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Human powered still - Nichrome wire

  1. Mar 1, 2007 #1
    The ASME design competition is to design a human powered still... basically to use human power to boil water. We have a bike running a DC motor, producing a range of 100-250 watts (depending on pedal speed, we need to test this).
    To convert this to electricty, we were thinking of using nichrome wire. However, as far as I know this wire is electrically live, so we can't just put it in water or put it on a copper pot.
    How can we insulate the wire electrically, but not thermally?
    Thanks,
    Drew
     
  2. jcsd
  3. Mar 1, 2007 #2

    Danger

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    Gold Member

    Your terminology is a bit confusing. I assume you mean that you're using the motor as a generator, and want to use the NiChrome to convert the electricity into heat.
    As for the insulation aspect, I believe that a couple of coats of engine enamel or other high-temperature paint would work. It's not flexible though, so have the wire in the desired shape before coating.
     
  4. Mar 1, 2007 #3
    Thanks, I'm looking into the high temp paint idea.
    You got it, I'm using the dc motor as a generator to produce electricity.
    What exactly does high temp paint do? I want to electrically insulate it, but allow for maximum heat transfer from the wire to the water. (or wire to copper pot to water).
     
  5. Mar 1, 2007 #4

    Danger

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    The paint doesn't exactly do anything that other paints don't, but its chemical make-up is designed to withstand extreme temperatures without degrading. It's used to paint car engines, barbecue grills, and such-like. Although some of them might be electrically conductive, most are not.
     
    Last edited: Mar 2, 2007
  6. Mar 1, 2007 #5

    berkeman

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    You could also look at the supermarket for the handy coffee/tea warmer things that plug into the wall socket, and have a small coil that you put in your cup to heat the liquid. You could either use it straight away, or tear it apart to see how they do it. The outer layer of the coil is metal, but it is not energized directly with wall voltage, obviously, since that would give even decaf coffee quite a jolt!
     
  7. Mar 1, 2007 #6

    rbj

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    BTW, get someone in good shape to ride the bike. 1/4 kilowatt is serious sweat.

    100 W = 100 J/s = 100 N-m/s

    100 N is about 22 pounds force. so to power your 100 watt bulb, you have to lift a 22 pound object up from the floor to a table top 1 meter higher, and you have to repeat this every second. will get tedious after a while.

    think of that when you imagine all these empty and lit buildings overnight. we waste a f0ck of a lot of energy, especially when you equate it to human terms.
     
  8. Mar 1, 2007 #7

    berkeman

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    I second rbj's comment. When I ride the stationary bikes in our company Gym, they tell me something like 125W for the average power output for a 30 minute ride usually. I'm no LanceA, but I do push reasonably hard.
     
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