Potential application of membrane distillation in ocean thermal energy conversion: fundamentals and perspectives

Albert S. Kim, Hyeon-Ju Kim
Civil and Environmental Engineering, University of Hawaii at Manoa, United States

Keywords: membrane distillation, evaporation, condensation, phase conversion

Membrane distillation (MD) is a non-isothermal membrane separation process involving the thermally driven transport of water vapor through non-wetted pores of hydrophobic membranes. The driving force for this gaseous transport is the gradient of the vapor pressure across membrane pores (i.e., macroscopically between feed and permeate sides of the membrane), which is maintained by introducing hot feed and cold permeate streams. Water molecules evaporate at the feed-side pore inlets, migrate though the (tortuous) pores, and condense on the permeate-side pore outlets (or in an external condensing unit). The temperature difference across the membrane is about 30 – 50o C, which is a little higher than that for ocean thermal energy conversion processes. As the fundamental scheme of OTEC is to generate electricity using an ocean temperature difference, using MD as a supplementary process of OTEC will increase the energy conversion efficiency and contribute to seawater desalination. This research introduces the fundamentals of MD and provides its application perspective for OTEC desalination.

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