831 research outputs found

    Assessment of the worthwhileness of efficient driving in railway systems with high-receptivity power supplies

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    Eco-driving is one of the most important strategies for significantly reducing the energy consumption of railways with low investments. It consists of designing a way of driving a train to fulfil a target running time, consuming the minimum amount of energy. Most eco-driving energy savings come from the substitution of some braking periods with coasting periods. Nowadays, modern trains can use regenerative braking to recover the kinetic energy during deceleration phases. Therefore, if the receptivity of the railway system to regenerate energy is high, a question arises: is it worth designing eco-driving speed profiles? This paper assesses the energy benefits that eco-driving can provide in different scenarios to answer this question. Eco-driving is obtained by means of a multi-objective particle swarm optimization algorithm, combined with a detailed train simulator, to obtain realistic results. Eco-driving speed profiles are compared with a standard driving that performs the same running time. Real data from Spanish high-speed lines have been used to analyze the results in two case studies. Stretches fed by 1 × 25 kV and 2 × 25 kV AC power supply systems have been considered, as they present high receptivity to regenerate energy. Furthermore, the variations of the two most important factors that affect the regenerative energy usage have been studied: train motors efficiency ratio and catenary resistance. Results indicate that the greater the catenary resistance, the more advantageous eco-driving is. Similarly, the lower the motor efficiency, the greater the energy savings provided by efficient driving. Despite the differences observed in energy savings, the main conclusion is that eco-driving always provides significant energy savings, even in the case of the most receptive power supply network. Therefore, this paper has demonstrated that efforts in improving regenerated energy usage must not neglect the role of eco-driving in railway efficiency

    Optimizing speed profiles for sustainable train operation with wayside energy storage systems

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    Large hauling capability and low rolling resistance has put rail transit at the forefront of mass transportation mode sustainability in terms of congestion mitigation and energy conservation. As such, rail vehicles are one of the least energy-intensive modes of transportation and least environmentally polluting. Despite, these positives, improper driving habits and wastage of the braking energy through dissipation in braking resistors result in unnecessary consumption, extra costs to the operator and increased atmospheric greenhouse gas emissions. This study presents an intelligent method for the optimization of the number and locations of wayside energy storage system (WESS) units that maximize the net benefits of the operation of a rail line. First, the optimized speed profiles with and without WESS is determined for a single alignment segment. Then, using the speed profiles obtained as an input, the number and locations of the WESS units that maximize the net benefit is determined for an entire rail line. The energy recovery methods used comprise optimal coasting, regenerative braking, and positioning of the energy storage devices to achieve maximum receptivity. Coasting saves energy by maintaining motion with propulsion disabled, but this increases the total travel time. Regenerative braking converts the kinetic energy of the train into electrical energy for the powering of subsequent acceleration cycles and although it does not affect travel time, it reduces the time available for coasting, indicative of a tradeoff. The study entails the design of a model that simulates the movement of the train over an existing alignment section while considering alignment topography, speed limits, and train schedule. Since on-time performance is the priority of railroad operations, the simulator instructs the driver to operate according to several motion regimes to optimize the energy consumption while maintaining schedule. The model consists of several time-varying inputs which add increased levels of complexity to the problem. This, in addition to its combinatorial nature, necessitates a heuristic algorithm to solve it, because traditional analytical solution methods are deficient. The optimization problem is solved by applying Genetic Algorithms (GA) because of their ability to search for a global solution in a complex multi-dimensional space. This strategy adds sustainability and reduces the carbon footprint of the operator. A case study is conducted on a single segment of a commuter rail line and yields a 34% energy reduction. The case study is extended to an entire line with multiple segments where the aim is to optimize the locations of wayside energy storage devices (WESS) for maximum economic benefit. It was found that out of the 10 alignment segments in the study, a maximized benefit of over $600,000 was achieved with WESS units installed on only three of those segments. The methods derived in this study can be used to generate speed profiles for planning purposes, to assist in recovery from service disruptions, to plan for infrastructural upgrades related to energy harvesting or to assist in the development of Driver Advisory Systems (DAS)

