Opportunities for Medium and Heavy Duty Vehicle Fuel Economy Improvements through Hybridization

Daniela Nieto Prada; Ram Vijayagopal; Vincent Costanzo

doi:10.4271/2021-01-0717

The objective of this study was to evaluate the fuel saving potential of various hybrid powertrain architectures for medium and heavy duty vehicles. The relative benefit of each powertrain was analyzed, and the observed fuel savings was explained in terms of operational efficiency gains, regenerative braking benefits from powertrain electrification and differences in vehicle curb weight. Vehicles designed for various purposes, namely urban delivery, utility, transit, refuse, drayage, regional and long haul were included in this work. Fuel consumption was measured in regulatory cycles and various real world representative cycles.

A diesel-powered conventional powertrain variant was first developed for each case, based on vehicle technical specifications for each type of truck. Autonomie, a simulation tool developed by Argonne National Laboratory, was used for carrying out the vehicle modeling, sizing and fuel economy evaluation. Performance based sizing rules implemented in Autonomie were used to determine the component sizes for the hybridized concept trucks. In addition to the conventional baseline, a 48V start-stop system, parallel pre-transmission system and a series plug in hybrid system were considered in this work.

This study shows that not all trucks can utilize engine downsizing as part of hybridization strategy. Hybrid trucks designed to match conventional vehicle performance in all functional requirements, will require engines that are comparably sized as the conventional counterparts. Plug in hybrids can have downsized engines and still meet performance goals, as the larger battery packs can be used to assist engine for a longer period of time. Depending on the drive cycle, the observed fuel economy for the hybrid powertrains will vary. It could be comparable to that of baseline vehicle in highway driving while resulting in over 30% fuel savings in more transient drive cycles.

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Opportunities for Medium and Heavy Duty Vehicle Fuel Economy Improvements through Hybridization 2021-01-0717

SAE MOBILUS