Abstract: In view of the current situation of energy utilization in our country and the demand of building green building, this paper introduces the advantages and disadvantages of soil source heat pump and its application scope. In view of the current situation and development background in Tianjin, The advantages and problems that should be noted. Keywords: Ground source heat pump Scope of application: Aiming at the actuality of energy using in our country and the request of green building, this paper introduce the advantage and disadvantage of Geothermal Heat Pump and its using areas. With the background of Tianjin area, we point out the advantages of Tianjin area in the development of Geothermal Heat Pump and some present issues Keywords: Geothermal Heat Pump using area Tianjin Introduction 1 In today's world, environmental pollution and the energy crisis have become the top priorities that threaten human survival. With the improvement of human living standards, central air conditioning energy consumption accounts for the proportion of the world's energy consumption continues to increase, and most of the central air conditioning energy consumption is consumed in the cold source. Therefore, the majority of professionals at home and abroad have been working hard to seek efficient and environmentally friendly air-conditioning cold and heat sources, building green buildings. For green building should be reflected in the following aspects [1]: 1, the symbiosis of architecture and nature: that is required to maintain the environment, the use of the environment, the defense of natural disasters. Protect the ecological system and reduce emissions of CO and other atmospheric pollutants, and maintain the balance of the ecological environment around the building; make full use of solar energy, geothermal energy for heating, heating, lighting and ventilation, give full consideration to green configuration, soften the artificial building environment; Consider the direction of the building and so on. 2, the application of building energy-saving technologies to reduce the environmental load: that is, to reduce energy consumption, extend the service life, the use of environmentally friendly materials, focus on energy reuse, the use of durable building materials and recyclable materials. 3, recycling-based construction career. Recycling runs through the entire building life. 4, to create a healthy and comfortable indoor environment. Including a healthy and lasting living environment, excellent air quality and so on. 5, so that the building into the history and culture of the human environment. Inherit and protect the landscape features of cities and regions, and maintain the permanent charm and vitality of the city. Ground-source heat pump system is a use of shallow underground heat resources (also known as geology, including groundwater, soil or surface water, etc.), by inputting a small amount of high energy (such as electricity) , In order to achieve energy-efficient green air-conditioning system that can both heat and cool. In building green buildings, ground-source heat pumps are a form of system that can be used in a wide range of applications. 2 advantages and disadvantages of ground-source heat pump and classification 2.1 The advantages of ground-source heat pump Soil-source heat pump using the characteristics of soil temperature stability throughout the year, the winter soil can be used as a heat pump heat source, that is, above ground temperature heat energy Removed for indoor heating, the summer soil can be used as a cold source of air conditioning, that is, the indoor heat removed to release the end of the ambient temperature in the soil [2]. Usually, the ground-source heat pump consumes 1 kilowatt (kW) of heat, and the user can get about 4 kilowatts of heat or cold so as to achieve the purpose of saving energy. In addition, no harmful substances are generated during the operation of the system, and the environmental protection effect is achieved. Ground source heat pump works as shown in Figure 1: Figure 1 ground source heat pump works A-underground circulation loop; B-heat pump work loop; C-indoor heat exchange loop The system has the following characteristics: [1] , Renewable resources, ground-source heat pump technology using the Earth's surface shallow geothermal resources (ground energy) as a heat source for energy conversion, while the shallow surface is a huge solar collector, collecting 47% of the solar energy, the equivalent In human use more than 500 times of energy each year, and not subject to geographical, resource constraints, the real amount is widespread, ubiquitous. This is an almost unlimited renewable energy stored in the shallow surface of the earth and a clean energy source. Compared with the ambient air on the ground, the soil temperature below 5m above the ground is basically stable throughout the year and slightly below the annual average temperature, which can provide relatively lower condensation temperature and higher evaporation temperature respectively in summer and winter. Therefore, thermodynamically speaking, soil is a hot and cold source of heat pump system better than ambient air. And ground source heat pump system will not heat, water vapor and bacteria in the atmosphere, in line with the current strategic requirements for sustainable development. Usually ground source heat pump consumes lKW of energy, users can get more than 4KW of heat or cold, the extra energy is the energy from the soil. In addition, the relatively constant temperature to the nature of the characteristics of the heat pump makes the operation more reliable and stable, but also to ensure system efficiency and economy. According to the EPA of the United States Environmental Protection Agency, the design and installation of a good ground source heat pump, on average, can save users 30% to 40% of the heating and cooling air conditioning operating costs. Efficient ground-source heat pump units, generating an average of 1 cold ton of cold only 0.88kW power consumption, the power consumption is only ordinary chillers plus boiler system 3O% ~ 60%; 2, less investment, low operating