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Performance evaluation of a combined cycle power plant (CCPP) is generally attempted using first law of thermodynamics based on energy and mass balance methodology. For detailed component wise performance analysis, exergy‐based evaluation based on second law of thermodynamics is gaining increasing importance. In this study, a CCPP consisting of triple pressure steam cycle with reheat is analyzed using both energy and exergy. Effect of ambient temperature, inlet and exhaust pressure loss, CCPP load, excess air percentage, cooling water temperature, and condenser vacuum has been investigated. Energy and exergy‐based performances are compared and presented. The simulation results show that efficiency of CCPP decreases with increase in the inlet and exhaust pressure loss and with increase in inlet air temperature to compressor. The total power output of CCPP decreases at higher inlet air temperature with increase of steam flow rate in bottoming cycle and increase in compressor power consumption. The exergy efficiency of combustion chamber, heat recovery steam generator, and condenser are found to be 77.48%, 87.20%, and 29%, respectively; and the overall exergy and energy efficiency of the unit at 100% design and operating condition is found to be 54.09%, 58.26% and 53.92%, 57.10%, respectively. The overall exergetic efficiency of the CCPP can be improved by reducing the losses in bottoming cycle. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1180–1186, 2017

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Steady state concept has relevance in many fields, particularly in economics, engineering and thermodynamics. In a steady state system, the recent observed behavior will continue to be so in future. Energy and exergy analysis (first and second law of thermodynamic) in steady state condition of a thermal power plant provides in-depth information to find out areas for potential improvement in efficiency. This study deals with the performance analysis of a pulverized coal fired power plant using energy and exergy analysis in steady state condition. The overall plant performance is assessed by undertaking detailed modeling and simulating thermal cycle of the plant scheme. Off design energy and exergy utilization efficiencies and thermodynamic properties are assessed from the model simulation based on actual operating data collected from the plant Distributed Control System (DCS) at operating load of 460 MW on 15-min average for a period of 8 h. The analysis revealed that the combustion chamber and boiler are the major source of exergy destruction with 40.29% and 53.20% respectively. Whereas gross energy and exergy efficiency of overall plant are calculated as 34.33% and 31.47% at 460 MW gross generation as compared to the design rating of 37.77% and 34.53% respectively at 500 MW. This paper deals with methodology and assessment of exergy destruction in the plant and how to reduce it. Simultaneously a comparison has been made of energy losses vis-a-vis exergy destruction of various plant components, which brings out advantages of using exergy method over energy method calculation.