Membrane Distillation

Membrane distillation (MD) is a thermal separation process that distills water. Warm seawater is separated from cold feed-water with a hydrophobic (water repellent) membrane. The liquid streams remain separated by surface tension, while higher vapour pressure drives steam molecules across the membrane.
In application, various layers separate the warm seawater, the product distillate, and the cooling water. A temperature difference of 5 to 10 K is sufficient to drive the MD process.

SolarSpring uses membrane distillation technology in a spiral-wound module with counter-current heat exchange.  Incoming seawater is used as the cooling medium in the module, and is preheated before passing to the solar collectors.  Warm seawater from the collectors returns to the hot-side of the membrane, where it is distilled into product water. Applications of these modules are: MMD-Desalination and Oryx-Desalination.