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Power Hardware Science

Rubber Boots Charge Your Phone 111

Posted by CmdrTaco
from the put-on-your-lead-boots dept.
andylim writes "UK wireless provider Orange and renewable energy experts GotWind have come up with a prototype pair of power-generating rubber boots. Inside the power-generating soles of the boots are thermoelectric modules constructed of pairs of p-type and n-type semiconductor materials forming thermocouples, which are connected electrically to form an array of multiple thermocouples (thermopile). They are then sandwiched between two thin ceramic wafers. When the heat from the foot is applied on the top side of the ceramic wafer and cold is applied on the opposite side, from the cold of the ground, electricity is generated."
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Rubber Boots Charge Your Phone

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  • by dtmos (447842) * on Monday June 07, 2010 @09:39AM (#32482922)

    The term for this type of electricity generation is the Seebeck effect [wikipedia.org]. Typically a very small voltage is generated per pn junction, so many hundreds of junctions are placed in series to generate a significant voltage.

  • Re:Slow news day? (Score:4, Informative)

    by datapharmer (1099455) on Monday June 07, 2010 @09:45AM (#32482996) Homepage
    If the light didn't work well for you it was adjusted poorly or you weren't riding fast enough. The only problems with them were:
    a) You had to ride relatively quickly to generate much light
    b) It added a significant amount of friction to your wheel meaning you had to ride harder and
    c) The light stopped when you stopped.

    That said, a few modifications such as adding a capacitor to even out the light (acting as a voltage regulator), changing the light bulb to LED, and lowering the friction caused by the generator wheel and it would probably work phenomenally well. I was happy even back then though.
  • by drinkypoo (153816) <martin.espinoza@gmail.com> on Monday June 07, 2010 @09:51AM (#32483082) Homepage Journal

    Boots that don't keep my feet warm because they depend on heat flowing across a thermocouple as quickly as possible to produce electricity? That sounds great! I'll take two.

  • So pathetic (Score:3, Informative)

    by Ancient_Hacker (751168) on Monday June 07, 2010 @09:52AM (#32483096)

    So pathetic. This is not a way to generate electricity, but to destroy it.

    You see those "p-n" junctions did not appear out of thin air-- they're the result of using scads of electricity to heat silicon to the melting point, extract it into perfect crystals, then slice it, anneal it again in an electric furnace, then more hours at 1200C to diffuse in minute amounts of p and n dopants, then more electricity to slice, dice, solder, and cement these into usable devices.

    And in the end you have some very expensive, in both dollars and energy used, heat to microamps of electricity converters. And you can easily compute exactly how much electricity you get back given say a 10 degree temperature difference between the warm and slightly less warm sides. It's miniscule. Microwatts per square centimeter. Even if you wore these for 10,000 hours, you're nowhere near making back the amount of electricity, not to mention the $$$, it cost to make these things.

  • by TeknoHog (164938) on Monday June 07, 2010 @09:55AM (#32483116) Homepage Journal

    Would it be possible to put them on a condom?

    Guy in bar to babe: "Hey. My phone died. Would you like to go and charge it?"

    The effect uses a temperature difference to generate power, so unless you are doing a dead fish, it wouldn't help much.

  • Re:Slow news day? (Score:3, Informative)

    by thermopile (571680) on Monday June 07, 2010 @10:00AM (#32483180) Homepage
    If you didn't like the dynamo for your bike, you're definitely not going to like the in-boot charger. Thermopiles have notoriously hideous efficiencies, like 2-5%.

    Note also that it relies on a heat difference between your foot and whatever is outside. So on a hot day, you're going to have a hard time generating much of a delta-T, and your efficiency will drop even further.

    Despite the fact that my nickname is one of these devices, I'm not very hopeful. A piezo-electric based device that uses the mechanical motion of your heel striking the ground is a much better solution, IMHO.

  • by Anonymous Coward on Monday June 07, 2010 @10:09AM (#32483292)

    In my own experiments with themoelectric generation, I was unable to get more than a few tens of milliwatts from such a setup.

    I connected up a cheap peltier module (TEC1-12709), 4cm * 4cm (1.5in * 1.5in), to a heatsink+fan with some heatsink paste, and pressed my palm against the other side, the maximum power output was a few milliwatts, and additionally my palm got cold very quickly (I altered the resistive loading to ensure I reached the maximum power point.) When I used a metal tray of boiling water instead of my palm, I could just about get 50mW (at less than 1V).

    It would seem that these cheap modules aren't very efficient at generating power from low heat differentials, so even you used enough of these modules to get enough power, you'd end up with very cold feet very quickly (and then no more power)

  • by solevita (967690) on Monday June 07, 2010 @10:17AM (#32483384)

    Boots that don't keep my feet warm because they depend on heat flowing across a thermocouple as quickly as possible to produce electricity? That sounds great! I'll take two.

    There are many inventions like this that suggest you can pull energy from nowhere. Of course you can't, it has to come from somewhere. In this case, it's your body heat powering the phone. You'll have cold feet and you'll have to put more energy into yourself everyday to power the phone in the form of calories. No such thing as free energy, just different ways to transfer it about.

  • Re:Slow news day? (Score:2, Informative)

    by Anonymous Coward on Monday June 07, 2010 @11:06AM (#32484008)

    Dynamos still exist; in fact, new models are being produced all the time:
    http://www.peterwhitecycles.com/shimano3n70.asp
    http://www.peterwhitecycles.com/schmidt.asp

    They tend to have pretty good efficiency (~60%), generally use a clutching system so there is no drag when the lights are turned off, and have capacitors that will run the lights for at least five minutes. The problem is the expense - a good hub-mounted generator system runs around $100 and requires a rebuild of the wheel to install (around $50 in labor). Whereas you can get a simple battery-operated LED unit for around $10.

  • Re:Slow news day? (Score:3, Informative)

    by Insightfill (554828) on Monday June 07, 2010 @01:26PM (#32486040) Homepage

    If you built it into the bicycle's hub, it might not cause nearly as much resistance.

    My wife has one of those. Specialized brand made the "Vienna Deluxe" [specialized.com] line last year. You can feel the drag when you hit the switch, but it's very subtle.

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