Thermoelectricity demonstrates the direct conversion of heat into electrical energy using the Seebeck effect. As in solar cells, electricity is generated directly through processes at the atomic level without moving mechanical parts. The atomic oscillations coupled with heat lead to a gradient in the distribution of electrons and thus to an electrical voltage. Further information about the Seebeck effect can be found here: Thermoelectricity

The actual conversion of heat into electricity takes place in the Peltier element. One side of this flat element is heated and the other is cooled. This means that a heat flow at a higher temperature is directed to the Peltier element and a smaller heat flow at a lower temperature is directed away from the Peltier element. The difference between these heat flows corresponds approximately to the electrical energy generated. ​