Zhao Jiankang, Zhang Yong, Zou Dengliang, Huang Changjun, He Yuncheng, Yang Junwei, Shi Hanjing, Li Weifang
(Beijing Geothermal Research Institute)
Abstract: The article describes the comprehensive utilization of geothermal resources in Beijing Shunyi Jinhan Lugang Homeland Community by combining the geothermal wells with the water-source heat pumps for heating as well as the comprehensive utilization of geothermal resources for providing hot springs for bathing. Combined with this project, the author gives the relationship equation between the water volume and temperature of geothermal wells and the heating area, which is of guiding significance for the preliminary demonstration of geothermal heating projects. This paper focuses on the operating cost of geothermal well combined with water source heat pump heating technology is analyzed in detail. The study shows that the operating cost of heating with geothermal well combined with heat pump technology is 18 yuan/m2, which is lower than the heating charge of 24 yuan/m2 for centralized heating in Beijing, and at the same time, the hot spring bathing is much lower than the cost of heating tap water for bathing.
1 Preface
In the past, for the low and medium temperature geothermal resources, especially the geothermal water around 50℃, usually only provide hot spring bathing and planting and breeding, and rarely used for heating. This is mainly because the old heating radiator heating supply and return water temperature requirements are high, generally 95 ℃ / 70 ℃, 50 ℃ geothermal water heating through the radiator is difficult to achieve the room temperature requirements. At present, with the floor heating technology, fan coil technology and the development of radiant ceiling technology, heating the required heat source temperature is greatly reduced, generally 40 ~ 45 ℃ to meet the needs of heating. As a result, geothermal direct heating and ground source heat pump technology heating provides a broad market space.
Beijing shunyi jinhan green harbor home district, is our hospital undertook a use of low-temperature geothermal resources heating and provide hot springs bathing geothermal comprehensive utilization of engineering. The project adopts radiant floor heating at the indoor end, utilizes heat pump technology, and basically solves the heating and hot spring bathing needs of the residential community of 230,000m2 with three geothermal wells, so that the low-temperature geothermal resources are effectively used. The use of clean geothermal energy heating, hot springs into the home, greatly improving the quality of housing, not only to the residents of the community to provide a good living environment and the quality of the atmosphere, but also gives the developer a generous return.
2 Project Overview
Jinghan Green Harbor Homes is a large-scale comprehensive residential district integrating residential, hotel, catering and entertainment. The total building area is 630,000 m2, the first phase of the building is 230,000 m2, and the public building area is 30,000 m2. The total heating load and the cold load of the public building part of the Jinhan Green Harbor Homes are as follows: Heating load: the heat index of the unit area in winter is 41W/m2, which is a total of 9,430kW; the public building part of the building is: the refrigeration index of the unit in summer is 80W/m2, which is a total of 2,400kW.
According to the above heat and cooling According to the above cooling and heating indicators and the geological conditions of the site, the institute proposes to utilize the geothermal hot spring wells combined with water source heat pump technology to provide heating and hot spring bathing in winter, and adopt the radiant floor heating at the end of the heating room; and utilize the water source heat pump unit and cold water wells to provide cooling for the public building part in summer, and adopt the fan coil tubes at the end of the building. The project is a comprehensive utilization of deep geothermal energy and shallow geothermal energy.
3 Determination of water required for heating and cooling
3.1 Derivation of the relationship between heating and cooling area and water volume
According to the law of conservation of energy, the relationship between the heating area and the water volume of the required geothermal spa wells can be derived, and from this, the amount of groundwater required can be determined according to the heating area; similarly, the amount of water and the water temperature of the geothermal wells can be determined according to the area capable of heating. area.
a. Direct heating
Shallow geothermal energy: national geothermal (shallow geothermal energy) development and utilization of field experience exchange conference proceedings
In the formula: S is the heating area, m2; q is the heat load per unit area, W/m2; J is the equivalent coefficient of thermal power, 4187 Joule / Daca; ρ is the density of water, 1 T / m3; c is the specific heat capacity of water, 1 × 103kcal / T - card. 103kcal/T-°C; Q is the water output from the geothermal well, m3/h; t1 is the output water temperature of the geothermal well, ℃; t2 is the water temperature of the tail water after heating, ℃.
b. Combined with heat pump technology heating
Shallow geothermal energy: Proceedings of the National Conference on the Exchange of Field Experiences in the Development and Utilization of Geothermal Heat (Shallow Geothermal Energy)
Formulas: cop is the heat supply coefficient of the heat pump unit, which is generally 4; t3 is the temperature of the tail water after extracting heat through the heat pump, ℃.
