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Abstract: This paper introduces the Beijing University to conduct deep geothermal heating demonstration project and cascade use of geothermal energy technology research projects in the pilot project of two comprehensive case. In this paper, for the school administered by the College Building in 2000 square meters of office area of geothermal heating (and cooling) in the pilot project system overview, use of deep geothermal energy when heat pump selection and the heat pump COP values, the system design considerations, dynamic experiments, geothermal use of open operating systems overall efficiency , geothermal utilization of the relationship between .
Key words deep geothermal gradient using water source heat pump heating buildings
An overview of Deep geothermal water in the world, widely used in a very long history. Western United States, deep geothermal areas, well depth of 300-400 meters, you can cut out the 80-90 in the geothermal water from underground environmental point of view, states have different policies, but the general does not advocate the use of open systems, if used, strict recharge the same layer. France's low-enthalpy heat can not warm aquifer water over 50 , well depth from several hundred meters to 1000-2000 meters range, and its application to achieve the cascade utilization, and strictly implement the "right well" system, that is, a production well , an injection well. Paris Basin, the groundwater level, 20 years, basically to maintain the water level did not fall, is a remarkable achievement. Poland holds aquifer thermal energy storage under the water temperature was between 30-130 , using a variety of use of technology. Hot water heating in China to have a long history of Tianjin and Tanggu area will be, but the higher water temperature in recent years, Tianjin, advanced technology, strict implementation "of the well" system, so that the groundwater level rose gradually.
Beijing is the world's few, there are deep geothermal water resources in the capitals. Over the past 30 years, a total of deep geothermal wells drilled about 200, more than 130 wells in normal use. Since most geothermal wells at temperatures between 40-60 , limited to the reasonable use of the spa villas. For a very few cases of direct geothermal heating. In 1999, in Beijing, discovered the depth of 3800 meters south of the city Department of 88 in the ground water. Since the bid to host the 2008 Olympic Games, Beijing authorities to conduct a comprehensive geophysical and found three large geothermal field, the water temperature up to 70-80 , well depth of 3,500 meters. Beijing's deep geothermal water level has fallen by 2 meters, from the perspective of sustainable development, to consider the use of deep ground water recharge technology and the importance of technology.
Second, pilot projects and the load characteristics of buildings
1. Building Features: Gailou to the original building. Office and laboratory section five-story building of 2,000 square meters, surrounded by two layers connected to a total of 10,000 square meters of classrooms. The middle of the glass dome 20 meters high in the hall, surrounded by eight outer door for evacuation use. As the "chimney effect", the cold winter outside the east gate through the normally open poured a lot of room, causing about 6 room temperature, around five-room into a cooling of the external walls. With the Office of the single large windows are cold penetration, but also limited to the construction of the economic situation, external wall insulation been simplified, resulting in room temperature around 13 in winter.
2. Load characteristics: the calculated design heating load in winter is about 120W/m2. As the office daily working time is 8:00-20:00. Evening and weekends or holidays, while keeping room temperature 10 . Smaller than the heating and cooling thermal loads.
Three pilot project system design considerations
1. Back to the recharge of irrigation water temperature and to consider: Our geothermal injection well well depth of 2,000 meters, 400 meters higher than the production well depth. Allowable amount for recharge, recharge temperature, the influence of heat storage, will take a long time to experiment identified. Therefore, on the one hand to make use of geothermal water to heat, to maintain a certain water temperature below 20 , such as peak load, you can try a short time to about 10 , long-term effects were observed. On the other hand, in non-peak load, but also reduce the amount of extracted ground water, do not make a lot of water recharge in the higher temperature, for example: try to avoid the water temperature above 25 recharge.
2. Utilization of the geothermal water considerations: recharge temperature directly affects the utilization of geothermal energy. Because geothermal energy is currently the hot water temperature down according to the average outdoor temperature throughout the year as a benchmark calculation. Not only out of deep geothermal water submersible pumps, energy consumption, hold the potential to be contaminated, but also the work of the unknown status of recharge wells.
3. On the direct use of geothermal water level to consider: Our total of two geothermal production wells, production wells are in the water temperature around 52 , the two wells is greater than or equal to the water Liangjun 70m3/hr. Geothermal water around 52 , after a plate heat exchanger, the circulating water up to 50 , is directly level with fan coil units, its power consumption, only circulating pump power.
4. On peak load consideration: Since the majority of Beijing's construction, heating and cooling load is greater than the load can be part of the heat pump and a heat flux. To provide boiler room area of the heat source, you can do with the peak heat.
5. Consider the use of heat pumps: Select import source side can tolerate water temperatures (ESWT) for the 30-35 geothermal heat pump, so that higher values of the heat cycle COP. In accordance with ARI-320 standard, water source heat pump heating conditions, the water side of the imported water temperature is 21 , in accordance with ARI-325 standard is 10 and 21 . Therefore, manufacturers generally do not provide ESWT can tolerate the heat pump to 30-35 . Select the United States ClimateMasterInc the GSW-120 type of water - water heat pump. Manufacturers recommend the use of ESWT does not exceed 35 . Then run the show good performance, curve provided by the study shown in Figure 1,2,3,4.
Figure 1 with water source heat pump COP side of the water temperature LSWT ( )
Figure 2 heat pump COP and the load side of the water temperature LSWT ( )
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