(Beijing Geothermal Research Institute)
This paper introduces the hot spring bathing provided by geothermal wells in Lvgang Jiayuan Community, Kim, Shunyi, Beijing, combined with water source heat pump heating and comprehensive utilization technology of geothermal resources. Combined with this project, the relationship between geothermal well water quantity, water temperature and heating area is given, which is of guiding significance to the early demonstration of geothermal heating project. In this paper, the operating cost of geothermal well combined with water source heat pump heating technology is analyzed in detail. The research shows that the operating cost of geothermal well combined with heat pump technology is 18 yuan /m2, which is lower than the heating charge standard of 24 yuan /m2. At the same time, the cost of hot spring bathing is much lower than that of hot tap water bathing.
1 preface
In the past, medium-low temperature geothermal resources, especially hot water with a temperature of about 50℃, were usually only used for hot spring bathing, planting and breeding, and rarely used for heating. This is mainly because the old radiator heating requires high water supply and return temperature, generally 95℃/70℃, and it is difficult for geothermal water at 50℃ to meet the room temperature requirements through radiator heating. At present, with the development of floor heating technology, fan coil technology and radiant ceiling technology, the temperature of heat source required for heating is greatly reduced, and generally 40 ~ 45℃ can meet the heating needs. Therefore, it provides a broad market space for geothermal direct heating and ground source heat pump technology heating.
Kim Green Harbor Home Community in Shunyi, Beijing is a comprehensive geothermal utilization project undertaken by our institute, which uses medium and low temperature geothermal resources for heating and providing hot spring bathing. The indoor terminal of the project adopts radiant floor heating and heat pump technology, which basically meets the heating and hot spring bathing needs of 230,000m2 residential quarters, and is equipped with three geothermal wells, so that low-temperature geothermal resources can be effectively utilized. Using clean geothermal energy for heating and soaking in hot springs has greatly improved the quality of houses, not only providing residents with a good living environment and air quality, but also bringing rich returns to developers.
2 Project overview
Kim Green Harbor Home is a large comprehensive residential community integrating residence, hotel, catering and entertainment. The total construction area is 630,000 square meters. The first-phase construction area is 230,000 square meters, and the public construction area is 30,000 square meters. The total heating load and cooling load of Kim Green Harbor Home are as follows: heating load: the thermal index per unit area in winter is 4 1W/m2, totaling 9430kW；; Public buildings: The unit refrigeration index in summer is 80W/m2, totaling 2400kW.
According to the above-mentioned cold and hot technical indicators and the geological conditions in this area, our hospital suggests that geothermal hot spring wells combined with water source heat pump technology should be used to provide heating and hot spring bathing in winter, and floor radiation heating should be used at the end of the heating room; In summer, water source heat pump units and cold water wells are used to provide refrigeration for public buildings, and fan coil units are used at the end. This project is a comprehensive utilization project of deep geothermal energy and shallow geothermal energy.
3 Determination of water required for heating and cooling
3. 1 Derivation of the relationship between cold and warm area and water quantity
According to the law of conservation of energy, the relationship between heating area and water demand of geothermal hot spring wells can be deduced, so the required groundwater quantity can be determined according to the heating area. Similarly, the area that can be heated can also be determined according to the water output and water temperature of geothermal wells.
A. Direct heating
Shallow geothermal energy: proceedings of the national on-site experience exchange meeting on geothermal (shallow geothermal energy) development and utilization
Where: s is the heating area, m2; Q is the heat load per unit area, w/m2; J is the mechanical equivalent of thermal coefficient, 4 187 joules/kcal; ρ is the density of water,1t/m3; C is the specific heat capacity of water, 1× 103 kcal/ton; Q is the water output of geothermal well, m3/h; T 1 is the outlet temperature of geothermal well,℃; T2 is the tail water temperature after heating,℃.
B, heating by combining heat pump technology
Shallow geothermal energy: proceedings of the national on-site experience exchange meeting on geothermal (shallow geothermal energy) development and utilization
Where: cop is the heating coefficient of the heat pump unit, which is generally 4; T3 is the tail water temperature after heat pump absorbs heat,℃.
From the relationship between (1) and (2), it can be seen that the heating area of geothermal well is directly proportional to the amount of geothermal water. In the case of a certain amount of water, it is directly proportional to the temperature difference used, that is, the greater the temperature difference used, the greater the heating area.
The combination of geothermal well and heat pump technology can increase the utilization temperature difference of geothermal water and correspondingly reduce the demand of geothermal water, thus achieving the purpose of intensive utilization of geothermal resources. For example, in the relationships (1) and (2), t2 is generally about 40℃, while t3 is about 10℃, so the temperature difference is increased by 30℃. For a geothermal well with a water outlet temperature of 70℃, 1 geothermal well can play the role of two geothermal wells through heat pump technology, which not only saves investment, but also saves valuable geothermal resources.
3.2 Determination of required geothermal well water quantity
It is understood that the total heating load of the community is 9430kW；; After the heat pump unit extracts heat, the tail water temperature can be reduced to 7℃; According to the analysis of reliable geological data, it is predicted that the geothermal well water volume is 55℃, the water temperature is 60m3/h, the well depth is 3000m, and the target layer of thermal storage is Wumishan Formation in Jixian system.
According to the above known data, it can be concluded that the required geothermal well volume is125m3/h.
