TEC, Thermo-Electric Cooler, can generate both heating and cooling power by input electric DC current. When the current flows in one direction, one of the thermo-electric cooler plates generates heat while the other generates cold. As the current reverses the direction, the TEC plates will reverse their relative relationship in temperature.
TEC modules have many applications. One of them is to keep diode laser chips working at a constant temperature, thus, the lasers will output a laser beam with a stable wavelength, constant power, and low optical noise. When designing a TEC based temperature regulation system, choosing the right TEC is critical.
General suggestions for choosing suitable TEC modules:
1. TECs have limited life time. Their health strength can be measured by the change of their AC resistance. When a TEC gets "old" or worn out, the AC resistance (ACR) will increase. To build a reliable system, only good "healthy" TECs should be used. Measuring the initial ACR is critical; make sure that the initial ACRs are within the specification. The ACR must be measured by special meters. 2. Try your best to minimize the thermal resistance between the TEC module plates and the thermal heat-sink on the hot side and the thermal load on the cold side.
3. The best way to connect the TEC modules plates to the heat-sink or the thermal load is by metalizing the TEC modules plates and soldering the metalized surface directly onto the heat-sink surface and/or the thermal load surface.
4. Try your best to design the system with smaller maximum temperature difference between the 2 plates (hot side and the cold side) of the TEC modules, so that the thermal efficiency of the system will be high. It would be the best not to require the maximum temperature difference be > 30 Celsius degree.
5. When the required maximum temperature difference is small, such as < 30 Celsius degree, use large TEC modules to drive small thermal load which will result in high thermal efficiency.
6. The thermal efficiency of the TEC modules is usually measured by COP: Coefficient of Performance. It is defined as the ratio: (Thermal output power)/(Electrical input power). A well designed system can achieve a COP to be > 2.