Thermoelectric modules are solid-state heat pumps that operate on the Peltier effect ( A thermoelectric module consists of an array of p- and n- type semiconductor elements heavily doped with electrical carriers. The array of elements is soldered so that it is electrically connected in series and thermally connected in parallel. This array is then affixed to two ceramic substrates, one on each side of the elements (Figure 1).
Electrons can travel freely in the copper conductors but not so freely in the semiconductor. As the electrons leave the copper and enter the hot-side of the p-type, they must fill a "hole" in order to move through the p-type. When the electrons fill a hole, they drop down to a lower energy level and release heat in the process. Essentially the holes in the p-type are moving from the cold side to the hot side. Then, as the electrons move from the p-type into the copper conductor on the cold side, the electrons are bumped back to a higher energy level and absorb heat in the process. Next, the electrons move freely through the copper until they reach the cold side of the n-type semiconductor. When the electrons move into the n-type, they must bump up an energy level in order to move through the semiconductor. Heat is absorbed when this occurs. Finally, when the electrons leave the hot-side of the n-type, they can move freely in the copper. They drop down to a lower energy level and release heat in the process.
What are the advantages of a thermoelectric unit over a compressor?
Thermoelectric modules have no moving parts and do not require the use of chlorofluorocarbons. Therefore they are inherently reliable and are virtually maintenance free. They can be operated in any orientation and are ideal for cooling devices that may be sensitive to mechanical vibration. Their compact size also makes them ideal for applications that are size or weight limited where even the smallest compressor would have excess capacity. Their ability to heat and cool lends them to applications where both heating and cooling is necessary or where precise temperature control is critical.
Typical applications for thermoelectric coolers include:
- Laser diodes
- Laboratory instruments
- Temperature baths
- Electronic enclosures
- Telecommunications equipment