Advanced Exergoeconomic Analysis Applied to a Complex Energy Conversion System

Abstract

Exergy-based analyses are important tools for studying and evaluating energy conversion systems. Conventional exergy-based analyses provide us with important information on the design and operation of a system. However, further insight into the improvement potential of plant components and the overall plant, as well as into component interactions, is important when optimal operation is required. This necessity led to the development of advanced exergy-based analyses, in which the exergy destruction as well as the associated costs and environmental impacts are split into avoidable/unavoidable and endogenous/exogenous parts. Based on the avoidable exergy destruction, costs and environmental impacts potential and strategies for improvement are revealed. The objective of this paper is to demonstrate the application, the advantages, and the information obtained from an advanced exergoeconomic analysis by applying it to a complex plant, i.e., to a combined cycle power plant. The largest parts of the unavoidable cost rates are calculated for the components constituting the gas turbine system and the low-pressure steam turbine. The combustion chamber has the second highest avoidable investment cost and the highest avoidable cost of exergy destruction. In general, the investment cost of most of the components is unavoidable, with the exception of some heat exchangers. Similarly, most of the cost of exergy destruction is unavoidable, with the exception of the expander of the gas turbine system and the high-pressure and intermediate-pressure steam turbines. The advanced exergoeconomic analysis reveals high endogenous values, which suggest that improvement of the total plant can be achieved by improving the design of individual components, and lower exogenous values, which means that component interactions are in general of lower significance for this plant.