Railway vehicles and energy storages - A contradiction?

Abstract

Besides automotive applications, the railway sector becomes a more and more important field of application for energy storages. The fact that the service conditions of a railway vehicle deviate from a car, e.g. railway vehicles have a higher energy consumption of auxiliary aggregates, suggests that different rules of dimensioning have to be considered for energy storages. This underlines the importance to have a well-directed focus on this means of transport. As there are many different railway vehicles who offer a potential to include (or already use) energy storages, it is important to determine the specific edge conditions of every vehicle segment. Each of the railway vehicle segments offers different individual constraints. That includes station spacing, mileage, performance, weight and cross section amongst others. These boundary conditions have a strong influence on the selection of an appropriate energy storage system –e.g.: while a (comparatively) low weight is an important factor for standard gauge railways, a heavy weight might have a positive impact for shunting locos that need a certain axial force, to transmit the required traction force. The fact that only ~50% of today’s tracks are electrified in Germany and Europe causes that diesel-driven vehicles are still a dominant technology in day-to-day passenger and goods rail transport. While fuel prices are expected to experience a steady increase in the next years, hybrid drivetrains or even fully electrified drivetrains come to the fore. The paper will discuss different applications for energy storages, like Light Rail Vehicles and Trams, shunting locos and standard gauge railways. In addition to possible scopes of application, the paper will discuss limitations and special restrictions, which result from the usage of energy storages in railway vehicles. A state-of-the-art review will focus on realized projects (R&D) and railway vehicles that already use energy storages. Furthermore the paper will show possible “new markets”, like the usage of traction energy storages for railway vehicles passing partly electrified tracks or non-electrified tracks. Finally an example for the design of a battery-driven and a hybrid railway vehicle will be presented. The dimensioning will be based on simulation results of a reference vehicle, running on a reference track. Therefore a simulation model, based on Dymola, will be used and described briefly.