Abstract: The heat pump technology in building heating and air conditioning can effectively improve the primary energy utilization rate, reduce the emissions of greenhouse gas CO2 and other atmospheric pollutants, minimize the impact of air-conditioning equipment on the appearance of the building. This paper expounds the principle of using heat pump to heat energy than the direct combustion of boiler, and gives a detailed introduction of the main heat pump heating modes, especially the technical features, applicable scope and economy of ground source heat pump. Keywords: heat pump building environment energy saving 1, heat pump and building heating and air conditioning With economic development and improvement of people's living standards, heating and air conditioning in public buildings and houses have become common needs. In developed countries, heating and air conditioning energy consumption can account for 25-30% of the total social energy consumption. The energy mix in our country depends mainly on fossil fuels, especially coal. A large number of pollutants generated by the combustion of fossil fuels, including a large number of harmful gases such as SO 2 , NOX and greenhouse gases such as CO 2 . The environmental problems caused by burning large quantities of fossil fuels have increasingly become the focus of attention of all governments and the public. China's heating has experienced a change from a small coal-fired boiler to a coal-fired boiler. Now further prohibit the construction of small and medium-sized coal-fired boiler rooms in urban areas, reflecting the government attaches great importance to the protection of the atmospheric environment. Therefore, in addition to the type of district heating, there is an urgent need to develop alternative alternative heating methods. Heat pumps are new technologies for heating and air conditioning that save energy and reduce air pollution and CO 2 emissions. 1.1 Heat Pump Principle and Composition Heat pump (refrigerator) is through the work of the heat from the low temperature medium to high temperature medium flow device. Building air-conditioning system should generally meet the winter heating and summer cooling two opposite requirements. Traditional air-conditioning systems usually require separate sets of cold sources (chillers) and heat sources (boilers). Because of the need to have a cold source (chiller) in a building air conditioning system, boiler and boiler rooms can be eliminated if it is run in heat pump mode in winter, saving not only initial investment, but also the use of clean energy such as electricity throughout the year, Greatly reduce the air pollution caused by heating problems. Heat pump air conditioning system usually consists of a refrigerant loop, indoor loop and low temperature heat exchanger loop loop. Some also have a loop of hot water heating. Different types of heat pump, the refrigerant loop and the indoor loop is basically the same, but the low temperature heat source heat transfer loop are different. Such as split air conditioners outdoor unit is the air source heat pump low temperature heat source heat exchange loop, and the geothermal heat exchanger is the ground source heat pump low temperature heat source heat exchange loop. A closed pressurized loop that circulates water from the domestic hot water tank to the condenser is a loop through which domestic hot water can be selectively heated. For summer conditions, this cycle takes full advantage of the heat released by the condenser and does not consume additional energy to get hot water; in winter it also consumes significantly less energy than the electric water heater (see Figure 1). ? Figure 1 ground source heat pump flow diagram 1.2 heat pump features Heat pump for building heating can greatly reduce the consumption of primary energy. Normally we generate heat by burning direct fossil fuels (coal, oil, natural gas) and eventually heat the building through several heat transfer links. In the ideal case where there is no heat loss from the boiler and heating pipelines, primary energy utilization (ie, the ratio of the heat of the building heating to the heating of the fuel) can be up to 100%. If the first use of high-temperature thermal energy combustion power generation, and then use the electric energy-driven heat pump to absorb low-grade thermal energy from the surrounding environment, the appropriate increase in temperature and heating the building, you can take full advantage of high-grade fuel energy, greatly reducing the Primary energy consumption for heating. The coefficient of performance of the heat pump with heat, that is, the ratio of the amount of heat supplied and the amount of energy consumed, can now reach 3 to 4. The resistivity heating device to convert electrical energy into thermal performance coefficient of 1. Heat pumps are the most cost-effective technology to reduce CO 2 emissions. There are now about 130 million heat pumps in operation around the world, with a total heat output of 4.7 × 10 9 GJ per year and a reduction of about 130 million tons of CO 2 emissions each year. With the further improvement of heat pump technology and the further improvement of power generation efficiency, it is possible to reduce the global CO 2 emissions by 