Compatibility factor for the power output of a thermogenerator



The compatibility approach introduced by Snyder and Ursell enables the description of both thermoelectric generator (TEG) and Peltier cooler (TEC) within the framework of a unified 1D model. Both TEG's efficiency η and TEC's coefficient of performance (C.O.P.) can be formulated in terms of the reduced current density u, which has been introduced as a new, intensive state variable of a thermoelectric system. For η and C.O.P., integral expressions are formed from additive contributions of all length segments of a thermoelectric ele-ment, enabling exact calculation of these quantities even for arbitrarily graded elements. Maximization of these global performance parameters can thus be deduced to local maximization. Here the maximum power from a TEG with fixed length but variable heat supply is considered, which leads to the new concept of power-related compatibility and to the introduction of a new, different compatibility factor. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)