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Energy savings in public transport
Abstract
Growing pollution levels and traffic congestion in major cities are becoming delicate issues that could be eased by more efficient public transportation systems. To reduce emissions, electric powered vehicles are in use in many cities. Depending on the number of commuters and on the available infrastructure, different types of electric vehicles (battery electric buses, trolley buses, trams, metro, light rail) can be applied. Although these mass transit vehicles enable large reductions in terms of emissions, their energy efficiency could be significantly improved. This improvement can be reached by the hybridization of their drive train with the inclusion of an energy storage system (ESS) for energy recovery purposes [1], [2]. Recent studies have shown that up to 40% of the energy supplied to electrical rail guided current, and power losses, a model of the tram, network, and substations power flow has been developed in a Matlab/ Simulink environment. Results obtained in energy savings at substation level vary from 24iquest27.6% under the same driving profile and auxiliaries load, while at the endof- life (EoL) of supercapacitors, the range varies from 18.1 - 25.1%, depending on the super capacitor module used and the vehicle load.
... As for on-board energy storage, savings are reported at 24% [39] and 18.6-35.6% [40]. These values refer to real-world data and account for phenomena that cannot be properly modelled. ...
... Chymera et al. showed that more than 50% of the energy dissipated in a transit system comes from braking [30], which also sets a limit on the energy that can be recovered through energy storage. The authors of [40] conduct a similar study to ours on a Brazilian route, calculating a theoretical 23.87% energy savings; when introducing the optimal size storage, an energy savings of 15.67% is achieved. [31] shows how coupling a flywheel in a slug car can reduce fuel consumption and NOx emissions by recovering the braking energy; gas emission reduction is another factor to take into account when dealing with ICE locomotives. ...
In this paper, we looked at the role of electromechanical storage in railway applications. A mathematical model of a running train was interfaced with real products on the electromechanical storage market supposed to be installed at the substation. Through this simulation, we gathered data on the recoverable energy of the system, its advantages, and its limitations. Various storage powers were run along variations in speed and gradient to paint a clearer picture of this application. Throughout these simulations, the energy savings were between 25% and 38%, saving up to 0.042 kWh/(seat km).
... For this reason, DC traction system are used intensively in dense urban area due to their high performances and low polluting emissions. Currently, new solutions are more and more studied and developed to further improve the overall efficiency [2]. For example, on-board or wayside energy storage systems [3]- [7] (ESS) or reversible Traction Power Substations (TPS) [6]- [8] can be used to save braking energy. ...
... The braking coefficient kov decreases linearly from Uov-min to Uov-max. The brake is represented by a current source, which imposes the current ibk (2). As a static model of the input filter (inductor and DC bus) is used [18], the train current it is calculated by (3). ...
... Given the advantages of high-transport capacity, punctuality, short isolation distance, and environmental aspects, electric DC railway transportation is a preferred solution in an urban area. However, global warming and the increase in the cost of energy lead to the need to further improve the overall efficiency [1]. Indeed, cost and energy optimisations are more and more expected in the transport sector to reduce its ecological footprint and make its economical aspect more resilient [2]. ...
... T1) is represented by a current source i tot−1 , a coupling element representing the parallel connection on the DC bus with the rheostatic brake (13), and an accumulation element representing the DC bus, which imposes the voltage u f−1 on the DCTN. The brake current i bk−1 is imposed by the braking management strategy (1). The interactions with the DCTN are the voltages u f of the DC buses and the currents i t of the trains. ...
Simulation tools are crucial to efficiently design the infrastructures and operations of DC electrical railway systems, including potential innovative technologies such as reversible traction power substations and energy storage systems. For this purpose, it is essential to accurately estimate the evolution of the voltage and power flows within the DC traction network, with fast computation time. This study, therefore, proposes a new simulation approach for fast and accurate voltage estimation and power flow analysis of DC railway systems. It is based on the use of non‐linear switched models for traction power substations and trains. The modified nodal analysis is extended to consider such models, including the voltage drop control of the different subsystems, avoiding the necessity to use complex numerical iterative solvers. This new approach is validated and compared to an existing dynamical model and a conventional static model. The comparisons prove the relevance of the new approach, which provides validated and accurate results (<2% error compared to the validated dynamical model) with fast computation time (speed up of 500 compared to the dynamical model). It can, therefore, be used to study, design, size, and optimise DC traction systems with new technologies aimed at saving braking energy.
... E LECTRIC vehicles (EVs) have been extensively seen as a favorable option to the conventional combustion engine vehicles [1], [2]. They have advantages such as energy-efficient, environmentally beneficial, silent, and their use decreases oil dependence [3], [4]. Meantime, due to some drawbacks, consumers Manuscript are still not attracted to using EVs. ...
... Having the resistance forces (R x and D A ), it is possible to obtain the total requested torque (T req ) [Nm] in function also of the external radius (r) [m] and the vehicle required acceleration (ẍ req ) [m/s 2 ], as shown in Eq. (3). ...
The hybrid energy storage system (HESS), which is composed of battery and ultracapacitor, is established to enhance the performance of an electric vehicle (EV). Moreover, several studies highlight the gains of split the traction power demand among electric motors (EMs) with different characteristics and drivetrain configurations, allowing these to operate at higher efficiency. In this paper, we unite the advantages of the multi EM drive train with the HESS power split and propose a novel two HESS system, in which each HESS is in charge of one of the drivetrain configurations (front and rear system). The EV is driven by two in-wheel EM at the front wheels and a single EM assembled with a differential transmission that moves the rear wheels. In this paper, a multiobjective optimization, based on a genetic algorithm (GA), is formulated to minimize the HESS sizing and maximize the driving range of the vehicle. Also employing the fuzzy control, this strategy is responsible to split the power between the front and rear wheels systems in a more reasonable way to satisfy the demands of better performance. The complete strategy has been developed under the FTP-75 (urban), HWFET (highway) and the US06 (high speed and required acceleration) driving cycles using the MATLAB/Simulink software environment. As compared to a similar EV with a single HESS system, the proposed dual-HESS configuration was able to improve the driving range in 145.15 km also decreasing 23.93% of the HESS mass.
... On the other hand, the installation of onboard devices introduces additional weight, requiring careful sizing analyses [5]. Nevertheless, several works in the reference literature have carried out theoretical analyses revealing energy-saving rates ranging from 16% to 35.8% [6], [7]. ...
... How to maintain passenger safety in public transport, whereas companies suffer financially? This is a balanced equation that should be achieved, it is the responsibility of the companies, the stakeholders, and transport sectors to assess the risk management tools and to conduct the essential cost-effective analysis, such assessment will make the mobility system more effective, because public transit sector caused enormous socioeconomic and environmental problems that can be avoided [15]. To explore the impacts of COVID-19 on people movements, some interviews were made with young adults in Melbourne and Victoria, Australia. ...
... Characterized by their very high power density, high dynamic response and low energy density, supercapacitors are most often used when high power peaks are required for very short periods. Supercapacitors are very suitable for applications where high power peaks are frequent [32], [33]. They are usually used in urban rail transit of all types [34]- [36]. ...
