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Earth Science Technology

New Solar-Powered Device Can Pull Water Straight From the Desert Air (sciencemag.org) 202

sciencehabit quotes a report from Science Magazine: You can't squeeze blood from a stone, but wringing water from the desert sky is now possible, thanks to a new spongelike device that uses sunlight to suck water vapor from air, even in low humidity. The device can produce nearly 3 liters of water per day, and researchers say future versions will be even better. That means homes in the driest parts of the world could soon have a solar-powered appliance capable of delivering all the water they need, offering relief to billions of people. To find an all-purpose solution, researchers led by Omar Yaghi, a chemist at the University of California, Berkeley, turned to a family of crystalline powders called metal organic frameworks, or MOFs. Yaghi developed the first MOFs -- porous crystals that form continuous 3D networks -- more than 20 years ago. The networks assemble in a Tinkertoy-like fashion from metal atoms that act as the hubs and sticklike organic compounds that link the hubs together. By choosing different metals and organics, chemists can dial in the properties of each MOF, controlling what gases bind to them, and how strongly they hold on. The system Wang and her students designed consists of a kilogram of dust-sized MOF crystals pressed into a thin sheet of porous copper metal. That sheet is placed between a solar absorber and a condenser plate and positioned inside a chamber. At night the chamber is opened, allowing ambient air to diffuse through the porous MOF and water molecules to stick to its interior surfaces, gathering in groups of eight to form tiny cubic droplets. In the morning, the chamber is closed, and sunlight entering through a window on top of the device then heats up the MOF, which liberates the water droplets and drives them -- as vapor -- toward the cooler condenser. The temperature difference, as well as the high humidity inside the chamber, causes the vapor to condense as liquid water, which drips into a collector. The findings were published in the journal Science.
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New Solar-Powered Device Can Pull Water Straight From the Desert Air

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  • by Anonymous Coward on Friday April 14, 2017 @06:11AM (#54233407)

    Sounds a bit like a windtrap. Can sietchs and spice-harvesting be far off?

  • Some other projects (Score:5, Interesting)

    by AHuxley ( 892839 ) on Friday April 14, 2017 @06:16AM (#54233415) Journal
    Fog collection https://en.wikipedia.org/wiki/... [wikipedia.org]
  • I gave TFA a cursory glance only, so sorry if ghis has been answered.

    How large is this thing?
    And I assume the water it produces is akin to distilled water. Isn't that bad to drink?

    • Re: A few questions (Score:3, Interesting)

      by Anonymous Coward

      Yes no, it is bad if you dont have a source of salts.

      Thats why the sami here drinks coffe with salt in it. When they are going in the moantins and only get water from snow you ad salt the same applies here

    • It's a prototype and TFA says it only has 1kg of material so it would be fairly small. This thing is producing a lot of water for 1kg.

      • It's a prototype and TFA says it only has 1kg of material so it would be fairly small. This thing is producing a lot of water for 1kg.

        It also say 'spread in to a thin sheet'. So it would be huge. And why do you consider it a 'lot of water' for 1kg?

    • Re:A few questions (Score:5, Interesting)

      by Baron_Yam ( 643147 ) on Friday April 14, 2017 @09:46AM (#54234091)

      > I assume the water it produces is akin to distilled water. Isn't that bad to drink?

      Yes. A lot of the human digestive tract works by osmosis. Putting distilled water through it means it's going to reverse, and rather than your body absorbing a lot of important things, it's going to be dumping them - presumably into your stool.

      I don't imagine hardening water to healthy levels will be all that difficult... the question is, can you make it inexpensive, robust, and foolproof enough for the type of applications this device (if it works and is practical) would see.

      Continual consumption of distilled water is bad for your heart, nervous system, and immune system - but it takes fair while, and there are other ways to get minerals and other things you might normally get from water... mainly *eating* them. Still, it would be an additional concern that you otherwise wouldn't even have to think about.

      • I remember reading about how the Sauds and other countries in that region take relatively deionized water that was distilled or from their desalination plants, and add the needed trace amounts of minerals fo it, so it would be suitable and healthy for drinking.

        If distilled water becomes common, I can see a company like Nuun making fizzy tablets which dissolve in water to give the needed minerals, and perhaps some useful vitamins as well.

      • by skids ( 119237 )

        Well, if you only drink gatorade you made from it, it should be fine... well except for the calcium. I heard distilled water can be hard on your teeth for lack of it.

      • by SEE ( 7681 )

        Aquifers under deserts tend to have rather saline groundwater, to the point the issue is often reducing the salt content enough to be potable. A supply of distilled water would be quite easy to handle; you just blend it with the water you're already drawing from wells.

      • shipping salt tablets (or whatever) is vastly easier than shipping water.

