Low-cost gel film can pluck drinking water from desert air
news.utexas.edu
news.utexas.edu
"Before the water vapor sorption measurement, all samples are dried in a vacuum oven at 90 °C for at least 2 h. "
- Fridge cooling
- liquid nitrogen bath
- 12h freeze drying
That doesn't sound low-cost / easy to manufacture.
https://www.nature.com/articles/s41467-022-30505-2
Figure of test rig: https://www.nature.com/articles/s41467-022-30505-2/figures/4
That looks like you capture using a very cold, porus material (cold, dry sponge that collects dew, essentially), then heat this "sponge" so the water then travels up to a condenser which causes it to "dew" and run into a collection chamber.
It's not magic water-cloth, and I don't think it's a weekend project, but it's pretty low tech.
What did I get wrong? I'm sure there's something.
> The mesh netting is where the condensation of water droplets appear. It consists of filaments knitted together with small openings, coated with a chemical to increase condensation. Shade Cloth is used for mesh structure because it can be locally sourced in underdeveloped countries. The filaments are coated to be hydrophilic and hydrophobic, which attracts and repels water to increase the condensation.[1] This can retrieve 2% of moisture in the air. Efficiency increases as the size of the filaments and the holes decrease. The most optimal mesh netting is made from stainless steel filaments the size of three to four human hairs and with holes that are twice as big as the filament. The netting is coated in a chemical that decreases water droplet's contact angle hysteresis, which allows for more small droplets to form. This type of netting can capture 10% of the moisture in the air.[2]
It’s certainly an interesting technology and achievement but one that could be easily misused with “unintended consequences”; or so it seems.
When reading through the article, it has potential application in areas where a local water supply may not be clean enough to drink or lacks sufficient water treatment & filtration.
In many industries this airborne salt can cause corrosion. Talk to anyone with a classic car in LA/SF, both cities with sea breezes. They don't want to leave them outside too much. That's why the aircraft "boneyards" are all in the interior, across the mountains from the sea.
Strong Dune vibes.
You could use these to water plants and set up a cycle where a significant portion of the water lost through evaporation was reclaimed and gradually accumulated locally. Dot a landscape with solar powered stacks of these things feeding appropriately selected plantations and you might make the desert bloom or help prevent the spread of deserts.
I don't have faith gov't will do it either. Those opposed to climate change will argue it is money spent on fake science. It'll die in congress (for US, s/congress/localGovUselessBody/ for other places).
Someone might get popular enough to crowd source fund it with an NGO type thing, but I'm not holding my breath there either.
I think you'd be hard pressed to find organic opposition to tackling environment issues that aren't related to the relatively abstract C02 pollution issues. I say organic because the corporations responsible for pollution will always find ways to manufacture consent that protects their own best interests. But, your stereotypical human-caused climate change denier is likely someone that hunts, fishes, or resides in a rural area, where environmental and conservationist concerns are taken very seriously, regardless of political affiliation. Your opposition is only going to come from people whose livelihood is affected by pollution controls. A broader swathe of people will always oppose addressing C02 related climate concerns because it affects literally everyone's bottom line in the form of rising cost of goods with energy prices going up, and it has abstract consequences, rather than concrete ones like your local streams being poisoned, or your well water going bad because the aquifer has been contaminated.
There are plenty of desert coastlines.
Not sure how much that would cost per square meter of forest/agriculture, tbh.
Solar powered desal is pretty expensive.
At 15% relative humidity, then, you can extract a maximum of 0.15 x 17.3g = 2.6g from every 1,000L of air.
If a person needs 5L/day for survival (I am making this up), then you’d need to dry out 5000 / 2.6 = 1,923L of air each day — that’s just short of two cubic meters…
If the density of people living in an area is 50 per square km, drying the air out to extract water would deplete the first meter of the atmosphere by 10%.
You made a unit conversion mistake there. It's 1923 cubic meters, not liters.
I was curious so I looked it up because I also did not know, ref: https://www.google.com/search?q=liters+in+cubic+meter&oq=lit...
