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Power Technology

Harvesting Energy From Humidity 89

rtoz writes: Last year, MIT researchers discovered that when water droplets spontaneously jump away from superhydrophobic surfaces during condensation, they can gain electric charge in the process. Now, the same team has demonstrated that this process can generate small amounts of electricity that might be used to power electronic devices. This approach could lead to devices that can charge cellphones or other electronics using just the humidity in the air. As a side benefit, the system could also produce clean water. The device itself could be simple, consisting of a series of interleaved flat metal plates. A cube measuring about 50 centimeters on a side — about the size of a typical camping cooler — could be sufficient to fully charge a cellphone in about 12 hours. While that may seem slow, people in remote areas may have few alternatives.
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Harvesting Energy From Humidity

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  • by Anonymous Coward
    Could we place banks of these along the US / Mexico border at aid stations so that incoming immigrants can stop and hydrate and recharge their cell phones?
  • by Commontwist ( 2452418 ) on Tuesday July 15, 2014 @05:39PM (#47461577)

    Power and water to produce... more power and water? Hmm... I wonder how much this could scale up

    • To be clearer: if a temperature difference can start the power generation in a humid area, can the power generated be enough to power an air conditioner to cool down enough air to extend the duration of the water condensation when the metal gets too warm and needs to be cooled? I doubt that it would allow perpetual water production but would the extra cooling allow it to extend the condensation process and power generation any significant degree?

    • Err....

      0.5m cubic of spaced sheet metal to charge a phone in a mere 12 hours and produce x litres of water.

      Why on EARTH would you want to scale this up??

      Perhaps on a distant, humid planet far from the sun?
      • Math fail...

        0.5 x 0.5 x 0.5 = 0.125 cubic metres.

      • Why on EARTH would you want to scale this up??

        You could use windtraps to increase humidity and use the electricity to pump the resulting water to your sietch water stores. Maybe not necessary on earth now, but who knows...

        • by cdrudge ( 68377 )

          If it takes 12 hours to charge a cell phone, I'm not sure how much water you'll be pumping in the same time period.

      • by gl4ss ( 559668 )

        well a shipping container sized thingy cold power an ordinary house if it scales up.

        if you can get cool from somewhere I suppose for the condensation?

        is it more efficient than peltiers for temp difference power generation?

  • uhh yeah they do... (Score:5, Informative)

    by Anonymous Coward on Tuesday July 15, 2014 @05:40PM (#47461589)

    its called a solar panel. it'll charge your phone in about an hour

    • Unless you're inside a cave; both humid and dark.

      This might be less-useless to maintain a small underground device, like a sensor to detect floods in a sewer system.

    • You'll need a much larger panel than 50cm to charge it that fast. And sunlight. This device should work day & night, regardless of weather.

  • by psybre ( 921148 ) on Tuesday July 15, 2014 @05:42PM (#47461613) Journal

    "What I really need is a droid who understands the binary language of moisture vaporators."

  • I'm from Florida and I'll take 30.
  • Are these modeled after the moisture vaporators used on the moisture farms of Tatooine

  • by Anonymous Coward

    the amount of power produced was vanishingly small â" just 15 picowatts, or trillionths of a watt, per square centimeter of metal plate. But Miljkovic says the process could easily be tuned to achieve at least 1 microwatt ... per square centimeter.

    This is another "5 years away" technology. I'll believe it when I see it.

    Also, how did they calculate that? My phone's battery contains about 1000mAh at about 3.5V, or 3 joules. To charge that in 12 hours, you'll need 250000 square centimeters, or 50000 square centimeters per cube side, which comes out to larger than 2 meters cube.

    They talk about making it smaller by having a large internal surface area, but I do not believe their fins-on-a-radiator strategy will work, since the moisture would condense near

    • ... unless the cube is made of 10 50cm square sheets 5cm apart.
      Then you've 50,000cm2 of surface area in a 50cm cube.

    • by mikael ( 484 )

      They would need to increase the surface area of the plates, probably using three-dimensional fractals. This would increase the ratio of surface area to volume in the same way that human lungs or fish gills work.

    • by Bengie ( 1121981 )
      A joule is a watt second. a 3.5v 1Ah battery will supply 1 amp @ 3.5v for 1 hour. That is 12,600 joules. I could be wrong, I'm great at making minor math errors.
  • "While that may seem slow, people in remote areas may have few alternatives."

    ''few' as in this device but no bug spray or cookstove, or few as in near death, out of water and food with only one magic wish left?
  • Where? (Score:4, Insightful)

    by Red Herring ( 47817 ) on Tuesday July 15, 2014 @06:00PM (#47461785)

    At ~1pW/cm^2, a 50x50cm verision of this will provide about 30mWh in 12 hours. Tiny cell phone battery. Heck, a tiny lithium coin cell will provide ~150mWh.

