Modelling and Simulation of Hybrid Electric Trains Powered by Hydrogen Fuel Cells and Batteries for Routes in the Highlands of Scotland : Preliminary Results

Murray-Smith, D. (2020) Modelling and Simulation of Hybrid Electric Trains Powered by Hydrogen Fuel Cells and Batteries for Routes in the Highlands of Scotland : Preliminary Results. Technical Report. Scottish Association for Public Transport, Glasgow.

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This report builds on an earlier review for the Scottish Association for Public Transport on the potential of batteries, hydrogen fuel cells and other short-term energy storage systems for railway and tramway applications. It outlines the development of a train performance model and associated computer simulation software for a design of hybrid multiple unit, powered by a combination of hydrogen fuel cells and batteries. Assumptions underlying the model are discussed in detail. The chosen mode of operation involves steady state conditions for the fuel cells, with the batteries being used to provide additional stored energy for use on gradients and when the train is accelerating. The simulation techniques involve a mix of conventional “forward” simulation and an approach based on an “inverse” simulation method. Simulation results presented are for a case study involving a short section of route chosen to be typical of sections of many rural routes in Scotland, such as the West Highland lines and routes north and west of Inverness or to and from Stranraer. Data relating to the performance of Class 156 diesel multiple units currently used on non-electrified railway lines in Scotland have provided a point of reference in assessing the performance of the hybrid multiple units. Although other studies of hybrid rail vehicles involving hydrogen fuel cell and battery combinations have been published, those have involved routes that are shorter, with more intermediate stations and no prolonged gradients. Conclusions are presented in terms of fuel cell and battery power levels and battery storage capacity required for operation on the type of route being considered. The most important conclusion is that a preliminary specification for a hybrid two-coach unit could involve two 200 kW traction motors, fuel-cells providing a maximum power output of 350 kW and a battery pack giving a maximum power output of 250 kW and 75 kWh of electrical energy storage capacity. Using standard components that are available commencially, approximate calculations suggest that a design based around these power ratings could be implemented within a target weight of 90 tonnes for a two-coach unit. However, it is thought that the limitations of the UK loading gauge could present difficulties in terms of the space required and implementation might only be possible at the cost of some passenger space. Suggestions are made in the report for further simulation work involving a three-coach configuration and for the addition of a pantograph and associated electrical equipment to allow power to be drawn from 25 kV overhead wiring when the unit is operating on electrified routes. Another important recommendation for further work involves development of a detailed route model for a typical line, including exact information about gradients, curvature and local speed restrictions. Assessment of possible journey-time reductions is also important and preliminary results are presented, for the specification given above, using inverse simulation methods. Potential journey-time reductions over a complete route or specific sections could be investigated in future work. Issues of weight could also be linked to performance within the simulation software and advice could be provided to the user when space or weight constraints are violated. The report includes discussion of possible benefits of developing more detailed, physics-based, sub-models of elements such as fuel cells, batteries, traction motors and power electronic components which could be used to replace the much simpler sub-models used in the existing simulation model. This might allow use of well-established and validated sub-models and would extend the range of issues that could be addressed through simulation and allow more accurate assessment of losses in batteries, power electronic components and traction motors over the full range of operating conditions. This could also be of value for checking underlying assumptions within the model and for the development of control and energy management strategies. The report recommends the use of both forward and inverse methods of simulation for applications of this kind as these two approaches, taken together, can provide additional insight that is not obtained so readily from the use of conventional forward simulation methods alone.

Item Type:Research Reports or Papers (Technical Report)
Keywords:Rail traction, hybrid vehicles, electrical battery, hydrogen fuel cells, computer simulation, inverse simulation, railways in Scotland.
Glasgow Author(s) Enlighten ID:Murray-Smith, Professor David
Authors: Murray-Smith, D.
Subjects:T Technology > TF Railroad engineering and operation
T Technology > TJ Mechanical engineering and machinery
T Technology > TK Electrical engineering. Electronics Nuclear engineering
College/School:College of Science and Engineering > School of Engineering
Publisher:Scottish Association for Public Transport
Copyright Holders:Copyright © 2020 The Author
Publisher Policy:Reproduced with the permission of the Author

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