What does Electro-Hybrid mean? The conventional overhead line bus, which until now was fitted with a 53 kW auxiliary diesel motor from the company Deutz, is now purely electrically driven. A traction battery with a capacity of 52 kWh renders it possible for the bus to function electrically even when not in contact with the overhead line. Why then the term „hybrid“? We use this term because the electricity for the system is produced in two different manners.
Whenever it is possible for the bus to access the overhead line, it draws electricity for the motor and all auxiliary equipment such as heating, lights, etcetera from the overhead line. At the same time, the battery is loaded. As soon as the rod is no longer touching the overhead line, the bus switches into battery mode and can continue on its route without any significant interruption. During this time, surplus kinetic braking energy is converted into electric power and fed back into the battery. At the next bus stop, the push of a button causes the rods to find the overhead line, and the battery is once again loaded without unnecessary time consumption.
This huge project was financed by the Baden-Württemberg Ministry of Transit and the greater Stuttgart region into several million euros, with each bus costing approximately 970.000 euros. The project was headed by Esslingen City Transit (Städtische Verkehrsbetrieb Esslingen) and joined by the battery producers Vossloh-Kiepe from Düsseldorf and bus manufacturers Solaris. Production was based on a study carried through by the Fraunhofer-Institut in Dresden (IVI), which was conducted with Esslingen University to determine the expected energy and capacity needed to conduct the vehicle. The results of this study were decisive in calculating the dimensions of the traction battery.
We are very proud that for the four years of this project, students of the Esslingen master’s programmes were active in developing the specifications for the new Electro-Hybrid Bus in Esslingen. Wolfgang Hechler, Quentin Burdel, Michael Barth and Marius Müller will soon enjoy seeing a vehicle that they helped to develop driving through our city streets.