The use of thermoelectric technology is the most direct way to convert electrical energy into heat transfer. While traditional cooling systems use gas or liquids to transfer heat, the thermoelectric system uses the electrons themselves as the means of transportation.
As this phenomenon is reversible, electrical energy can be obtained when there is heat available; however, since the efficiency of this process is extremely low, there are very few cases when a thermoelectric generator is preferred to a traditional device.
Many years of research aimed at the improvement of the efficiency of the thermoelectric modules, which represent the main component of the unit, and the continuous reduction in their cost are making the application of this technology more and more convenient both in the consumer and industrial fields.
The thermoelectric units are simply small static heat pumps which operate according to the principles discovered by the French physicist Jean-Charles Peltier (1785 - 1845) more than a century ago.
The basic principles of thermodynamics can be applied to these devices just as is done with traditional heat pumps, absorption refrigerators or other heat transfer devices.
The "motor" of the thermoelectric system is represented by the thermoelectric module more commonly known
as the "Peltier module". This module consists
of a certain number of thermocouples, all identical and made of semi-conducting material, with the two components of the couple having different electrical characteristics. These thermocouples are electrically connected in series, and thermally connected in parallel, so as to create different joints. They are then put into a "sandwich", between two very thin ceramic plates which serve both as mechanical support and electrical insulation.
The system starts up when tension is given to both ends of the circuit. As soon as current flows through, one side of the element cools (gives off energy to the opposite side) and the other side heats up (absorbs energy from the cold side).
This phenomenon can be reversed simply
by inverting the direction of the current flow. The modules can be manufactured in different dimensions, power supply voltages, current inputs, number of thermocouples and cooling capacities.
This phenomenon uses the physical law in which the speed of the movement of the electrons depends on the material through which they are passing. The following drawing shows the reaction of the electrons during their passing through an electric circuit made of equal metal conductors (A) and two different semiconductors (B and C).
At the A-B joint the moving electrons are slowed down and so give off energy which causes this point to heat up. At the B-A joint the moving electrons accelerate, returning to their original speed and so absorb energy which causes this point to cool down.
At the A-C joint the electrons continue to accelerate further thus absorbing more energy which causes this joint to cool down. At the C-A joint the electrons are slowed down again and so give off energy.
This causes this point to heat up, in the same way as at the A-B joint.