# Again about water - water from air?



## sci (Apr 18, 2017)

The more I am reading about water gathering, more I am interested in gathering water from air. If it is clear enough to brethe it, the water extracted from air will be clear enought for drinking. WIthout minerals, but as a life-saving liquid should be OK. The question is - how? There are few ways I have found, the most effective from which is the active water condensation - shortly an electrical dehumidifier + water filtration system. The issues I see are:
- The off-the-shelf dehumidifiers are not designed to produce clean water. The materials used do not have any intention to keep the water clean from contamination coming from the machine. Aluminium, lead and anything else of this sort comes in mind;
- In real SHTF situation, the electricity will be short, if any - and it is needed for the dehumidifier.
Does anybody know some other practical way to get (let´s say 6-8 liters a day) in any time of the year - which is a norm for the electrical/condensation dehumidifiers?


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## rstanek (Nov 9, 2012)

Am I missing something here, water from the air? I thought that was rain.....


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## sci (Apr 18, 2017)

I don't mean rain water. I mean extracting the water from the humid air via condensation - you know, like if you exhale in front of a mirror or glass, the humidity from you breath condensates to water drops on the cold surface of the glass. The same with air - practically any air we breathe contains water. Via heating it and directing it to a cold surface, you can gather the condensated water drops. In the dehumidifiers there is a kind of fridge, which takes care to make the "cold" surface... well, cold. It is in addition a radiator, in order to have as much surface as possible in such a compact device. But that is detail - long story short: I have really doubts to use the water, even after filtration with sawyear, for drinking. The materials used in the commercial dehumidifiers are just not taken to deal with water for drinking...


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## Kauboy (May 12, 2014)

Water from the air would be quite inefficient. There just isn't much of it in most places to do any real good. It's far more effective to just let the sun do the job for you, and catch the condensate when it comes falling back down.

Now, extracting it from the ground is a different story. If the soil is moist, it is holding quite a bit of water, and a solar still over a hole could collect far more with less effort than trying to get it out of the air.

I'm curious why you think using a Sawyer would not be sufficient for a normal water source.
Unless you have reason to believe the the water is chemically contaminated, a Sawyer would take care of most biological contaminants.


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## KUSA (Apr 21, 2016)

You want water from air? Here you go.

https://m.phys.org/news/2017-04-device-air-powered-sun.html

Imagine a future in which every home has an appliance that pulls all the water the household needs out of the air, even in dry or desert climates, using only the power of the sun.

That future may be around the corner, with the demonstration this week of a water harvester that uses only ambient sunlight to pull liters of water out of the air each day in conditions as low as 20 percent humidity, a level common in arid areas.

The solar-powered harvester, reported in the journal Science, was constructed at the Massachusetts Institute of Technology using a special material - a metal-organic framework, or MOF - produced at the University of California, Berkeley.

"This is a major breakthrough in the long-standing challenge of harvesting water from the air at low humidity," said Omar Yaghi, one of two senior authors of the paper, who holds the James and Neeltje Tretter chair in chemistry at UC Berkeley and is a faculty scientist at Lawrence Berkeley National Laboratory. "There is no other way to do that right now, except by using extra energy. Your electric dehumidifier at home 'produces' very expensive water."

The prototype, under conditions of 20-30 percent humidity, was able to pull 2.8 liters (3 quarts) of water from the air over a 12-hour period, using one kilogram (2.2 pounds) of MOF. Rooftop tests at MIT confirmed that the device works in real-world conditions.

"One vision for the future is to have water off-grid, where you have a device at home running on ambient solar for delivering water that satisfies the needs of a household," said Yaghi, who is the founding director of the Berkeley Global Science Institute, a co-director of the Kavli Energy NanoSciences Institute and the California Research Alliance by BASF. "To me, that will be made possible because of this experiment. I call it personalized water."

Yaghi invented metal-organic frameworks more than 20 years ago, combining metals like magnesium or aluminum with organic molecules in a tinker-toy arrangement to create rigid, porous structures ideal for storing gases and liquids. Since then, more than 20,000 different MOFs have been created by researchers worldwide. Some hold chemicals such as hydrogen or methane: the chemical company BASF is testing one of Yaghi's MOFs in natural gas-fueled trucks, since MOF-filled tanks hold three times the methane that can be pumped under pressure into an empty tank.

