Effect of Ambient Conditions on Energy and Exergy Efficiency of Combined Cycle Power Plant

The exergy analysis acts as a powerful tool for a clear variation between losses of energy to the surrounding and irreversibilities in the system. This paper evaluates the effect of ambient conditions on energy and exergy efficiency of a 50 MW capacity combined cycle power plant. To carry out performance analysis, a code was developed in Python language, and the results were first validated with the component wise exergy efficiency data of Ersayin and Ozgener (Renew Sustain Energ Rev. 43:832–842, 2015). For ambient temperature varying from 17 to 42  C, the energy efficiency reduced from 64.1 to 54.5%, while the overall exergy efficiency of the plant reduced from 57.5 to 48%. The ambient temperature rise led to increase in specific volume of inlet air to gas turbine unit, and subsequently, compressor power consumption was increased. The rise in ambient temperature had also increased heat recovery steam condenser back pressure from 7260 to 10,520 Pa. Although steam quality at exit of low pressure (LP) turbine was improved from 0.881 to 0.8925, but the rise in back pressure had reduced LP turbine output and energy-exergy efficiency of the plant. Based on exergy analysis of the plant, it is found that combustion chamber had most exergy destruction rate among all the system components.