Supercritical carbon dioxide cycle and deep geothermal reservoir coupled comprehensive energy system and operation method

Abstract

This invention discloses an integrated energy system and its operation method that couples a supercritical carbon dioxide cycle with a deep geothermal reservoir. The system includes a supercritical carbon dioxide cycle system, a deep geothermal system, and a heating system. Coupling and regulation of the working fluid between the surface circulation system and the deep geothermal reservoir are achieved through the installation of regulating valves. When the grid load is stable, the system operates in supercritical carbon dioxide recompression cycle mode for power generation. During load reduction, a portion of the working fluid is injected into the deep geothermal reservoir for underground storage and to reduce the cycle load. During load increase, the stored working fluid is recovered for power generation and replenished to the circulation system, thus achieving rapid load increase. When the surface circulation system is shut down or under low load, the system switches to independent geothermal power generation mode. Simultaneously, waste heat can be recovered through a precooler to provide heating to users under all operating conditions, and coordinated optimization of power generation and heating is achieved through turbine bypass regulation. This invention utilizes the dual functions of deep geothermal reservoirs—working fluid storage and heat exchange—to improve the system's peak-shaving capacity, operational flexibility, and overall energy utilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of energy power and integrated energy utilization technology, specifically to an integrated energy system and operation method that couples supercritical carbon dioxide cycle with deep geothermal reservoir. Background Technology

[0002] In recent years, with the continuous increase in the installed capacity of new energy sources such as wind power and photovoltaics, the fluctuation of power grid load has become increasingly severe, placing higher demands on the flexible adjustment capability and comprehensive energy utilization efficiency of power generation systems. Supercritical carbon dioxide cycle has advantages such as high cycle efficiency, compact equipment, and applicability to medium and high temperature heat sources, and has broad application prospects in geothermal power generation, solar thermal power generation, and industrial waste heat utilization.

[0003] Existing supercritical carbon dioxide cycles typically employ turbine throttling, bypass regulation, or volumetric mass regulation to achieve load control during partial load operation. While volumetric mass regulation can maintain relatively high system efficiency to some extent, it suffers from slow response speed and poor operational flexibility. Furthermore, it usually requires large-scale ground-based high-pressure gas storage devices to store and replenish the circulating working fluid, leading to high equipment investment, large footprint, and insufficient safety.

[0004] Deep geothermal reservoirs not only provide stable geothermal resources, but also have large underground storage space, providing a new way to regulate and utilize circulating working fluids. However, the comprehensive utilization rate of geothermal resources is currently low. Summary of the Invention

[0005] In view of the problems in the existing technology, such as insufficient peak-shaving capacity of supercritical carbon dioxide cycle, reliance on large-scale ground high-pressure gas storage devices for regulating the quality of the circulating working fluid, poor system operation flexibility, and low comprehensive utilization rate of geothermal resources, the purpose of this invention is to provide an integrated energy system and operation method that couples supercritical carbon dioxide cycle with deep geothermal reservoir.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A comprehensive energy system coupling a supercritical carbon dioxide cycle with a deep geothermal reservoir includes a supercritical carbon dioxide cycle system, a deep geothermal system, and a heating system. The three are coupled and connected through a supercritical carbon dioxide working fluid to form a comprehensive energy utilization system integrating power generation, energy storage, and heating.

[0007] The supercritical carbon dioxide circulation system includes a precooler 1, a main compressor 2, a first regulating valve 3, a low-temperature regenerator 4, a high-temperature regenerator 5, a main heat exchanger 6, a first turbine 7, a recompressor 8, and a first generator 9. These components are connected via pipelines to form a recompressed supercritical carbon dioxide Brayton cycle. After being compressed by the main compressor 2, the supercritical carbon dioxide working fluid is regulated by the first regulating valve 3 and sequentially enters the cold side of the low-temperature regenerator 4 and the cold side of the high-temperature regenerator 5 for reheating. It then enters the main heat exchanger 6 to absorb heat before entering the first turbine 7 to expand and perform work, driving the first generator 9 to generate electricity. The supercritical carbon dioxide working fluid discharged from the first turbine 7 flows sequentially through the hot side of the high-temperature regenerator 5 and the hot side of the low-temperature regenerator 4, releasing heat before splitting into two paths. One path enters the recompressor 8 for compression and returns to the cold side of the high-temperature regenerator 5; the other path enters the hot side of the precooler 1 to exchange heat with circulating water and cool down before entering the main compressor 2, completing the cycle.