    • Better yet, do they have a working, of sorts, prototype?
  • by Opportunist ( 166417 ) on Friday April 14, 2017 @06:26AM (#54233443)

    There have been a few, let's say, shady promises about extracting water from air, mostly coupled with crowdfunding campaigns (gee, why could that be?). Those that actually delivered a product were mostly ridiculous, provided you were not one of those duped into backing it. Then it was more a reason for anger and disappointment.

    Most actually never delivered. Which reminds me, wasn't Fontus [fontus.at] due to deliver right now in April? Any backers here, did they actually deliver? Because, let's put it careful, I'd really, really love to see that!

    So don't get me wrong when I don't hold my breath. I have been promised easy water from thin air before. And what has been delivered so far, if anything, was ridiculous. Either it didn't work, didn't scale past proof-of-concept scale or only worked if the humidity was high enough that rain was more the rule than the exception, rendering a system that extracts water from the air redundant: A bucket would do.

    • Re: (Score:3, Insightful)

      by Anonymous Coward

      The crowdfunded examples all had glaring issues that they needed to break the laws of physics to work as stated, had no working prototype, and made excessive claims

      This has the advantage of not breaking any laws of physics, having a working prototype, and making claims that are reasonable

      3 liters of water in 12 hours is not excessive for either humid air or a lot of energy, all they have done is use a new (but already tried method) of doing this, the airflow is low, and the energy usage looks reasonable

      It i

      • Let's put it that way: I know how much water my air condition condenses in 12 hours. Yes, 2-3 liters in half a day is very possible. In a sweltering atmosphere with a humidity that reaches the 80% easily, 100F and an air condition with 8000 btu.

        • Plus your airconditioner doesn't run on solar power.
          • by Lumpy ( 12016 )

            IT can, and quite easily. 1000 watts of solar is not that hard to achieve

            • by Jhon ( 241832 )

              " 1000 watts of solar is not that hard to achieve"

              neither is 10,000. You just need a lot of surface area.

              1000 is about 5.5 square meters -- and that will produce about enough water for 1 person per day -- to drink -- never mind tending to food (livestock or crops). Unless we're planning on building a subterranean society of Morlocks living under miles of solar panels I don't think we're at the point where this is practical for anything more than off-grid outback living or helping out small communities of

          • It could, technically. The solar panels to do so would probably black out the Sahara, but technically...

            • Not really a window airconditioner running on a 15 amp(generally 12 amp) and 120 volts has a max 1200watt draw.

              1000w of solar panels is roughly the same size as a typical mid sized window in a home. so 1x2 meters or 3x 6 foot.

              5000w can power something like 60-90% of a given home depending on if it is gas or electric heat gas or electric hot water and size of air conditioner. That is why solar panels are popping up around the world on houses. for $20-$30k you can get basically free electricity. at $100 a

              • Re: (Score:2, Interesting)

                A 1,000 W panel is its peak rating. It will give you about 300W average during daylight hours (in the tropics, not North London), so about 150W average over 24 hours.

                Where you live is a lot different to here. Generally, we expect a house to average 4kW (over 24 hours) with no A/C. 5kW will probably only power one A/C in addition to routine loads, and a very small house has a 15kW gas boiler round here.

                Electric heating costs 5 * the price of gas here. Even using an A/C in heating mode will cost you twice

              • for $20-$30k you can get basically free electricity. >

                Whoodathunkit!

    • by swb ( 14022 )

      Whether it's worthwhile seems to come down to something like how many square meters of collector does it take to create 300 liters of water per day and is it all done with just solar power or does it require extra inputs and how much does it cost.

      • and something like if there is 300 liters of water present in the air to begin with.
      • I have no idea where you're getting 300L a day. A human only needs around 1l of water a day to survive.

        • A human only needs around 1l of water a day to survive.

          In the desert ?

        • Human water needs (Score:5, Informative)

          by sjbe ( 173966 ) on Friday April 14, 2017 @08:01AM (#54233711)

          A human only needs around 1l of water a day to survive.

          You will respirate and pee away well more than 1 liter [quora.com] per day under normal circumstances even if you aren't in a desert and are doing nothing active. Water requirements can easily exceed that substantially if you are sweating significantly or if it is very hot.

        • A liter a day is your "invisible" water loss, due to respiration and perspiration. If it's not too hot and you're sweating like a pig.

          Urine accounts for 1.5 - 2.5 liters a day, depending on circumstances. If you're dehydrated and your body notices it should be conserving fluids, you're closer to 1.5, but that's not good for your kidneys if carried on for too long.

          So we're closer to 2-3 liters a day that you need to survive. And your didn't brush your teeth, wash yourself or cook food yet.

        • I have no idea where you're getting 300L a day. A human only needs around 1l of water a day to survive.

