Holistic Development of Thermoelectric Generators for Automotive Applications

Abstract

One of the major challenges of the future automotive development is to achieve the required reductions of the CO2 emissions. Therefore, it is necessary to investigate all potential technologies for efficiency improvement. In a combustion engine, about 2/3 of the chemical energy of the fuel is dissipated as waste heat. Due to its high temperature level, the waste heat in the exhaust gas is very promising for the technology of thermoelectric generators (TEG). In this work the methodology for a holistic TEG optimization for automotive vehicle applications will be presented. Thereby, all system interactions between the vehicle and the TEG are modelled and the CO2 reduction can be optimized within the vehicle system. Moreover the costs are calculated for each TEG design, and the method realizes an optimization of the cost–benefit ratio in a direct way. The optimization method is applied with a highly integrated TEG design, which has been developed to be compact and lightweight. Through the combination of improvements in TEG design and system optimization, a gravimetric power density of 267 W/kg and a volumetric power density of 478 W/dm^3 could be achieved. These power densities are about 900% and 700%, respectively, higher than the state of the art. The optimization method was applied exemplarily to a conventional vehicle (Volkswagen Golf VII) and a hybrid vehicle (Opel Ampera/Chevrolet Volt). As a result, reductions in consumption and CO2 emissions of up to 2.2% for the conventional and 3.4% for the hybrid vehicle could be achieved within the worldwide harmonized light duty driving test cycle. The cost–benefit optimum is 81.3 €/(g/km) for the conventional vehicle and 54.8 €/(g/km) for the hybrid vehicle in charge sustaining mode.