Governments have recently been dedicating relevant funds to cope up with the inevitable transition to sustainable mobility aiming for a greener transportation sector. This scenario is backed up by the deteriorating global energy crisis which is predicted to hasten the transition to sustainable energy. Focus has been given to railway systems being globally considered as a tractor project for promoting the use of green and renewable energy by helping build the required infrastructure. As a result, a high tendency for integrating onboard energy storage systems in trains is being observed worldwide. This paper provides a detailed review of onboard railway systems with energy storage devices. In-service trains as well as relevant prototypes are presented and their characteristics are analyzed. A comprehensive study of the traction system structure of these vehicles is introduced providing an overview of all converter architectures used, categorized based on the type of onboard energy storage device on the train. The current situation of hydrogen fuel cells in railway systems is presented as well, highlighting consistent tendencies. The paper also provides a glimpse into commercial battery and fuel cell products used on operating trains.
... Nowadays, EVs are becoming a feasible option for the traditional combustion engine vehicles (De Keyser et al., 2017;Zhang et al., 2018). There are some benefits with these EVs like silent, being energy efficient, reduces oil dependency and environmentally beneficial (Barrero et al., 2008;Abdelsalam and El-Shorbagy, 2018). Meanwhile, customers are not interested in using these EVs because of some limitations. ...
... E NERGY saving is a critical issue for the next decade. New transportation systems aim to increase mobility while limiting environmental impacts [1], [2]. Electrified vehicles have, thus, been developed to replace thermal cars. ...
... Public transport (PT) is beneficial for many aspects of urban systems. It provides benefits such as congestion mitigation (Nguyen-Phuoc, Young, Currie, & De Gruyter, 2020), air pollution reduction (Borck, 2019), and energy savings (Barrero, Van Mierlo, & Tackoen, 2008). The built environment and travel time are considered to be the two critical categories of factors that influence people's preferences for PT travel (Liao, Gil, Pereira, Yeh, & Verendel, 2020). ...
Understanding human perceptions of public transport (PT) travel is essential for improving PT provision/operation and the travel experiences of PT users, as well as for encouraging more people to use green and sustainable travel to reduce the congestion, air pollution, and energy costs that many urban systems are facing. Based on behavioral experiments and surveys, existing research has revealed that the spatial and temporal characteristics of PT travel greatly influence human perceptions; however, neuroimaging evidence confirming these findings remains lacking. In this study, we conducted a functional magnetic resonance imaging- (fMRI-) based PT travel and recall experiment with 9 participants and collected 651 unique bus travel trajectories in Beijing City over 21 days. We extracted 22 spatial and temporal characteristics and derived brain activity patterns for each PT travel route. A representational similarity analysis (RSA) was performed to quantify the relationship between these spatial and temporal characteristics and brain activity patterns. Verbal descriptions were collected to cross-check the brain imaging results. We show that the participants' brain activity patterns were significantly correlated with seven spatial (i.e., circuity, turn, angular deviation, slope, point of interest (POI), and land use) and two temporal (i.e., travel time and waiting time) features, although individuals' perceptions of PT travel differed substantially. These findings are in line with the participants' verbal reports. Our findings offer new neuroimaging evidence from an interdisciplinary perspective on the perception of the spatial and temporal characteristics of PT travel, which not only lays an empirical basis but also provides a “neurourbanism” approach to improve travelers' subjective well-being during PT travel.
... Since most of the topologies and EMSs are simulated using acquired working condition data or by direct measuring data during the functioning of the HESS, it strongly depends on the vehicle type and its operating conditions, for instance, urban buses where HESSs provide a significant amount of quickly delivered power optimal for accelerating, braking, and motor-starting processes for each route stop [66], trams where HESSs must support bursts of energy supply in each substation where they charge in a short period of time [67], and electric cars where customers need better prices and driving ranges [33]. ...
The current worldwide energy directives are oriented toward reducing energy consumption and lowering greenhouse gas emissions. The exponential increase in the production of electrified vehicles in the last decade are an important part of meeting global goals on the climate change. However, while no greenhouse gas emissions directly come from the operations of the electrical vehicles, the electrical vehicle production process results in much higher energy consumption and greenhouse gas emissions than in the case of a classical internal combustion vehicle; thus, to reduce the environment impact of electrified vehicles, they should be used for as long as possible. Using only batteries for electric vehicles can lead to a shorter battery life for certain applications, such as in the case of those with many stops and starts but not only in these cases. To increase the lifespan of the batteries, couplings between the batteries and the supercapacitors for the new electrical vehicles in the form of the hybrid energy storage systems seems to be the most appropriate way. For this, there are four different types of converters, including rectifiers, inverters, AC-AC converters, and DC-DC converters. For a hybrid energy storage system to operate consistently, effectively, and safely, an appropriate realistic controller technique must be used; at the moment, a few techniques are being used on the market.
... Due to the reduction of global fossil fuel storage, the application of electric vehicles (EVs) in many countries is getting more and more attention, compared with vehicles using internal combustion engines, EVs have the advantages of no emissions, high efficiency and high economy [1,2]. However, as the main energy source of EVs, the battery is facing several challenges and barriers, such as the size, performance, and durability, especially its available capacity will be reduced due to the heating effect caused by the high charging/discharging currents [3,4]. ...
To solve the problem of battery capacity degradation caused by high current magnitudes and frequent current variations in electric vehicles (EVs), a hybrid energy storage system (HESS) incorporating high energy density storage (battery) and high power density storage (ultracapacitor) is proposed. The HESS contains a multi‐port DC‐DC converter, which controls the energy flow among the battery pack, the ultracapacitor (UC) pack, and the port of output. Considering the state of charge (SOC) of UC, the speed, and demand power of EV, an energy management strategy (EMS) based on fuzzy logic control (FLC) for the HESS is proposed in this paper. According to the strategy, the battery pack serves as a base power source while the UC pack serves as a transient power source so as to smooth the battery pack current and prolong the battery life. Simulation and experiment results illustrate the effectiveness of the proposed strategy for UC/battery HESS in EVs. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.
... Issues related to electromobility in public transport systems and the improvement of the operational efficiency of public transport are currently of interest to many scientists and engineers [1][2][3][4][5][6]. This coincides with the development of devices ensuring passenger comfort, greater passenger comfort expectations and the intensive advancement of technologies involved in the production of traction batteries [7,8], supercapacitors [9][10][11][12], combustion generators and other energy sources [9,13,14]. ...
When a trolleybus travels through insulated sections of the overhead contact line, it experiences momentary power interruptions, which adversely affect the vehicle’s on-board auxiliary subassemblies. To reduce these negative effects, one can harness energy recovered via regenerative braking. A model power supply circuit diagram for structural systems of the trolleybus is proposed. Simulation tests were carried out to develop a method for analyzing power supply to trolleybus auxiliary devices and verify it in a real-life example. The results allow determination of the limit power that can be generated by the trolleybus drive system to feed auxiliary devices during interruptions in power supply from the overhead contact line. The possibility of powering the on-board auxiliary equipment of a trolleybus using energy from recuperation with a traction motor is presented.
