Daily Archives: November 28, 2023

All about Thermoelectrics

TECs or Thermoelectric coolers or Peltier coolers are typically made from semiconductor materials exhibiting good electrical conductivity and thermal insulation. One such material is Bismuth Telluride. It offers the best performance of the above properties at room temperature environments. The development of ceramic-based substrates along with advanced semiconductor processing in the 1960s made thermoelectric devices available in commercial quantities.

TECs are solid-state devices that pump heat from a hot region to a colder region. For this to function properly, a heat transfer mechanism is necessary, a sort of heat exchanger that can absorb and dissipate the heat. TECs typically require DC voltages to operate. When power is applied, current flows through the cooler, carrying electrons from one side of the ceramic to the other. This results in one side of the substrate cooling down, while the other remains hot.

With a standard single-stage TEC, it is possible to achieve a temperature differential of nearly 70 °C at room temperature. That means the temperature difference between the two sides of the TEC can reach a maximum of 70 °C. With more advanced materials, TECs can reach temperature differentials of 74 °C.

Compared to alternate cooling technologies, TECs offer several advantages. One of them is their compact form factor, making them ideal for applications involving low heat loads. As there are no moving parts, TECs operate for extended periods with almost no maintenance necessary.

While cooling with thermoelectric coolers, it is possible to reach temperatures well below the freezing point of water. For instance, with multistage coolers, it is possible to reach temperatures below -90 °C. One major advantage of TECs is their ability to reverse their polarity by reversing the direction of current flow. This property is very useful in enabling thermal cycling, resulting in precise control of temperature, up to ±0.01 °C, maintained under steady-state conditions.

TECs are very efficient for heating purposes as well. In fact, they are more effective compared to conventional resistive heaters. This is because the heat generated by TECs is from the input power in addition to the heat it pumps in from the cold side. As TECs do not emit any HCFCs, they are environmentally friendly.

Depending on their rated capacity, the footprint of a typical TEC can range from 2 x 2 mm to up to 62 x 62 mm. This makes thermoelectric coolers ideal for operating in tight geometric spaces such as in telecom, industrial, analytical, and medical applications. Compared to conventional technologies such as compressor-based systems, TECs are miniscule.

Applications that handle low heat loads, less than 400 W, and those requiring cooling below ambient temperatures are typical applications benefitting from TECs. Where the control temperature is near ambient, passive heat exchanger solutions utilizing a heat sink and a fan may be adequate. Design engineers typically use TECs when their design criteria include such factors as high reliability, precise temperature control, compact form factor, minimal global warming potentials, and low weight requirements. TECs are ideal for various medical, telecom, analytical, and industrial applications that require active cooling.