          No, active adults need about 3L not 1L. So with this device producing about 2.8L it could sustain a single person. Things get complicated with activity levels and climate, and water in food counts towards the total.

          The 1L per day figure is life raft level rationing where you are sedentary and either rescued from the sea in a few days or likely to die so additional water is unlikely to change the outcome.

        • I have no idea where you're getting 300L a day. A human only needs around 1l of water a day to survive.

          It sounds like total water usage in the west once you consider showers, toilets, cooking, cleaning, etc.

        • 1l a day to survive if you're sitting around in a nice cool environment and not doing much exercise. A lot more than that in the desert and/or if you do any kind of physical labor.

          In the prepper community, the general rule of thumb is to store 5 gallons of water per person per day. That's the bare minimum for drinking needs + food preparation + some (very) basic personal hygiene.

    • There have been a few, let's say, shady promises about extracting water from air, mostly coupled with crowdfunding campaigns (gee, why could that be?).

      And how. Crowdfunding is a great way to grab some money from the Youtube perpetual motion gang.

      The thing that is odd is that this paltry 3 liters of water with it's expensive collection materials pales in comparison with this system that will extract 42 liters per day, http://www.treehugger.com/clea... [treehugger.com] , uses wind power, and only costs 134 dollars.

      These people are pikers compared to the manufacturer of that fine bit of kit.

      But there are those nasty thermodynamic laws and the enthalpy of vaporizat

      • Since I don't know just how good the lawyers of those Vaporware producers are, I will refrain from commenting on the veracity of that claim. I will point out, though, that with a relative humidity of 100% at 25C you can squeeze 0.01ml of water from a liter of air. Or 0.00001 liters per liter of air. So it's easy to see that you'd have to move and FULL dehumidify (which is impossible, but let's fake it, I mean, if they can, why shouldn't we...) over 4 MILLION liters of air for those 42 liters of water. And w

    • I suppose the difference is that those other products were designed by artists, and this one is developed by scientists.
      The artists have no idea about the technical details of how it supposed to work, and try to hire some engineers to do the actual development. When the numbers don't work out, then they go into full bullshit mode, crafting stories to their backers about supplier difficulties or whatnot.

      The scientists are already developing the device and have some prototypes that do things. The claims are l

  • by sjbe ( 173966 ) on Friday April 14, 2017 @06:58AM (#54233539)

    What is the cost per unit of water generated? It doesn't matter if it works if it is prohibitively expensive per unit of water generated. If the economics of it don't make sense it will never be used at scale.

  • by randomErr ( 172078 ) <ervin DOT kosch AT gmail DOT com> on Friday April 14, 2017 @07:18AM (#54233583) Journal
    So, they hooked a solar cell to a thermoelectric cooling cell [wikipedia.org]. Its the same tech as those USB refrigerators. You can build a basic a basic unit for $30-40 [digikey.com].
  • Vapor-ware (Score:5, Funny)

    by Ritz_Just_Ritz ( 883997 ) on Friday April 14, 2017 @07:24AM (#54233605)

    ...that really is VAPOR ware. ;)

  • Where did they test this thing and what was the relative humidity during the test? 3 liters isn't enough for one person to survive on in the desert (1 gallon per person per day) so you'd really need a lot of them for normal daily use and a lot more to be able to grow crops.

    • Maybe it works even better for a sailboat on the ocean. A silent water maker that can generate a few liters of water each day sound pretty useful to me even when not in the desert.
  • I mean if drinking distilled water is bad for you, long term, without adding the minerals that your body needs, that's not really a good solution. Plus, I expect this water is going to be pretty hot since it's sitting in the desert sun, so that the solar panels can power it, so... Maybe the real application for this is that they have a really fancy way to boil a pot of water to cook their noodles? I didn't really think that my 10 cent pack of ramen needed a more cost effective cooking mechanism, but if they

    • I mean if drinking distilled water is bad for you, long term, without adding the minerals that your body needs, that's not really a good solution

      There are minerals in the food.

  • has typed the words "moisture vaporators" prior to this?

    Damn, has this place gone downhill.

  • New Solar-Powered Device Can Pull Water Straight From the Desert Air

    Yeah, it's called a sheet of plastic [wikihow.com].

  • Second-world community I knew had a condenser for night dew installed by a global charity. Two nights later, the locals had stolen the polythene sheeting on which it relied. 'Appropriate Technology' Rules OK.
  • if implemented widescale, it will screw up weather patterns globally. there's a finite amount of water on the earth.

  • But . . . people fart in it.

  • It should be 30 deciliters. C'mon, get the units right. It's a windtrap.

    --Shai-Hulud

    • Whoops, I have to turn in my sci-fi geek card. That should be 0.3 decaliters/day.

      It will still take quite a while to collect millions of them. But when we have enough...

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