16% with heat pump technology. Therefore, it is one of the key technologies for building energy efficiency and reducing CO 2 emissions. In addition to reducing the consumption of fossil fuels outside, since the concentration in large power stations burning fossil fuel power boiler facilitate use of advanced technology to remove or reduce the combustion product dust, SO 2 and NOx and other air pollutants, the use of electric heating and heat dispersion Housing heating can also greatly reduce the air pollution caused by coal combustion. Heat pumps, which take full advantage of renewable energy, are a sustainable technology. Heat pumps use low-temperature heat sources are usually the environment (air, surface water and earth) or a variety of waste heat. The heat absorbed by these heat sources by the heat pump is a renewable energy source. Such as ground source heat pump in the heat of the earth after the heat of the building heating, while reducing the temperature of the earth, that is, the storage of cold for summer use; summer heat transfer to the building through the heat pump to the earth , Cooling the building while storing the heat in the ground for winter use. This land played the role of accumulator to further improve the energy efficiency of the air-conditioning system throughout the year. As mentioned above, geothermal heat pumps use geothermal heat exchangers as a low-temperature heat source loop, eliminating the need for cooling towers and outdoor heat exchangers; replacing chillers with chillers (heat pumps). Therefore, for architects, there is another important advantage of GSHH air-conditioning system, which is to remove the boiler room and cooling tower required by traditional air-conditioning system. The need for and restrictions on building space at these facilities often become a problem for architects. The ground source heat pump air conditioning system does not have outdoor facilities, no effect on the appearance of the building. Therefore, this technology is especially suitable for landscape architecture, ancient buildings and air-conditioning projects that make it difficult to set up cooling towers. This technology helps to protect the façade and the surrounding environment of these buildings from being damaged and solves the problem of having no place for a cooling tower or a boiler room. For example, in the landmark area of ​​Wenzhou Century Plaza, air-conditioning system uses a ground source heat pump as a source of cold and heat, mainly due to landscape considerations. 2, air-conditioning heat pump classification and technical analysis There are many types of heat pump systems for the purpose of air-conditioning in buildings (including heating and cooling), such as heat-recovery type heat pumps that utilize the heat (cooling capacity) of the building ventilation system and water that is used in different sections of the interior of a large building Central heat pump system. This article focuses on the use of the surrounding environment as a hot and cold air conditioning heat pump system. By their nature, foreign literature usually divides them into two categories: air source heat pump (ASHP) and ground source heat pump (GSHP). Ground-source heat pumps can be further divided into surface-water heat pumps (SWHPs), groundwater heat pumps (GWHPs) and ground-coupled heat pumps (GCHPs). Our country on the heat pump system terminology has not yet formed a normative usage. For example, commercial names for "ground temperature air conditioning" are used for groundwater heat pump systems; underground heat pumps are referred to in some literature as "ground source heat pumps," or directly as "ground source heat pumps." 2.1 air source heat pump air source heat pump to outdoor air as a heat source. Under the condition of heating, the outdoor air is taken as a low-temperature heat source to absorb the heat from the outdoor air, and the heat pump is used to raise the temperature and send it into the room for heating. The coefficient of performance (COP) is generally 2 to 3. Air source heat pump system is simple, the initial investment is low. Air source (air-cooled) heat pump current products are mainly household heat pump air conditioners, commercial unit heat pump air-conditioning units and air-cooled heat pump hot and cold water units. The main disadvantage of air-source heat pumps is that the efficiency of the heat pump is greatly reduced during high temperatures in summer and cold weather in winter. In addition, the necessary outdoor unit or cooling tower on the building have a certain impact or damage. Air-source heat pump heating with the outdoor air temperature decreases and reduce, which is the opposite of the building thermal load demand. Therefore, when outdoor air temperature is lower than the balance of the heat pump temperature, you need to use electricity or other auxiliary heat source to heat the air. Moreover, air-source heat pump evaporators frost on heating conditions and require regular defrosting, which also consumes a lot of energy. Frosting of heat pump evaporators in cold and high humidity areas can be a major technical obstacle. In summer hot weather, as its cooling capacity decreases with outdoor air temperature, the same may cause the system can not work properly. Air