Geothermal collection system and methods of construction and use thereof

Abstract

The application discloses a geothermal collection system and a construction and use method thereof. The geothermal collection system comprises a plurality of prefabricated geothermal energy piles. An enlarged cavity space is formed below each geothermal energy pile, and the enlarged cavity space is filled with circulating water for geothermal heat exchange. A circulating water cavity is arranged in the prefabricated geothermal energy pile. A heat exchange mechanism for heat exchange between the circulating water cavity and the enlarged cavity space is arranged in the prefabricated geothermal energy pile. The heat exchange mechanism comprises a heat exchange pipe in the circulating water cavity and a heat exchange net in the enlarged cavity space. A releasing mechanism for releasing the heat exchange net after the construction of the energy pile is completed is arranged in the prefabricated geothermal energy pile. The heat exchange structure is integrated into the prefabricated geothermal energy pile, so that the energy pile can be used as a structural component and a heat exchange component, and thus, additional drilling or excavation for installing a ground source heat pump system is not needed, and land cost and installation cost are saved.

Description

Technical Field

[0001] This invention relates to the field of geothermal collection and utilization technology, specifically to a geothermal collection system and its construction and usage methods. Background Technology

[0002] Compared to fossil fuel combustion and traditional air-source heat pumps, ground-source heat pump systems reduce carbon emissions and environmental pollution. Traditional ground-source heat pump systems use closed heat absorption pipes buried in horizontal trenches or vertical boreholes. As needed, antifreeze is circulated through these pipes to transfer shallow geothermal energy from the geothermal source to the ground (in winter) or store ground heat energy at the geothermal source (in summer). Installing a ground-source heat pump system requires additional drilling and excavation beyond its inherent structural purpose, and the large amount of additional land use and high installation costs make this technology difficult to widely adopt.

[0003] Energy piles are a new application in ground source heat pump systems, integrating geothermal heat exchangers into the foundation structure. Compared to traditional ground source heat pump systems, energy piles serve as both structural and heat exchange components, eliminating the need for additional drilling or excavation for system installation, thus saving on land and installation costs.

[0004] Currently, there are two main types of geothermal piles: cast-in-place piles and precast piles. Groundwater seeping into the bottom of the pile is extracted through a pumping pipe. However, when groundwater resources are not abundant, the extracted groundwater and its heat are very limited, making it impossible to obtain geothermal resources through groundwater and thus impossible to effectively collect and utilize geothermal energy. Summary of the Invention

[0005] Technical objective: To address the shortcomings of existing geothermal collection methods, this invention discloses a geothermal collection system and its construction and usage methods.

[0006] Technical solution: To achieve the above technical objectives, the present invention adopts the following technical solution:

[0007] A geothermal collection system includes several prefabricated geothermal energy piles. An enlarged cavity space is formed beneath each geothermal energy pile, and the enlarged cavity space is filled with circulating water for geothermal heat exchange. A circulating water cavity is provided inside each prefabricated geothermal energy pile, and a heat exchange mechanism is installed within the prefabricated geothermal energy pile for heat exchange between the circulating water cavity and the enlarged cavity space. Circulating water is introduced into the enlarged cavity space through the circulating water cavity for geothermal heat exchange. The heat exchange mechanism includes heat exchange pipes located within the circulating water cavity and heat exchange mesh located within the enlarged cavity space. The injection and extraction of circulating water into the enlarged cavity space through the heat exchange pipes form a geothermal utilization cycle. A release mechanism is provided within the prefabricated geothermal energy pile for releasing the heat exchange mesh after the energy pile construction is completed.

[0008] Preferably, the release mechanism of the present invention includes a heat exchange mesh storage cavity, in which a release piston is disposed. The release piston is slidably connected to the heat exchange mesh storage cavity. The cavity on the side of the release piston facing away from the heat exchange mesh is connected to the heat exchange tube. Water is injected into the heat exchange tube to push the release piston to move and release the heat exchange mesh.

[0009] Preferably, the heat exchange mesh of the present invention is formed by copper wire weaving into a mesh bag. One end of the mesh bag is fixedly connected to the end of the release piston, and the other end is a free end that is pushed out of the heat exchange mesh storage cavity into the expansion cavity space for release. The inner and outer surfaces of the heat exchange mesh are sprayed with water-soluble polymer. The release piston and the heat exchange mesh storage cavity are connected by a communication mechanism to allow water to enter the heat exchange mesh for expansion after the release piston pushes the heat exchange mesh to release.

