Conference PaperPDF Available

Improving energy efficiency in public transport: Stationary supercapacitor based Energy Storage Systems for a metro network

Authors:

Abstract and Figures

This article will assess the installation of stationary super capacitor based energy storage systems (ESS) along a metro line for energy savings purposes. The influence of the ESS size and distribution along the line will be studied taking into account different traffic conditions.The ESSs will be configured with regards to energy content, voltage variation, maximum current and power losses. To carry out the study, an 'effect-cause' or 'backwards looking' model of the light rail vehicles and the electric network has been developed in Matlab/Simulink. A power flow controller to handle the energy flow in function of the network voltage and ESS state of charge will be proposed.
Content may be subject to copyright.
A preview of the PDF is not available
... Siguiendo con este primer enfoque, pero más enfocado en las técnicas de optimización se presentó una síntesis de trabajos [23,32,68,69,[71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89]. Por ejemplo, [89] realiza una combinación de técnicas de control con lógica difusa; [60] presenta un estudio sobre técnicas de control adaptativo; [93] utiliza una función multiobjetivo y [28] presenta un algoritmo heurístico. ...
... Los autores proponen este dispositivo por su buena relación calidad-precio y por el gran desempeño que se ha visto en distintas instalaciones, como en el Metro de Varsovia en donde se logra ahorrar más de 2 MWh en una semana[69] y en el Metro de Washington se logra duplicar el ahorro energético al colocar los supercapacitores entre dos estaciones[70].Se propone la solución a un algoritmo de redes neuronales que determine el estado de carga (SOC) mínimo del sistema de almacenamiento para su óptima operación. En la actualidad, pocos estudios consideran el voltaje mínimo de operación de los paquetes de supercondensadores y optan por establecer valores constantes que rondan en 25% y 50%[71]. Para determinar el SOC mínimo primero se determinan las pérdidas del supercapacitor[72] y por separado las del convertidor DC-DC; dicho cálculo de pérdidas permite estimar la corriente del supercapacitor en función de la eficiencia del convertidor y obtener una relación que describa la variación de la tensión en las terminales del supercapacitor. ...
Chapter
Full-text available
En este capítulo se presenta una revisión sistemática sobre las tecnologías de sistemas de almacenamiento de energía y sobre los enfoques para un mejor aprovechamiento. La revisión se divide en dos vías: tendencias más desarrolladas (horarios de operación de los trenes, almacenamiento de energía y subestaciones reversibles) y los enfoques de investigación sobre el aprovechamiento del frenado regenerativo en los sistemas de transporte ferroviario (sistemas híbridos, algoritmos de optimización y técnicas de control, e integración de la generación distribuida).
... Due to the well-known advantages [1], energy storage devices on supercapacitors are used in regulated general application, industrial [4,6], traction [3,7], automobile [5,10], marine [9] and other electric drives [2,8,12]. In this case, energy storage devices allow to save the electrical energy, received from motor during braking, with its subsequent using during start-up in order to increase the energy efficiency, provide an uninterrupted power supply in case of a short-term disappearance of the mains voltage, and also to solve the problem of smoothing the peak power [11,13]. ...
... The need for the control and energy management of the energy storage system applied to urban rail transit system is highly crucial because of the frequent and numerous vehicles acceleration and braking operations which result in a very high rate of charging and discharging cycles. The control and energy management of the ESS must provide an efficient, optimal recovery in re-using the regenerative braking energy while ensuring safe and reliable operations of the energy storage devices as well as the bidirectional DC-DC converter [10], [190]. Depending on what is required to be achieved in the traction network -energy saving or voltage stabilization, that is the indicator which control strategy should be applied to the ESS [62], [191]- [194]. ...
