Abstract
The status of metrology for the characterization of thermoelectric generator modules (TEM) is investigated in this work by an international round robin (RR) test including twelve laboratories from nine countries on three continents. Measurements have been performed with three samples of a Bi2Te3-based commercial TEM type, which has prevailed over three competing types during previous tests on the short- and long-term stability. A comparison of temperature-dependent results is provided up to 200 °C hot side temperature for the maximum power output Pmax, the incident heat flow (at maximum efficiency conditions), and the maximum efficiency ηmax. Data evaluation from all RR participants reveals maximum standard deviations for these measurands of 27.2% (Pmax), 59.2% (), and 25.9% (ηmax). A comparison between RR data sets and reference data from manufacturer specifications shows high deviations of up to 46%, too. These deviations reflect the absence of measurement guidelines and reference samples and confirm the need for improvements in the standardization of TEM metrology. Accordingly, the results of the RR are presented against the background of our own investigations on the uncertainty budgets for the determination of the abovementioned TEM properties using inhouse-developed characterization facilities, which comprise reference and absolute measurement techniques for the determination of heat flow.
Highlights
Thermoelectric generator (TEG) systems are suited to supply electric energy by the direct conversion of waste heat from mobile applications [1,2,3,4] and stationary processes [5,6,7]
TEGs consist of one or multiple thermoelectric generator modules (TEM), which operate within heat transmission paths between heat reservoirs
In addition to previous publications, which have quantified the uncertainty of heat flow measurement on a thermal reference material [51] and the uncertainty of module resistance measurements [52], we report on the uncertainty budget for the maximum power, heat flow, and efficiency measurement on a TEM in this work, in order to allow for a conclusive interpretation of observed deviations between round robin (RR) results
Summary
Thermoelectric generator (TEG) systems are suited to supply electric energy by the direct conversion of waste heat from mobile applications [1,2,3,4] and stationary processes [5,6,7]. Development of high-precision characterization methods and their transformation into primary methods with specified uncertainty budgets and traceability of measurands is required Several works with this focus have been accomplished in the field of TE material characterization, yielding uncertainty analyses for commercial or custom-made measurement systems for the determination of the Seebeck coefficient and the electric resistivity [36,37,38], as well as for zT measuring systems [39]. Besides discussion of the RR results, a brief summary of experiments for module sample selection will be given, in addition to further relevant information on the organization of comparative RR tests and their technical concept
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