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Thread: thermoelectric power

  1. #1
    Member BrowningLeverAction's Avatar
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    Default thermoelectric power

    I am looking at several options for power at my weekend cabin and am wondering if anyone out there has any experience with using a thermoelectric cell running off of a woodstove? Is it feasible to use to trickle charge batteries, what kind of power output, what temperature difference is necessary, etc. I am not too keen on running a generator all the time and am not sure if I will get enough sun in the winter to make solar an effective option (Cabin is up near Lake Louise). I will (eventually) be running a DC setup with an inverter for certain AC needs.

  2. #2

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    How does a thermoelectric cell work? Do you have a link for info?

  3. #3

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    Think wind

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    Member BrowningLeverAction's Avatar
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    Default some thermoelectric links

    I don't have any direct experience with thermoelectric cells except the little "Ecofans" that sit on top of a stove. Those are driven by a small thermoelectric cell. The theory is that a cell of 2 dissimilar metals with a "hot side" that is heated and a "cold side" in a cooler area will generate an electrical current. You can also apply current to the cell to create a refrigerant effect. I was hoping that someone on the forum knows a little more than me about this subject. All of the cells I have looked into so far seem to put out very low voltage and I am not sure if they can be wired in series to increase the output. I am also not sure what kind of temp difference is necessary for efficient operation. Here are some links to products and the theory behind it:

    http://www.repp.org/discussiongroups...ETHOS_2005.pdf

    http://www.thermoelectrics.com/introduction.htm

    http://www.thermoelectricsupplier.com/

    http://www.hi-z.com/


    Dogfish, I don't think wind is a good option as there is very little wind in the area most of the time.

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    Member bushrat's Avatar
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    Default Peltier Junctions

    I messed around with Peltier Junctions for a couple winters in the late 80s, using woodstove to heat them, with heatsinks, and ambient air with fan to cool for temp differential. They require a large temp differential, 100+degrees really. Since then the Peltier modules have come a long way but there is still nothing I know of commercially produced for small scale home power use. However there are products currently being tested and supposed to be available soon; the one I know of slips over stovepipe and uses a liquid coolant instead of air, puts out about twenty watts. Company is still testing it. It won't be cheap. Large scale TEG (thermoelectic generators) have been in use for some time to power remote sites, using propane to heat. Very expensive. Industry is now utilizing waste heat from many things (car exhaust for example) to power low-power devices using small TEG units.

    The principle comes from a guy named Seebeck as I recall, a darn smart dude doing experiments on the conjoining of dissimilar metals in the 1800s. If you wire together dissimilar metals of certain types in a series and heat one side you will get a small electric current to flow. Similarly if you produce current through them you will get a cooling/heating effect on each end. I may have this a bit off, but the first fridges and coolers used this effect. And if you've ever wondered why it is we have propane powered refridgerators (I did!)...same deal, propane used to heat the peltier junctions to produce cold on one side.

    Anywho...they are fun to play with, easy to burn up (I burned up plenty!), but have a lot of potential. My thoughts when I first started experimenting with them was to use outside subarctic winter air somehow to produce a larger temp differential, but had a hard time doing that...and drilling a 2" hole in the cabin wall behind the stove with a small little computer fan worked to blow cold air over the junctions but also sent forty below air into the cabin. I think liquid coolant is the way to go.
    Good luck, (ps, Browninglever, we posted at same time)

  6. #6
    Member bushrat's Avatar
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    Default BrowningLever...

    BLA,

    Yes you can wire the modules in series to get more voltage. You can parallel them too. In my experience so far they are too spendy and too fragile to really get any sustainable amount of even trickle charge. Thought about trying again using heat sinks that were cooled by water. If you have an ecofan, sometime try spraying top of heatsink with water...amazing difference in getting fan to spin and it spins faster <grin>. Somewhere in a box I have all the temp data from the experiments from the late 80s, with the differentials etc. As I recall, wasn't getting anything at all til 80deg differential, and got full pwer at around 150 or so differential. I think the hi-z link is the outfit I wrote last winter about their stovepipe model...president wrote me back saying they were still working on it. Seems like a great idea.

  7. #7
    Member BrowningLeverAction's Avatar
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    Default Stovepipe

    Bushrat,

    It sounds like you really spent some time playing with these things. I am envisioning using them mostly in the winter when solar isn't as effective, and setting them on top of the stove with a pot of snow on top to get the temperature difference. I may be able to use the batteries to run the cell in reverse for a small refrigeration unit in the summer. The stovepipe model sounds really great, although the expense may put me off. I am going to keep researching. There seems to be a lot of outrageous claims and some crackpot science on the internet regarding this technology.

    Thanks for your experiences!

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    Member dkwarthog's Avatar
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    Default Fwiw

    I've often thought that something like that could work. Thanks Bushrat for the info on your experimentation experience. I'd hate to reinvent the square wheel!!

    FWIW, I've tried to measure the amps/volts on our Ecofan while it was running at max speed and was not able to even get it to register on my fluke so it must be miniscule....like milliamps. My fluke reads to .01 amps.

  9. #9

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    Lots of energy info at BHM website.

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