Study on low temperature phase change heat storage and its performance of solar and air source heat pump system

In view of the deterioration of the performance of air source heat pump at low temperature in cold regions and the large fluctuation of solar heating systems, a heat pump system with low-temperature heat storage using sodium chloride aqueous solution as the phase change thermal storage material is proposed. The system form and its operation scheme, unit energy consumption model and economic evaluation index are given. The influence of different concentrations of sodium chloride solution corresponding to different heat storage temperatures and different areas of solar collectors on the system operation economy is studied, and simulation analysis and optimization are carried out and the operation efficiency and operation economy of the system are analyzed with an actual residential building in a cold region as an example. The results show that with the increase of collector area, the lower the sodium chloride concentration, the higher the heat storage temperature and the higher the coefficient of performance (COP) of the system; the larger the collector area, the higher the COP of the system, but the payback period decreases first and then extends with the increase of the collector area. When the system sodium chloride solution concentration is 5.3% and the collector area is 372m(2), there is a minimum payback period for the winter heating of 3000m(2) building in this case, and at this time, the COP of the system is 2.37, which is 20% higher than that of the traditional air source heat pump. The payback period of the system is 7.7 years, and the contribution rate of the solar collector system is 53%. The solar air source heat pump system with low temperature phase change heat storage significantly improves the operation performance of the system and has good energy saving benefits.