A Review of Developments in Electrical Battery, Fuel Cell and Energy Recovery Systems for Railway Applications: a Report for the Scottish Association for Public Transport

This report outlines the current status of batteries, hydrogen fuel cells and short-term energy storage systems for railway and tramway applications. The report includes discussion of issues associated with regenerative braking and the recovery of energy that would otherwise be dissipated as heat during braking. As well as feeding energy back to the supply grid, as in the case of conventional electrified rail systems, energy recovery may also be achieved using batteries, supercapacitors, flywheels or hydraulic devices and developments in each of these areas are reviewed. The advantages of hybrid systems that involve combinations of different power sources and energy storage methods are emphasised and some associated design optimisation issues are discussed. For each of the developments mentioned, there is a brief account given of some transport applications in the United Kingdom and elsewhere. This is a rapidly developing field and operating experience with vehicles currently entering service in various countries will provide important additional insight within the next two or three years

An integrated energy-efficient operation methodology for metro systems based on a real case of Shanghai Metro Line One

Metro systems are one of the most important transportation systems in people's lives. Due to the huge amount of energy it consumes every day, highly-efficient operation of a metro system will lead to significant energy savings. In this paper, a new integrated Energy-efficient Operation Methodology (EOM) for metro systems is proposed and validated. Compared with other energy saving methods, EOM does not incur additional cost. In addition, it provides solutions to the frequent disturbance problems in the metro systems. EOM can be divided into two parts: Timetable Optimization (TO) and Compensational Driving Strategy Algorithm (CDSA). First, to get a basic energy-saving effect, a genetic algorithm is used to modify the dwell time of each stop to obtain the most optimal energy-efficient timetable. Then, in order to save additional energy when disturbances happen, a novel CDSA algorithm is formulated and proposed based on the foregoing method. To validate the correctness and effectiveness of the energy-savings possible with EOM, a real case of Shanghai Metro Line One (SMLO) is studied, where EOM was applied. The result shows that a significant amount of energy can be saved by using EOM

Powering Future Transport in Scotland: A Review for the Scottish Association for Public Transport

This report discusses energy costs and emissions associated with transport in Scotland and reviews options for future power sources for different modes of public transport. Transport provides a major contribution to greenhouse gas and other harmful emissions worldwide and efforts to reduce these are important for all forms of public transport, as well as for private cars and for the movement of freight. The effects of transport policy decisions are recognised, increasingly, as being very important for the electricity supply industry at national and local levels, largely because of the growth in the numbers of electric and hybrid road vehicles. Moving from oil to low carbon energy for transport raises important issues for electrical power generation and distribution systems in addition to challenges already being faced by the electrical power industry as the proportion of generating capacity involving renewables increases. The report starts by considering current energy costs and emissions for different forms of passenger transport and then outlines some current developments in areas such as internal combustion engine technology, battery storage systems and hydrogen fuel cells. Systems involving short-term energy storage and recovery of energy that would otherwise be dissipated as heat during braking are also discussed. Such systems generally involve the use of super-capacitors, flywheels or hydraulic devices. References are provided to the sources of data used in the analysis carried out for this review and, also, to sources of information about relevant developments in science and engineering. For all the new developments mentioned, there is a brief review of some transport applications in the United Kingdom and elsewhere. The possible impact of autonomous vehicles on future car ownership is still not known and the effects of this technology on public transport remain uncertain. As well as discussing autonomous road vehicles, the report makes brief mention of the potential of autonomous systems and increased automation for rail transport and for tramway operations. The benefits of further conventional railway electrification are reviewed in terms of energy usage, costs and emissions and the advantages of a more integrated approach to the provision of public transport in Scotland are emphasised. The value of using mathematical modelling and simulation methods to explore options in transport systems developments and planning is discussed, and the importance of testing simulation models in ways that are appropriate for the intended application is emphasised. This review presents the first results from a continuing study which was started in 2018 and is intended to provide information that should be relevant for those involved in decision-making in Scotland at the time of publication. The quantitative information contained within it clearly needs to be updated on a regular basis. The review concludes with recommendations for the Scottish Association for Public Transport about possible priorities for its efforts to increase public awareness about transport issues and is intended to be the first of a series of publications on transport and energy issues in the Scottish context. The references form an important part of the report and provide a potentially important bibliography which must be augmented and updated regularly

Cooperative control of high-speed trains for headway regulation: A self-triggered model predictive control based approach

The advanced train-to-train and train-to-ground communication technologies equipped in high-speed railways have the potential to allow trains to follow each with a steady headway and improve the safety and performance of the railway systems. A key enabler is a train control system that is able to respond to unforeseen disturbances in the system (e.g., incidents, train delays), and to adjust and coordinate the train headways and speeds. This paper proposes a multi-train cooperative control model based on the dynamic features during train longitude movement to adjust train following headway. In particular, our model simultaneously considers several practical constraints, e.g., train controller output constraints, safe train following distance, as well as communication delays and resources. Then, this control problem is solved through a rolling horizon approach by calculating the Riccati equation with Lagrangian multipliers. Due to the practical communication resource constraints and riding comfort requirement, we also improved the rolling horizon approach into a novel self-triggered model predictive control scheme to overcome these issues. Finally, two case studies are given through simulation experiments. The simulation results are analyzed which demonstrate the effectiveness of the proposed approach

