Extracting water from the air might seem like magic, but the technology is very real. In fact, it might just be one of the most important innovations of the last few decades if fears of future water scarcity are actually true.
And such technologies couldn't come sooner. Poor water management strategies, growing populations, geopolitics, and both natural and anthropogenic environmental changes are all contributing to pushing some areas to run critically low on potable water. The problem is only set to get worse, with some estimates predicting that 87 countries will be in a state of water scarcity by 2050.
But, like so many things in life, "necessity is the mother of all invention". Human ingenuity may well have already provided a partial solution to the impending problem.
How can you extract water from the air?
Water-from-air devices, also known as atmospheric water generators (AWG), are pieces of technology that are able to, through a variety of methods, effectively condense water vapor from ambient, usually humid, air. How this is achieved does vary, but most will take advantage of the process of condensation to cool, condense, and then collect liquid water.
Of the current existing technologies, most systems tend to work in a similar way to air conditioners — but not all. By using heating/cooling coils, these machines reduce the temperature of the air in order to cool the air below the dew point of water vapor to turn it into liquid water.
Other methods also exist, including the use of desiccants or pressure to achieve the same goal.
However it is achieved, these devices differ from similar machines, like dehumidifiers, in that their main task is to remove water from the air to provide potable water.
Such machines are critically important in areas of the world where pure drinking water is scarce or very difficult to obtain. While most AWG devices can only extract a small amount of potable water, this is infinitely better than not being able to source safe water a short distance from your home.
Devices tend to fall into one of two camps — passive water extraction and forced, or powered. The first kind tends to rely on natural temperature differences rather than forcing the issue using an external power source.
Despite some of the highly sophisticated examples today, the technique of extracting water from air is actually relatively old. For example, we know that the Incas were able to sustain their cities above the rain line by collecting dew and channeling it into cisterns for later collection and distribution using rudimentary water fences. (more on those later).
Another interesting historical example is something called an "air well". Designs vary widely for these structures, and the technique is completely passive requiring no external energy source or moving parts.
One interesting example was developed by a Russian engineer called Friedrich Zibold in around 1900. Inspired by enigmatic piles of ancient stones near the ruined city of Theodosia, Zibold decided to test his hypothesis that these were ancient water-from-air condensers.
Each pile of ancient stones was found to cover roughly 9,700 feet (900 m2) and were associated with remains of terracotta pipes which apparently led to wells and fountains in the ancient city. Zibold concluded there must have been some ancient method of passivating collecting water, and set about building a modern example to test his hypothesis.
His construction was completed in around 1912, and, so it was claimed, could produce around 360 liters of water a day — but no official records are known. The base later developed a leak and the experiment was ended in 1915, before being partially demolished. The site was rediscovered in 1993 and refurbished, but found to yield considerably less water than was first claimed.
What are some examples of water-from-air technology?
We have already touched on a few older examples above, but modern AWGs tend to be a little more sophisticated. Here are some prime examples.
This list is far from exhaustive and is in no particular order.
1. Beetle-power might be the secret
Interestingly, like many things humans invent, nature has usually beaten us to it. For example, when it comes to extracting water from the air, the desert beetle Stenocara gracilipes has a rudimentary but effective mechanism for achieving this seemingly impossible task.
These little creatures live in one of the driest and most inhospitable places on Earth — the Namib Desert. In response, they have evolved a strategy to extract water from the air through an activity called "fog basking" — a behavior of the beetle whereby it leans its bumpy body into the wind, letting water droplets condense from the fog onto its body.
These droplets then drip down the beetles' wing case and are directed to its mouth. This strategy is incredibly efficient, and something that has grabbed the interest of scientists trying to find useful methods of providing clean water for water-stressed communities around the world.
By studying the beetle's anatomy in minute detail, a team of scientists have attempted to replicate its abdomen texture using 3D printing. They discovered the smaller the bumps, and the larger the number of them, the better the surface was at trapping moisture — in short, a larger surface area.
But this was only part of the story. The team discovered that the surface works best when any condensed water is rapidly drained away — which is exactly the point of the process from the beetle's point of view.
If this technique can be further refined and improved — and scaled up, it could, in theory, be used to provide a highly efficient passive method of providing clean water for some water-scarce places around the world.
2. Tsunami Product's water atmospheric water generator can produce hundreds of gallons of water
In California, Tsunami Products (a Washington-based company) has managed to design an innovative water-from-air device that, they hope, could help millions of Californians have access to clean water for pennies on the dollar.
An example of a forced condenser-type system, this device works similarly to an air conditioner. To date, examples of their device have been installed in homes, offices, ranches, and other buildings to dehumidify the air, extract water vapor, and then filter it ready for drinking.
According to the manufacturer, the device works by drawing air "through a series of condensing coils, where water vapor is cooled down sufficiently to reach the dew point. This converts water vapor into droplets."