... Ordody observed the properties of the existing ventilation system in the Budapest subway and proposed a new economic primary ventilation system considering the technical requirements [|11]. Baerro et al. investigated the use of energy storage systems super capacitors in terms of energy savings and stated that these systems provide about 18 -25% efficiency [12]. Meinert investigated the effects of hybrid energy storage units, and these units provided that energy stored up to 2.5 km and saved up to 10.8% [13]. ...
Today, reducing the energy consumption of rail systems is one of the issues that attract researchers' attention. There are many methods to reduce energy consumption and coasting control method has been used in this study. The driving modelling of the vehicle has been carried out by considering all parameters. A new objective function has been determined and for optimization, genetic algorithm (GA) and artificial bee colony (ABC) algorithm have been preferred. The study has been tested with the data of Ankaray metro line. When the proposed optimized driving has been compared with practical driving of the vehicle, the energy savings rate is 13.79% in GA and 13.45% in ABC for a driving. Despite these significant savings ratios, the increase in travel time has been calculated at 1.7% in GA and 1.55% in ABC. When the obtained savings rates are considered annually, this study may greatly contribute to sustainable life.
... Energy consumption is a very important aspect linked to the decline in public transport in cities. Increasing levels of pollution, congestion on the roads and energy consumption in cities are becoming sensitive issues that could be mitigated by more efficient public transport systems and an increased share of urban travel by public transport [67]. The epidemic threat has reduced the share of public transport travel, and this reduction occurred drastically during national lockdowns. ...
Pandemics have presented new challenges for public transport organisers and operators. New diseases (e.g., influenza H1N1, severe acute respiratory syndrome—SARS, as well as, more recently, SARS-CoV-2) increase the need for new protection measures to prevent epidemic outbreaks in public transport infrastructure. The authors’ goal is to present a set of actions in the area of public transport that are adjusted to different levels of epidemic development. The goal goes back to the following question: how can the highest possible level of passenger safety be ensured and the losses suffered by urban public transport companies kept as low as possible? The sets of pro-active measures for selected epidemic scenarios presented in the article may offer support to local authorities and public transport operators. In the next steps, it is important to develop and implement tools for public transport management to ensure safety and tackle epidemic hazards.
... Surplus energy in braking phases recovered by the installation of onboard or wayside energy storage systems with designing controllers to control charge/discharge process of SCESS suitable for operation characteristic of train. Studies, applications of super capacitor energy storage system with tested to practical utilization (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) . Iannuzzi et al (5) using onboard SCESS integrated with traction drive system saves energy to 38%, reducing peak power up to 50% in accelerating regime, stabilizing voltage on DC bus to 1%, increasing power supply distance among traction substations ; Dominguez et al released a study of energy consumption reduction to 24% in the Metro de Madrid (7) ; Michael Steiner et al (8) shows Bombardier installed Mitrac energy saver being able to reduce the consumption of the traction energy to 30% and line current peak and voltage drop by 50% ; Diego Iannuzzi, Flavio Ciccarelli, Davide Lauria (12) use stationary ultra-capacitor storage device for improving energy saving and voltage profile of light transportation networks; reversible substations (17,18) ; maximizing the regenerative energy exchange between trains by synchronizing their accelerating and braking phases as much as possible (19)(20)(21) , Fathy Ahmed et al. (22) applied parasitism-predation algorithm (PPA) in the energy management strategy for hybrid photovoltaic/fuel cell/battery/supercapacitor to minimize the hydrogen consumption of fuel cell; Jamadar Najimudin et al (23) developed regenerative braking system (RBS) and braking energy management techniques, considering different driving situations and road conditions which employed in addition to mechanical braking for increasing the braking efficiency of the electric vehicle system. ...
... 46 Three types of OESDs are commonly utilized in electri-47 fied railway systems, namely supercapacitors, flywheels, and 48 electrochemical batteries. Supercapacitors are widely utilized 49 as the OESD, for example, many urban rail transit systems 50 have been equipped with them, such as tramlines [6] and 51 metro lines [7] in Brussels, Madrid metro line [8], Blackpool 52 tramway [9], Mannheim tramway [10], and Paris tram line 53 [11]. For the flywheel, early in 1988, it has been proposed as 54 an OESD for trains to avoid regenerative braking cancellation 55 and to compensate for voltage drops. ...
With the rapid progress in railway electrification and energy storage technologies, on-board energy storage devices (OESDs) have been widely utilized in modern railway systems to reduce energy consumption. This paper aims to develop the optimal driving strategy of electric trains with three popular types of energy storage devices, namely supercapacitors, flywheels and Li-ion batteries, as the OESD to minimize the net energy consumption. With the given OESD investment cost, the dynamic power limits of different types of OESDs are fully considered to optimize the dynamic discharge/charge behavior of the OESD in the train operation. The case studies investigate the train operation on fully electrified railways, discontinuously electrified railways and catenary-free railways, showing that the optimal eco-driving strategy of the train and discharge/charge behavior of the OESD are significantly different for different type of OESDs. The obtained train speed, OESDs’ state of energy (SOE), power profiles and energy-saving potential for each type of OESDs under various scenarios are compared comprehensively, and the results also reveal that the flywheel has the best performance for its energy-saving rate ranging from 0.15 %/k while Li-ion battery is observed with the weakest performance with energy-saving rate being only 0.01 %/k. The error rate analysis also confirms a satisfactory modeling accuracy of the proposed method.
... Most of these research studies estimate a reduction in total energy consumption around 12-35% when using SC. Simulation results reported in the literature show reduction of 33% for a metro line in Brussels [38], 24% for a metro line in Madrid [39], 25% for a tramway in Mannheim [40], or 30% for a Blackpool tramway [41] are reported in the literature. The research presented in [21], oriented to freight trains, shows that using a storage unit to enable regenerative braking reduces up to 25% of the total energy. ...
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.
... Microgrids are considered innovative solutions to be used also in transportation systems to integrate the advantages of energy storage utilization [13][14][15][169][170][171]. Indeed, they can help to reach the target of increasing energy saving [172] and the capability to compensate strong perturbations [173]. In urban railways, the power consumption is very high, therefore the optimization of energy consumption in this field means a great contribution for energy efficiency, specially when dealing with braking energy recovery. ...
