Abstract
A test facility for graded thermoelectric elements has been developed, which simulates application relevant thermal conditions. The typical case of thermogenerator (TEG) use implies a difference of several hundred degrees between its hot and cold side. Therefore, the TEG device behaviour is essentially influenced by its transport properties' temperature dependence. In a vacuum chamber, reference blocks for heat flow determination are serially connected to the generator sample. Special solutions have been found to prevent disturbance of the heat flux distribution due to radiation. Ductile and liquid metal interlayers have been used to obtain good electrical and thermal coupling between sample and reference. A fine tuning of very low resistive loads is required to study the efficiency and electrical power output for arbitrary temperature conditions. For this purpose, a computer controllable electrical load with high accuracy has been developed. The operation of this new set-up has been tested. This includes the examination of segmented thermoelectric (TE) elements composed of FeSi 2 with different dopings. The thermo-voltage, resistance, thermal conductance and effective figure of merit Z have been measured. The method allows to compare the properties of real graded systems with the TE material properties to estimate the influence of material contacts. An experimental valuation of the theoretically predicted operating conditions for maximum efficiency and maximum power output, respectively, is enabled.
Published Version
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