Evaluation of waste heat recovery of electrical powertrain with electro-thermally coupled models for electric vehicle applications

The mile range of an electric vehicle (EV) may be reduced significantly in cold weather owing to the energy demand for meeting thermal comfort in the vehicle cabin, as waste heat from a combustion engine is not available for this purpose. Various heat pump-based heating, ventilation, and air conditioning (HVAC) systems can be employed to absorb the heat energy from the surroundings and/or the waste heat from the electrical powertrain to facilitate cabin thermal comfort, thereby extending the EV mile range. However, there is a lack of research on the electro-thermally coupled modelling and evaluation of the thermal performance of HVAC systems. This paper proposes electro-thermally coupled models for the electrical machine and inverter by modelling the key electromagnetic quantities as functions of the torque and speed based on offline parameter extraction from two-dimensional electromagnetic finite element analysis. The proposed electro-thermally coupled models, which are computationally efficient, are integrated into HVAC thermofluid simulation. Comparative studies of three heat pump-based HVAC architectures (conventional ambient heat only, waste heat only, and dual heat source) are performed using the proposed electro-thermally coupled models. The dual heat source HVAC architecture exhibits superior thermal performance over its counterparts in cold weather conditions.