[0008] The deep geothermal system includes a second regulating valve 10, an injection well 11, a deep geothermal reservoir 12, a production well 13, a third regulating valve 14, a second turbine 15, a second generator 16, and a turbine bypass valve 17. The outlet of the main compressor 2 is connected to the injection well 11 via the second regulating valve 10. Supercritical carbon dioxide is injected into the deep geothermal reservoir 12, absorbs geothermal energy underground, and is extracted by the production well 13. It then enters the second turbine 15 via the third regulating valve 14, expands to drive the second generator 16, and generates electricity. Afterward, it enters the hot side of the precooler 1 and returns to the main compressor 2, forming a geothermal cycle. The turbine bypass valve 17 is connected in parallel at both ends of the second turbine 15 to regulate the flow rate of the working fluid entering the second turbine 15, achieving coordinated control of geothermal power generation and heating capacity.

[0009] The heating system includes a circulating water pump 18, a precooler 1, and users 19. The circulating water pump 18 delivers circulating water to the cold side of the precooler 1, where it exchanges heat with high-temperature supercritical carbon dioxide from the outlet of the second turbine 15 and the hot side outlet of the low-temperature regenerator 4. After absorbing heat, the circulating water is delivered to users 19 to provide heating. The supercritical carbon dioxide after heat exchange is further cooled before entering the main compressor 2 to complete the subsequent cycle.

[0010] The supercritical carbon dioxide circulation system shares the main compressor 2 and precooler 1 with the deep geothermal system. The coupling control between the supercritical carbon dioxide circulation system and the deep geothermal system is achieved by adjusting the opening degrees of the first regulating valve 3, the second regulating valve 10, the third regulating valve 14, and the turbine bypass valve 17. It can operate under the following conditions: (1) Baseline power generation conditions When the grid load remains constant, the system operates primarily through a supercritical carbon dioxide recompression regenerative cycle, with the geothermal system serving only as a coupling channel and not participating in working fluid storage or energy release, thus achieving stable power generation.

[0011] (2) Reduced load condition When the grid load decreases, some supercritical carbon dioxide is injected into the deep geothermal reservoir 12 through the surface circulation system to achieve underground storage of the working medium. The remaining working medium maintains surface circulation for power generation, thereby reducing the circulation mass flow rate and realizing the system's load reduction operation and working medium regulation.

[0012] (3) Increased load condition When the grid load increases, the high-temperature and high-pressure supercritical carbon dioxide stored in the deep geothermal reservoir 12 is extracted, expanded by the second turbine 15 to generate electricity, and replenished to the supercritical carbon dioxide circulation system, thereby increasing the mass flow rate of the circulating working fluid and the system output power, and realizing the system's rapid load increase and peak-shaving operation.

[0013] (4) Geothermal independent power generation operation When the supercritical carbon dioxide ground circulation system is shut down or running at low load, the system switches to geothermal independent circulation mode, shuts down the supercritical carbon dioxide circulation system, and retains only the main compressor 2, precooler 1 and deep geothermal system to form an independent geothermal circulation, so as to realize the independent utilization of geothermal resources.

[0014] (5) Waste heat supply function Under all the above operating conditions, the working fluid at the hot side outlet of the low-temperature regenerator and the waste heat from the turbine exhaust can be recovered through the precooler 1 to provide heating to user 19.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) Using deep geothermal reservoirs to replace traditional ground high-pressure gas storage devices to achieve large-capacity underground storage of supercritical carbon dioxide working fluid, and combining working fluid storage and geothermal heat exchange functions, thereby reducing equipment investment, land area and high-pressure storage risks.

[0016] (2) Utilizing deep geothermal reservoirs to achieve circulating working fluid energy storage and quality regulation, and cooperating with geothermal power generation, can quickly respond to load changes and improve the system's peak-shaving capacity and operational flexibility.

[0017] (3) Combine the recovery of supercritical carbon dioxide cycle waste heat and geothermal turbine exhaust waste heat for heating, realize the cascade utilization of low-grade waste heat, and improve the overall energy utilization efficiency of the system.

[0018] (4) The storage and release are completed directly by using supercritical carbon dioxide circulating working fluid, avoiding multiple energy conversions in traditional energy storage methods, reducing energy storage losses and improving system energy utilization efficiency.

[0019] (5) When the supercritical carbon dioxide cycle system is shut down or running at low load, the system can switch to geothermal independent power generation mode to ensure continuous and stable operation, reduce low load efficiency loss, and improve operational flexibility, reliability and geothermal resource utilization efficiency.

