Utilization of shallow geothermal energy at the Beijing Foreign Language and Culture Press International Conference Center

Pan Xiaoping

(Beijing Institute of Geothermal Engineering)

Abstract The water source heat pump utilization project of shallow geothermal energy in the Beijing Foreign Language and Culture Press International Conference Center has been feasible after two years. After practical demonstration planning, water source drilling construction and equipment installation and commissioning, it was put into operation in the summer of 2004. After three summers and two winters of practice, the cooling and heating effects are good, providing a comfortable environment that is cool in summer and warm in winter, and cooperates with the hot spring entertainment and health care of geothermal wells. services and huge economic benefits. The development and utilization of shallow geothermal energy and conventional geothermal energy have brought unexpected surprises.

1 Preface

Beijing Foreign Language Teaching and Research Press (referred to as "Foreign Language Teaching and Research Press"), in response to the Beijing Municipal Government's call to control air pollution and restore a blue sky to Beijing, plans to publish a press conference at its international conference The center installs a new pollution-free, energy-saving and efficient water-source heat pump air-conditioning system, which utilizes local shallow geothermal energy resources to provide winter heating and summer air-conditioning and cooling for all buildings. The center is located in the northwest of Lucheng Town, Daxing District, Beijing, covering an area of ??89,581.1m2 and a total construction area of ??101,550m2. It is a large-scale engineering project. The feasibility study of the project began in the spring of 2002, construction began in mid-2003, and was completed in June 2004. The project has been running for 3 summers and 2 winters so far. It not only has good heating and cooling effects, but also brings huge economic and environmental benefits.

2 Historical review

The International Conference Center was originally a library of the Beijing Foreign Language and Culture Press in the northwest of Lucheng Town, Daxing District. Later, it built a training base for the Foreign Language and Culture Press and built two training buildings. Teaching buildings, as well as related teachers' apartments and staff and student dormitories and other buildings. The local environment is a vast and sparsely populated area in the outer suburbs. The training base has been greened, and the teaching and living environment conditions are good, but how to create higher economic value is not yet ideal.

With the promotion of Daxing County to Daxing District, Daxing District has set up a development zone in Lucheng, the Fifth Ring Road in Beijing has been built, and new projects such as Tempu Solar Energy Company have been built near the training base. FLTRP planned to improve the level, rename the training base, build an international conference center, and develop business. FLTRP invited famous designers to design a new auditorium and its ancillary parts, including bowling, sauna, fitness facilities and swimming pools, etc. It also renovated and decorated old buildings to form an overall coordination. In addition to these external images, the specific projects to improve the internal quality level are the water source heat pump project using shallow geothermal energy and the icing on the cake geothermal well project.

3 Water source heat pump project utilizing shallow geothermal energy

The water source heat pump project utilizing shallow geothermal energy includes pumping wells and recharge wells that provide shallow geothermal energy, namely The underground part, the water source heat pump unit and the supporting pipe network and control system in the above-ground part.

3.1 Feasibility Study

According to the heating and cooling load requirements, the water source heat pump of this project requires no less than 3600m3 of water supply per day. Are these volumes of water available at the project site? Can all the water pumped out be reinjected back? What is the environmental impact of the project? How to lay a well? How to build a well? These are tasks that heat pump engineering specifications require to be completed by a professional survey team.

The FLTRP Training Base commissioned the Beijing Geothermal Engineering Research Institute to conduct the feasibility study in April 2002. After nearly two months of work, the conclusion of the feasibility study is: at the lower reaches of the local Yongding River, On the ground, the thickness of the aquifer is not large, with a total thickness of only 20m. The underground water depth has reached below 20m, and its upper part has been drained. Fortunately, the aquifer has coarse particles, mainly sand and gravel, and contains a medium-coarse sand layer. Therefore, under normal circumstances, two water supply wells can meet the required water demand. However, in order to leave sufficient room, it is recommended to drill three production wells. The maximum attenuation of the injection wells in the test is 25%. According to 30% Consider it better to arrange 6 recharge wells. There is no water supply source near the work area. The water source heat pump uses local groundwater to pump and irrigate the water from different wells in the same layer, without causing adverse environmental impacts. Wells can be laid out in a scattered manner using the training base, and the distance between wells can be kept at about 100m.

