Comparative Analysis of Energy Recovery Configurations for Solar Vacuum Membrane Distillation

Vacuum membrane distillation (VMD) is a promising desalination technology, which is likely to be integrated with solar energy, and offers a sustainable solution to freshwater scarcity. However, its industrial application remains limited due to high specific energy consumption and water production costs. The key to improving VMD performance lies in enhancing the recovery of the latent heat of condensation. In this investigation, four different configurations are proposed; each differs in the method of condensation and energy recovery. The first is applied by using a basic condenser, preheating seawater with latent heat from vapor. The second is implemented by incorporating a liquid ring vacuum pump (LRVP), enabling both condensation and vacuum generation. The third is performed by coupling VMD with a heat pump, which operates by using a refrigerant fluid. Lastly, the fourth is employed by using mechanical vapor compression (MVC), where the vapor is compressed to recover heat efficiently. The results show that the VMD-MVC is the most efficient configuration, offering the lowest specific energy consumption (154.6 kWh/m3), the highest energy recovery rate (54.64%), the highest gained output ratio (GOR) of 5.52, and the lowest water production cost (4.6 USD/m3). In contrast, the VMD system coupled with a heat pump presented the highest water production cost (36.4 USD/m3) among all the evaluated configurations.