A shallow ground pipe and medium deep ground heat well series coupling double source ground heat system

Abstract

The utility model relates to a kind of shallow ground heat exchanger and middle-deep geothermal well series coupling's double-source geothermal system, including underground heat exchange unit, ground heat pump unit and user end, and the underground heat exchange unit, ground heat pump unit and user end mutually cooperate to provide two kinds of operating modes of winter heating mode and summer refrigeration mode.The utility model uses the cascade utilization mode of "shallow preheating+deep heating", significantly improves heat pump source side temperature, reduces ground heat exchanger area, prolongs the service life of deep well;In addition, the switching of two modes of heating and refrigeration can be carried out in different seasons, the stratum is reheated by heat pump in summer waste heat, effectively delays stratum attenuation rate.

Description

Technical Field

[0001] This utility model belongs to the field of geothermal energy resource development and utilization technology, specifically relating to a dual-source geothermal system that couples a shallow buried pipe with a medium-deep geothermal well in series. Background Technology

[0002] Geothermal energy is a clean, stable, and sustainable energy source derived from the Earth's crust, characterized by its vast reserves, wide distribution, and ability to provide continuous power over long periods. Geothermal resources originate from the Earth's internal heat and are considered a renewable energy source. Their development and utilization process results in extremely low greenhouse gas emissions, effectively replacing fossil fuels and reducing environmental pollution problems such as smog. Unlike wind and solar energy, which are affected by climate and diurnal cycles, geothermal energy can provide stable power 24 hours a day. Based on its occurrence form and development depth, geothermal energy can be classified into shallow geothermal, medium-deep hydrothermal, and medium-deep dry hot rock types. As a stable, renewable, and green energy source, geothermal energy has received increasing attention, especially in northern regions where the "clean heating" policy has driven the development of shallow buried pipe and medium-deep geothermal energy utilization technologies.

[0003] Single shallow buried pipe systems primarily rely on near-surface isothermal layers for heat exchange, with their core bottleneck being low energy density and limited heat source temperature quality. In cold regions or scenarios with high heating demands, the temperature of shallow rock and soil masses as heat sources is insufficient to meet the initial requirements for efficient heating, resulting in low heat pump evaporation temperatures and limited COP improvement. Furthermore, to meet large-scale loads, shallow systems often require extensive buried pipe laying, leading to large land areas and high initial investment. While single medium-deep coaxial casing closed-loop systems can obtain higher-quality heat energy, their performance is strongly positively correlated with drilling depth, resulting in drilling costs accounting for 50% of the total system investment, making them uneconomical. More seriously, long-term centralized heat extraction continuously depletes the limited heat storage resources around the well, causing thermal decay in the formation's temperature field. The outlet temperature gradually decreases with the years of operation, posing a severe challenge to the system's lifespan and heating stability. For the shallow buried pipe-medium-deep geothermal deep parallel architecture, since the two subsystems are independent in fluid loops and heat management, it is impossible to achieve the preheating and enhancement of the deep inlet working fluid by the shallow system. The outlet temperature is even lower than the extraction temperature of a single well in the medium-deep geothermal system, which restricts the improvement of heat pump COP. At the same time, this superposition has not alleviated the heat decay pressure of the deep system. Instead, the increased system complexity has brought higher control difficulty and operation and maintenance costs.

[0004] Therefore, in order to solve the problems of low energy density and limited heat source temperature quality in the above-mentioned single heat extraction system and low COP of heat pump in parallel system, this utility model innovatively proposes a dual-source geothermal system with "series coupling and cascade utilization", which can switch between heating and cooling modes in different seasons. Utility Model Content

[0005] The purpose of this invention is to address the shortcomings and deficiencies of existing technologies by providing a dual-source geothermal system that couples a shallow buried pipe with a medium-deep geothermal well in series. During winter heating, the circulating medium flows sequentially through a series path of pre-heat extraction in the shallow buried pipe and deep heating in the medium-deep coaxial casing, significantly improving the heat source quality and increasing the COP of the heat pump. During summer cooling, the system switches to cooling mode, and the condensation heat discharged by the heat pump can be transported through an optimized loop to the medium-deep coaxial casing and the shallow buried pipe to supplement the heat storage.

[0006] The technical problem solved by this utility model is achieved through the following technical solution: A dual-source geothermal system consisting of a shallow buried pipe and a medium-deep geothermal well coupled in series includes an underground heat exchange unit, a surface heat pump unit, and a user terminal. The underground heat exchange unit, the surface heat pump unit, and the user terminal cooperate to provide two operating modes: a winter heating mode and a summer cooling mode. The underground heat exchange unit includes a shallow buried pipe heat exchange assembly and a medium-deep coaxial sleeve heat exchange assembly connected in series via a second pipe. The shallow buried pipe heat exchange assembly is composed of shallow buried pipes. The medium-deep coaxial sleeve heat exchange assembly is installed inside the geothermal well and is composed of the geothermal well wall and a vacuum-insulated steel pipe. An annular flow channel is formed between the vacuum-insulated steel pipe and the geothermal well wall, and the interior of the vacuum-insulated steel pipe is a central pipe flow channel. The ground heat pump unit is connected to the medium-deep coaxial sleeve heat exchange assembly and the shallow buried pipe heat exchange assembly via the second pipe and the first pipe, respectively. The ground heat pump unit consists of a heat pump unit, a first circulating pump, a second circulating pump, a heating pump, a cooling pump, and a valve assembly. The valve assembly includes a first throttle valve, a second throttle valve, a third throttle valve, and a fourth throttle valve. The medium-deep coaxial sleeve heat exchange assembly and the heat pump unit are connected sequentially according to the operating mode, with the third throttle valve and the second circulating pump or the first circulating pump and the first throttle valve. The heat pump unit and the user end are connected sequentially according to the operating mode, with the fourth throttle valve, the cooling pump or the heating pump, and the second throttle valve.

[0007] Furthermore, a wellbore one-way valve is installed at the connection between the annular flow channel and the central pipe flow channel, so that fluid can only flow from the annular flow channel into the central pipe flow channel in one direction.

[0008] Furthermore, an inner tube check valve is installed at a designated depth position in the central tube flow channel. The flow direction of the inner tube check valve is from bottom to top to prevent fluid from flowing back downward in the central tube.

[0009] Moreover, the shallow buried pipe is laid vertically or horizontally in the shallow rock and soil mass on the ground surface.

[0010] Moreover, the vacuum-insulated steel pipe consists of two layers of steel pipes, inner and outer, and a high-vacuum insulation layer in between.

[0011] Moreover, the heat pump unit is a reversible ground source heat pump.

[0012] Moreover, the heating pump and cooling pump are frequency converter controlled.

[0013] The advantages and beneficial effects of this utility model are as follows: 1. The shallow and medium-deep geothermal system proposed in this utility model, which is a dual-source geothermal system, innovatively connects the shallow buried pipe and the medium-deep coaxial casing through a hydraulic loop, compared with the traditional single or parallel geothermal system. This constructs a two-way energy cascade utilization mode of "buried pipe preheating and deep well heating" and "deep well heat dissipation and shallow buried pipe cooling", which fundamentally solves the problem of thermal imbalance in the shallow geothermal field and significantly improves the system's life cycle and operational stability.

[0014] 2. The shallow and medium-deep series coupled dual-source geothermal system proposed in this utility model realizes cross-seasonal underground heat management through winter and summer mode switching; during summer cooling, the condensation heat is preferentially discharged to the deep well rock mass to store heat for winter; during winter heating, the source-side temperature of the heat pump is effectively increased by preheating through shallow buried pipes and heating through deep wells compared with complex parallel systems, thereby improving the heat pump COP.

[0015] 3. The shallow and medium-deep geothermal system proposed in this utility model, through its series structure, enables the shallow system to bear part of the basic load, significantly reducing the peak heat extraction demand and long-term heat extraction pressure on the medium-deep geothermal wells. This allows the depth and scale of the medium-deep wells to be optimized to the best economic range, effectively reducing the initial investment of the system and extending the service life of the medium-deep geothermal wells, thus greatly improving the economic feasibility of the project.

[0016] 4. The dual-source geothermal system with shallow and medium-deep geothermal wells coupled in series proposed in this invention significantly reduces the dependence on the heat exchange area of ​​the shallow buried pipes through the series architecture. In traditional single shallow systems, a large area of ​​buried pipes needs to be laid to meet the entire heating and cooling load of a building, resulting in a large footprint. In this invention, since the medium-deep geothermal wells bear the main peak and basic loads, the shallow buried pipes only serve as preheaters, effectively reducing the footprint of the shallow system.

[0017] 5. The shallow and mid-deep series-coupled dual-source geothermal system proposed in this invention solves the reverse heating problem that may exist in traditional systems through the precise layout of one-way valves. When the high-temperature fluid flows downward in the central pipe to a certain depth, the inner pipe one-way valve and the well wall one-way valve are set at critical depths. Their function is to prevent the fluid from continuing to flow downward and guide the fluid into the annular cavity for backflow. This prevents the negative effect of reverse heating by the formation when the fluid temperature drops below the formation temperature at that point during the flow process, thus ensuring that heat is only directionally discharged to the shallower rock layers with lower temperatures.

[0018] 6. The shallow and medium-deep geothermal system coupled in series proposed in this utility model provides both stable heating and efficient cooling for buildings, making it widely applicable. Its innovative architectural concept offers a universal technical solution for integrating the characteristics of geothermal resources at different depths, making it particularly suitable for buildings in cold regions with high heating demands, as well as various buildings that need to simultaneously meet winter and summer heating and cooling loads. This significantly promotes the advancement of geothermal comprehensive utilization technology and expands its application scope. Attached Figure Description

[0019] Figure 1 This is a diagram of a heat pump heating system of the present invention, which connects a shallow buried pipe and a medium-deep geothermal well in series. Figure 2 This is a diagram of a heat pump refrigeration system that connects a shallow buried pipe and a medium-deep geothermal well in series, according to this utility model.

[0020] Explanation of reference numerals in the attached figures 1. Geothermal well wall; 2. Vacuum-insulated steel pipe; 3. Shallow buried pipe; 4. First pipeline; 5. Second pipeline; 6. Heat pump unit; 7. User end; 8. Well wall check valve; 9. Inner pipe check valve; 10. First circulation pump; 11. First throttle valve; 12. Heating pump; 13. Second throttle valve; 14. Second circulation pump; 15. Third throttle valve; 16. Fourth throttle valve; 17. Cooling pump. Detailed Implementation

[0021] The present invention will be further described in detail below through specific embodiments. The following embodiments are only descriptive and not limiting, and should not be used to limit the protection scope of the present invention.

[0022] An innovative dual-source geothermal system that couples a shallow buried pipe with a medium-deep geothermal well in series is characterized by: including an underground heat exchange unit, a surface heat pump unit, and a user terminal 7, wherein the underground heat exchange unit, the surface heat pump unit, and the user terminal 7 cooperate to provide two operating modes: winter heating mode and summer cooling mode. The underground heat exchange unit includes a shallow buried pipe heat exchange assembly and a medium-deep coaxial sleeve heat exchange assembly connected in series via a second pipe 5. The shallow buried pipe heat exchange assembly consists of a shallow buried pipe 3, which is laid vertically or horizontally in the shallow soil and rock mass. The medium-deep coaxial sleeve heat exchange assembly is installed inside the geothermal well and consists of a geothermal well wall 1 and a vacuum-insulated steel pipe 2. The vacuum-insulated steel pipe 2 consists of two layers of steel pipes, inner and outer, and a high-vacuum insulation layer between them. The structure effectively reduces heat loss in the wellbore. An annular flow channel is formed between the vacuum-insulated steel pipe 2 and the geothermal well wall 1, and the interior of the vacuum-insulated steel pipe 2 is a central pipe flow channel. A well wall one-way valve 8 is installed at the connection between the annular flow channel and the central pipe flow channel, so that the fluid can only flow from the annular flow channel into the central pipe flow channel in one direction. An inner pipe one-way valve 9 is installed at a designated depth position in the central pipe flow channel. The flow direction of the inner pipe one-way valve 9 is from bottom to top to prevent the fluid from flowing back downward in the central pipe.

[0023] The ground heat pump unit is connected to the medium-deep coaxial sleeve heat exchange assembly and the shallow buried pipe heat exchange assembly through the second pipe 5 and the first pipe 4, respectively. The ground heat pump unit consists of a heat pump unit 6, a first circulation pump 10, a second circulation pump 14, a heating pump 12, a cooling pump 17, and a valve assembly. The heat pump unit 6 includes an evaporator 6-1 and a condenser 6-2, and the heat pump unit 6 is a reversible ground source heat pump that can switch between cooling and heating modes according to seasonal needs. The heating pump 12 and the cooling pump 17 are frequency converters and can automatically adjust the flow rate according to changes in system load. The valve assembly includes a first throttle valve 11, a second throttle valve 13, a third throttle valve 15, and a fourth throttle valve 16. The third throttle valve 15 and the second circulating pump 14 or the first circulating pump 10 and the first throttle valve 11 are sequentially arranged between the medium-deep coaxial tube heat exchange assembly and the heat pump unit 6 according to the operating mode. The fourth throttle valve 16, the cooling pump 17 or the heating pump 12 and the second throttle valve 13 are sequentially arranged between the heat pump unit 6 and the user end 7 according to the operating mode.

[0024] like Figure 1 The diagram shows a heat pump heating system consisting of a shallow buried pipe and a medium-deep geothermal well connected in series. With the first throttle valve 11 and the second throttle valve 13 open, the heat pump unit 6 operates in heating mode. The low-temperature circulating medium at the outlet of the evaporator 6-1, driven by the first circulating pump 10, flows through the first pipe 4 through the shallow buried pipe 3, exchanges heat with the relatively stable shallow rock and soil, absorbs heat, and achieves a preliminary temperature rise from 5°C to 10°C. The preheated fluid enters the medium-deep coaxial sleeve through the second pipe 5. Under the action of gravity pressure difference and pump driving force, the fluid flows downward along the annular gap between the vacuum insulated steel pipe 2 and the central pipe. During this process, it undergoes deep heat exchange with the deep high-temperature rock layer, and the temperature is significantly increased from 10℃ to 15℃. Subsequently, the high-temperature fluid enters the central pipe through the inner pipe check valve 9 and flows upward, finally exiting through the wellhead of the inner pipe vacuum-insulated steel pipe. It then enters the evaporator 6-1 of the heat pump unit 6, transferring heat to the refrigerant within the heat pump. The refrigerant, after absorbing heat, undergoes compression and circulation, releasing high-temperature heat at the condenser 6-2. The heating pump 12 drives the user-side circulating water to absorb this heat, and regulates the flow rate through the second throttle valve 13 to provide heating to the user end 7.

[0025] like Figure 2 The diagram shows a heat pump cooling system with a shallow buried pipe connected in series with a medium-deep geothermal well. When the third throttle valve 15 and the fourth throttle valve 16 are opened, the heat pump unit 6 operates in cooling mode. The evaporator 6-1 absorbs the heat from the circulating water on the user side to achieve cooling. The cooling pump 17 delivers the cold water to the user end 7. Meanwhile, the condensation heat generated by the refrigeration cycle is carried into the condenser 6-2 by the heat pump working fluid. The 45°C high-temperature circulating medium carrying the condensation heat, driven by the second circulating pump 14, preferentially enters the central pipe of the mid-deep coaxial sleeve. The fluid flows downward, and an inner pipe check valve 9 is installed at a suitable position to prevent it from continuing to flow downward, thus preventing the fluid temperature from being lower than the formation temperature and instead heating the fluid. After passing through the one-way valve 8 on the well wall, the fluid flows upward into the annulus and discharges heat to the shallow rock strata through the outer pipe wall of the geothermal well, thus replenishing the shallow layer of the deep well geothermal reservoir. The fluid, whose temperature drops to 43°C, flows through the second pipe 5 through the shallow buried pipe 3, discharging the remaining heat into the shallow rock and soil. The return liquid temperature reaches 35°C and then returns to the condenser 6-2 through the first pipe 4.

[0026] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A dual-source geothermal system of a shallow ground heat exchanger coupled in series with a medium-deep geothermal well, characterized in that: It includes an underground heat exchange unit, a ground heat pump unit and a user terminal (7), which work together to provide two operating modes: winter heating mode and summer cooling mode. The underground heat exchange unit includes a shallow buried pipe heat exchange assembly and a medium-deep coaxial sleeve heat exchange assembly connected in series through a second pipe (5). The shallow buried pipe heat exchange assembly is composed of a shallow buried pipe (3). The medium-deep coaxial sleeve heat exchange assembly is set inside the geothermal well and is composed of a geothermal well wall (1) and a vacuum-insulated steel pipe (2). An annular flow channel is formed between the vacuum-insulated steel pipe (2) and the geothermal well wall (1). The interior of the vacuum-insulated steel pipe (2) is a central pipe flow channel. The ground heat pump unit is connected to the medium-deep coaxial sleeve heat exchange assembly and the shallow buried pipe heat exchange assembly through the second pipe (5) and the first pipe (4), respectively. The ground heat pump unit consists of a heat pump unit (6), a first circulating pump (10), a second circulating pump (14), a heating pump (12), a cooling pump (17), and a valve assembly. The valve assembly includes a first throttle valve (11), a second throttle valve (13), a third throttle valve (15), and a fourth throttle valve (16). The medium-deep coaxial sleeve heat exchange assembly and the heat pump unit (6) are connected in sequence according to the operating mode, with the third throttle valve (15) and the second circulating pump (14) or the first circulating pump (10) and the first throttle valve (11) being installed in sequence. The heat pump unit (6) and the user end (7) are connected in sequence according to the operating mode, with the fourth throttle valve (16) and the cooling pump (17) or the heating pump (12) and the second throttle valve (13) being installed in sequence.

2. The dual-source geothermal system of claim 1, wherein: A wellbore one-way valve (8) is installed at the connection between the annular flow channel and the central pipe flow channel, so that the fluid can only flow from the annular flow channel into the central pipe flow channel in one direction.

3. The dual-source ground heat system of claim 1, wherein the shallow ground heat exchanger is coupled in series with the medium-deep ground heat exchanger. An inner tube check valve (9) is installed at a specified depth position in the central tube flow channel. The flow direction of the inner tube check valve (9) is from bottom to top to prevent the fluid from flowing back down in the central tube.

4. The dual-source ground heat system of claim 1, wherein the shallow ground heat exchanger is coupled in series with the medium-deep ground heat exchanger. The shallow buried pipe (3) is laid vertically or horizontally in the shallow rock and soil mass on the ground surface.

5. The dual-source ground heat system of claim 1, wherein the shallow ground heat exchanger is coupled in series with the medium-deep ground heat exchanger. The vacuum insulated steel pipe (2) consists of two layers of steel pipes, inner and outer, and a high vacuum insulation layer between them.

6. The dual-source ground heat system of claim 1, wherein the shallow ground heat exchanger is coupled in series with the medium-deep ground heat exchanger. The heat pump unit (6) is a reversible ground source heat pump.

7. The dual-source ground heat system of claim 1, wherein the shallow ground heat exchanger is coupled in series with the medium-deep ground heat exchanger. The heating pump (12) and cooling pump (17) are frequency converter controlled.

Images