Middle-deep layer geothermal energy gradient utilization system

Abstract

The utility model relates to the technical field of geothermal energy development and utilization, in particular to a mid-deep layer geothermal energy gradient utilization system which comprises a mid-deep layer underground water circulation subsystem, a multi-stage heat exchange subsystem and a user heat supply subsystem. By arranging the multiple stages of heat exchange subsystems, gradient utilization of geothermal energy is achieved, the utilization efficiency of the energy is improved, and different heat requirements of heat users are met; the ground source side water inlet and outlet pipeline comprises a ground source side water outlet pipeline, a ground source side water inlet pipeline and a bypass pipeline, a temperature sensor is arranged on the ground source side water inlet pipeline of the heat pump unit, and a temperature control regulating valve is arranged on the bypass pipeline. Ground source side inlet water and part of ground source side return water are mixed and then enter the heat pump unit, the set inlet water temperature of the heat pump unit is met, and the situation that the inlet water temperature is too high and influences the stability of the system is avoided. Compared with the prior art, the treatment mode is simpler, the use of a plate heat exchanger is reduced, and the cost is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to geothermal energy development and utilization technical field, concretely relates to a middle deep layer geothermal energy gradient utilization system. BACKGROUND

[0002] Compared with renewable energy such as wind energy and solar energy, geothermal resources have the advantages of safety, stability, not being affected by seasons and day-night changes, cleanness, low carbon, and renewability, especially middle deep layer geothermal energy, which has the advantages of wide distribution, large reserves, stability and reliability, and cleanness and environmental protection.

[0003] The middle deep layer geothermal energy needs to be taken from the deep stratum 200-3000 m underground, and currently, the drilling depth of the middle deep layer geothermal energy in China is mainly above 2000 m. The middle deep layer geothermal system has the characteristic of large temperature difference of water supplied and returned on the ground source side. Currently, the temperature difference of water supplied and returned on the ground source side of the middle deep layer geothermal project in China is mostly more than 10 DEG C. The temperature difference of water supplied and returned on the user side under the working condition of comfort air conditioning is generally less than 10 DEG C. The temperature difference on the source side is too large, and it is difficult to realize the large temperature difference working condition only by a single heat pump unit, and the utilization efficiency of geothermal energy is low.

[0004] In addition, because the temperature of the middle deep layer heat source can reach 50 DEG C-60 DEG C, if the high-temperature heat source on the ground source side directly contacts the heat pump unit at the initial stage of the operation of the geothermal system, the heat pump unit is prone to failure, which affects the stability of the system operation. In the existing scheme, the high-temperature heat source on the ground source side is connected to the user side through a plate heat exchanger, and the high-temperature heat source on the ground source side does not enter the heat pump main unit, which reduces the power consumption of the heat pump unit and can avoid the failure of the heat pump unit caused by the excessively high temperature of the heat source on the ground source side. However, in the scheme, the return water temperature is high, which causes waste of heat.

[0005] In summary, there is an urgent need to provide a middle deep layer geothermal energy gradient utilization system to solve the problems in the prior art. UTILITY MODEL CONTENT

[0006] The utility model aims at providing a middle deep layer geothermal energy gradient utilization system, and the specific technical scheme is as follows:

[0007] A middle deep layer geothermal energy gradient utilization system, comprising a middle deep layer underground water circulation subsystem, a multi-stage heat exchange subsystem, and a user heat supply subsystem.

[0008] The middle deep layer underground water circulation subsystem comprises a ground source side heat exchanger, a ground source side water inlet and outlet pipeline, and an underground water circulation water pump. The ground source side heat exchanger is arranged in a geothermal well and communicates with the ground source side water inlet and outlet pipeline. The underground water circulation water pump is arranged on the ground source side water inlet and outlet pipeline. The ground source side water inlet and outlet pipeline communicates with the multi-stage heat exchange subsystem. The multi-stage heat exchange subsystem communicates with the user heat supply subsystem.