[0020] (6) The system can flexibly switch between modes such as energy storage, peak shaving power generation, combined heat and power and geothermal independent power generation according to the grid load and heating demand, so as to realize the comprehensive and efficient utilization of power generation, heating and geothermal resources. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the integrated energy system structure of the present invention, which couples a supercritical carbon dioxide cycle with a deep geothermal reservoir.

[0022] Wherein: 1 is the precooler; 2 is the main compressor; 3 is the first regulating valve; 4 is the low-temperature regenerator; 5 is the high-temperature regenerator; 6 is the main heat exchanger; 7 is the first turbine; 8 is the re-compressor; 9 is the first generator; 10 is the second regulating valve; 11 is the injection well; 12 is the deep geothermal reservoir; 13 is the production well; 14 is the third regulating valve; 15 is the second turbine; 16 is the second generator; 17 is the turbine bypass valve; 18 is the circulating water pump; 19 is the user. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following embodiments.

[0024] like Figure 1 As shown, this embodiment provides an integrated energy system coupling a supercritical carbon dioxide cycle with a deep geothermal reservoir, including a supercritical carbon dioxide cycle system, a deep geothermal system, and a heating system.

[0025] The supercritical carbon dioxide cycle system includes a precooler 1, a main compressor 2, a first regulating valve 3, a low-temperature regenerator 4, a high-temperature regenerator 5, a main heat exchanger 6, a first turbine 7, a re-compressor 8, and a first generator 9.

[0026] The hot-side outlet of the precooler 1 is connected to the inlet of the main compressor 2. The outlet of the main compressor 2 is connected to the first regulating valve 3 and the second regulating valve 10 respectively. The outlet of the first regulating valve 3 is connected to the cold-side inlet of the low-temperature regenerator 4. The cold-side outlet of the low-temperature regenerator 4 is connected to the cold-side inlet of the high-temperature regenerator 5. The cold-side outlet of the high-temperature regenerator 5 is connected to the cold-side inlet of the main heat exchanger 6. The cold-side outlet of the main heat exchanger 6 is connected to the inlet of the first turbine 7. The first turbine 7 drives the first generator 9 to generate electricity through a rotating shaft. The outlet of the first turbine 7 is connected in sequence to the hot-side inlet of the high-temperature regenerator 5 and the hot-side inlet of the low-temperature regenerator 4. The hot-side outlet of the low-temperature regenerator 4 is connected to the hot-side inlet of the precooler 1 and the inlet of the recompressor 8 respectively. The outlet of the recompressor 8 is connected to the cold-side inlet of the high-temperature regenerator 5, thereby forming a recompression supercritical carbon dioxide Brayton cycle.

[0027] The deep geothermal system includes a second regulating valve 10, an injection well 11, a deep geothermal reservoir 12, a production well 13, a third regulating valve 14, a second turbine 15, a second generator 16, and a turbine bypass valve 17.

[0028] The outlet of the second regulating valve 10 is connected to the injection well 11, which is connected to the deep geothermal reservoir 12. The deep geothermal reservoir 12 is connected to the production well 13. The outlet of the production well 13 is connected to the inlet of the second turbine 15 via the third regulating valve 14. The second turbine 15 drives the second generator 16 to generate electricity through a rotating shaft. The turbine bypass valve 17 is connected in parallel between the inlet and outlet of the second turbine 15 to regulate the flow rate of the working fluid entering the second turbine 15. The outlet of the second turbine 15 is connected to the hot side inlet of the precooler 1, and the hot side outlet of the precooler 1 is connected to the inlet of the main compressor 2, thereby forming a supercritical carbon dioxide geothermal cycle.

[0029] The heating system includes a circulating water pump 18, a precooler 1, and users 19. The outlet of the circulating water pump 18 is connected to the cold-side inlet of the precooler 1, and the cold-side outlet of the precooler 1 is connected to the users 19. Circulating water enters the precooler 1 under the action of the circulating water pump 18, exchanges heat with supercritical carbon dioxide from the outlet of the second turbine 15 and the hot-side outlet of the low-temperature regenerator 4, absorbs residual heat, and is then delivered to the users 19 to provide heating. The supercritical carbon dioxide after heat exchange is further cooled and returned to the main compressor 2 to continue participating in the system circulation.

[0030] In this embodiment, the supercritical carbon dioxide circulation system and the deep geothermal system share the main compressor 2 and the precooler 1. By adjusting the opening of the first regulating valve 3, the second regulating valve 10, the third regulating valve 14, and the turbine bypass valve 17, the flow distribution of the supercritical carbon dioxide working fluid between the surface circulation system and the deep geothermal system can be realized, enabling the system to switch between different operating modes according to operational needs.

