Study on performance of a multi-heat source heat pump coupled energy storage system for plant factory heating system

• The MHSHP coupled with thermal energy storage was implemented in plant factories. • The MHSHP was studied under different user-side parameters by experiment. • The MHSHP demonstrated superior the CASHP system in thermodynamic performance. • MHSHP system control temperature with deviation by 0.4 °C. • Raising COP of CASHP and GSHP decreased CO 2 emission by 56.6% and 69.2%. CO 2 air source heat pump (CASHP) faces challenges of performance degradation caused by the high return water temperature and the low ambient temperature for building heating. This study proposed a novel multi-heat source heat pump system (MHSHP) that combined with a CO 2 air source heat pumps (CASHP) and ground source heat pumps (GSHP) with the implementation of a thermal storage tank. The performance and CO 2 emissions of both CASHP and MHSHP systems were investigated by applying a plant factory located in Beijing, China. The effects of user-side parameters and ambient temperature were explored with the storage water temperatures ranging from 20 °C to 40 °C. The results demonstrated that the heating performance of the CASHP improved with an increase of user water flow rate and ambient temperatures, while it decreased as the storage water temperature increased. At the flow rate of 1.1 m 3 /h, the increase of the compressor frequency from 40 Hz to 60 Hz led to a significant improvement in heating capacity by 53.3 %, and a reduction in COP by 23.3 %. When the user-side water flow ratio decreased or the total flow rate increased, the COP of the MHSHP system showed improvement and outperformed that of the CASHP system, with an increase ranging from 46.9 % to 61.5 %. Additionally, it exhibits reduced sensitivity to ambient temperature fluctuations, resulting in a decrease in COP variability from 33.3 % to 20.6 %. Moreover, the CO 2 emissions of the system decrease as the COP increases, with significant reduction of 69.2 %.