Preprint
p>Electrified urban railway systems are large consumers of energy in urban areas and thus, there is a need for energy saving measures in this transportation sector. Recuperation of train’s regenerative braking energy (RBE) is one of the best ways for attaining high levels of energy efficiency in this area. Energy Storage Systems (ESSs) prove to be the most practical and viable solution for maximizing the RBE utilization in urban railway systems. In the existing related reviews of ESSs, few papers covered the review of ESS technologies or converter interface. However, a comprehensive review is needed in this regard. This paper discusses an overview of urban railway electrification, and detail review for the three ESS components – ESS Technologies, Bidirectional DC-DC Converters (BDCs), and Controller Unit. This study concludes that among the storage technologies, supercapacitor ESS appears to be the most suitable followed by Lithium-ion batteries and flywheels. For BDC, cascaded BDC is the most suitable followed by dual active bridge. For control methods, fuzzy logic and artificial intelligent are recommended among other control strategies. Thus, the key contribution of this paper is the comprehensive review and analyses of the ESS’s components in the recovery of RBE in urban railways. </p
... The basic cost incurred by the traction substation operator is usually the fee for the consumed energy [1], but also the fee for 15 min average power demand [2] as the fixed operating expenditure cost (OPEX) is considered [3]. Sometimes, for instance in Korea, the energy and power demand fee is charged additionally with the time-of-use tariff (TOU) [4], while the local distribution network operator (for example in Thailand) may also charge the traction substation operator with a service fee and a power factor fee [5]. ...
Article
Full-text available
This paper introduces the concept of fault-tolerant control (FTC) of a multi-string battery energy storage system (BESS) in the dynamic reduction system of a traction substation load (DROPT). The major task of such a system is to reduce the maximum demand for contracted peak power, averaged for 15 min. The proposed concept, based on a multi-task control algorithm, takes into account: a three-threshold power limitation of the traction substation, two-level reduction of available power of a BESS and a multi-string structure of a BESS. It ensures the continuity of the maximum peak power demand at the contracted level even in the case of damage or disconnection of at least one chain of cells of the battery energy storage (BES) or at least one converter of the power conversion system (PCS). The proposed control strategy has been tested in a model of the system for dynamic reduction of traction substation load with a rated power of 5.5 MW. Two different BESS implementations have been proposed and several possible cases of failure of operations have been investigated. The simulation results have shown that the implementation of a multi-string BESS and an appropriate control algorithm (FTC) may allow for maintenance of the major assumption of DROPT, which is demanded power reduction (from 3.1 MW to 0.75 MW), even with a reduction of the BESS available power by at least 25% and more in the even in fault cases.
... At present, most of the research focuses on metro. Barrero et al. [9] put forward a stationary supercapacitor-based energy storage system for metro. The capacity and installation location of energy storage system are studied for different traffic conditions, with the aim of saving energy by maximizing the use of regenerative braking energy. ...
Article
Full-text available
Abstract The regenerative braking energy generated during the braking of high‐speed trains affects the power quality of the power grid. Recovery of regenerative braking energy is problem that needs to be solved urgently. The regenerative braking energy of high‐speed railway features high power and high energy. It is difficult to recover it only by using high power density supercapacitors or high energy density batteries. In this paper, a hybrid energy storage system (HESS) composed of supercapacitors and lithium‐ion batteries and its optimal configuration method are proposed for the purpose of obtaining maximum economic benefits for railroad systems. Then the economic benefits when using the HESS and the single energy storage system are compared from the perspective of whether the regenerative braking energy is fully recycled or not. Finally, a simulation analysis with actual load of a high‐speed railway station is performed. The highest benefit is achieved when the regenerative braking energy is partially recovered by the HESS, which can save 3% of the total cost per day and pay back the cost in eight years.
