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Evaluation of CO 2 emissions reduction in diesel-electric trains with advanced batteries
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The railway sector is facing significant challenges in addressing the increasing concerns related to climate change, environmental pollution and scarcity of resources. This especially applies to often non-electrified regional railway networks, with passenger services provided by diesel-driven vehicles. Innovative propulsion system concepts offer significant improvement of energy efficiency and reduction of overall environmental impact from train operation. This study presents a life cycle assessment of greenhouse gas emissions linked to the implementation of alternative powertrain systems in conventional diesel-electric multiple-unit vehicles employed on the regional railway lines in the northern Netherlands. The analysis encompassed the retrofit of a standard vehicle to its hybrid-electric, fuel cell-electric and battery-electric counterparts, and a comparative assessment of life cycle emissions during a ten-year time horizon. Results indicated significant impact of the production pathway for alternative energy carriers to diesel, namely hydrogen and electricity. The largest reduction in total emissions (96.80%) is obtained for a fuel cell-electric vehicle running on hydrogen produced from electrolysis, with slightly lower performance shown by the battery-electric configuration using green electricity produced from wind power (95.92%). Maintaining the diesel engine in the hybrid-electric alternative leads to a potential overall emission reduction of about 27%, as a result of improved fuel economy offered by the implemented energy storage system, and could be considered as a cost-effective transition solution towards carbon-neutral trains operation.
Non-electrified regional railway lines with typically employed diesel-electric multiple units require alternative propulsion systems to meet increasingly strict emissions regulations. With the aim to identify an optimal alternative to conventional diesel traction, this paper presents a model-based assessment of hydrogen-powered propulsion systems with an internal combustion engine or fuel cells as the prime mover, combined with different energy storage system configurations, based on lithium-ion batteries and/or double-layer capacitors. The analysis encompasses technology identification, design, modelling and assessment of alternative powertrains, explicitly considering case-related constraints imposed by the infrastructure, technical and operational requirements. Using a regional railway network in the Netherlands as a case, we investigate the possibilities in converting a conventional benchmark vehicle and provide the railway undertaking and decision-makers with valuable input for planning of future rolling stock investments. The results indicate the highest fuel-saving potential for fuel cell-based hybrid propulsion systems with lithium-ion battery or a hybrid energy storage system that combines both energy storage system technologies. The two configurations also demonstrate the highest reduction of greenhouse gas emissions compared to the benchmark diesel-driven vehicle, by about 25% for hydrogen produced by steam methane reforming, and about 19% for hydrogen obtained from electrolysis of water with grey electricity.
The energy consumption estimation of a locomotive for a particular route is important for the selection of a locomotive technology, the improvement of the energy management system, the evaluation of the locomotive’s potential energy generation, among others. The methodologies reported in the literature usually assume that the information of the railway track is available; however, in some cases, the track information is incomplete, not available, or the route is still in a planning stage. Therefore, this paper proposes a methodology to estimate the energy consumption and the potential energy generation of a locomotive when the railway track information is not available or incomplete. The methodology begins by extracting the main technical information of the locomotive to be analyzed. Then, the route is traced on Google Earth with steps of 100 m and the obtained information is processed to generate the longitude, latitude, elevation, and distance of the points along the route. From such information, it is possible to generate the slope and curvature profiles, while the speed profile can be obtained from the track operator or the regulations of a specific country. With that information, it is possible to estimate the equivalent power of the locomotive at each point of the route to finally calculate the consumed energy. The proposed methodology is validated with two case studies. The first one compares the results with a methodology available in the literature for the same route and locomotive, while the second case shows the applicability of the proposed methodology for a route without information.
Rail transport, specifically diesel–electric trains, faces fundamental challenges in reducing fuel consumption to improve financial performance and reduce GHG emissions. One solution to improve energy efficiency is the electric brake regenerative technique. This technique was first applied on electric trains several years ago, but it is still considered to improve diesel–electric trains efficiency. Numerous parameters influence the detailed estimation of brake regenerative technique performance, which makes this process particularly difficult. This paper proposes a simplified energetic approach for a diesel–electric train with different storage systems to assess these performances. The feasibility and profitability of using a brake regenerative system depend on the quantity of energy that can be recuperated and stored during the train’s full and partial stop. Based on a simplified energetic calculation and cost estimation, we present a comprehensive and realistic calculation to evaluate ROI, net annual revenues, and GHG emission reduction. The feasibility of the solution is studied for different train journeys, and the most significant parameters affecting the impact of using this technique are identified. In addition, we study the influence of electric storage devices and low temperatures. The proposed method is validated using experimental results available in the literature showing that this technique resulted in annual energy savings of 3400 MWh for 34 trains, worth USD 425,000 in fuel savings.
