# Which thermoelectric effect is better?

I am doing an experiment which requires the thermoelectric effect. I know about the Seebeck and the Peltier effects. Well, from what I have found till now on these topics is that they both can produce electricity through temperature differences and both can produce heat or cold through electricity, but have different ways of doing it. Can anybody tell me the comparison between both of them based on their pros and cons. I don't want to go very deep into this topic right now, but I just want to ask that if I have to buy a Peltier's or Seebeck's electricity generating module, then which one will be better. By better I mean what is the difference between the amount of power they generate and the difference between their costs.

If you're looking to produce power from a temperature differential, go with a device optimized for the Seebeck effect. Peltier and Seebeck effects are essentially the same thing, or rather flip sides of the same thing, but thermoelectric generators (Seebeck) are optimized differently from thermoelectric coolers (Peltier).

• thank you, but can you tell me what will be the difference in the costs of both? – Ishpreet Apr 3 '14 at 7:12

The Peltier and Seebeck effects are each others opposites so to say.

• The Seebeck effect is described by the electromotive force or voltage $V$ generated at a temperature difference $\Delta T$ across the ends of a material: $$V=S\Delta T$$ $S$ is the Seebech coefficient and is a material constant that depends on charge carriers, material density and much more.

• The Peltie effect is the generation of a heat flow $Q$ from one junction to the other (heating of one end while cooling of the other) of a unicouple when a current $I$ flows: $$Q=\Pi I$$ A unicouple is simply two fitting materials (semiconductors) that are put together end to end. $\Pi$ is the Peltier coefficient, which is a property of the unicouple.

Now, both a "Seebeck module" and a "Peltier module" can be reversed. They are both build as several unicouples in electric series (which is called a module). Apply a voltage to the Seebeck module and you get cooling/heating. Apply a temperature difference across a Peltier module and you get a voltage difference.

But as has been said in another answer, since the two modules are intended for each specific purpose, they might have been optimized only two that specific use. In the Seebeck module the Seebeck coefficient of the materials might be prioritized, even if it might mean some damage done to the peltier coefficient. And vice versa. Therefore, pick a Seebeck module for power generation.

The temperature range that you are going to use the module in has a large influence on the coefficients of materials. Look out for that specification.

• Could you specify your sentence " In the Seebeck module the Seebeck coefficient of the materials might be prioritized, even if it might mean some damage done to the peltier coefficient. And vice versa."? As far as I understand, they are linked through Kelvin relation $\Pi = ST$, so a "damage" to either $S$ or $\Pi$ looks like a damage on the other one. – thermomagnetic condensed boson Sep 18 '18 at 12:06