Thermoelectricity is the field which deals with the relationship between temperature and electricity. Both, thermoelectric generators (TEGs) and thermoelectric coolers (TECs) are based on the thermoelectric effect, which can be subdivided into two effects:
Thermoelectric generator (TEG / Seebeck): If a temperature difference is applied across a TEG module, a voltage is produced. It is known as the Seebeck effect.
Thermoelectric cooler (TEC / Peltier): If a voltage is applied to a TEC module, it will pump heat. It is known as the Peltier effect.
Thermoelectric generators (TEGs)
A TEG module consists of many paired thermoelectric (TE) legs, which are only a few cubic millimeters in size and are made of a semiconductor material. In operation, one side of the module faces the heat source (hot side), while the other side is averted from it (cold side). The temperature difference between the two sides generates a proportional voltage in the thermoelectrically active material. So-called n-type doped and p-type doped materials are employed to utilize the TE properties. In each case, an n-type leg and a p-type leg together form a pair of legs. A large number of such legs are electrically connected in series to generate a suitable voltage.
The energy potential of waste heat generated each year in Germany alone – particularly in heat-intensive industrial processes – is estimated to reach some 300 TWh. So far, this potential has remained largely unexploited, although TEGs represent a smart method for direct conversion of waste heat into electrical energy. These modules are able to generate power from temperature differences, without emissions nor noise, relying on a solid-state effect that has long been known as the Seebeck effect. Although only five percent of the thermal energy can be directly converted in this manner, it makes sense to utilize waste heat as a regenerative source of energy and to boost process efficiency with promising sustainability impact.
Thermoelectric coolers (TECs)
TEC modules use the Peltier effect, for this reason they are often called Peltier modules. Heat pump or solid state refrigerator are other words used for the same. By applying a current on the junction of two different types of materials, a heat flux is created. The direction of the current will define the direction of the heat transfer from one side of the device to the other. Theoretically TECs can be used either for heating or for cooling, in practice, the main application is cooling. It can also be used as a temperature controller that either heats or cools.
Potential applications are all requiring either cooling or temperature control. The primary advantage of TEC/Peltier modules are its lack of moving parts, therefore also low-noise levels, long life, small size, and flexible shapes.