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Principle of Thermoelectric Operation
Thermoelectric coolers (TECs), also known as Peltier coolers, are solid-state heat pumps that utilize the Peltier effect to move heat. Passing a current through a TEC transfers heat from one side to the other, typically producing a heat differential of around 40°C—or as much as 70°C in high-end devices—that can be used to transfer heat from one place to another.
The principle of thermoelectric cooling dates back to the discovery of the Peltier Effect by Jean Peltier in 1834. All electric current is accompanied by heat current (Joule heating). What Peltier observed was that when an electric current passed across the junction of two dissimilar conductors (a thermocouple) there was a heating effect that could not be explained by Joule heating alone. In fact, depending on the direction of the current, the overall effect could be either heating or cooling. This effect can be harnessed to transfer heat, creating a heater or a cooler.
When two conductors are placed in electric contact, electrons flow out of the one in which the electrons are less bound, into the one where the electrons are more bound. Current passing across the junction results in either a forward or reverse bias, resulting in a temperature gradient; Cold vs. Heat! If the temperature of the hotter junction (heat sink) is kept low by removing the generated heat, the temperature of the cold plate can be cooled by tens of degrees.
In practice, many TEC pairs (or couples) are connected side-by-side, and sandwiched between two ceramic plates, in a single TEC.
The Benefits of Thermoelectric Chillers as Compared to Compressor Chillers
Thermoelectric recirculating chillers (also called Peltier chillers) have many benefits and advantages when compared to compressor-based chillers. Thermoelectric chillers utilize multiple arrays of thermoelectric chips (TECs) are coupled with heat sinks, fans and liquid heat exchangers to provide extremely accurate thermal control of the outgoing fluid. As TECs have the ability to heat as well as cool, thermoelectric chillers provide extremely fast and accurate temperature control and stability and can achieve temperature stability near 0.01°C with a stable heat load. Compressor-based chillers utilize compressors with refrigerant, condensers and evaporators to provide bulk cooling and typically resistive heaters in order to counteract the on-off cooling of compressors.
The solid-state nature of the TEC (no moving parts) leads to a very high reliability for the entire thermoelectric chiller system. There are no consumables or refrigerant required. Additionally, there is no compressor so the vibration is minimal.
Thermoelectric Benefits
Accurate, responsive and consistent temperature control
Limited maintenance due to lack of moving parts
No harmful CFCs due to lack of refrigerants
Iceless cooling
Lightweight and compact