[0009] Further, the ground source side water inlet and outlet pipeline comprises a ground source side water outlet pipeline, a ground source side water inlet pipeline and a bypass pipeline, the bypass pipeline is arranged between the ground source side water outlet pipeline and the ground source side water inlet pipeline and communicates with the ground source side water outlet pipeline and the ground source side water inlet pipeline respectively.

[0010] Further, the multi-stage heat exchange subsystem comprises at least two groups of sequentially connected heat pump units and a multi-stage heat exchange subsystem ground source side water inlet and outlet pipeline; the multi-stage heat exchange subsystem ground source side water inlet and outlet pipeline comprises a heat pump unit ground source side water inlet pipeline, a heat pump unit ground source side water outlet pipeline and a heat pump unit ground source side intermediate pipeline, a water inlet end of the heat pump unit ground source side water inlet pipeline is connected with a water outlet end of the ground source side water outlet pipeline and the bypass pipeline, a water outlet end of the heat pump unit ground source side water inlet pipeline is connected with an input end of a first heat pump unit;

[0011] a water inlet end of the heat pump unit ground source side water outlet pipeline is connected with an output end of a last heat pump unit, and a water outlet end of the heat pump unit ground source side water outlet pipeline is connected with a water inlet end of the ground source side water inlet pipeline and the bypass pipeline.

[0012] The heat pump unit ground source side intermediate pipeline communicates two adjacent groups of heat pump units.

[0013] Further, the heat pump unit comprises a condenser and an evaporator, the evaporators of adjacent heat pump units are arranged in series, and the condensers of adjacent heat pump units are arranged in parallel.

[0014] Further, the underground water circulating pump is arranged on the heat pump unit ground source side water inlet pipeline; a temperature sensor is arranged on the heat pump unit ground source side water inlet pipeline, a temperature control regulating valve is arranged on the bypass pipeline, and the temperature sensor is connected with the temperature control regulating valve.

[0015] Further, the multi-stage heat exchange subsystem ground source side water inlet and outlet pipeline further comprises a heat pump unit ground source side water inlet branch pipeline and a heat pump unit ground source side water outlet branch pipeline, the heat pump unit ground source side water inlet branch pipeline is communicated between the heat pump unit ground source side water inlet pipeline and the heat pump unit ground source side intermediate pipeline, and the heat pump unit ground source side water outlet branch pipeline is communicated between the heat pump unit ground source side water outlet pipeline and the heat pump unit ground source side intermediate pipeline.

[0016] Further, valves are arranged on the heat pump unit ground source side water inlet branch pipeline and the heat pump unit ground source side water outlet branch pipeline.

[0017] Further, the user heat supply subsystem comprises a heat user, a heat supply circulating water pipeline and a heat supply circulating water pump, each group of heat pump units is connected with the heat user through the heat supply circulating water pipeline, and the heat supply circulating water pump is arranged on the heat supply circulating water pipeline.

[0018] Further, the heat supply circulating water pipeline comprises a heat supply circulating water inlet pipeline and a heat supply circulating water outlet pipeline, the water inlet end of the heat supply circulating water inlet pipeline is connected with the output end of the condenser, and the water outlet end of the heat supply circulating water inlet pipeline is connected with the water inlet end of the heat user; the water inlet end of the heat supply circulating water outlet pipeline is connected with the water outlet end of the heat user, and the water outlet end of the heat supply circulating water outlet pipeline is connected with the input end of the condenser.

[0019] Further, the ground source side heat exchanger adopts a coaxial double-pipe heat exchanger.

[0020] The technical scheme of the utility model has the following beneficial effects:

[0021] (1)The utility model provides a middle deep layer geothermal energy stepwise utilization system, including middle deep layer underground water circulation subsystem, multistage heat exchange subsystem and user heat supply subsystem, the middle deep layer underground water circulation subsystem includes ground source side heat exchanger, ground source side inlet and outlet water pipeline and underground water circulating pump, the ground source side heat exchanger is located in geothermal well and is communicated with ground source side inlet and outlet water pipeline, the underground water circulating pump is arranged on ground source side inlet and outlet water pipeline, ground source side inlet and outlet water pipeline are communicated with multistage heat exchange subsystem, multistage heat exchange subsystem is communicated with user heat supply subsystem, through the setting multistage heat exchange subsystem, realize the stepwise utilization of geothermal energy, improve the utilization efficiency of energy, satisfy the different heat demand of heat user.

