Abstract: This paper first introduces the concept and working principle of water source heat pump technology, compares it with that of boiler and air source heat pump, and draws a conclusion that water source heat pump technology is a technology that makes use of renewable energy. Subsequently, the characteristics of water source heat pump are described in detail and the basic situation of application of ground source at home and abroad and the prospect of development and application of water source heat pump in China are introduced. Finally, the technical characteristics of Tsinghua Tongfang water source heat pump and the popularization and application of water source heat pump in China Some of the problems. First, the concept of water source heat pump technology and working principle Water source heat pump technology is the use of shallow surface water sources such as groundwater, rivers and lakes in the absorption of solar and geothermal energy and low temperature heat energy resources and the use of heat pump principle, through a small amount of high Power input, low heat transfer to a high heat transfer of a technology. Shallow water on the surface of the Earth, such as groundwater, surface rivers and lakes and seas at depths of up to 1,000 meters, absorbs considerable solar radiation into the Earth and the temperature of the water source is generally stable. The principle of water source heat pump unit is to transfer the heat in the building to the water source in the summer. Because of the low temperature of the water source, the heat can be efficiently taken away, and in winter, the energy is extracted from the water source by the heat pump principle by air or water Refrigerant to the building after raising the temperature. Usually water source heat pump consumes 1kW of energy, users can get more than 4kW of heat or cold. Water source heat pump according to the different ways of using water can be divided into two kinds of closed system and open system. Closed system refers to the water side of a group of closed loop heat transfer casing, the casing is generally buried horizontally or vertically in the sea water or seawater, through the heat transfer with the soil or seawater to achieve energy transfer. (Which buried in the soil system, also known as ground-source heat pump, buried in the sea water system, also known as seawater source heat pump). Open system refers to the system that discharges directly from the underground pumping water or surface water through the heat exchanger. Water-source heat pumps have significant advantages over heating systems for boilers (electricity, fuel) and air-source heat pumps. Boiler heating can only 90% ~ 98% of the electric energy or 70 ~ 90% of the fuel can be converted into heat for the user, so ground-source heat pump to save electricity more than two-thirds of electric boiler heating, fuel The boiler saves more than one-half of the energy. Since the heat source temperature of the water source heat pump is relatively stable throughout the year, the temperature of the heat source of the water source heat pump is generally 10-25 ° C, and the cooling and heating coefficient can reach 3.5-4.4. Compared with the conventional air source heat pump Higher than about 40%, its operating costs for the ordinary central air-conditioning 50 to 60%. Therefore, over the past decade or so, especially in the past five years, water source heat pump air conditioning systems have achieved rapid development in North America such as the United States, Canada, Central and Northern Europe such as Switzerland and Sweden, and the water source heat pump market in China has also become increasingly active. The technology is expected to be the most effective heating and cooling air-conditioning technology in the 21st century. In China's traditional concept of air-conditioning systems, due to the country's economic development and policies, the north generally solves winter heating problems with coal-fired boilers for a long period of time and water cooling units in the south address summer cooling issues. After 1980s, the way of refrigeration units began to diversify. At this moment, lithium bromide units and air-cooled units appeared. The capacities of units also changed from large and medium-sized units to large, medium and large units, Since the 1990s, new attempts and discussions have been made on heating methods. In particular, with the promotion of sustainable development and public awareness of environmental protection, the structure of energy use in both the world and China is changing. From the existing coal and oil Heating transition to natural gas and electricity and other clean energy. As one of the cities with the most air pollution in Beijing, its policy on the control of air pollution includes the adjustment of energy structure from coal to natural gas and electricity to alternative energy sources. However, although alternative energy sources can partially solve the problem of air pollution, natural gas and petroleum are non-renewable energy sources. From a sustainable development point of view, it is necessary to improve energy efficiency or find renewable energy sources. However, water-source heat pump units are An ideal device. Second, the characteristics of water source heat pump Water source heat pump technology uses surface water as the air conditioning unit of the heating and cooling source, so it has the following advantages: 1, is a renewable energy technology Water heat pump is the use of the Earth's water storage of solar energy resources as a Cold and heat source, energy conversion heating and air conditioning system. Among the available water bodies are groundwater or rivers, rivers and lakes that are part of the surface, and oceans. Surface soil and water bodies are not only huge solar collectors that collect 47% of the solar radiation energy, more than 500 times the amount of energy used annually by human beings (underground water bodies receive indirect solar radiation energy through the soil) and are A huge dynamic energy balance system, the soil and water on the surface naturally maintain the relative balance of energy acceptance and divergence. This makes it possible to utilize almost infinite solar energy or earth stored therein. So, a water source heat pump uses a technology that is clean and renewable. 