As the rail industry explores the use of battery-powered trains, there comes a need to consider how traction batteries are recharged and generally managed. Battery-powered trains are not new, there were various early examples. Experiments with accumulator railcars, as they were initially called, were conducted from around 1890 in Belgium, France, Germany and Italy. Between 1955 and 1995, Deutsche Bahn in Germany successfully operated a fleet of 230 Class ETA 150 railcars utilising lead acid batteries.
Japan has taken to battery rail vehicle development and has combined this with contact system electrification, charging taking place from the fixed system.
British Railways, in the late 1950s, produced a battery version of its Derby Lightweight first- generation diesel multiple units. The unit went into service on the Aberdeen-Ballater branch line in 1958 and the North of Scotland Hydro-Electric Board provided recharging facilities at Aberdeen Platform 1 and at Ballater.
The batteries were large lead-acid units weighing about eight tonnes. Development of the traction battery continued but special strengthening of the BEMU (Battery Electric Multiple Unit) underframe was required. Charging was by shore supply cables at each end of the line, which had to be connected manually. The train either ran in to a special charging siding or careful cable management was required at the terminal.
In the South, the Class 419 battery motor luggage vans were capable of running on batteries or a third rail, useful for short non-electrified sections on quayside lines at Folkestone and Dover.
Lead-acid batteries, as used on these first-generation rail vehicles, are not the most efficient or effective form of stored energy electrical power. However, battery development has proceeded apace, as it has on road vehicles. Weight penalties are now therefore much reduced, increasing the attractiveness of battery-powered vehicles.
While super-capacitors have been used on some light rail schemes, these are not really suited to heavier applications, being more useful for short sections of light rail in architecturally sensitive areas. So any use of stored energy on heavy rail will, for the foreseeable future, be a question of battery technology.
The growth of network electrification has also driven a desire for electric traction on non- electrified routes. In 2015, a single Class 379 Bombardier Electrostar, after the installation of lithium-ion batteries, went into service on the Mayflower line (From Manningtree to Harwich) in Essex. The term IPEMU (Independently Powered Electric Multiple Unit) was coined to describe it.
All this development of rolling stock has led to new thoughts on how to recharge units, as there will not always be an installation of contact system electrification to provide charging facilities – particularly not at the remote end of a branch line.
Furrer+Frey and Opbrid (now a Furrer+Frey company) have developed a product known as RailBaar, an ultra-high-power rapid charge station suitable for the exact purpose discussed above – the charging of battery-equipped rail vehicles in service.
Ankur Saxena, Furrer+Frey’s project engineering manager based in the UK, described how RailBaar is a rapid-charge station for battery trains. RailBaar takes proven technology from tram, bus and lorry rapid charging stations and applies the same principles to the rail industry, exploiting innovations in battery power to produce an overhead automatic electric charging station for battery-powered electric trains. This facility eradicates the need for an overhead contact system and can economically extend the scope and range of independently powered trains.
Furrer+Frey feels that the system could be a game changer, dramatically reducing the cost of electrification, and thus the feasibility of new electrification projects.
For RailBaar to be successful, Opbrid and Furrer+Frey worked together on a collaborative project. Experience was drawn from their success with BusBaar, which various bus manufacturers and cities have deployed on road vehicles since 2010.
The system incorporates a platform or trackside mechanism that can be lowered to the height of any train or raised to a suitable safe height when not charging. It integrates all charging electronics into a single vertical mast for a remarkably small total footprint of less than 0.5m2. The compact overhead unit thus reduces visual impact, provides more space for passengers on the platform and allows the use of a wide variety of mounting posts to match, and complement, the existing station architecture.
As a safety consideration, the design incorporates twin-contact fixed in-line current collectors on the roof of the vehicle. This offers lowest cost, weight and maintenance liability. The train installation is mechanically passive and thus offers low risk.
The RailBaar design offers a number of advantages:
- With a small footprint, the equipment can be adapted to fit almost any train and station/platform;
- The design allows a pathway to future ultra-high-power transfer requirements;
- Safety features always ensure correct connection, even with vehicles and charging stations from different manufacturers and with differing power requirements;
- The system allows for multi-modal use with integrated road and rail transport networks;
- Its modular design is flexible and makes extending transport network routes easy so networks can grow with the strategic placement of further charging stations;
- Designed for very large standstill current and power transfer;
- An integrated cover offers an additional level of safety.
The basic infrastructure provides the ability to charge the vehicle with route-end platform-side charging or at depot facilities where there may be a 24/7 depot charger for applications such as airport transfers or routes with multiple battery- operated trains. A mini-charging depot for quick one-to-three minute top-ups is also possible.
Charging time can be a major consideration, with turn-round or dwell times potentially being under pressure for a return or connecting service. Consideration of the supply capacity at the charging site is essential as a full charge will exert a significant power demand. The system’s fast mechanical connection maximises the charging time.
The compact nature of the RailBaar design, with all of the moving parts contained within a protective hood, allows it to be mounted on a wide variety of supports, giving designers and architects the freedom to blend the plant visually into the terminal design. The equipment may also be attached to existing structures such as buildings and platform shelters.
Having all of the electronics inside the charging post eliminates the need for a bulky external electronics enclosure. This further helps in planning, site preparation, and ease of installation.
Advantages in operation
The system has many in-built safety features. The RailBaar itself is switched off when not in use and may be sited at the end of a platform – the isolated system can be regarded as lower in risk than live contact systems. In operation, the RailBaar gantry automatically lowers the current collector onto the contact strips mounted onto the roof of the train and, as the train departs, the RailBaar moves the current collectors safely away.
Use of the RailBaar system will allow a battery- powered train to be continuously in service while ultrafast charging permits the use of smaller, lighter traction batteries. There is little, if any, weight penalty on the rail vehicle as there are no moving parts thereon, reducing the potential vehicle mass.
As there are likely to be more trains than charging stations, the cost per vehicle of charging arrangements is kept to a minimum. And RailBaar need not be the only source of power for the batteries, regenerative braking systems can provide additional recharging.
As detailed above, RailBaar has been developed from existing installations for buses and so has been in use since 2010. The technology is also currently being installed on tram routes and is under development for lorry applications.
One recent installation by Furrer+Frey was in China on the 20.3km Huai’an light rail line, which opened in February. The line is entirely catenary- free and utilises battery-powered LRVs, supplied by CRRC Zhuzhou, which recharge at charging points at end of the route.
In addition, Furrer+Frey has supplied two all-in- one charging stations, each 300kW, for a project in Utrecht, Netherlands and another two, this time 150kW each, to CAF for a project in Valladolid, Spain.
Furrer+Frey is examining various further options – the boundary of existing third-rail systems would seem to be an attractive option as the use of RailBaar could avoid high installation costs on what could be a very low-use periphery of the system.
As the concept of the independently-powered electric multiple unit continues to grow in popularity, the RailBaar system appears to offer an environmentally sensitive solution to charging points while reducing risk.
Written by Peter Stanton