[0010] Preferably, the release piston of the present invention adopts an I-shaped structure, and the two ends of the release piston slide in conjunction with the heat exchange mesh storage cavity. The communication mechanism includes a water channel opened on the inner wall of the heat exchange mesh storage cavity and located on the sliding path of the release piston, and a communication hole opened at the connection end between the release piston and the heat exchange mesh. After the end of the release piston moves to the position of the water channel, the water flows from the water channel into the interior of the heat exchange mesh.

[0011] Preferably, after the prefabricated geothermal energy pile of the present invention is constructed, water is filled into the heat exchange net storage cavity through the heat exchange pipe. Under the action of water pressure, the release piston is pushed to push the heat exchange net out of the heat exchange net storage cavity. After the end of the release piston moves to the water channel, the release piston stops moving. Water flows from the water channel to the connecting hole at the end of the release piston and enters the heat exchange net. The water-soluble polymer of the inner and outer layers of the heat exchange net prevents water from flowing out of the heat exchange net. The water flow expands the heat exchange net.

[0012] Preferably, the present invention provides a flow chamber below the heat exchange network storage chamber along the height direction of the prefabricated geothermal energy pile for allowing water in the heat exchange tube to flow directly into the expanded cavity space. The flow chamber is connected to the end of the heat exchange tube. A water-soluble polymer one-way valve core is provided at the outlet of the flow chamber. The water-soluble polymer one-way valve core restricts water from flowing out of the flow chamber before dissolving.

[0013] Preferably, the prefabricated geothermal energy pile of the present invention has a central hole concentrically provided for the entry and exit of the drilling end of the drilling equipment. The drilling equipment includes a core tube, and drill rods are symmetrically hinged at the ends of the core tube. Alloy cutter heads are provided at the ends of the drill rods. A retraction mechanism is provided inside the core tube for adjusting the angle of the drill rods relative to the core tube to change the drilling radius.

[0014] Preferably, the launching and retracting mechanism of the present invention includes an intermediate top rod coaxially arranged with the core tube and a support rod whose end is rotatably engaged with the intermediate top rod. The other end of the support rod is hinged to the drill rod. By adjusting the axial position of the intermediate top rod relative to the core tube, the support rod is moved to adjust the position of the drill rod and thus adjust the drilling range.

[0015] This invention discloses a construction method based on the above-mentioned geothermal collection system. A drilling device is used to drill a hole below a precast geothermal energy pile. The precast geothermal energy pile is pressed down by a precast pile static press and moved down along the drilling path of the drilling device for construction and installation. After reaching the installation depth, the drilling device changes the drilling radius to create an enlarged cavity space below the precast geothermal energy pile to accommodate groundwater. Then, the drilling device is removed from the precast geothermal energy pile. Finally, water is filled into the heat exchange pipe of the precast geothermal energy pile to release and expand the heat exchange network and inject water into the enlarged cavity space, allowing the heat exchange network to be distributed within the enlarged cavity space and contact the circulating water for heat exchange.

[0016] Preferably, after the prefabricated geothermal energy pile is constructed, the heat exchange network absorbs geothermal heat from the circulating water in the enlarged cavity space and conducts it to the prefabricated geothermal energy pile through the heat exchange pipe. At the same time, the circulating water in the enlarged cavity space absorbs geothermal heat synchronously, and conducts the geothermal heat to the ground through the heat exchange pipe itself and the circulating water after heat exchange absorbed by the heat exchange pipe.

[0017] Beneficial effects: The geothermal collection system and its construction and use method disclosed in this invention have the following beneficial effects:

[0018] 1. The present invention uses a heat exchange net that can be released after the construction of prefabricated geothermal energy piles to circulate in the enlarged cavity space for heat exchange, which can effectively increase the heat exchange contact area and thus improve the geothermal collection efficiency.