[0022] (2)In the utility model, the ground source side inlet and outlet water pipeline includes ground source side outlet water pipeline, ground source side inlet water pipeline and bypass pipeline, the bypass pipeline is arranged between ground source side outlet water pipeline and ground source side inlet water pipeline and is communicated with ground source side outlet water pipeline and ground source side inlet water pipeline respectively, temperature sensor is arranged on the ground source side inlet water pipeline of heat pump unit, temperature control regulating valve is arranged on the bypass pipeline, through the setting bypass pipeline, cooperate the use of temperature sensor and temperature control regulating valve, make ground source side inlet water mix with part ground source side return water and enter heat pump unit, satisfy the set inlet water temperature of heat pump unit, avoid that inlet water temperature is too high and influence the stability of system, relative to prior art, the processing mode of the utility model is simple, reduces the use of plate heat exchanger and reduces cost.

[0023] (3)In the utility model, when the heat supply load is small or a group of heat pump units is in fault maintenance, the selection of different heat pump units can be realized through the opening and closing of the heat pump unit ground source side inlet water branch pipeline, the heat pump unit ground source side outlet water branch pipeline and the valves S1 and S2.

[0024] In addition to the objects, features and advantages described above, the utility model has other objects, features and advantages. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the present application illustrated in the drawings and their descriptions are used to explain the present application and are not intended to limit the present application. In the drawings:

[0026] Figure 1 is a schematic diagram of the overall structure of the middle-deep geothermal energy cascade utilization system in the embodiment of the present application;

[0027] Figure 2 is a schematic diagram of the state of the middle-deep geothermal energy cascade utilization system in the initial stage of operation in the embodiment of the present application;

[0028] Figure 3 is a schematic diagram of the state of the middle-deep geothermal energy cascade utilization system in the initial stage of operation in the embodiment of the present application; Figure 1

[0029] Figure 4 is a schematic diagram of the state of the middle-deep geothermal energy cascade utilization system in the initial stage of operation in the embodiment of the present application; Figure 2

[0030] Figure 5 is a schematic diagram of the state of the middle-deep geothermal energy cascade utilization system in the initial stage of operation in the embodiment of the present application;

[0031] wherein, 1, ground source side heat exchanger, 2, ground source side water inlet and outlet pipeline, 2.1, ground source side water outlet pipeline, 2.2, ground source side water inlet pipeline, 2.3, bypass pipeline, 3, underground water circulating pump, 4, heat pump unit, 4.1, condenser, 4.2, evaporator, 5, multi-stage heat exchange subsystem ground source side water inlet and outlet pipeline, 5.1, heat pump unit ground source side water inlet pipeline, 5.2, heat pump unit ground source side water outlet pipeline, 5.3, heat pump unit ground source side intermediate pipeline, 5.4, heat pump unit ground source side water inlet branch pipeline, 5.5, heat pump unit ground source side water outlet branch pipeline, 6, temperature sensor, 7, temperature control regulating valve, 8, heat user, 9, heat supply circulating water pipeline, 9.1, heat supply circulating water inlet pipeline, 9.2, heat supply circulating water outlet pipeline, 10, heat supply circulating water pump. DETAILED DESCRIPTION

[0032] The embodiments of the present application are described in detail below with reference to the accompanying drawings, but the present application can be implemented in various different ways as defined and covered.

[0033] ​​In the description of the utility model, it is understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the utility model.

[0034] In addition, the terms "first", "second", and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", and the like can explicitly or implicitly include one or more features. In the description of the utility model, unless otherwise stated, the meaning of "multiple" is two or more.

