Separated effect of 1D thermoelectric material gradients

Graded and segmented thermoelements have been considered for long, aiming at improving the performance of thermogenerators which are exposed to a large temperature difference. A precise numerical algorithm for performance estimation of thermogenerator (TEG) and Peltier cooler elements has been developed using MATHEMATICA. It is capable to calculate accurate profiles of temperature, potential, and energy flux along segmented and graded TE elements in a one-dimensional model. Application-relevant performance parameters like C.O.P., cooling power, temperature difference (of a TEC), efficiency, and output power (of a TEG) are deduced. Executing the calculation in a loop with variation of the current allows selecting optimum operation parameters. A fundamental parameter study to identify optimum combinations of gradients of the TE properties along a Peltier and TEG element, respectively, demonstrates the quantitative improvement of performance achievable by gradients. Related to the higher optimum current density, achievable effects are larger for Peltier coolers than for TEGs although the operating temperature difference was assumed much larger for TEGs. The strongest improvement for Peltier elements can be achieved at the maximum temperature difference if steep material gradients are selected. The attempt is made to discuss the results in terms of the compatibility approach