Turning waste heat into electricity

How do thermoelectric generators (TEGs) work?

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 thermoelectric 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. 

Why are thermoelectric generators (TEGs) attractive for waste heat recovery?

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 thermoelectric generators 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.