Materials used
What materials are being used to produce thermal electricity. What is efficiency of conversion?
Thermoelectricity / Discussion
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As far as I know, compound material are used for these devices. One challenge is to have p and n type of same semiconducting material. Therefore, heterojunction are made use of mostly. although, Si has well-built infrastructure, bulk si makes very bad thermoelectric device. Efficiency of these devices are very low, which is the major problem that these devices have to overcome. Usually figure of merit ZT is used to for the efficiency and today's devices are working with ZT slightly larger than 1. Here is a ZT to efficiency conversion table:
ZT, efficiency/ carnot efficiency
1, 27 %
2, 40 %
3, 49 %
4, 54 %
Hi, I have two questions. In the Thomson Effect, the electric current can produce net heat. Does the heat all come from the resistance of the conductor? And should the current change to produce the heat, just as the electricity can be produced only if the temperature change?
That is a good question but I don't have a simple answer for you. You maybe right, the only source of heat is the Joule heat but then because of the distribution of heat as a consequence of the thermal resistivity, electrical resistivity, mobility, phonon - phonon interaction, electron - phonon drag, etc; the Thomson heat take place. I will try to precise a simple answer and I will let you know.
If you change the current on the Peltier effect you will change your delta T, changing the polarity of your current you will change the direction of the thermoelectric current, but if you leave your current constant you will keep a constant delta T. For the Seebeck effect, the change in temperature will give you a current, if the delta T increase your current increase too.
Nice page Abdiel,
One question: Heating or cooling at a junction depending on the current direction (Peltier effect) sounds interesting and yet a bit puzzling. How can you cool or heat a junction?
If you apply an electric field to two different materials connected electrically in series and thermally in parallel, the temperature will increase. As a consequence of the phonon - phonon interaction and electron phonon drag, the hot electron will diffuse to the cold end of the material. As a result, one side of the material will have higher temperature than the other side, if the electric field is big enough delta T will provide a cool and a hot junction. This depend also of the properties of the material, Seebeck coefficient and Peltier Coefficient.
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