals to meet capacity needs beginning June 2017. The Lee self-build option was picked after refreshed bids were taken.
Mark Landseidel, Director of Project Development and Initiation in the Project Management and Construction Department of Duke Energy, provided details in the application about the planned Lee gas plant.
The existing Lee station is located on the Saluda River, near the town of Williamston in Anderson County, S.C. Lee began operation in 1951 and has three operating coal-fired units: Units 1 and 2 are 100 MW units that began operation in 1951. Unit 3 is a 170 MW unit that began operation in 1958. There are also two existing simple cycle combustion turbine units at the Lee site with a combined capacity of 84 MW that began commercial operation in 2007.
The Lee combined cycle facility will use two combustion turbine generators (CTGs), two heat-recovery steam generators (HRSGs), and one steam turbine generator in a“2×1” configuration, Landseidel wrote. Duke Energy Carolinas evaluated F Class and Siemens H Class combustion turbine technologies in various configurations. The 2×1 technology selection was chosen based on the need as well as the company’s and industry experience. The need fits well with current F Class technologies that are designed with moderate duct burning capabilities.
Recent Duke Energy Carolinas gas-fired projects at Buck and Dan River were successfully executed and operated with the same technology and configuration.
There is a natural gas interstate pipeline located about one mile from the plant site. Natural gas will be supplied to the facility via pipelines owned and operated by Williams Transco Main Pipeline and Piedmont Natural Gas Lateral Pipeline. The capacity of the new gas lateral to the Lee plant site will be around 5,800 million standard cubic feet per hour.
The project scope proposes to connect to the transmission grid at 100 kV, with a new 100-kV switchyard to be constructed. All new transmission facilities will be located on existing company property at the Lee Steam Station site. No new rights of way or additional property will be required.
Duke Energy Carolinas is soliciting competitive bids for long lead major plant equipment (such as combustion turbines, HRSGs, the steam turbine, and generator step-up transformers) which the company will purchase directly. It is also soliciting competitive bids from qualified contractors for the engineering, procurement and construction (EPC) scope of work. These major equipment supply and EPC contractor bids will be evaluated and awarded in 2014 as required to maintain the schedule for plant operation by the summer of 2017.
The Lee Combined Cycle Project will use a wet cooling tower for steam turbine condenser cooling which will minimize both the intake and discharge impacts to the Saluda River. Duke Energy Carolinas has previously investigated other condenser cooling technologies that would further reduce the evaporative water use. However, considering the overall environmental impacts, water consumption, cost and efficiency factors, the utility determined that a wet cooling tower is the best choice of condenser cooling technology for the Lee project, Landseidel noted.