Characterization of Thermoelectric Generator Modules: A transient TEG measurement apparatus (T-TEGMA)

Kurzfassung

"Reliable characterization of thermoelectric modules (TEM) is important for the validation of device measurands in commercial and industrial applications. Various characterization methodologies are reported including reference and absolute principles. As a counterpart to established steady state methods we propose a transient mode TEM characterization methodology, mainly, since steady-state techniques require long characterization times due to slow temperature stabilization related to the massive components (heater block, heat flow meters, cross sectional adaptors) in a conventional reference method for TEM measurement as implemented, e.g. in the TEGMA apparatus developed at German Aerospace Center (DLR). As a methodological increment to the steady state method, the transient thermoelectric measurement apparatus (T-TEGMA) implements a transient mode based on a continuous slow temperature ramp up with a continuous characterization of the module parameters. A simplified device model based on the constant property assumption justifies that the established measurement principle of the steady state can be transferred to the transient mode taking into account corrections due to the heat capacity of the involved components which are of minor magnitude if the ramping sweep rate is low. Here a detailed presentation of the design of the T-TEGMA is introduced along with a discussion of the components, sensor instrumentation and control functions. An active cooling mode for the heater block was implemented to shorten the cool-down period. Functional tests and results are reported, which includes referencing and validation of the new T-TEGMA machine to the classic TEGMA by comparing the thermal and electrical measurands. The TEM parameters obtained using the transient method are compared to the results obtained by the steady-state method, thereby providing an estimate on the measurement accuracy of the transient method."