Seawater Desalination Using a Salinity-gradient Solar Pond-vacuum Freezing Ejector Absorption Hybrid System

Abstract:

Seawater desalination is an attractive but energy-intensive process used to produce freshwater. In this study, we propose a salinity-gradient solar pond-vacuum freezing ejector absorption hybrid system to produce freshwater from seawater using solar-thermal energy as the power source. A salinity-gradient solar pond is used to collect and store solar-thermal energy; and a vacuum freezing ejector absorption (VFEA) system converts the seawater into potable freshwater. The system desalts seawater by transforming part of the seawater into solid ice crystals. During the ice crystal formation, impurities (including salt ion, contaminants) are excluded from the crystal structures so that high-quality freshwater can be obtained. The system has the potential to use much less energy than traditional thermal distillation processes since the latent heat of fusion (335 kJ/kg) is much less than the latent heat of evaporation (2503 kJ/kg). In addition, the pre-treatment of feed seawater can be less intensive since the impurities in the seawater can be automatically excluded from the ice crystal. Also, the brine generated from the system can be discharged into the solar pond, acting as the salty water source of the solar pond