    For contrast, a typical solar cell will give 130W/m^2 (-ish), so a 0.25m^2 solar cell will provide ~33W, while the sun shines, obviously.

    I'm not sure where exactly on Earth is sufficiently "remote", dark, moist, and unreachable that this makes sense. (Yes, I though of that, but it's really uncomfortable to fit a camping cooler there...)

    • Re: (Score:2, Funny)

      I'm not sure where exactly on Earth is sufficiently "remote", dark, moist, and unreachable that this makes sense.

      Thor's vagina.

    • It's interesting, but practically speaking is it worth building a large, passive electricity and water generator in a cave system?

      Not really.

      OTOH, it would generate electricity forever, or at least until dust caked all the plates.

    • Re:Where? (Score:4, Informative)

      by Ichijo ( 607641 ) on Tuesday July 15, 2014 @06:37PM (#47462081) Journal

      At ~1pW/cm^2, a 50x50cm verision of this will provide about 30mWh in 12 hours.

      That's just one 50x50 cm plate. They're suggesting a 50x50x50 cm cube of stacked plates.

    • At ~1pW/cm^2, a 50x50cm verision of this will provide about 30mWh in 12 hours. Tiny cell phone battery. Heck, a tiny lithium coin cell will provide ~150mWh.

      50x50x50 cm cube. Presumably they were able to fit (by your math) 5 plates in the cube.

    • Re:Where? (Score:4, Insightful)

      by viperidaenz ( 2515578 ) on Tuesday July 15, 2014 @07:36PM (#47462555)

      A solar panel doesn't produce much clean drinking water.

      • With electrolisis and a fuel cell, only the gas carried contaminates could possibly contaminate the drinking water. For quanity and qualityproduced, I'll take the solar solution. The distances traveled and the amount produced are both quite small. In the solar solution, the volume would be much greater and due to the recombining of gasses, much less likely to transport pathagens.

    • by afidel ( 530433 )

      More like 30-60W/m^2 depending on if they're amorphous or poly-crystalline, most folks won't be buying 25+% efficient monocrystalline panels for charging their cellphone =)

    • Solar panel by day, wind trap by night!
  • by Livius ( 318358 )

    As in, you need some cooling to get the condensation happening.

    Still, pretty neat to get electricity from it.

    • So if it's hot a humid and this technology is integrated in to home heat pumps, they could dehumidify more effectively at the same time as lowering power consumption a tiny fraction?

      The surface area of the heat exchangers in heat pumps is huge.

  • Didn't Frank Herbert write of something similar to this in Dune? I recall small objects which collected water, but I don't recall whether they provided any sort of power generation in the process.
    • They didn't - they were 'simple' water collectors (such as, I think, already exist), providing a small amount of clean water at dawn but not generating any energy in the process.
      This tech, however, would be a nice one to power the Fremen's stillsuits in the same universe - providing additional water from the atmosphere while at the same time powering the various pumps and recycling tech inside of the suit :-) though if I remember correctly Herbert described those as powered by the movements of the user.
      • by Onuma ( 947856 )
        Yes. In Children of Dune, Leto's stillsuit was sabotaged. They tampered with the pumps located in the heels, which would normally circulate water as the wearer walked through the desert.

        Good call.
  • Now my fat sweaty body will actually be good for something... Eat It Mom!
  • by phorm ( 591458 )

    Would this work with snow? Sounds useful for Canada and other places that have snowy winters that aren't so solar-friendly. Won't help on an overcast-but-not-wet day though.

  • A cube measuring about 50 centimeters on a side â" about the size of a typical camping cooler â" could be sufficient to fully charge a cellphone in about 12 hours. While that may seem slow, people in remote areas may have few alternatives.

    You're not going to be carrying this thing in a backpack, so it's not like you won't have a car to charge your cellphone.

    On the other hand, you might be far enough out in the boonies that you can't get a car to where you are. Of course, the question then become

    • Arguably *something* like this could be placed remotely to power the search and rescue device at the end of a trail in a national park... It could spend months just making sure that it keeps its own battery topped of for when someone needs to signal for help.

    • What if that cube provides you with clean drinking water as well? Spare cellphone batteries won't do that.

  • Given that a low end cell phone charger is about 2 watts, 1 watt would be a fair performance assumption for that 50cm unit. That gives us an approximate 8 watts per mÂ. Scaling up, this means that a cube 5 metres on a side will generate a kilowatt of electricity.

  • under the same conditions? That's what would really be interesting.

    This new device needs a temperature differential and humidity to operate. A thermocouple only needs a temperature differential. The new device won't work anywhere where there isn't a humidity high enough to provide condensation (such as space).

    It's a curiosity, but I'm not investing any money in it in the short term...

  • Quick, someone call Kickstarter and get iFind up and running again.

