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TEG/Thermoelectric Power Harvesting

Discussion in 'Renewable Energy' started by Overclocked, Nov 22, 2014.

  1. Overclocked

    Overclocked Member

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    I wanted to start my own thread with this, but a few weeks ago I bought a 6W TEG module that produces 4.1v@1.4A . I attached it to the biggest heatsink I have and got no where near that output. I was lucky if I got 1V at 20mA. I was using a candle as a heatsource. My next idea was to use some high temp insulation from mcmastercarr. That didnt really improve my output much. According to the data sheet, their test conditions are Thot = 300C Tcold = 30C .

    Datasheet:http://www.tegmart.com/datasheets/TGPR-6W-4V.pdf

    But heres my idea. Recently I bought a milling machine and Im thinking about small watercooling system for it. Now in order for water to flow a small pump needs to be on, but in order for the pump to be on there needs to be enough output. I was thinking of using a small battery to get things going and then once the TEG is producing enough, it will charge the battery and also run the Pump. Any extra energy would be available at after that point. Basically the battery is there to get things started.

    Anyone have any suggestions or ideas to add? I found a small DC pump on ebay (3 to 12V). The rest (including a radiator) I can make. This is also more of a curious thing (like stirling engines) just to see how far I could go.
     
  2. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Well one candle puts out about .7 - .8 watts of heat so........... Yea I can see where a 6 watt TEG would likely not work so well running off of one especially once heat transfer and TEG efficiency is factored in.
     
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  3. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Do have any idea what the actual temperature of the hot side was? A candle might be a good spot source for heat, but it is doubtful that with a good heat sink you got the entire hot side very hot.

    Was there soot on the hot side?

    If I read you intent with the mill correctly, it seems you want to use heat removed from machining to generate enough TEG power to supply the circulating pump. That is extremely unlikely with a small mill. Even with a huge mill that is water cooled, your highest temperature will be limited by the boiling point of the fluid, about 100°C. That would require a huge amount of TEG devices to generate enough power to drive your circulator.

    John
     
  4. dave

    Dave New Member

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  5. Overclocked

    Overclocked Member

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    By Mill, I mean a milling machine. Almost like a drill press but you can do A lot more with it. I was going to use my mill to make a waterblock out of aluminum or copper to take away the heat from the TEG.
     
  6. Joe G

    Joe G Member

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    "when there is a temperature difference between both sides" .. when holding it over the candle I'd bet the temp difference wasn't as good as if one side had a heatsink from the candle and the other side
    had a "coolsink". that may make a big difference, My small sterling engine would not run as fast if the cool side got warmed from the heat source, but if I kept it cool by putting a ice cube on it, it would
    run much faster???? The temp defference may make a better Volt output....I was looking at those same items a while ago....I'll keep an eye on your project, sounds like a neat fun one....I wish you luck:woot:
     
  7. Overclocked

    Overclocked Member

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    Yes if you cool the cool end of a stirling engine it will go faster. Ive seen tons of videos where people hook up a generator directly to the engine to get power, but thats not the "right" way to do it, and what I mean by that is it would be better to use a DIY generator.
     
  8. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    I am immensely curios. Why would a DIY generator be better?

    John
     
  9. Overclocked

    Overclocked Member

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    I personally feel that it would be less torque on the engine to get started. Stirling engines are already low power, but they have a flywheel, so why not integrate the magnets in the flywheel itself? It would also give a lot of flexibility and options (ie more current or more voltage). IMHO I would shoot for something like 5V at 500mA, because that would be of greatest use in an emergency situation.
     
  10. Pommie

    Pommie Well-Known Member Most Helpful Member

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    Here's a 1993 article on using TEGs. It might be of interest.

    Edit, I've uploaded the file twice but it isn't showing? Is there something wrong with uploads or can others see it?

    Mike.
     
  11. JimB

    JimB Super Moderator Most Helpful Member

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    No, I cannot see your upload either.

    JimB
     
  12. Pommie

    Pommie Well-Known Member Most Helpful Member

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    I uploaded the same file here. Guess there's something wrong with the site.

    Mike.
     
  13. Overclocked

    Overclocked Member

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    Reuploading.

