MIT Is Looking To Pull Fresh Water Out Of Thin Air
This may not be my usual fare - if indeed I can be said to have one - but it's interested me enough that I simply had to write about it. Sit down, folks, and let me tell you a story about the natural world, and how, yet again, it's inspiring scientific progress and development. Not surprisingly, this story involves MIT - I've been writing a lot of pieces on them lately, it seems.
There is a region in central Chile known as the Fray Jorge Fog Forest. In this semi-arid region, rain is an extremely rare event - so much so that it's effectively nonexistent. By all rights, plants and animals should find it difficult to survive in such a clime. Water is, after all, the most basic ingredient for life on Earth.
Fascinatingly enough; there exists in this region a specialized group of plants and insects with a very interesting adaptation. These creatures, in the absence of rainfall or any standing bodies of water, have evolved to pull water straight out of the air, harvesting moisture from the fog that frequently drifts in off the nearby ocean. After observing this interesting evolution, researchers at MIT - with the co-operation of colleagues in Chile - are looking to imitate it on a much, much larger scale.
Sort of. See, it's worth noting that fog harvesting is hardly a new or revolutionary idea. Systems designed to create potable water from the air already exist in at least seventeen nations across the globe. What MIT seeks to do isn't to invent a new technology, but to offer innovations on an old one - the research carried out by the Institute found that, in mild fog, the efficiency of water harvesters can be increased by a factor of at least five.
MIT's findings have been published by MIT postdoctorate Kyoo-Chul Park and MIT alumnus Sheerang Chhatre, chemical engineering professor Robert Cohen, mechanical engineering professor Gareth McKinley, and graduate student Siddarth Srinivasan. They can be found online, in the American Chemical Society publication Langmuir.
Traditional fog-harvesting systems consist of a large, vertical mesh. Regulation of this mesh, the researchers found, is the key. The size of the filament in the net, the size of the holes between the filament, and the coating applied to the filaments are all vital components in making these systems more efficient.
The problem with most current systems is that they're made of woven polyolefin mesh - which is both easily available and inexpensive - and tend to have both holes and filaments that are far too large. As a result of this flaw, they only collect about 2% of the water to be found in a fog condition. With a finder mesh, the research found, this number could be increased by 10% or more, with multiple nets stacked side by side to gather even larger quantities of water.
According to calculations carried out by the researchers, fog harvesters can gain the best performance from a mesh of stainless steel filaments about three or four times the thickness of human hair, with double that size in spacing between the fibers. The mesh additionally must be dip-coated, using a solution that allows small droplets to more easily slide into the collection basin before being blown away. Check out the videos below for more details.
With this new design, systems deployed at the edge of the Atacama Desert could yield up to 12 liters per day or more of drinking water.
Currently, MIT researchers are collaborating with the Pontifical Catholic University in Santiago, Chile to test a variety of different screen designs in a semi-arid region north of the city. The water yield and durability of each configuration is being painstakingly tested; depending on the results, they may even find a design more efficient than the one mentioned above.
Not that they haven't made huge strides already: Daniel Beysens of the Heterogeneous Media Laboratory in Paris declared this paper an extremely important resource for anyone looking to collect water from fog, even going so far as to declare it a "breakthrough in the design of fog collectors."
The research was supported by a Samsung Scholarship, MIT's MISTI-Chile program, the Xerox Foundation, and the MIT-Legatum Center for Entrepreneurship.