Well, I definitely overestimated what one of these small TEG units could do, and my goals were a bit too ambitious. At least I was able to achieve a bit of what I set out to do. While it doesn't really generate much meaningful energy, at least it functions fairly well as a temperature alarm.

This project had no shortage of hurdles and design changes, but with those a lot of learning happened. It was a fun exercise in designing and troubleshooting. This is one of the few projects I've done with only analog circuitry, and it's made me appreciate projects where I don't need to worry about how much energy it uses.

Things to improve:

1. Copper conductor was too thick. Too much energy/time wasted heating all of the copper. The copper remaining warm for a long time after use did not benefit me as it was not usable to generate more energy.

2. Circuitry was not as optimized as it could have been, particularly the thermistor that was used to remove the offset caused by ambient temperature. I did not have time/desire to dial in the resistor values to maximize stability.

3. TEGs require some serious temperature differential to generate a meaningful amount of energy. I will have to try to find a copper mug to see how well that does. There never was much hope trying to harvest heat from the side of an insulator.

Even though the device doesn't really save much energy at all, at least it is something I can use and show off to guests.

Cheers!