This paper presents a simulation-based analysis of hybrid and plug-in hybrid propulsion system concepts for diesel-electric multiple unit regional railway vehicles. These alternative concepts primarily aim to remove emissions in terminal stops with longer stabling periods, with additional benefits reflected in the reduction of overall fuel consumption, produced emissions, and monetary costs. The alternative systems behavior is modeled using a backward-looking quasi-static simulation approach, with the implemented energy management strategy based on a finite state machine control. A comparative assessment of alternative propulsion systems is carried out in a case study of a selected regional railway line operated by Arriva, the largest regional railway undertaking in the Netherlands. The conversion of a standard diesel-electric multiple unit vehicle, currently operating on the network, demonstrated a potential GHG reduction of 9.43–56.92% and an energy cost reduction of 9.69–55.46%, depending on the type of service (express or stopping), energy storage technology selection (lithium-ion battery or double-layer capacitor), electricity production (green or grey electricity), and charging facilities configuration (charging in terminal stations with or without additional charging possibility during short intermediate stops) used. As part of a bigger project aiming to identify optimal transitional solutions towards emissions-free trains, the outcomes of this study will help in the future fleet planning.
The present work evaluates the application of regenerative braking for energy recovery in diesel-electric freight trains to increase efficiency and to improve decarbonization. The energy from regenerative braking has to be stored onboard when the track is not electrified. Different technologies of energy recovery are presented and discussed. The energy balance of an existing route is presented and simulated for different battery sizes. The analysis is illustrated with experimental data from an important Brazilian railway. Results show that the energy recovery from regenerative brake is a feasible investment and may be recommended to increase the efficiency in transportation and also to improve the low carbon mobility in railway systems.
A problem of peak power in DC-electrified railway systems is mainly caused by train power demand during acceleration. If this power is reduced, substation peak power will be significantly decreased. This paper presents a study on optimal energy saving in DC-electrified railway with on-board energy storage system (OBESS) by using peak demand cutting strategy under different trip time controls. The proposed strategy uses OBESS to store recovered braking energy and find an appropriated time to deliver the stored energy back to the power network in such a way that peak power of every substations is reduced. Bangkok Mass Transit System (BTS)-Silom Line in Thailand is used to test and verify the proposed strategy. The results show that substation peak power is reduced by 63.49% and net energy consumption is reduced by 15.56% using coasting and deceleration trip time control.
The paper considers a novel approach to heavy-haul of railway freight by means of combined operation of conventional diesel-electric and battery-electric locomotives either in single or joint (tandem) operation. A backward-looking quasi-static model of a battery-electric locomotive is proposed, based on the undercarriage of a decommissioned conventional diesel-electric locomotive equipped with a sufficiently-sized battery energy storage system. In order to facilitate power flow control from the battery-electric locomotive and to avoid deep battery discharges a suitable control rule is introduced aimed at modulating the driver power (throttle Notch) command in order to maintain the battery state-of-charge above the safe lower limit during discharging. The effectiveness of the proposed approach has been verified by means of simulations for the considered mountainous railway route driving scenario, including realistic railway track slope and speed limitations. The results show that between 22% and 30% fuel cost savings may be achieved, along with reduced emissions of exhaust gases by using the proposed battery-electric locomotive in combination (tandem) with the conventional diesel-electric one.
