Thursday, 22 October 2015

[Purdue e-Pubs] A physics-based compact model for thermoelectric devices


A physics-based compact model for thermoelectric devices
Kyle Conrad, Purdue University; Mark S. Lundstrom, Purdue University (Advisor)

Abstract: Thermoelectric devices have a wide variety of potential applications including as coolers, temperature regulators, power generators, and energy harvesters. During the past decade or so, new thermoelectric materials have been an active area of research. As a result, several new high figure of merit (zT) materials have been identified, but practical devices using these new materials have not yet been reported. A physics-based compact model could be used to simulate a thermoelectric devices within a full system using SPICE-compatible circuit simulators. If such a model accepts measured or simulated material parameters, it would be useful in exploring the system level applications of new materials. In this thesis, the ground work for such a compact model is developed and tested. I begin with a discussion of thermoelectric transport theory within the Landauer formalism. The Landauer formalism is used as the basis of the tool LanTraP, which uses full band descriptions to calculate the distribution of modes and thermoelectric transport parameters, which can serve as the input to a compact model. Next, an equivalent circuit model is presented, explained, and tested using a simple Bi2Te 3 thermoelectric leg. The equivalent circuit is shown to perform well under a variety of DC, transient, and AC small signal operating conditions. With the equivalent circuit it is easy to determine the maximum cold side temperature drop, the maximum cold side heat absorbed, the temperature profile within the leg, the temperature response to a pulsed current, and impedance over a range of frequencies. Finally, Sentaurus®, a computer program that solves the thermoelectric transport equations numerically, is used to compare and benchmark some of the results of the equivalent circuit when considering Si as the thermoelectric material. The equivalent circuit and Sentaurus® simulations produce similar results in DC and transient cases, but in the AC small signal case the two simulations produce slight differences. The results of this work establishes a baseline compact model for thermoelectric devices whose accuracy and capabilities can be extended.

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