[0019] 2. The heat exchange mesh of the present invention uses copper wire to form a mesh bag structure. Combined with the water-soluble polymer brushed on the inner and outer surfaces of the mesh bag, the mesh bag can be in a contracted state before release, which is convenient for construction and installation. At the same time, after construction is completed, the water flow filled into the mesh bag is used to assist in the expansion of the heat exchange mesh, so that it can be unfolded in the expanded cavity space, thereby improving the subsequent heat exchange and heat transfer effect.

[0020] 3. Through the structural design of the release piston and the heat exchanger storage chamber, this invention enables the release piston to automatically switch the heat exchanger release after sliding to the release position. This ensures the reliability of the heat exchanger release and deployment operation in a closed underground space, reduces the difficulty of construction control, and achieves the switching based on the mechanical structure design without the need for complex electrical or pneumatic facilities. This simplifies the internal structure of the prefabricated geothermal energy pile, facilitates processing and manufacturing, and reduces the difficulty of construction.

[0021] 4. The present invention provides a flow chamber below the heat exchange mesh storage chamber. The water-soluble polymer one-way valve core in the flow chamber can restrict water from flowing directly out of the heat exchange tube. Water can then enter the chamber through the connection between the heat exchange tube and the heat exchange mesh storage chamber, providing water pressure to push the release piston to move and enter the heat exchange mesh to open the heat exchange mesh using water pressure.

[0022] 5. The present invention uses a retractable drilling device that enters and exits through the central hole of the prefabricated geothermal energy pile. During the drilling process, the prefabricated geothermal energy pile is pressed in simultaneously. After the energy pile is installed, the drilling device opens an enlarged cavity space to form a geothermal collection area under each prefabricated geothermal energy pile. The geothermal energy is collected and utilized using the filled circulating water. In areas with abundant geothermal resources but lack of groundwater, geothermal energy can still be effectively collected and utilized, unaffected by the geological environment.

[0023] 6. The retraction mechanism of the present invention drives the support rod to move through the middle top rod, thereby changing the angle of the two drill rods hinged to the core drill rod, and thus changing the drilling range of the drill rod. This allows for flexible adjustment of the borehole diameter to meet the drilling needs at different stages of the precast geothermal energy pile construction process. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0025] Figure 1 This is a schematic diagram of the prefabricated geothermal energy pile structure of the present invention;

[0026] Figure 2 For the present invention along Figure 1 Enlarged view of a portion of region A in the middle;

[0027] Figure 3 For the present invention along Figure 1 BB section view;

[0028] Figure 4 This is a diagram showing the release state of the heat exchanger mesh of the present invention;

[0029] Among them, 1-prefabricated geothermal energy pile, 2-expanded cavity space, 3-circulating water cavity, 4-heat exchange tube, 5-heat exchange mesh, 6-heat exchange mesh storage cavity, 7-release piston, 8-water passage, 9-connecting hole, 10-flow cavity, 11-water-soluble polymer one-way valve core, 12-drill core tube, 13-drill rod, 14-alloy cutter head, 15-intermediate top rod, 16-support rod, 17-end plate, 18-sealing plate, 19-drainage pipe, 20-high pressure water gun pipe. Detailed Implementation

[0030] Reference will now be made in detail to embodiments of the present disclosure, one or more of which are set forth herein. Each embodiment and example is provided by way of explanation of the apparatus, composition, and materials of the present disclosure, and not by way of limitation. Rather, the following description provides convenient illustrations for implementing exemplary embodiments of the present disclosure. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made to the teachings of the present disclosure without departing from the scope or spirit of the present disclosure.

[0031] like Figures 1-4 As shown, this invention discloses a geothermal collection system, including a plurality of prefabricated geothermal energy piles 1. An enlarged cavity space 2 is opened below each geothermal energy pile 1, and the enlarged cavity space 1 is filled with circulating water for geothermal heat exchange. A circulating water cavity 3 is set inside the prefabricated geothermal energy pile 1, and a heat exchange mechanism is set inside the prefabricated geothermal energy pile 1 for heat exchange between the circulating water cavity 3 and the enlarged cavity space 2. Circulating water is introduced into the enlarged cavity space 2 through the circulating water cavity 3 for geothermal heat exchange. The prefabricated geothermal energy pile 1 is used to collect geothermal energy in the corresponding area. The collection method is circulating water heat exchange, so that the circulating water can be drawn out for direct use of geothermal energy. The heat exchange mechanism includes a heat exchange pipe 4 located in the circulating water cavity 3 and a heat exchange net 5 located in the enlarged cavity space 2. A release mechanism is set inside the prefabricated geothermal energy pile 1 for releasing the heat exchange net 5 after the energy pile construction is completed.

