Evaluation of monolithic and segmented thermoelectric materials using a potentiometer-type high accuracy generator test facility

A facility for investigating the thermal and electrical properties of a thermoelectric generator in an environment close to reality and the thermal resistance of multi-layer specimen has been constructed at DLR. Quantities such as output power and efficiency, output voltage and current, inner resistance, and overall thermal conductance can be determined under vacuum or inert gas, but also in oxidising atmosphere. The heat flow through the generator is measured via the temperature gradient in a reference block at the hot side. The cold side heat flux is measured by a commercial heat flux meter, a second reference block or a combination of both. This redundant measurement provides a sensitive indicator for systematic errors caused by incomplete thermal shielding which would lead to thermal bypasses. Comparison of our generator tests a comparison with by a similar apparatus at another institution gives evidence for good measuring accuracy. The relative error of the resulting parameters is in the range of 5%. The method of heat flow detection in the GTF can also be used for thermal resistance investigations, especially on multi-layer systems of too low thermal conductivities for appropriate measurements by laser flash.