source heat pump is not suitable for cold areas, in the more temperate winter climate regions, such as China's midstream and downstream areas of the Yangtze River, has been widely used. 2.2 Ground Source Heat Pump Another type of heat pump using the earth (soil, groundwater, groundwater) as a heat source, can be called "ground source heat pump." Ground-source heat pumps overcome the technical barriers to air-source heat pumps because they remain constant throughout the year in undisturbed conditions, well above the outdoor temperature in winter and outside the summer, and the efficiency Greatly improve. In addition, in winter, the heat in the ground is raised by the heat pump to heat the building and the temperature in the ground is reduced, that is, the cold energy is stored for use in summer. In summer, the heat in the building is transmitted to The earth, cooling the building, while storing heat in the earth for winter use. This ground source heat pump system in the earth played the role of accumulator to further improve the air conditioning system annual energy efficiency. 2.2.1 Groundwater heat pumps Groundwater sources Heat pumps are the source of groundwater drawn from wells or abandoned mines. The heat-exchanged groundwater can be discharged into the surface water system, but for larger applications it is often required to recharge the groundwater to the groundwater level through the recharge well. Groundwater with good water quality can directly enter the heat pump for heat exchange. Such a system is called open loop. In practice, more closed loop heat pump circulating water system is adopted, that is, the plate heat exchanger is used to separate the groundwater from the circulating water through the heat pump to prevent the influence of the sediment and corrosive impurities in the groundwater on the heat pump. The groundwater heat pump system is more efficient than the air source heat pump because the groundwater temperature is basically constant over the years, the temperature in summer is lower than that in outdoor air, the temperature in winter is higher than that in outdoor air, and the heat capacity is larger. The COP value is usually 3 to 4.5, There are frosting and other issues. Groundwater source heat pump system has been rapidly developed in our country in recent years. The use of groundwater heat pump systems is also limited by many conditions. First of all, such systems require a rich and stable groundwater resource as a prerequisite. As a general rule, the air conditioning area of ​​10,000 m 2 requires about 120 m 3 / hr of groundwater. The economics of groundwater heat pump systems also have a large relationship to the depth of the groundwater layer. If the groundwater level is low, not only the cost of going to a well increases, but also the power consumption of the pump in operation will greatly reduce the efficiency of the system. In addition, although theoretically extracted groundwater will be recharged into the groundwater layer, at present, groundwater recharge technology in China is not yet mature and the rate of recharge under many geological conditions is much lower than that of pumping water. The water extracted from underground passes After the heater is difficult to be fully recharged into the aquifer, causing the loss of groundwater resources. Furthermore, how to ensure that the groundwater layer is free from pollution can be a thorny issue even if all the extracted groundwater can be recharged. 2.2.2 Surface water heat pumps One source of heat for surface water heat pump systems is surface water in ponds, lakes or streams. The use of these natural waters as low-temperature heat sources in heat pumps near large rivers, lakes and seas, etc., is a type of air conditioning heat pump to be considered. Heat pump and surface water heat exchanger can be used open loop or closed loop in the form. Open cycle is the use of water pump pumping surface water in the heat exchanger and heat pump circulating fluid heat before discharge into the water. The disadvantage is poor water quality in the heat exchanger produce dirt, affecting heat transfer, and even affect the normal operation of the system. More commonly used surface water heat pump system uses closed-loop, that is, multiple sets of plastic pipe sinking into the water, heat pump circulating fluid through the coil and the water heat exchanger, to avoid dirt and corrosion caused by poor water quality problems. Of course, this surface water heat pump system is also subject to natural conditions. In addition, as the surface water temperature is greatly affected by the climate, similar to the air source heat pump, the heat pump heat quantity is smaller when the ambient temperature is lower, and the heat pump performance coefficient is also reduced. Certain surface water body can bear the heat load and its area, depth and temperature and other factors, need to be calculated according to the specific circumstances. The heat exchanger on the impact of water on the ecological environment sometimes need to be considered in advance. Deep water lakes in the summer will produce temperature stratification, the bottom of the lake to maintain a lower temperature; winter lake ice will limit the temperature drop. 2.2.3 underground coupled heat