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Dear world: thermo electric generators

September 25th, 2008 · No Comments

I’m thinking about trying to make a thermo electric generator, but I’m not coming up with anyone who’s actually done it before.  Do you know anyone who’s used chips like these – http://www.hi-z.com/hz20.php on a woodstove or other hot thing to charge batteries?  If you do, I really really really really really want to talk to them.

(Okay, now scroll down and keep reading)

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0 responses so far ↓

  • 1 NathanSt // Sep 25, 2008 at 10:39 pm

    I think you might want to look at this:

    http://en.wikipedia.org/wiki/MicroCHP

    “micro combined heat and power” units

  • 2 Jeff // Sep 26, 2008 at 4:29 am

    Here’s a coincidence: thermoelectrics is my job. I work for these guys:

    http://www.melcor.com/index_melcor.html

    We make a few thermoelectric modules that can be used to generate power, but there isn’t a huge market for it. This company makes thermoelectric off-grid power sources for natural gas pipelines:

    http://www.globalte.com

    There’s also a project where Philips has prototyped a woodstove that uses thermoelectrics to power a fan, which blows air into the wood to make the stove more efficient and less smoky. Wonderful stuff.

    There’s not much power available, and the parts are very costly. Let me know how I can help you follow up.

  • 3 HoboStripper // Sep 26, 2008 at 5:41 am

    OMG, all the best people read my blog! Jeff, is it okay if I email you? I have questions about two specific chips, and temperature stuff.

  • 4 Anthony // Sep 26, 2008 at 8:42 am

    I’ve investigated these from time to time. In the Maine ( or Alaska ) winters, they’d be as efficient as they’re going to get, but that’s not terribly. If you don’t have to pay (much) for the fuel, and you don’t need much electricity, which is, I think, your case, Tara, then it might work out well for you.

  • 5 Mike // Sep 26, 2008 at 11:42 am

    Another link for you to check out. I used to dig into seebeck generators quite a bit. A woodstove is a pretty decent application for it. Obviously Jeff is probably the one to talk to but maybe this will be of help as well.

    http://tinyurl.com/54hblf

    -Mike

  • 6 Randy // Sep 26, 2008 at 12:51 pm

    That looks like just a peltier.(pretty cheap but low power , can get them on ebay) your still going to need a converter to make it usable, and alot of then is going to be needed to get any useable power out of them. but a diy one might get a bit pricey fast.

    You might want to consider a Stirling engine to power a generator motor it will be bigger and not very portable but would be cheaper and more people have diy guides out there for them.

    http://en.wikipedia.org/wiki/Stirling_engine

    http://en.wikipedia.org/wiki/Thermoelectric_effect

  • 7 judyofthewoods // Sep 26, 2008 at 4:13 pm

    Here is an interesting website on thermoelectric
    generators
    . Not sure what the latest is on availability. Certainly looks good. Then there is the refrigerator-stove-generator concept known as SCORE (Stove for COoking, Refrigeration and Electricity supply). Two more links on SCORE –

    Link 1

    Link 2

  • 8 Mags // Sep 26, 2008 at 4:46 pm

    Tara, They produce very little power at low voltage DC. 30 watts at 2.4 v while heated at 230’C or 450’F. I think this would be a ton of work and other components for little power. I think I’d look at little windmills batteries if you’re in a windy area.

  • 9 HoboStripper // Sep 26, 2008 at 9:43 pm

    Judy, thanks.

    Mike, that’s perfect! I paid the thirty dollars for the article, and it’s pretty vague, but it’s still sooo much more information than I had! Thanks! How the heck did you find it?

