Development and Application of CO2 Cascade Air Source Heat Pumps for Space Heating in China
In northern China, space heating consumes 19% of the total energy and emits 22% of the carbon dioxide in the building operation sector. Against the background of China’s “carbon peaking and neutrality” goals, improving building electrification rates and renewable energy utilization rates have become critical development pathways. As a state-of-the-art solution for this transition, the CO2 air source heat pumps (ASHP) are applicable to both retrofitted and newly constructed buildings. Taking distributed heating system projects using CO2 ASHPs as the research object, this paper illustrates the technology’s development status and investigates its operational performance. Analysis of the projects applied in cold and severe cold zones revealed that CO2 cascade ASHPs achieve favorable efficiency, with a seasonal heating COP ranging from 2.24 to 2.92. Moreover, they can operate stably at ambient temperatures around -22? while maintaining indoor temperatures that meet relevant standards. To guide and regulate the further development of such applications, a national standard has been released in response to the growing adoption of CO2 ASHPs in space heating and other heating systems.