pump underground heat pump system is the use of underground geothermal heat in the closed-loop ground source heat pump system. Often referred to as "closed-circuit ground source heat pump" to distinguish it from groundwater heat pump systems or directly as "ground source heat pumps." It is through the circulation of liquid (water or water as the main component of the antifreeze) in the closed underground pipe flow, the system and the ground to achieve heat transfer. The underground coupling heat pump system is structurally characterized by a geothermal heat exchanger (or ground heat exchanger) consisting of buried underground pipes. Geothermal heat exchangers are mainly installed in the form of horizontal buried pipe and vertical buried pipe two. Horizontal pipe buried in the form of open 1 to 2 meters deep trench, buried in each groove 2, 4 or 6 plastic pipe. The vertical buried pipe is to drill a hole with a diameter of 0.1-0.15 m in the ground and set up one (two) or two (four) U-pipes in the borehole and filled with filling material. Drilling depth is usually 40 ~ 200 m. The available surface area on site is a decisive factor in the choice of the form of the geothermal heat exchanger. Vertical buried geothermal heat exchanger can save a lot of land area than the horizontal buried pipe, so it is more suitable for China's less people and more national conditions. The total length of the buried pipe required for the geothermal heat exchanger needs to be calculated in detail according to the form of the buried pipe, the thermal properties of the underground rock, the underground temperature and the cooling load. The main cost of setting geothermal heat exchangers is the cost of drilling. Therefore, the correct design of geothermal heat exchanger tube length is very important to ensure system performance and economy. Due to many influencing factors and complex mathematical models, some geothermal heat exchanger design and calculation software have been developed both at home and abroad, which can avoid the mistakes made by blind estimation. The thermophysical properties of the underground rock have a great influence on the heat transfer capability. It is suggested that the physical properties of the underground rock should be determined by field measurement. In recent years, our researchers and engineers have made unremitting efforts in the design theory of geothermal heat exchangers based on the assimilation of foreign advanced technologies. Shandong Institute of Building Engineering has built a closed-circuit ground source heat pump demonstration project in 2001 Put into practical use, has accumulated valuable experience in popularizing and applying this new technology in our country. 3, ground source heat pump air conditioning system economic analysis Ground source heat pump system can be achieved on the building heating and cooling, but also for domestic hot water, a multi-purpose machine. A system can replace the original boiler plus cooler two sets of devices or systems. Compact system, eliminating the boiler room and cooling tower, saving construction space, but also conducive to the appearance of the building. As mentioned above, another notable feature of GSHP systems is that it greatly increases primary energy utilization and therefore has the advantage of being energy efficient. Ground source heat pump than the traditional air conditioning system operating efficiency of about 40-60% higher. In addition, the relatively constant temperature of the ground source makes the operation of the heat pump unit more reliable and stable. The maintenance cost of the entire system is also greatly reduced compared with the boiler-refrigerator system, which ensures the high efficiency and economy of the system. The obstacles that have hindered the application of underground coupled heat pump systems in our country are mainly high initial investment in buried underground pipes and lack of understanding of this technology by the government, architects and the general public. The economics of GSHP air conditioning systems depend on many factors. Different regions, different geological conditions, different energy structures and prices will have a direct impact on their economy. According to foreign experience, due to the low operating cost of ground-source heat pump, the initial investment increased can be recovered within 3 to 7 years. The average cost of ground-source heat pump system during the whole service cycle will be lower than that of the traditional air-conditioning system. Here according to the situation in Shandong Province and the current price system for ground source heat pump air conditioning and traditional air-conditioning initial investment and operating costs for a comparison. Table 1 ground source heat pump air conditioning and conventional air conditioning investment and operating costs of the initial comparison Hot and cold source approach And serial number project 1 2 3 4 Ground source heat pump Chiller and Gas boiler supporting Chiller and City heating network package Direct-fired lithium bromide Hot and cold water units Hot and cold water unit (yuan / kW cold) 600 ~ 800 560 ~ 700 560 ~ 700 950 ~ 1300 Gas boiler (yuan / kW heat) 400 ~ 520 Heating network (Yuan / m 2 heating area) 100 