A Review of Vacuum-Enhanced Solar Stills for Improved Desalination Performance

Abstract

The lack of freshwater and the low efficiency of the traditional solar stills have led to the search to find a technology that can enhance desalination by use of vacuum-enhanced solar still technology. This review intends to investigate the impact of integrating a vacuum into solar stills, which include vacuum membrane distillation (VMD), nanoparticle-enhanced solar stills, multi-effect/tubular solar stills, geothermal integration and parabolic concentrator solar stills. The most important findings show that the productivity improves greatly: vacuum-assisted solar stills give up to 133.6% more product using Cu2O nanoparticles, and multi-effect tubular stills under vacuum (40−60 kPa) show a doubling in freshwater productivity (7.15 kg/m2) in comparison to atmospheric operation. Geothermal cooling and vacuum pump systems show a 305% increase in productivity, and submerged VMD reached 5.9 to 11.1 kg m−2 h−1 with solar heating. Passive vacuum designs further reduce the energy used down to a specific cost, using as little as USD 0.0113/kg. Nevertheless, membrane fouling, initial cost, and the complexity of the system can still be termed as the challenges. This review highlights the significance of vacuum-enhanced solar stills to address the critical issue of freshwater scarcity in arid regions. The integration of vacuum membrane distillation, nanoparticle and heat recovery into vacuum-enhanced solar stills enabled us to improve the economic feasibility. We conclude that vacuum technologies significantly boost the efficiency and economic feasibility of solar desalination as a potential approach to sustainable desalination. Specifically, these inventions will contribute to providing a renewable and cost-effective solution for freshwater production. Further investigations are required to overcome the existing challenges, such as system complexity and membrane fouling, to effusively comprehend the efficacy of vacuum-enhanced solar stills to ensure sustainable water management.