Forever young: trolleybuses offer a green solution for public transport

The future of public transport is electric – as it was once before. The trolleybus with poles for the overhead lines brings a number of benefits for the ecological balance of modern cities.

With nicknames like the "Cable Express" and the "Pole Taxi", trolleybuses have really made their mark on their home towns. The "Express", Germany's oldest trolleybus, has been on the road in Eberswalde since 1940; the "Taxi" has been doing the rounds in Solingen since 1952. And to this day, the trolleybus solution keeps on winning over cities and municipalities: In 2011, futuristic-looking trolleys designed for desert conditions began transporting passengers around the King Saud University campus in Riyadh. Malatya in Turkey introduced a new trolleybus system for double-articulated buses in 2014, as it offers substantially lower costs than a tram system of similar capacity (>200 passengers per vehicle). In Italy, a new Rapid Coast Transport (TRC) express line will be opened between Rimini and Riccione in 2019. And from 2021, thanks to the IMC charging concept, these buses will travel through the center of Verona without overhead contact lines. The fundamental reasons why these municipalities have driven the expansion of the trolleybus system: it offers a quiet, reliable, emission-free public transport solution with low operating costs and a long vehicle service life. It should ease the overall burden on the city coffers, even though additional funds may be required to install the overhead power lines.

Improving the ecological balance

For many municipalities, there is another strong argument for the trolleybus: electric vehicles cut the most significant and hotly debated emissions, such as nitrogen oxides and CO2, to zero. The most familiar challenge for electric buses is energy storage. A modern battery is around 100 times heavier than the equivalent diesel fuel. In practice, this means that the electric vehicle can either carry significantly fewer people or has a much shorter range than its diesel rival. The challenge of "refueling" electrical energy is equally tough: spending one minute filling up a tank of diesel is equivalent to spending around 100 minutes charging an electric bus!

Trolleybuses offer crucial advantages in precisely these areas, thereby helping to optimize the use of electric buses in cities.

One of the first trolleybuses in Solingen. Models like this are a thing of the past, but the system continues to prove its worth to this day. © Knorr-Bremse
Knorr-Bremse is equally at home in the world of highly robust and efficient mechanics as it is in the world of flexible charging concepts for electric vehicles.

Peter Dr. Radina – Member of the Management Board of Knorr-Bremse’s Rail Vehicle Systems division

Trolleybuses – charging on the go

There are many battery and charging concepts for electric buses. They range from vehicles that complete their route on a single battery charge before being charged overnight to "flash-charging" at bus stops and charging stations at the terminals. One thing they all have in common: the vehicles are stood still while charging, not travelling.

Not so with trolleybuses: they are supplied with electricity during the journey. A particularly flexible option is to use overhead lines in combination with batteries. This is what the In Motion Charging (IMC®) concept from Knorr-Bremse offers. Here the overhead lines supply power to the vehicle while it is in motion and simultaneously charge its battery. Wherever the route does not have overhead lines, the bus runs on battery power. As a result, the battery can be smaller than those in buses that only charge overnight and standstill times for charging can be completely eliminated.

With the latest IMC version - IMC500 - the bus can draw up to 500 kW of power during travel. This makes it possible to power all sub-systems at the same time wherever overhead lines are available: two 160 kW motors (= 320 kW), the HVAC system and battery. The higher the charge rate, the less time the vehicle needs to spend under overhead lines to keep the battery topped up, which reduces the amount of infrastructure required. To be precise: IMC500 only requires an overhead line system to cover approximately 20% of the total route, so infrastructure costs can be kept to an absolute minimum.

With Kiepe Electric's IMC concept, large urban areas can remain free of overhead lines. The trolleybuses run on energy from the battery, which is charged in areas with overhead lines (light blue). This concept will come into play in Verona's new IMC system. © Knorr-Bremse
The trolleybus goes intercity: The major advantage of Knorr-Bremse's new In Motion Charging concept – IMC500 – is that trolleybuses only need overhead lines on 20 percent of their total route. The battery can power the remainder of the journey, with no extra charging stops. © Knorr-Bremse

Project Linz – from trolleybus to double-articulated electric bus

Trolleybuses have been running in Linz since 1944. The latest innovation is an IMC500 double-articulated trolleybus with a length of 24 meters and space for 180 passengers. This makes the latest trolley a cost-effective alternative to the tram. It has a range of up to seven kilometers in battery operation. In Austria, the length of articulated buses was limited to just under 19 meters until 2015. At the end of 2015 Linz AG announced that it had gained approval for its trolleybuses in XXL format. The first double-articulated trolleybus has been in operation since the end of November 2017. With more trolleybuses coming into service, the fleet renewal should be completed in 2019, when 20 electric buses will form a major feature of Linz's cityscape.

This 24-meter double-articulated bus in Linz has room for 180 passengers. In its latest form, the trolley has become a cost-effective alternative to the tram. © Knorr-Bremse

Trolleys in the contact shoe era

Trolleybuses take their name from the original four-wheeled trolley that ran on casters along the two overhead wires. It supplied the power for the electric drive via a flexible cable and was thus pulled along behind the motor vehicle. This principle, developed by Werner Siemens, was employed for the first time in 1882 – years before buses were powered by fuel. However, the trolleys had a tendency to derail. Negotiating branches in the line was also problematic. Finally, the trolleys were replaced by poles with contact shoes. But the trolleybus retained its name. With "In Motion Charging", Kiepe Electric has established a contemporary name for the latest technology to power the time-tested trolleybus. Kiepe Electric has trademarked the abbreviation IMC®, which is now used around the world – from Russia to China, the US and Europe.

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