Thermoelectric coolers are solid-state heat pumps used in applications where temperature stabilization, temperature cycling, or cooling below ambient levels are required. Thermoelectric cooling is produced when direct current (DC) is applied across two dissimilar materials and causes a temperature differential. Because of their relatively low efficiency, thermoelectric coolers are used mainly in environments that require solid-state devices. Typically, a thermoelectric cooler is used for a job that would be impractical with a compressor-based system.
Most thermoelectric coolers use semiconductors, in part because these materials can be optimized for pumping heat, but also because the type of charge carrier employed can be controlled within a conductor. A typical thermoelectric cooler is manufactured using two thin ceramic wafers with a series of P and N doped bismuth-telluride semiconductor material placed between them. Ceramic material on both sides of the substrate adds rigidity and electrical insulation. Thermoelectric chillers consist of a series of thermoelectric modules placed between a conductive plate and a finned heat sink to dissipate the heat to the ambient air. A pump circulates the liquid from the thermoelectric chiller through the plate, where it is cooled to the desired temperature before absorbing heat from the object. Thermoelectric generators are thermoelectric coolers that convert part of the heat flowing from a hot body to a cold body into electricity. The portion of the thermal power that is turned into electrical power is referred to as efficiency. A thermoelectric generator produces DC voltage that is proportional to the temperature difference. When a thermoelectric generator is connected to a variable input DC/DC converter, stable voltage output can be achieved over a wide range of temperatures. Maximum power output is achieved when the external resistance is equal to the internal resistance.
Thermoelectric coolers and thermoelectric modules are used in many different products. Examples include charge coupled device (CCD) cameras, laser diodes, microprocessors, blood analyzers and portable picnic coolers. Thermoelectric cooling is also used to cool computer components. A thermoelectric generator is often used in power instruments on spacecraft, on glaciers, and in places away from inhabited areas. Thermoelectric coolers are also used in medical applications such as therapeutic hot/cold pads, surgical lasers, and recirculating baths.