Energy efficient membrane distillation through localized heating

Membrane-based desalination technologies are crucial for generating clean water, but are energy intensive. Localizing heat generation at the liquid-membrane interface could reduce energy consumption while maintaining sufficient mass flux. Here, a locally heated membrane distillation approach is analytically and experimentally evaluated. The measured evaporated mass flux matches the analytical limits considering diffusive and advective mass transfer across a heated porous membrane into stagnant air. Experimentally, thermally-stable silver membranes demonstrate similar mass flux compared to conventional polymer based membrane at the same surface temperature. At high membrane temperatures (∼80 °C), the locally heated membrane distillation demonstrates good efficiency with up to 75% reduction of energy compared to direct contact membrane distillation and airgap membrane destination. Efficiency can be further improved with better thermal design of the supporting structure and permeate heat recovery.