The Fog Collectors: Harvesting Water From Thin Air

by |March 7, 2011

Today nearly two people in ten have no source of safe drinking water according to the U.N. Millions of people, most of them children, die from diseases associated with inadequate water supply, sanitation, and hygiene each year. But in some desert areas, where there is very little rain, fog and dew are abundant sources of humidity that are being harvested to produce fresh water.

Fog or dew collection is an ancient practice. Archaeologists have found evidence in Israel of low circular walls that were built around plants and vines to collect moisture from condensation. In South America’s Atacama Desert and in Egypt, piles of stones were arranged so that condensation could trickle down the inside walls where it was collected and then stored.

Photo credit: FogQuest

FogQuest, a Canadian non-profit, uses modern fog collectors to bring drinking water and water for irrigation and reforestation to rural communities in developing countries around the world.  Fog collectors can be used in regions and deserts that receive less than one millimeter (about the thickness of a paper clip) of rain each year, but to work, they require fog and light winds.

Fog, a cloud that touches the ground, is made of tiny droplets of water—each cubic meter of fog contains .05 to .5 grams (half the weight of a paper clip) of water. Fog collectors look like tall volleyball nets slung between two poles, but they are made of a polypropylene or polyethylene mesh that is especially efficient at capturing water droplets. When the fog rolls in, the tiny droplets of water cling to the mesh, and as more and more cluster together, they drip into a gutter below that channels the water to a water tank. Fog collectors, which can also harvest rain and drizzle, are best suited to high-elevation arid and rural areas; they would not work in cities because of the space constraints and water needs of an urban environment.

Fog collection projects have used from 2 to 100 fog collectors, and depending on the location, each panel can produce 150 to 750 liters of fresh water a day during the foggy season. In the village of Chungungo, Chile where annual precipitation is less than 6 centimeters, 100 fog collectors produced 15,000 liters of water a year for ten years. Harvested fog water meets the World Health Organization’s drinking water standards.

The hills above Lima, Peru receive about 1.5 centimeters of rain each year, but fog from the Pacific Ocean moves in from June to November. FogQuest’s project in the village of Bellavista here is producing 2271 liters of water a day with seven fog collectors. Not only do they supply ample drinking water, they provide enough water for villagers to have gardens and grow tara trees which produce tannins that are sold for leather treatment.  Eventually, the trees will become self-sustaining, collecting their own fog water, reforesting the area and replenishing the groundwater.

FogQuest was founded in 2000 by Sherry Bennett and Robert Schemenauer, an atmospheric scientist who has been working on fog collection for over 20 years. The all-volunteer organization gets funding from grants, donations and membership fees. When a fog collection project is proposed, FogQuest first assesses the conditions of the location to make sure there is enough fog. Since the work of building and maintaining the fog collectors depends on the locals themselves, FogQuest needs a local partner and a community willing to pitch in. If these conditions are met and there is funding available, the organization builds a small fog collector, costing from $75 to $200, to see how much water can be harvested. If all goes well, larger fog collectors of approximately 40 square meters, which can produce 200 liters per day, can be set up for $1000 to $1500 each. The system is completely passive, requires no energy inputs, and can last ten years provided it’s taken care of.

Schemenauer’s first fog collectors were developed in El Tofo, Chile in 1987, which led to a fog collection project in the village of Chungungo, Chile in 1992. Since then, small and large fog collection projects have been established in Peru, Ecuador, Guatemala, Cape Verde Islands, Eritrea, South Africa, Yemen, Oman, Ethiopia, Israel, and Nepal. FogQuest is currently evaluating the potential of a project in Tanzania, and will soon construct 15 large fog collectors in Sidi Ifni, Morocco.

Stenocara beetle. Photo credit: JochenB

Scientists in Australia are developing an entirely different fog collection strategy modeled after the Stenocara beetle of the Namib Desert. The Namib Desert in southwest Africa is one of the driest places on earth, receiving less than 2 centimeters of rain annually, but night and morning fog from the Atlantic Ocean are the lifeblood of the desert’s flora and fauna.  When the fog sweeps in, the dime-sized Stenocara beetle clambers up the dunes, sticks his rear end into the air and faces his back to the fog. The configuration of hydrophilic (water-loving) bumps and hydrophobic (water-repellent) troughs between the bumps on his shell collect the moisture and channel water droplets right into the beetle’s mouth.

Inspired by nature’s design, scientists Chiara Neto, Stuart Thickett, and Andrew Harris from the University of Sydney have invented a synthetic surface using a combination of chemistry and structure. The surface is composed of two polymer layers: the top is hydrophilic, while the bottom is hydrophobic, which makes water droplets detach as soon as they get large enough. Similar surfaces inspired by the Stenocara have collected up to 10 liters of water per square meter every hour. The Australian scientists’ goal is to manufacture an equally efficient surface that could be used for local water harvesting—every house could have part of its roof coated with the surface to channel condensation into a rainwater tank. Prototypes have shown that this technology is several times more productive than mesh harvesting methods and could be scaled up to work in urban environments. Because each cubic meter of Australia’s coastal air holds 30 grams of water, this invention could be a boon for a country that has suffered severe droughts in recent years and is considered the driest inhabited continent on earth.