3.2 Construction of pumping and irrigation wells

Drilling construction started on July 16, 2003, and all tasks were completed on January 12, 2004. In order to ensure the long-term sustainable operation of the project in the future, an additional backup well for recharge was considered and 10 wells were drilled (Figure 1).

The well depth is 40 to 42m, mainly using the water-bearing sand gravel layer or pebble layer below the water level. After the aquifer of more than 30 m is terminated, about 8 m of sedimentation pipe space is left to form the well. The drilling diameter is ?800mm, and ?426mm well casing (upper section 8~12m) and water filter pipe (lower section) are run in. The shallow fine and medium sand layer is not used. The drilling project is carefully constructed, gravel is strictly filled, and the wells are carefully washed to ensure that the water is clean and the sand content is less than 1/200,000. All are high-quality wells.

Figure 1 Schematic diagram of water source heat pump system pumping and recharge lines

The local groundwater level is about 21m deep. The water output of a single well in the pumping test is basically 85 to 90m3/h, and the unit water inflow is Most of them are between 7 and 24m3/h·m, and the outlet water temperature is 14℃. Before the end of the pumping test, a water sample was taken for drinking water quality testing. It is a calcium and magnesium carbonate water type with a pH value of 7.5, total dissolved solids of 0.91 to 0.97 g/L, and metasilicic acid content of 20.5 to 21.8 mg/L. In addition to total hardness Except for 485~490mg/L (CaCO3), which exceeds the drinking water standard (450mg/L CaCO3), the rest are in compliance with the standards and are non-scaling and non-corrosive.

3.3 Installation of water source heat pump system

The water source heat pump system uses heat pump products from CLIMAVENETA, Italy, with 4 sets of units separated into two operating rooms. , respectively controlling two systems of the hotel part and the recreational part. The model specifications of the heat pump unit are listed in Table 1.

Table 1 Model specifications of Clemento heat pump unit (operating fluid R22)

3.4 Operation

The operation of the water source heat pump system is to turn on the heat pump At the same time as the unit is running, the pumping well must be started to deliver water to the unit, and the circulating water must also be directed to the recharge well for recharge. In winter heating mode, the groundwater entering the unit supplies heat and is recharged after the temperature drops. In the summer cooling mode, the groundwater entering the unit absorbs heat and is recharged after the temperature rises. In order to prevent the recharge water from forming local cold or hot masses underground, and to prevent the recharge wells from being clogged due to long-term use, the recharge wells need to be pumped back and pumped regularly. Taking these factors into consideration, FLTRP has made a decision on the water source heat pump project. The 10 wells are opened and closed in turns, and the production wells and recharge wells are used alternately. It was originally considered to open 3 pumping wells and 5 to 6 recharge wells to meet all water needs and recharge. However, in the actual project, two heat pump rooms were split and run separately. Therefore, the water volume cannot be uniformly allocated and each needs to work independently. Therefore, the actual operation situation is: in the early cold and late cold periods, it is enough to open 1 pumping well and 2 recharge wells in each of the two heating machine rooms; in the severe cold period, it is basically necessary to open 2 pumping wells and 3 recharge wells in each. Irrigating, pumping, and filling wells are basically rotated every one to two weeks.

The water source heat pump system of FLTRP has been running for 3 summers and 2 winters, about 240 days a year: winter heating starts at the end of October or early November and ends at the end of March of the following year, lasting about 150 days, which is more normal than Beijing The heating period is extended by half a month each; summer cooling starts in early June and ends at the end of August, which lasts about 90 days.

3.5 Effects and changes

According to monitoring data such as operation shift reports, because the water source entering the water source heat pump is sufficient, and one production well is basically linked to two recharge wells, the recharge It is relatively smooth, so the system runs quite stably, and the heat pump efficiency is obvious. The room temperature in winter and summer can be around 21°C. It is warm and comfortable in winter, and cool and refreshing in summer. Such comfortable environmental hardware and software conditions have attracted a large number of customers to the International Convention Center.

