Need help finding way to step up ~0.1v to 3v

[Imperf3kt]

I hope this isn't too off topic for this forum, but I need some help finding a way to step up about 0.1v to anywhere over 3v and googling is showing the lowest value around 0.5v

Some context may help

I'm trying to use a TEG, Thermo Electric Generator, to cool my Pi.
The idea is the TEG consumes the excess heat put off by the SOC and converts it into electrical energy, thereby removing heat from the SOC and "cooling" it by spreading the heat into the surrounding atmosphere.

The energy produced harvested, then powers a fan which blows against a largish heatsink in order to retain a Thermal Delta of 20°C or more.
The TEG specs are hereń

Specifications
Model:SP1848-27145
Color :white
Lead Length: about 30CM
Size: 40MM * 40MM* 3.4MM
20 degree temperature difference: open-circuit voltage 0.97V, generated current: 225MA
40 degree temperature difference: open circuit voltage 1.8V, generated current: 368MA
60 degree temperature difference: open circuit voltage 2.4V, generated current: 469MA
80 degree temperature difference: the open circuit voltage 3.6V, generated current: 558MA
100 degree temperature difference: open circuit voltage 4.8V, generated current: 669MA

I have no idea how to interpret open circuit voltage, but I know that when I set it up and run CPU BURN on my Pi, it only generates 0.16v and so my fan never turns on, the thermal delta is not maintained and I end up with a thermally throttling Pi after ten minutes. (after which, a very disappointed me takes the contraption apart and near breaks his monitor after instinctively throwing the scaldingly hot chunk of aluminium he just picked up )

The fan only requires about 0.15A @5v and I have tested it to work as low as 1.5v


I figured if I could step the voltage up enough to get the fan to turn, it might work, but I am not able to get the required voltage for the fan to work.


Anybody got any ideas or should I abandon this silly idea?
I can always use it as a TEC.

[Heater]

Imperf3kt,

"Open circuit" voltage is the voltage you will measure on the TEG output when there is nothing connected, no load (except your meter which we can assume has a high input resistance). The output voltage will drop as ever increasing loads are applied.

This works the same as batteries and other supplies. Try measuring a battery voltage when "open circuit" and when a lamp is connected.

If your fan requires 0.15 amps at 5v then it will consume a power of 0.15 * 5 = 0.75 watts.

If your TEG can deliver 225ma then it's output voltage will probably have dropped very low, say 0.1v. It will then be delivering a power of 0.1 * 0.225 = 0.0225 watts

That is 0.75 / 0.0225 = 33 times less than your fan needs. It will not spin. You should forget this silly idea.

If you were to add a voltage step up circuit it would still not work. Power in watts is volts * amps. There is only so much power available, so if you step up the voltage the available current will be proportionately less. It still won't work.

On the other hand, TEG and energy harvesting (to power very low power circuits) is a very interesting subject. If you want to learn how to get a useful voltage and some energy out of a TEG watch this video by Dave Jones: "Peltier TEG Energy Harvesting Experiments": https://www.youtube.com/watch?v=9aSPopIcKLQ

One trick is that you can store the energy from such a device into a battery super capacitor over a long period of time. When it has sufficient energy that can be used to power a circuit for a brief time. Perhaps some IoT gadget that takes a measurement of something and sends out a message every time it has harvested enough energy to do so.

[Imperf3kt]

Thanks. Confirmed my suspicions.
I knew that an open circuit voltage would drop once a load is connected, and that's all I knew. I didn't know by how much.
I had hoped there would be enough to step up and still have enough current.

Oh well. I guess it's back to finding another use for these TEGs.
Perhaps I can use the energy for something still. Hmmm.