Peltier Cooling Plates work on the principle of the Peltier Effect. The Peltier Effect states that when a voltage is applied across a thermoelectric junction heat is generated on one side and cooling occurs on the other side.
The device has two sides. Heat is brought from one side to the other. If the heat from the hot side is removed by means of a heat sink, the temperature of the cool side will fall significantly.
When the plates are used in cascade, the temperature can be lowered to very low values.
Peltier Plates are use to cool components such as ICs, power transistors, etc. Peltier Cooling Plates are also used for portable refrigerators which can be used in cars and in camping.
Peltier Plates are compact and can be designed in very small sizes. The downside is their low efficiency.