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B2: Module design
Despite the ongoing electrification of vehicle propulsion systems, combustion-engine vehicles will continue to bear the brunt of passenger services world-wide for the next several decades. As a result, the DLR Institute of Vehicle Concepts, the Institute of Materials Research and the Institute of Technical Thermodynamics focused on utilizing exhaust heat of combustion engines through thermoelectric generators (TEG). Its primary goal is the development of cost-efficient TEG with long-term stability and a maximized energy yield.
In addition to overall TEG system design, the development of long-term stable, efficient thermoelectric modules (TEMs) for high-temperature applications is a great challenge. This paper presents the results of internal development activities and reveals an expedient module design for use in TEGs suitable for vehicles.
The TEM requirements identified which were obtained by means of experimental investigations in the test vehicle and on the test bench, are first described.
Doped semiconductor materials were fabricated and characterized with production methods capable of being scaled up in order to represent series application. The results in terms of thermoelectric properties (Seebeck coefficient, electrical conductivity, thermal conductivity) were used for the simulative design of a thermoelectric module using a constant-property model and with the aid of FEM calculations.
Thermomechanical calculations concerning material stability were done in addition to the TEM's thermodynamic and thermoelectric design. An essential element was formulation of a thermomechanical analogous model of the TEM in order to enable time-efficient variational calculus of the overall structure.
The film sequence within the module posed a special challenge. Multilayer films enabled adaptation of the thermal and mechanical properties of plasma-sprayed films. A joint that manages without solder additives was also possible using multilayer films.
The research resulted in a function-optimized module design, which was optimized for use in motor vehicles using process flexibility and close-to-production manufacturing methods.