Other MOFs are able to capture carbon dioxide from flue gases, catalyze the reaction of adsorbed chemicals or separate petrochemicals in processing plants.

A schematic of a metal-organic framework. The lines in the models are organic linkers, and the intersections are multi-metallic units. These are building blocks that Omar Yaghi stitches together into crystalline sponges using new reticular chemistry. The yellow balls represent the porous spaces that can fill up with water. The background image shows the many cyrstals of MOF that are combined in the water harvester. Credit: UC Berkeley and Berkeley Lab
In 2014, Yaghi and his UC Berkeley team synthesized a MOF - a combination of zirconium metal and adipic acid - that binds water vapor, and he suggested to Evelyn Wang, a mechanical engineer at MIT, that they join forces to turn the MOF into a water-collecting system.

The system Wang and her students designed consisted of more than two pounds of dust-sized MOF crystals compressed between a solar absorber and a condenser plate, placed inside a chamber open to the air. As ambient air diffuses through the porous MOF, water molecules preferentially attach to the interior surfaces. X-ray diffraction studies have shown that the water vapor molecules often gather in groups of eight to form cubes.

Sunlight entering through a window heats up the MOF and drives the bound water toward the condenser, which is at the temperature of the outside air. The vapor condenses as liquid water and drips into a collector.

"This work offers a new way to harvest water from air that does not require high relative humidity conditions and is much more energy efficient than other existing technologies," Wang said.

This proof of concept harvester leaves much room for improvement, Yaghi said. The current MOF can absorb only 20 percent of its weight in water, but other MOF materials could possibly absorb 40 percent or more. The material can also be tweaked to be more effective at higher or lower humidity levels.

"It's not just that we made a passive device that sits there collecting water; we have now laid both the experimental and theoretical foundations so that we can screen other MOFs, thousands of which could be made, to find even better materials," he said. "There is a lot of potential for scaling up the amount of water that is being harvested. It is just a matter of further engineering now."

Yaghi and his team are at work improving their MOFs, while Wang continues to improve the harvesting system to produce more water.

"To have water running all the time, you could design a system that absorbs the humidity during the night and evolves it during the day," he said. "Or design the solar collector to allow for this at a much faster rate, where more air is pushed in. We wanted to demonstrate that if you are cut off somewhere in the desert, you could survive because of this device. A person needs about a Coke can of water per day. That is something one could collect in less than an hour with this system."


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## Smitty901 (Nov 16, 2012)

Does the EPA own all water that is in the air or only that that hits the ground. Collection methods we used in dessert training were slow and produced very little water. 
Kind of like stealing it from the air before it rains.


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## SOCOM42 (Nov 9, 2012)

In a SHTF situation, a solar collector is the only viable method, and moist ground is needed for any volume, not just survival..

The power to drop the evaporator temp below the dew point would be impossible to get, post SHTF.

It works but is too power dependent and the net results to small.

To get 4 liters a day would require a huge system.

This is why you don't see any systems available or commercial plant in this manor.

If you have an air conditioner see how much comes from it while running, it will give you a good idea of the volume vs, power.

I am lucky, I have an over abundance of water around me.

The perceived problem with the system @KUSA posted is the particulate contamination of the microcrystaline matrix.

MIT has some of the greatest research, but it is a long journey from lab to commercial application.

I was involved with a similar project stripping gasses from an effluent stream.


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## Medic33 (Mar 29, 2015)

their used to be a thing called an air well -but it only produced like a cup of water a day.
basically the more humid the more water I guess not sure if it was real or just a joke or something but it looked like it would be a must have prep item -me I live in place that has more water than anyone would need and so far this year I think it might be a problem it has rained almost every day for about a month now.


