I'm generating some power so it's time to try to use it. I'm using the LTC3108-1 step up converter which appears to be a fairly recognizable choice for energy harvesting applications. Normal buck-boost converters won't work for this application as the voltage produced is too low. This chip is able to work with voltages between 20mV to 500mV.

This is the circuit I'm going with, except I am only using Vout. There are some different sources available and a status pin that I won't be needing. An output voltage of 2.5V, 3V, 3.7V, or 4.5V can be selected based on what VS1 and VS2 is tied to. You can refer to the datasheet for more information and an idea of how it works.

I tried taking the output and applying it to the heat sink fan and to some small DC motors, but didn't have much luck. The motor would ever so slightly turn before the output voltage began to rapidly drop to 0V. The supercapacitor on Vstore didn't seem to help the issue as it would not charge to 4.5V (which I will discuss later).

I tried thinking smaller and put an LED and 200ohms of resistance at the output. Connecting it would have the LED start bright and eventually stabilize at a dim light level. I was only getting 1.5V at the output. With 8.3mA through the LED, it appears I was able to generate 12.5mW maximum from the TEG. I should be able to improve this with thermal paste between the TEG and the heat source and sink, and possibly some insulation on the unused surfaces of the copper.

It is pretty clear though that with such limited power it won't be ideal or possible to run a microcontroller and fan constantly. I've got some ideas on efficient uses of power that can still make this a useful device.