Cooling tower (yuan / kW cold) no 40 ~ 60 Underground drilling and buried pipe (yuan / kW) 800 ~ 1400 no Room pump, piping, control and so on Basically the same (20 to 40 yuan / m 2 ) Building air conditioning terminal Basically the same (100 ~ 160 yuan / m 2 ) Estimated initial investment (cold index 100W / m 2 ) Initial investment (Yuan / m 2 air-conditioned area) 340 280 330 280 Operating costs comparison (thermal index 100W / m 2 ) season summer winter summer winter summer winter Winter, summer two seasons Energy form Electricity Electricity natural gas Electricity Heating network natural gas Light diesel oil unit kW.h kW.h m 3 kW.h m 2. Season m 3 Rise Price (yuan) 0.5 0.5 2.0 0.5 19.5 2.0 3.0 Calorific value 1000W 1000W 35600kW 1000W 35600kW 43000kW effectiveness 4.8 3.5 3.8 0.88 3.8 0.88 0.85 Fuel consumption / m 2 .h 0.021 0.029 0.0263 0.0115 0.0263 0.0115 0.01 / m 2. Season 13.23 28.02 16.57 11.27 16.57 18.52 16.1 Fuel costs (dollars / m 2. Season) 6.6 14 8.29 22.54 8.29 19.5 37.04 48.3 Room operating costs (yuan / m 2. Season) 4.5 yuan / m 2. Two seasons Cooling tower operating costs no 2 yuan / m 2 quarter Total annual running costs (yuan / m 2) 25.1 37.33 34.29 43.54 54.8 Cost ratio 1 1.49 1.37 1.73 2.18 Note: The days in winter and summer are respectively 140 days and 90 days, running 10 hours a day, and the running load factor is 0.7. Engine room operating costs and cooling tower operating costs are operating costs of water pumps and other electrical equipment, the table is the estimated value. 4 Conclusion In building heating and air conditioning using heat pump technology can effectively improve the primary energy efficiency and reduce emissions of greenhouse gases CO 2 and other pollutants generated by combustion is a sustainable development of new building energy-saving technologies. Among the main heat pump systems discussed in this paper, the air-source heat pump has the lowest initial investment, but its efficiency is low and its application conditions are limited. It will still be used more often in some areas with mild winter temperatures. Groundwater heat pump and surface water heat pump system is subject to water resources conditions, the scope of application is limited. Ground source heat pump (underground heat pump system) a wide range of applications, low operating costs, energy saving and environmental benefits significantly. Ground-source heat pump has been widely used in many countries in North America and Europe and is a mature technology. However, our country has just started the application of ground-source heat pump. The promotion of ground source heat pump technology requires government policy guidance, training of design and construction personnel, equipment and materials needed, and public awareness of ground source heat pump technology. The main constraints in the application of heat pump technology in heating and air conditioning used to be the lack of electricity supply and the low level of people's consumption. The market demand for heat pump air-conditioning systems has not yet been established. With the economic development and improvement of people's living standards in our country since the reform and opening up, the above two constraints have ceased to exist. Air conditioning and heat supply have become the needs of ordinary people and have gradually expanded to the rural and southern areas with good market prospects. Through the joint efforts of government departments, research institutions and engineering and technical personnel, learn from the successful experience of other countries, China's application of ground source heat pump will be faster to promote and develop. Hot and cold source approach And serial number project 1 2 3 4 Ground source heat pump Chiller and Gas boiler supporting Chiller and City heating network package Direct-fired lithium bromide Hot and cold water units Hot and cold water unit (yuan / kW cold) 600 ~ 800 560 ~ 700 560 ~ 700 950 ~ 1300 Gas boiler (yuan / kW heat) 400 ~ 520 Heating network (Yuan / m 2 heating area) 100 Cooling tower (yuan / kW cold) no 40 ~ 60 Underground drilling and buried pipe (yuan / kW) 800 ~ 1400 no Room pump, piping, control and so on Basically the same (20 to 40 yuan / m 2 ) Building air conditioning terminal Basically the same (100 ~ 160 yuan / m 2 ) Estimated initial investment (cold index 100W / m 2 ) Initial investment (Yuan / m 2 air-conditioned area) 340 280 330 280 Operating costs comparison (thermal index 100W / m 2 ) season summer winter summer winter summer winter Winter, summer two seasons Energy form Electricity Electricity natural gas Electricity Heating network natural gas Light diesel oil unit kW.h kW.h m 3 kW.h m 2. Season m 3 Rise Price (yuan) 0.5 0.5 2.0 0.5 19.5 2.0 3.0 Calorific value 1000W 1000W 35600kW 1000W 35600kW 43000kW effectiveness 4.8 3.5 3.8 0.88 3.8 0.88 0.85 Fuel consumption / m 2 .h 0.021 0.029 0.0263 0.0115 0.0263 0.0115 0.01 / m 2. Season 13.23 28.02 16.57 11.27 16.57 18.52 16.1 Fuel costs (dollars / m 2. Season) 6.6 14 8.29 22.54 8.29 19.5 37.04 48.3 Room operating costs (yuan / m 2. Season) 4.5 yuan / m 2. Two seasons Cooling tower operating costs no 2 yuan / m 2 quarter Total annual running costs (yuan / m 2) 25.1 37.33 34.29 43.54 54.8 Cost ratio 1 1.49 1.37 1.73 2.18