Vehicle is 70th hybrid bus in the Rhein Rhuhr area since promotion began in 2009
GERMANY: WSW mobil GmbH has taken delivery of an 18m Mercedes- Benz Citaro G articulated hybrid with the aid of funding through the Rheine-Ruhr transport association.
The Rhein-Ruhr transport association (VRR), of which WSW mobil GmbH is a member, launched a promotional programme for hybrid buses in 2009. Today approximately 70 hybrids belonging to VRR transport companies have been subsidised with the help of the programme for ‘Innovative projects for the improvement of local public transport.’ The objective is to pool the findings and experience gained with regard to the new technology as part of a research programme and put them at the disposal of other transport companies and vehicle manufacturers.
Ulrich Piotrowski, who is responsible for the market launch of hybrid and electric buses at Mercedes?Benz, said: “Wuppertal is just perfect for the Citaro G BlueTec Hybrid. The demanding topography provides sufficient opportunity for energy recuperation via the brakes, but, if necessary, can also clearly demonstrate deficits thanks to the challenging routes. The experience gained during daily operations is invaluable to the further development of vehicles.”
When topographical conditions are ideal, the Citaro G BlueTec Hybrid can drive up to 10km using only electric power without the help of the diesel engine. Four electric wheel hub motors which draw their power from lithium ion batteries provide the drive. Electric current is generated when the brakes are applied and, if required, can also be obtained via a generator which is driven by a small diesel engine.
Outwardly, the light blue hybrid hardly differs from the rest of the WSW Citaro fleet. The bright and friendly interior is characterised by large windows, traffic red grab rails, which provide a contrast to the blue seat covers. A five-camera CCTV system improves safety and avoids damage through vandalism. The climate control in the passenger saloon and in the driver’s cab can be regulated independently of one another via the overhead air-conditioning system. The airconditioning concept, just like the fire alarm system and the automatic fire extinguishing system in the engine compartment, is standard WSW equipment.
Two 48.26 cm TFT monitors in the front and rear sections display the names of bus stops. When connected to the IBIS on-board computer, information regarding route progress and the name of the next bus stop are displayed. The IBIS is not only responsible for the control of the passenger information systems, but also for traffic signal pre-emption in Wuppertal. The control centre can directly transmit acoustic and visual information to one or all of the vehicles on the service route. The exact position of the vehicle is determined, evaluated and transmitted to the passenger information boards located at the bus stops using GPS. Passengers at the bus stops are informed in real time about exact arrival and departure times.
Four electric motors influence the driving characteristics of the Citaro. They accelerate the 18m-long bus quickly and almost silently. As no transmission is used, passengers notice no jerking typical of gear changes. The drive output of the wheel hub motors is 320 kW, supplied as required by the battery and the diesel engine driven generator. These electric motors are also used for braking the bus. They then function like generators and convert the brake energy into electric current for the battery. If the battery indicates it requires more power, the diesel engine automatically starts to generate additional energy. In comparison to a bus which runs on diesel only, the engine is only half the size – it weighs only 450 kg instead of 1,000 kg and its engine capacity is 4.8 litres as opposed to 12 litres. At 160 kW, its output is about a third lower.
The energy storage unit used in the Mercedes?Benz Citaro G BlueTec Hybrid is a lithium ion battery. The battery system supplies a maximum of 240 kW and, weighing less than 350 kg, is comparably light. Compared to conventional battery systems, batteries with ion technology impress with a higher energy density in conjunction with a greater storage capacity and lower weight.
WSW mobil GmbH is a subsidiary of Wuppertal Stadtwerke GmbH. The fleet comprises 300 regular service buses operating 65 routes totalling 633.7 km long, stretching from Wuppertal and Solingen via Remscheid to as far away as parts of the Ennepe-Ruhr district.
Ulrich Jäger, MD at WSW mobil GmbH, said: “Hybrid technology is the future for environmentally friendly bus services. It will only be possible to implement the ambitious climate targets of the EU by 2050 if all areas of transport policy are consistently oriented towards environmental protection.”
