Air-source heat pump heating system with a new temperature and hydraulic-balance control strategy: A field experiment in a teaching building

Owing to the government's policy of clean-energy heating reform, air-source heat pump (ASHP) heating projects are growing rapidly in number in China, and an efficient operation mode for this type of heating system has become an issue for researchers. In this study, a new temperature and hydraulic-balance control strategy is proposed for ASHP heating systems. This strategy utilizes the cooperation of three different devices: room thermostats, pressure independent balancing and control valves, and a differential pressure relief controller. Two almost identical ASHP heating systems in areas A and B of a teaching building, one with the new control strategy (system A), were field tested. The operation mode was divided into two periods of school terms with a return water temperature of 35 °C for heating and winter vacation with a temperature of 20 °C for frost protection. Through a 67-day monitoring of operating performance, the results showed that system A could not only realize a more suitable indoor temperature, but also provided on-demand heating with the setting of thermostats. This new control strategy will not affect the COP of ASHP. Compared with system B, a significant energy conservation achievement of 38.6% heat savings and 31.5% electricity savings was achieved for system A during the school term. Moreover, the static payback period for the devices of the new control strategy is only 1.46 years. System A can realize a further positive environmental benefit with a 37.2% reduction in emissions.