Exergoeconomic analyses of a Combined Water and Power Plant (CWPP)

Abstract

In this study, exergy and thermoeconomic analyses of MSF/MED and Reverse Osmosis (RO) processes are presented. Exergy analyses of every streams, both incoming and outgoing, for each plant configurations have been performed to quantify the exergy losses. The evaluation of cost depends upon the chosen methodology of accruing fuel cost. The exergy equations coupled with appropriate cost provide a valuable insight into areas of potential improvement of the Combined Water and Power Plant (CWPP). Various combinations (Combined cycle power plant (CCPP) with stand alone MSF, MED and RO; CCPP with MSF-RO hybrid or MED-RO hybrid) have been considered. This study reveals that major exergy losses occur in the evaporators (about 34%) especially in the first and last few stages, in case of MSF, and, hence, improvements in the evaporator design will have significant impact on the whole plant performance. Similar trend is also observed for MED. It exhibits low exergetic efficiency for the first stage as well the last few stages. All these results suggest that more focus on these design aspects have potential for further improvement. Moreover, among the three top brine temperatures 65 °C, 70 °C and 75°C, 65 °C show better exergetic efficiency. Comparison between MSF, MED shows that unit product cost decreases by about 30% in favor of MED. Copyright © 2009 by ASME.