[0035] Embodiment

[0036] Referring to Figure 1 , the embodiment provides a middle-deep geothermal energy cascade utilization system, which comprises a middle-deep underground water circulation subsystem, a multi-stage heat exchange subsystem and a user heat supply subsystem; the middle-deep underground water circulation subsystem comprises a ground source side heat exchanger 1, a ground source side water inlet and outlet pipeline 2 and an underground water circulation water pump 3, the ground source side heat exchanger 1 is arranged in a geothermal well and communicates with the ground source side water inlet and outlet pipeline 2, the underground water circulation water pump 3 is arranged on the ground source side water inlet and outlet pipeline 2, the ground source side water inlet and outlet pipeline 2 communicates with the multi-stage heat exchange subsystem, and the multi-stage heat exchange subsystem communicates with the user heat supply subsystem.

[0037] In the embodiment, the ground source side water inlet and outlet pipeline 2 comprises a ground source side water outlet pipeline 2.1, a ground source side water inlet pipeline 2.2 and a bypass pipeline 2.3, the water inlet end of the ground source side water outlet pipeline 2.1 and the water outlet end of the ground source side water inlet pipeline 2.2 are connected with the ground source side heat exchanger 1 respectively, and the bypass pipeline 2.3 is arranged between the ground source side water outlet pipeline 2.1 and the ground source side water inlet pipeline 2.2 and communicates with the ground source side water outlet pipeline 2.1 and the ground source side water inlet pipeline 2.2 respectively.

[0038] The multi-stage heat exchange subsystem comprises at least two groups of heat pump units 4 and multi-stage heat exchange subsystem ground source side water inlet and outlet pipelines 5 connected in sequence; preferably, in the embodiment, the heat pump units 4 comprise two groups, namely heat pump unit A and heat pump unit B, and the heat pump unit A and the heat pump unit B each comprise a condenser 4.1 and an evaporator 4.2, the evaporator 4.2 of the heat pump unit A and the evaporator 4.2 of the heat pump unit B are arranged in series, and the condenser 4.1 of the heat pump unit A and the condenser 4.1 of the heat pump unit B are arranged in parallel. The multi-stage heat exchange subsystem is arranged to realize the cascade utilization of the geothermal energy, improve the energy utilization efficiency, and meet different heat utilization requirements of the heat users.

[0039] The multi-stage heat exchange subsystem ground source side water inlet and outlet pipelines 5 comprise a heat pump unit ground source side water inlet pipeline 5.1, a heat pump unit ground source side water outlet pipeline 5.2 and a heat pump unit ground source side intermediate pipeline 5.3, the water inlet end of the heat pump unit ground source side water inlet pipeline 5.1 is connected with the water outlet end of the bypass pipeline 2.3 and the ground source side water outlet pipeline 2.1, and the water outlet end of the heat pump unit ground source side water inlet pipeline 5.1 is connected with the input end of the evaporator 4.2 of the heat pump unit A.

[0040] The water inlet end of the heat pump unit ground source side water outlet pipeline 5.2 is connected with the output end of the evaporator 4.2 of the heat pump unit B, and the water outlet end of the heat pump unit ground source side water outlet pipeline 5.2 is connected with the water inlet end of the bypass pipeline 2.3 and the ground source side water inlet pipeline 2.2; the output end of the evaporator 4.2 of the heat pump unit A and the input end of the evaporator 4.2 of the heat pump unit B are communicated through the heat pump unit ground source side intermediate pipeline 5.3.

[0041] Preferably, referring to Figure 1 , the underground water circulating pump 3 is arranged on the heat pump unit ground source side water inlet pipeline 5.1; a temperature sensor 6 is arranged on the heat pump unit ground source side water inlet pipeline 5.1, a temperature control adjusting valve 7 is arranged on the bypass pipeline 2.3, the temperature sensor 6 is connected with the temperature control adjusting valve 7, the temperature sensor 6 transmits the monitored temperature to the temperature control adjusting valve 7, the temperature control adjusting valve 7 adjusts the valve opening degree, thereby adjusting the water flow of the bypass pipeline 2.3, the water inlet temperature of the heat pump unit A is adjusted, and the influence of the excessively high water inlet temperature on the stability of the system is avoided.

