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Wireless Networking Hardware

Wind-powered Wi-Fi Sensors 89

Posted by ScuttleMonkey from the self-sufficient-drones dept.
Glenn Fleishman writes "According to an article at Indolink a 10-centimeter diameter windmill can produce the 7.5 milliwatts needed for a wireless sensor. The paper was published earlier (available as a PDF), but Nature magazine has apparently picked up the tidbit. The process flexes piezoelectric crystals to create a current. Although flywheels aren't mentioned in this article, it seems like a windmill, a flywheel, and a solar cell could in combination produce effective power in a range of conditions for remote wireless devices, including network relays obviating batteries entirely."
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Wind-powered Wi-Fi Sensors More

Wind-powered Wi-Fi Sensors

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  • not enough power for 802.11 (Score:5, Informative)

    by j1m+5n0w ( 749199 ) on Saturday November 12, 2005 @09:32PM (#14018215) Homepage Journal
    802.11 cards typically consume around 1 or 2 watts. They are probably targeting much simpler radios, like those used in motes.

    • Re:not enough power for 802.11 (Score:5, Interesting)

      by EnderWigginsXenocide ( 852478 ) on Saturday November 12, 2005 @10:01PM (#14018307) Homepage
      A sensor need not be on the network 24/7. When it's onboard memory has been filled to a certain capacity (say 80%) if fires up the transceiver and transmits to the network. You only need peak power on occasion. Give your windmill plenty of time to charge up a big capacator (or a small battery.)
      • That is true, a very short duty cycle could be used. However, I think in this case the author of the article simply assumed that "wireless" in the paper automatically means "wifi", which it certainly does not. (The paper does not specify any particular protocol.)
      • Surely though, unless all these wireless repeaters are time-synced to power up (once charged and ready) at a certain time, there's a pretty high probability that the neighbouring nodes will be powered down when your node is ready to go. Though, I suppose less power would be needed to run a simple sensor for nearby active nodes, upon which it could then actually transmit. Will still obviously require some power though. I can imagine the routing being a nightmare too.
    • Low power wireless sensors are more likely to be using Zigbee etc. It isn't just the power for the Wireless stuff, but also the host CPU. A Wifi device needs a big fat-assed stack (+ lots of CPU) while a Zigbee device can probably live with a very small CPU and less than 1kB or RAM. There are a lot of very low power devices in this range.

  • Not to optismitic about being commercialized yet (Score:3, Interesting)

    by external400kdiskette ( 930221 ) on Saturday November 12, 2005 @09:36PM (#14018233)
    "Dr. Priya foresees piezoelectric bimorphs being utilized to power a variety of small devices" but I foresee nothing practical unless the efficiency is as high as enviromentally unfriendly stuff known as batteries. People just aren't going to go for this sort of thing anymore than other alternate energies unless it's going to work just as well sitting alone with no vibrations ... I mean he mentions a discman but is it still going to be fine if your lying down with it on a table playing for hours on end lacking vibrations , indoors with no wind in sight... if not it's not ready to be commercialized. That's the problem with alternate energies, they're cool and great for the environment but lack of efficiency means you usually have to suffer to be a good citizen.

    • That's the problem with alternate energies, they're cool and great for the environment but lack of efficiency means you usually have to suffer to be a good citizen.

      I've played with an old electronic calculator which plugs into the mains socket, but ones with little solar cells and no battery at all are far more convenient these days.

      The principles behind things like the device described have been known for some time, but as energy requirements to do stuff decreases they increase in usefulness.

    • Yeah, because battery powered devices are great when you have no batteries around. And god forbid anyone ever build a hybrid device (where's the market for that?!).

      When I viewed this page on a threshold of 3, there were 5 comments. 2 of them were full of utter crap. What is wrong with moderators today? Don't they think before modding something up?

  • electric double layer caps (Score:5, Interesting)

    by Montressor ( 34631 ) on Saturday November 12, 2005 @09:37PM (#14018238)
    Flywheels? The simplest way to store power would be an electric double layer capacitor. No moving parts. They can come in up to 70F at 2.1V - that's 140 C of charge. At 10 mW of power, 2.1V is 5mA of current; that means that it can stay above 1.5V for 2 hours. If a higher voltage is needed, put the capacitors in series. And these are not huge devices. Here's a datasheet for one [panasonic.com]
    • I'm trying to remember my electronics classes, but doesn't the capacitance drop in half if you put capacitors in series?
      • Yes, but the energy stored still doubles. At a higher voltage, with the same power, you'll have less current, so you need less stored charge.

