Pulsed cooling of inhomogeneous thermoelectric materials

It has been proven that the maximum cooling temperature of a thermoelectric material can be increased by using either pulsed operation or graded Seebeck profiles. In this paper, we show that the maximum cooling temperature can be further increased by the pulsed operation of optimal inhomogeneous thermoelectric materials. A random sampling method is used to obtain the optimal electrical conductivity profile of inhomogeneous materials, which can achieve a much higher cooling temperature than the best uniform materials under the steady-state condition. Numerical simulations of pulsed operation are then carried out in the time domain. In the limit of low thermoelectric figure-of-merit ZT, the finite-difference time-domain simulations are verified by an analytical solution for homogeneous material. This numerical method is applied to high ZT BiTe materials and simulations show that the effective figure-of-merit can be improved by 153% when both optimal graded electrical conductivity profiles and pulsed operation are used.