Energy, exergy, and thermoeconomic analysis of a natural gas combined power plant

This paper explores an innovative power plant design integrating three organic Rankine cycle (ORC) subsystems with a Brayton cycle (BC) to enhance energy conversion efficiency by utilising various waste heat sources. The study applies advanced energy, exergy, and thermoeconomic analyses to comprehensively assess the performance of a natural gas combined cycle (NGCC) power plant, using the energy equation solver (EES) software. The model has been validated against previous research with different parameters, such as compressor efficiency, ambient temperature, and pressure ratio, confirming its accuracy and reliability. The numerical results demonstrate that increasing compressor efficiency from 70 to 88% boosts the NGCC system’s net power output by nearly 60% compared to the Brayton cycle alone. Additionally, both energy and exergy efficiencies of the NGCC improve by 6.6% from the initial state, while the annual cost rate shows a parabolic increase over this range. Furthermore, higher turbine efficiency leads to a 14% increase in overall energy efficiency and a 13% increase in exergy efficiency. An increase in pressure ratio from 6 to 15 raises energy and exergy efficiency by 4% and 3%, respectively. However, the influence of the pressure ratio is less significant compared to the other parameters. Moreover, cycle performance is inversely related to ambient and exhaust gas temperatures.