Abstract: The composition and operation principle of direct expansion variable frequency solar heat pump hot water system are introduced. The fixed frequency method is used to analyze the operation rules and characteristics of solar water heater. The system performance is raised on the basis of ensuring the user 's demand for heating water. According to the difference between the actual heating capacity and the expected heating capacity, the operating frequency of the inverter compressor is adjusted to realize the heating time and the heating efficiency of the control system. The feasibility of the method is verified by data analysis and experimental verification.

Key words: Direct expansion type, Solar energy heat pump, Variable Frequency