Distributed solar desalination by membrane distillation: current status and future perspectives

Membrane distillation (MD) has been proven promising in solar-driven desalination. Moreover, its unique characteristics such as simple process, module compactness, high salt rejection rate, etc. allow for a small-scale device in a distributed system. Both theoretical and experimental researches on the cou-pling between solar collectors and MD aiming at compact and autonomous desalination system have been devoted to enhance freshwater productivity and energy efficiency. In this paper, certain critical gaps are summarized upon a panoramic review of the current status, including limited production and energy performance compared with commercial-scale desalination, unclear relation between solar collecting area and membrane area, and few discussions on efficient condensation, etc. To tackle these challenges, per-spectives on the essential future research directions are proposed. Solar direct heating and solar concen-tration constitute the possible resolution to enhance solar energy utilization for higher water production, which also raise the question of optimizing solar/MD areas. Meanwhile, module stacking, module internal heat recovery and external evaporation heat recovery are deemed prospective in further reducing MD en-ergy consumption. Subsequently, an enhanced vapor condensation needs more exploration. Those aspects and a potential combination among them are the main tasks in the near future, together with more field tests on small distributed solar-driven MD systems. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Membrane distillation (MD) shows promise in solar-driven desalination, but faces challenges such as limited production and energy performance, unclear relation between solar collecting and membrane areas, and lack of discussion on efficient condensation. Future research directions include enhancing solar energy utilization through solar direct heating and concentration, reducing energy consumption through module stacking and heat recovery, and exploring enhanced vapor condensation. Field tests on small distributed solar-driven MD systems are also crucial for the future.