The characteristics of ultramodern combined cycle power plants

• Methods to improve the efficiency of combined cycle power plants were presented.
• Effective utilization of heat from the turbine cooling air was implemented.
• Improvement of the gas turbine characteristics were analyzed.
• Analyzes in a wide range of compression ratios and temperatures were conducted.
• Economic analysis of the investigated unit was conducted.

In the paper are presented methods to improve the efficiency of combined cycle power plants. The efficiency increase is sought by the improvement of the gas turbine characteristics and by proposed effective utilization of heat from the turbine cooling air. The calculation methodology in a wide range of compression ratios and temperatures, far beyond currently applied values, with an assumed constant turbine outlet gas temperature, is presented. It is revealed that the efficiency rise without the use of this heat may be achieved only by improving the gas turbine characteristics. By introducing the additional steam cycle, an efficiency growth of 2–3 percentage points is gained, although this results in a corresponding increase in the compression ratio. An economic analysis is performed, which confirms that the presented development direction of gas turbines may be feasible under the condition of maintaining reasonably low gas turbine investment costs.