[0031] When the grid load is stable, the first regulating valve 3 opens, while the second regulating valve 10 and the third regulating valve 14 close. Supercritical carbon dioxide, after being pressurized by the main compressor 2, enters the low-temperature regenerator 4 and the high-temperature regenerator 5 for preheating, then enters the main heat exchanger 6 to absorb heat from external heat sources. Subsequently, it enters the first turbine 7 to expand and drive the first generator 9 to generate electricity. The turbine exhaust flows sequentially through the high-temperature regenerator 5 and the low-temperature regenerator 4. A portion then enters the re-compressor 8, and a portion enters the precooler 1 for waste heat recovery, before finally returning to the main compressor 2 to complete the supercritical carbon dioxide re-compression cycle.

[0032] When the grid load decreases, the first regulating valve 3 and the second regulating valve 10 are opened, the third regulating valve 14 is closed, and the openings of the first regulating valve 3 and the second regulating valve 10 are adjusted. This allows some of the supercritical carbon dioxide, pressurized by the main compressor 2, to enter the injection well 11 through the second regulating valve 10 and be injected into the deep geothermal reservoir 12 for storage. The remaining supercritical carbon dioxide continues to enter the low-temperature regenerator 4 and the high-temperature regenerator 5 to participate in the surface circulation, thereby reducing the circulation mass flow rate and achieving system load reduction operation. Utilizing the large-capacity storage characteristics of the deep geothermal reservoir, it can replace traditional surface energy storage devices to realize the underground utilization of the circulating working fluid.

[0033] When the grid load increases, the first regulating valve 3 and the third regulating valve 14 are opened, the second regulating valve 10 is closed, and the opening degree of the first regulating valve 3 and the third regulating valve 14 is adjusted. High-temperature, high-pressure supercritical carbon dioxide stored in the deep geothermal reservoir 12 is extracted through the production well 13 to the surface system and enters the second turbine 15 to expand and perform work, driving the second generator 16 to generate electricity, thereby increasing the power output capacity. The supercritical carbon dioxide discharged from the second turbine 15 enters the precooler 1 to release waste heat and then returns to the main compressor 2, where it recirculates and merges with the surface supercritical carbon dioxide, thereby increasing the mass flow rate of the circulating working fluid, improving the supercritical carbon dioxide circulation output power, and thus enhancing the overall power generation capacity of the system, achieving flexible grid regulation and peak-shaving operation.

[0034] By switching operating conditions as described above, a two-way coupled regulation of supercritical carbon dioxide cycle and deep geothermal reservoir is achieved. This enables the system to achieve underground working fluid storage and load reduction operation under low load conditions, and to achieve working fluid recovery and power output enhancement under high load conditions, thereby constructing a dynamic working fluid regulation and peak-shaving power generation system based on underground reservoirs. Compared with traditional working fluid mass regulation methods based on volumetric storage tanks, this invention avoids the problems of large tank volume, slow regulation response speed, and insufficient system flexibility.

[0035] When the ground-based supercritical carbon dioxide cycle system is shut down, under maintenance, or under low load, the system can switch to geothermal independent power generation mode, using the deep geothermal system to generate electricity independently, ensuring continuous and stable operation of the system, reducing efficiency losses caused by low-load operation of the supercritical carbon dioxide cycle, and improving the system's operational flexibility, reliability, and geothermal resource utilization efficiency.

[0036] Under independent geothermal power generation conditions, the first regulating valve 3 is closed, and the second regulating valve 10 and the third regulating valve 14 are opened, shutting down the supercritical carbon dioxide surface circulation loop. Only the main compressor 2, precooler 1, and deep geothermal system remain operational. Supercritical carbon dioxide, pressurized by the main compressor 2, is injected into the deep geothermal reservoir 12 through the injection well 11 via the second regulating valve 10. After absorbing geothermal energy underground, it is extracted to the surface through the production well 13 and the third regulating valve 14, enters the second turbine 15 to expand and drive the second generator 16 to generate electricity, and then returns to the main compressor 2 after being cooled by the precooler 1, forming an independent geothermal power generation cycle.

[0037] Under heating conditions, the system can operate in either supercritical carbon dioxide cycle power generation mode or geothermal power generation mode. The precooler 1 serves as the system's heating heat exchange device, through which circulating water continuously flows and exchanges heat with supercritical carbon dioxide. The supercritical carbon dioxide from the hot side outlet of the low-temperature regenerator 4 and the supercritical carbon dioxide discharged from the second turbine 15 both release waste heat in the precooler 1, heating the circulating water. The heated circulating water is then delivered to user 19 for heating.

