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Joule Thief in between Peltier/TEG and DC Motor?

As per the title I've got a Peltier cooler chip sandwiched between 2 heat sinks acting as a Thermoelectric generator (TEG) which when sat on my wood burning stove generates about .5V (which is a bit disappointing).  The idea was to cheaply recreate one of the EcoFans, so the plan was to connect the TEG to a low voltage DC motor.  The obvious issue is the low output from the TEG itself - I need to maximise the heat dissipation from the top heatsink to create the temperature difference, but even solving that I'm going to struggle to consistently get more the 1V from the TEG.

Before I go to the hassle of sourcing and making a Joule Thief (like the 1up instructable) is there something fundamental I've missed that means either the TEG won't work with the JT, or a 1.5V - 3V DC motor won't work with the JT?

Appreciate any help is establishing the feasibility of this idea, or suggestions to an alternative solution :-)

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thankyousam (author) 5 years ago
I can now answer my own question. The answer is currently no. The JT spreads the current too thinly as the voltage goes up (at least with my tests with an AA battery powering the JT). I need to experiment with torroid coil windings to see if I can boost the voltage a little, while keeping the current high enough to turn the motor. I only need about 2V, not the 9V the circuit gives me. I also need to put a non LED diode in the circuit to see if the LED is taking some of the current out.

At least I now understand how the JT works and that the diode is essential!
Look out for some "MPPT" regulator circuits - Linear Technology make some good ones.
Wow! I was just trying to do this for my dad! We just put a gas stove in our house and we have a electric fan blowing the air around the room. I'm trying to make my own peltier chip though... Can you post a pic of your design? I have an idea how you can maximize your heat to the peltier chip!
Cheers! -joespicnictables
thankyousam (author)  joespicnictables5 years ago
I've only been playing about to baseline what the TEG can do - it's not really a design ;) .

I got two aluminium solid state relay heatsinks (about 5cm^3): one for the top and one for the bottom. I took all the intermediate fins and mounting bracket from the bottom one (so it's a sideways H) to maximise the heat transfer from the cast iron top of the stove. I need to make the top heatsink much bigger in terms of weight and surface area - placing a 500g cast iron dumbell weight on the top of it made a difference, although this still only gave about .5V.

Putting the chip straight on the stove top with the two heatsinks on top gave about 1.3V dropping to .9V as the heatsinks warmed up.

I think the trick will be minimsing the height the chip is from the stove top, but not getting the top heatsink too close so that it overheats. I've also not thought properly about any thermal paste yet.

I'm not sure how the motor would be mounted. The Ecofans have a tealight size DC motor, which I've not been able to find locally.
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It appears that the EcoFan cools the top heat sink with the air the fan is pulling through it. You could get a small motr out of a old cd drive.