Okay let’s say the bottom 10m of atmosphere is available for water making. That means there are 10 million cubic meters of air per square km, or per 50 people. We will need to dry out 1,923 x 50 = 96,150 cubic meters of air. But there is 10,000,000 available, meaning we are only drying out just under 1% of the air.
https://collaboration.cmc.ec.gc.ca/science/rpn/SEM/dossiers/...
It's infuriatingly hard to find good citations, but I think they actually mostly breathe it out. IIRC, the water breakdown for some (spacecraft) life support system was something like 50% from respiration, 30% in urine, 10% in sweat, and 10% in feces.
I suspect that if you think that this is going to give us the ability to suck out all the water out of thousands of cubic kilometers of desert air any time soon, you're probably being a little too optimistic.
Wikipedia speaks of an "abrupt desertification" 5400 years ago.
It's worth noting that sea level rise is kinda complex.
First, if an iceberg floating on the ocean melts it doesn't raise sea levels. That's the buoyancy principle of displacing an object's weight in water.
Second, a lot of ice (eg Antarctica, Greenland) is on land so the first point doesn't apply to all ice as some deniers have tried to claim.
Third, the sea level rise is partially from ice melt but also from thermic expansion.
Fourth, even if you flooded all the below sea level parts of the world, it would only account for a fraction of the sea level rise so it's not a permanent solution.
But several thousand eyars ago the Sahara was arable land. Some parts of the Sahara were >400 feet below sea level so this would be a significant body of water. Even as seawater this would inject a lot of water into the environment through evaporation and normal water cycles.
Obviously this would have an impact on the ecosystem and displace some people but we've displaced far more people for less (eg the Three Gorges Dam).
This seems like something we should do, no?
Then the humidity would trigger rains and help grow a vegetation, and the salt residues would remain inside the canals.
Then at some point the vegetation would self-maintain the necessary humidity level.
Years ago I read about a system that seemed successful. Ridges were built up at the desert’s edge, and salt-tolerant trees and shrubs were planted on hem to keep the ground stable. This change in microclimate promoted more greening in the valleys between, which increased overall moisture levels. Once this is established, more ridges can be constructed further out to repeat the process. It’s not an easy thing to search the web for, and I don’t recall how long it takes for one ridge to be productive, but I recall thinking it was shorter than I expected (still on the order of years, of course).
Not necessarily, given the weather conditions there it's quite plausible that all the evaporation would form clouds which would only rain elsewhere and not in that desert.
From what I just read up on, the Salton Sea over the millennia would periodically flood, become a small lake or dry out to desert levels. The change that occurred was that humanity changed the rhythm of this artificially to a 'flood it' state for a prolonged period of time.
They are now complaining that when they changed it to the 'small lake' state again, well, shrinking lakes create a certain situation.
The problem I do see is really the way the 'flood' state was created and other usages of the lake. Runoff from agriculture with way too much fertilizer, waste dumping etc. and now they wonder why the dust is toxic and stinks.
How would that apply to flooding the Sahara w/ sea water perpetually?
But what about ice that is 'on land' but also below sea level? Iirc roughly half of Antarctica's glacier ice is sitting dry ground that is below sea level. Whether melting that ice will raise or lower sea levels is more complicated, with variables for amounts above/below various points.
I think the desert status of the Sahara has more to do with a combination of oceanic gyre patterns and the structure of the Hadley circulation. The Sahara and other latitudes around 30N are constantly under a high-pressure zone of descending hot dry air which is part of the northern Hadley cell. The exception is over India where the Eurasian landmass pulls the ITCZ (ascending side of the Hadley cell) way far North and causses the monsoons.
I don't think flooding the Sahara would change its aridity any more than the Arabian peninsula, despite being surrounded by water, is still a desert away from the immediate coastline. It's a matter of air moisture, not sea or ground moisture. You could try irrigation, though. The Libyans abortively tried that under Gaddhafi.