[0032] Since the heat is absorbed solely from groundwater through circulating water, the contact area between the heat pipes and the geothermal groundwater within the prefabricated geothermal energy pile 1 is limited. Furthermore, relying solely on the energy pile's natural heat transfer is insufficient for rapid heat exchange. Therefore, this invention employs a heat exchange mesh 5 to absorb heat from the groundwater, enabling rapid heat transfer through the heat exchange pipes to the surface heat exchanger. Both the heat exchange mesh 5 and the heat exchange pipes 4 are made of thermally conductive metal, preferably copper. Four sets of heat exchange pipes 4 are evenly distributed along the circumference of the prefabricated geothermal energy pile 1, with the number of heat exchange meshes 5 corresponding to the number of heat exchange pipes 4. Because the heat exchange mesh 5 is made of metal, it cannot automatically expand after release; therefore, a structure to assist in its expansion is also required. Figure 1 The heat exchange mesh 5 on the right side is in an open state and can be distributed within the enlarged cavity space 2 to exchange heat with the internal groundwater.

[0033] like Figure 2As shown, in an embodiment of the present invention, the release mechanism includes a heat exchange mesh storage cavity 6, and a release piston 7 is disposed within the heat exchange mesh storage cavity 6. The release piston 7 is slidably connected to the heat exchange mesh storage cavity 6. The cavity on the side of the release piston 7 facing away from the heat exchange mesh 5 is connected to the heat exchange tube 4. Water is injected into the heat exchange tube 4 to push the release piston 7 to move and release the heat exchange mesh 5. The water pressure generated by the continuous water flow input through the heat exchange tube 4 pushes the release piston 7 to move. The heat exchange mesh 5 of the present invention is formed into a mesh bag by copper wire weaving. One end of the mesh bag is fixedly connected to the end of the release piston 7, and the other end is a free end that is pushed out of the heat exchange mesh storage cavity 6 into the expanded cavity space 2 for release. The inner and outer surfaces of the heat exchange mesh 5 are sprayed with a water-soluble polymer. The release piston 7 and the heat exchange mesh storage cavity 6 are connected to the heat exchange mesh 5 after the release piston 7 pushes the heat exchange mesh 5 to release, so that water enters the heat exchange mesh 5 to expand the heat exchange mesh. To prevent the water-soluble polymer from dissolving prematurely and affecting the opening of the heat exchanger, the present invention also provides a rubber stopper at the outlet of the heat exchanger storage cavity 6. The rubber stopper prevents water from entering and contacting the water-soluble polymer on the surface of the heat exchanger before release.

[0034] like Figure 2 and Figure 4 As shown, the release piston 7 of the present invention adopts an I-shaped structure. The two ends of the release piston 7 are slidably engaged with the heat exchange mesh storage cavity 6. The communication mechanism includes a water channel 8 opened on the inner wall of the heat exchange mesh storage cavity and located on the sliding path of the release piston 7, and a communication hole 9 opened at the connection end between the release piston 7 and the heat exchange mesh 5. After the end of the release piston 7 moves to the position of the water channel 8, the water flows from the water channel 8 into the interior of the heat exchange mesh 5. In addition to serving as a channel for water flow, the water channel 8 can also control the sliding distance of the release piston 7 by opening its position, so as to control the release position of the heat exchange mesh. A push rod for pushing open the rubber stopper can also be provided at the end of the release piston 7 near the rubber stopper. The push rod moves synchronously with the release piston 7 to avoid the rubber stopper 7 from obstructing the release of the heat exchange mesh 5. Figure 2 The heat exchanger 5 is in an unreleased state, located within the heat exchanger storage chamber 6. Figure 4 When the heat exchanger 5 is in the release state, the release piston moves to the water tank 8, and the connecting hole 9 and the water tank 8 form a passage.