The use of linear motor technology to increase capacity in conventional railway systems

PhD ThesisWheel/rail adhesion is an important constraint on the design and operation of conventional railways. The research question considered for this thesis is whether linear motor technology can improve the performance of railway systems by reducing the dependence of tractive and braking effort on the available wheel/rail adhesion. The two principal contributions of the research are an analysis of the influence of several different linear motor technologies on the capacity of conventional railways, and the development of a new design concept for train braking (named LEMUR – Linear Electromagnetic Machine Using Rails). Multi-train simulation of three different railway networks was used to investigate the capacity benefits and energy consumption of the LEMUR concept, along with four other existing or proposed implementations of linear induction motor technology with the running rail used as the secondary component of the motor. A model of each network was built using OpenTrack software, and Monte Carlo simulation with pseudorandom distributions of initial delays to train services was carried out to compare train movements under the influence of the delays typically encountered during day-to-day operation. An indication of the improvements in railway capacity possible with different linear motor technology options was then derived from these simulations. The results of the experiments indicate that the LEMUR concept provided the greatest increase in capacity and the lowest energy consumption of the five linear motor technology options tested. Although the limitations of the study do introduce some uncertainty into the precise values of capacity and energy consumption obtained, the experimental methods were considered sufficiently robust for this conclusion to remain valid. The most promising application in the study was suburban passenger services that are part of busy mixed-traffic networks. Here, the capacity benefits of the LEMUR concept appear to show sufficient promise to justify further development and application

Control of Energy Storage

Energy storage can provide numerous beneficial services and cost savings within the electricity grid, especially when facing future challenges like renewable and electric vehicle (EV) integration. Public bodies, private companies and individuals are deploying storage facilities for several purposes, including arbitrage, grid support, renewable generation, and demand-side management. Storage deployment can therefore yield benefits like reduced frequency fluctuation, better asset utilisation and more predictable power profiles. Such uses of energy storage can reduce the cost of energy, reduce the strain on the grid, reduce the environmental impact of energy use, and prepare the network for future challenges. This Special Issue of Energies explore the latest developments in the control of energy storage in support of the wider energy network, and focus on the control of storage rather than the storage technology itself

Energy management strategy to optimise regenerative braking in a hybrid dual-mode locomotive

This study proposes an energy management strategy (EMS) for a dual-mode hybrid locomotive equipped with a fuel cell, supercapacitors, and batteries, and intermittent access to an electrified overhead catenary. It is inspired by the Ragone plot and does not consider information or predictions of future load consumption. It aims to reduce a cost function that considers the cost of hydrogen, the electricity consumed from the network, and the energy sources' degradation. The EMS focuses on maximising the energy recovered during braking. The study introduces a methodology to tune the EMS parameters. Two study cases are used to evaluate the EMS. In the evaluation driving profile, typical for a French freight train, the braking energy is around 12.8% of the total energy. With the proposed EMS, the energy recovered is around 99.8% of the total braking energy. A second EMS not oriented to reduce the energy in the braking resistor is also evaluated. The energy recovered with this strategy is around 91.5% of the total braking energy. The global energy reduction is around 1.1% compared with the second EMS and 12.8% without energy recovering. These results show a real opportunity to increase the energy recovered during braking

Increasing urban tram system efficiency, with battery storage and electric vehicle charging

This paper examines the possible placement of Energy Storage Systems (ESS) on an urban tram system for the purpose of exploring potential increases in operating efficiency through the examination of different locations for battery energy storage. Further, the paper suggests the utilisation of Electric Vehicle (EV) batteries at existing Park and Ride (P&R) sites as a means of achieving additional energy storage at these locations. The study achieves this through MATLAB modelling utilising captured GPS data and publically available information. This study examines the scenario of uni-directional substations with no interconnection between the overhead catenary for both directions of travel, and discusses the trade-offs between ESS size and required current limits. The results show the savings in both energy and basic CO2 emissions alongside the discussion of Return on Investment (RoI) that can be achieved through the potential installation of ESS at identified ideal locations along the tram network. Moreover, this may be extended to the use of EVs as stationary ESS sited at the existing P&R facilities. Further, the model may also be used to inform future infrastructure upgrades and potential improvements to air quality within urban environments

The impact of the overhead line's power supply system spatial differentiation on the energy consumption of trolleybus transport: planning and economic aspects

Nowadays the issue of electric energy saving in public transport is becoming a key area of interest, which is connected both with a growth in environmental awareness of the society and an increase in the prices of fuel and electricity. It can be achieved by reducing of the transmission losses in supply system or by the improving of the usage of the regenerative breaking. The spatial differentiation of the energy supply system of public transport is one of the elements, which has significant impact on the energy consumption. Paper presents the theoretical analysis of the impact of supply system topology on the energy consumption and extensive measurement analysis realized in Gdynia (Poland) trolleybus system. First published online: 13 Oct 201