Improved supercooling in transient thermoelectrics

We present calculations for the supercooling of a thermoelectric material during a transient current pulse. At room temperature, a standard steady-state cooler produces a maximum temperature drop of 82 K. During a current pulse, this value can be increase to about 108 K. While prior calculations focused on the optimization of the current pulse with respect to length and height, we investigate the influence of the pulse shape upon the cooling mechanism. Our results show that using a quadratic pulse form, the supercooling effect can be improved and a maximum temperature drop of 116 K can be achieved, exceeding all previously reported results by 8 K. The mechanism increases the ratio of ZT(eff)/ZT from the previous value of 1.76 to a maximum of 2.01. The optimized pulse shape requires less,energy and, therefore, prevents extensive heating of the material after the minimum temperature is reached, resulting in an increase of efficiency by approximately a factor of 2. (C) 2004 American Institute of Physics.