Each unit then passes the air, and water, through a series of specially patented extraction chambers that have a range of features to further force water condensation. Any and all liquid water is then filtered for potential contaminants (like pathogens, pollen, etc) and then collected in a special storage tank ready for tapping.
The device works best in areas with high humidity, like foggy areas or coastlines, and, depending on the size of the unit, it is capable of producing between 200 and 1,900 gallons (900 and 8,600 liters) of water a day.
Sadly, these devices are not cheap and cost anywhere between $30,000 and $200,00. depending on their capacity. But that is just the start of a potential owner's financial outlay.
The unit also consumes a lot of power. However, if paired with a clean energy source such as a solar panel array, the running, and carbon, costs for the machine can be made more reasonable.
3. FIshing for water with fog nets
Another interesting technique for drawing water apparently out of thin air is the use of fine nets. Usually elevated above ground level on poles, this simple technique is used for agriculture and potable water harvesting alike.
Also known as fog nets, such devices can be made from polythene fiber cloth that catches condensed water from passing water vapor. The condensed water is then directed into collection vessels underneath the net.
While completely passive, fog nets are only able to produce a relatively limited amount of water and are usually only viable on foggy days. For this reason, this technique is normally limited to mountainous regions where warm, wet air arrives from the coast up steep slopes and cools to form dense fog.
However, a few years ago, researchers at the University of Akron, Ohio, made something of a breakthrough in this technology that could greatly improve the efficacy of such systems. They made nets out of electrospun polymers which were tangled around fragments of expanded graphite — a bit like spaghetti wound around small meatballs.
This technique greatly improves the relative surface area of the net, which allows much more water to condense on the surface for collections. The system is so efficient, according to its creators, that it could yield up to 180 liters of water per square meter every day. To put things into perspective, a regular fog net can usually produce around 30 liters per day.
4. DARPA has an interesting method of extracting water from the air in the works
DARPA is currently developing a method of extracting enough water from the air to potentially supply 150 soldiers daily. Called Atmospheric Water Extraction (AWE), the technology will be used to provide potable water for a range of, "military, stabilization, and humanitarian needs through the development of small, lightweight, low-powered, distributable systems that extract potable water from the atmosphere to meet the drinking needs of individuals and groups, even in extremely arid climates."
While still under development, current proposals include the development of a scalable sorbent material that will be able to rapidly extract water from the air in as lightweight, and energy-efficient a device as possible.
According to DARPA, "AWE will address water needs in two tracks: expeditionary and stabilization. The expeditionary unit will provide sufficient drinking water for an individual warfighter, with SWaP parameters restricted by the need for portability and operation in austere environments. The stabilization device will provide the daily drinking needs for up to ~150 people (i.e., a company or humanitarian mission), with SWaP requirements tailored to resources available to missions of that scale."
5. This atmospheric water generator is helping bring water to some of the aridest places on Earth
An octagenarian Spanish inventor, Enrique Vega, devised his own water from air machine after a serious water crisis hit Spain during the 1990s. His device works much like an air conditioner and could be used to provide clean water for people living in some of the more arid places on Earth.
The machine actively cools down ambient air to condense out clean, drinkable water. After improving his design so that it could work in higher ambient temperatures, Vega founded Aquaer in 2004 to roll out his device to paying customers.
The smallest variant of his invention is able to produce around 50-70 liters of water per day, but he has a much larger machine that can produce somewhere in the region of 5,000 liters per day.
Vega and his company have also teamed up with a non-governmental organization (NGO), Water Inception, to provide the machines to water-poor areas around the world. Recently a 500-liter capacity machine was provided to a refugee camp near Tripoli in Lebanon.
The NGO is now trying to raise funds to provide solar panels to help with the running costs of the unit.
6. This water from air machine can work 24 hours a day
A new technology devised by researchers at ETH Zurich has managed to develop a water-from-air generator that, they claim, can work all hours of the day completely passively. Deceptively simple in design, this machine makes use of a combination of special polymer and silver layers to give the glass some special properties which work to force water to condense out of the air.
The coatings are applied to glass that is housed in a special cone-shaped radiation shield that works to passively allow the glass to cool down by as much as 9 degrees Fahrenheit (15 degrees Celsius) below ambient temperature for any particular region. This creates a temperature differential which in turn causes water to condense out of the air, where the moisture is trapped underneath the cone.
To help with water collection, the team also developed a special water-repellent coating to the underside of the glass that rapidly facilitates the formation of water beads that can then run off and be collected.
According to the researchers, the entire process does not require any energy input and works great even during the day, thanks to the radiation shield.
Pilot studies showed that the device could harvest up to 1.8 fluid ounces (53 ml) of water per square foot (one-tenth of a square meter) of pane surface per hour, in ideal conditions. Not bad.