3.3 Determination of required cold water well volume
Similarly, according to the law of conservation of energy, we can get the relationship between the water volume of public buildings and the cooling area:
Shallow geothermal energy: proceedings of the national on-site experience exchange meeting on geothermal (shallow geothermal energy) development and utilization
Among them, EER is the energy efficiency ratio of heat pump unit, and the ratio of obtained refrigeration capacity to input electric energy is generally 5; T 1 is the outlet temperature of cold water well,℃; T3 is the water temperature during recharging,℃.
It is known that the total cooling load is 2400kW；; Effluent temperature of cold water well 15℃, water quantity and well depth; The recharge temperature is 27℃. According to the above known data, the water demand of 30,000m2 public buildings can be obtained as 206m3/h by substituting into relation (3). ..
4 engineering technical scheme design
The heating temperature of this project is 55℃, and the geothermal water flow rate is125m3/h/h. According to the known hydrogeological data, two geothermal wells can meet the water demand. The geothermal well in this area is well reinjected, and 1 reinjected well can meet the needs. Therefore, three "geothermal well-heat pump units" (two pumps and one irrigation) are adopted in the heating project design, which can meet the heating requirements of the first-phase construction area of 230,000 m2 and the residents' hot spring bathing.
The quantity of cold water wells in public buildings is 206m3/h, while the depth of local wells is 100m, and the water quantity can reach 80m3/h, so three pumping wells can meet the demand. The recharge situation in this area is general, and the pumping-irrigation ratio is 1∶2. Therefore, the total number of cold water wells is 9. Using cold water well-heat pump unit to meet the cooling demand of public buildings in summer. Indoor floor heating technology is used, and fan coil units are used at the end of public buildings.
In order to meet the requirements of inlet and outlet water temperature of evaporator side of water source heat pump unit, and because geothermal well water can not directly enter the unit, geothermal well water is used to exchange heat through plate heat exchanger. Inlet water flow of plate heat exchanger 120 tons/hour, temperature 55℃, outlet water temperature 9℃, secondary water flow (water source heat pump unit side) about 750 tons/hour, inlet water temperature 7℃, outlet water temperature. When the unit is running at full load, the secondary water quantity can meet the requirements of total water quantity.
5 operating cost analysis
5. 1 main equipment and power distribution in the machine room (table 1)
Table 1 Main Equipment and Power Distribution in Computer Room
The total estimated value of other equipment is 150kW. The total power distribution is expected to be 2880.2kW, with the maximum power consumption of 2880.2kW in winter and 300kW in summer.
5.2 Cost analysis of operating expenses
The heating operation cost mainly includes the following contents: electricity consumption cost, personnel salary and welfare, equipment depreciation cost, annual maintenance cost and various taxes and fees.
Running six heat pump units can meet the maximum load, and the maximum heat provided by six units in winter is 9504kW. When the unit is fully loaded in winter, the total power consumption of the unit and its related auxiliary equipment is 2880.2kW.
According to the above power load (2880.2kW), the winter operation cost is calculated, and the daily average full-load operation time is 12 hours. The annual operating electricity fee for the equipment of water source heat pump central air conditioning cold and heat source scheme is 2,405,600 yuan (in winter).
As this project adopts automatic control technology, it needs 6 people to maintain (three shifts) during operation, and the salary is:
6 people × April×1600 yuan/(person-month) = 38,400 yuan.
The service life of all equipment is 15 years, and the service life of water wells is 15 years, so the annual depreciation expense is: equipment, 770,000 yuan/year; Well, 830 thousand yuan/year; A total of 6.5438+0.6 million yuan. The annual maintenance fee is 654.38 million yuan. The total amount is 4144,000 yuan. The annual operating cost per square meter is 18 yuan/square meter. At present, the central heating price in Beijing is 24 yuan/m2, and the natural gas heating price is 30 yuan/m2. Therefore, using geothermal well combined with water source heat pump technology for urban heating is not only technically feasible, but also has price advantage.
The geothermal well in the community not only serves as a heat source for heating, but also provides hot spring bathing in the community. Heating a ton of tap water with electric water heater requires 23 yuan, gas water heater needs 14 yuan, and domestic geothermal hot spring bath only needs to pay the mineral resource tax of 3.5 yuan per ton. In extremely cold weather, when there is a conflict between heating and bath water, you can start the cold water well for peak shaving.
6 conclusion and enlightenment
It is technically feasible to provide urban heating and hot spring bathing by using geothermal well combined with water source heat pump technology, and the operating cost is also better than gas. More importantly, geothermal resources are almost renewable clean energy, without any waste gas and waste, which is very conducive to improving the air quality of cities.
Compared with ordinary water source heat pump heating, geothermal well combined with heat pump technology has the following advantages:
(1) While heating, hot spring bathing can be provided;
(2) Due to the high water temperature, the demand for water is correspondingly reduced, thus reducing the number of wells and the occupied area;
(3) The depth of geothermal wells is generally about 3000m, and the hot water produced is generally bedrock fissure water, which has little effect on land subsidence; Generally, the cold water well is about 80m, mostly confined water in the Quaternary aquifer, which has a slightly greater relative impact.
The main disadvantages are high cost of geothermal well and high drilling risk.
Geothermal well combined with water source heat pump heating technology provides a new idea for low temperature geothermal heating. Most cities in China have such low-temperature geothermal resources. If it can be widely used, it will have a very positive significance for solving urban air pollution, saving energy and saving land.
refer to
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[3] Lu Yaoqing. Guide to HVAC design. Beijing: Building Industry Press, 1990.
[4] He Manchao et al. China Low Enthalpy Geothermal Engineering Technology. Beijing Science Press, 2004.
Zhu Jialing and others. Geothermal energy development and application technology. Beijing: Chemical Industry Press, 2006.