Using tram infrastructure to re-charge e-buses in Oberhausen (Germany)

First published 12/04/2017

 

The public transport operator of German city Oberhausen (Stadtwerke Oberhausen) is taking part in the H2020 project ELIPTIC (Electrification of public transport in cities) which aims to show how costs and energy can be saved by electrifying public transport and optimising the use of existing infrastructure and rolling stock.

In Oberhausen, two use cases will showcase e-buses using existing electric public transport infrastructure and how this infrastructure can be used for multi-purpose services. In this sense Stadtwerke Oberhausen operates two e-bus lines, each with a battery bus. One e-bus is charged from a sub-station of the tram (the charger has an output of 200 kW and could therefore also charge other buses), and the other one takes energy directly from the contact line. Monitoring and evaluation of these demonstrations will contribute to the use-case implementation as well as technology, business case and development schemes assessment in the project.

Context 

In urban bus systems like in Oberhausen - which is a medium-sized city within the so-called Ruhr Metropolis in the west of Germany - mostly diesel vehicles are currently in operation. To reduce the dependency on fossil fuels and to reduce the nitrogen oxide, particulate matter and noise pollution in urban areas, the public transport operator Stadtwerke Oberhausen GmbH (STOAG) is trying to introduce alternative urban bus drive systems.

Public transport by buses and trams plays a central role in the mobility concepts of the future in the city of Oberhausen. To meet the rising demand for mobility without negative effects on the environment, STOAG in co-operation with transport association Verkehrsverbund Rhein-Ruhr (VRR) on 4 October 2015 started the operation of the two urban lines 962 and 966 with an electric bus (12m standard) on each line and hence completely converted both routes from diesel to electric mode.

In action 

For fast charging, the existing DC tram infrastructure is used to charge the battery buses in operation. The required charging stations were built in late July 2015 at the Oberhausen-Sterkrade train station (line 962) and the Neumarkt station (line 966). In Sterkrade, the power is taken from the tram catenary by a pantograph installed on the roof of the bus, and at the Neumarkt station the charging energy is taken from the tram sub-station. Each charging operation takes place during the turning times at the terminus station and takes up to 10 minutes. During regular operation, charging at the depot is not required.

The charging energy for line 962 is taken from the tram catenary at Sterkrade train station (see figure below). This solution is especially used in the immediate vicinity of the tram catenary where several waiting positions for electric buses are available and sufficient space for the implementation of charging devices for electric vehicles of other means of transport is available.

 

Source: Müller-Hellmann

For line 966, the charging energy is taken from the sub-station at Neumarkt station (see figure below). This solution not only has the advantage of sharing the existing medium-voltage switchgear, the converter transformer and the rectifier of the sub-station, but also allows the weather-proof placement of the charger in the sub-station. Hence, there is no additional space (probably subject to approval) required, except for the mast and integrated charging device.

 

 

Results 

The electric bus costs around € 300 000 more than a conventional diesel bus. In case of Stadtwerke Oberhausen, the two buses were funded through the transport association Verkehrsverbund Rhein-Ruhr (VRR). Furthermore, investment costs for the charging infrastructure at both termini need to be taken account by € 500 000 each.

The electricity the electric buses use comes from a renewable energy mix. The energy consumption per bus was 1.5 kWh/km and by this replaced emissions from the diesel: 80t less CO2 per year.

The buses run in average about 303 km (line 962) and 204 km (line 966) per day. Maintenance costs for both lines are reported to be about € 2 000. 

Challenges, opportunities and transferability 

The operation of e-bus lines 962/966 is continuing to be successful. There were only small disruptions which could be solved by technical staff in a short time period. The parking situation at the Sterkrade train station is difficult for the drivers. The contacts of the ‘pantograph up’ charging system aren’t working well especially because of lower outside temperatures. Besides, it became obvious to look in more depth in the security and safety aspects of the technical functionality of the charging system and handling of the e-buses and interaction with the charging infrastructure. There are also future plans to electrify another line together with the neighbouring public transport operator.

In Depth 

• STOAG: Elektromobilitaet (in German)