Rules of Thumb for TEGs
- ZT for typical devices manufactured today by any company is between 0.5 and 1.0. Keep in mind this is device ZT, not material ZT. You can have a higher material ZT but by the time you account for condition between the TE elements, and other losses, the device ZT will always be lower.
- To design a waste heat recovery system where the waste heat is a hot exhaust stream, first design your hot side and cold side heat exchangers. The thermal resistance of the TEG will be approximately equal to the sum of the hot and cold side heat exchangers. This will also dictate the temperature drop across the TEG.
- Because of the thermal resistances on either side of the TEG, the temperature drop across the TEG will always be lower than the system temperature difference.
Some equations you will need:
