Energy pile structure based on shaping phase change material backfilling and operation method thereof

Abstract

The invention provides an energy pile structure based on shaping phase change material backfilling and an operation method of the energy pile structure. The energy pile structure sequentially comprises a pile core heat injection base material A, a heat removal heat shield base material B and a concrete shell from inside to outside. A heat injection pipe is arranged in the pile core heat injection base material A, and a heat removal pipe is arranged in the heat removal heat shield base material B; the heat extraction heat shield base material B is internally connected with the pile core heat injection base material A, and is externally connected with the concrete shell; the pile core heat injection base material A and the heat extraction heat shield base material B are both made of shaped phase change materials; and the heat removal heat shield base material B adopts asymptotic phase change, so that the problems that underground cold and heat loads are unbalanced, a ground temperature field is unbalanced, inter-pile heat interference is serious, underground heat transfer efficiency is low, and the heat and cold supply capacity and energy efficiency of a system are not expected and are reduced year by year when an existing shallow soil source heat pump energy pile supplies heat and cold are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of renewable energy application and building energy electrification, and relates to an energy pile structure based on backfilling of a shaped phase change material and an operation method thereof. Background Art

[0002] Under the background of zero-carbon development, the development trend of building energy electrification is becoming increasingly significant. This is not only one of the key paths to achieve the goal of carbon neutrality, but also an important measure to promote revolutionary changes in energy consumption and comprehensive technological progress. With the improvement of environmental awareness and the implementation of green building standards, the market demand for new energy buildings is growing. Consumers' pursuit of a healthy, energy-saving and sustainable lifestyle has promoted the application of new energy in residential, commercial and industrial buildings.

[0003] In order to achieve the global zero-carbon development goal, the energy transformation of the construction industry is particularly critical, and the electrification of building energy has become an irreversible trend. In this context, shallow soil source heat pump energy pile heating and cooling technology, with its unique advantages and wide application potential, is gradually becoming an important force in promoting the optimization of building energy structure.

[0004] In short, shallow soil source heat pump energy pile technology is an efficient energy system that uses stable low-temperature heat energy in shallow underground soil for heating and cooling. It uses special energy piles (usually also the foundation piles of buildings) as heat exchangers to exchange heat with shallow soil, thereby absorbing heat from the soil in winter to heat the building, and releasing heat in the building into the soil to achieve cooling in summer. This process not only efficiently utilizes the low-grade heat energy that is almost everywhere in nature, but also greatly reduces dependence on traditional fossil energy, providing strong support for achieving zero carbon emissions in buildings.

[0005] After years of research and development and practice, the shallow soil source heat pump energy pile technology has become quite mature, and its stable operating performance and efficient energy conversion efficiency have been widely verified. Whether in the cold northern region or the warm southern region, this technology can stably provide a comfortable indoor environment and meet the heating and cooling needs under different climatic conditions. Compared with traditional geothermal wells, the shallow soil source heat pump energy pile technology does not require a large area of ​​open space to arrange geothermal wells, but cleverly combines energy piles with building foundation piles to achieve efficient land use. Due to the integrated design of energy piles and building foundation piles, the need for separate drilling and installation of geothermal heat exchangers is greatly reduced, thereby significantly reducing drilling costs. Through reasonable system design and layout, this technology can cover a large area of ​​heating and cooling areas, meeting the needs of a variety of scenarios such as large public buildings and residential communities. This large-scale application capability further enhances its important role in building energy transformation.

[0006] However, the current shallow soil source heat pump energy pile heating and cooling system also faces the following problems: 1) It is difficult to balance the underground heat and cold loads, resulting in an imbalance in the geothermal field, and the heating and cooling capacity and energy efficiency of the heat pump system are declining year by year; 2) The thermal interference between the piles is serious, resulting in the energy pile design capacity cannot be fully realized, the underground heat transfer efficiency is low, and the heating and cooling capacity and energy efficiency of the heat pump system do not meet expectations. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides an energy pile structure based on backfill of shaped phase change materials and an operation method thereof, thereby solving the problems existing in the existing shallow soil source heat pump energy piles for heating and cooling, such as unbalanced underground heating and cooling loads, imbalance in geothermal fields, severe thermal interference between piles, low underground heat transfer efficiency, and system heating and cooling capacity and energy efficiency that are lower than expected and decrease year by year.

