title: Relationship between thermoelectric figure of merit and energy conversion efficiency.
abstract: The formula for maximum efficiency (ηmax) of heat conversion into electricity by a thermoelectric device in terms of the dimensionless figure of merit (ZT) has been widely used to assess the desirability of thermoelectric materials for devices. Unfortunately, the ηmax values vary greatly depending on how the average ZT values are used, raising questions about the applicability of ZT in the case of a large temperature difference between the hot and cold sides due to the neglect of the temperature dependences of the material properties that affect ZT. To avoid the complex numerical simulation that gives accurate efficiency, we have defined an engineering dimensionless figure of merit (ZT)eng and an engineering power factor (PF)eng as functions of the temperature difference between the cold and hot sides to predict reliably and accurately the practical conversion efficiency and output power, respectively, overcoming the reporting of unrealistic efficiency using average ZT values.
authors.affiliation: Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5002;
authors.forename: Hee Seok
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5002;
authors.forename: Weishu
authors.initials: W
authors.lastname: Liu
authors.affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; gchen2@mit.edu cwchu@uh.edu zren@uh.edu.
authors.forename: Gang
authors.initials: G
authors.lastname: Chen
authors.affiliation: Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5002; Lawrence Berkeley National Laboratory, Berkeley, CA 94720 gchen2@mit.edu cwchu@uh.edu zren@uh.edu.
authors.forename: Ching-Wu
authors.initials: CW
authors.lastname: Chu
authors.affiliation: Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5002; gchen2@mit.edu cwchu@uh.edu zren@uh.edu.
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Ren
keywords: conversion efficiency; cumulative temperature dependence; engineering figure of merit; engineering power factor; thermoelectrics