Small-signal model for frequency analysis of thermoelectric systems

TL;DR

This paper extends small-signal analysis from electrical engineering to thermoelectric systems, providing a physical basis for impedance spectroscopy interpretation and enabling in-situ device characterization.

Contribution

It introduces a generalized small-signal model for thermoelectric systems that accounts for finite thermal impedance, improving the understanding of their frequency response.

Findings

Derived a generalized expression for the characteristic angular frequency.

Highlighted the importance of thermal contact impedance in models.

Enables impedance spectroscopy beyond adiabatic boundary conditions.

Abstract

We show how small-signal analysis, a standard method in electrical engineering, may be applied to thermoelectric device performance measurement by extending a dc model to the dynamical regime. We thus provide a physical ground to \textit{ad-hoc} models used to interpret impedance spectroscopy of thermoelectric elements from an electrical circuit equivalent for thermoelectric systems in the frequency domain. We particularly stress the importance of the finite thermal impedance of the thermal contacts between the thermoelectric system and the thermal reservoirs in the derivation of such models. The expression for the characteristic angular frequency of the thermoelectric system we obtain is a generalization of the expressions derived in previous studies. In particular, it allows to envisage impedance spectroscopy measurements beyond the restrictive case of adiabatic boundary conditions often difficult to achieve experimentally, and hence \emph{in-situ} characterization of thermoelectric generators.