Energy and exergy analysis of a combined cycle power plant

Abstract

In Bangladesh, the primary fuel is natural gas, predicted to be exhausted by 2025, and the availability of other fuels is also limited. Therefore, it is important to ensure proper utilization of available natural resources, which can be achieved by performing energy analysis and the exergy and exergoeconomic analysis. A detailed energetic, exergetic and exergoeconomic analysis of the Fenchuganj Combined Cycle Power Plant has been carried out in this thesis to investigate the possible scope of improvement of plant’s performance. Basic thermodynamic properties of the systems have been determined by energy analysis utilizing main operating conditions. Exergy destructions within the system and exergy losses to the environment were investigated to determine thermodynamic inefficiencies in the design and guide future plant improvements. Exergoeconomic analysis was carried out to assess the cost-effectiveness of individual components. Among the different approaches for thermoeconomic analysis in literature, Specific Exergy Costing (SPECO) method was applied to calculate each product, Per unit fuel cost and unit total generation cost. This thesis has determined the comparison of the configurations in terms of performance assessment parameters and costs per unit of exergy.The average range of thermal efficiency of the gas turbine is found 30.23%, the overall efficiency of the plant in simple cycle operation is 30.46%, and the plant's combined cycle efficiency is 43.21%. The average Heat Rate in simple cycle operation is 11,641.32 kJ/kWh, and the average Heat Rate in combined cycle operation is 8,369.55 kJ/kWh.The exergoeconomic analysis results indicated that the combustion chamber was the most cost-effective component, which a low cost of capital investment can improve. Comparing the Fenchuganj Combined Cycle Power Plant with other plants also represents that the combustion chamber is the plant's highest exergy destruction component. The heat energy loss in the combustion chamber decreases with an increase in air mass flow rate. This implies that a high mass flow rate of air can minimize the combustion chamber's energy losses as this would introduce more air for combustion. The component with the highest exergy improvement potential is the combustion chamber.