Hybridization of diesel multiple unit railway vehicles is an effective approach to reduce fuel consumption and related emissions in regional non-electrified networks. This paper is part of a bigger project realized in collaboration with Arriva, the largest regional railway undertaking in the Netherlands, to identify optimal solutions in improving trains’ energy and environmental performance. A significant problem in vehicle hybridization is determining the optimal size for the energy storage system, while incorporating an energy management strategy as well as technical and operational requirements. With the primary requirement imposed by the railway undertaking to achieve emission-free and noise-free operation within railway stations, we formalize this as a bi-level multi-objective optimization problem, including vehicle performance, the trade-off between fuel savings and hybridization cost, influence of the energy management strategy, and other constraints. By deriving a Li-ion battery parameters at the cell level, a nested coordination framework is employed, where a brute force search finds the optimal battery size using dynamic programming for full controller optimization for each feasible solution. In this way, the global minimum for fuel consumption for each battery configuration is achieved. The results from a Dutch case study demonstrated fuel savings and CO2 emission reduction of more than 34% compared to a standard vehicle. Additionally, benefits in terms of local pollutants (NOx and PM) emissions are observed. Using an alternative sub-optimal rule-based control demonstrated a significant impact of the energy management on the results, reflected in higher fuel consumption and increased battery size together with corresponding costs.
The issues of global warming and depletion of fossil fuels have paved opportunities to electric vehicle (EV). Moreover, the rapid development of power electronics technologies has even realized high energy-efficient vehicles. EV could be the alternative to decrease the global green house gases emission as the energy consumption in the world transportation is high. However, EV faces huge challenges in battery cost since one-third of the EV cost lies on battery. This paper reviews state-of-the-art of the energy sources, storage devices, power converters, low-level control energy management strategies and high supervisor control algorithms used in EV. The comparison on advantages and disadvantages of vehicle technology is highlighted. In addition, the standards and patterns of drive cycles for EV are also outlined. The advancement of power electronics and power processors has enabled sophisticated controls (low-level and high supervisory algorithms) to be implemented in EV to achieve optimum performance as well as the realization of fast-charging stations. The rapid growth of EV has led to the integration of alternative resources to the utility grid and hence smart grid control plays an important role in managing the demand. The awareness of environmental issue and fuel crisis has brought up the sales of EV worldwide.
Hitachi, Ltd. has been developing vector-control techniques, high-voltage insulated gate bipolar transistors (IGBTs), snubberless inverters, soft-gate circuits which can control switching behavior of IGBTs, airless line breakers, and electronic master controllers to make train traction systems smaller, lighter, more functional, and easier to maintain. Recently, however, the need for upgrading train traction systems has been growing due to changes in social conditions such as heightened environmental consciousness. In particular, train traction systems need to be even easier to maintain, more energy efficient, smaller and lighter (through simplification of cooling equipment by reducing refrigerant and blowers), and more functional (improved passenger comfort). To meet these new needs, Hitachi has developed (1) high-conductivity, high-voltage power devices to make cooling equipment smaller and lighter, (2) snubberless inverters using high-voltage power devices to reduce the number of components, (3) control systems to achieve advanced rolling-stock control and high functionality, (4) train power control using on-board data-transmission equipment, and (5) low-maintenance motors. Hitachi is enhancing these technologies to provide a train traction system that is smaller and lighter and easier to maintain while improving passenger comfort (Fig. 1).
The trapezoidal rule is a numerical integration method to be used to approximate the integral or the area under a curve. The integration of [a, b] from a functional form is divided into n equal pieces, called a trapezoid. Each subinterval is approximated by the integrand of a constant value. This paper provides three SAS â macros to perform the area under a curve (AUC) calculation by the trapezoidal rule. The first macro allows you to select the number of subintervals from a continuous smooth curve and then performs the area under the curve calculation. The second macro allows you to select the accuracy level of the approximation and then performs the necessary iterations to achieve the required accuracy level of approximation. The third macro is for discrete points of (x, y) and performs the area calculation. The SAS products used in this paper are base SAS , and SAS/STAT â , with no limitation of operating systems.
In the field of railway braking, improving the performances of friction brake systems requires better knowledge of the local tribological behaviour of pad–disc contact under braking conditions. After analysing the tribological triplet involved in railway braking, this paper focuses on the development of laboratory tests for studying local physical phenomena caused by friction in braking. The aim is to generate at reduced scale similar contact conditions to those at full-scale. An original braking tribometer is presented whose design is based on similitude rules between reduced-scale and full-scale. As it is difficult to reproduce representative full-scale thermal loading generated by friction at reduced-scale, compromises are needed and the choice of experimental parameters, based on a non-dimensional conversion rule, is discussed. The results obtained at reduced-scale are presented and comparison with results available at full-scale shows that the reduced-scale tests are very representative.
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