[0042] In the embodiment, the water inlet and outlet pipeline 5 of the multi-stage heat exchange subsystem ground source side further comprises a heat pump unit ground source side water inlet branch pipeline 5.4 and a heat pump unit ground source side water outlet branch pipeline 5.5, the heat pump unit ground source side water inlet branch pipeline 5.4 is communicated between the heat pump unit ground source side water inlet pipeline 5.1 and the heat pump unit ground source side intermediate pipeline 5.3, and the heat pump unit ground source side water outlet branch pipeline 5.5 is communicated between the heat pump unit ground source side water outlet pipeline 5.2 and the heat pump unit ground source side intermediate pipeline 5.3; the heat pump unit ground source side water inlet branch pipeline 5.4 is provided with a valve S1, and the heat pump unit ground source side water outlet branch pipeline 5.5 is provided with a valve S2. When the heating load is small or a group of heat pump units is in fault maintenance, the heat pump unit A and the heat pump unit B can be selected by opening and closing the heat pump unit ground source side water inlet branch pipeline 5.4, the heat pump unit ground source side water outlet branch pipeline 5.5 and the valves S1 and S2.

[0043] In the embodiment, the user heating subsystem comprises a heat user 8, a heating circulating water pipeline 9 and a heating circulating water pump 10, each group of the heat pump unit 4 is connected with the heat user 8 through the heating circulating water pipeline 9, and the heating circulating water pump 10 is arranged on the heating circulating water pipeline 9.

[0044] The heating circulating water pipeline 9 comprises a heating circulating water inlet pipeline 9.1 and a heating circulating water outlet pipeline 9.2, the water inlet end of the heating circulating water inlet pipeline 9.1 is connected with the output end of the condenser 4.1, and the water outlet end of the heating circulating water inlet pipeline 9.1 is connected with the water inlet end of the heat user 8; the water inlet end of the heating circulating water outlet pipeline 9.2 is connected with the water outlet end of the heat user 8, and the water outlet end of the heating circulating water outlet pipeline 9.2 is connected with the input end of the condenser 4.1.

[0045] In the embodiment, each condenser 4.1 is connected with the heat user 8 through the heating circulating water pipeline 9, and a plurality of condensers 4.1 are connected in parallel to meet different heating demands of the heat user. The heating circulating water is heated through the condenser 4.1, flows into the heat user side through the heating circulating water inlet pipeline 9.1, flows back to the condenser 4.1 through the heating circulating water outlet pipeline 9.2, forms a cycle, and the water temperature of the circulating water flowing into the user side and the water temperature of the circulating water flowing out of the user side are set and adjusted according to the actual demand of the heat user.

[0046] In the embodiment, the ground source side heat exchanger 1 is preferably a coaxial sleeve heat exchanger, and other non-water type interference-free buried pipe heat exchangers for extracting underground heat energy can also be used. When the system is shut down, the coaxial sleeve heat exchanger fully stores heat. For example, when the outer tube specification of the coaxial sleeve heat exchanger is Φ177.8*9.19mm, the inner tube specification is Φ110*10mm, and the well depth is 2500m, one coaxial sleeve heat exchanger can store water up to 42m 3, system downtime during storage of a large amount of high temperature heat source, through the rational and effective use, can greatly improve the energy utilization efficiency.

[0047] Preferably, the outer tube of the coaxial jacket heat exchanger adopts steel pipe, and the inner tube adopts PERT pipe or pipe material with better heat preservation and temperature resistance.

[0048] Referring to Figure 2 In the initial stage of system operation, the actual outlet water temperature t1 of the ground source side is higher than the set inlet water temperature of the evaporator 4.2 of the heat pump unit A, and the temperature monitoring signal is transmitted to the temperature control regulating valve 7 through the temperature sensor 6. The temperature control regulating valve 7 adjusts the valve opening to adjust the water flow in the bypass pipeline 2.3, so that the temperature of the mixed water in the ground source side outlet water pipeline 2.1 and the bypass pipeline 2.3 meets the set inlet water temperature of the evaporator 4.2 of the heat pump unit A. On the one hand, it avoids the heat pump unit A from being damaged due to the excessively high inlet water temperature; on the other hand, the bypass pipeline 2.3 provides part of the flow, so that the actual operating flow of the coaxial jacket heat exchanger is lower than the design flow, the flow rate of the ground source side outlet water pipeline 2.1 decreases, and the utilization efficiency of the geothermal energy is improved.

