The typical simple-cycle efficiency is 33–43% at maximum load and drops significantly at partial load. The efficiency for a CCGT will vary with size and type of turbine selected. But tends to increase with the size of the turbine. A combined-cycle power system is an established technology for larger, onshore power generation plants.
It uses a General Electric 9HA, that claimed 41.5% simple cycle efficiency and 61.4% in combined cycle mode, with a gas turbine output of 397 MW to 470 MW and a combined output of 592 MW to 701 MW. Its firing temperature is between 2,600 and 2,900 °F (1,430 and 1,590 °C), its overall pressure ratio is 21.8 to 1.
A combined-cycle power plant uses both a gas and a steam turbine together to produce up to 50% more electricity from the same fuel than a traditional simple-cycle plant. The waste heat from the gas turbine is routed to the nearby
Suppose that the gas turbine cycle has an efficiency of 40%, which is a representative value for current Brayton cycle gas turbines, and the Rankine cycle has an efficiency of 30%. The combined cycle efficiency would be 58%, which is a very large increase over either of the two simple cycles.
Current F class gas turbines have simple cycle efficiency ranging from 36% to 38.5% and combined cycle efficiency from 56% to 58% based on natural gas lower heating value (LHV) (Lebedev and Kostennikov, 2008). The current state-of-the-art gas turbine technologies include the G and H classes.
Combined cycle gas turbine (CCGT) power plants fired by natural gas have higher thermal efficiency and lower CO 2 emissions than their coal-fired counterparts. With the rapid increase of energy demand and stricter environmental regulation, CCGT plants are now undergoing widespread installation.
The gross efficiency (LHV) at Shunde is 43% (43.8% nominal), based on a guaranteed heat rate of 8376 kJ/kWh (8221 nominal). Slow roll to running speed with the gas turbine takes 5 minutes. Getting the steam turbine running takes approximately two hours).
EDF and GE installed the first commercial 9HA gas turbine in the Bouchain power plant and set a new world record for combined cycle efficiency—62.22%.
High-pressure steam from these boilers can be used to generate additional electric power with steam turbines, a configuration called a combined cycle. A simple cycle gas turbine can achieve energy conversion efficiencies ranging between 20 and 35 percent.
A combined-cycle gas turbine (CCGT) power plant is essentially an electrical power plant in which a gas turbine and a steam turbine are used in combination to achieve greater efficiency than would be possible independently.