The Peltier Technology

What are the advantages of cooling with Peltier cooling components?
Which differences and similarities to conventional compressor systems exist?

Both cooling systems have a heat flow from a cold to a warm reservoir.

Schaubild

In the compressor system, the heat transfer is carried out by a cooling fluid which is compressed by the compressor and transported through the system.


In the Peltier cooler, the electric current corresponds to the coolant of the compressor and the direct current voltage source is equivalent to the compressor.


A variety of applications can only be solved with Peltier technology.

  • Control accuracy
    Peltier units can be controlled electronically. This results in control accuracies which cannot be achieved with compressor cooling.
  • Reversibility
    Peltier elements are easily reversible. Simply by reversing the polarity of the DC voltage, heat can be produced where it was cooling previously, and vice versa.
  • Robustness
    Peltier coolers can work in the most adverse environmental conditions. They are suited for working in high ambient temperatures or heavily polluted ambient air. Peltier coolers don’t even have problems with vibrations or strong accelerations!
  • Miniature cooling
    Peltier coolers can provide precisely defined small cooling capacities.

The history of thermoelectric effects

The thermoelectric effects were discovered in
the first half of the 19th century.

1822 Seebeck effect
It was Thomas Johan Seebeck, who observed the following phenomenon named after him in 1822: If a closed conductor loop is formed from two different metallic conductors, and a temperature difference prevails between the two contact points of the two materials, a current flows in the conductor loop.

Today’s thermocouples are demonstrative examples.

1834 Peltier effect
The opposite effect was discovered 1834 by Jean Charles Athanase Peltier: Under certain conditions, an electrical current ow causes a temperature difference between two metallic conductors.

Peltier effect: A temperature difference is generated by an electric current flow
Peltier effect: A temperature difference is generated by an electric current flow

In order to make the Peltier effect economically usable, two differing metals are no longer used for the construction of a Peltier element. In this case, the resulting temperature difference is below 1 K.

Nowadays one metal is replaced with an n-type semiconductor (the electric conduction is caused by the ow of negatively charged electrons) and the other with a p-type semiconductor (the electric conduction is caused by the ow of positively charged holes). A copper bridge connects the two semiconductor legs. If direct current is passed through the Peltier element in the direction indicated, the copper bridge, which connects the two elements, cools down. The two connecting bridges, also made of copper, heat up. A steady heat transfer takes place from the upper copper bridge to the lower copper bridges.

In order to obtain suitable Peltier blocks for technical application, the individual Peltier elements are joined in a meandering manner. The Peltier elements which are combined to form a Peltier block are electrically connected in series and thermally in parallel. The Peltier blocks then again can be switched electrically in series or parallel, in case large cooling surfaces are required.