Experimental study on phase change heat storage of valley electricity and economic evaluation of commercial building heating

Abstract

• A composite PCM of Mg (NO 3 ) 2 6H 2 O/NaNO 3 for an electric boiler was developed. • A modular PCHS unit was constructed and tested, showing stable heating performance. • The heating tests in commercial buildings show 53% savings in operating costs. • The valley power PCHS heating technology shows good application prospects. The application of valley power phase change heat storage (PCHS) in commercial building heating has practical significance for the city's sustainable development. In this study, the experimental study on valley power PCHS is carried out, focusing on the winter heating of a commercial building. An inorganic hydrated salt phase change material (PCM) of magnesium nitrate hexahydrate and sodium nitrate (mass ratio, 92:8) with a phase change temperature of 80–83 °C for an electric boiler was developed. A modular PCHS unit was constructed and tested for 2.5 months from 2018 to 2019 and 4.5 months from 2020 to 2021. The results show that the PCM is stable at about 81 °C after 240 cycles. Moreover, the heat storage and the exothermic power of the PCHS unit reached 10.95 kW and 10.15 kW in the 9-hour test, respectively. The 12-day trial of an office shows that the indoor temperature was maintained at 22–24 °C stably during the daytime working hours (7:00–17:00). Furthermore, the two-year test of the building heating shows that the valley power PCHS can effectively adapt to the outdoor environment changes. The power consumption of the PCHS unit has a negative linear correlation with the ambient temperature. In addition, the operating cost of the PCHS unit system is only 3.5 RMB/month/m 2 , which is less than half of the municipal central heating system cost of 7.5 RMB/month/m 2 , reflecting good economy, and the advantages of energy-saving, emission reduction, and environmental benefits are obvious. The findings of this study provide a valuable supplement for the heating mode and low-carbon energy utilization of urban buildings.