[0008] The present invention is achieved through the following technical solutions: An energy pile structure based on backfilling of shaped phase change materials, comprising: From inside to outside, it includes pile core heat injection base material A, heat extraction heat shield base material B and concrete shell; The pile core heat injection substrate A is provided with a heat injection pipe, and the heat extraction heat shield substrate B is provided with a heat extraction pipe; The heat extraction heat shield substrate B is internally connected to the pile core heat injection substrate A, and externally connected to the concrete shell; the pile core heat injection substrate A and the heat extraction heat shield substrate B are both fixed phase change materials; wherein the heat extraction heat shield substrate B is asymptotic phase change material.

[0009] Preferably, the inner diameter of the heat extraction heat shield substrate B is 0.6 m, the outer diameter of the heat extraction heat shield substrate B is 1.0 m, and the heat extraction heat shield substrate B is a circular ring structure; the diameter of the pile core heat injection substrate A is 0.6 m.

[0010] Preferably, the heat shield substrate B is a gradual phase change material, specifically: The thermal conductivity of the heat-taking heat shield substrate B decreases linearly from the inside to the outside, and the inner edge of the heat-taking heat shield substrate B is consistent with the thermal conductivity of the pile core heat injection substrate A; the thermal conductivity of the outer edge of the heat-taking heat shield substrate B is one order of magnitude lower than that of the pile core heat injection substrate A and is consistent with the thermal conductivity of the concrete shell.

[0011] Preferably, the thermal conductivity of the pile core heat injection base material A is isotropic.

[0012] Preferably, the heat extraction pipe and the heat injection pipe are both made of PE spiral pipes, the spiral outer diameter of the heat injection pipe is 0.4m, and the spiral outer diameter of the heat extraction pipe is 0.8m.

[0013] Preferably, the phase change temperature range of the pile core heat injection base material A is 18-24°C, and the phase change latent heat is 200 kJ / kg.

[0014] Preferably, the phase change temperature range of the heat extraction heat shield substrate B is 10-16° C., and the phase change latent heat is 200 kJ / kg.

[0015] An operating method of an energy pile structure based on backfilling of a shaped phase change material, comprising: Heat injection stage: After the heat injection begins, the heat injection fluid heats the densified pile core heat injection substrate A from the periphery to transform it into a high energy state. The heat extraction heat shield substrate B absorbs the heat energy in the pile core heat injection substrate A under the action of the temperature difference and transforms into a high energy state. When the heat extraction heat shield substrate B is completely transformed into a high energy state, the heat energy of the heat injection fluid is stored in the pile core heat injection substrate A and the heat extraction heat shield substrate B. Insulation stage: The temperature field is adjusted by spontaneous heat diffusion between the heat shield substrate B and the pile core heat injection substrate A, so that all the heat storage bodies are in a high energy state and the heat diffusion potential difference is reduced to the minimum, forming a temperature distribution pattern of internal heat and external cold; Heat extraction stage: After heat extraction begins, the heat extraction fluid draws heat energy from the heat extraction heat shield substrate B in the middle, causing its temperature to drop and transform into a dense state; when both the heat extraction heat shield substrate B and the pile core heat injection substrate A have completed densification, the heat extraction fluid recovers the heat energy stored in the heat extraction heat shield substrate B and the pile core heat injection substrate A; Recovery stage: By taking advantage of the spontaneous heat diffusion between the heat shield substrate B and the pile core heat injection substrate A to harmonize the temperature field, the heat storage body is completely in a dense state, and the heat diffusion potential difference is reduced to a minimum, forming a temperature distribution pattern of internal heat and external cold.

[0016] Preferably, the operation cycle of the energy pile is 24 hours, which includes a heat injection stage of 7 hours, a heat preservation stage of 4 hours, a heat extraction stage of 9 hours and a recovery stage of 4 hours. After the energy pile has run for 3 cycles, the geothermal field becomes stable, forming a temperature pattern with a single energy pile as the center, hot inside and cold outside, and the wall temperature of the energy pile is close to the temperature of the undisturbed soil.

[0017] Preferably, the ratio of the heat injection intensity in the heat injection stage to the heat extraction intensity in the heat extraction stage is 9:7.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention provides an energy pile structure based on backfilling of a fixed phase change material and an operation method thereof. The structure comprises: from the inside to the outside, a pile core heat injection substrate A, a heat extraction heat shield substrate B and a concrete shell; the pile core heat injection substrate A is the core part of the energy pile, and the pile core heat injection substrate A is made of a fixed phase change material with high thermal conductivity and isotropy. This material can absorb or release a large amount of thermal energy within a specific temperature range to achieve efficient energy storage and conversion. A heat injection pipe is embedded therein, and is used to inject heat into the substrate when necessary, thereby achieving active regulation of underground thermal energy. The heat extraction heat shield substrate B surrounding the pile core heat injection substrate A also uses a fixed phase change material, but its phase change temperature is designed to be slightly lower than that of the pile core material, and the thermal conductivity decreases linearly from the inside to the outside to form an asymptotic thermal barrier. This design helps to eliminate thermal interference between piles and improve the recovery efficiency of thermal energy. The heat extraction pipe is arranged in the heat extraction heat shield substrate B, and is responsible for collecting thermal energy in the surrounding environment and maintaining the balance of the geothermal field. In particular, the heat shield substrate B is made of asymptotic phase change material, that is, the thermal conductivity of the material decreases linearly from the inside to the outside, which further optimizes the heat transfer path and reduces heat dissipation. The outermost layer is a solid concrete shell, which not only provides protection for the entire structure, but also serves as an insulation layer to prevent underground moisture penetration and external environment from interfering with the internal heat exchange process, ensuring long-term stable operation of the system.

[0019] The present invention also provides an operation method of an energy pile structure based on backfilling of a shaped phase change material, comprising: a heat injection fluid heats a pile core heat injection substrate A from the periphery to transform it into a high energy state, and a heat extraction heat shield substrate B absorbs heat energy in the pile core heat injection substrate A under the action of a temperature difference; in a heat preservation stage, all heat storage bodies are in a high energy state, and the heat diffusion potential difference is reduced to a minimum, forming a temperature distribution pattern of internal heat and external cold; a heat extraction fluid draws heat energy from the heat extraction heat shield substrate B from the middle, causing its temperature to drop and transform into a dense state, and the heat extraction fluid recovers the heat energy stored in the heat extraction heat shield substrate B and the pile core heat injection substrate A; in a recovery stage, all heat storage bodies are in a dense state, and the heat diffusion potential difference is reduced to a minimum, forming a temperature distribution pattern of internal heat and external cold. From the principle to the technology, the present invention realizes a method for artificially designing underground cold and heat load balance, solves the problem of imbalance in the geothermal field, and avoids the situation in which the heating and cooling capacity and energy efficiency of the heat pump system decline year by year; it blocks the thermal interference between energy piles, so that the geothermal field is stable on a large scale, forming a temperature pattern with a single energy pile as the center, hot inside and cold outside, and the wall temperature of the energy pile is close to the undisturbed soil temperature, which maintains the soil ecology and ensures the efficiency, robustness and sustainability of the energy pile charging and releasing heat process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments. For ordinary technicians in this field, other inspirations can be obtained based on these drawings without paying creative labor.

[0021] Figure 1 This is a functional structure diagram of an asymptotic phase change energy pile of the present application; Figure 2 It is a schematic diagram of thermal conductivity distribution of asymptotic phase change materials; Figure 3 It is a schematic diagram of the operation method of the asymptotic phase change energy pile; Figure 4 This is the temperature distribution pattern of Example 1 at the end of each stage in the fifth operation cycle; Figure 5 This is the temperature distribution pattern of Comparative Example 2 at the end of each stage in the 5th operation cycle; Figure 6 This is the temperature distribution pattern of Example 3 at the end of each stage in the fifth operation cycle; Figure 7 is the temperature distribution pattern at the end of each stage in the fifth operation cycle of the embodiment; Figure 8 is a photograph of a sample of asymptotic phase change material of an embodiment.

[0022] In the figure, the pile core has a heat injection base material A1, a heat extraction heat shield base material B2, a heat injection pipe 3, a heat extraction pipe 4, and a concrete shell 5. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0024] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0025] Example 1 The energy pile structure based on backfilling of shaped phase change materials includes: The pile core heat injection substrate A1 and the heat extraction heat shield substrate B2 are both shaped phase change materials. Among them, the pile core heat injection substrate A1 is responsible for absorbing, storing and transferring the heat energy of medium-temperature hot water (20°C). The diameter of the shaped material is 0.6m and it is fully filled; the heat extraction heat shield substrate B2 is responsible for storing and releasing the heat energy of low-temperature hot water (<15°C). The inner diameter of the annular area is 0.6m, which is connected to the pile core heat injection substrate A. The outer diameter of the annular area is 1.0m, and the concrete shell 5 is connected to the outside. The heat injection pipe 3 is a PE spiral pipe, which is placed in the pile core heat injection substrate A, and the outer diameter of the spiral is 0.4m; the heat extraction pipe 4 is a PE spiral pipe, which is placed in the heat extraction heat shield substrate B, and the outer diameter of the spiral is 0.8m; the specifications of the heat injection pipe and the heat extraction pipe are both DN20.

[0026] According to the energy pile structure based on backfilling of fixed phase change materials, the phase change temperature range of the pile core heat injection substrate A is 18-24°C, and the phase change latent heat is 200kJ / kg; the phase change temperature range of the heat extraction heat shield substrate B is 10-16°C, and the phase change latent heat is 200kJ / kg. Different from the pile core heat injection substrate A, the heat extraction heat shield substrate B adopts asymptotic phase change design.

[0027] According to the stereotyped phase-change pile core heat injection substrate A and heat extraction heat shield substrate B, the concept of asymptotic phase change is that, among the thermophysical parameters of the pile core heat injection substrate A and the heat extraction heat shield substrate B, except for the phase change temperature range and thermal conductivity, other thermophysical parameters remain consistent; and the thermal conductivity of the heat injection pile core heat injection substrate A is isotropic, and the thermal conductivity of the heat extraction heat shield substrate B decreases linearly from the inside to the outside, and its inner edge thermal conductivity is consistent with the pile core heat injection substrate A, and the outer edge thermal conductivity is one order of magnitude lower than the pile core heat injection substrate A and consistent with the thermal conductivity of the concrete shell. This structure blocks the thermal interference between energy piles and ensures the efficiency, robustness and sustainability of the energy pile charging and discharging process.

[0028] The operation method and requirements of the energy pile structure based on the backfill of the shaped phase change material are to follow Figure 3 The operation method shown in the figure is as follows: the operation cycle of the energy pile is 24 hours. Among them, the operation mode is connected in sequence according to the heat injection stage of 7 hours, the heat preservation stage of 4 hours, the heat extraction stage of 9 hours, and the recovery stage of 4 hours. The ratio of heat injection intensity to heat extraction intensity is 9 to 7. After running for 3 complete cycles, the geothermal field reaches stability on a large scale, forming a temperature pattern with a single energy pile as the center, hot inside and cold outside, and the wall temperature of the energy pile is close to the undisturbed soil temperature, which maintains the soil ecology and ensures the efficiency, robustness and sustainability of the energy pile charging and releasing heat process.

[0029] According to the operation method and requirements of the energy pile structure based on the backfill of the fixed phase change material, the heat injection stage is the first stage of the operation cycle of the energy pile. After the heat injection starts, the heat injection fluid with a higher temperature heats the densified pile core heat injection substrate A from the periphery, causing its temperature to rise and gradually transform to a high energy state; at the same time, the heat extraction heat shield substrate B is in a dense state with a lower temperature, and absorbs the heat energy in the pile core heat injection substrate A with a higher temperature under the action of the temperature difference, and transforms to a high energy state. However, since the thermal conductivity of the pile core heat injection substrate A is isotropic, and the thermal conductivity of the heat extraction heat shield substrate B decreases linearly from the inside to the outside until it is one order of magnitude lower than the thermal conductivity of the pile core heat injection substrate A, the heating process of the heat extraction heat shield substrate B is longer and plays a "heat shield" role, limiting the heat diffusion within the filling range of B. When the heat extraction heat shield substrate B is completely converted into a high energy state, the heat energy of the heat injection fluid is successfully stored in the pile core heat injection substrate A and the heat extraction heat shield substrate B. At this time, there is still a significant temperature gradient between the pile core heat injection substrate A and the heat extraction heat shield substrate B, and the temperature of the material adjacent to the heat injection tube is the highest. In order to ensure the heat transfer efficiency in the heat extraction stage, a heat preservation stage must be set after the heat injection stage to harmonize the temperature field through spontaneous heat diffusion in / between the materials. When the heat preservation stage is over, all the heat storage bodies are in a high energy state, and the heat diffusion potential difference is reduced to a minimum, forming a temperature distribution pattern of internal heat and external cold. The heat extraction stage is the third stage of the energy pile operation cycle. After the heat extraction begins, the heat extraction fluid with a lower temperature draws heat energy from the heat extraction heat shield substrate B in the middle, causing its temperature to drop and transform to a dense state. Since the thermal conductivity of the heat extraction heat shield substrate B decreases linearly from the inside to the outside, the heat flux intensity on the inside and outside of the heat extraction pipe is not equal - the heat flux intensity on the side connected to the pile core heat injection substrate A is high, and the heat flux intensity on the side connected to the concrete shell is low, causing the heat extraction heat shield substrate B to cool down and densify from the outside to the inside, playing the role of a "heat shield" and limiting the heat diffusion to the outer boundary of the heat extraction heat shield substrate B. When the heat extraction heat shield substrate B gradually completes densification, the pile core heat injection substrate A also quickly completes densification - the thermal conductivity of the pile core heat injection substrate A is isotropic and higher than the average value of the heat extraction heat shield substrate B, resulting in heat energy transfer from the beginning of the heat extraction stage. When the pile core heat injection substrate A is completely transformed into a dense state, the heat extraction fluid successfully recovers the heat energy stored in the pile core heat injection substrate A and the heat extraction heat shield substrate B. At this time, there is still a relatively obvious temperature gradient between the pile core heat injection substrate A and the heat extraction heat shield substrate B, and the material temperature adjacent to the heat extraction pipe is the lowest. In order to ensure the heat transfer efficiency in the heat injection stage, a recovery stage must be set after the heat extraction stage to adjust the temperature field through spontaneous heat diffusion inside / between materials. When the recovery stage is over, all the heat storage bodies are in a dense state, and the heat diffusion potential difference is reduced to the minimum, forming a temperature distribution pattern of internal heat and external cold. It can be seen that the essence of the asymptotic phase change is to block the thermal interference between piles and maintain the temperature distribution pattern of internal heat and external cold by designing a reasonable heat injection-heat extraction structure, material thermal physical parameters, and operation strategy.

[0030] Comparative Example 1 The existing energy pile does not have phase change material backfilled, and the operation mode is exactly the same as that of Example 1; See also Figure 4 In the comparative example 1, there are obvious heat and cold accumulation phenomena at the end of heat injection and heat extraction in the 5th cycle; even after the insulation and recovery stages, the geothermal field is still significantly unbalanced; the thermal influence range exceeds the outer boundary of the energy pile, indicating that the thermal interference between the piles has not been resolved; Comparative Example 2 Ordinary phase change energy pile, the operation mode is exactly the same as that of Example 1; See also Figure 5 In the comparative example 2, there are obvious heat and cold accumulation phenomena at the end of heat injection and heat extraction in the 5th cycle; after the insulation and recovery stages, the degree of imbalance of the geothermal field is significantly improved compared with the comparative example 1; the heat influence range still exceeds the outer boundary of the energy pile, indicating that the thermal interference between the piles has not been resolved; Comparative Example 3 Ordinary phase change energy pile, heat is taken from the pile core and heat is injected into the periphery, and the other conditions are the same as those in Example 1; See also Figure 6 In the comparative example 3, there are obvious heat and cold accumulation phenomena at the end of heat injection and heat extraction in the 5th cycle; after the insulation and recovery stages, the consistency of the ground temperature field is further improved compared with the comparative example 2; but the heat influence range is larger than that of the comparative example 2, indicating that the thermal interference between piles is worsened; See also Figure 7 Compared with comparative examples 1, 2, and 3, the heat and cold accumulation of embodiment 1 at the end of heat injection and heat extraction in the 5th cycle is the lightest; after the insulation and recovery stages, the consistency of the geothermal field is the best; the heat impact range is the smallest and is controlled within the outer boundary of the energy pile, properly eliminating the existing obstacles of the shallow soil source heat pump energy pile heating and cooling system; Referring to Table 1, several indicators of heat recovery performance of the energy pile structure based on backfill of shaped phase change material provided in the present application are shown; it indicates that the energy pile structure based on backfill of shaped phase change material provided in the present application strengthens the heat transfer process in the pile and improves the heat recovery efficiency, while blocking thermal interference between piles, improving the uniformity of soil temperature distribution around the energy pile, establishing a benign and sustainable temperature distribution pattern, and improving the energy efficiency of heat pump heating operation.

[0031] Table 1 Several indicators of heat recovery performance of asymptotic phase change energy piles provided in this application

[0032] See also Figure 8 , a sample photo of asymptotic phase change material.

[0033] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or equipment that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment.

[0034] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0035] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

[0036] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. An energy pile structure based on backfilling of shaped phase change materials, characterized in that: include, From inside to outside, it includes pile core heat injection base material A, heat extraction heat shield base material B and concrete shell; The pile core heat injection substrate A is provided with a heat injection pipe, and the heat extraction heat shield substrate B is provided with a heat extraction pipe; The heat extraction heat shield substrate B is internally connected to the pile core heat injection substrate A, and externally connected to the concrete shell; the pile core heat injection substrate A and the heat extraction heat shield substrate B are both fixed phase change materials; wherein the heat extraction heat shield substrate B is asymptotic phase change material.

2. The energy pile structure based on backfilling of shaped phase change materials according to claim 1 is characterized in that: The inner diameter of the heat extraction heat shield substrate B is 0.6 m, the outer diameter of the heat extraction heat shield substrate B is 1.0 m, and the heat extraction heat shield substrate B is a circular ring structure; the diameter of the pile core heat injection substrate A is 0.6 m.

3. The energy pile structure based on backfilling of shaped phase change materials according to claim 1 is characterized in that: The heat shield substrate B is taken as a gradual phase change material, specifically: The thermal conductivity of the heat shield substrate B decreases linearly from the inside to the outside, and the inner edge of the heat shield substrate B is consistent with the thermal conductivity of the pile core heat injection substrate A; The thermal conductivity of the outer edge of the heat shield substrate B is one order of magnitude lower than that of the pile core heat injection substrate A and is consistent with the thermal conductivity of the concrete shell.

4. The energy pile structure based on backfilling of shaped phase change materials according to claim 3 is characterized in that: The thermal conductivity of the pile core heat injection base material A is isotropic.

5. The energy pile structure based on backfilling of shaped phase change materials according to claim 1 is characterized in that: The heat extraction pipe and the heat injection pipe are both made of PE spiral pipes. The spiral outer diameter of the heat injection pipe is 0.4m, and the spiral outer diameter of the heat extraction pipe is 0.8m.

6. The energy pile structure based on backfilling of shaped phase change materials according to claim 1 is characterized in that: The phase change temperature range of the pile core heat injection base material A is 18-24° C., and the phase change latent heat is 200 kJ / kg.

7. The energy pile structure based on backfilling of shaped phase change materials according to claim 1 is characterized in that: The phase change temperature range of the heat extraction heat shield substrate B is 10-16° C., and the phase change latent heat is 200 kJ / kg.

8. An operation method of an energy pile structure based on backfilling of a shaped phase change material, based on the energy pile structure based on backfilling of a shaped phase change material according to any one of claims 1 to 7, characterized in that: include, Heat injection stage: The heat injection fluid heats the densified pile core heat injection substrate A from the periphery to transform it into a high energy state. The heat extraction heat shield substrate B absorbs the heat energy in the pile core heat injection substrate A under the action of the temperature difference and transforms into a high energy state. When the heat extraction heat shield substrate B is completely transformed into a high energy state, the heat energy of the heat injection fluid is stored in the pile core heat injection substrate A and the heat extraction heat shield substrate B. Insulation stage: The temperature field is adjusted by spontaneous heat diffusion between the heat shield substrate B and the pile core heat injection substrate A, so that all the heat storage bodies are in a high energy state and the heat diffusion potential difference is reduced to the minimum, forming a temperature distribution pattern of internal heat and external cold; Heat extraction stage: After heat extraction begins, the heat extraction fluid draws heat energy from the heat extraction heat shield substrate B in the middle, causing its temperature to drop and transform into a dense state; when both the heat extraction heat shield substrate B and the pile core heat injection substrate A have completed densification, the heat extraction fluid recovers the heat energy stored in the heat extraction heat shield substrate B and the pile core heat injection substrate A; Recovery stage: By taking advantage of the spontaneous heat diffusion between the heat shield substrate B and the pile core heat injection substrate A to harmonize the temperature field, the heat storage body is completely in a dense state, and the heat diffusion potential difference is reduced to a minimum, forming a temperature distribution pattern of internal heat and external cold.

9. The method for operating an energy pile structure based on backfilling of a shaped phase change material according to claim 8, characterized in that: The operation cycle of the energy pile is 24 hours, which includes 7 hours of heat injection stage, 4 hours of heat preservation stage, 9 hours of heat extraction stage and 4 hours of recovery stage. After the energy pile has run for 3 cycles, the geothermal field reaches stability, forming a temperature pattern with a single energy pile as the center, hot inside and cold outside, and the wall temperature of the energy pile is close to the temperature of the undisturbed soil.

10. The method for operating an energy pile structure based on backfilling of a shaped phase change material according to claim 8, characterized in that: The ratio of heat injection intensity in the heat injection stage to heat extraction intensity in the heat extraction stage is 9:7.

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