        • Re:electric double layer caps (Score:1, Informative)

          by Anonymous Coward
          The energy stored in a capacitor is

          U = Q^2/2C = C/2*V^2

          If you put your two identical capacitors in series, then each is dropping only half of the voltage of the battery (the same for each as the lower voltage before). But at the same time the capacitance is cut in half (by being in series). So the energy stored is 1/2 * (1/2C) * (V/2)^2 = 1/16 * VC. If you put your capacitors in parallel with half the voltage then the energy stored is 1/2 * 2C * (V/2)^2 = 1/4 * VC. In your example of 70 F and 2.1 V this

          • Re:electric double layer caps (Score:1, Insightful)

            by Anonymous Coward
            I should have been slightly more clear. Its 77J series for each capacitor (for a total of 154J series) and 309 J for each capacitor in parallel (for a total of 617 J parallel).
          • I think you misunderstood what I meant - I was implying using a series of two capacitors charged to a total of 4.2V - rather than one or two capacitors in parallel charged to 2.1V (2.1V is the maximum charge of the capacitor); this would be for cases where 2.1V is an insufficient operating voltage. So the voltage doubles as the capacitance drops in half, doubling the total energy.

      • Re:electric double layer caps (Score:2, Informative)

        by Anonymous Coward
        I'm trying to remember my electronics classes, but doesn't the capacitance drop in half if you put capacitors in series?


        You're correct, however: energy stored = 0.5CV^2 (C = capacitance, V = voltage), so if C decreases by a factor of 2 while V increases by a factor of 2 (making V^2 increase by a factor of 4), "energy stored" will overall increase by a factor of 2.
    • Thank you! Why is it that submitters randomly feel the need to pick out a buzzword to stick into the headlines?

      Flywheels are not energy dense storage (very much the opposite, both on mass and volume). They're not efficient electricity storage. They're leaky storage. They're not cheap (for a given amount of energy storage). They'd interface awfully with wind power, which is variable RPM.

      The main benefit of flywheels is that you can get a lot of power from one at once. What the heck does that have to do
  • How about bring them back with a geeky Wi-Fi vengeance?

    Possibly even attach an LED headband to it to tell others how close to a hotspot they're in. C'mon, I see profits galore!

  • Prior Art (Score:5, Funny)

    by karvind ( 833059 ) <karvind@NoSPAM.gmail.com> on Saturday November 12, 2005 @09:49PM (#14018274) Journal
    Propeller Beanie hats [hatsinthebelfry.com] :)

  • Wi-Fi and Wind (Score:5, Insightful)

    by Chrontius ( 654879 ) on Saturday November 12, 2005 @09:50PM (#14018278)
    First, these aren't wind powered sensors that transmit over wi-fi -- they're wind-powered sensors that detect a wi-fi node nearby. There's a big difference in power levels there. The first sounds really nifty, and with lower-power radio systems would be really cool. The second sounds like something ThinkGeek will have on clearance in about two years.
    • Really? The artical gives the impression that these are in fact used to power wireless sensors that transmit data, and not power sensors that detect a wi-fi signal. I mean, what would be the point in installing them otherwise?

  • Larger applications? (Score:3, Insightful)

    by Nerdposeur ( 910128 ) on Saturday November 12, 2005 @09:50PM (#14018279) Journal
    I have no concept of electrical quantities. What I see here is "tiny windmills make electricity."

    So, for someone with more of a clue: does this sound like something that could be scaled up? Like, could you put them all over your roof and generate green power, or would there not be enough juice?
    • Likely not enough - I suggested small normal windmills on roofs of our house in a previous post and someone said even that wouldn't be enough (ie. it would barely make a difference). I thought if each house had 6 small windmills they could reduce the load (imagine every house having this). But I was told it wasn't enough even still. Too bad, I would love to know in the middle of summer with solar and wind power I was generating enough power to reduce my electric bill by 40% or something.
      • Wait to dramatically reduce your A/C bill in the summer? Install high-efficiency insulated solar reflecting windows. Plant shade trees and place awnings in strategic places.

