A phase change heat storage device was designed and built based on a spherical unit.The hot water storage tank is the core equipment in the solar heating system,and the heat release performance of the water tank directly determines the overall operating efficiency of the energy storage system.The heat release experiments of the spherical unit heat storage device were carried out by using single control variable method,and the temperature change curves were obtained and analyzed.The results show that when the water tank space is constant and the phase change materials are basically the same,the number of spherical phase change units has greater impact on the heat release efficiency of the device;changing the interlayer spacing between the units has less impact on the heat release efficiency of the device;the change of inlet temperature and inlet flow rate has greater impact on the heat transfer efficiency of the device.