Thermoeconomic analysis of a solar MVC desalination system

Globally, about 10% of the world population does not have access to enough fresh water. In many hot-and-dry coastal regions and islands, the desalination of seawater might be the only practical option to have a fresh water supply. Therefore, low-cost desalination system is critical for freshwater demands. To address this issue, a desalination system consisting of solar photovoltaic (PV) and mechanical vapor compression subsystem is proposed in this study. The entire desalination system was modeled and designed to produce 10,000 m³ of fresh water per day at the coast of San Francisco, California. Key components such as water vapor compressor, solar PV panel, and three-stream heat recovery unit were designed, and their performances were analyzed. The effects of design variables and operating conditions on the system performance were investigated through a parametric study. Finally, an economic analysis was conducted and compared with current desalination technologies. The analysis results show that the specific power consumption of desalination system can reach 14.4 kWh/m³ when the evaporation temperature is 70°C. It is found that the evaporating temperature has a great influence on the heat pump system efficiency and evaporator design. The levelized cost of the proposed system is $0.76 per m³ of fresh water which is lower than current grid-powered vapor compression desalination system and other thermal desalination systems. The proposed solar PV driven desalination improves thermoeconomics of desalination system by applying low-lift operating condition to the vapor compression cycle so that it can contribute to solving the fresh water supply challenges.