By (1), (2) relationship equation can be seen, the area of geothermal well heating and geothermal water volume is directly proportional. The water volume of a certain case, and the utilization of the temperature difference is directly proportional to the temperature difference, that is, the greater the utilization of the temperature difference, the greater the heating area.
Geothermal wells combined with heat pump technology heating, can increase the utilization of geothermal water temperature difference, the corresponding reduction in the demand for geothermal water, so as to achieve the purpose of intensive use of geothermal resources. Such as the relationship (1), (2) in the t2 is generally about 40 ℃, while t3 in about 10 ℃, to improve the utilization of the temperature difference of 30 ℃. For a geothermal well with a water temperature of 70 ℃, through the heat pump technology, can make 1 geothermal well to play the effectiveness of two geothermal wells, not only saves the investment, but also saves the valuable geothermal resources.
3.2 Determination of water volume of the required geothermal wells
It is known that the total heating load of the district is 9430kW; the temperature of the tail water can be lowered to 7℃ after the heat pump unit extracts the heat; according to the analysis of reliable geological data, it is presumed that the volume of water and the prediction of the water temperature of the geothermal wells are 55℃, the volume of water is 60m3/h, and the depth of the well is 3000m, and the purpose of the thermal storage is the Jixian system Wumushan Formation.
According to the well depth of 3000m, the thermal storage destination layer is the Jixian Mushushan Group.
Based on the above known data, the water volume of the required geothermal wells can be derived as: 126m3/h.
3.3 Determination of the water volume of the required cooling wells
Similarly, based on the law of conservation of energy, the relationship between the water volume and the cooling area in the case of cooling of the public building part can be derived as:
Shallow geothermal energy: National Geothermal (Shallow Geothermal Energy) Development and Utilization of Field Experience Proceedings of the National Geothermal (Shallow Geothermal Energy) Development and Utilization Field Experiences
Where: EER is the energy efficiency ratio of the heat pump unit, the ratio of the cooling capacity obtained to the input electricity, generally taken as 5; t1 is the temperature of the water coming out of the cold water wells, ℃; t3 is the temperature of the water at the time of recharging, ℃.
Knowing that the total cooling load of 2400kW; cold water well water temperature of 15 ℃, the amount of water, the depth of the well; recharge temperature of 27 ℃. According to the above known data into the relationship (3), can be obtained 30,000m2 public part of the required water: 206m3 / h.
4 engineering technology program design
The project heating needs temperature 55 ℃ geothermal water flow rate of 126m3 / h, according to the known hydrogeological data can be seen, two geothermal wells can meet the needs of the water. Geothermal wells in the region recharge situation is good, 1 recharge wells can meet the needs. Therefore, the heating project is designed to use three "geothermal wells - heat pump unit" (two pumping and one irrigation) to meet the heating requirements of the first phase of the building of 230,000m2 floor area and the residents of the community's hot springs bathing.
The water volume of the cold wells required for the cooling of the public building part is 206m3/h, while the depth of the wells in the area is 100m, and the water volume can be up to 80m3/h, so the three pumping wells can meet the needs. The recharge situation in this area is general, and the ratio of pumping and irrigation is 1:2, therefore, the total number of cold water wells is 9. Cold water wells and heat pump units are utilized to meet the summer cooling needs of the public building section. The indoor end uses underfloor heating technology, and the end of the public building part uses fan coils.
In order to meet the requirements of the water source heat pump unit evaporator side of the inlet and outlet water temperature, at the same time, because the geothermal well water can not be used directly into the unit, so the geothermal well water through the plate heat exchanger heat exchange, plate heat exchanger, primary side of the inlet water flow rate of 120 tons / hour, the temperature of 55 ° C, the temperature of the water outlet is 9 ° C, the secondary side of the water source heat pump unit side) water flow rate of 750 tons / hour, the inlet temperature is 7 ° C, the outlet temperature is 9 ° C, the water source heat pump unit side of the secondary side of the flow rate of 750 tons / hour. The water flow rate of the secondary side (water source heat pump unit side) is about 750 tons/hour, the inlet water temperature is 7℃, and the outlet water temperature is 15℃. The secondary side of the water can meet the requirements of the total amount of water when the unit is in full operation.
