Device Pulls Water From Dry Air, Powered Only By the Sun

[DetlefK]

http://www.kavlifoundation.org/kavli-news/device-pulls-water-dry-air-powered-only-sun#.WPYx-2dCSUm



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.

...

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.

...

“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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- The size and weight of a toaster.
- Can harvest enough water from fairly dry air to keep you alive.
- No electricity, no batteries, no solar-cells. Only needs strong sunlight.

[HoneyBadger]

1. Overthinking

Try this the next time you are in the desert and you do not happen to have this device with you. Dig hole. Put water can in hole. Put plastic sheet over hole. Put rock in middle so condensation drips into can.

[DetlefK]

2. How much water does this yield?

[HoneyBadger]

4. 6'x6' plastic yields a quart a day from the ground

You can add to that by putting a container of urine under there as that process will recover all potable water from the urine. If you have a static location and enough plastic, you can dig a much larger hole with proportional yield.

[Arkansas Granny]

5. It's known as a solar still. This seems to be a pretty good article.

http://www.desertusa.com/desert-people/water-solar-still.html

It can also be used to purify tainted or questionable water.

[muntrv]

3. Didn't Luke Skywalker have these at his home on Tatooine?

[DetlefK]

9. Yes, but their name doesn't come to my mind. Something with "evaporators", I think.

And I remember that they had to be cleaned regularly or mold would grow on them.

[DetlefK]

10. Found it. The real-life version is better.

http://starwars.wikia.com/wiki/Moisture_vaporator

coaxed moisture from the air by means of refrigerated condensers

The article from the OP states that this method has horrible efficiency at low humidity.

Vaporators were capable of collecting 1.5 litres of water per day, even when the relative humidity of the air was only 1.5 percent.
I think, with some optimization we could get there in real life.

[byronius]

6. Very cool. Large output.

[Judi Lynn]

8. A life-saving discovery. How wonderful is this? Thank you. n/t