Winter driving range optimization of electric bus based on CO2 thermal management system and thermal energy cascade utilization

Abstract

Environmental pollution and the energy crisis are intensifying. Pure electric vehicles (EVs) are promising alternatives to traditional internal combustion engine vehicles (ICEVs), but a significant decrease in winter driving range challenges their adoption. This paper proposes an integrated CO₂ thermal management system with a waste heat recovery mode(WHR-CO₂ TMS) for buses, addressing cabin, motor, and battery thermal management. By harnessing motor waste heat and preheating the battery, we optimize winter driving range. The study compares four systems between −20 °C and −10 °C: PTC heating system, CO₂ heat pump system, WHR-CO₂ TMS, WHR-CO₂ TMS with battery preheating. Key findings include: a. Replacing PTC heating system with a CO₂ heat pump system increases driving range by 10.37 %–12.90 %. b. Motor waste heat recovery enhances CO₂ heat pump performance, increasing COP by 6.97 %–11.13 %, and improves driving range by 19.14 %–20.90 %. c. Preheating the battery reduces range decay by 8.73 %–13.26 %, leading to a range improvement of 19.47 %–21.60 % compared to PTC heating system. d. A scheme is proposed to adjust battery preheating based on driving distance and ambient temperature. The results highlight the potential of integrated TMS for enhancing the winter driving range of electric buses.