5 Operation cost analysis
5.1 Main equipment and power distribution in the equipment room (Table 1)
Table 1 Main equipment and power distribution in the equipment room
The total amount of other equipments is tentatively estimated to be 150kW, and the total power distribution amount is tentatively estimated to be 2880.2kW. 2880.2kW is the maximum power consumption in winter, and 300kW in summer.< /p>
5.2.2.1 The total water flow is about 750 tons/hour, and the water inlet temperature is 7℃. /p>
5.2 Operation Cost Analysis
Heating operation cost mainly includes the following items: electricity cost, personnel wages and benefits, equipment depreciation, annual maintenance costs, various taxes and fees.
Operation of 6 heat pump units can meet the maximum load, 6 units can provide the maximum heat in winter is 9504kW, winter unit full load operation, the unit itself and its related auxiliary equipment total power consumption of 2880.2kW.
Calculate the winter operating costs based on the above power (2880.2kW) load, set the average daily full-load running time of 12 hours. time is 12 hours. Water source heat pump central air-conditioning heat and cold source program equipment for the annual running cost of electricity: 2.4056 million yuan (winter).
Because the project uses automatic control technology, so the operation requires 6 people to maintain can (three shifts), personnel wages are:
6 people × 4 months × 1,600 yuan / (person-months) = 38,400 yuan
All the equipment for the use of the life of 15 years, the water well for 15 years, the annual depreciation costs are: equipment, 770,000 yuan / year; wells, 830,000 yuan /year; totaling $1.6 million. Maintenance costs are $100,000 per year. Totaling 4.1440 million dollars. The annual running cost per square meter is 18 yuan/m2. At present, the price of central heating in Beijing is 24 yuan/m2, and the price of natural gas heating is 30 yuan/m2. Therefore, the use of geothermal wells combined with water source heat pump technology for urban heating is not only technically feasible, but also has a price advantage.
The district geothermal wells not only as a heat source for heating, but also to provide hot springs bathing community. The use of electric water heaters to heat a ton of tap water needs 23 yuan, gas water heaters need 14 yuan, while the home geothermal hot spring water bathing only need to pay 3.5 yuan per ton of mineral resources tax. When encountering extreme cold weather, heating and bathing water conflict, you can start the cold water well for peak adjustment.
6 Conclusion and revelation
The use of geothermal wells combined with water source heat pump technology for urban heating and the provision of hot springs bathing is technically completely feasible, and the operating costs are also advantageous relative to gas. What's more, geothermal resources are a nearly renewable and clean energy source without any emissions or wastes, which is very conducive to improving the quality of the city's atmosphere.
Geothermal wells combined with heat pump technology heating compared to ordinary water source heat pump heating, but also has the following advantages:
(1) in the heating at the same time, you can take into account the provision of hot springs and bathing;
(2) due to the high water temperature, the corresponding reduction in the amount of water requirements, which reduces the number of wells and reduces the occupation of space;
(3) the depth of geothermal wells Generally around 3000m, the hot water extracted is generally bedrock fissure water, which has almost no effect on the ground subsidence; cold water wells are generally around 80m, most of which extracts pressurized water from Quaternary aquifers, which has a slightly greater relative impact.
The disadvantages are mainly the higher cost of geothermal wells and the higher risk of drilling.
Geothermal wells combined with water-source heat pump heating technology provides a new idea for low-temperature geothermal for heating. Most cities in China have such low-temperature geothermal resources, and if they can be widely utilized, it has a very positive significance for solving urban air pollution, saving energy, and saving land occupation.
References
[1] Chi Shiaojun. Hydrogeology and Engineering Geology. Beijing: Water Resources and Electric Power Press, 1985
[2] Zhou Nianhu. Development and utilization of geothermal resources. Beijing: China Geoscience Press, 2005
[3] Lu Yaocheng. HVAC design guide. Beijing: Architecture Industry Press, 1990
[4] He Manchao et al. Geothermal engineering technology in China with low and medium enthalpy. Beijing: Science Publishing House, 2004
[5] Zhu J. L. et al. Geothermal energy development and application technology. Beijing: Chemical Industry Publishing House, 2006