    Mags, actually there are a wide variety of chips available that produce a wide variety of electricity. It is at least possible to get 15v/80w out of one chip. I think if you look around a little you’ll be pleasantly suprised. 🙂

  • 10 Mike // Sep 27, 2008 at 6:12 am

    Hope it really is of help Tara, I found it with a google search using the string “seebeck generator wood stove”

    -Mike

  • 11 Jeff // Sep 28, 2008 at 6:27 am

    Thanks for the link to Varmaraf, I’m always on the lookout for that sort of thing. There are three big companies in thermoelectrics (Marlow, Laird/Melcor, and Ferrotec) and hundreds of little companies all over the world.

    A Peltier cooler chip can be used as a Seebeck generator. When used as a cooler, you’re pushing electricity through it, causing it to get cold on one side. When used as a generator, you’re keeping one side cold and the other side hot, and it produces electricity.

    Using a typical chip (30x30mm) from my company, if you held one side at the temperature of boiling water and the other side at room temperature, you would produce a little over a watt. The open circuit voltage would be 3-4 volts, but that decreases when you draw current from it. The power depends mainly on the temperature difference between the hot side and the cold side of the chip.

    The hard part is keeping the hot side hot and the cold side cold. It’s remarkably difficult. For example, just letting the cold side hang in the air won’t keep it at room temperature–it’ll warm up a lot, which decreases the temperature difference, decreasing your power output. You usually need a heatsink and a fan, or even water cooling.

    Tara, you can email me. Sorry I took a while to get back to you.

  • 12 BoB // Sep 29, 2008 at 8:36 pm

    I’ve got a ton of labbooks to grade and am about done procrastinating, but here’s my two cents…

    The process is reversible, conservation of energy and all that. In semiconductors neat things happen between heat energy and available electrons in the conduction band. The efficiency is low, sure, but you’ve got plenty of waste heat from a woodstove. I’d think that it may be possible to use the heat from the stove pipe and if the bit about keeping the cool side cool is accurate, then put these magic (as in sufficiently advanced technology, I’ve taken some grad level semiconductor physics classes and still don’t really understand it) boxes out in the ambient air. I have no reason to believe that this information is wrong, difference in temperature is what defines the efficiency of coal or natural gas or nuclear power stations and may well effect the efficiency here.

    If pressed, I’ll look into it further. It may take more time than you have, I need to get the roof done on the house before the snow flies.

  • 13 BoB // Sep 29, 2008 at 8:45 pm

    OK, re-read Jeff’s post.

    Boiling water is 212F and room temperature is 70F? So about 140F difference. How hot is a stove pipe?

    I think the exhaust gas temperature should go down as you’re burning more efficiently, so it’s a trade off between efficiency from your fuel and efficiency from your power generation.

    Every little bit helps, though. And with batteries to store the energy, a combination of solar/wind/TE can get you some power all of the time.

    Have fun with it.

  • 14 Jon // Dec 4, 2009 at 5:40 pm

    I’ve been thinking about using a TEC module on the outside of my stovepipe (outside). Winters here are about 20 Degrees and a stovepipe is much hotter than that. Do you think that would work?

  • 15 HoboStripper // Dec 15, 2009 at 2:42 pm

    It would work, but, two problems –

    1 – the module has to be extremely flat and pressurized. I’m sure you could fabricate something, but if you just slap it up there it’s not gonna work so well.

    2 – it turns out they really don’t make much electricity. If you’re already used to no/limited electricity and you just want enough to charge your cell phone or use your laptop for ten minutes, go ahead and use them. But if you’re thinking they’ll provide lights and stuff, or even half as much as a solar panel, you’ll be very disappointed.

  • 16 jim // Jan 22, 2010 at 11:43 pm

    i thought that an arangement of a upside down square can with a candel under it and the can coverded with heat mods and thermal paste could do a good job the candel creates a thermal cline inside of the cans and a small flame would go a long way to power. inside of the can the heat has noware to go but out thu the mods

  • 17 HoboStripper // Jan 23, 2010 at 2:44 pm

    First, what would keep the outside of the chips cool? The heat on the one side of the chip will heat it through and then there won’t be a temperature difference.

    Second, I think you’ll be suprised at how little electricity you get from a set up like that.

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