        It may not be as "sexy" as a bunch of windmills and a roof full of solar cells, but it will get the job done... and not need maintenance to boot.

      • Re:Larger applications? (Score:2, Informative)

        by odysen ( 930700 )
        Forget about wind turbines on a house. A house in a windy location will generally need about 1kw wind turbine. The turbine should on at least a 30 foot tower, above your roof. That being said, turbines on top of buildings usually aren't a good idea. The building becomes an acoustic from the vibrations of the wind turbine. Not to mention your home probably wasn't build to handle the stress. Anyway.. Solar is great solution though.

      • Well you could put windmills on your roof. However there are some problems.

        The first, as the other guy said, is they tend to transmit annoying noises into the house if they are on the roof. Not technical problem, but annoying enough that most people wouldn't stand for it.

        Only the largest mansions are big enough for several windmills. A windmill causes turbulence around it, which cuts the efficiency of nearby windmills. To get 6 windmills on the roof you are looking at maybe 10 watts from each - no

  • What is the advantage of his piezoelectric device over a simple electromagnetic generator?
    • Well, from Wikipedia, "Direct piezoelectricity of some substances like quartz, as mentioned above, can generate potential differences of thousands of volts." I imagine it'd take hell of a field and alot of [horse]power to get "thousands of volts" (even if at low amperage.)
      • No, it would just take many turns of very fine wire. However, that's irrelevant here. The piezoelectric devices under discussion use high-output ceramic material to produce useful power at useful voltages.

    • Re:Doing It The Hard Way? (Score:5, Informative)

      by EnderWigginsXenocide ( 852478 ) on Saturday November 12, 2005 @10:10PM (#14018335) Homepage
      Also found on the internet: " The piezoelectric generator is a much more efficient way of converting wind energy on a small scale than the conventional generators that create energy for the national power grid from wind turbines.

      A conventional generator that used a 10-cm turbine would convert only 1 per cent of the available wind energy directly into electricity. A piezoelectric generator ups that to 18 per cent, which is comparable to the average efficiency of the best large-scale windmills, says Priya. "

  • Wi-Fi (Score:5, Insightful)

    by Montressor ( 34631 ) on Saturday November 12, 2005 @10:00PM (#14018304)
    Will people stop applying this term to everything? Wi-Fi is referring to wireless LAN, not to any device that happens to use the radio spectrum. Use "wireless", or "radio", or "remote".
  • "Obviating batteries entirely"? They misspelled "recharging". They still need a battery for low-wind sensor telemetry. But 7.5mW is less than what 5x5mm of solar panels get. Store the surplus in a battery, and half a square centimeter can power them.
    • 5mmx5mm is only a quarter of a square centimeter.

      Though... I suppose that error doesn't negate your final statement.

      • It doesn't, because my final statement about half a square centimeter includes the surplus I mentioned for the batteries, beyond the quarter square centimeter. I could have been more explicit.
  • Windmill? DARPA is working on dust sized devices that work off of ambient vibration.... catch up with the times. Smart Dust is an old idea.

    http://robotics.eecs.berkeley.edu/~pister/SmartDus t/ [berkeley.edu]

    MOTAR the imperious

  • Environmental effects? (Score:5, Funny)

    by Ritz_Just_Ritz ( 883997 ) on Saturday November 12, 2005 @10:46PM (#14018473)
    10cm?!?! You'll decimate the local Japanese beetle population! We can't have that. Somebody alert PETA!
    • PETA is for animals. I am preatty sure that the organization you are looking to contact is PETJFIDCT (people for the ethical treatment of Japanese flying insects and discarded christmas trees) otherwise known as bill widley, but he's dead.
  • How about a wifi powered wind detector?

  • People Power! (Score:3, Interesting)

    by Max Threshold ( 540114 ) on Sunday November 13, 2005 @12:19AM (#14018751)
    What's with all these over-engineered solutions for the developing world? My mom still has an old foot-powered sewing machine. If people could run a sewing machine with their feet, why not a generator?

  • obligatory (Score:2, Funny)

    by Hobbes828 ( 880721 )
    In Soviet Russia, the Wi-Fi powers the Wind!!!!
  • Wind powered machine that detects.. well..air.
  • "Where are you, sir?"

    "In my office"

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