Trams are great people movers. After an early boom, many systems around the world were removed and replaced by buses, but that trend is being reversed in many cities, while others never lost their beloved trams.

However, while the tracks can be buried in the city streets, there is still the problem of what to do with the wires. They are unsightly, particularly when crossing a historic city square when poles have to be installed to support them.

So the major manufacturers have come up with various ways of removing the wires (issue 98, December 2012). Induction loops buried in the road is the most discrete – there is nothing to see at all, but a flush-mounted third rail and overhead charging stations at tram stops with no wires in between have all been tried and adopted for a few installations.

Now, another milestone in the development of these wire-less systems has taken place. On 1 October 2015, Bombardier successfully completed a 41.6 km catenary-free test run with a tram powered entirely by its Primove battery in combination with a Mitrac propulsion system. The test run was conducted in the German city of Mannheim on the network of Rhein-Neckar-Verkehr GmbH (RNV), the transport operator for the region.

The innovative Primove battery system builds upon Bombardier’s many years of experience with energy storage systems. The system combines high power capacity and exceptional battery life with good reliability and has been designed to maximise performance using the latest developments in nickel manganese cobalt (NMC) Li-Ion cells.

An advanced thermal conditioning unit maintains the battery’s ideal temperature and enables rapid charging and full braking energy recovery while extending life up to ten years.

German partnership

This is another milestone in the long-standing partnership between RNV and Bombardier, and represents the evolution of e-mobility. Both companies have always focussed strongly on e-mobility as well as on exploring different applications of this concept.

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RNV operates in the cities of Heidelberg, Ludwigshafen and Mannheim in the German province of Baden-Württemberg and owns 82 Bombardier-built trams.

In December 2009, six of these trams were commissioned and featured the first commercial application of Bombardier’s Mitrac Energy Saver at RNV’s Heidelberg site. This makes a 30% energy saving and utilises an energy-recovery system – three roof-mounted energy storage units use their capacitors to store the energy generated during braking, ready to release it again when accelerating or during operation.

The Mitrac Energy Saver features high-performance double-layer capacitors which store up to 3kWh per vehicle. When starting up and accelerating, vehicles require a particularly large amount of electricity and put a significant burden on the power supply network. Drawing power from the Mitrac capacitors reduces this by some 40 per cent, allowing the network to be utilised more cost effectively.

Using stored energy has also allowed sections of the route to be operated without contact wires. A total of 19 vehicles were equipped with this feature.

Buses too

Primove doesn’t just power trams. Since June 2015, city centre bus line 63 in Mannheim, Germany, has been operated by two fully electric buses, charged and powered by Primove technology. This has proved the system’s suitability for regular revenue service, even on demanding bus routes, giving passengers a quiet and emission-free ride.

Mannheim’s new e-bus line is the result of cooperation between regional transport operator RNV, Bombardier Transportation, the City of Mannheim, the Karlsruhe Institute of Technology and Swiss bus manufacturer Hess AG. The 12-metre vehicles are the first of their kind to be equipped with the complete Primove package, which includes wireless charging technology, long-life battery system and a fully integrated propulsion system.

Electrifying the bus route presented the team with several challenges. Not only does the nine-kilometre line run through the heart of the city, but buses typically only rest at each stop for a very limited time. To meet this challenge, a series of four fast, high-power charging stations were installed at strategic locations along the line, one at each end stop and one at the bus depot.

With this arrangement, the system only needs to charge for about thirty seconds at each of the four charging stops and then for approximately five minutes at the end stops. This is enough to provide a single e-bus with sufficient energy to serve the entire route and eliminates the need for any additional charging or time-consuming battery exchanges. Mannheim’s two e-buses will save around 180 tonnes of CO2 per year, equal to the emissions of 74 private cars.

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In addition to the two buses, a fully electric Primove-equipped van will also be used by RNV as a service and delivery vehicle. With a maximum range of 240km, it can easily complete its daily 80km service route after charging wirelessly at the depot for just 180 minutes. The project is funded by the German Federal Ministry of Transport and Digital Infrastructure (BMVI).

The Primove battery

Designed specifically for public transport applications, Primove battery systems were developed and tested according to safety standards both from the railway and automotive sectors. The multi-level safety concept covers all aspects of functional, electrical, chemical, mechanical and occupational safety, making it one of the safest battery systems on the market today.

Through the Primove Care portal, all battery system components will be monitored in real-time, providing feedback on their usage and remote failure analysis to optimise the reliability and availability of the system.

China followed

In addition to the above applications in Germany, the combination of Primove battery and Mitrac propulsion equipment has been in revenue service on the Hexi line in Nanjing, China since August 2014. Six trams, built by CRRC Puzhen under Bombardier license, operate without overhead cables on 90 per cent of the lines. The batteries are charged during passenger service via the pantograph, statically at tram stops and dynamically during deceleration.

In total, six vehicles run on the Hexi line, which connects four stops on central metro lines 1 and 2 with the venues of the Youth Olympic Games. Another seven vehicles are planned for the 9km Qilin line, also in Nanjing, which features steep sections and an elevated route over a major highway.

Following on from these successful introductions in Germany and China, the Primove/Mitrac combination is now being considered for other systems requiring catenary-free operation (CFO) around the globe.