[0035] After the prefabricated geothermal energy pile 1 of the present invention is constructed, water is filled into the heat exchange mesh storage cavity 6 through the heat exchange pipe 4. Under the action of water pressure, the release piston 7 is pushed to push the heat exchange mesh 5 out of the heat exchange mesh storage cavity 6. After the end of the release piston 7 moves to the water channel 9, the release piston 7 stops moving. Water flows from the water channel 8 to the connecting hole 9 at the end of the release piston 7 and enters the heat exchange mesh 5. The water-soluble polymer of the inner and outer layers of the heat exchange mesh 5 prevents water from flowing out of the heat exchange mesh 5. Under the action of water pressure, the heat exchange mesh can be expanded in a short time, so that the heat exchange mesh 5 can fill into the enlarged cavity space. The water-soluble polymer will continue to dissolve, so that the water can flow normally through the mesh of the heat exchange mesh 5.

[0036] In this invention, a flow chamber 10 is also provided below the heat exchanger storage chamber 6 along the height direction of the prefabricated geothermal energy pile. This flow chamber 10 allows water from the heat exchanger tube 4 to flow directly into the enlarged chamber space 2. The flow chamber 10 is connected to the end of the heat exchanger tube 4. A water-soluble polymer one-way valve core 11 is provided at the outlet of the flow chamber 10. Before dissolving, the water-soluble polymer one-way valve core 11 restricts the flow of water from the flow chamber 10. In the initial stage, water cannot flow out of the flow chamber 10 and will enter the heat exchanger storage chamber 6 above through the heat exchanger tube 4, generating water pressure to release and expand the heat exchanger. At this time, the release piston 7 and other structures still exert pressure on the water. The flow generates a certain resistance, preventing rapid flow. However, after the water-soluble polymer one-way valve core 11 dissolves, the water flows directly out of the flow chamber 10. The resistance here is small, allowing for rapid water injection to fill the enlarged cavity space 2, thereby improving overall construction efficiency and shortening the time. The flow chamber 10 is formed by the end cap plate 17 and the sealing plate 18 of the L-pile at the end of the prefabricated geothermal energy pile 1. The outlet of the flow chamber 10 is along the radial direction of the prefabricated geothermal energy pile 1. Water injection can clean impurities in the enlarged cavity space, and sewage can be discharged in conjunction with the sewage pipe 19 installed in the prefabricated geothermal energy pile 1.

[0037] To facilitate the opening of the enlarged cavity space 2 and the simultaneous installation of the prefabricated geothermal energy pile 1, the prefabricated geothermal energy pile 1 of the present invention has a central hole concentrically arranged inside for the entry and exit of the drilling equipment. The drilling equipment includes a core tube 12, with a drill rod 13 symmetrically hinged at the end of the core tube 12. An alloy cutter head 14 is provided at the end of the drill rod 13. A retraction mechanism is provided inside the core tube 12 for adjusting the angle of the drill rod 13 relative to the core tube 12 to change the drilling radius. A drain pipe 19 passes through the core tube 12, and a high-pressure water gun pipe 20 is provided inside the core tube 12, reaching the alloy cutter head 14. When cutting hard rock, the high-pressure water gun cools the cutter head on the one hand, and on the other hand, it plays the role of high-pressure water cutting, assisting in drilling.

[0038] The retraction mechanism of the present invention includes an intermediate top rod 15 coaxially arranged with the core tube 12 and a support rod 16 whose end is rotatably engaged with the intermediate top rod 15. The other end of the support rod 16 is hinged to the drill rod 13. By adjusting the axial position of the intermediate top rod 15 relative to the core tube 12, the support rod 16 is moved to adjust the position of the drill rod 13 to adjust the drilling range. After drilling is completed, the two adjusting drill rods 13 can be retracted to a vertical position so that they can be moved out of the prefabricated geothermal energy pile 1 together with the core tube 12. This can ensure the synchronization of drilling and pile driving processes, improve construction efficiency, and ensure that the enlarged cavity space 2 generated by drilling can maintain the position corresponding to the prefabricated geothermal energy pile 1, so as to realize the effective collection and utilization of geothermal energy in various locations of the geothermal area.