[0049] Referring to Figure 5 When the system runs stably, the outlet water temperature t1 of the ground source side is equal to the set inlet water temperature of the evaporator 4.2 of the heat pump unit A, and the temperature control regulating valve 7 is closed. The outlet water of the coaxial jacket heat exchanger enters the evaporator 4.2 of the heat pump unit A through the ground source side outlet water pipeline 2.1 and the heat pump unit ground source side inlet water pipeline 5.1 to perform the first heat exchange, and the water temperature is reduced to t3. Then the water enters the evaporator 4.2 of the heat pump unit B through the heat pump unit ground source side intermediate pipeline 5.3 to perform the second heat exchange, and the water temperature is reduced to t2. The outlet water of the evaporator 4.2 of the heat pump unit B returns to the coaxial jacket heat exchanger through the heat pump unit ground source side outlet water pipeline 5.2 and the ground source side inlet water pipeline 2.2 to complete the whole cycle, realizing the cascade utilization of the medium-deep geothermal energy and improving the utilization efficiency of the heat source.

[0050] In this embodiment, the structure of the heat pump unit adopts the existing technology. Considering the equipment efficiency, equipment versatility and partial load operating condition equipment matching ability of the existing heat pump unit, t1-t2≤20℃, t1-t3≤10℃, t3-t2≤10℃ are set, i.e. the total temperature difference of the ground source side supply and return water is ≤20℃, and the temperature difference of the heat pump unit evaporator supply and return water is less than 10℃. In addition, in order to improve the utilization efficiency of the medium-deep geothermal energy and avoid the reverse heat transfer of the return water to the soil, the ground source side inlet water temperature t2 is set to be less than 15℃, and the specific set temperature needs to be selected in combination with the soil thermal response test results of the project site.

[0051] Referring to Figure 3 When the heating load is less than or equal to the heating capacity of the heat pump unit A, only the heat pump unit A operates, and the heat pump unit B is stopped. At this time, the valve S1 is closed, the valve S2 is opened, and the input end valve of the heat pump unit B is closed.

[0052] Referring to Figure 4 When the heat pump unit A is in failure or maintenance, only the heat pump unit B is started, the input valve of the heat pump unit A is closed, the valve S1 is opened, and the valve S2 is closed.

[0053] The above only provides preferred embodiments of the present application and is not intended to limit the present application, and for those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A cascade utilization system for medium-deep geothermal energy, characterized in that, It includes a medium-deep groundwater circulation subsystem, a multi-stage heat exchange subsystem, and a user heating subsystem; The medium-deep groundwater circulation subsystem includes a ground source heat exchanger (1), a ground source inlet and outlet water pipeline (2), and a groundwater circulation pump (3). The ground source heat exchanger (1) is located in the geothermal well and is connected to the ground source inlet and outlet water pipeline (2). The groundwater circulation pump (3) is installed on the ground source inlet and outlet water pipeline (2). The ground source inlet and outlet water pipeline (2) is connected to a multi-stage heat exchange subsystem, and the multi-stage heat exchange subsystem is connected to the user heating subsystem.

2. The medium-deep geothermal energy cascade utilization system according to claim 1, characterized in that, The source-side water inlet and outlet pipeline (2) includes a source-side water outlet pipeline (2.1), a source-side water inlet pipeline (2.2), and a bypass pipeline (2.3). The bypass pipeline (2.3) is located between the source-side water outlet pipeline (2.1) and the source-side water inlet pipeline (2.2), and is connected to the source-side water outlet pipeline (2.1) and the source-side water inlet pipeline (2.2) respectively.

