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Electric bus systems

 

​​VTT is your partner of choice in planning and design of urban electric bus systems as well as electrification of other commercial vehicles and mobile machinery. We support you in all key areas of the process:

  • Electric bus technologies and analysis
  • Charging infrastructure design
  • Traction battery dimensioning and system energy management
  • City planning, electrification strategies and roll-out
  • Complete system design, techno-economic (TCO) optimisation
  • Support in procurement processes
  • Electrification in mining, logistics, port operations, marine vessels

Electric buses suit well for public city transportation, where the driving is predefined as the route length, timetable, daily mileage and operation time. The overall energy efficiency of an electric vehicle consists of the efficiencies of the powertrain components used. In addition to optimising the individual subsystems of the vehicle, the whole system should be studied to find the most suitable components for improvement. In this, finding the optimal control strategy is important. When inspecting a whole fleet of electric buses, the charging system and the bus routes need to be also considered to ensure optimal fleet and energy management.

Planning of electric bus systems


Using our in-house built design tool, it is possible to study the prospects for electrifying the public transportation in a given city. The tool uses basic bus line data together with geographical information of the route to generate a driving cycle to represent the desired bus lines. The energy consumption on a given route is calculated using our electric vehicle simulation model.

It is possible to study optimal locations for charging stations and strategies for charging. Dimensioning the capacity and power for the battery and for the charging stations is possible. In addition, effect of the charging strategy on the battery lifetime can be predicted.

Scalability and roll-out strategies for electric can be analysed with the geographic design tool as well. This includes selection of bus lines to be electrified, scalability of the charging infrastructure for cost-optimal system design.

With the aid of our total cost of ownership (TCO) model, the total costs incurring from owning and operating fleets of different electric buses in comparison with conventional diesel buses can be calculated. Different scenarios and systemic arrangements can be reviewed with the well parametrised model together with the vehicle and bus system models. Sensitivity analyses reveal dependencies on parameters such as daily mileage (utilisation rate), battery type, price and lifetime. This supports in finding optimal solutions for electrification.

PICTURE

​​Simulations for electric vehicles


Using a multi-physics modelling approach, the whole vehicle is modelled and simulated as a system to study the optimal configuration for maximum energy efficiency. The cost minimal solution is found with right dimensioning of the components.


Thermal management to utilise the waste heat flows of the powertrain components together with the cabin heating and cooling is included. Finding optimal control strategies that take into account also the non-controllable environment properties such as outside temperature can be achieved. The modelling is supported by testing on a prototype fully electric city bus and more specific computational fluid dynamics modelling.

 

 

 


 

 

 

 

 

 

 

Subsystems of the electric bus model. Route and duty cycle information is used as an input data for the model.

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VTT’s own prototype electric bus is an open R&D platform on electric commercial vehicles (ECV) in different public and confidential projects and activities from components to system-level living labs, in close co-operation with industry and public stakeholders. Our research topics include the following:

  • performance evaluation
  • development, optimisation and validation of the electric powertrain and components
  • traction battery systems and hybrid power sources with fuel cell range extender
  • control of in-vehicle subsystems and components
  • system-level IoT
  • driver’s aid systems
  • electric vehicle fleet and energy management.

The hands-on prototype combined with our modelling and simulation capabilities serve as a comprehensive platform for the electrification of commercial vehicles and machinery. In addition to public transport and buses, this is highly relevant, for example, in the development of electric and hybrid mining, port operations, logistics and marine vessels.


Heavy-duty vehicle test facility at VTT enables simulation of driving in controlled laboratory environment for maximum accuracy and repeatability.


ECV – electric commercial vehicles eBus project on electric bus technology 2012 – 2016.

HSL Helsinki Region Transport, pre-commercial pilot on urban electric bus systems 2016 – 2019.

 M. Pihlatie et al, Fully electric city buses – the viable option, http://www.vtt.fi/inf/julkaisut/muut/2014/OA-Fully-Electric.pdf

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