How do Peltier junctions work physically?

[PRodQuanta]

What's the physics behind a Peltier (sp?) Junction. I know what it does, but I'm not quite confident how it works.

Paden Roder

 

[Mk]

A Peltier cooler can transform electrical energy into that of thermal energy. The Peltier Effect is explained through electron motion. As current's applied to a junction, electrons increase or decrease their velocity based on the contact potential difference of the material they are traveling though. If the electrons speed up in the material, kinetic energy increases and this energy is converted to heat. For the slowdown of electrons, the opposite occurs.

 

[Gonzolo]

Another way to look at it is by assimilating the free electron gas in a metal to a regular gas.

Imagine a metal rod. By applying a voltage through it, electrons tend to group at the positive end. Electron density is thus a bit higher there. But the hotter electrons tend to stay on the end that is less dense because there is more room to move around. In this way, applying a voltage through the rod tends to separate the colder denser electrons, from the hotter, more wigly ones.

With junctions, delta T are added, much like delta V are in the case of batteries in series.