How do thermoelectric generators convert heat directly into electricity?

Thermoelectric generators convert heat directly into electricity through the Seebeck effect, a phenomenon discovered by Thomas Johann Seebeck in 1821.1

The process relies on a temperature differential maintained across a device composed of dissimilar materials, typically p-type and n-type semiconductors. When one side of the device is exposed to a heat source and the other to a cooler heat sink, the resulting temperature gradient drives electrons across the junctions. This movement of electrons creates a voltage, which produces direct current when an electrical load is connected to the circuit.231

Because this process involves no intermediate mechanical energy conversion, it is classified as direct power conversion. The efficiency of the device is determined by the Seebeck coefficient of the materials used, as well as their electrical resistivity and thermal conductivity. These generators are particularly valued for their reliability in remote or isolated environments, such as in space exploration.23