Characterization of Thermoelectric Power Generation Modules Made from New Materials
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Characterization of Thermoelectric Power Generation Modules Made from New Materials Jarrod L. Short1, Jonathan D’Angelo1, Adam D. Downey1, Michael A. Pajor1 Ed Timm3, Harold Schock3, Mercouri G. Kanatzidis2, Timothy P. Hogan1 1 Electrical and Computer Engineering Department, Michigan State University 2 Chemistry Department, Michigan State University 3 Mechanical Engineering Department, Michigan State University East Lansing, MI 48824-1322
ABSTRACT Lead-Antimony-Silver-Tellurium (L-A-S-T) materials, synthesized at Michigan State University, show promising thermoelectric properties at high temperatures for use in power generation applications. Recent scaled-up quantities of L-A-S-T show a ZT=1.4 at 700 K approaching the figure of merit for samples made in small quantities [1]. These materials are of great interest for power generation applications with hot side temperatures in the range of 600800 K. Developing these materials into working devices requires minimization of the thermal and electrical parasitic contact resistances, so various fabrication methods are under investigation. To examine each method, a new measurement system has been developed to characterize these devices under various load and temperature gradients. An introduction to the system will be presented, as well as results for devices made of the L-A-S-T materials.
INTRODUCTION Thermoelectric generators convert energy from heat into electricity by existence of the Seebeck effect. An applied temperature gradient across the generator will force heat to flow from the hot to cold side by thermal conduction while some of this heat is converted to electricity. The generator efficiency, η, is determined by comparing the amount of electricity produced, Pout, to the total amount of heat induced, Qin. P η = out Qin To accurately determine the efficiency of a generator, the heat induced and electrical power produced must be carefully measured. Generator efficiencies are often calculated from the measured material properties [9]. This method indirectly yields generator efficiency through the figure of merit, requiring separate measurements of absolute Seebeck, electrical and thermal conductivities of which each are susceptible to a tolerance of errors. More direct measurements of the figure of merit have been demonstrated and are useful to obtain generator efficiency, but the measurement accuracy is limited to testing under small temperature gradients [2,3,4]. Thermoelectric generator efficiency can also be determined through comparative heat flow, and this method offers a more direct and realistic measurement of a generators efficiency [5].
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EXPERIMENTAL SETUP
Figure 1 shows the method of measuring generator efficiency by comparative heat flow by which a generator is sandwiched between two standard reference materials (SRM) of known thermal conductivity. A heater source and sink induce a uniform heat flow through the reference materials and generator. For the system presented here, heat flow is monitored into and out of the gen
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