Previous Work

The thermoelectric effect was discovered by Thomas J Seebeck in 1821. He discovered that when heated different metals, as the temperature get hotter a small voltage will increase. By bonding the metals like iron with constants, for example, and then heating the bonded junction area, a small voltage is generated.

This bonded junction called a thermocouple is widely used as a control device in applications and equipment where heat in used. For example, natural gas devices including furnaces, hot water heaters, gas fireplace inserts and outdoor propane barbeque grills use this thermocouple process to verify the pilot flame is burning prior to allowing the main gas valve to open.  The newer discoveries with the p-n junction are leading to new technologies in P-N thermoelectric usage.

Both N-type and P-type Bismuth Telluride thermoelectric materials are used in a thermoelectric cooler. This arrangement causes heat to move through the cooler in one direction only while the electrical current moves back and forth alternately between the top and bottom substrates through each N and P element. N-type material is doped so that it will have an excess of electrons (more electrons than needed to complete a perfect molecular lattice structure) and P-type material is doped so that it will have a deficiency of electrons (fewer electrons than are necessary to complete a perfect lattice structure).

The extra electrons in the N material and the "holes" resulting from the deficiency of electrons in the P material are the carriers which move the heat energy through the thermoelectric material. Most thermoelectric cooling modules are fabricated with an equal number of N-type and P-type elements where one N and P element pair form a thermoelectric "couple." For example, the module illustrated above has two pairs of N and P elements and is termed a "two-couple module". Cooling capacity (heat actively pumped through the thermoelectric module) is proportional to the magnitude of the applied DC electric current and the thermal conditions on each side of the module. By varying the input current from zero to maximum, it is possible to regulate the heat flow and control the surface temperature