>don't think flooding the Sahara would change its aridity any more than the Arabian peninsula
There's something to be said about the lake effect. It certainly happens in U.S and Canada where areas just east of the Great Lakes get much more precipitation than other parts
As for the rain in Saudi Arabia, there is a mountain range along the coast south of Mecca, and I think the area gets rain because of orographic uplift. When the wind blows across the Red Sea it does pick up a lot of moisture, just not enough to cause rain, because the air is so hot and can hold so much moisture overall. But it gets forced up over the mountains, cools, and passes saturation humidity, and the excess water becomes rain. You can see where the mountain range ends on an annual precipitation map of SA.
Sorry to rain on your parade.
Anticipating the impact is probably a fool's errand, since climate is extremely complex and changes on one part of the world affect others. It's not just about displacing people in the area, you risk altering the patterns that bring rain to places as far as Germany or help grow crops in Brazil. Sahara sand plumes play a role in replenishing phosphates in the Amazon, for example. Even blanketing some parts with solar panels will probably alter global weather patterns significantly.
https://en.wikipedia.org/wiki/Qattara_Depression_Project
It would have provided hydroelectric power and as the water evaporated and formed clouds it may have increased rainfall.
The United States wanted to use nuclear bombs to excavate the channel to the Mediterranean Sea.
Consequently, use of nuclear explosives to excavate the canal was another proposal by Bassler. This plan called for the detonation in boreholes of 213 nuclear devices, each yielding 1.5 megatons (i.e. 100 times that of the atomic bomb used against Hiroshima). This fit within the Atoms for Peace program proposed by President Dwight Eisenhower in 1953. Evacuation plans cited numbers of at least 25,000 evacuees.
Project Plowshare was pretty crazy. Use nuclear bombs for excavation. There were ideas to create artificial harbors by using a bombs.
Extracting ubiquitous atmospheric water is a sustainable strategy to enable decentralized access to safely managed water but remains challenging due to its limited daily water output at low relative humidity (≤30% RH). Here, we report super hygroscopic polymer films (SHPFs) composed of renewable biomasses and hygroscopic salt, exhibiting high water uptake of 0.64–0.96 g g−1 at 15–30% RH. Konjac glucomannan facilitates the highly porous structures with enlarged air-polymer interfaces for active moisture capture and water vapor transport. Thermoresponsive hydroxypropyl cellulose enables phase transition at a low temperature to assist the release of collected water via hydrophobic interactions. With rapid sorption-desorption kinetics, SHPFs operate 14–24 cycles per day in arid environments, equivalent to a water yield of 5.8–13.3 L kg−1. Synthesized via a simple casting method using sustainable raw materials, SHPFs highlight the potential for low-cost and scalable atmospheric water harvesting technology to mitigate the global water crisis.
> The research builds on previous breakthroughs from the team, including the ability to pull water out of the atmosphere[1] and the application of that technology to create self-watering soil[2]. However, these technologies were designed for relatively high-humidity environments.
1: https://news.utexas.edu/2019/03/13/solar-powered-moisture-ha...
2: https://news.utexas.edu/2020/11/02/self-watering-soil-could-...
> renewable cellulose and a common kitchen ingredient, konjac gum, as a main hydrophilic (attracted to water) skeleton
(artificial sponges are made of cellulose - I learned this just last year when washing my dishes and thinking... wtf is this made of?)
---
Seems then you can:
0. Go to the dollar store
1. Buy a thin sponge
2. Buy konjac gum
3. Buy a tray
4. Place the thin sponge in the tray, mix the konjac gum with water, and pour it into the tray, and place it into your freezer, waiting for the water to evaporate...?
5. Place it now somewhere in a humid place to pull the water out of the air
---
Industrial version of this is probably a ton of thin wafers side-by-side in a cube-like fashion, so they can easily come off an assembly line
> In a typical fabrication, LiCl powder (0.32–0.82 g) is added into 10 mL HPC solution (0–2.0 wt%) forming solution A. The pH of solution A can be tuned by NaOH or HCl solution. 0.44 g KGM powder is added into solution A and quickly cast into the petri dish after vortex. The gelation takes place within 2 min, and sit in room temperature for 15 min. Then, the film is placed in the fridge (−4 °C) for 3 h followed by 15 min freeze in liquid nitrogen. Last, the gel film is ready to use after 12 h freeze-drying.