[0039] This invention also discloses a construction method based on the above-mentioned geothermal collection system. A drilling device is used to drill a hole below a precast geothermal energy pile. The precast geothermal energy pile is pressed down by a precast pile static press and moved down along the drilling path of the drilling device for construction and installation. After reaching the installation depth, the drilling device changes the drilling radius to create an enlarged cavity space below the precast geothermal energy pile to accommodate groundwater. Then, the drilling device is removed from the precast geothermal energy pile. Finally, water is filled into the heat exchange pipe of the precast geothermal energy pile to release and expand the heat exchange network and inject water into the enlarged cavity space, allowing the heat exchange network to be distributed within the enlarged cavity space and contact the groundwater for heat exchange.

[0040] During pile driving, the drilling equipment rotates at low speed to drill the hole. Every 2-3 meters, the precast pile static pressure machine applies static pressure to the precast geothermal energy pile for another 2-3 meters until the designed pile bottom elevation is reached. Pressure is applied to the central top rod of the drill bit mechanism, and the rotation speed of the core tube is increased. Due to the support of the bottom central top rod 15, the retraction mechanism is forcibly opened, and the drill rod 13 also naturally expands under the action of centrifugal force. Thus, under the simultaneous cutting of the alloy cutter head and high-pressure water jet, an enlarged cavity space is formed at the bottom. After drilling is completed, the core tube is directly used as a sewage pipe, and a water pump is used to pump all the debris and sewage in the enlarged cavity space to the ground, reducing the impact on the later use of the heat exchange equipment. Water can also be injected through the high-pressure water jet to circulate and flush the enlarged cavity space for more thorough sewage removal. Then, the drilling equipment is lifted out of the ground.

[0041] This invention discloses a method for using the aforementioned geothermal collection system. After the prefabricated geothermal energy pile is constructed, the heat exchange network absorbs geothermal heat from the circulating water in the enlarged cavity space and conducts it to the prefabricated geothermal energy pile through heat exchange pipes. Simultaneously, circulating water is drawn from the enlarged cavity space through the heat exchange pipes to conduct geothermal heat to the ground. In cases of groundwater scarcity, this invention can supplement the geothermal energy by injecting water into the enlarged cavity space through the heat exchange pipes, solving the problem of insufficient groundwater resources and ineffective geothermal utilization. It also solves the problem of difficult pile driving in hard rock formations. The geothermal collection system of this invention integrates the heat exchange structure into the prefabricated geothermal energy pile 1. The energy pile serves as both a structural component and a heat exchange component, thus eliminating the need for additional drilling or excavation for installing a ground source heat pump system, saving land and installation costs. The geothermal heat exchange of the circulating water and the heat conduction of components such as the heat exchange network occur simultaneously, improving the efficiency of geothermal collection and utilization.

[0042] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A geothermal harvesting system, characterized in that, The system includes several prefabricated geothermal energy piles (1), with an enlarged cavity space (2) below each geothermal energy pile (1). The enlarged cavity space (2) is filled with circulating water for geothermal heat exchange. A circulating water cavity (3) is set inside the prefabricated geothermal energy pile (1). A heat exchange mechanism is set inside the prefabricated geothermal energy pile (1) for heat exchange between the circulating water cavity (3) and the enlarged cavity space (2). Circulating water is introduced into the enlarged cavity space (2) through the circulating water cavity (3) for geothermal heat exchange. The heat exchange mechanism includes a heat exchange pipe (4) in the circulating water cavity (3) and a heat exchange net (5) in the enlarged cavity space (2). Circulating water is injected into and drawn into the enlarged cavity space (2) through the heat exchange pipe (4) to form a geothermal utilization cycle. A release mechanism is set inside the prefabricated geothermal energy pile (1) for releasing the heat exchange net (5) after the energy pile construction is completed. The release mechanism includes a heat exchange mesh storage cavity (6), and a release piston (7) is provided in the heat exchange mesh storage cavity (6). The release piston (7) is slidably connected to the heat exchange mesh storage cavity (6). The cavity on the side of the release piston (7) facing away from the heat exchange mesh (5) is connected to the heat exchange tube (4). Water is injected into the heat exchange tube (4) to push the release piston (7) to move and release the heat exchange mesh (5). The heat exchange mesh (5) is woven from copper wire to form a mesh bag. One end of the mesh bag is fixedly connected to the end of the release piston (7), and the other end is a free end that is pushed out of the heat exchange mesh storage cavity (6) and enters the expansion cavity space (2) for release. The inner and outer surfaces of the heat exchange mesh (5) are sprayed with water-soluble polymer. The release piston (7) and the heat exchange mesh storage cavity (6) are connected to each other after the release piston (7) pushes the heat exchange mesh (5) to release, so that water enters the heat exchange mesh (5) for heat exchange mesh expansion.

