Carbon mitigation potential of the new energy bus thermal management systems with the international ban of hydrofluorocarbons

To address carbon emissions from transportation, this study develops an integrated thermal management system for electric buses using natural refrigerant CO₂ (CO₂-TMS), designed to replace conventional high-global-warming-potential refrigerant R407C (GWP = 1980). Against the backdrop of the global phase-out of hydrofluorocarbons (HFCs), the system leverages CO₂′s eco-friendly properties (GWP = 1) and integrated thermal management technology to significantly reduce direct carbon emissions and enhance energy efficiency, which is crucial for achieving carbon neutrality goals. Current research predominantly focuses on passenger vehicles, leaving a gap in comprehensive thermal management systems tailored to the fixed-route operations and strong regional climate dependencies of buses, alongside a lack of nationwide quantitative carbon emission analysis at the municipal level. To bridge this gap, we employ the China Heavy-Duty Commercial Vehicle Test Cycle (CHTC-B) as the benchmark, combining experimental and simulation methods to compare the thermodynamic performance and environmental impact of R407C, basic CO₂ (Basic-CO₂), and CO₂-TMS systems. Core innovations include: (1) a multi-mode cooperative design (six operation modes dynamically adapting to thermal demands); (2) a Life Cycle Climate Performance (LCCP) model covering 344 Chinese cities. Key findings reveal that CO₂-TMS elevates heating COP by 112 % over R407C at −30 °C (with 16 kW waste heat recovery further boosting COP by 17.65 %), extends driving range by 27.0 % (−30 °C) and 9.6 % (28 °C), and achieves nationwide LCCP reduction of 89,370 kilotonnes (average reduction rate: 7.68 %, 21.37 × that of Basic-CO₂). This work provides quantitative evidence and theoretical support for low-carbon thermal management in buses.