Performance assessment of an industrial F-class combined cycle power plant with an air-cooled condenser using energy and exergy analysis

Combined cycle power plants are among the most efficient technologies for large scale electricity generation. This study presents a comprehensive energy and exergy analysis of an F-class combined cycle power plant equipped with dual three-pressure heat recovery steam generators, supplementary firing, and an air-cooled condenser. A detailed thermodynamic model was developed and validated against the manufacturer’s design data before being used to evaluate the plant under both design and representative off-design operating conditions. Under the design condition, the plant achieved a net power output of 734.3 MW, a net thermal efficiency of 54.6%, and an overall exergy efficiency of 54.1%. The energy analysis identified the air-cooled condenser as the largest source of energy loss because of heat rejection, whereas the exergy analysis showed that the gas turbine was responsible for approximately 71% of the total plant exergy destruction, followed by the heat recovery steam generator (15%). The steam turbine and heat recovery steam generator exhibited exergy efficiencies of 82.0% and 81.2%, respectively. The influence of ambient temperature, inlet air evaporative cooling, and supplementary firing was also investigated under representative operating scenarios. High ambient temperatures significantly reduced the plant power output, while evaporative cooling effectively recovered part of the lost capacity with a smaller efficiency penalty than supplementary firing. The proposed methodology provides a practical framework for the thermodynamic assessment and performance improvement of large scale air-cooled combined cycle power plants operating under water scarce conditions.