costs , Compared with the traditional air-conditioning system, the one-time investment can save 15% to 25%, annual operating costs can save about 40%. With the ground-source heat pump system, the ground-source heat pump can have higher efficiency and better reliability than the air-cooled heat pump because of the temperature of the soil. The temperature of the heat source is relatively stable throughout the year, generally at 10-25 ° C. And the ground source heat pump system can be used for heating, air conditioning, but also provide hot water, a system can replace the original boiler, air conditioning and refrigeration systems or systems, a multi-purpose machine; not only for hotels, shopping malls, office buildings, schools and other buildings , More suitable for heating and air conditioning in the villa house. In addition, the long life of the unit, are in 20 years or so; compact unit, saving space: low maintenance costs; a high degree of automation and control, unattended. The heat source in the ground source heat pump does not refer to the hot gas or hot (warm) water in the geothermal field, but refers to the normal ambient temperature soil. Therefore, there is no special requirement for underground heat sources and it can be applied in most areas of China. The COP value of the soil source heat pump system is generally about 3 to 6, which is about 40% higher than that of the conventional air source heat pump, and the operating cost thereof is 50% -60% of the normal central air space. 3, small footprint, room covers an area of ​​small, space-saving, can be located in the ground; 4, green, ground-source heat pump system using the earth's surface shallow geothermal resources, no burning, no smoke and waste, environmental plot , Without any pollution, the emission of pollutants from the ground-source heat pump is equivalent to a reduction of over 40% when compared with the air-source heat pump, which is equivalent to a reduction of over 70% as compared with that of the electric heating, and energy saving will be more obvious if combined with other energy-saving measures. Although the refrigerant is also used, it is 25% less than the conventional air conditioning unit. The ground source heat pump system is a self-contained system, which can be packaged and sealed well in the factory workshop. Therefore, the probability of refrigerant leakage is large To reduce. The unit is operated without any pollution and can be built in residential areas. It is installed in green spaces and parking lots. There is no combustion, no smoke emission and no waste. There is no need to store fuel waste and do not need to transport heat over long distances. Ground source heat pump system without cooling towers and other outdoor equipment, there is no central air-conditioning land area problems, saving space and land, generating extra profits for developers, resulting in additional economic benefits and improve the external image of the building; 5, High degree of automation, the unit and the unit and the system can be automated control, according to the outdoor temperature and indoor temperature control unit start and stop, to achieve the best energy-saving effect, while saving manpower and resources; 6, Any machine can be adjusted, investors can adjust the supply time and temperature as required, completely autonomy; 7, a multi-purpose machine, you can heating, but also cooling, heat generated in the cooling can also provide domestic production of hot water or heating for the swimming pool, Maximize the use of energy. 2.2 The disadvantage of ground-source heat pump 1, buried heat exchanger affected by the larger soil properties, soil thermal performance, energy balance, soil heat transfer and humidity have a greater impact on heat transfer [4]; 2, Condenser temperature and evaporating temperature of heat pump fluctuate due to the change of soil temperature during continuous operation; 3, the soil thermal conductivity is small, heat transfer is small. Experience has shown that its continuous heat absorption rate is generally 25W / m2, so when a certain amount of heat, heat exchanger coil covers an area larger, buried pipe laying either horizontal excavation arrangement or vertical drilling installation , Will increase the cost of civil engineering. 2.3 Classification of soil-source heat pump 2.3.1 According to the underground buried pipe system classification Underground buried pipe heat pump system according to the form of buried pipe can be divided into horizontal buried heat pump and vertical buried heat pump. Horizontal pipe is often used in engineering examples, and more for heating. The vertical buried pipe generally considered its performance better than the horizontal buried pipe system, but the construction of a relatively high degree of difficulty. 1, horizontal buried heat pump system About horizontal buried heat pump research began in 1930 to 1940. Such systems, commonly used in Europe today, are mostly used for heating purposes only. Horizontal coil system has a single layer and double the two forms, can be U-shaped, snake-shaped, single-slot single-slot single tube and other forms. Monolayer is the earliest and most commonly used form, the general design depth of buried pipe between 0.5m to 2.5m. Due to different soil saturation, the depth of the trenches is also different. If the entire winter soil are in saturation, the depth of the trench must be greater than l.5m at the same time for heating. Tube burial depth of more than 1.5m heat storage slow, and less than 0.8m, the coil will be affected by ground cooling and freezing, the other tube spacing of less than 1.5m, coil may produce solid ice crystals and reduce the heat storage in the spring . The double-layer coil system is about 1.2m deep in one layer and about 1.9m deep in the other layer, that is, laying a layer of pipe at a height of 1.9m and then backfilling to a depth of 1.2m to lay another layer of double-layer laying drastically reduced Excavation depth and fill the amount of sand required. 2, vertical buried hot spring system Vertical buried hot spring system has two kinds of shallow buried and buried. Shallow depth of 8m to