Generate electricity with "waste" heat

Discussion in 'Electrical' started by CrazyDan, Aug 17, 2016.

  1. CrazyDan

    CrazyDan Member

    As we all know, current ways to hook up lights on our bikes without recharging batteries at home robs horsepower to the ground. I present to you the Thermoelectric Power Generator http://www.shop.customthermoelectri...TL4HucHnqhnuS7X7Uf7UY6ihthI1EmvWecxoCxVPw_wcB I'm pretty sure there are others to be found but I'm too excited about this and had to post it without finding all our available options first. We don't need to steal power from our motor, it gives this stuff away for free ;).
     
    Last edited: Aug 17, 2016

  2. CrazyDan

    CrazyDan Member

    Found another source with more to choose from.
    http://www.tegmart.com/thermoelectric-modules/
    These things are pretty small and I think can be used in series or parallel to achieve the volts or watts desired. The bigger the temperature difference the more energy they produce, so you want a heatsink on the cold side for sure with air flowing across it. They can go on any surface that gets hot, as long as it doesn't exceed 330C constant with the occasional 400C spike. This will definitely keep batteries charged or power your lighting directly, might even be good enough for a hybrid system with an electric front hub.
    Found some cheap ones for $0.99 each http://m.ebay.com/itm/181975508417?...16&_trksid=p2141725.c100338.m3726&_mwBanner=1 they are weaker but you can make up for it with more in a string. Hope all this helps with everyone's power needs. Happy motorbiking.
     
    Last edited: Aug 17, 2016
  3. jaguar

    jaguar Well-Known Member

    These can output a good amount of current for powering lights. But it needs to have a transistor heat sink attached to its cold side and since those are flat then it needs to be mounted to something flat like a cylinder fin (and not an exhaust pipe which is round). Looking at the specs of the 6 watt one it actually only outputs 2 watts at 150 degrees celsius (300F) and 1.3 watts at 100C (212F) so its wattage listing is for the very highest of temperatures. My engine gets up to around 300F at the base of the spark plug so at an outer fin it is probably around 250 degrees which is 120 C. The 7 volt module outputs 2.5 watts (2 v at 1.25 amps) at 120 degrees celsius on the hot side and 30C (86F) at the cool side (at the heat sink). Most bicycle lamps use 5 volt USB recharging so they wouldn’t work. Some lamps use two AAA (1.5v) batteries so to get 3 volts you’d need 150C (302F) for the 7W module to work. Around the middle of the exhaust header the temp is around 600F so probably on the muffler the temp would be high enough but not too high. Maybe use of a hammer could make a flat spot for it.
    Here is a $3 heat sink from Mouser Electronics that could work with it: page
     
    Last edited: Aug 17, 2016
  4. CrazyDan

    CrazyDan Member

    Instead of doing anything that might impede your exhaust flow you can use hose clamps and a metal plate for the surface, make sure its good and snug, or even weld a small plate to your header. I think these can be ran in series or parallel to increase voltage or wattage output. Used with a charging circuit you can charge a battery. Check out the camping generators that you put over a campfire or stove that has 5 volt usb and 12v cigarette lighter outputs. Its being done elsewhere with no issues getting the voltages desired. You just need to figure out the operating tempuratures of what you intend to mount it on and buy the ones that operate at those tempuratures, then buy or make a charging circuit to cover your needs. Also remember, these will continue to generate electricity even after your engine has been turned off till it matches ambient tempurature. Also from what I understand is there only has to be a tempurature difference, you don't need it to reach a certain operating tempurature, those are just the maximums. Each one has different max tempuratures, some use solder so they can't get too hot, others have different materials used. If one side is 50C and the other is 150C they will have a 100C difference and get the power specified for that difference. If you can't keep the heat transfer at bay the cold side will slowly rise and it'll produce less. I might buy a few of these 99 cent ones and screw around with them a bit.
     
    Last edited: Aug 17, 2016
  5. Steve Best

    Steve Best Active Member

    I am already making electricity from heat:
    [​IMG]
    It is a Biolite woodstove, weighs about 2 lbs (1 Kg).
    Has a fan and can make a cup of coffee in about 7 minutes starting with cold water and dry wood. I've used it for about 3-4 years now, love it. No need to bring propane canisters or messy stinky fuels. I even have a BBQ (grilling) rack for it. Miles back in the woods I can cook up a rack of ribs while my phone and GPS charge up. .

    It is an interesting idea to use this solid state heat to electric technology on low powered bikes like ours. Complete with a small Li-ion battery and LED lights could have the whole package for less weight than an extra coil.
    Steve
     
  6. CrazyDan

    CrazyDan Member

    Not to mention it won't rob power from our engines like every other form of electric generation we have available excluding solar.
     
  7. zippinaround

    zippinaround Active Member

    dont forget the wind!
     
  8. CrazyDan

    CrazyDan Member

    Any wind resistance from spinning a fan will produce drag robbing power, simple science.
     
  9. zippinaround

    zippinaround Active Member

    Well it's not directly robbing power , I'm sure with clever positioning you wouldn't notice any loss. If the area of the fan blades were the same as your hand let's say , next time you're going flat out put your hand out see how much it slows you.