The principle of TEC is the Peltier effect. When the current passes through a circuit composed of different conductors, there are endothermic and exothermic phenomenon at the joint of each conductor.

Figure 1-1 is a diagram of a TEC. When voltage is applied at the two sides, the electrons travel through Copper to P-type semiconductor, N-type semiconductor, then back to Copper. Due to the energy level transition of electrons, there is heating or cooling at the joint. When the direction of current changes, the heating and cooling sides exchange. The heat absorbed and released is proportional to the current intensity, and is related to the properties of the two conductors and the temperature of the hot end.

Figure 1-1 Structure of TEC Element