Drinking water from air humidity

June 5, 2009
Plants producing large quantities of drinking water from moisture in the air could look like this. Credit: Logos Innovationen

Cracks permeate the dried-out desert ground, the landscape bears testimony to the lack of water. But even here, where there are no lakes, rivers or groundwater, considerable quantities of water are stored in the air. In the Negev desert in Israel, for example, annual average relative air humidity is 64 percent - in every cubic meter of air there are 11.5 milliliters of water.

Research scientists at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart working in conjunction with their colleagues from the company Logos Innovationen have found a way of converting this air humidity autonomously and decentrally into drinkable water.

"The process we have developed is based exclusively on such as thermal solar collectors and , which makes this method completely energy-autonomous. It will therefore function in regions where there is no electrical infrastructure," says Siegfried Egner, head of department at the IGB. The principle of the process is as follows: hygroscopic brine - saline solution which absorbs moisture - runs down a tower-shaped unit and absorbs water from the air. It is then sucked into a tank a few meters off the ground in which a vacuum prevails. Energy from solar collectors heats up the brine, which is diluted by the water it has absorbed.

Because of the vacuum, the boiling point of the liquid is lower than it would be under normal atmospheric pressure. This effect is known from the mountains: as the atmospheric pressure there is lower than in the valley, water boils at temperatures distinctly below 100 degrees Celsius.

The evaporated, non-saline water is condensed and runs down through a completely filled tube in a controlled manner. The gravity of this water column continuously produces the vacuum and so a vacuum pump is not needed. The reconcentrated brine runs down the tower surface again to absorb moisture from the air.

"The concept is suitable for various sizes of installation. Single-person units and plants supplying to entire hotels are conceivable," says Egner. Prototypes have been built for both system components - moisture absorption and evaporation - and the research scientists have already tested their interplay on a laboratory scale. In a further step the researchers intend to develop a demonstration facility.

Source: Fraunhofer-Gesellschaft (news : web)

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1 / 5 (1) Jun 05, 2009
Very innovative!
However, it is not clear how the deliquescent brine will be cooled so that it's vapor pressure is less than the partial pressure of the atmospheric moisture during the scrubbing phase. I doubt the vacuum evaporative cooling will be sufficient in such a hot climate. Same cooling issues may exist for the distilled water condensed in the barometric leg.
An air conditioned lab is one thing, but what happens in the desert?

not rated yet Jun 05, 2009
moisture vaporators...
2.5 / 5 (2) Jun 05, 2009
while i am for this is areas say like make shift camps where refugees have gathered and as a aid for the red cross and the like --- I think of the effect on weather patterns and everything else to the east fo the area where water is taken from the air. Before it was desert but it was a likable dessert for the plants and animals in it not it will either grow very quickly eastward of at the least impact the precipitation in the area where it is cooler and the gathered moisture is usually rung from the clouds.

any comments
not rated yet Jun 05, 2009
moisture vaporators...

LOL, moisture farmers?
not rated yet Jun 05, 2009
El_Nose, sounds like pure non-scientific speculation to me.
not rated yet Jun 05, 2009
Maybe shadow, and finally a couple of square feet of sunpanel.
not rated yet Jun 05, 2009
deatopmg,I find your comment very thoughtful,but perhaps under very low pressure the boiling point of this humid brine is so low that only a slight rise of the temperature is needed (being very optimistic the heat of the dessert would be enough to make the water evaporate).
But how much water can one of those thing produce?
Because that "single person units and plants" doesnt like like they'll be little.
not rated yet Jun 06, 2009
el_nose could have a valid point only articulated in the wrong way. take the animals and plants out of the equation a second (which too are valid points to me)
i can definitely see where hes going with this...

if an area over a land mass averages say 1" of rain per year..if you then suck the additional moisture from the air in that locale, thereby decreasing the rate of evaporation of water into the clouds, you should logically lower the rainfall even further, and the amount of decrease being directly proportional to the amount of water taken from the air in that area.

i will say, the thing here not being taken into consideration is the fact that clouds circulate/move at different rates...therein it may not effect just the areas to the east of the air dryed locations :)
5 / 5 (1) Jun 07, 2009
I like this idea. Put hundreds of them all over the west so that the air becomes drier and I have more wildfires to fight!
not rated yet Jun 07, 2009
Wouldn't the water just be evaporated after it is used anyway?
not rated yet Jun 11, 2009
Regarding effects on downwind deserts and plant life... Let's see. Say eg. a series of these were set up 100 meters apart to capture 24,000 kg / day (1,000 kg / hr) water each in an area with an average windspeed of 10 kph. Each one will affect a volume of 1/10 x 10 x 5 = 5 cu km air / hour.

Assume initial air conditions 30 degC, 20% RH. Each 100 cu m of air will contain 3 x .2 = 0.6 kg water. The total water content of the 5 cu km of air is 5x10^6 x 0.6 = 3x10^6 kg. The unit will extract 1 x 10^3 kg, or 1/3,000th of the air's water content. 0.03%
5 / 5 (1) Jun 11, 2009
Sorry, error.

The total water content of the 5 cu km of air is 5x10^6 x 0.6 / 100 = 3x10^4 kg. The unit will extract 1 x 10^3 kg, or 1/30th of the air's water content. 3%

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