Photo credit: Luc Viatour

Meanwhile Chinese scientists are studying the structure of spider silk to learn why it is so effective at collecting water from the air. Under an electron microscope, Lei Jiang and Yong Zhao from the Chinese Academy of Sciences in Beijing and colleagues observed that spider silk fibers change structure when they come into contact with water. The fibers form hydrophilic spindle knots while the joints in between the knots remain smooth, so condensing water droplets slide along the smooth surfaces and coalesce into bigger drops at the knots. The scientists dipped nylon into a polymer solution; when it was stretched out, small polymer droplets formed, which became spindle knots once they dried. The scientists hope to use this research to develop synthetic materials that can direct and control water droplets more efficiently, which could potentially be used to make FogQuest’s fog collectors even more effective.

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19 thoughts on “The Fog Collectors: Harvesting Water From Thin Air

  1. 7LeagueBoots says:

    This was used in the Atacama desert in northern Chile. It provided all the water the town needed, but required more maintenance than the villagers were willing to put into it (the line tension is critical). They eventually switched back to trucked in water.

    If the maintenance issue can be dealt with this would be great, until then laziness will always be a problem.

  2. Dear Mme/Sir,
    Watching the dramatic results of the great famine in Africa, I would appreciate if you could inform me about technologies allowing collection of water from the air (maybe in hours with some humidity like evening or night).
    Your answer would be appreciated.
    Spyros Vrettos

  3. Renee Cho says:

    Dear Spyros,
    Here are some links about technologies that can pull water out of the air:

    There is also the technology used in Seawater Greenhouses which I wrote about in a previous blog:

    I hope this helps.

    -Renee Cho

  4. Tyler Morgan says:

    Good to know. I just found out that it might cost upto $20,000 to put a well on my parcel. For the intirum, I will be trucking a 200 gallon water trailer up the hill, filled from a well on my bosses’ property up the road. Water will be tight, but using fog harvesters and rain collectors will help immensely in getting some garden water in.

  5. Well Done Fog Quest!

    I am actually very surprised that some areas receive less than one millimeter (about the thickness of a paper clip) of rain each year! That blew my mind away.

    My partner is Chinese, So I will have to ask him if he knows anything about the Spider Silk study.

    Thanks for those links Renee, those links were an Intereting read 🙂

    Holly X

  6. Mary Seely says:

    I’m really sorry to see that the Australian scientists are using the erroneous recent article attributing the behaviour of the head-standing, fog-basking beetle Onymacris unguicularis (Nature 262(5566): 284-285, 1976) to Stenocara which does not display this behaviour. Although Nature refused to publish our rebuttal of the recent paper, the author did admit that he had not seen this behaviour in the field and had asked a student to collect beetles for him in a different habitat.

  7. Stacey says:

    Very well written. I gathered a lot of information for my science project. Thank you. 🙂

  8. B. Machlan says:

    I am working on a long range project to develop sustainable, accessible cities for emerging and developing countries, and want to incorporate a simple air to water system on all of the buildings. Where can I obtain details and sources for fog collectors.

  9. Renee Cho Renee says:

    I would start by clicking on the links in my blog and tracking down the University of Sidney scientists.

  10. fredrick oira-kenya says:

    excellent work to provide water to human life

  11. khaled sleem says:

    Dear sir

    I have seen the fog water collector, i have a question, does any propeline mesh could be used to collect water. or should it be specially made for this purpose? if so, where can i find this mesh? can i make myself.
    i am located in Lebanon in the Middle East.

  12. Leifur Thor says:

    Possibly using nano 3D printing, it may be possible to construct a mesh that would capture moisture of a much higher degree than what’s currently available, since the air must pass through without stopping it, but offer as much surface for the water to collect as possible, 3D nano printing could offer a host of solutions to this issue.

  13. Donatella says:

    Maybe this wouldn’t work for an entire city, but people have wind and sunscreens and fences on their individual properties already – why not substitute fog nets for some of these devices, they can screen the sun and the view along with being useful in other ways. Hook the bottom up to a cistern and I’m sure you could augment if not replace city water, as well as eliminate their penchant for poisoning the water with fluoride…

    So where does a person buy these nets? I would be happy to buy two, one for me, and one for a village that needs one somewhere.

  14. Alen says:

    Fog collecting was, and still is used in the Atacama desert for a very long time. I remember it in the 80’s being used there and was told by my mom that it was used since for a long time, but on a smaller scale. They did not stop out of laziness… prick.

  15. We live in Pululahua Crater in Ecuador need Fog harvesting curtains (system) please get info to me where we can buy them. there are 35 families who farm in the valley and we have a shortage of water

  16. David Swanson says:

    The island of St. Helena in the South Atlantic has used trees and other plants planted at it’s highest points to collect cloud condensation to fill cisterns that supply the town at the seashore for generations. I read about it in Joshua Slocums account of his circumnavigation at the turn of the previous two centuries. I live in Manila, California where we get fog or low clouds about 200 nights a year so far since I have lived here. I have a large garden with many trellises of berries, grapes and beans and other vining foodstuffs. I plan to try and supplement my water bill with some sort of screen built as a continuation of the trellises.wish me luck because I am not as smart as I look.

  17. Elena V says:

    Fog collected for local use is moisture that was supposed to travel somewhere else and didn’t. I would be curious to know how fog harvesting affects climate systems in the area surrounding the nets and also further afield.

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