Thermoelectric cooling
Thermoelectric cooling uses the Peltier effect to create a heat flux at the junction of two different types of materials.
The primary advantages of a Peltier cooler compared to a vapor-compression refrigerator are its lack of moving parts or circulating liquid, very long life, invulnerability to leaks, small size, and flexible shape.
Its main disadvantages are high cost for a given cooling capacity and poor power efficiency (a low coefficient of performance or COP).
When operated as a generator, heating one side to a higher temperature that then other results in a voltage across the device (the Seebeck effect).
However, a well-designed Peltier cooler will be a mediocre thermoelectric generator and vice versa, because of different design and packaging requirements.
In special applications, multiple coolers can be cascaded or staged together for lower temperature, but overall efficiency (COP) drops significantly.
The maximum COP of any refrigeration cycle is ultimately limited by the different in temperature between the hot and cold side.
Improvements in reduced thermal transport with increased electrical conductivity are an active area of material science research.
There are many factors motivating further research on TEC including lower carbon emissions and ease of manufacturing.
Current technologies show the mean time between failures (MTBF) to exceed 100,000 hours at ambient temperatures.
These factors make them a common choice in scientific and engineering applications with demanding requirements where cost and absolute energy efficiency are not primary concerns.
Prior to their phaseout some early refrigerants, such as chlorofluorocarbons (CFCs), contributed significantly to ozone depletion.
Many refrigerants used today also have significant environmental impact with global warming potential[12] or carry other safety risks with them.
The result is that the heat effectively moved drops as the temperature difference grows, and the module becomes less efficient.
A single-stage thermoelectric cooler will typically produce a maximal temperature difference of 70 °C between its hot and cold sides.
Thermoelectric coolers are used for applications that require heat removal ranging from milliwatts to several thousand watts.
For example, they are used in camping, portable coolers, cooling electronic components, mattress pad sleeping systems and small instruments.
[16][17] Thermoelectric coolers can be used to cool computer components to keep temperatures within design limits or to maintain stable functioning when overclocking.
Some of the applications include laser equipment, thermoelectric air conditioners or coolers, industrial electronics and telecommunications,[20] automotive, mini refrigerators or incubators, military cabinets, IT enclosures, and more.
They are a common component in thermal cyclers, used for the synthesis of DNA by polymerase chain reaction (PCR), a common molecular biological technique, which requires the rapid heating and cooling of the reaction mixture for denaturation, primer annealing, and enzymatic synthesis cycles.
Photon detectors such as CCDs in astronomical telescopes, spectrometers, or very high-end digital cameras are often cooled by Peltier elements that may be arranged in a multi-stage,[22] cascade refrigeration configuration.This reduces dark counts due to thermal noise.
A dark count occurs when a pixel registers an electron caused by thermal fluctuation rather than a photon.
[citation needed] They are also used in energy-dispersive spectrometers to cool the sensor crystals, eliminating the necessity of large liquid nitrogen dewars.
Around 1955, RCA Laboratories built a refrigerator and a small room that was air conditioned using the Peltier effect.
