Simulation-Based Investigation and its experimental Validation of the Thermal Behaviour of a Battery Electric City Bus

Electrification of city busses is an important factor for decarbonisation of the public transport sector. Due to its strictly scheduled routes and regular idle times the public transport sector is an ideal use case for battery electric vehicles (BEV). In this context the thermal management has a high potential to decrease the energy demand respectively to increase the mileage of the vehicle [1]. The thermal management of an electric city bus comprises the thermal behaviour of the components of the powertrain, such as engine and inverters, as well as the conditioning of the battery system and the heating, ventilation, and air conditioning (HVAC) of the drivers’ front box and the passenger room. The focus of the research is the modelling of the thermal management of an electric city bus in MATLAB/Simscape including real world driving cycles. The heating of the components, geometry and behaviour of the cooling circuits as well as the different mechanisms of heat transfer are modelled analogue to the real system. The goal is to find synergy effects within the different components to improve the overall energy efficiency. Additionally, a test setup is built on the institutes’ power and inertia simulator test rig including all relevant components of an exemplary electric powertrain for validation of the simulation model. Results are presented, which show that the thermal behaviour of the system can be modelled with high accordance to the real system. Moreover, synergy effects are identified for improving the thermal energy flows with the goal of reducing the overall energy demand. [1] Rehm, D., Krost, J., Meywerk, M., and Czarnetzki, W., “Optimization-Based Battery Thermal Management for Improved Regenerative Braking in CEP Vehicles,” SAE Technical Paper 2024-01-2974, 2024, doi:10.4271/2024-01-2974.