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Peltier-element: Limiting its heat by tapping the power? Answered


I have a question based upon logics and the function of a peltier-element.

we all know, that you can supply power to a peltier-element to raise the temperature on it one side and lowering it on the other. So it increases the differential.

Now: If we heat the "cool" side and try to radiate the heat off the hot side (eg cooling it a bit), we can get a small amount of energy off the peltier as electrical current. The current depends on the temperature-differential: The bigger the more.
OK so far. Nothing new.

But what made me think was the fact, that you have 2 opposite states:
Heat Side C and cool side H --> Get energy out in proportion of heat-differential.
Put energy in --> Side C gets cooler and side H gets hotter in proportion of energy supplyed.

By getting energy OFF the peltier, you in some way, redirect some parts of the heating-energy to the electrical-output. Also that is nothing new and we all know that since energy cannot be generated but only converted (in our case from thermal energy to electrical energy).

Now what puzzles me is: Does it actually affect the temperature (-differential) of the peltier, if you get energy off it?

Lets imagine the following experiment:
- You build something like in https://www.instructables.com/id/Candle-Powered-Electric-Candle/
- Now you disconnect the load (lamp) and measure the temperature on the upper side (Away from the candle).
- Wait for a steady-state when the upper side doesn't get hotter
- Now turn on the lamp thus redirecting a bit of energy away from the peltier.
- measure the temperature again on the upper side.

Does it lower the upper temperature a bit? of course it wont be lower than the unheated state. But lets say the steady state was 55°C. Would it be like 50°C if i switch on the lamp?


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8 years ago

Of course it does, otherwise there would be no flow of energy. Thermodynamics.


Reply 8 years ago

Thanks for the confirmation! :)