Development and analysis of new pneumatic based powering options for transit buses: A comparative assessment

Carbon dioxide reduction has been the central focus of current climate change public policy and largely determines procurement of next generation 'clean' transit buses. Development of alternative nature-friendly systems for clean transportation is critical in the transition of the sector from conventional fossil fuel-based powertrains. The current study undertakes the design and analysis of a newly-developed hybrid pneumatic powertrain concept for fourty-foot public transit buses using liquid nitrogen and compressed natural gas as a secondary fuel. Various fuel types for system hybridization are investigated comparatively in terms of fuel economy and well-to-wheel carbon dioxide emission ratios. A pure pneumatic configuration is also considered as a base case and discussed accordingly. The performance of the proposed system is evaluated through parametric studies by considering primary design and operational parameters. In similar operational conditions, the performance of a conventional diesel bus, a plug-in hybrid electric bus, a battery-electric bus and a hydrogen fuel cell electric bus is considered in the further comparative assessment of the proposed system. From a well-to wheel point of view, the emission ratio of the developed hybrid pneumatic system is evaluated at 0.1452 kg carbon dioxide equivalent per kilometer of city driving, which corresponds to a 95% emission reduction compared to conventional diesel buses. The present study results indicate that a hybrid pneumatic configuration carries significant potential for a green transition in the public transit sector. Furthermore, eliminating the need for charging infrastructure, grid upgrading and additional infrastructure capacity, the system can be assembled with readily available off-the-shelf components.

Automated summary

This study designs and analyzes a newly-developed hybrid pneumatic powertrain system for public transit buses, comparing different fuel types for hybridization. The results show that the hybrid pneumatic configuration has significant potential for a green transition in the public transit sector.