Microgrids are a very good solution for current problems raised by the constant growth of load demand and high penetration of renewable energy sources, that results in grid modernization through “Smart-Grids” concept. The impact of distributed energy sources based on power electronics is an important concern for power systems, where natural frequency regulation for the system is hindered because of inertia reduction. In this context, Direct Current (DC) grids are considered a relevant solution, since the DC nature of power electronic devices bring technological and economical advantages compared to Alternative Current (AC). The thesis proposes the design and control of a hybrid AC/DC Microgrid to integrate different renewable sources, including solar power and braking energy recovery from trains, to energy storage systems as batteries and supercapacitors and to loads like electric vehicles or another grids (either AC or DC), for reliable operation and stability. The stabilization of the Microgrid buses’ voltages and the provision of ancillary services is assured by the proposed control strategy, where a rigorous stability study is made. A low-level distributed nonlinear controller, based on “System-of-Systems” approach is developed for proper operation of the whole Microgrid. A supercapacitor is applied to deal with transients, balancing the DC bus of the Microgrid and absorbing the energy injected by intermittent and possibly strong energy sources as energy recovery from the braking of trains and subways, while the battery realizes the power flow in long term. Dynamical feedback control based on singular perturbation analysis is developed for supercapacitor and train. A Lyapunov function is built considering the interconnected devices of the Microgrid to ensure the stability of the whole system. Simulations highlight the performance of the proposed control with parametric robustness tests and a comparison with traditional linear controller. The Virtual Synchronous Machine (VSM) approach is implemented in the Microgrid for power sharing and frequency stability improvement. An adaptive virtual inertia is proposed, then the inertia constant becomes a system’s state variable that can be designed to improve frequency stability and inertial support, where stability analysis is carried out. Therefore, the VSM is the link between DC and AC side of the Microgrid, regarding the available power in DC grid, applied for ancillary services in the AC Microgrid. Simulation results show the effectiveness of the proposed adaptive inertia, where a comparison with droop and standard control techniques is conducted.
... The problems of energy efficiency and energy saving have been extremely topical lately. So, implementing various systems and devices whose function is not only saving energy, but also generating a certain amount of energy for further use is one of the ways to solve them [1]- [3]. Transport (with its infrastructure) apparently faces the urgency of implementing energy-efficient and energysaving technologies more than any other sector of economy. ...
... This scenario is particularly favorable for the use of regenerative braking systems and, since the lines are usually shorter than conventional railway lines, it is also possible to easily implement innovative customized solutions. For these reasons, the application of energy recovery systems in tramways and light railways has been widely analyzed [10][11][12], considering various energy storage systems locations [13,14], different applications and usage [15][16][17][18], and different storage technologies [19]. Energy recovery in high speed railway systems is still an open field of research and the possibility to obtain significant savings is remarkable. ...
... If there is no train in traction and no load on the system to absorb this regenerative energy, the voltage of the DC catenary increases [14]. To overcome this problem, some strategies can either be involved: to optimize the train's operations [16,30] (optimization timetables, efficient energy based driving) or to address an updating of the railway power network by integrating new hardware equipment such as energy storage [6]. Train timetable optimization has been suggested as one of the approaches to increase the recuperation ratio of the regenerative braking energy. ...
To face environmental issues, SNCF, the French railway, has chosen to improve the energy efficiency of its electrical power system by investigating solutions for regenerative braking. With the contribution of Railenium, a research and test center in railway activities, they aim to recover the braking energy by setting up a reversible inverter in the DC substation ”Masséna”. The issue is to test, implement and compare various control solutions to increase the energy efficiency with minimum impacts on the railway operation. In this paper, a simulation model for studying a reversible power substation is addressed by considering AC and DC equivalent electrical sources. The proposed model provides a reliable tool for analyzing the behavior of the railway electrical network during specially braking mode. In order to validate this model, its simulation results are compared with the ones obtained from Esmeralda, the SNCF professional software. A first configuration is led without the inverter and gives certified Esmeralda results and validates the proposed model despite some gaps in powers and voltages due to differences in input data and models. A second comparison with inverter is presented to highlight the main difference between the proposed model and Esmeralda. In addition, laboratory experimental activities are put forward to investigate the proposed model by using power-hardware-in-the-loop simulations. Finally, a simulation test under MATLAB software with fifty train’s traffic is presented to estimate the energy saving thanks to the installed inverter. For this latter case study, the system sent back to the national AC grid around 6.9% of the total energy consumed by all trains.
... Many urban rail transit systems have been equipped with supercapacitors, such as Brussels tram line, Brussels metro line, Madrid metro line, Blackpool tramway, Mannheim tramway and Paris tram line. The energy saving rate by using supercapacitors ranges from 16% to 35.8% in theoretical assessments [4]- [9]. Electrochemical batteries, such as lead-acid batteries, Ni-Cd batteries, NiMH batteries, Li-ion batteries and so on, are with relatively high energy density leading to large energy-storage capability [1]. ...
For improving the energy efficiency of railway systems, on-board energy storage devices (OESDs) have been applied to assist the traction and recover the regenerative energy. This paper aims to address the optimal sizing problem of OESDs to minimize the catenary energy consumption for practical train operations. By employing a mixed integer linear programming (MILP) model based on energy flow and the law of conservation of energy, three types of widely used OESD: supercapacitors, Li-ion batteries and flywheels have been studied in a real-world case of Beijing Changping line. Results show that without the constraints of capital cost and volume, the supercapacitor, Li-ion battery and flywheel with optimized capacity can save the catenary energy consumption by 23.6%, 22.9% and 23.7% compared to the cases without OESDs respectively. The minimum catenary energy consumption for each type of OESD has also been found with the constraints of capital cost and volume. The study shows that with a volume constraint less than 0.6 m3 and a higher allowed capital cost more than 20 k$, flywheel tends to achieve the least catenary energy consumption. When the volume is relaxed to go beyond 0.6 m3, supercapacitors always achieve the minimum catenary energy consumption disregarding the constraint of capital cost.
... Many urban rail transit systems have been equipped with supercapacitors, such as Brussels tram line, Brussels metro line, Madrid metro line, Blackpool tramway, Mannheim tramway and Paris tram line. The energy saving rate by using supercapacitors ranges from 16% to 35.8% in theoretical assessments [4]- [9]. Electrochemical batteries, such as lead-acid batteries, Ni-Cd batteries, NiMH batteries, Li-ion batteries and so on, are with relatively high energy density leading to large energy-storage capability [1]. ...
For improving the energy efficiency of railway systems , on-board energy storage devices (OESDs) have been applied to assist the traction and recover the regenerative energy. This paper aims to address the optimal sizing problem of OESDs to minimize the catenary energy consumption for practical train operations. By employing a mixed integer linear programming (MILP) model based on energy flow and the law of conservation of energy, three types of widely used OESD: supercapacitors, Li-ion batteries and flywheels have been studied in a real-world case of Beijing Changping line. Results show that without the constraints of capital cost and volume, the supercapacitor, Li-ion battery and flywheel with optimized capacity can save the catenary energy consumption by 23.6%, 22.9% and 23.7% compared to the cases without OESDs respectively. The minimum catenary energy consumption for each type of OESD has also been found with the constraints of capital cost and volume. The study shows that with a volume constraint less than 0.6 m 3 and a higher allowed capital cost more than 20 k$, flywheel tends to achieve the least catenary energy consumption. When the volume is relaxed to go beyond 0.6 m 3 , supercapacitors always achieve the minimum catenary energy consumption disregarding the constraint of capital cost.
