Siemens’ Mobility division has been investing significant time and money into developing a comprehensive e-bus system for some time now. Already back in October 2012, its mass produced ‘eBus’, developed and built together with the Italian Rampini, became the first vehicle bus to enter into commercial service in Vienna.
For operator Wiener Linien, this launch marked the debut of its long-term objective to turn two Viennese bus lines 100% electric. Indeed the company has subsequently purchased 12 of these electric microbuses, which are now are fully operational on a daily basis. They recharge either overnight at depots, or during daytime operations using overhead power lines already installed for trams. To connect to this existing infrastructure the buses are equipped with a rooftop pantograph.
Replacing the liquefied petroleum gas (LPG) buses already in service with electric has reduced CO2 emissions in Vienna by 300 tonnes.
Complete system to go
Three years on, in January 2015, Siemens signed a global agreement with Volvo Buses for the supply of complete electrified bus systems to cities. Through the partnership, Volvo will supply electric-hybrid and full e-buses to customers, while Siemens will provide and install its high-power charging (HPC) stations for the electric vehicles.
The two companies, which have been working together for the past three years in the field of electromobility, are clearly stepping up a gear with this complete system offering.
Charge & go
The Siemens’ charging infrastructure includes the station, auxiliary equipment, cabling, civil works, installation, commissioning and maintenance. The new HPC system (capacity of up to 300kW) is designed for fully automatic charging. It enables a number of buses to be charged per hour with one station, since all the necessary electronics are located outside of the vehicle. The stations themselves can be installed at stops along routes, or at terminals, to ensure vehicles are charged efficiently, rapidly, and, importantly, without impacting their operating punctuality.
In November 2014, this HPC was brought into service with the roll-out of a Volvo 7900 Electric Hybrid in the downtown district of Hamburg. Operator Hamburger Hochbahn is now running the vehicle approximately seven kilometres on its Innovation Line 109*, purely under electric propulsion.
“Instead of a trolley bus system, which takes energy from the bus grid when necessary, the HPC eBus technology implies ‘opportunity’ or ‘interim’ charging,” explains Andreas Laske, senior project manager, eBus, Siemens Mobility. And there are two methods for this kind of charging:
- inductive, using an electromagnetic field to transfer the energy
- conductive, requiring a physical connection
“At Siemens we believe in conductive as being the more straightforward,” continues Mr Laske. “It involves low weight vehicle components, proven and safe technology, and implies a lower vehicle cost/complexity. Further benefits are fast charging up to 450kW and efficient energy transfer.”
The operating sequences for charging the eBus are as follows:
1 – Approach
- bus arrives at the charging station and stops under the pantograph. Wireless communication is established via patch antennas mounted on the mast and bus roof
- positioning of the bus: the driver stops at parking reference point and activates the parking brake
- sensors check the position of the bus; the system verifies the parking brake is activiated; if all is OK, the charging process begins
Notification to driver: charging session ‘initiated’
2 – Contact & charge
- pantograph is lowered onto the bus rails until the required pressure is reached, and confirmed
- system checks for positive earthing and safe insulation; if all is OK, the main circuit of the HPC is switched on
- system sends ‘all OK/all safe’ message to the bus, which then closes the insulation circuit to the battery system
Charging begins with continuous insulation and power monitoring
3 – Charge & release
- charging and battery status are transmitted to the driver via a visual display in the vehicle cab
- at ‘battery status 100%’, or at any point, the driver can release the parking brake and so trigger termination of the charging process
- charger lowers the current and opens the charging circuit, switching off the main circuit. The charging process is completed
The pantograph is raised to ‘full raised up’ position; bus leaves the station.
The bottom line
To date, Volvo Buses and Siemens have already delivered three electric hybrid buses and four charging stations to Hamburg. During 2015, the partnership is delivering full electric buses, electric hybrids and charging infrastructure to the Swedish cities of Gothenburg and Stockholm.
There are plenty of expectations riding on the success of this eBus collaboration, namely:
- development of a concept whereby such electric services are integrated with standard operating conditions
- the ‘intelligent’ use of existing infrastructure to reduce installation costs
- establishing suitable battery sizes. “One of the key challenges for this system is battery capacity and weight,” recognises Mr Laske
- making the e-bus practicable and financially viable: the investment required to purchase a fleet of electric, instead of diesel, buses is a significant barrier to uptake; however the operating and maintenance costs are far lower
- creating ‘open interfaces’, i.e. charging stations that can be used by buses from different manufacturers. This factor is especially important, given that few, if any operators choose to lock themselves into a single supplier
A one-year field test in Gothenburg demonstrated that the Volvo 7900 Electric Hybrid enables the reduction of fuel consumption and CO2 by up to 75%, compared to a Euro 6 diesel model. Total energy consumption is diminished by 60%, and the bus runs in electric mode on average 70% of the route. Charging at end stations takes up to six minutes.
Drivers & other road users
“In terms of practicability, we are much further ahead with the eBus than the electric car,” says Mr Laske. Nevertheless open points clearly still exist. One question that needs to be addressed when bringing this type of vehicle into commercial service is driver training. “E-bus drivers have to understand that life will be easier for them, not more difficult. For instance, not having to leave the vehicle during charging.”
Note should also be taken on the ‘noiselessness’ of the e-bus, and whether or not this constitutes a safety risk for other road users. Here one is reminded of incidents (admittedly rare, but sometimes with fatalities) of collisions between trams and cars/pedestrians/cyclists. Yet contrary to public perceptions, the e-bus is not silent; it simply emits fewer decibels than its diesel counterpart. “You will always have the sound of tyre friction,” comments Mr Laske. “But, yes, yes,” he concedes, “the lower noise level of the e-bus certainly is something that will have to be examined at some point.”
HPC reference projects
- In passenger service
- Hamburg: 4 x 300kW
- Hallerad, Sweden: 1 x 300kW
- Project delivery phase
Gothenburg, Sweden: 3 x 300kW
- Testing
Stockholm, Sweden: 2 x 150kW
Wroclaw, Poland: 1 x 300kW
Montreal, Canada: 1 x 450kW
Incentives, incentives
Both Siemens and Volvo are undoubtedly counting on uptake of the e-bus in the near future to seize new business opportunities. Indeed if the technology finally does take off, driven in part by those cities that have committed to becoming ‘emission-free’ by 2020-2025, there will be some lucrative tenders in the offing, e.g. around 1,000 new ‘cleaner technology’ buses for Hamburg alone.
“I am convinced the e-bus is one of THE technologies of the future, and into this we are investing a lot of our experience,” comments Sandra Gott-Karlbauer, CEO, urban transport business unit, Siemens Mobility.
A further e-bus incentive lies in the 200 cities worldwide identified as having one million inhabitants, but no public transport whatsoever. “We have identified this as a key growth area,” adds Ms Gott-Karlbauer, “although which is the right product – bus, tram, or other – naturally depends on various criteria. We advise and consult with cities on how best to address their particular issues.”
Lesley Brown
*inaugurated in December 2014, this line, used by some 15,000 passengers on a daily basis, is dedicated to testing low carbon and ultra-low carbon buses