As a water source heat pump, one should also consider whether it can operate sustainably. The essence is whether the local ground temperature can be restored regularly. According to temperature monitoring data, at the beginning of winter heating of the year (November), the local ground temperature is 14°C. The temperature of the groundwater pumped into the water source heat pump unit is reduced by 5 to 7°C after heat is extracted. The outlet temperature of the heat pump is lower than the import temperature. The temperature rises by 2 to 3°C to about 46°C, and the building is heated through the fan coil; in the following 2, 3, 4, and 5 months, the temperature of the groundwater pumped into the water source heat pump unit basically decreases by 1°C per month , that is, it is roughly 13°C, 12°C, 11°C, and 10°C month by month. After the heat is extracted, the temperature decrease gradually decreases accordingly, from 5 to 7°C to 3 to 5°C, but the heat pump outlet temperature basically remains unchanged. .

After 2 months of rest, summer cooling begins, and the ground temperature returns to slightly lower than 12°C. After the water source heat pump unit absorbs the heat, the temperature rises by 2 to 6°C, and the outlet temperature of the heat pump manufactured by it can be 3 to 4°C lower than the inlet temperature. , dropped to about 6°C, and the building was cooled through the fan coil; in the following 2 and 3 months, the temperature of the groundwater pumped into the water source heat pump unit basically increased by 2°C every month, that is, 14 ℃, 16 ℃, but the outlet temperature of the heat pump unit remains basically unchanged. The groundwater temperature returns to its original temperature of 14°C after a 2-month rest and when heating begins. This completes the year-long cyclical change and achieves the goal of sustainable development of shallow geothermal energy.

4 The icing on the cake is to drill a geothermal well

Following the "hot spring craze" in the Beijing-Tianjin area in recent years, geothermal water is used to operate hot spring leisure, health care, entertainment, tourism, and conference operations. As the icing on the cake, FLTRP also considered adding geothermal well development projects when executing its water source heat pump project tasks. In the summer of 2003, FLTRP commissioned the Beijing Geothermal Engineering Research Institute to conduct a feasibility study on geothermal well drilling. The feasibility study report was completed in July, and it was deemed that FLTRP has the conditions to drill a geothermal well. FLTRP made a prompt decision and immediately organized geothermal well construction. The well team entered the site on September 26, and the construction was completed on February 6 of the following year. The drilling of the "Xingre-6" well was completed. The designed drilling length was 2,600m, and the actual drilling was drilled as designed. The Tieling Formation and Shuishizhuang Formation of the Quaternary System, Tertiary System, Cambrian System and Jixian System were covered with a total thickness of 1747.5m (although part of the aquifer was included), casing was lowered in sections and cement cementing was carried out , and finally the open hole was drilled into the siliceous dolomite thermal reservoir of the Wumishan Formation in the Jixian System, and the well was completed at the final hole of 2601.88m. The water output temperature of the well was 51°C, and the water output was 1979.42m3/d.

The temperature of this geothermal well is not very high, so it is difficult to use it for heating, and there is already a water source heat pump for heating. Therefore, FLTRP used this well to build a hot spring swimming pool, sauna and fitness center, in conjunction with the water source heat pump project. It provides a comfortable environment in all seasons of winter and summer, as well as leisure, entertainment and health care services. Although the International Convention Center is located in a relatively remote location outside the Fifth Ring Road, it continues to attract people from all walks of life. Of course, it also brings a steady stream of money.

5 Conclusion

The water source heat pump project of Beijing FLTRP International Conference Center has achieved unexpected surprises for the developers.

(1) After three summers and two winters of practice, the cooling and heating effects of shallow geothermal energy are good, providing a comfortable environment that is cool in summer and warm in winter.

(2) In conjunction with the hot spring leisure, entertainment and health care services provided by the completed geothermal well, the quality will be further improved, and there will be a large number of customers all year round, bringing huge economic benefits.

(3) Monitoring data show that the underground temperature can cycle over and over during annual operation, meeting the requirements for sustainable utilization.