Gesamtkosten- und emissionsoptimierte Systemauslegung von Nutzfahrzeug-Hybridantriebssträngen

  • Optimal system design for commercial vehicle powertrains based on total cost of ownership and emmissions

Maiterth, Johannes Moritz; Pischinger, Stefan (Thesis advisor); Eckstein, Lutz (Thesis advisor)

Aachen (2022)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022

Abstract

In the thesis "Optimal System Design for Commercial Vehicle Powertrains based on Total Cost of Ownership and Emissions", a methodology for powertrain design is developed with which the hybrid-electric powertrain of commercial vehicles can be optimized for the respective utilization profile. The needs of manufacturers and users are taken into account. The goals are on the one hand the reduction of pollutant emissions and CO2 for the manufacturer and on the other hand the rapid amortization of the additional costs based on a TCO analysis for the user. This optimization is applied to two examples of heavy commercial vehicles in long-distance and distribution operations as HEVs and two further examples of medium-duty commercial vehicles in urban and regional distribution operations as HEVs and PHEVs. Based on a market study, an introduction to the topic of electrified commercial vehicles and also into the CO2 legislation is given. Subsequently, the state of the art is explained in terms of a total cost of ownership analysis. In addition, the important topics of exhaust gas after treatment and powertrain system design will be introduced. By means of a scenario definition and various commercial vehicle-relevant requirements, the framework conditions for the simulation study are defined. As a first step for the system design, the topology selection is carried out on the basis of a morphological box and a P2 arrangement was chosen for both medium and heavy-duty commercial vehicle applications. In addition, the simulation and component models and scaling approaches are explained. As an approach for the optimization, design of experiments with subsequent minimization of the payback period is used, while keeping the constraints for emissions. For the system design the following conclusions can be drawn. The optimization goal and the weighting of the optimization parts must be clearly defined in advance. It is possible to simultaneously evaluate the amortization, the operation strategy and to optimize emissions. With the introduction of CO2 legislation in Europe, the focus will be more on vehicle electrification since all optimized hybrid vehicles save CO2 . Although depending on the scenario, the end customer may have to take a longer payback period into account. With rising fuel costs, hybridization will become more attractive for end customers due to the savings in operating costs. As a result of more frequent engine stop phases and thus repeatedly falling temperatures in the exhaust tract, the exhaust system must also be considered in the hybrid system design. Due to the CO2 legislation, the focus for savings will probably be mainly on heavy trucks for long-distance transport, although the required CO2 savings of 15 % cannot only be achieved through hybridization. However, hybridization can make a contribution, as shown in the case study "5-LH" with 9,6 % (weighted) CO2 savings. In order for the hybrid systems to be profitable for the end customer, customer-specific driving cycles must also be taken into account in the selection process. Due to the high mileage of the vehicles cycle-stable battery cells should be used. Depending on the application, very high fuel savings can be achieved in medium-duty distribution transport. However, these systems require an increased mileage despite the high percentage savings for the amortization and were not profitable in the chosen scenarios. The PHEV system is profitable if there is enough electrical range implemented and electrical energy provides cost savings, whereby increased differential costs compared to a HEV must be compensated.

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