Research on the characteristics of CO2 heat pump integrated with thermal energy storage for space heating

The CO2 air source heat pump (ASHP) has been widely used for space heating and domestic hot water because of its energy saving, high efficiency and environmental protection. However, when used for space heating, the high return water temperature causes higher throttle loss, which results in the energy efficiency of the system obviously decreasing. To solve this problem, a CO2 ASHP integrated with thermal energy storage (TES) is proposed in this paper. A simulation model of the system was established by TRNSYS software, and the operating characters of the studied system were investigated under the typical daily operating conditions. Additionally, its performance was compared with the benchmark system. This research shows that the average unit COP of the studied system was increased by 14.1 % compared with the benchmark system. It indicates that TES is beneficial for promoting CO2 heat pump application in cold areas.