3. A medium-deep geothermal energy cascade utilization system according to claim 2, characterized in that, The multi-stage heat exchange subsystem includes at least two sets of sequentially connected heat pump units (4) and ground source side water inlet and outlet pipelines (5) of the multi-stage heat exchange subsystem; The ground source side inlet and outlet water pipes (5) of the multi-stage heat exchange subsystem include a ground source side inlet water pipe (5.1), a ground source side outlet water pipe (5.2), and a ground source side intermediate pipe (5.3). The inlet end of the ground source side inlet water pipe (5.1) is connected to the outlet end of the ground source side outlet water pipe (2.1) and the bypass pipe (2.3). The outlet end of the ground source side inlet water pipe (5.1) is connected to the input end of the first heat pump unit (4). The inlet end of the ground source side outlet water pipe (5.2) of the heat pump unit is connected to the output end of the terminal heat pump unit (4), and the outlet end of the ground source side outlet water pipe (5.2) of the heat pump unit is connected to the inlet end of the ground source side inlet water pipe (2.2) and the bypass pipe (2.3); The intermediate pipeline (5.3) on the ground source side of the heat pump unit connects to two adjacent heat pump units (4).

4. A medium-deep geothermal energy cascade utilization system according to claim 3, characterized in that, The heat pump unit (4) includes a condenser (4.1) and an evaporator (4.2). The evaporators (4.2) between adjacent heat pump units (4) are connected in series, and the condensers (4.1) between adjacent heat pump units (4) are connected in parallel.

5. A medium-deep geothermal energy cascade utilization system according to claim 3, characterized in that, The groundwater circulating pump (3) is installed on the ground source side inlet pipe (5.1) of the heat pump unit; A temperature sensor (6) is installed on the ground source side water inlet pipe (5.1) of the heat pump unit, and a temperature control valve (7) is installed on the bypass pipe (2.3). The temperature sensor (6) is connected to the temperature control valve (7).

6. A medium-deep geothermal energy cascade utilization system according to claim 3, characterized in that, The ground source side inlet and outlet water pipes (5) of the multi-stage heat exchange subsystem also include a ground source side inlet branch pipe (5.4) and a ground source side outlet branch pipe (5.5) of the heat pump unit. The ground source side inlet branch pipe (5.4) of the heat pump unit is connected between the ground source side inlet pipe (5.1) of the heat pump unit and the intermediate ground source side pipe (5.3) of the heat pump unit. The ground source side outlet branch pipe (5.5) of the heat pump unit is connected between the ground source side outlet pipe (5.2) of the heat pump unit and the intermediate ground source side pipe (5.3) of the heat pump unit.

7. A medium-deep geothermal energy cascade utilization system according to claim 6, characterized in that, Valves are installed on both the ground source side inlet branch pipe (5.4) and the ground source side outlet branch pipe (5.5) of the heat pump unit.

8. A medium-deep geothermal energy cascade utilization system according to claim 4, characterized in that, The user heating subsystem includes heat users (8), heating circulating water pipes (9) and heating circulating water pumps (10). Each heat pump unit (4) is connected to the heat users (8) through the heating circulating water pipes (9), and the heating circulating water pumps (10) are installed on the heating circulating water pipes (9).

9. A medium-deep geothermal energy cascade utilization system according to claim 8, characterized in that, The heating circulating water pipeline (9) includes a heating circulating water inlet pipeline (9.1) and a heating circulating water outlet pipeline (9.2). The inlet end of the heating circulating water inlet pipeline (9.1) is connected to the outlet end of the condenser (4.1), and the outlet end of the heating circulating water inlet pipeline (9.1) is connected to the inlet end of the heat user (8). The inlet end of the heating circulating water outlet pipeline (9.2) is connected to the outlet end of the heat user (8), and the outlet end of the heating circulating water outlet pipeline (9.2) is connected to the input end of the condenser (4.1).

10. A medium-deep geothermal energy cascade utilization system according to any one of claims 1-9, characterized in that, The ground source heat exchanger (1) adopts a coaxial tube heat exchanger.

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