At this point, the solar system is in standby mode, the heat pump unit alone work on the hot water tank heating. 3 solar-heat pump central hot water system design 3.1 solar assisted heating air-source heat pump unit to determine the power of solar-heat pump central hot water system, solar assisted heating air source heat pump unit in sunny weather as a solar collector system auxiliary heat source equipment in When the solar energy resources are insufficient or rainy weather as the main heat source of the system to ensure the normal supply of hot water, so the heating power should be in accordance with the design of the entire hot water system to determine the heat load. For the full-time central hot water system, the heat pump unit power is determined according to the hourly heat load of the hot water system. For the part-time central hot water system, the power of the heat pump unit should be based on parameters such as maximum water consumption, hot water tank volume and heating time To determine, see specific reference [9]. The rated heating power of the heat pump unit is not less than the design load of the central hot water system. In the colder winter, the unit type may be appropriately increased so that it runs within a relatively high temperature in a day, Time to meet the needs of the system with heat. 3.2 Determination of solar collector area Solar-heat pump central hot water system, the solar collector area should be based on the hot water system design load or according to the actual situation to determine the solar heat as the basic basis and analysis of the project The unit area of ​​the solar collector on the average daily effective heat, so as to determine the solar collector installation area. In hot water projects, solar collectors are generally installed at a fixed angle. The effective heat gain per unit area varies with the seasons and changes in the daily solar radiation intensity are not a fixed value. The main factors affecting the installation of the collector angle, the system operating conditions, the location of meteorological parameters and solar radiation and so on. Different types of collectors have different heat collecting efficiencies and different effective heat quantities. Therefore, in practical applications, heat collecting efficiency and other data of collectors provided by collectors are generally analyzed and calculated. Take the annual average. 3.3 The form of solar collector system For the solar-heat pump central hot water system, the solar collector system not only serves as the main heat source for hot water heating but also as an auxiliary heat source for the heat pump unit and should be able to withstand lower ambient temperatures. Therefore, System, system working fluid using antifreeze solution. 4 Solar Energy - Practical Significance of Heat Pump Central Hot Water System 4.1 Operation Reliability Analysis Solar energy and air source heat pump are mature energy-saving and environment-friendly products as the main components of solar-heat pump central hot water system. Solar energy has been used for large-scale in domestic hot water system for more than 20 years. The large number of applications of air source heat pump has also been used for decades [10]. The solar water heater central hot water system organically combines solar energy with air source heat pump technology, Without affecting the original operating functions of the two under the conditions of its operational efficiency significantly improved to ensure stable and reliable operation of the system to save the conventional water heating system energy consumption. 4.2 Energy Efficiency Analysis According to solar radiation data in most parts of northern China, according to the average heat consumption of sanitary hot water system and solar collector daily average calorific value to determine the solar collector area of ​​solar water heating systems, solar - heat pump central hot water In the system, direct solar heating can meet the needs of 60-80% of the annual demand for hot water system, and the remaining 20-40% of the heat is supplied by the solar assisted air source heat pump unit. The average COP of the heat pump can reach 3.0, that is, More than 65% come from solar and air heat that can not be directly used by collectors. Throughout the operation of the system, the solar collector absorbs nearly 100% of the solar energy, the auxiliary heating consumes only 7-14% of the total energy consumption of the system, and at least 85% more energy than the conventional energy hot water system. Through the above analysis shows that the solar-heat pump central hot water system is a reliable, environmentally friendly energy-saving hot water system in the form of the system uses only a small amount of solar energy and electricity, the environment without any pollution. In the daytime minimum temperature of -15 ℃ above, the sun is well irradiated in most parts of China can promote the application. System and hot water supply, winter heating operation to save more than 60% of conventional energy, most of our winter cold and hot in summer, the system can also be combined with the building heating and air conditioning system, to maximize the energy saving effect.