19. What is the Peltier Effect?
Named after the man who discovered it, the Peltier effect is surprisingly simple. An electric current that flows between two semiconductors faces is being heated on one side, and the energy output from that side simultaneously cools the other side. The Peltier effect can be reversed; you can use the energy to either heat something or cool something. From this, thermoelectric coolers and heaters were born. In addition to the Seebeck effect and the Thompson effect, the Peltier effect completes the trinity of thermoelectric rules.
The Peltier Effect Equation
Many factors go into the equation for the Peltier effect, and determining specific coefficients. The simplest form of the Peltier effect can be represented by:
Here,is the Peltier coefficient of conductor A (B), and is the electric current (from A to B).
Different coefficients that could determine any changes to the equation would be Joule heating, and thermal gradient effects, such as the Seebeck and Thompson effects. However, the fundamental basis for the equation remains the same.
Peltier Effect Cooling
Most people may own a large refrigerator, one that can hold food, drinks, and freezer items. What they don’t realize is these large refrigerators are operating on a large amount of power. They also require maintenance or upgrades when you’ve had them for too long. However, coolers that use Peltier effect modules are more reliable and do not require any maintenance. These modules are solid-state devices and do not have any moving parts, therefore they are less likely to have anything go wrong than a normal refrigerator.
Here are some more examples of the many benefits of thermoelectric coolers that use the Peltier effect:
- No refrigerants, such as chlorofluorocarbon (CFC), make these devices more nvironmentally friendly and safer to be around
- Modules that are small and lightweight are easily adaptable to whatever room or device they are aiding
- With less moving parts, these devices provide a faster, more dynamic response than larger cooling generators
Peltier Effect Inefficiencies
While there are many benefits to using Peltier coolers, there are also some downsides. Peltier modules actually use more power than they put out, so they are more beneficial for smaller coolers. Smaller coolers may consume twice as much energy (in the form of electricity) than they actually transport (in the form of heat). In addition, condensation on the device is a major issue. Because these modules can be cooled below ambient temperature (safe room temperature is between 60 and 70 degrees), condensation may occur depending on current ambient temperature, surrounding humidity, and other factors. If you are operating a device that uses the Peltier effect, be sure to monitor for condensation, as water on electronics is a safety hazard.
Peltier Coolers in Consumer Products
The average person may not think that they come in contact with thermoelectric materials often, but they are more prevalent than one would think. Some common uses of Peltier coolers in consumer products are:
- Camping gear, such as a USB powered beverage cooler
- Heat pumps used to extract water in humidifiers
- Wine coolers
- Mini refrigerators
These affordable cooling options that utilize the Peltier effect can be found in cars, home, and college dorm rooms across the country.
Industrial Uses of Peltier Coolers
Aside from more common everyday uses, thermoelectric coolers have large roles in several different industries. Photon detectors such as CCDs in astronomical telescopes, spectrometers, or very high-end digital cameras are often cooled down with Peltier elements.
Smaller modules that operate medium to low heat applications can be used for temperature stabilization in fiber optics & Ink Jet printers. Because fiber optic applications are highly sensitive to temperature, Peltier coolers are used along with a thermistor in a feedback loop to maintain a constant temperature and thereby stabilize the wavelength of the device.
Similarly, Peltier coolers used in outer-space that must be kept at specific temperatures. The effect is used in satellites and spacecraft to counter the effect of direct sunlight on one side of a craft by dissipating the heat over the cold shaded side, whereupon the heat is dissipated by thermal radiation into space.
With the world of physics constantly changing and evolving, Jean Peltier was able to provide a solid foundation for thought leaders such as II-VI Marlow to build upon. The discovery of the Peltier effect has lead to several technological advances, such as single-stage and multi-stage coolers. II-VI Marlow’s advances with Peltier coolers have led to their uses in several different industries, such as wide range temperature calibration for thermal reference sources, imaging systems for space-based instruments, and temperature stabilization of bolometers and ferroelectric detectors.