7. This moisture harvesting machine produces clean water using solar power
Another interesting water-from-air generator was recently unveiled by researchers at the University of Texas in Austin. Based on the principle of something called "super sponges", this machine uses solar power to produce drinkable water out of thin air.
The main guts of the machine are a special hydrogel and gel-polymer hybrid material that happens to be very good at retaining liquid water. Using this material, the machine is able to suck water out from the air and store it safely, ready for extraction.
When water needs to be tapped from the gel, all you need to do is heat it up.
"We have developed a completely passive system where all you need to do is leave the hydrogel outside and it will collect water," said Fei Zhao, a postdoctoral researcher and co-author of the study. "The collected water will remain stored in the hydrogel until you expose it to sunlight. After about five minutes under natural sunlight, the water releases."
Current tests of the design were able to produce around 50 liters per kg of hydrogel, which should be more than enough for most domestic applications. If commercially produced, this technique could prove to be a game-changer for many water-stressed regions of the world, especially when paired with solar power.
It could also be used to greatly improve current water harvesting techniques, making them more efficient and less energy-consuming.
Yu and his team have already filed a patent.
8. Carbon rods could be the secret to harvesting water from dry air
A few years ago, a novel technique for extracting water from the air was unveiled by Pacific Northwest National Laboratories (PNNL). Discovered completely by accident, this new technique uses carbon-based nanorods to adsorb water at low humidity.
The rods, amazingly, also spontaneously expel about half of any trapped water when the relative humidity exceeds 50-80%. The water expulsion is completely reversible and is attributed to the interfacial forces between the confined rod surfaces.
Amazingly this discovery came completely by accident as Chemist Satish Nune was studying the nanorods using a vapor analysis tool. He was surprised to find that the rods appeared to be working contrary to other water receptors as the rod assembly actually lost mass as the external humidity increased. This was obviously a surprise, but closer examination found that this odd behavior was a consequence of the variable spacing of the rods.
When humidity is low, the rods are able to maintain a relatively wide spacing between them, which allows water to stick to them. However, as humidity rises, the capillary action of water draws the rods together which, in turn, squeezes out and expels any rod-adhered water.
Interestingly, a similar process was theorized back in the 1990s, but nothing really came of it, until now. It is now hoped that this strange phenomenon can be harnessed, in some way, on a large scale for water harvesting in dry desert regions.
9. This shipping container-based machine won the Water Abundance XPRIZE
Developed by a company called WEDEW, this device won the $1.75 million Water Abundance XPRIZE back in 2018, as the most feasible solution to alleviate the world's growing water crisis. The machine is able to generate at least 2000 liters of water from the atmosphere every single day, all from organic trash.
The XPrize is sponsored by the TATA Group and Australia’s Aid Group.
Not only that, but the device costs a little over 2 cents per liter an power to run. Housed inside a shipping container, this AWG is able to generate and maintain a humid environment inside the container, while also generating clean drinking water using a device called Skywater.
Another example of an active water-from-air generator, this system uses biomass gas to produce, and sustain, a moist environment inside the container through a process called pyrolysis. Pretty much any organic waste can be added to fuel the machine including plant and animal materials, wood chips, or nutshells. As the organic material decomposes, it gives off water vapor, which is trapped in the container and extracted from the air.
Not only does the device produce potable water, but it also produces nutrient-rich waste, called biochar, that can be used as a potent natural fertilizer for crops.
9. These water bottles can refill themselves from the very air around them
Yet another interesting AWG is a self-refilling water bottle called the Fontus Airo. Ideal for people who love nothing more than the great outdoors, these bottles can refill themselves in less than an hour.
The bottles were developed by an Austrian industrial engineer called Kristof Retezár, to provide a simple method to supply safe water to water-scare regions of the world. Unlike some other solutions on this list, the technology behind the bottles is relatively simple, and, most importantly, portable.
The bottle works by allowing humid air to enter the device, whereby the air is exposed to what is termed hydrophobic "teeth". Resembling toothbrush bristles, these "teeth" force water vapor to condense out of the air to form water droplets ready for collection.
Another example of an active AWG, the power is provided by a small solar-panel rechargeable battery integrated into the device. According to its creator, the bottle is most efficient between 86 degrees Fahrenheit (30 degrees Celsius) and 104 degrees Fahrenheit (50 degrees Celsius) and between 80 and 90% humidity.
Over the course of an hour, Fontus can produce roughly 0.5 quarts (roughly 1/2 a liter) of water. Since its development, the product has been brought to market for cyclists and ramblers alike.
And that, water-from-air enthusiasts, is your lot for today. Far from the preserve of sci-fi films, like Star Wars, the technology to literally draw water from the air is a very real, and very promising field of technology for helping provide life-giving water to many parts of the world.
If warnings of an impending water crisis are well-founded, then technologies like the ones described above may prove critical to the survival of many millions of people around the world.