As I mentioned already, I burned my old Peltier element before receiving the LTC3108 breakout PCB, so I couldn’t test that setup. So I went and hooked a solar cell, but the configuration I have on the PCB is not optimal for solar usage: I need another transformer ratio and different capacitor values. I have ordered these components and will build another PCB when they arrive. Luckily, I got the replacement early today and immediately started looking for a suitable place to test it out. I needed to find a place with temperature difference: that is what creates the voltage in the TEG. I have a Popcorn hour A110 networked media player in my living room, aluminium casing and surface temperature of 31 degrees (when off) that is given off by its power supply.
Simply placing the TEG on-top isn’t enough as it quickly equalizes its plates temperatures and doesn’t produce the minimum 20mV to get the LTC3108 started. So I put an old aluminum heat sink from a Intel Celeron processor on top the element and I got steady 38-40mV output since one side is 31 degrees and the other tends to follow room temperature i.e. around 21 degrees C. My TEG is the cheapest found on ebay, probably high quality ones would produce more at 10 degrees difference, but 38-40mV is perfect for the LTC3108, in fact it is most efficient at these voltages. Without load, I got around 70mV from the TEG.
So I plugged everything and it works as a charm, simply *amazing* stuff. This setup works 24hrs a day (unlike solar), so I can even skip the storage capacitor, or use a smaller one – I have a 0.1F (currently using a 1F)