Abstract
The development of more sustainable and zero-emissions collective transport solutions could play a very important measure in the near future within smart city policies. This paper tries to give a contribution to this aim, proposing a novel approach to fuel cell vehicle design and operation. Traditional difficulties experienced in fuel cell transient operation are, in fact, normally solved in conventional vehicle prototypes, through the hybridization of the propulsion system and with the complete fulfillment of transients in road energy demand through a high-capacity onboard energy storage device. This makes it normally necessary to use Li-ion battery solutions, accepting their restrictions in terms of weight, costs, energy losses, limited lifetime, and environmental constraints. The proposed solution, instead, introduces a partitioning of the hydrogen fuel cell (FC) and novel optimal power control strategy, with the aim of limiting the capacity of the energy storage, still avoiding FC transient operation. The limited capacity of the resulting energy storage systems which, instead, has to answer higher power requests, makes it possible to consider the utilization of a high-speed flywheel energy storage system (FESS) in place of high energy density Li-ion batteries. The proposed control strategy was validated by vehicle simulations based on a modular and parametric model; input data were acquired experimentally on an operating electric bus in real traffic conditions over an urban bus line. Simulation results highlight that the proposed control strategy makes it possible to obtain an overall power output for the FC stacks which better follows road power demands, and a relevant downsizing of the FESS device.
Highlights
The transport sector accounts for about 30% of world energy demands, this being still mainly fulfilled by fossil oil-derived fuels, generating more than 30% of total GHG emissions
The authors propose the design of a novel hydrogen-fueled hybrid power unit for zero-emission
The authors propose thethe design of a novel hydrogen-fueled hybrid power unita for zero-emission city transit bus applications; powertrain consists of an electric drive fed by hybrid power unit city transit bus applications; the powertrain consists of an electric drive fed by a hybrid power unit composed of a functional coupling of a high specific power flywheel energy storage system (FESS)
Summary
The transport sector accounts for about 30% of world energy demands, this being still mainly fulfilled by fossil oil-derived fuels, generating more than 30% of total GHG emissions. The authors’ opinion is that limiting the attention to urban buses, BEVs, and HFCVs provide the most promising alternatives: the choice of the best solution is affected by the path used in electricity or hydrogen production (e.g., fossil fuel reformulation or water electrolysis in the case of hydrogen), so it may vary locally and during time, as far as renewables share increases in electric energy production In any case, both systems guarantee a substantial bettering with respect to conventional vehicles, making it locally possible not to generate any pollutant emission [20,21,22,23,24].
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