Thermoelectric Devices and the Peltier Effect

Thermoelectric devices convert directly between heat and electricity using junctions of dissimilar conductors, usually doped semiconductors. They rely on three related phenomena. The Seebeck effect produces a voltage from a temperature difference and underlies thermocouples and thermoelectric generators. The Peltier effect, the reverse process, causes heat to be absorbed at one junction and released at another when an electric current flows. The Thomson effect describes heating or cooling along a single conductor that carries current while a temperature gradient exists across it.

A Peltier cooler, also called a thermoelectric cooler, is built from many small pairs of n-type and p-type semiconductor pellets connected electrically in series and thermally in parallel between two ceramic plates. When current passes through, one plate becomes cold and the other warm, so the module pumps heat from the cold side to the hot side. Reversing the current swaps which side is cold. The material most often used is bismuth telluride, chosen for its favourable thermoelectric properties near room temperature.

Because they contain no moving parts, refrigerants or compressors, Peltier modules are compact, silent, reliable and easy to control precisely. They are used to cool electronic components, laser diodes, camera sensors and small portable coolers, and to stabilise temperatures in instruments. Their main limitation is modest efficiency, so they suit small heat loads rather than large-scale refrigeration. The same physics run in reverse lets thermoelectric generators turn waste heat or temperature differences into electric power.

Frequently asked questions

What is the Peltier effect?

It is the absorption or release of heat at a junction of two different conductors when an electric current passes through it. Reversing the current direction reverses which junction heats and which cools.

What are Peltier coolers used for?

They cool electronics, laser diodes, image sensors and small portable refrigerators, and they hold instruments at a stable temperature. They suit small heat loads where silence and no moving parts matter.

How is a thermoelectric module constructed?

It uses many n-type and p-type semiconductor pellets, often bismuth telluride, wired electrically in series and sandwiched thermally in parallel between two ceramic plates.