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Can a small Thermoelectric Generator feasibly power an LED?

I want to make a small LED circuit that consists of a coin cell, an LED, and some sort of touch-sensitive switch. The entire circuit needs to be very small (~3cm³), and there must be no moving parts. The circuit is for a jewelry piece so it doesn't need to act within finely tuned boundaries at all times, all I want is for the LED to glow visibly when the circuit is held.

I've never used TEGs before, but after reading a question from earlier this year I would like to know if a small TEG could be used, essentially to act as both switch and power source. I tried figuring it out but I am still struggling to understand the relevant information on this page and the related datasheets.

I would like to use one in the 10mm - 20mm range if possible, using this as an example. My understanding is that since they work on temperature differences, if a temperature gradient of 68deg / 27deg produces 8.8V, then a typical human/room temperature gradient of 37deg / 27deg would produce around 2.2V, enough to power your typical 1.5V LED.

Am I correct in this assumption?

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    \$\begingroup\$ LEDs need a specific current, not just voltage. How much current can your TEG generate? And I would assume that you won't get it up to body temp unless it is in somebody's armpit. \$\endgroup\$
    – Ron Beyer
    Dec 12, 2017 at 2:44
  • \$\begingroup\$ Well I sure feel silly, I would mention that I'm self-taught, but 'taught' would be an overstatement... If current follows the same guesswork I used for voltage, then it would provide 0.2A, which is more than the 0.05A required for, say, this LED. However I no longer have any confidence in my ignorance-based theories. \$\endgroup\$
    – Bazul
    Dec 12, 2017 at 2:55
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    \$\begingroup\$ While a small (say 2x2 inch) TEG attached to a wood stove can probably power LEDs quite nicely, I'm going to say that an even smaller one, powered by hand heat and air cooling, almost certainly can not. Sorry. \$\endgroup\$
    – user16324
    Dec 12, 2017 at 10:36

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Here is some interesting data from a 30mm RC12-2.5 module. (One of the few that actually publishes the numbers.)

enter image description here

Note the 8mW output at body temps.. You would need closer to 20mW to light up an LED. The optimum voltage produced is also far too small.

Unfortunately, peltiers are much less efficient at generation than they are at cooling.

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