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Referring to this diagram:

Peltier Element

How does the height of the P and N components affect heat or cold generated on this thermoelectric element?

The idea I keep having is that it seems like the hot and cold sides are too close to each other. Would increasing the distance, via lengthening the height of the P and N components help to segregate the differential more or would this decrease the differential produced?

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Here is the problem: the electrical current has to flow through the chunks of junction material. That material has electrical resistance and will therefore heat up as the current flows, negating the cooling effect. So you do not want the P & N chunks to be too thick.

On the other hand, if you make then too thin in response, then it's too easy for heat to flow across the chunks from the hot side to the cold side, short-circuiting the cooling effect.

This means two things: 1) the thickness of the chunks is a compromise between these two competing influences, and 2) the holy grail of this business is a material that simultaneously possesses high electrical conductivity and low thermal conductivity, which are to a great extent contradictory properties.

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  • $\begingroup$ Thank you, could the material be a composite between a ceramic and a semiconductor? $\endgroup$
    – Michael S.
    Dec 9 '18 at 20:22
  • $\begingroup$ I have been out of the loop on research into these things for too long to know. Sorry! $\endgroup$ Dec 9 '18 at 20:38
  • $\begingroup$ In short, yes, it would increase the differential between the hot and cold side; no, it wouldn't make the cold side colder. $\endgroup$
    – SF.
    Dec 10 '18 at 15:05

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