LabTips: Peltier vs. Compressor: A Chilling Battle

 <span>LabTips:</span> Peltier vs. Compressor: A Chilling Battle

“Peltier technology” was discovered by Athanase Peltier while observing the temperature difference between one side of a device and the other, depending on the direction of current. Only from recent advances in semiconductor materials has the full utilization of this technology been realized. The strength of Peltier technology lies in the scalability of its cooling elements, their location-independence, precision control, as well as vibration-free and noise-free operation.

KT Series Refrigerated Incubator by BINDER with Peltier Technology

Compressor technology utilizes a chemical-based pump to transfer heat from the inside of an insulated compartment to the outside, thereby maintaining an interior temperature cooler than the exterior ambient temperature. A compressor system operates by using a pump to move a cooled chemical gas through a pressurized system. The gas cools the interior compartment, is compressed and heats up as it exits, releasing the heat on the exterior of the unit following the second law of thermodynamics These units are commonly used in refrigerators and freezers for food storage and have higher energy costs and heat dissipation.

Compressor systems use flammable chemical materials that are not environmentally friendly or economical to run. Conventional compressor system operation also depends on the unit positioning. When tilted or rotated, these systems can fail. In contrast, Peltier modules handle tilting and rotation without interruption.

KT Series Refrigerated Incubator by BINDER with Peltier Technology; door open

In general, Peltier elements are very reliable and durable and, because they contain no moving parts, they are quiet and vibration-free. They can be small and lightweight, even when combining several modules into a single unit. They contain no flammable refrigerants and without the need for a cooling system, they are economical to manufacture. They require little or no maintenance and are easy to replace in case of failure. State-of-the-art control technology allows more accurate measurement of the cooling effect than with conventional compressors. The systems can also be reversed from cooling to heating by changing the polarity of the elements.

Peltier elements absorb heat on one side and dissipate it on the other, making the current act as a “refrigerant” in the cooling cycle. The electrical energy (current) is converted into heat energy (Joules) with the Peltier element acting as a resistor (Ohm). This heat energy generated is dissipated into the exterior, which creates a net cooling effect inside the unit.

KB Series Refrigerated Incubator from BINDER Inc

Peltier modules are only 3 to 5 mm (0.1 to 0.2 in) thick with the hot and cold sides situated very closely together. The heat in the module is carried by large heat sinks with fans, delivering increased efficiency. If there is a greater temperature difference, the unit’s heat transfer capacity will decrease until coming to a complete standstill at approximately 70 K (-203 ºC) temperature difference (based on the present state of Peltier technology). Greater temperature differentials within one unit can only be achieved by complex, multistage elements. If a single unit is used to implement a high temperature difference, the system will fail.

Thermoelectric refrigeration technology is used wherever compressors are not suitable due to size, noise, energy efficiency, or precision cooling. Peltier-based systems are an excellent choice for food and beverage coolers and small dehumidifiers. Additionally, they are used for thermo cyclers, a device for multiplying DNA sequences. For a PCR (polymerase chain reaction), three different reaction temperatures are required in rapid succession. Because compressor systems cannot be scaled to accommodate this process, the Peltier modules are used to provide the precise temperature control needed for this technique. Miniature Peltier elements are also used in scintillators, where the noise of the photodiodes must be reduced by cooling and in computer chips for heat dissipation.

KB Series Refrigerated Incubator from BINDER Inc.

Peltier technology has only begun to be used more recently in refrigerated laboratory incubators. They are unable to provide consistently low temperatures (e.g., below 10 °C). However, for incubation at or around room temperature (15 – 30 °C) or for applications with heat input, these units can be operated economically. In such cases, poor energy efficiency is of little consequence as cooling runs at a low level without demanding maximum power. Average power consumption can fall below that of a conventional cooled incubator and the technical complexity of a compressor system with its disadvantages can be eliminated.

Peltier technology opens new opportunities for special applications, especially if the process does not require extensive temperature differential cooling or energy efficiency. Its scalability and location-independence enables the development of smaller and more portable units. Peltier modules make temperature control efficient at lower temperature gradients by fine metering of cooling capacity.

Conventional compressors with their high efficiency and greater power reserves still remain the norm for conventional refrigerators and freezers found in the home and in laboratories.

Author

Dr. Jens Thielmann is a biologist and Product Manager, Growth & Storage, at BINDER GmbH. He is responsible for the development of various incubators used in medicine, science and pharmaceutical research, incubation of bacteria or mammalian cell cultures, as well as ultra-low temperature freezers for long-term stable storage of sensitive samples.

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