Optimal working conditions for thermoelectric generators with realistic thermal coupling

¹ Institut d'Electronique Fondamentale, Université Paris-Sud CNRS - F-91405 Orsay, France, EU
² CNRT Matériaux UMS CNRS 3318 - 6 Boulevard Maréchal Juin, F-14050 Caen Cedex, France, EU
³ Renault SAS, SAS FR TCR AVA 058 - 1 avenue du Golf, F-78288 Guyancourt, France, EU
⁴ Laboratoire CRISMAT, UMR 6508 CNRS, ENSICAEN et Université de Caen Basse Normandie 6 Boulevard Maréchal Juin, F-14050 Caen, France, EU

^a yann.apertet@u-psud.fr

Received: 26 August 2011
Accepted: 28 November 2011

Abstract

We study how maximum output power can be obtained from a thermoelectric generator (TEG) with non-ideal heat exchangers. We demonstrate with an analytic approach based on a force-flux formalism that the sole improvement of the intrinsic characteristics of thermoelectric modules including the enhancement of the figure of merit is of limited interest: the constraints imposed by the working conditions of the TEG must be considered on the same footing. Introducing an effective thermal conductance we derive the conditions which permit maximization of both efficiency and power production of the TEG dissipatively coupled to heat reservoirs. Thermal impedance matching must be accounted for as well as electrical impedance matching in order to maximize the output power. Our calculations also show that the thermal impedance does not only depend on the thermal conductivity at zero electrical current: it also depends on the TEG figure of merit. Our analysis thus yields both electrical and thermal conditions permitting optimal use of a thermoelectric generator.