Thermoelectric cooling uses the Peltier effect to create a
heatIn physics and thermodynamics, heat is the process of energy transfer from one body or system due to thermal contact, which in turn is defined as an energy transfer to a body in any other way than due to work performed on the body....
flux between the junction of two different types of materials. A
PeltierPeltier is a French surname and may refer to:* Jean Charles Athanase Peltier , French physicist, documented the Peltier effect* Lee Peltier , English football player...
cooler, heater, or thermoelectric heat pump is a solid-state active
heat pumpA heat pump is a machine or device that moves heat from one location to another location using mechanical work. Most heat pump technology moves heat from a low temperature heat source to a higher temperature heat sink...
which transfers heat from one side of the device to the other side against the temperature gradient (from cold to hot), with consumption of electrical energy. Such an instrument is also called a Peltier device, Peltier
diodeIn electronics a diode is a two-terminal electronic component which conducts electric current asymmetrically or unidirectionally; that is, it conducts current more easily in one direction than in the opposite direction. The term usually refers to a semiconductor diode, the most common type today,...
, cooling diode, Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC).
http://www.redfishphotonics.com/thermoelectric_coolers.htm Because heating can be achieved more easily and economically by many other methods, Peltier devices are mostly used for cooling.
Thermoelectric cooling uses the Peltier effect to create a
heatIn physics and thermodynamics, heat is the process of energy transfer from one body or system due to thermal contact, which in turn is defined as an energy transfer to a body in any other way than due to work performed on the body....
flux between the junction of two different types of materials. A
PeltierPeltier is a French surname and may refer to:* Jean Charles Athanase Peltier , French physicist, documented the Peltier effect* Lee Peltier , English football player...
cooler, heater, or thermoelectric heat pump is a solid-state active
heat pumpA heat pump is a machine or device that moves heat from one location to another location using mechanical work. Most heat pump technology moves heat from a low temperature heat source to a higher temperature heat sink...
which transfers heat from one side of the device to the other side against the temperature gradient (from cold to hot), with consumption of electrical energy. Such an instrument is also called a Peltier device, Peltier
diodeIn electronics a diode is a two-terminal electronic component which conducts electric current asymmetrically or unidirectionally; that is, it conducts current more easily in one direction than in the opposite direction. The term usually refers to a semiconductor diode, the most common type today,...
, cooling diode, Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC).
http://www.redfishphotonics.com/thermoelectric_coolers.htm Because heating can be achieved more easily and economically by many other methods, Peltier devices are mostly used for cooling. However, when a single device is to be used for both heating and cooling, a Peltier device may be desirable. Simply connecting it to a DC voltage will cause one side to cool, while the other side warms. The effectiveness of the pump at moving the heat away from the cold side is dependent upon the amount of current provided and how well the heat can be removed from the hot side.
Peltier devices can also be used to generate electricity (
thermogeneratorThermogenerators are devices which convert heat directly into electrical energy. For the most part, this term is synonymous with "thermoelectric generator" and rarely used in English. Essentially they work on the principle of the Seebeck effect, with typical efficiencies of around 5-10%...
) if a temperature difference is maintained between the two sides.
Performance
Thermoelectric junctions are generally only around 5–10% as efficient as the ideal
refrigeratorA refrigerator is a cooling appliance comprising a thermally insulated compartment and a heat pump—chemical or mechanical means—to transfer heat from it to the external environment, cooling the contents to a temperature below ambient. Refrigerators are extensively used to store foods which spoil...
(
Carnot cycleEvery thermodynamic system exists in a particular state. When a system is taken through a series of different states and finally returned to its initial state, a thermodynamic cycle is said to have occurred. In the process of going through this cycle, the system may perform work on its...
), compared with 40–60% achieved by conventional compression cycle systems (reverse
RankineThe Rankine cycle is a thermodynamic cycle which converts heat into work. The heat is supplied externally to a closed loop, which usually uses water as the working fluid. This cycle generates about 80% of all electric power used throughout the world, including virtually all solar thermal, biomass,...
systems like a compressor). Due to the relatively low efficiency, thermoelectric cooling is generally only used in environments where the solid state nature (no moving parts, maintenance-free) outweighs pure efficiency.
Peltier (thermoelectric) cooler performance is a function of ambient temperature, hot and cold side heat exchanger (
heat sinkA heat sink is an environment or object that absorbs and dissipates heat from another object using thermal contact...
) performance, thermal load, Peltier module (thermopile) geometry, and Peltier electrical parameters.
However recent developments prove that series Peltier effect modules could soon surpass internal combustion engines both in efficiency and power density for fuel based power generation .