2, water-efficient heat pump units available water temperature in winter is 12 ~ 22 ℃, the water temperature is higher than the ambient air temperature, so the heat pump cycle evaporation temperature increases, the energy efficiency ratio also increased. The summer water body is 18-35 ° C, and the temperature of the water body is lower than the ambient air temperature. Therefore, the condensation temperature of the cooling decreases, making the cooling effect better than that of the air-cooling and cooling towers, and the unit efficiency is improved. According to the EPA of the United States Environmental Protection Agency, the design and installation of a good water source heat pump can save 30-40% of the heating and cooling air-conditioners on average. 3, stable and reliable operation The water temperature is relatively stable throughout the year, the scope of its fluctuations is much smaller than the air changes. Is a very good heat pump heat source and air conditioning cold source, water temperature is more constant characteristics, making the heat pump operation more reliable and stable, but also to ensure the system's efficiency and economy. There is no air source heat pump in winter defrost and other difficult issues. 4. Significant Environmental Benefits Electric water heaters use electric energy, which itself is a clean energy source, but consumes primary energy and causes emissions of greenhouse gases such as pollutants and carbon dioxide when generating electricity. Therefore, the pollution of energy-saving equipment itself is small. The power consumption of well-designed water-source heat pump units is equivalent to a reduction of more than 30% compared to air-source heat pumps, which is equivalent to a reduction of more than 70% when compared to electric heating. The refrigerant used in water source heat pump technology can be replaced by R22 or R134A, R407C and R410A. The water source heat pump unit runs without any pollution and can be built in residential areas without burning, without smoke and without waste, There is no need to store fuel waste on the site, and no long-distance heat transfer. 5, a multi-purpose machine, wide range of applications Water source heat pump system can be heating, air conditioning, but also for domestic hot water, a multi-purpose machine, a system that can replace the original boiler plus air conditioning two sets of devices or systems. Especially for buildings with both heating and cooling requirements, water-source heat pumps have obvious advantages. Not only saves a lot of energy, but also with a set of equipment to meet both heating and cooling requirements, reducing the initial investment of equipment. Water source heat pump can be applied to hotels, shopping malls, office buildings, schools and other buildings, small water source heat pump is more suitable for residential heating, air conditioning. 6, automatic operation of water source heat pump unit due to stable conditions, so you can design a simple system, fewer components, simple and reliable unit operation, low maintenance costs; a high degree of automatic control, the service life of up to 15 years. Of course, like any thing, water source heat pump is not perfect, its application will be constrained. ⑴ available water source constraints Water source heat pump can theoretically use all the water resources, in fact, the actual project, the cost difference between different water use is considerable. So in different regions whether there is a suitable water source heat pump applications become a key. The current water source heat pump use, the closed system is generally higher cost. The open system, can find the right water to become a source of heat pump restrictions. On the open system, water requirements must meet a certain temperature, water and cleanliness. (2) Restrictions on the Geographical Structure of the Aquifer For the use of underground pumping and recharge, the geologic structure of the place of use must be taken into account to ensure that wells can be found under economic conditions to find a proper source of water, taking into account local geology and soil The conditions to ensure that after the tail water can be achieved. (3) The economic efficiency of investment Due to the different basic conditions of water resources affected by different regions, different users and national energy policies and fuel prices, the one-time investment and operating costs will vary from user to user. Although, on the whole, water-source heat pumps operate at a higher cost and with lower costs, However, compared with the traditional air-conditioning and cooling heating methods, the water-source heat pump investment economy will be different under different requirements of different regions. Third, the development and characteristics of water source heat pumps at home and abroad abroad, the research on water source heat pump belong to two types of heat pump system: one for the ground source heat pump, a seawater heat pump. One of the real significance of commercial applications of ground source heat pump only a few years history, but the development is quite rapid. For example, in the United States, there were 14,000 ground-source heat pumps in the country as of 1985, up from 45,000 in 1997 and 400,000 already so far, with steady growth of 10% annually. Ground-source heat pump systems in commercial buildings in the United States accounted for 19% of total air-conditioning capacity in 1998, of which 30% were new construction. The ground-source heat pump industry in the United States has been established by the Energy & Environmental Research Center, the National Groundwater Resources Association, the Edison Elect