The goal of reducing the global CO2 emissions requires actions especially for the transportation sector. To achieve the goal, electric traction motors are frequently implemented in passenger vehicles as well as in commercial vehicles like heavy-duty trucks or buses. Particularly electric city buses have the potential to reduce the local emissions in urban areas and provide local exhaust-emission-free mobility. While their number of registrations rises, research focusses on the improvement of the overall system in order to increase the energy efficiency. High importance is gained by the thermal management of the whole system. This research describes and investigates a simulative approach to improve the thermal management and therefore the energy efficiency of an electric bus system. The different thermal components of an electric city bus like drive system, battery system and heating, ventilation and air conditioning system (HVAC system) are modelled. Their thermal behaviour has been validated in previous research [1]. Based on the validated model this study proposes an improved thermal management that, state-dependent, combines the thermal circuits of the single components to reduce the overall energy demand. Cooling or heating is provided by the HVAC system. Furthermore, the simulation utilizes real driving cycles of a city bus in Hamburg area. Measurement data from an entire year are examined by a cluster analysis that results in typical application profiles for urban bus traffic and are used as basis for further research.
Results are presented, which show that the overall energy demand decreases due to a improved, application cluster profile-dependent thermal management system. An operating strategy for the thermal management of an electric city bus under real driving conditions is developed using the simulation model.
[1] Schäfer, H., Meywerk, M., and Hellberg, T., "Simulation-Based Investigation and its Experimental Validation of the Thermal Behaviour of a Battery Electric City Bus," SAE Technical Paper 2025-01-0266, 2025, https://doi.org/10.4271/2025-01-0266.