Index Terms-On-board energy storage device (OESD), optimal sizing, electrified railway systems, mixed integer linear programming (MILP), energy-saving
... Real applications of on-board storage systems are the Brussels, Madrid metro and Mannheim tramway lines. The percentage of energy saving reported in [45][46][47] are 18.6% ÷ 35.8%, 24% and 19.4% ÷ 25.6%, respectively. To reach high integration with motor drive control, some research studies are focused on the optimal design, sizing and control of on board energy storage systems [48][49][50][51][52]. Focuses on stationary storage systems, the real implementation of wayside Energy Storage System (ESS), show an increase in energy savings of up to 30%. ...
The present paper is a review on efficiency issues related to three important sectors of the transportation systems: railways, electrical vehicles, and marine. For the three sectors, the authors, in reference of their knowledge and research area, show the results of a wide literature analysis, in order to highlight which are the measures, in terms of technological solutions and management techniques, which are recently investigated and implemented, for improving the three transportation systems, from the point of view of efficiency. In particular, for the railway transportation sector, a wide analysis is presented, detecting which are the main measures adopted for improving the efficiency, related to the power systems for supplying trains and to the train traffic control, with a focus on the storage system integration. For electric road vehicles the analysis is focused on the plug-in electrical vehicles and on the infrastructure for their recharge, with an emphasis on how these vehicles can support the grid, e.g., through Vehicle to Grid (V2G) applications. Finally, for the marine transport service the review is related to the propulsion systems and on how the different solutions can meet the objective of efficiency.
... It consists of obtaining a way to drive a train on a journey to fulfil a target running time with minimal energy consumption. Eco-driving has the advantage of being a short-term action that requires low investments, while other measures, such as improving the infrastructure [3][4][5][6][7][8][9][10][11][12] or rolling stock [13][14][15][16][17], usually require a significant investment and long/mid-term actions. ...
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.
Regenerated energy has the potential to produce great energy saving figures in railway operation. However, in DC systems, regenerated energy cannot be harnessed completely. The presence of rectifier filters does not allow returning energy from the railway system to the utility grid. Therefore, the regenerated energy that cannot be consumed by other trains instantaneously must be wasted in on-board resistors. Energy storage systems, on-board the train or in the track-side, can be implemented to avoid this situation and maximise regenerated energy usage. The main technologies that have been applied in railways, the modelling of these energy storage systems and its control are discussed in this chapter. Besides, a case study is presented where different scenarios of energy storage and receptivity to regenerated energy are analysed based on the characteristics of a real line of the Madrid Underground. These scenarios allow to evaluate the influence in the energy consumption reduction because of the installation of energy storage devices and the influence in the optimal design of ATO speed profiles. The results indicate that energy storage systems would provide energy savings in scenarios with low density traffic, but low benefits are obtained in dense traffic scenarios where the regenerated energy can be exchanged between trains easily.KeywordsEfficient-drivingEnergy storageATOMulti-objective optimization
Carpooling has become a practical, cheap, and stress-free way to move around. This project presents the requirement, design and implementation of an enterprise-class application for carpooling following Model-View-Controlol model. The added features, compared to available applications, are different kinds of trips, a check-in system, and social media integration. The two kinds of trips are single trips, which are trips between two cities, and frequent trips which are the ones that commuters do every day. The check-in system enables users to check in meetings points and notify all users about that. Users can also share their activities on the application thanks to social media integration. The application is designed to be scalable, extensible, highly available and with a good performance.
Electric trains generally have four modes of operation including acceleration, cruising, coasting, and braking. There are several types of train braking systems, including regenerative braking, resistive braking and air braking. Regenerative braking energy can be effectively recuperated using wayside energy storage, reversible substations, or hybrid storage/reversible substation systems. This chapter compares these recuperation techniques. As an illustrative case study, it investigates their applicability to New York City Transit systems, where most of the regenerative braking energy is currently being wasted. One of the approaches to maximizing reuse of regenerative braking energy is through optimizing train timetables. One of the key solutions for better recuperation of regenerative braking is through an energy storage system. Reversible substations are another technique for recuperating regenerative braking energy. The chapter investigates the impact of installing each of the three wayside energy storage technologies, that is, battery, supercapacitor, and flywheel, for recuperation of regenerative braking energy and peak demand reduction.
The paper describes the measuring systems and methodology for acquiring traction power measurements on the on-board traction systems of two metro trains and three 750 V DC rectifier substations in the Athens Metro Line 2. Being part of a wider investigation to develop a Hybrid Energy Storage System (HESS), the purpose of the present measurements is to provide traction systems experimental and operational data that would assist in the understanding of the dynamic characteristics of train braking regeneration and quantify the available energy that could be stored in a super-capacitors/batteries hybrid storage system for further use, which would otherwise be wasted and consumed as heat in stations and tunnels through the trains' braking resistors. In turn the stored energy could power upon demand selected stationary electrical loads in Metro stations of a non-safety critical character (such as lighting, ventilation, pumps, etc.) leading to very significant energy savings and to a corresponding reduction of greenhouse gases. Preliminary results confirm the feasibility of the energy saving concept indicating a significant potential for the hybrid energy storage devices and subsequent energy re-use of 4000–6000 kWh/day per rectifier substation of otherwise unused train braking energy, with a typical Metro station stationary loads consumption of 2000 kWh/day.
Transit stops serve as crucial components of journeys for riders, but their condition is often left out of equity considerations. Two important empirical questions are what stop amenities, such as places to sit, clear signage, shelters for inclement weather, and unobstructed curbs are present, and how are they distributed across systems, which may reveal neighborhood or route-specific disparities. San Francisco, CA represents an ideal case for which to pursue this question, given it maintains a ‘transit first’ policy directive that mandates public space prioritize transit over private automobiles. An in-person census of 2964 street-level bus stops was conducted over three months, which finds that a majority of stops lack both seating and shelter of any kind, that route signage varies widely in format and legibility, and that roughly one third of all stops are obstructed by on-street parking, rendering them difficult to use and exposing riders to oncoming traffic. Stops in the city’s northern half are more likely to feature seating, shelter, and unobstructed curbs, whereas amenity “coldspots” nearly all lie within the city’s southern half. Stop amenities also vary sharply by bus route, such that routes with the longest headways (and thus waiting times) provide on average the least seating, shelter, and clear curbs. These three amenities – seating, shelter, and unobstructed curbs – are also present to a greater degree in Census tracts with higher shares of white residents. This census demonstrates that equity evaluations of transit must include stop amenities, which are often overlooked, can undermine transit’s attractiveness, and even compound long-standing imbalances in service quality for underserved communities. Furthermore, studies of this kind can inform where amenity upgrades should be prioritized, targeting those areas currently lacking in high-quality stops, and raising the minimum standard of stop amenities overall. Finally, given data collected in this census is almost entirely unavailable to riders within current trip-planning and wayfinding applications, this work raises the possibility of expanding transit-data standards to include amenity details.
