To overcome the restrictions on electric vehicles ranges on winter term conditions, due to the heating demand of the interior, the use of a Thermal High Performance Storage with metallic Phase Change Materials is one possible solution. A new storage concept, using a so called Heat Transport System, enabling the heat transfer from the storage to a vehicles cooling fluid by evaporation and condensation of a working fluid within a closed circle, is introduced in this study. The influence of the storage on an electric vehicles range is exemplary shown for DLR´s Urban Modular Vehicle Concept for a motorway cycle by theoretical investigations. An increase of range by 36,3 km resp. 18,4 % for an ambient temperature of -10 °C and 46 km resp. 26,7 % for an ambient temperature of -20 °C could be reached. The energy densities of the designed storages reach values of more than 220 Wh/kg resp. more than 310 Wh/l. The cost estimations for those storage systems are approx. 445 € resp. 660 €. A comparison between the thermal energy storage and a conventional heating system consisting out of a PTC-Heater and a battery show, that the conventional heating system has a mass which is about two thirds higher, a volume which is more than one third higher and a quadrupled price compared to the thermal energy storage.
To meet the future development in vehicle drivetrains, the Institute of Vehicle Concepts of the German Aerospace Center (DLR) aims to prove, that exhaust heat recovery using a Thermoelectric Generator (TEG) is, even with more electrification, still a promising concept to increase efficiency. Together with material researches at the Fraunhofer Institute of Physical Measurement Techniques (IPM) in Freiburg, the DLRs next generation of TEG is adapted to the special boundary conditions in hybrid vehicles. After investigating and measuring these boundary conditions, a first potential analysis is made. In test cycles a potential reduction of fuel consumption of about 3 % is calculated. It has been shown, that under exemplary driving conditions the possible electric power output of a TEG can be increased, compared to conventional vehicle, despite the increased efficiency of the drivetrain in a hybrid. Keywords-thermoelectric generator; range extended and hybridelectric vehicles; potentials of thermoelectric energy conversion; boundary conditions for TEG integration; complete system analysis;I.
Despite the ongoing electrification of vehicle propulsion systems, vehicles with combustion engines will continue to bear the brunt of passenger services worldwide for the next few decades. As a result, the German Aerospace Center Institute of Vehicle Concepts, the Institute of Materials Research and the Institute of Technical Thermodynamics have focused on utilising the exhaust heat of internal combustion engines by means of thermoelectric generators (TEGs). Their primary goal is the development of cost-efficient TEGs with long-term stability and maximised energy yield. In addition to the 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 work and reveals an expedient module design for use in TEGs suitable for vehicles. The TEM requirements identified, which were obtained by means of experiments on the test vehicle and test bench, are described first. Doped semiconductor materials were produced and characterised by production methods capable of being scaled up in order to represent series application. The results in terms of thermoelectric properties (Seebeck coefficient, electrical conductivity and 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 of material stability were carried out in addition to the TEM's thermodynamic and thermoelectric design. The film sequence within the module represented a special challenge. Multilayer films facilitated adaptation of the thermal and mechanical properties of plasmasprayed films. A joint which dispenses with solder additives was also possible using multilayer films. The research resulted in a functionally-optimised module design, which was enhanced for use in motor vehicles using process flexibility and close-to-production manufacturing methods.
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