PSI Blog

E-Mobility: Sustainable Software Concepts for Emission-Free Bus Fleets

20 Sep 2019 - Transport, Artificial Intelligence, Energy, Sustainability

The need for intelligent software concepts to support electromobility is also growing in public transport. Source: petovarga/
The need for intelligent software concepts to support electromobility is also growing in public transport. Source: petovarga/

Experts say there are about 22,000 diesel buses still currently on the road in German cities. And this number is decreasing every day. That is because an ever-increasing number of cities and municipalities are investing in buses with alternative, emission-free drive systems and are striving for completely "green fleets." This development is supported by the deployment of intelligent software concepts that consider and control the new links and processes connecting charging logistics, dispatching and route planning.

Currently, 45 German cities are testing electric buses. Their long-term goal is to operate their vehicle fleets everywhere economically. However, there are still reservations about cost-effectiveness, range and charging infrastructure for a large-scale interconnected operation.

The fact is: Companies counting on alternative drives for the future face major challenges. Inevitably, this requires changes to their operational processes – including the accompanying IT systems.

IT systems as a driver for emission-free driving

These can even become a driver for the use of emission-free vehicles and intelligently compensate for the lack of maturity of most alternative drive technologies, in this way already making them economical today.

The software supplier PSI Transcom is regarded as a pioneer in the world of service providers.  The Berlin-based company has designed a depot management system especially for emission-free fleets (PSItraffic/E-BMS) that has already been used successfully.

Plug-in charging station on Solaris bus. Source: HOCHBAHN
Plug-in charging station on Solaris bus. Source: HOCHBAHN

The system not only factors in the required interrelationships of the different drive types: Since as a rule, fleets can only be converted successively, the integration of different drive types becomes a realistic scenario. It therefore supports both parallel operation during migration and the possibility of mixed operation in the future.

A question of the right charging

When it comes to green fleets, operators must first decide between an overnight charging at the depot and “opportunity charging” along the route.

This also impacts the controlling software systems. For example, with a growing fleet of electric buses and a large network, the arguments for overnight charging are obvious. Construction only affects the depots and not the overall urban infrastructure, changes to which usually requires extensive permits.

Advantages of "Overnight Charging"

  • No restrictions for citizens in everyday life
  • Construction only affects the depots and not the overall urban infrastructure
  • No permits required for installation areas
  • Significantly lower costs for the company
  • Charging the entire fleet can be centrally controlled and the energy supply intelligently managed

Charging at the depot: A focus on safety and efficiency

Safety aspects also play a central role – more so for hydrogen fleets than for electric buses, because supplying them economically requires large tanks. Of course, these cannot be distributed across a city. And even central depots carry risk here. Finally, the power supply required for individual charging stations along the entire network is only available in a few cities – let alone in rural areas.

With depot charging, charging the entire fleet can be centrally controlled and the energy supply intelligently managed. This means an additional, decisive cost advantage.

A guarantee for being on time: Correctly calculating battery capacities

In the future, depot management systems will primarily have to balance the interrelationship between the vehicles’ state of charge, remaining range and the number of routes that can be travelled – independent of overnight or opportunity charging.

For example, PSItraffic/E-DMS automatically determines which vehicles at the depot best match which open routes after how many minutes of charging. To achieve this, vehicles continuously send the corresponding state data to a server. This logic can be applied to any drive type.
This is also the context for so-called charging and load management, which ensures an optimal charging strategy.

Charging and load management: The advantages at a glance

  • Specification of the vehicles required for charging through the block planning
  • Control of charging based on predicted energy demand
  • Control and monitoring of all charging processes
  • Demand-oriented assignment of the vehicles to charging station
  • Charging just as needed
  • Demand-oriented distribution of the available connected load
  • Consideration of all operational requirements, e.g. upcoming workshop orders

In PSI's E-DMS, this aspect was integrated into the system as a "smart Power" module.
This module is essential to ensure that not all vehicles are charged simultaneously and – in the case of electric vehicles – are not even charged to full battery capacity, among its other functions. Here, the automatic functions described, such as the continuous adjustment of charge state and remaining range with the open circuits, become active. On the other side of the equations, the amount of energy available from the power grid is also recorded.

Not every bus needs its own charging station. In this way, the existing charging hardware can be used in a budget-friendly way, and available capacity and resources can be used optimally.

Predicting energy demand thanks to intelligent technology

Charging stations: In PSItraffic/E-DMS, these are automatically controlled by the charging management system according to demand. The system works not only with the current status, but also with forecasts.

The module forecasts the total energy required to charge the vehicle fleet throughout the day. Artificial intelligence methods are also used for this purpose. Energy demand is calculated by the E-DMS using all constant master data for individual vehicles. Influences such as outside temperature, battery type and battery age are included in the forecast, since they affect charging capacities.

Monitoring and control of the charging infrastructure in the Smart Power module. Source: PSI AG
Monitoring and control of the charging infrastructure in the Smart Power module. Source: PSI AG

Based on this information, the system then develops a logical charging strategy which allows statements to be made about the number of routes at a certain minimum daily temperature that can be expected, among other things. In addition, the E-DMS also enables projections to be made for energy demand throughout the next day, how and when charging should be performed, and when which vehicles will be ready for operation.

In this way, optimised charging concepts are created that build on the currently available electrical grid capacities. In the future, data for costs and capacities on the energy market could also be included in such calculations.

The fact is: Public transport companies are evolving. There is little time for doubt or waiting for mature drive technologies. IT systems that use intelligent automatisms and algorithms to allow both gradual migration with parallel operation and the perspective of mixed operation appear even more valuable. Corresponding systems are already, and their practicality is being proven in early projects.

Futher information on depot and charging management for electric buses

Eric Nöh

Head of Sales Public Transport
PSI Transcom GmbH
Phone: +49 30 2801-1680