Simple-Cycle Plants
From Operations - Power Operations - Technologies - Natural Gas
Simple-cycle plants are the most flexible and operate as quick-responding 'peakers' that generate power when demand is highest.
Product Details
The simple-cycle process is the starting point for natural-gas-fired power generation. Clean-burning natural gas powers a combustion turbine, which is connected directly to a generator that produces electricity. Some of Calpine’s power plants, particularly in the eastern United States, are also equipped to produce power from ultra-low-sulfur fuel oil when market conditions warrant.
A combustion turbine in a power plant is similar to a jet engine on an airplane. The process starts as air flows through intake structures, where it is filtered before entering the combustion turbine. The air then enters the gas turbine, where it is compressed, mixed with natural gas and ignited, which causes it to expand. The pressure created from this expansion spins the turbine blades, which are attached to a drive shaft and generator, creating electricity.
Some of Calpine’s plants operate in simple-cycle mode only. They ramp up quickly and provide power during periods of high demand. Others integrate steam turbines and/or cogeneration technologies to improve efficiency and increase generation capacity.
Combined Cycle
Highly efficient combined-cycle plants maximize the electricity-producing potential of their fuel source by combining natural gas and steam generation technologies. This process uses the extremely hot exhaust from natural-gas combustion turbines (see the description of the simple-cycle process) to create steam and generate additional electricity.
Heat recovery steam generators (HRSGs) contain boiler tubes filled with ultrapure water. Hot exhaust flows past these tubes, turning the water into steam. The steam is routed to steam turbines, which are connected to their own generators. HRSGs are so efficient that exhaust leaving turbines at more than 1,000 degrees Fahrenheit is reduced in temperature to about 200 degrees by the time the heat recovery process is completed.
The spent steam then flows into a condenser. The condenser converts the steam back into water, which is returned to the HRSG in a closed-loop cycle to be reused. In most cases, a cooling tower adjacent to the plant provides a constant flow of cool water to the condenser.
Click here to watch a video describing the combined-cycle power production process at our Russell City Energy Center.
Cogeneration
A simple-cycle or combined-cycle plant may incorporate cogeneration – or combined heat and power – capabilities. In this process, a heat recovery steam generator (HRSG) uses heat from natural gas turbine exhaust to produce steam (see description of the combined-cycle process). Some or all of this steam is piped to a customer that uses it in an industrial process or for heating. Depending on the steam needs of the host facility and the local power market, some facilities are also equipped with a steam turbine to obtain combined-cycle efficiency from steam produced in excess of the host facility’s needs. In a different type of cogeneration cycle, the energy of the steam cycle can also be used to operate chillers to produce chilled water. Cogeneration is a cost-effective way to support the energy needs of local industry and one of the most efficient ways to generate electric power.
Calpine operates the nation’s largest portfolio of cogeneration plants. Examples include:
- The Kennedy International Airport Power Plant on Long Island, which provides electric power as well as chilled and hot water to the airport.
- The nearby Stony Brook Power Plant, which sells electricity and steam to the neighboring State University of New York Stony Brook.
- Several cogeneration plants along the Houston Ship Channel, including the Deer Park Energy Center, which provide steam for the petrochemical industry.
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