The traditional trolley bus conference in Europe is called “trolley:motion”. This year Andreas Heuke from Volvo Bus made a contribution. The message was clear, Volvo will be providing different technologies for different types of partial or full electric operation.
With the risk for oversimplifying, minimizing the cost falls back on the main cost contributions which for hybrids and battery buses are:
1, Cost for the driver
2, Cost for the Bus
3, Cost for charging infrastructure
4, Cost for energy storage
5, Cost for fuel/energy
It does not take long to realize that the characteristics of the bus route will have impact on which technology will bring the lowest cost.
The main rout characteristics are:
1, Rout speed
2, Rout topography
3, Number of buses per hour
4, Time table: Idle time/stop time
Prof. Arnd Stephan from TU Dresden addressed this complexity in his presentation. Furthermore, it was shown that already today coaches for intercity traffic provide the lowest energy use per passenger kilometer, also when compared to other means of transports such as trains. The bus and coach technologies already have a very favorable starting point when it comes to future demands for energy efficiency in the person transport sector. What Volvo and our customers have found is that the Volvo 7700/7900 hybrid technology is very robust and delivers high savings at all conditions.
Now, when applying the complexity described above on future public transports. It is clear that there will not be only one vehicle technology dominating, in the same way as diesel engines have dominated in the past. Our analysis shows that several technologies will gain advantage in for different boundary conditions. Hybrid buses will be preferred in an increasing number of operations where the traffic density (i.e. number of buses per hour) is not sufficient to finance charging infrastructure for plug-in and electric buses. If the future electric bus is a trolley bus with a complementary battery or a battery bus with opportunity charging will stay a subtle debate in some circles.
In the future, to realize the lowest cost for a certain operation under the typical cost conditions above, plug-in buses (in the meaning that a part of the energy is charged from the electric grid, irrespectively of how the transfer to the bus is arranged) have a strong advantage providing both the efficiency of the electric bus but also the versatility of the infrastructure “independent” conventional diesel bus.
In some areas a dogmatic approach may develop while in other areas a more pragmatic approach will lead the way.