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Modeling and sizing of a TEG with half-heusler TE legs for reducing fuel consumption in a heavy duty vehicle

: Contet, A.; Lhomme, C.; Zuckermann, D.; Fey, A.; Rouaud, C.; Cimen, T.; Rabanser, P.; Rost, A.; Trache, M.; Feng, B.

Warrendale, Pa.: SAE, 2019
SAE Technical Papers, 2019-01-0897
Society of Automotive Engineers (SAE World Congress) <2019, Detroit/Mich.>
Fraunhofer IKTS ()

Following a historical increase in energy demand, the use of fossil fuels is causing irreversible damages to the environment, while local pollutant emissions must comply with ever more stringent emissions legislation. Waste Heat Recovery (WHR) devices and particularly Thermo-Electric Generators (TEG) using Seebeck effect have often been seen as levers to improve those conflicting objectives, but yet are so far limited to niche market due to the use of expensive, scarce or toxic thermoelectric (TE) elements (Bi, Pb, Te). Within the European project INTEGRAL, a consortium of 13 companies and research organizations tackling with upscaling the production of the next generation TE materials, a TEG dedicated to heavy-duty trucks using half-Heusler TE material is being developed. First, a TEG system integration model has been developed and iterated in steady-state to provide TE Module (TEM) specifications. In this approach, typical truck operating points have been used, along with specific TEG impacts on both engine and vehicle, like additional weight and pressure drops, while aiming at a return of investment for the truck operator. Then, the TEMs were assembled and tested on a dedicated performance test bench. The measured TEM outputs including idle voltage, internal resistance, heat transfer and Peltier effect were compared to previous predictions. A root cause analysis was then conducted to explain the mismatches. The first step was to track and eliminate the errors in the test setup itself. The second step was to investigate local losses in the TEM, including layer-by-layer thermal contact and thermal by-pass of the TE material through conduction, convection and radiation. Lastly, the improved TEG model was used in a transient simulation platform to take into account the TEG thermal masses on the electric output. Finally, vehicle simulations were performed to update the fuel economy with TEG installed on a hybrid electric powertrain.