Under the right conditions in many arid regions, suspending a mesh material above a receptacle can yield clean water from airborne moisture, which is a viable means of producing potable water in places with no other alternatives. And like any technology, there's plenty of room for improvement and innovation in fog-harvesting, especially for areas with extremely limited clean water access.
Current systems tend to be fairly inefficient, condensing and capturing just 2% of the available water in a mild fog condition, but a new type of mesh developed by researchers at MIT and their colleagues in Chile, can boost water yields from airborne moisture by a factor of five or more.
The team found that the amount of water the mesh could harvest depended on several variables: the size of the filaments, the size of the holes between the filaments, and the coating applied to the surface of the filaments.
"Detailed calculations and laboratory tests indicate that the best performance comes from a mesh made of stainless-steel filaments about three or four times the thickness of a human hair, and with a spacing of about twice that between fibers. In addition, the mesh is dip-coated, using a solution that decreases a characteristic called contact-angle hysteresis. This allows small droplets to more easily slide down into the collecting gutter as soon as they form, before the wind blows them off the surface and back into the fog stream." - MIT
The new mesh was found to be capable of harvesting 10% of the available water in the air, which could potentially lead to a yield of 12 liters per day for each square meter of mesh in the right locations. The results of the research are published at ACS: Optimal Design of Permeable Fiber Network Structures for Fog Harvesting
An assortment of test fog-harvesting screens made from different materials have been installed on hilltops north of Santiago for a year-long test on the durability and yields for each different setup, including instrumentation to study the collection and growth of water droplets on the screens, which should help to further optimize the design.