Driving range evaluation based on different cabin thermal management goals of CO2 heat pumps for electric vehicles

Improving driving range is very important for electric vehicles (EVs). The use of CO2 heat pumps to replace Positive Temperature Coefficient (PTC) heaters for cabin heating is one of the most efficient choices for improving driving range in EVs. The combination of CO2 heat pumps and electric vehicles matches well with the social requirements of low-carbon, cleaner production, and sustainable development. However, heat pumps may frost under a conventional optimal discharge pressure control, resulting in a rapid drop in driving range. To solve this problem, the impact of frost on the driving range under different ambient conditions was assessed, and the failure of performance guarantee under conventional control in frost-prone conditions was deeply studied. Based on the experimental data, a heating capacity decline map was developed, and a new global performance improvement control method was proposed. Moreover, the dynamic characteristics between optimal discharge pressure control and the new control process were experimentally compared. Furthermore, a comparative analysis of driving range improvement under the global performance improvement control was carried out in three cities with typical climates. The results indicated that driving range improvement of the new method could be even as high as 10% in some conditions. Finally, the global performance improvement control method was recommended in regions with low ambient temperatures and high humidity.