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## sci (Apr 18, 2017)

I have a dehumidifier working in my basement to keep the humidity at about 50-55%. The thing is able to extract several liters a day (the capacity according the datasheet is 20L a day, but in maximal conditions, which i assume is something like 90%) from this already closed volume. A humidifier like this costs less than 200EUR and consumes 200 to 300 Watt. Most of them operate internally on 24V DC or something, so powering with solar/wind source isn't unreal. My concern is the contamination comming from the machine itself.
- Sawyer is a great filter, but I have doubts using it to filtrate the water from dehumidifier. I find is also pity, that I ak supposed to filtrate from source, which is a part of the system. The contamination in this case is avoidable, but not easy- you need to replace some parts with such made of stainless steel, glass, HD polimers, etc.
- Gathering water vrom soil is more effective, than from air, but eventual contamination is soil is more long-lasting than in air, due to the circulation difference. And as I said, you are already exposed to that same air to breath. If soil, than a normal weel will be even more effective 
I was asking if someone have some info for a practical application, how you can DIY a device to use it in reality. Developments like this from MIT are great, but unfortunately far from accessible.


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## sideKahr (Oct 15, 2014)

This passive method is similiar to, but not exactly, gathering water from air:

Transpiration Water Gathering

Water can be obtained by placing clear plastic bags over the leafy branch of a non-poisonous tree and tightly closing the bag's open end around the branch. During photosynthesis plants lose water through a process called transpiration. A clear plastic bag sealed around a branch allows photosynthesis to continue, but traps the evaporating water causing the vapor pressure of water to rise to a point where it begins to condense on the inner surface of the bag. Gravity then causes the water to run to the lowest part of the bag, where it can be collected.

- from Wikipedia "Solar Still"


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## Urinal Cake (Oct 19, 2013)

The Israelis (of course) developed an efficient system

gOOGLE: water collection from the air devices in Israel

Water-Gen machine can pull water out of the air - Business Insider


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## Redneck (Oct 6, 2016)

SOCOM42 said:


> The perceived problem with the system @KUSA posted is the particulate contamination of the microcrystaline matrix.


As I read this, my first thought was this sounds like something from Star Trek, Scotty.


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## sideKahr (Oct 15, 2014)

******* said:


> As I read this, my first thought was this sounds like something from Star Trek, Scotty.


Dune. The Fremen on Arrakis used windtraps to collect water from desert air.


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## SOCOM42 (Nov 9, 2012)

@sideKahr, been into the spice, much?

Yes the technology is there, as I said it requires power to operate in most cases.

The power will be the problem in SHTF.


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## sideKahr (Oct 15, 2014)

@SOCOM42 He who controls The Spice controls the universe!


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## SOCOM42 (Nov 9, 2012)

sideKahr said:


> @SOCOM42 He who controls The Spice controls the universe!


I have blue eyes, does that give me a head start?

I have a thumper.


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## sideKahr (Oct 15, 2014)

@SOCOM42 I have a thumper, too, but let's not go there...this is a family place.


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## paraquack (Mar 1, 2013)

Down here in southern AZ, I think I might have a problem.


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## sideKahr (Oct 15, 2014)

paraquack said:


> Down here in southern AZ, I think I might have a problem.


Build that wall...build that wall. If you build it high enough, you'll get a snowcap. Problem solved!


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## Smitty901 (Nov 16, 2012)

sideKahr said:


> @SOCOM42 He who controls The Spice controls the universe!


Still have a copy of that movie here some where.
Great thing about Wisconsin Water we have enough to last until the end and then some. Don't even have to pump some of it comes up on it's own.


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## SOCOM42 (Nov 9, 2012)

Smitty901 said:


> Still have a copy of that movie here some where.
> Great thing about Wisconsin Water we have enough to last until the end and then some. Don't even have to pump some of it comes up on it's own.


Movie just ended at 6 here.

Low water table here is 3 feet down, high is 1 foot above ground.

River behind and a lake in front.


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## Smitty901 (Nov 16, 2012)

SOCOM42 said:


> Movie just ended at 6 here.
> 
> Low water table here is 3 feet down, high is 1 foot above ground.
> 
> River behind and a lake in front.


 We have springs here no real flood issues . Wisconsin for what ever reason was blessed with a lot of good ground water supply. By my one sons house they have great water, but it is 400 feet down.


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