thermo electric generators

[greenkarson]

Not sure if this question should be in heating or here.  but here goes

have a woodstove top ecco fan that runs runs off a little TEG. its works decient but is a little under powered.  the TEG on the fan averages between .5vdc and 1vdc.  when its at 1vdc it works pretty good.  so i found another TEG and a big heat sink and was hoping to wire it into the fan as well hoping to speed it up.  the new TEG when on my stove averages about the same as the one on the fan .5vdc to 1vdc.  but not sure would i wire it up in series or paralel to speed up the electric motor?  any other thoughts?

thanks Karson

[kenobrock]

There is a thermo electric generator being developed that produces electric from a fire. It's called an acoustic generator. Here are some search links where you can read about it. Very interesting. http://www.google.com/search?client=safari&rls=en&q=acoustic+generator&ie=UTF-8&oe=UTF-8

[DanG]

The ecco fans use a module good for 500°F - with graphite gasket/covers. These are rare unless you've purchased the correct spec module.

http://www.tecteg.com/product.php?product=1 has the high temp modules but shipping is $56 for a $30 module.

Are the voltages you are seeing measuring the drop across a running motor?

[madlabs]

I'm assuming a TEG is the same as a Peltier junction?

Well, I didn't know you needed a high temp version when I repaired an Ecco fan. I just got a surplus TEG of the same dimensions from All Electronics, cheap. The fan has been working fine for years since. Maybe I got lucky and the ones they sell are high temp.

Anyway, at the same time I ordered a bunch more to play with. I found you can stack them 3 deep or so before you start seeing a drop in output. Depends on what you are doing with 'em and how hot. At that point they are too hot. Fun little buggers to play with.

As to acoustic generators, I built the reverse which makes sound from substrate and heat. Nifty. Here is my page on that, in case you are bored: http://madlabs.info/acoustic_laser.shtml

Oh, I'd series 'em. Should help it start up sooner and run faster.

Jonathan

[OperaHouse]

We had a gas furnace in our house that had one of these powered from the pilot light. It was nice because the furnace was gravity fed and a power oitagewould not keep the furnace from working.  Of course the rest of the time it used enormous amounts of gas.  That mofule produced about .6V and consisted of about 100 sections of thermocouple wire wekded in series.  each junction produced only a few milivolts.  So it likely isn't the Peltier junction you are thinking about. 

[greenkarson]

decided to stack the new TEG ontop of the original on right on the fan.  Instead of using its own independant heat sink.  used the proper thermal greese between all layers.  wired them in series.  thought i would get roughly twice the voltage of the indepentant TEG.  but not the case.  voltage is staying pretty much the same as with only one TEG.  not sure why this is.  is  it possible that the cooling fins are not big enough for two TEG's?  or is there another issue at play? 
for the record fins do get to hot to touch on the fans heat sink
thanks

[Bruce S]

TEGs run on thermal change or delta T, if the cool side heat sink fins are hot, then you probably do not have enough cooling surfaces.
The cooler you keep the cold side the better the TEG will work.