Southaven Combined Cycle Plant

In May 2008, TVA purchased the Southaven Combined Cycle Combustion Turbine Plant in Desoto County, Miss. This 118-acre facility helps reduces the need for TVA to purchase higher-priced power from external sources during periods of high demand.

Efficient power production helps meet intermediate needs

Southaven is one of 12 combustion-turbine sites in the TVA power system and one of four with combined-cycle units. The units at Southaven run on natural gas and can reach full power in about one hour, depending on the status of the units.

The units are capable of cycling on and off daily and are used for 12 to 16 hours per day to meet power demands longer than peaks but briefer than continuous base-load. The site interconnects with the TVA transmission system and neighboring systems.

How it works

Combined-cycle units are enhanced versions of single-cycle combustion turbines. They burn natural gas or low-sulfur oil and operate on the same principle as a jet engine. Air entering each unit is compressed, mixed with fuel, and ignited. The hot gas expands through turbine blades that turn generators to produce electricity.

Combined-cycle units generate 50 percent more power than simple-cycle turbines from the same amount of fuel. They do this by using the exhaust gas from the first turbine to produce steam that can generate additional electricity from a second turbine.

The Southaven plant can produce extra steam and 75 megawatts more power by operating additional burners in the second combustion phase – a process called duct firing.

Emissions

The combustion turbines produce very low nitrogen oxide and carbon emissions. The heat recovery steam generator on Southaven’s combined-cycle units uses a selective catalytic reduction system to reduce NOx to about 30 percent of what a simple-cycle combustion turbine using similar technology would emit.