Thermoeconomic evaluation of the feasibility of highly efficient combined cycle power plants

The paper proposes an analysis of the feasibility of highly efficient combined plants. The aim of the paper is to discuss and analyze different strategies for the increase of the efficiency of the combined cycle power plants with respect to those usually proposed in the literature. Resorting to the optimization of the components, joined with the use of regeneration and postcombustion (reheat) in the topping cycle it is shown how the combined plant efficiency can rise well over the actually well known limit of 60%. The possibility of obtaining such a high efficiency value is confirmed also by the proposed thermoeconomic optimization, based on the minimization of the total cost of the plant per unit power, obtained referring to a common economic basis the cost of the exergy losses and the costs of the components. The feasibility of obtaining combined plant with efficiency higher than 62%, simply by best fitting the available technology and without waiting for meaningful technological improvement of the gas turbines, is demonstrated.