Thermodynamic analysis of an integrated solar-based multi-stage flash desalination system

Worldwide concern about the scarcity of global water resources is increasing day by day. In Gulf countries, most power plants are co-generation power desalting plants (CPDP) that generate electric energy and also produce fresh water through the desalination of seawater. Nowadays, renewable energy provides a viable solution to the scarcity of energy resources and an environmental friendly option of global economy. In this paper, thermodynamic analyses have been performed on an integrated solar-based multi-stage flash desalination/Rankine cycle system. The respective losses as well as the first-law and second-law efficiencies for the system have been evaluated. The first-law and second-law efficiencies of the solar field were found to be 61.70% and 31.74%, respectively. The solar thermal field is based on direct steam generation method. Moreover, the mass flow rate through the Rankine cycle has been optimized to produce the maximum power. The optimal mass flow rate through the Rankine cycle found to be 51 kg/s. Furthermore, this paper presents and investigates a model of distillation plant that can use the heat rejected from the condenser of the Rankine cycle. The model is analyzed and validated with other results gained from literature. It found that the highest exergy destruction through the distillation unit occurs within the stages of the MSF unit. The percentage of exergy destruction in the MSF stages was found to be 75.41% of the total exergy destruction in the distillation unit. Additionally, this study verifies that increasing number of MSF stages decreases the percentage of exergy destruction.