2. The geothermal harvesting system according to claim 1, characterized in that, The release piston (7) adopts an I-shaped structure. Both ends of the release piston (7) are slidably engaged with the heat exchange mesh storage cavity (6). The communication mechanism includes a water channel (8) opened on the inner wall of the heat exchange mesh storage cavity and located on the sliding path of the release piston (7) and a communication hole (9) opened at the connection end between the release piston (7) and the heat exchange mesh (5). After the end of the release piston (7) moves to the position of the water channel (8), the water flows from the water channel (8) to the interior of the heat exchange mesh (5).

3. A geothermal collection system according to claim 2, characterized in that, After the prefabricated geothermal energy pile (1) is completed, water is filled into the heat exchange network storage chamber (6) through the heat exchange pipe (4). Under the action of water pressure, the release piston (7) is pushed out of the heat exchange network (5) from the heat exchange network storage chamber (6). After the end of the release piston (7) moves to the water channel (8), the release piston (7) stops moving. Circulating water flows from the water channel (8) to the connecting hole (9) at the end of the release piston (7) and enters the heat exchange network (5). The water-soluble polymer of the inner and outer layers of the heat exchange network (5) prevents water from flowing out of the heat exchange network (5). The heat exchange network (5) is expanded by the water flow.

4. A geothermal harvesting system according to claim 1, characterized in that, Along the height direction of the prefabricated geothermal energy pile, a flow chamber (10) is provided below the heat exchange network storage chamber (6) to allow water in the heat exchange tube (4) to flow directly into the enlarged chamber space (2). The flow chamber (10) is connected to the end of the heat exchange tube (4). A water-soluble polymer one-way valve core (11) is provided at the outlet of the flow chamber (10). The water-soluble polymer one-way valve core (11) restricts water from flowing out of the flow chamber (10) before dissolving.

5. A geothermal harvesting system according to claim 1, characterized in that, The prefabricated geothermal energy pile (1) has a concentric central hole for the drilling end of the drilling equipment to enter and exit. The drilling equipment includes a core tube (12), and a drill rod (13) is symmetrically hinged at the end of the core tube (12). An alloy cutter head (14) is provided at the end of the drill rod (13). The core tube (12) is provided with a retraction mechanism for adjusting the angle of the drill rod (13) relative to the core tube (12) to change the drilling radius.

6. A geothermal collection system according to claim 5, characterized in that, The take-up and take-down mechanism includes an intermediate top rod (15) coaxially arranged with the core tube (12) and a support rod (16) whose end is rotatably engaged with the intermediate top rod (15). The other end of the support rod (16) is hinged to the drill rod (13). By adjusting the axial position of the intermediate top rod (15) relative to the core tube (12), the support rod (16) is moved to adjust the position of the drill rod (13) and thus adjust the drilling range.

7. A construction method for a geothermal collection system according to any one of claims 1-6, characterized in that, Drilling equipment is used to drill holes below precast geothermal energy piles. The precast geothermal energy piles are pressed down by a precast pile static press and moved down along the drilling path of the drilling equipment for construction and installation. After reaching the installation depth, the drilling equipment changes the drilling radius to process an enlarged cavity space to accommodate groundwater below the precast geothermal energy pile. Then, the drilling equipment is removed from the precast geothermal energy pile. Finally, water is filled into the heat exchange pipes of the precast geothermal energy pile to release and expand the heat exchange network and fill the enlarged cavity space with water, so that the heat exchange network is distributed in the enlarged cavity space and contacts the circulating water for heat exchange.

8. The method of using a geothermal collection system according to claim 7, characterized in that, After the prefabricated geothermal energy piles are constructed, the heat exchange network absorbs geothermal heat from the circulating water in the enlarged cavity space and conducts it to the prefabricated geothermal energy piles through the heat exchange pipes. At the same time, the circulating water in the enlarged cavity space absorbs geothermal heat synchronously and conducts the geothermal heat to the ground through the heat exchange pipes themselves and the circulating water after heat exchange absorbed by the heat exchange pipes.

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