Uses
Peltier devices are commonly used in
campingCamping is an outdoor recreational activity.The participants, known as campers, leave urban areas, their home region, or civilization and enjoy nature while spending one or several nights, usually at a campsite, which may have cabins...
and portable coolers and for cooling electronic components and small instruments. Some electronic equipment intended for military use in the field is thermoelectrically cooled. The cooling effect of Peltier heat pumps can also be used to extract water from the air in
dehumidifierA dehumidifier is mostly a household appliance that reduces the level of humidity in the air, usually for health reasons, as humid air can cause mold and mildew to grow inside homes, which has various health risks. Relative humidity is preferably 30 to 50%...
s.
Peltier elements 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.
The effect is used in
satelliteIn the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
s and
spacecraftA spacecraft is a craft or machine designed for spaceflight. On a sub-orbital spaceflight, a spacecraft enters space then returns to the Earth. For an orbital spaceflight, a spacecraft enters a closed orbit around the planetary body. Spacecraft used for human spaceflight carry people on board as...
to counter the effect of direct
sunlightSunlight, in the broad sense, is the total spectrum of the electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon. Near the poles in summer, the days are longer and the...
on one side of a craft by dissipating the heat over the cold shaded side, whereupon the heat is dissipated by
thermal radiationThermal radiation is electromagnetic radiation emitted from the surface of an object which is due to the object's temperature. An example of thermal radiation is the infrared radiation emitted by a common household radiator or electric heater. A person near a raging bonfire will feel the radiated...
into space.
Photon detectors such as
CCDA charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
s in astronomical telescopes or very high-end
digital cameraA digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor....
s are often cooled down with Peltier elements. This reduces dark counts due to thermal noise. (A dark count is the event that a pixel gives a signal although it has not received a photon but rather mistook a thermal fluctuation for one. On digital photos taken at low light these occur as speckles (or "pixel noise").
Thermoelectric coolers can be used to
cool computer componentsComputer cooling is the process of removing heat from computer components. Because a computer system's components produce large amounts of heat during operation, this heat must be dissipated in order to keep these components within their safe operating temperatures.In addition to maintaining...
to keep temperatures within design limits without the noise of a fan, or to maintain stable functioning when
overclockingOverclocking is the process of running a computer component at a higher clock rate than it was designed for or was specified by the manufacturer, usually practiced by enthusiasts seeking an increase in the performance of their computers...
. A Peltier cooler with a
heat sinkA heat sink is an environment or object that absorbs and dissipates heat from another object using thermal contact...
or waterblock can cool a chip to well below ambient temperature.
Peltier devices are used in USB drink coolers/chillers, one of the latest addition to USB gadgets/toys. These devices are powered directly from the USB port and are said to keep drinks chilled, some even can keep drinks warm. The effectiveness of these devices, however, is questionable. The available power from a USB socket is very limited, so cooling or heating will be minimal.
Underlying principles
Thermoelectric coolers rely on the
thermoelectric effectThe thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely when a voltage is applied to it, it creates a temperature difference...
. When a current is run through an appropriately-configured thermoelectric device, heat is transported from one side of the device to the other.
See also
- Bismuth telluride
Bismuth telluride is a gray powder that is a compound of bismuth and tellurium also known as bismuth telluride. It is a semiconductor which is an efficient thermoelectric material for refrigeration or portable power generation.-Thermoelectric properties:Bismuth telluride is a narrow gap layered...
, an efficient thermoelectric material
- Freezer
- H2Ceramic cooling
H2Ceramic cooling is a computer cooling product offered as an option in Dell's XPS gaming systems, advertised specifically as facilitating CPU overclocking...
- a hybrid combination of thermoelectric and liquid cooling
- Heat transfer
Heat transfer is the transition of thermal energy from a hotter object to a cooler object...
- Joule's law
Joule's laws are a pair of laws concerning the heat produced by a current and the energy dependence of an ideal gas to that of pressure, volume, and temperature, respectively....
- Pyroelectric effect - the creation of an electric field in a crystal after uniform heating
- Thermionic emission
Thermionic emission is the heat-induced flow of charge carriers from a surface or over a potential-energy barrier. This occurs because the thermal energy given to the carrier overcomes the forces restraining it. The charge carriers can be electrons or ions, and in older literature are sometimes...
- Thermoelectrics
- Thermoelectricity
Thermoelectricity refers to a class of phenomena in which a temperature difference creates an electric potential or an electric potential creates a temperature difference. In modern technical usage, the term almost always refers collectively to the Seebeck effect, Peltier effect, and the Thomson...
- Thermopower
The thermopower, or thermoelectric power of a material is a measure of the magnitude of an induced thermoelectric voltage in response to a temperature difference across that material...
- Thermotunnel cooling
Thermotunnel cooling is similar to thermionic emission cooling in that fast moving electrons carry heat across a gap but cannot return due to a voltage difference...
- Thermoacoustics - competitor technology to thermoelectric cooling