Maximum temperature difference in a single-stage thermoelectric device through distributed transport properties

Abstract

Maximum temperature difference (DT) for a standard thermoelectric (TE) module operating in cooling mode is 73 K (based on a hot-side temperature of 300 K) [1]. That value can be increased to 107 K for a two-stage cascaded device and up to 130 K for a four-stage cascaded device. The following paper presents findings determined through numerical analysis that confirm a single-stage device capable of achieving a maximum DT exceeding 130 K. This is accomplished principally by using distributed transport properties (DTP) with variable area, but also through the combination of alternative thermoelectric materials, including CsBi4Te6 (p-type) and magnetically-enhanced Bi0.88Sb0.12 (n-type).This numerical analysis builds on previously defined theory and analytical work by Bell [2]. Analysis includes the study of devices operating in maximum coefficient of performance (COP) and maximum heat pumping (Qc) modes, in addition to maximum DT mode. The study also shows how devices made with DTP excel over standard devices when operated in off-nominal conditions. Performance is determined using real temperature-dependent TE transport properties. Validation studies confirm performance against analytical results using ideal material properties where figure of merit (ZT) is kept constant and independent of temperature.