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I am building an experimental thermopile, and I'm getting confused with the definitions for the Seebeck effect and Pettier effects.

From Wikipedia:

The Seebeck effect:

The Seebeck effect is the conversion of heat directly into electricity at the junction of different types of wire. It is named after the Baltic German physicist Thomas Johann Seebeck, who in 1821 discovered that a compass needle would be deflected by a closed loop formed by two different metals joined in two places, with a temperature difference between the joints.

The Peltier effect:

The Peltier effect is the presence of heating or cooling at an electrified junction of two different conductors and is named after French physicist Jean Charles Athanase Peltier, who discovered it in 1834. When a current is made to flow through a junction between two conductors, A and B, heat may be generated or removed at the junction.

The Peltier effect has been shown to be 'reversible' - in the sense that if the temperature of one side of a Peltier element is elevated with respect to the other side, a current is generated.

Is the Peltier effect the dual of the Seebeck effect?

Also, for the purpose of producing voltage and current from thermal energy, is it better to use the Seebeck effect or the Peltier effect - if one is "better" than the other (i.e. produces more voltage and current for a given temperature differential), what is the scientific reason for that?

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  • $\begingroup$ "Is the Peltier effect the dual of the Seebeck effect?" Yes, as it says in your link: "The Peltier effect can be considered as the back-action counterpart to the Seebeck effect" $\endgroup$ – endolith Mar 9 '17 at 17:18
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Short answer: Basically all the same. It is different observation due to the same thermoelectric effect

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Addressing the first question :

Is the Peltier effect the dual of the Seebeck effect?

Not quite. The Peltier effect requires two dissimilar materials, whereas the Seebeck effect does not have this requirement. One may argue that it's possible to think about the Thomson effect as a spatially continuous Peltier effect, within a single material, but then there is still the need of having a current, while the current is not a necessity for the Seebeck effect to take place. So the real answer is no.

However, many people use the Seebeck effect (that creates a potential difference, or voltage) to create a current to power on some device. In that case a $\Delta T$ creates a current $I$. While a Peltier module works with some input current $I$ in order to produce a temperature difference $\Delta T$. So in that loose way, it may be possible to think of the Peltier effect as the "dual" of the Seebeck effect even though they are not strictly the inverse or opposite of one another.

Onto your second question:

for the purpose of producing voltage and current from thermal energy, is it better to use the Seebeck effect or the Peltier effect - if one is "better" than the other (i.e. produces more voltage and current for a given temperature differential), what is the scientific reason for that?

It should be clear from the description above that in that case the Seebeck effect is the relevant one. The reason is that the Peltier effect needs an input current to produce an output temperature difference, which is not what you're looking for. The Seebeck effect on the other hand needs a temperature gradient (or more loosely speaking, a $\Delta T$) to produce a voltage and possibly a current (assuming you use a closed circuit), which is exactly what you're looking for.

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  • $\begingroup$ "requires two materials to manifest itself". This is not a clear statement in English. Please clarify. $\endgroup$ – Homunculus Reticulli Sep 18 '18 at 15:13
  • $\begingroup$ @HomunculusReticulli "requires two materials to occur". Is that clearer? If so, you can edit my answer, or I'll do it myself. Please let me know! $\endgroup$ – thermomagnetic condensed boson Sep 18 '18 at 17:52
  • $\begingroup$ Ok. I will edit it as per my understanding. $\endgroup$ – Homunculus Reticulli Sep 18 '18 at 18:59
  • $\begingroup$ I approved your edit, but changed "separate" to "dissimilar", as it is a standard use in that field (thermoelectricity). $\endgroup$ – thermomagnetic condensed boson Sep 18 '18 at 19:20
  • $\begingroup$ Lol, your English is better than mine! :) $\endgroup$ – Homunculus Reticulli Sep 18 '18 at 19:20

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