U-tube vacuum tube collectors, heat pipe vacuum tube collectors and DC vacuum tube collectors are all products developed on the basis of all-glass vacuum tube collectors, the three common characteristics of all have a high heat collection efficiency to Metal as a heat sink, can be pressure operation, but from the collector efficiency, leakproof, anti-scaling, durability, safety, reliability, installation and maintenance of a comprehensive evaluation of the difficulty, heat pipe vacuum tube collector is the most suitable The type of solar collector used in the central hot water supply system followed by the U-tube vacuum tube collector and the DC tube collector. Heat pipe vacuum tube heat pipe heat pipe, dry connection, the pipe does not go water, with a small heat capacity, heat transfer fast, freeze-resistant, heat shock, strong pressure, good insulation, no leakage, easy maintenance Advantages, U-tube vacuum tube collectors and DC collectors use vacuum tube concentric tube directly to the working fluid heating, in addition to a high temperature, high pressure resistance and thermal shock resistance and other characteristics, the set Thermal efficiency is higher than other types of collectors, and can be installed horizontally, simplifying the mounting bracket, reducing the installation site area, to avoid the collector affects the appearance of the building, in the solar energy and building a combination of strong adaptability, but the installation process than Heat pipe vacuum tube collector complex, more interfaces, there are leaks in operation, system maintenance costs are relatively high. 2 solar - heat pump central hot water system works solar and solar assisted heating air source heat pump as a central hot water system heat source, its purpose is to learn from each other, so that the two complement each other, each alternate, priority in the use of sunshine Solar heating hot water, the use of solar collectors produce low-temperature hot water as a solar assisted heating air source heat pump auxiliary heat source to improve the heat pump operating conditions and improve its heating performance. This combination of forms, both in relatively stable and efficient conditions to work under the system to ensure that the system 24/7 hot water supply. Air source heat pump heating process is essentially the solar energy contained in the air to enhance the use of heat pump according to the operating characteristics of the entire hot water system in the operation of the heat pump as an auxiliary heat source operation of the supply of heat, only one The small part comes from electric energy, so the solar-heat pump central hot water system greatly increases the utilization of solar energy and reduces the consumption of primary energy. Solar-Heat Pump The operation of the central hot water system mainly has the following four conditions: (1) solar heating domestic hot water In most sunny sunny days, the system according to this work conditions, the work of solar energy circulating pump by the system control According to the solar collector and hot water tank temperature control, an endless stream of heat collected by the collector through the intermediate heat exchanger to the hot water tank. (2) Solar assisted heat pump unit to heat domestic hot water When the cloudy or cloudy weather, when the solar collector temperature is lower than the hot water tank temperature is not enough to directly heat domestic hot water, the heat pump unit starts using the air as a heat source to heat the hot water tank Inside the hot water. In autumn and winter, when the ambient temperature is lower than the economic operating temperature of the heat pump, the heating efficiency of the heat pump unit drops down and the surface of the evaporator frosts. At this time, the heat pump assists the heating cycle to start, and the low-temperature solar hot water above the ambient temperature enters the heat pump unit Auxiliary heat exchanger, preheated air through the heat pump to improve efficiency, and cut have the role of preventing frost evaporator, you can save the heat pump unit power consumption. (3) Heating of domestic hot water at the same time by solar and heat pump units When the sunshine is good on a sunny day, if the heat consumption of the hot water system is greater than the effective heat supply of the solar heat collecting system or the number of solar collectors is small, the hot water system can not be satisfied Of the demand for heat, the solar and heat pump units work simultaneously to hot water heating system. (4) Heat pump unit directly heat domestic hot water In continuous rain and snow weather, the heat required by the hot water system is completely provided by the air source heat pump unit.