Exergoeconomic Analysis of Power Plants: Impact of Exergy Destruction Due to Entropy Generation on Unit Cost of Electricity

Various exergy-based exergoeconomic methods have been developed to evaluate the production cost of electricity in power systems. One of the unresolved issues in the field of exergoeconomics is that different exergoeconomic analysis methods can yield different unit costs of power production. In this study, the unit cost of electricity generation is comprehensively analyzed using three representative approaches: the Moran method, the specific exergy costing (SPECO) method, and the Modified Productive Structure Analysis (MOPSA) method. The objective of this study is to identify a condition under which different exergoeconomic methods yield the same production cost for a power plant. The results show that power production costs are obtained using all three exergoeconomic methods when the costs associated with exergy destruction are appropriately incorporated in the cost-balance equation. In other words, under this condition, the cost-balance equations of SPECO and MOPSA for the entire power plant reduce to the Moran equation. These findings indicate that the critical issue in exergoeconomic analysis for determining the unit cost of products is whether the cost of exergy destruction is explicitly or implicitly accounted for. Furthermore, the numerical results demonstrate that all input cost rates, including equipment investment, operation and maintenance, and fuel costs, are fully recovered through the cost flow rates of the products. It is also shown that the cost flow associated with exergy destruction ultimately appears as the cost flow of waste streams.