Edit:
> Another designed component, thermo-responsive cellulose with hydrophobic (resistant to water) interaction when heated, helps release the collected water immediately so that overall energy input to produce water is minimized.
"The team developed a low-cost gel film made of abundant materials that can pull water from the air in even the driest climates. The materials that facilitate this reaction cost a mere $2 per kilogram, and a single kilogram can produce more than 6 liters of water per day in areas with less than 15% relative humidity and 13 liters in areas with up to 30% relative humidity."
Doesn't seem like this would be used for agriculture at scale - but it sure could beat digging a well to get water for a house.
"The salt mentioned is not table salt, but lithium chloride. Lithium chloride - which makes up a half by weight of the film, and is also in obvious demand for batteries, is $70/kg or so in bulk."
I haven't really dug in deep myself, but this is the comment that deflated me when reading about this yesterday, so worth looking into at least imo
The ground isn’t all that dry, you can dig a hole, cover it with plastic and get enough water through evaporation/ condensation to hopefully not die of dehydration if you get stranded in the desert.
Something like this would be very helpful for troops in the desert since water is heavy and resupply is very critical to keep up combat readiness. Back when I was a “speed bump in the sand” they drove us out into choke points in the Saudi desert to take out a few Iraqi tanks before they overran us in case of invasion. Assuming we were able to somehow escape contact our mission was to then try to make it to the coast and steal a boat through we probably wouldn’t have had enough water to accomplish the second part. Not even exaggerating a little bit, such is the life of a paratrooper.
But what’s the total yield for the $2? In other words single or multiple use?
In some areas of the world there’s a serious fresh water crises. Very poor people are left buying expensive bottled water to avoid disease.
The linked self-watering soil article [1] makes me wonder if the material could be used to reverse desertification.
[0] https://wahainc.com//smithsonian [1] https://news.utexas.edu/2020/11/02/self-watering-soil-could-...
What's the catch?
Wide scale harvesting of water from the air will change the local climate in unpredictable ways?
There's quite a number of inventions and breakthroughs that looked great in the lab but never made it to real world applications.
Remains to be seen if this approach can work in practice and at scale and what the real-world implications would be.
I cant see this scaling. There is not much water to collect to begin with.
A person using it sure. A platoon sure.
But if a city of 2000 people started using I cant see it working well.
Further the moisture extracted from the air in that city would mean even drier air in other places?
I imagine moisture from other places would simply travel to his low humidity place to replace the one taken out. Should be limitless.
Now I’m wondering if you could use this stuff like crazy in hot, humid places and whether (a) it could pull enough water to be useful for drinking or irrigation, and (b) whether it’s possible to “locally” lower the ambient humidity (like the reverse of the urban heat island effect).
According to the paper, they use heating (60°C) to extract the water. In hot environments, however, ambient temperatures get quite close to that already (see India at the moment).
The answer to b) would be a no. The technique doesn't work in high humidity environments.
If so, then I'm smelling a plausible solar-powered, cheap, modular "emergency life support" system for people threatened by extreme web bulb temperature conditions.
In conclusion, if the environment is 50°C or hotter, the sponge cannot absorb much water from the atmosphere, because the kinetics imply that the water would evaporate too quickly.
“konjac gum” a common kitchen ingredient, eh? Let me just check my pantry. Odd, seems I am fresh out.
Would this be viable in a Window Casing/Screen? system where-by you have, instead of a "screen" you have this mesh - then with a window moulding application that funnels the water to either an "ITS ALL PIPES" type of reclaimation.....
My question is can this process be scaled to the point of replacing the standard desalinization plant?
https://www.scientificamerican.com/article/slaking-the-world....
Fremen Inc.