Book
Full-text available
El contenido de este libro trata sobre una ingeniería global y sostenible que guie a la sociedad en su tránsito por el Nuevo Orden Mundial. Los autores de cada capítulo plasman sus pensamientos acerca de muchas de estas cuestiones, tan necesarias en la actual situación del Planeta, ofreciendo una perspectiva global de la ingeniería para el mundo, y no para atender al neoliberalismo imperial. Las investigaciones desde las que se generan los capítulos aquí incluidos son de carácter transdisciplinar, ya que esta deberá la manera en que se desarrolle la ingeniería en la Nueva Era que estamos viviendo.
Article
Hydrogen is acquiring a central role in energy uses, aiming to support and, then, replace conventional sources. Innovative smart-grids are based on new concepts of energy production and distribution, focus of research studies and preliminary prototypes. In this field, fuel cell-based vehicle-to-grid applications can be a useful system as a back-up power device during energy oscillations and as a transportation mode, especially in public service. In the present paper, a fuel cell hybrid tram is numerically tested, modelling dynamically each main component, with the aim to operate as a power and heat supplier, during the night, and as an urban light rail vehicle, during the day. The fuel cell model is developed, highlighting the principal elements of stack, auxiliary and heat-water management sub-systems. Performance improvements, such as regenerative braking and cogenerative processes, are taken into account, conceptualizing an innovative cooling method. In addition, a 3D CAD model is built to define a suitable layout for the hybrid powertrain, following safety guidelines. In the simulation campaigns, encouraging results are achieved for the case study analysed: for daily operations, the fuel cell-based powertrain provides approximately 2 MWh, consuming 108 kg of hydrogen (48 kg in vehicle-to-grid mode and 60 kg in mobility mode) and reaching an overall efficiency of approximately 43%. In addition, during vehicle-to-grid mode, the tram supplies thermal power capable of warming up at 45 °C almost 0.2 kg/s of tap water on average, obtaining a cogenerative efficiency that exceeds 60%. The promising performance achieved could represent the first steps of the proof of feasibility for this innovative technology.
Chapter
Full-text available
La medición de la conductividad eléctrica CE en la solución nutritiva, que se suministra a las plantas en un cultivo aeropónico, permite conocer la concentración total de sales de manera que se pueda determinar la cantidad de nutrientes presentes en todo momento en la solución, para asegurar un desarrollo adecuado de las plantas. Una CE alta puede inducir toxicidad por salinidad, mientras que una CE baja viene acompañada de una deficiencia de macro y micronutrientes. En el presente trabajo los autores identificaron y experimentaron las ventajas del sistema remoto comparado con las mediciones manuales en campo. El sistema remoto permite conocer la CE de la solución nutritiva de manera regular durante todo el proceso de desarrollo de las plantas y facilita, tanto la toma de datos, como el registro de estos. Con el sistema implementado se pudo conocer en tiempo real cómo varían las concentraciones en la solución nutritiva de un cultivo de lechuga, para de esta manera determinar cuándo debe adicionarse agua o reponerse la solución nutritiva.
Article
This paper proposes the optimal charging and discharging scheduling algorithm of energy storage systems based on reinforcement learning to save electricity pricing of an urban railway system in Korea. Optimization is done through reinforcement learning of charging and discharging schedule of energy storage systems according to the unit of electricity pricing rates as well as a reduction of peak power demand to save electricity pricing. To do this, modeling of urban railway systems including energy storage systems, electricity pricing rates, and changes in rates according to operations of energy storage systems are carried out. Reinforcement learning for an agent is also done to reduce peak power demand through DQN algorithm. Operation data of actual lines of urban railways operating with energy storage systems are utilized for learning. For this reinforcement learning, about 399(45.3%) incorrect data are removed and 481(54.7%) normal data are extracted. Through the reinforcement learning, maximum peak power demand is reduced by a targeted amount, 100 kW, from 2,982.4 kW to 2,882.4 kW. When the peak power demand is under 2,600 kW, charging at times when the power rate is cheaper and discharging at times when the power rate is more expensive are carried out, thus saving the total electricity pricing.
