Method and Apparatus for Determining Operational Parameters of Thermoelectric Modules

Rafał Zybała,Mirosław J Kruszewski,Kamil Kaszyca,Ł Ciupiński ,M Schmidt ,K Pietrzak

doi:10.1007/s11664-016-4712-1

Abstract

The main aim of this work was to construct and test an apparatus for characterization of high temperature thermoelectric modules to be used in thermoelectric generator (TEGs) applications. The idea of this apparatus is based on very precise measurements of heat fluxes passing through the thermoelectric (TE) module, at both its hot and cold sides. The electrical properties of the module, under different temperature and load conditions, were used to estimate efficiency of energy conversion based on electrical and thermal energy conservation analysis. The temperature of the cold side, Tc, was stabilized by a precise circulating thermostat (≤0.1°C) in a temperature range from 5°C to 90°C. The amount of heat absorbed by a coolant flowing through the heat sink was measured by the calibrated and certified heat flow meter with an accuracy better than 1%. The temperature of the hot side, Th, was forced to assumed temperature (Tmax = 450°C) by an electric heater with known power (Ph = 0–600 W) with ample thermal insulation. The electrical power was used in calculations. The TE module, heaters and cooling plate were placed in an adiabatic vacuum chamber. The load characteristics of the module were evaluated using an electronically controlled current source as a load. The apparatus may be used to determine the essential parameters of TE modules (open circuit voltage, Uoc, short circuit current, Isc, internal electrical resistance, Rint, thermal resistance, Rth, power density, and efficiency, η, as a function of Tc and Th). Several commercially available TE modules based on Bi2Te3 and Sb2Te3 alloys were tested. The measurements confirmed that the constructed apparatus was highly accurate, stable and yielded reproducible results; therefore, it is a reliable tool for the development of thermoelectric generators.

Highlights

Direct energy conversion from heat into electricity takes place in thermoelectric generators (TEGs) made from coupled n- and p-type carrier thermoelectric material by way of the Seebeck (Received February 15, 2016; accepted May 27, 2016; published online June 23, 2016)effect
The measurements confirmed that the constructed apparatus was highly accurate, stable and yielded reproducible results; it is a reliable tool for the development of thermoelectric generators
The heat losses in the system were evaluated by comparing the heat fluxes and the electrical power

Summary

Introduction

Direct energy conversion from heat into electricity takes place in thermoelectric generators (TEGs) made from coupled n- and p-type carrier thermoelectric material (unicouple) by way of the Seebeck (Received February 15, 2016; accepted May 27, 2016; published online June 23, 2016)effect. The energy conversion efficiency is closely related to the Carnot cycle efficiency and material properties expressed by thermoelectric figure-ofmerit (ZT).[1] Because the voltage of one unicouple is very small, TEGs have to be constructed of a number of such pairs connected electrically in series and thermally in parallel.[2] As a result, TEG efficiency depends on many factors such as design issues, including dimensions of the modules and Zybała, Schmidt, Kaszyca, Ciupinski, Kruszewski, and Pietrzak number of the unicouples, material parameters (ZT, electrical and thermal contact resistance, properties of insulation plates), and operating conditions (temperature range, load parameters). A number of parameters can limit the TEG performance, and the best way to compare thermoelectric modules is based on measurement of their efficiency of energy conversion. Recently an interest in the real TEG operating parameters is stimulated, because of possibility of a wide range of home and industrial applications.[1,2,3,4] The performance evaluation of the modules, and a precise characterisation of their operational parameters became a necessary requirement.[2,3]

Objectives

Methods

Findings

Conclusion