Supercooling of Peltier cooler using a current pulse

The operation of a Peltier cooler can be temporarily enhanced by utilizing the transient response of a current pulse. The performance of such a device, using (Bi,Sb) ₂Te ₃-based thermoelectric elements, was examined from -70 to 55°C. We establish both theoretically and experimentally the essential parameters that describe the pulse cooling effect, such as the minimum temperature achieved, maximum temperature overshoot, time to reach minimum temperature, time while cooled, and time between pulses. Using simple theoretical and semiempirical relationships the dependence of these parameters on the current pulse amplitude, temperature, thermoelectric element length, thermoelectric figure of merit and thermal diffusivity is established. At large pulse amplitudes the amount of pulse supercooling is proportional to the maximum steady-state difference in temperature. This proportionality factor is about half that expected theoretically. This suggests that the thermoelectric figure of merit is the key materials parameter for pulse cooling. For this cooler, the practical optimum pulse amplitude was found to be about three times the optimum steady-state current. A pulse cooler was integrated into a small commercial thermoelectric three-stage cooler and it provided several degrees of additional cooling for a period long enough to operate a laser sensor. The improvement due to pulse cooling is about the equivalent of two additional stages in a multistage thermoelectric cooler.