Article
Artykuł przedstawia analizę kryteriów oraz drogę sformułowania założeń projektowych, a także praktyczną realizację układu napędu trolejbusu. Przedstawiono dwa istotne zagadnienia, które mają decydujący wpływ na podniesienie sprawności energetycznej, jakimi są układ falownika, który umożliwia efektywne wykorzystanie zasobnika pojemnościowego złożonego z baterii superkondensatorów oraz sam dobór i wymiarowanie zasobnika z uwzględnieniem aspektów ekonomicznych.
Article
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.
Article
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.
Article
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.
Conference Paper
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.
Article
In this paper, a new mathematical model in semi-empirical form for lead-acid batteries is presented, which describes the relationship between the battery terminal voltage and the variable discharge current. Based on the proposed model, a new estimation method of the battery available capacity (BAC) in the presence of variable discharge currents is developed. The method involves the real-time identification of the model parameters which are then used to estimate the BAC according to the predefined cutoff voltage and the trend of battery terminal voltage during discharging. Thus, both temperature and aging influences on the BAC are considered inherently. Comparisons between the calculated results and the measured data confirm that the proposed method can provide an accurate real-time estimation of the BAC under variable discharge currents.
Conference Paper
The paper deals with the actual theme of power management in traction systems presenting a study about the use of regenerative braking energy in electric subway transportation. Storage systems on board of the vehicles or on fixed plants can give advantages both to contain the costs of the electric power and to limit power losses along the traction line. Moreover, other technical advantages can be obtained as, for example, the reduction of contact line voltage fluctuations. With reference to a real case, one of the Milan subway lines, a software program is implemented in order to simulate the electric power flow and to optimize the storage device size and control
Conference Paper
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
Conference Paper
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
Conference Paper
The presented article will describe an 'effect-cause' model for the purpose of simulating the energy consumption of DC fed light rail vehicles. The model will assess the advantages of hybrid vehicles in terms of energy consumption, network power and voltage variations, line current and losses; and will help sizing and designing a supercapacitor based energy storage system (ESS) for both on-board, and stationary applications. The proposed modeling needs to allow the ESS sizing according to the objective that needs to be achieved, being braking energy recovery, voltage drop compensation and peak power shaving the most common goals of ESS use in hybrid vehicles. The needed power and energy levels will vary in function of the vehicle features and the driving cycle followed. This all can be determined by the quasi-static simulation tool to ease the design process. Another objective of the modeling tool is to evaluate the behaviour of the vehicle power flow controller, which manages the power from/to the ESS in function of the state of several variables.
Conference Paper
The on board energy storage system with Ultracaps for railway vehicles presented in this paper seems to be a reliable technical solution with an enormous energy saving potential. Bombardier Transportation has equipped one bogie of a prototype LRV (light rail vehicle) for the public transportation operator RNV in Mannheim with a MITRAC Energy Saver. Outstanding feature is the daily operation of the energy storage unit in daily passenger service, and this even since September 2003. The experiences are very positive. The measured traction energy saving of approximately 30% confirmed fully the former calculations. Running the energy storage device on board of a tram brings additionally following benefits: (i) a dramatic reduction of the peak power demand (ii) catenary free operation" on several hundred meters without power supply from the catenary (iii) catenary free city center by on board storage and recharging stations. Applying the energy storage devices in Metro systems has a similar effect as in case of LRVs. However the savings distribution in the whole system will be a little bit different. Due to higher regeneration capability of metro systems the expected share of the train propulsion saving will be lower. It will be compensated by a considerable reduction of the line losses, especially for systems with low rated catenary voltages (600 V or 750 V). Very promising are energy storage applications in propulsion systems of diesel-electrical multiple units (DEMUs). These vehicles lack possibilities to use the braking energy of the train. Energy storage systems on board of DEMUs bring high fuel savings together with the corresponding emission reduction. On top of that the energy storage leads to a booster effect - extra power during acceleration from the storage, by adding the limited weight of the MITRAC Energy Saver.