Review on Thermal Vacuum Desalination: Technologies, Challenges and Sustainable Pathways

Global water scarcity and the energy demand of conventional desalination motivate the development of thermal vacuum desalination (VD), which lowers the boiling temperature of saline water and can use low-grade heat from solar, waste-heat, ocean-thermal, and geothermal sources. This review traces the progression from passive natural-vacuum systems to forced-vacuum, ejector, spray-flash, falling-film, and membrane configurations. Reported headline values are case-specific. A reviewed multistage solar natural-vacuum configuration reported thermal efficiency up to 86%, and one experimental variable-geometry radial ejector reported an average entrainment-ratio improvement of 107% relative to its tested reference geometry. An experimental solar Venturi prototype produced 7.01–9.02 kg/(m2·d), depending on its operating cycle. Separately, a validated Aspen Plus simulation of a 14-effect MED-HV system reported a GOR of 13.49, while an experimental DCMD-crystallization study reported 98.9% water recovery for hypersaline produced water. Despite these promising results, the large-scale deployment of vacuum desalination technologies remains hindered by operational instabilities, intermittent thermal inputs, and membrane scaling. This review critically evaluates vacuum desalination technologies by distinguishing modeled, laboratory, pilot-scale, and review-derived evidence. It assesses energy consumption, techno-economic feasibility, and environmental performance on a case-specific basis. This review highlights major challenges in vacuum desalination (VD), such as vacuum stability, intermittent operation, scaling, irreversible membrane wetting, and long-term performance validation, and suggests research priorities for the future. Through this assessment of key findings, this review outlines a strategic approach to advancing thermal VD technologies toward sustainable, practical applications by integrating water treatment, energy efficiency, and mineral recovery through water–energy–mineral synergies.