  • So you're telling me that when I'm outside pouring sweat in the oppressive Floridian humidity, I can look down at my phone to see it's charging and for a brief moment not hate where I live? TAKE MY MONEY!
  • and you can create X-rays by rapidly unrolling scotch tape in a vaccuum. I don't see conventional X-Ray machines, let alone CT scanners, leaving the scene to make way for "Scotch Tape" X-Rays. I also don't see me getting rid of my USB charging cord to make way for dehumidifier chargers. It is interesting that people have found these things out though. It gives me hope that there is still enough inquisitive nature left for true innovation.

  • This will not only trigger Global Drying, but Republicans will deny it's happening, making it hard to do anything about it, and Koch bro's will buy up moisturizer lotion companies to profit from it.

  • While that may seem slow, people in remote areas may have few alternatives.

    Try this [] or this [] as alternatives.

  • How much energy does it take to create a super hydrophobic surface?
  • Way too high tech for remote areas.

    Bringing clean water to remote areas in Africa means using parts that can be sourced from those remote areas using skills taught in those remote areas or else it's back to dirty water in a few years.

    Think about aliens crashing a ship on Earth. Where would we get the parts to fix it? Alien technology is worse than useless when it fails.

    • It's easier to fix alien tech if you are living in an alien junkyard.

      I don't know about those areas specifically, but there are many extremely poor areas of the world that are drowning in 1st world waste like plastic bottles and broken electronics.
      Maybe the solution could use those "resources"

      Some of this already exists, like the 20oz-bottle skylight (fill bottle with water and 2 cap fulls of bleach, drill hole in tin roof, stick bottle half-way through, and seal it somehow) The end result is a bright light

  • by rossdee ( 243626 )

    dam! I wish I had thought of that

  • Scientists have conducted simulations using super computers and whole bunch of formulas to test the impact that these devices might have on climate. Their research was inconclusive due to lack of funding but they say that it could lead to devastating planetary dryness and eventually global catastrophe. They are requesting another $10bn annually to continue the important research and have begun to lobby for Al Gore to become their fund raising spokesperson. Meanwhile a base of deniers is building who deny th

  • by BillX ( 307153 ) on Wednesday July 16, 2014 @12:52AM (#47463981) Homepage

    While the "water droplets spontaneously jumping off superhydrophobic surfaces" effect is interesting in itself, the mechanism of stripping charge from those droplets as they leave the apparatus sounds like a variation of the Kelvin water-drop energy harvester from 1867 []. In this case, rather than charge separation via the cross-connected cups, electric-double-layer charge-separation occurs between the droplet and the hydrophobic surface, causing the two to come away similarly unbalanced when the droplet jumps away.

  • I gather that "remote areas" somehow excludes deserts? Amazing ...
  • While that may seem slow, people in remote areas may have few alternatives.

    Other than:

    Solar power, at roughly $1/watt (and then "free" for 10-20 years), price falling on a nearly Moore's Law trajectory.
    Wind power -- expensive, unreliable but simple technology and humidity isn't reliable either.
    The entire panoply of standard sources -- coal, oil, gasoline, nuclear, hydroelectric, alcohol, diesel, methane... which we can deliver a variety of ways including simply delivering a small generator and fuel.

    I would

    • > Solar power, at roughly $1/watt (and then "free" for 10-20 years), price falling on a nearly Moore's Law trajectory.

      Ummm, no. Current prices, all in and spinning the meter, is around $1.70/W. Those are the latest cross-US numbers.

      > Wind power -- expensive, unreliable but simple technology and humidity isn't reliable either.

      Whereas wind actually is about $1/W (same source, DoE) and has a CF of 30% as opposed to 15% for PV.

      Both are inexpensive and work well. We need both, and are installing both faste

    • I really hate solar panels.

      Concentrated sunlight into thermal generators is more efficient, cheaper to produce, cheaper to maintain, less toxic to produce, and so on. Europe? Parabolic reflectors focus light from an infinite-distance focal point to a fixed focal point, where you place a sterling engine or a salt tower.

      For the home, you don't want all that conversion waste. Electricity is the last thing you want. You should have a solar hot water system with an evacuated tube collector--a set of 18

  • Really MIT? Stooping to ripping off the University of Dayton?!

  • Seriously, something like that would enable a transmitter and a camera to be set up. Where this could be useful is for fire, weather, geological monitoring. Heck, this could even be used to put simple digital telescopes up on 14K' tops and broadcast back.
  • I live in an area with high humidity (~80% / 25C) and am wondering how well this would work as a dehumifier that uses no electricity. The one we own is rated at 400 Wh. We often run in daily for 2+hrs. Also, if this is effective I can see other uses, like drying clothes. Or a small set up that can provide 2-3 liters of potable water/day.

"In matrimony, to hesitate is sometimes to be saved." -- Butler