    I was stuck between either buying a small pump or buying one. I ended up buying one from china. I could make one very easily and it would give great flexiblity in motor options, but right now its just a proof of concept (And just an experiment for curiosities sake). This is the one :

    http://www.ebay.com/itm/Good-Mini-W.../231227643245?pt=BI_Pumps&hash=item35d63dd56d

    I'll have to test it when I get it to see how much current it consumes. I plan on using PWM or a boost converter for it. Possibly even a small micro with temperature sensing to adjust a PWM signal for the motor.

    I have to get my vice re-ground down for the mill, its off by 15 thou on either side.
     

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  14. Overclocked

    Overclocked Member

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    Hi everyone. Im just about 75% done working on the plans for the waterblock. I got the pump that I bought (it took quite a while) and tested it. It puts out a fair amount of water, I havent timed it against a given amount of water though. It will work down to 3V.

    Ive been thinking about goals I would like to accomplish with this project, this is one idea I had:

    • Some kind of closed loop control. A temperature sensor feeding into a PIC would dictate a PWM signal to the pump, to pump more water or less water. It would also send a PWM signal to a fan for a radiator. Even a simple 555 timer circuit with a NTC thermistor would work.
    I have to remember the first rule of thermodynamics. The energy comes from what ever heat source I am using to generate electricity. So If I use as little as possible to cool things off, I will have a net benefit of electricity (but still a overall loss as far as heat is concerned) . The Fan, and pump all take a little energy to run. The Key is to minimize that energy so I can still use what ever is left to do something useful.
     
  15. Overclocked

    Overclocked Member

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    Little update for those who are following. I got off my butt and actually did something. I broke a end mill in the process (1/8th endmills are very thin..). Got another one and continued milling. I eyeballed everything, as I havent installed the Y-DRO on my mill yet (sort of, I did lay out the holes with a caliper and marker). Im waiting for the loctite to dry and then I can leak test it tomorrow. I have a feeling it will leak.

    I tested out the pump. The max amount of current it consumes at 3.3v is 140mA, with the min being at 110mA. I had it pump out 500mL of water, which took 47 seconds, which comes out to be 10.6mL a second. I dont know how useful that metric is but its something.
     

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  16. Overclocked

    Overclocked Member

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    Really quick post, I'll get to photos later but I have a result to share. The pump was powered by 1 LiFePO4 Battery, I was able to generate 5V at 500mA into a 10 Ohm load using a propane torch on the hot side (the little 1/4w resistor couldnt take much more, it started smoking). I initially used cold tap water, but it quickly became warm. Obviously this opens up to phase 3 (2?)..which would be to make a radiator. I plan on using small copper pipe, 1/8th in diameter.

    The waterblock leaks..not too much of a problem, I have to get some silicone sealant or cut a O-Ring gasket (but I would need a round nose end mill).
     
  17. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Not sure why. Lots of O-rings go into grooves with square walls.

    As for the copper piece, I forgot to ask. Is that pure copper or tellurium ("machinable") copper. I got some of the machinable copper several years ago. I don't know if it is still available, but it sure helps.

    John
     
  18. Overclocked

    Overclocked Member

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    True. I do have a 1/8th endmill. I could get 1/8th thick o-ring cord from mcmaster and do it that way. Luckily I could also get the copper tube I need (its the same price as onlinemetals).

    I used C110 copper. Beryllium copper is the one to watch out for, because as you machine it, the dust is hazardous. According the some of the machining websites I belong to, its a little bit more yellowish in color.
     
  19. Joe G

    Joe G Member

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    as jpanholt stated, why, almost all the o-ring grooves I've done have been a flat bottom groove, You need to allow some "squish" for the o-ring to seal. Like 5-1% of the thickness depending on the application. I've even added a tapered side so it seals in one direction but tends to release in the other.
     
  20. Overclocked

    Overclocked Member

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    I ordered some O-Ring material, but I got 1/8th thick stuff, only because I have a 1/8th endmill and didnt want to splurge on a smaller endmill. Its slightly too large though, so I might have to go smaller.

    Now heres a interesting question. I was going to make a radiator, like a car radiator (multiple tubes separated by 2 tubes at the ends) but now Im wondering what if I take a straight peice of copper pipe and coil it? I would think it would have more surface area to cool the water down with a fan blowing through it.
     
  21. Joe G

    Joe G Member

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    have you ever seen a "heat exchanger", some are just basically just small tubes in a cylinder with a coolant flowing through the larger cylinder, cooling the smaller tubes.
     

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