Abstract: Increased competition among power generating companies, changes in generating system load requirements, lower allowable plant emissions, and changes in fuel availability and cost accentuate the need to closely assess the economics and performance of older electric generating units. Generally, decisions must be made as to whether these units should be retired and replaced with new generation capacity, whether capacity should be purchased from other generation companies, or if these existing units should be repowered. These decisions usually require the evaluation of many factors. The analysis is usually complicated due to the interaction of all the factors involved. In this paper, evaluation of a 156MW steam power plant and proposed repowered scenario has been performed. The exergy and exergoeconomic analysis method was applied in order to evaluate the proposed repowered plant. Simulation of each case has been performed in Thermoflow software. Also, computer code has been developed for exergy and exergoeconomic analysis. It is anticipated that the results provide insights useful to designers into the relations between the thermodynamic losses and capital costs, it also helps to demonstrate the merits of second law analysis over the more conventional first law analysis techniques