Enerji verimliliği çalışmalarında iyileşmenin sürekliliğini sağlamak için Enerji Yönetim Sistemlerinin (EnYS) kurulması ve kullanılması tavsiye edilmektedir. Bu çalışmada, ulaşım sistemleri içerisinde elektrik tüketiminde ağırlıklı bir yere sahip olan ve ülkemizin en büyük kent içi raylı sistemi olan İstanbul kent içi elektrikli raylı ulaşım sistemleri (Metro, Tramvay ve Füniküler hatları) için önerilen EnYS tanıtılmıştır. Ayrıca EnYS kapsamında kurulan ölçme ve izleme sisteminden alınan ölçümlerle hangi verilerin ne şekilde değerlendirilebileceği ile ilgili örnekler sunulmuş, enerji verimliliği çalışmaları için işleyişle ilgili önerilerde bulunulmuştur. Çalışmada, İstanbul kent içi raylı ulaşım sistemlerine ait 6 metro, 3 tramvay, 1 füniküler, 2 teleferik hattı olmak üzere toplam 12 hattın enerji tüketimi incelenmiştir. Trenlerin teşkil ettiği hareketli sistemlerin (CER) toplam tüketimin %55-60’ını oluşturması sebebi ile ana tüketici olduğu, geri kalan tüketimlerin ise yardımcı tesisler olarak anılan istasyonlara ait aydınlatma-priz (%14-16), asansör-yürüyen merdiven (%6-8), havalandırma sistemleri (%6-8), ticari alanlar (%4-6) ile atölyeler (%3-5) ve idari ofislerde (%2-3) tüketildiği tespit edilmiştir. EnYS kapsamında hatların performanslarını belirlemek ve kıyaslamak için Enerji Performans Göstergeleri oluşturulmuş ve enerji verimliliğinde ki iyileşmenin sürekli ve maksimum olması hedeflenmiştir. Hatların CER performansları incelenmiş ve sefer süresi düzenlemesi ile ilk etapta %17’ ye varan oranlarda enerji tasarrufu sağlanabileceği hesaplanmıştır.
This paper proposes a hierarchical optimization energy management strategy (EMS) considering speed profile to explore energy-saving potential and achieve a reasonable power distribution for the hybrid propulsion system of a tramway composed of the catenary, a battery pack and an ultracapacitor pack. For the higher layer, a speed profile is optimized in the space domain through a particle swarm optimization algorithm, which balances energy consumption, running time and passenger comfort. For the lower layer, based on the optimized speed profile, an EMS is designed, using dynamic programming. The boundary range calculation of state variables for the dynamic programming is carried out in advance, based on the working mode analysis to reduce the computation load. In addition, a supervisory controller is developed to achieve reliable real-time control. Finally, to verify the proposed method, real rail line data in China are used as a case study, and the results show that the proposed method offers the better energy and tramway efficiency.
As an intensive travel mode, public transportation is an essential part of a circular economy construction. Scientific decision-making in a PT development plan is a fundamental prerequisite for ensuring its prioritization. In this study, based on the large-scale group decision-making of fuzzy preference relations, we examine PT development decision-making under public participation, to promote the effective use of PT resources. First, we cluster participants in the decision-making process based on the similarity method. Second, based on the clustering, an induced orderly weighting method is used to analyze the decision-making preferences of each sub-group. Finally, the decision-making preferences of each group are prioritized according to an analysis of group heterogeneity. We found that based on the similarity clustering method, when the threshold was set to 0.68, 85 participants were divided into 4 groups, and the demographic characteristics of the sub-groups presented some agglomeration. The four groups paid little attention to improving the quality of PT services. Moreover, the work unit had a significant impact on the decision-making preferences of participants, and public officials paid more attention to society and the government. Group heterogeneity significantly affects decision-making preferences and alternative priorities.
Due to the short distance between urban rail transit stations, a large amount of regenerative electric energy will be generated. Studying how to recuperate regenerative braking energy and control the voltage fluctuation of the traction network within allowable range can result in economic as well as environmental merits, which has important practical significance in alleviating energy shortage at home and abroad. According to the differences in energy process, regenerating energy absorbing modes can be divided as follows: energy-consuming mode, energy-feeding back mode, energy-storing mode. In this comprehensive paper, for the regenerative braking energy recuperation during the train operation, various method and technology have been analyzed. First of all, three methods of storage and utilization of regenerative braking energy are briefly introduced respectively. Then, the advantages and disadvantages of these three methods are summarized. Finally, based on the current research situation, the storage and utilization of regenerative braking energy in urban rail transit is prospected.
Simulation tools are essential to design the infrastructure and plan the trains operations of electrical railway systems. Traditionally, the train model (that estimates the electrical, mechanical and kinematical behaviors of the vehicles) and electrical network model (that estimates the electrical behavior of the energy supply network) are developed separately. Then, they are simulated together to estimate the interactions between both subsystems. The paper objective is to compare different models to highlight the impacts on the interactions between the vehicles and the railway electrical network, which are crucial to have accurate estimations of the system behavior. For this purpose, a new dynamical model, which is based on a systemic approach and a causality analysis, is compared to a conventional static model, which is based on a cartesian approach and a power flow analysis. The dynamical model is accurate and has been experimentally validated but requires a long computational time. The static model is fast to compute and give a good estimation of the energy consumption for conventional railway systems. However, it is not always able to estimate the power flows within the DC network, and especially when all traction power substations are blocked.
Nowadays, one of the strategies that are being applied in DC railway networks to improve energy efficiency is the installation of Reversible Substations or Energy Storage Systems. The assessment of their impact on the network consumption is typically based on simulation. The accuracy of the results provided by the simulations relies on the accuracy of the models used. This paper focuses on the traffic model used in electric railway simulators. A preliminary literature review has shown that, in most cases, the traffic models of electric railway simulators involve too many simplifications that can lead to non-accurate results. This lack of accuracy can have a great impact in the assessment of the infrastructure improvements, reason why a more accurate traffic model is proposed. The proposed traffic model includes different headways, different time shifts at terminal stations, non-constant dwell times, different train speed profiles and a specific module of the traffic regulation system in real time. The energy saving resulting from the installation of a Reversible Substation obtained with both models-the one used in the literature and the one proposed in this paper-has been compared to illustrate the risk of using a too simplified traffic model. The comparison shows that the simplified model used in the literature leads to high overestimations in energy saving.
In addition to energy consumption, DC railway operators must also pay for the demand charge. This term of the electricity bill has not been studied in detail in the literature and penalizes power peaks. The big fluctuations on the power demand which characterize railway systems make the demand charge important for railway operators. This paper studies the impact of the demand charge on DC railway systems and proposes a solution based on Energy Storage Systems (ESSs) to reduce it. An analysis of the main parameters of the ESS regarding the reduction of the demand charge is provided, as well as an explanation of the effects of different control strategies on the system performance. Most of the savings obtained with the installation of ESSs come from the reduction in the energy consumption; nevertheless, the savings coming from the reduction in the demand charge are significant and contribute to the economic viability of the investment.
The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3–5 Wh/kg with a power density of 300–500 W/kg for high efficiency (90–95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1–2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 Ω cm2.Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.
