Automotive heat pump systems with the R134a refrigerant cannot provide sufficient heating capacity and even stop working in a low ambient temperature. Developing a transcritical CO2 automotive heat pump system would be an effective method to solve this problem. This study theoretically analyzed the impacts of key factors on the performance of a CO2 heat pump system

and experimentally investigated the developed heat pump in a ﹣20 ℃ environment. Experimental results showed that the developed heat pump system ran stably at low temperatures and had a good heating performance. Under the same compressor speed

the indoor environment temperature had a greater impact on the heating coefficient of performance (COPh))

while the outdoor environment temperature had a greater impact on the heating capacity. Under a cold condition at ﹣20 ℃

the COP reached 3.15 and the heating capacity reached 3.6 kW. When the indoor inlet and outlet air temperatures are 20 ℃ and 40 ℃

respectively

the COPh was at least 1.72. Therefore

compared to R134a

the CO2 heat pump system has a great heating performance in a low temperature environment

and thus has good application potential for electric vehicles.