Since 31 October 2019, four battery-operated trolley buses (BOB) are running on the 695 line in regular service. The Meigen-Gräfrath connection is the first BOB line in Solingen. It is now up to BOB to show that it is a real alternative to diesel buses in everyday deployment on this heavily frequented pilot route.

In order to examine this over a scheduled five year project, the BOB project will be funded in the amount of 15 million euros by the Federal Ministry of Transport and Digital Infrastructure in the framework of the Mobility and Fuels Strategy of the Federal Government (MFS).

Towards more flexibility with an integrated battery

Trolley buses have been running in Solingen since the 1950s. The vehicles are powered by electric engines and get their electricity from a contact wire. In order to also be able to operate short routes without overhead cables, most of the buses are equipped with a diesel generator. Increasing levels of fine dust pollution in cities are making electric drive concepts more and more important.

As a first step, the changeover of the 695 diesel bus line is implemented, after which the pilot project is expanded over the medium term to 20 battery trolley buses to be deployed in Solingen. When this is successful, the entire city’s bus fleet is to be gradually converted. The special feature of electric vehicles is that they have both a battery and modern control technology. This allows them to be on the one hand, charged during operation at the contact wire (in-motion charging), and on the other hand to also cover route sections not fitted with a contact wire. The buses feature even more advantages: the batteries help to balance out fluctuations caused by electricity from renewable energy sources. The entire overhead cable infrastructure will be closely linked to the city’s power distribution network in future.

Gradually towards a sustainable, urban complete system

Until now electricity only flows from the power distribution network into the overhead network. In future power flow will also be possible from the overhead network back into the electricity distribution network. This is exciting because photovoltaic systems will be connected directly to the overhead network as part of the project. As these will be operated with direct current, conversion losses will be avoided through the direct feeding-in of solar energy. It is envisaged that only locally-produced green electricity will be produced in the local transport in Solingen. The project also uses the old batteries of the buses in order to stabilize the overhead cable network. Through intelligent charging and energy management, current load peaks or green electricity production peaks can be absorbed in the overhead as well as the electricity distribution system. Thus the integration of fluctuating renewable energy sources can be improved overall. Furthermore officials are planning to connect charging columns for private households to the overhead system.