Today I made a compact thermal electric generator ( TEG ) using a thermal electric cooler ( TEC a.k.a Peltier device ) and a Joule Thief.
This TEC produces about 1.8VDC when heated on one side and cooled on the other (this setup uses a candle as the heat source and cooling is from ambient air). The advantage of using the Joules Thief circuit in this setup is that it will boost low voltages to higher usable voltages. The open circuit output voltage of the Joule Thief in this circuit was about 31V Peak. It takes about 14VDC to forward bias and light the four LEDs.
The down side of this circuit is that there are conversion losses, but still it costs a lot less to buy one TEC then to buy nine of them and put them in series to get to the voltage required.
From the time I light the candle it takes ~36 seconds to light the LEDs, and they continue to get brighter from there. The LEDs stay lit for ~2 minutes after I blow the candle out, as the residual heat moves from the bottom heat sink through the TEC to the top heat sink, not shown in the video.
Here is a video of the circuit in operation:
Here is a picture of the major components, from left to right: top heat sink, thermal electric cooler, Joule Thief, bottom heat sink, and candle. (to see full size images click images, then click image on following page, still have to figure out why you have to do this to get a full size image? )
Here is a picture of the assembled cooler and heat sinks, I added several pieces of 12AWG solid wire and a 3/4inch copper coupler to direct the heat.
Here is a picture of the TEC Generator connected directly to a DMM without the Joule Thief boost circuit. The DMM is reading 1.792 VDC
And here the circuit is operation, producing ~14VDC to light four white LEDs. :