A new feeding concept for electrical transportation systems is presented, based on supercapacitive energy storage. Supercapacitors are new and powerful components for energy storage. Compared with batteries, the amount of energy they can store is low and does not allow a large vehicle autonomy. Because supercapacitors have the property to be re-loadable in a few seconds, a sequential supply system has been developed, considering repetitive feeding at the stops. To solve the problem of the needed high power amount to reach short refill times, a solution is proposed which consists of using an intermediary supercapacitive tank placed at fixed stations, which is refilled between the bus arrivals with a much lower power. In addition to the description of the needed power electronic converters, theoretical and experimental results are presented, defining the controlled profile of the instantaneous power-level, in order to achieve a fast energy transfer between two supercapacitive tanks.
Power variations and energy criteria have been the main motivations for developing regenerative drive converters for elevators. A more performant solution for power-smoothing can be easily found by using a supercapacitor based storage device, connected to the intermediary circuit of a variable speed drive system. In this paper, power and energy considerations are made for the design of the storage tank and regarding the maximum power demand from the feeding network. For the power-conversion circuit, which is necessary to compensate the voltage variations of the supercapacitors by discharging and charging, a high efficiency converter topology is proposed which allows the bidirectional energy flow under soft-commutation conditions, and offers also a good flexibility for the optimal sizing of the supercapacitor voltage level. The typical behaviour of the special converter is given, together with an analyze of the advantages related to the specific application.
Power variations and energy criteria have been the main motivations for developing regenerative drive converters for elevators. A better performing solution for power smoothing can be easily found by using a supercapacitor-based storage device, connected to the intermediary circuit of a variable-speed-drive system. In this paper, power and energy considerations are being accounted for in the design of the storage tank and regarding the maximum power demand from the feeding network. For the power-conversion circuit, which is necessary to compensate the voltage variations of the supercapacitors during charge and discharge, a high-efficiency converter, topology is proposed, which allows the bidirectional energy flow under soft-commutation conditions. Additionally it offers a good flexibility for the optimal sizing of the supercapacitor voltage level. The typical behavior of the special converter is given, together with an analysis of the advantages related to the specific application.
Resulting from Ph.D. research, a vehicle simulation program is proposed and continuously developed, which allows simulation of the behavior of electric, hybrid, fuel cell, and internal combustion vehicles while driving any reference cycle. The goal of the simulation program is to study power flows in the drivetrains of vehicles and the corresponding component losses, as well as to compare different drivetrain topologies. This comparison can be realized for energy consumption and emissions, as well as for performance (acceleration, range, maximum slope, etc.). The core of this program, consisting of a unique iteration algorithm, will be highlighted in this paper. This algorithm not only allows the calculation of the limits of vehicle acceleration in the function of drivetrain component characteristics, but at the same time is able to develop and evaluate the different power-management strategies of hybrid vehicles, combining combustion engines and electric motors. Furthermore, the comprehensive iteration algorithm is demonstrated to be very efficient in handling any type of working limit for all components in different types of drivetrains, which results in an accurate and modular vehicle simulation program with high data flexibility.
A supercapacitive-storage-based substation for the compensation of resistive voltage drops in transportation networks is proposed. It allows to feed as a current source in any voltage conditions of the line. The system has been designed as a compensation substation to be placed at weak points like end-of-line stations, instead of additional feeding substations. A dedicated power-electronic converter with an associated control system for the stabilization of the voltage level at the point of coupling in case of strong perturbations is proposed. Practical results are also presented, which have been recorded from a reduced size prototype.
A new feeding concept for electrical transportation systems is presented, based on supercapacitive energy storage. Supercapacitors are new and powerful components for energy storage. Compared with batteries, the amount of energy they can store is low and does not allow a large vehicle autonomy. Because supercapacitors have the property to be re-loadable in a few seconds, a sequential supply system has been developed, considering repetitive feeding at the stops. To solve the problem of the needed high power amount to reach short refill times, a solution is proposed which consists of using an intermediary supercapacitive tank placed at fixed stations, which is refilled between the bus arrivals with a much lower power . In addition to the description of the needed power electronic converters, theoretical and experimental results are presented, defining the controlled profile of the instantaneous power-level, in order to achieve a fast energy transfer between two supercapacitive tanks.
How to compare the environmental damage caused by vehicles with different fuels and drive trains? This paper describes a methodology to assess the environmental impact of vehicles, using different approaches, and evaluating their benefits and limitations. Rating systems are analysed as tools to compare the environmental impact of vehicles, allowing decision makers to dedicate their financial and non-financial policies and support measures in function of the ecological damage. The paper is based on the "Clean Vehicles" research project, commissioned by the Brussels Capital Region via the BlM-IBGE (Brussels Institute for the Conservation of the Environment) (Van Mierlo et al., 2001). The Vrije Universiteit Brussel (ETEC) and the Université Libre de Bruxelles (CEESE) have jointly carried out the workprogramme. The most important results of this project are illustrated in this paper. First an overview of environmental, economical and technical characteristics of the different alternative fuels and drive trains is given. Afterward the basic principles to identify the environmental impact of cars are described. An outline of the considered emissions and their environmental impact leads to the definition of the calculation method, named Ecoscore. A rather simple and pragmatic approach would be stating that all alternative fuelled vehicles (LPG, CNG. EV, HEV. etc.) can be considered as 'clean'. Another basic approach is considering as 'clean' all vehicles satisfying a stringent emission regulation like EURO IV or EEV. Such approaches however don't tell anything about the real environmental damage of the vehicles. In the paper we describe "how should the environmental impact of vehicles be defined?", including parameters affecting the emissions of vehicles and their influence on human beings and on the environment and "how could it be defined ?", taking into account the availability of accurate and reliable data. We take into account different damages (acid rain, photochemical air pollution, global warming, noise, etc.) and their impacts on several receptors like human beings (e.g.: cancer, respiratory diseases, etc), ecosystems, or buildings. The presented methodology is based on a kind of Life Cycle Assessment (LCA) in which the contribution of all emissions to a certain damage are considered (e.g. using Exposure-Response damage function). The emissions will include oil extraction, transportation refinery, electricity production, distribution, (Well-to-Wheel approach), as well as the emission due to the production, use and dismantling of the vehicle (Cradle-to-Grave approach). The different damages will be normalized to be able to make a comparison. Hence a reference value (determined by the reference vehicle chosen) will be defined as a target value (the normalized value will thus measure a kind of Distance to Target). The contribution of the different normalized damages to a single value "EcoScore" will be based on a panel weighting method. Some examples of the calculation of the Ecoscore for different alternative fuels and drive trains will be calculated as an illustration of the methodology.
This article will propose different energy storage systems, ranging from 0.91 kWh to 1.56 kWh, suitable for a 30 m long tram. To configure the system regarding energy content, voltage variation, maximum current and power losses, a model of the tram, network and substations power flow has been developed in a Matlab/Simulink environment. Results obtained in energy savings at substation level vary from 24% to 27,6% under the same driving profile and auxiliaries load; while at the end-of-life of supercapacitors, the range varies from 18,1% to 25,1% depending on the supercapacitor module used and vehicle load.
