Thermoelectric power generation is conducted, as in the diagram, by using a unit element that has a connected P-type semiconductor and N-type semiconductor. If one side of the unit is maintained at high temperature, and the other at low temperature, a heat flow will develop across the unit from the high temperature side to the low.
In other words, heat energy will flow into the element from the high temperature side and be discharged from the low temperature side. At this point, part of the heat energy flowing through the element will not be discharged but transformed into electrical energy, and can be taken as electric power by an external load as shown on the diagram. In this way, by connecting multiple unit elements of this kind, it is possible to obtain a greater amount of electric power.