Modelling and simulation of HVAC energy demand in battery electric rail vehicles for the evaluation of operational strategies and heat pumps

Abstract

The transition to battery electric multiple units (BEMUs) focuses on reducing carbon emissions and ensuring environmental sustainability in rail transport. A major factor influencing the range of BEMUs is the energy demand of the heating, ventilation, and air-conditioning system (HVAC) during catenary-free operation. This thesis aims to evaluate the energy demand of the HVAC system of battery electric multiple units with the implementation of heat pump integration and HVAC control strategies under different operating and environmental conditions. A Python-based simulation in the thermal car body model (TCBM) was carried out to examine the effect of HVAC energy demand under various factors, including environmental conditions, passenger load, heat pump efficiency, and the implemented HVAC control strategies. The applied TCBM model is validated by comparing simulated results with real-world data to improve the accuracy of HVAC energy demand in battery electric trains. The HVAC energy demand of electric resistance heaters and heat pumps with different refrigerants, such as propane, carbon dioxide, and air, is evaluated at electrified and non-electrified routes. The optimised HVAC control strategy was implemented in the model to reduce the energy demand by the HVAC system during catenary-free operation with onboard battery storage. The results demonstrate a reduced energy demand for heat pump-based HVAC systems compared to electric resistance heating during heating operation. The comparison of refrigerants denotes the refrigerant with higher efficiency showcases a lower energy demand for the HVAC system in both heating and cooling operations. The optimised HVAC control strategy ensures a reduction in energy demand during non-electrified routes. The thesis highlights the importance of heat pump-based HVAC systems over electric resistance heaters in BEMUs. The potential of the coefficient of performance of refrigerant and the optimised HVAC control strategy during non-electrified routes are also defined in this thesis. The overall thesis highlights the importance of heat pump integration and an optimised HVAC control strategy to increase the range of BEMU by reducing the energy demand of the battery electric rail vehicles to support the large-scale implementation of sustainable rail transport.