This article gives an overview of the various possibilities of increased energy efficiency in electrical railway systems. Not only the power systems in the main traction circuit are emphasized, but also efficient solutions arising from auxiliary-optimization, reduced weight of the vehicles, aerodynamics and efficient rail automation. The main focus is on the application of energy storage in traction systems. The stationary installation in substations is described and the advantages demonstrated in a number of applications using different main strategies. A wide and varied range of benefits arise from the typical application situation
The proposed energy storage on board of a railway vehicle leads to a big step in the reduction of consumed energy. Up to 30% energy saving are measured in a prototype light rail vehicle, at the same time reducing the peak power demand drastically. Additionally, operation without catenary for several hundred meters was successfully demonstrated with the prototype light rail vehicle driving with switched off pantograph. This prototype vehicle is in passenger operation since September 2003, the implemented software is optimized on energy savings. About two years experience is available and the results are convincing. Applying the energy storage to diesel-electrical multiple units leads to fuel savings and provides a "booster" effect on the acceleration performance. The stored energy is adding additional power on top of the diesel engine power during acceleration. Compared to original diesel power, this additional power can be provided with a relatively low additional weight. Finally, the energy savings of up to 30% and the corresponding emission reduction will already fulfill the targets of various local and global energy saving programs set up by e.g. European Union and big railway operators
An efficient energy storage medium is essential in all hybrid electric vehicles. The advances in double layer electrolytic capacitor technology have opened new areas to complement batteries as a storage medium. In this paper we will review some of the present applications of ultracapacitors as well as to provide guidelines for sizing ultracapacitors for minimal mass in hybrid electric vehicles. Equations for both constant current as well as constant power discharge are discussed. An iterative method for determining the minimum number of ultracapacitor cells is introduced. The effects of ultracapacitor sizing on the rating of interface power electronics are examined.
The development of Hybrid Electric Vehicles is one of the most effective solutions to improve our environment. For the purposes of improving the characteristic and efficiency of Hybrid Electric Vehicles, different hybrid drive train topologies with super capacitor based energy storages have been studied with concern about energy sources control and management. The methods of controlling mean power and controlling peak power according to the load current have been presented in this paper. The experimental results proved that the super capacitor based energy storage is fully controlled by using our strategy of control and management, and that the main power supply system (even without mean power control) is controlled to only supply the mean power. The efficiency and lifecycle of the main power supply system (e.g. fuel cell) can be improved. And good dynamics of the Hybrid Electric Vehicle have been achieved.
This paper proposes and studies new strategies for an increase of the energetic efficiency of an urban transportation network fed with catenaries. A simulation tool has been developed to determine the energy efficiency on the global transportation system (vehicles, feeding line and substations). The system energy consumption is identified by calculating the energy injected by the substations to the feeding line. It takes into account all the line losses and the interactions between the different vehicles on the line. The development of a new tool was necessary as other simulation tools calculate the energy consumption of the tram without taking in account the line properties and the interactions between the vehicles. Using this simulation tool, the energetic efficiency of a tram is studied while on board of the vehicle a supercapacitive energy storage has been added. The energy storage allows local energy recovery and injection of energy to the catenaries during braking phases. The results of simulations with or without on-board energy storage and with overhead lines with high resistive or standard behavior are presented. The results show that the global energy efficiency of the system (trams, feeding line and substations) is increased by a factor between 19.4 and 25.6% (depending on the vehicle auxiliaries power) by adding a supercapacitive energy storage for both cases presented in this paper: high and standard line resistance. The use of a high line resistance instead of a standard line resistance increases the efficiency of the total system by an additional 5%.
Two rating systems assessing the environmental damage caused by vehicles are compared: a Brussels one, ECOSCORE and a European one, CLEANER DRIVE. Both vehicle rating systems were developed for the assessment of vehicles with alternative types of fuels as well as different types of drive train, such as electric, hybrid and fuel cell vehicles. A simplified life cycle assessment following a well-to-wheel approach is used to compare the methodologies. Total emissions involve oil extraction, transport and refinery, fuel distribution and electricity generation and distribution as well as tailpipe emissions from the use phase. Different types of pollution such as acid rain, photochemical air pollution, noise pollution and global warming are examined and their impact on numerous receptors such as ecosystems, buildings and human beings (cancer, respiratory diseases, etc.) are investigated. Examples illustrate both methodologies and sensitivity analysis is used to examine the robustness of the systems.
Resulting from a Ph.D. research a Vehicle Simulation Programme (VSP) is proposed and continuously developed. It allows simulating the behaviour of electric, hybrid, fuel cell and internal combustion vehicles while driving any reference cycle [Simulation software for comparison and design of electric, hybrid electric and internal combustion vehicles with respect to energy, emissions and performances, Ph.D. Thesis, Department Electrical Engineering, Vrije Universiteit Brussel, Belgium, April 2000]. The goal of the simulation programme is to study power flows in vehicle drive trains and the corresponding component losses, as well as to compare different drive train topologies. This comparison can be realised for energy consumption and emissions as well as for performances (acceleration, range, maximum slope, etc.).
In order to configure super capacitor based energy storages in hybrid electric vehicles, the required peak power and the total amount of energy are estimated by using our strategies of energy source control and management during typical test cycles. The configuration of the super capacitor based energy storage for a dedicated vehicle has been verified with respect to the voltage variation, maximum current and power losses. The strategies of energy source control and management presented in this paper can be ensure efficiently and safely using the super capacitor based energy storage.
A supercapacitive-storage based substation for the compensation of resistive voltage-drops in transportation networks is proposed. It allows to feed as a current-source in any voltage conditions of the line. The system has been designed as a compensation-substation to be placed at weak points like end-of-line stations, instead of additional feeding substations. A dedicated power-electronic converter with an associated control system for the stabilization of the voltage level at the point of coupling in case of strong perturbations is proposed. Practical results are also presented, which have been recorded from a reduced-size prototype.
An ultracapacitor system for an electric vehicle has been implemented. The device allows higher accelerations and decelerations of the vehicle with minimal loss of energy and minimal degradation of the main battery pack. The system uses a DC-DC power converter, which is connected between the ultracapacitor and the main battery pack. The design has been optimized in weight and size, by using water-cooled heat sinks for the power converter, and an aluminum coil with air core for the smoothing inductance. The ratings of the ultracapacitor are: nominal voltage: 300 Vdc; nominal current: 200 Adc; capacitance: 20 Farads. The amount of energy stored allows us to have 40 kW of power during 20 seconds, which is enough to accelerate the vehicle without the help of the traction batteries. The vehicle uses a brushless DC motor with a nominal power of 32 kW and a peak power of 53 kW. A control system based on a Digital Signal Processor (DSP) manipulates all the aforementioned variables and controls the Pulse Width Modulation (PWM) switching pattern of the converter transistors. The car used for the implementation of this system is a Chevrolet LUV truck.
Innovative iteration algorithm for a vehicle simulation program
- J Van Mierlo
- G Maggeto
J. Van Mierlo and G. Maggeto, "Innovative iteration algorithm for a vehicle
simulation program," IEEE Trans. Veh. Technol., vol 53, no. 2. pp. 401-412,
Mar. 2004.