    Flywheel Energy Storage Systems for Rail

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    In current non-electrified rail systems there is a significant loss of energy during vehicle braking. The aim of this research has been to investigate the potential benefits of introducing onboard regenerative braking systems to rail vehicles. An overview of energy saving measures proposed within the rail industry is presented along with a review of different energy storage devices and systems developed for both rail and automotive applications. Advanced flywheels have been identified as a candidate energy storage device for rail applications, combining high specific power and energy. In order to assess the potential benefits of energy storage systems in rail vehicles, a computational model of a conventional regional diesel train has been developed. This has been used to define a base level of vehicle performance, and to investigate the effects of energy efficient control strategies focussing on the application of coasting prior to braking. The impact of these measures on both the requirements of an energy storage system and the potential benefits of a hybrid train have been assessed. A detailed study of a range of existing and novel mechanical flywheel transmissions has been performed. The interaction between the flywheel, transmission and vehicle is investigated using a novel application-independent analysis method which has been developed to characterise and compare the performance of different systems. The results of this analysis produce general ‘design tools’ for each flywheel transmission configuration, allowing appropriate system configurations and parameters to be identified for a particular application. More detailed computational models of the best performing systems have been developed and integrated with the conventional regional diesel train model. The performance of proposed flywheel hybrid regional trains has been assessed using realistic component losses and journey profiles, and the fuel saving relative to a conventional train quantified for a range of energy storage capacities and power-train control strategies

    Energy storage systems to exploit regenerative braking in DC railway systems: Different approaches to improve efficiency of modern high-speed trains

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    The growing attention to environmental sustainability of transport systems made necessary to investigate the possibility of energy optimization even in sectors typically characterised by an already high level of sustainability, as in particular the railway system. One of the most promising opportunity is the optimization of the braking energy recovery, which has been already considered in tramway systems, while it is traditionally overlooked for high-speed railway systems. In this research work, the authors have developed two simulation models able to reproduce the behavior of high-speed trains when entering in a railway node, and to analyze the impact of regenerative braking in DC railway systems, including usage of energy storage systems. These models, developed respectively in the Matlab-Simscape environment and in the open source Modelica language, have been experimentally validated considering an Italian high-speed train. After validation, the authors have performed a feasibility analysis considering the use of stationary and on-board storage systems, also by taking into account capital costs of the investment and annual energy saving, to evaluate cost-effectiveness of the different solutions. The analysis has shown the possibility to improve the efficiency of high-speed railway systems, by improving braking energy recovery through the installation of such storage systems

    Energy Storage for High Speed Trains: Economical and Energy Saving Evaluation

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    Increasing the utilization rate of regenerative braking energy in rail systems is one of the ongoing applications increasing in significance in recent years. In rail systems, braking is made with two ways, mechanical and electrical. While the energy released due to mechanical braking cannot be recovered, the energy released due to electrical braking can be reused as regenerative braking energy. This regenerative braking energy varies according to the dynamics of the system and it can be given back to the grid, stored in storage devices or burned in resistors (it is not desired). This study develops a novelty algorithm within the scope of this objective and provides the calculation of the regenerative braking energy recovery rate and then making a decision for storage or back to grid of this energy. Afterwards, the regenerative braking energy was calculated with the help of this algorithm for Eskisehir-Ankara and Ankara-Eskisehir trips in two different passengers (load) scenarios, using the YHT 65000 high-speed train, which was chosen as a case study. Then, with a decision maker added to this classical regenerative braking energy algorithm, it will be decided whether this energy will be stored or forward back into the grid for the purpose of providing non-harmonic energy to the grid

    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

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    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

    Feasibility study of a diesel-powered hybrid DMU

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    Nowadays the interest in hybrid vehicles is constantly increasing, not only in the automotive sector, but also in other transportation systems, to reduce pollution and emissions and to improve the overall efficiency of the vehicles. Although railway vehicles are typically the most eco-friendly transportation system, since commonly their primary energy source is electricity, they can still gain benefits from hybrid technologies, as many lines worldwide are not electrified. In fact, hybrid solutions allow ICE-powered railway vehicles, such as diesel multiple units (DMU), to operate in full-electric mode even when the track lacks electrification. The possibility to switch to full electric mode is of paramount importance when the vehicle runs on urban or underground track sections, where low or zero emission levels are required. The paper describes the feasibility study of hybridization of an existing DMU vehicle, designed by Blue Engineering S.r.l., running on the Aosta-Torino Italian railway line, which includes a non-electrified urban track section and an electrified underground section. The hybridization is obtained by replacing one of the diesel generators installed on the original vehicle with a battery pack, which ensures the vehicle to operate in full-electric mode to complete its mission profile. The hybridization is also exploited to implement a regenerative braking strategy, which allows an increase in the energetical efficiency of the vehicle up to 18%. The paper shows the sizing of the battery pack based on dynamic simulations performed on the Turin underground track section, and the results demonstrate the feasibility of the hybridization process
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