Conventional and Advanced Exergetic Analyses applied to a Combined Cycle Power Plant

Conventional exergetic, economic and exergoeconomic analyses assist in a rigorous evaluation of energy conversion system. A conventional exergetic analysis reveals irreversibilities within each component of a plant. The costs related to the irreversibilities are then estimated in an exergoeconomic analysis. These analyses, however, do not provide adequate information about interactions among components and the improvement potential of a structure. To determine which part of the inefficiencies and the related costs, identified in the exergetic and exergoeconomic analyses, is caused by component interactions and which part can be avoided through technological improvement of a plant, advanced exergetic and exergoeconomic analyses must be applied. Using these analyses helps to explicitly identify the exergy destruction and costs and separate them into two main groups: avoidable-unavoidable exergy destruction/cost and endogenous-exogenous exergy destruction/cost. More specifically, concerning the advanced exergetic analysis, the source of irreversibilities for a component is either component interactions (exogenous exergy destruction) or operational inefficiencies within the component (endogenous exergy destruction). Moreover, part of the overall irreversibilities exists due to physical, technological and economic constrains and cannot be prevented (unavoidable exergy destruction). Irreversibilities that can be prevented through design improvement constitute the avoidable exergy destruction. The exogenous and endogenous parts can be further split into avoidable and unavoidable parts facilitating the understanding of component interconnections and the estimation of the potential for improvement. Through the classifications developed in these analyses, the components that influence the performance of the overall process are identified and the focus lies on the avoidable part of the endogenous and exogenous exergy destruction. The present work focuses on the application of the advanced exergetic analysis to a complex energy conversion system: a three-pressure-level combined cycle power plant. The main objective is to identify the more influential components, in order to indicate changes related to the structure and the operation of the plant components that will result in a more efficient performance of the overall plant. Moreover the work has been also focused on the research of a standard and simplified procedure to apply the advanced exergetic analysis.