[0038] When heating demand increases, the system simultaneously activates both the supercritical carbon dioxide cycle power generation mode and the geothermal power generation mode. The first regulating valve 3, the second regulating valve 10, and the third regulating valve 14 are opened, and the opening of the turbine bypass valve 17 is adjusted. This allows some of the high-temperature, high-pressure supercritical carbon dioxide from the deep geothermal reservoir 12 to bypass the second turbine 15 and directly enter the precooler 1 to exchange heat with the circulating water. This reduces the work done by the second turbine 15, increases the system's heating capacity, and meets user heating demands. This process achieves the synergistic utilization of supercritical carbon dioxide cycle waste heat and geothermal waste heat, as well as flexible adjustment of heating capacity, improving the system's overall energy utilization efficiency.

[0039] This embodiment utilizes the dual functions of deep geothermal reservoirs as both supercritical carbon dioxide storage medium and geothermal heat exchange medium, achieving the organic coupling of supercritical carbon dioxide cycle power generation, underground energy storage, peak-shaving power generation, and waste heat supply, thereby improving the system's operational flexibility, peak-shaving capacity, and comprehensive utilization efficiency of geothermal resources.

Claims

1. A comprehensive energy system coupling supercritical carbon dioxide cycle with deep geothermal reservoirs, characterized in that, include: The supercritical carbon dioxide circulation system, the deep geothermal system, and the heating system are all connected by supercritical carbon dioxide as the working fluid. The supercritical carbon dioxide cycle system includes a precooler (1), a main compressor (2), a first regulating valve (3), a low-temperature regenerator (4), a high-temperature regenerator (5), a main heat exchanger (6), a first turbine (7), and a first generator (9) connected in sequence, as well as a recompressor (8) disposed between the precooler (1) and the high-temperature regenerator (5). The deep geothermal system includes a second regulating valve (10), an injection well (11), a deep geothermal reservoir (12), a production well (13), a third regulating valve (14), a second turbine (15), a second generator (16), and a turbine bypass valve (17) connected in sequence. The injection well (11) and the production well (13) are connected through the deep geothermal reservoir (12). The heating system includes a circulating water pump (18), a precooler (1), and a user (19) connected in sequence. The precooler (1) and the main compressor (2) serve as shared equipment for the supercritical carbon dioxide circulation system and the deep geothermal system. The working fluid flow direction is regulated by the first regulating valve (3), the second regulating valve (10), the third regulating valve (14) and the turbine bypass valve (17), so that the supercritical carbon dioxide can be stored, released and switched between the ground circulation system and the deep geothermal reservoir (12), thereby forming a comprehensive energy system integrating power generation, energy storage and heating.

2. The system according to claim 1, characterized in that: The supercritical carbon dioxide circulation system is a closed recompression Brayton cycle, wherein the hot side outlet of the precooler (1) is connected to the inlet of the main compressor (2); the supercritical carbon dioxide at the outlet of the main compressor (2) is divided into two paths, one path enters the cold side of the low-temperature regenerator (4) and the high-temperature regenerator (5) through the first regulating valve (3), and the other path enters the deep geothermal system; after heat exchange in the low-temperature regenerator (4) and the high-temperature regenerator (5), the supercritical carbon dioxide enters the main heat exchanger (6) to absorb heat and then enters the first turbine (7) to expand and do work; the supercritical carbon dioxide at the outlet of the first turbine (7) passes through the hot side of the high-temperature regenerator (5) and the low-temperature regenerator (4) in sequence for waste heat recovery and then is diverted, part of which enters the hot side of the precooler (1) for cooling and then returns to the main compressor (2), and the other part enters the recompressor (8) for pressurization and then is sent back to the cold side inlet of the high-temperature regenerator (5).

3. The system according to claim 1, characterized in that: In the deep geothermal system, supercritical carbon dioxide regulated by the second regulating valve (10) enters the deep geothermal reservoir (12) through the injection well (11), absorbs geothermal energy through heat exchange in the deep geothermal reservoir (12), and is then extracted by the production well (13). The extracted supercritical carbon dioxide enters the second turbine (15) through the third regulating valve (14), expands and does work in the second turbine (15), and drives the second generator (16) to generate electricity. The supercritical carbon dioxide at the outlet of the second turbine (15) flows back to the hot side of the precooler (1) for cooling and then returns to the main compressor (2), forming a closed geothermal power generation cycle system.

4. The system according to claim 1, characterized in that: In the heating system, the circulating water pump (18) delivers circulating water to the cold side of the precooler (1) and exchanges heat with the high-temperature supercritical carbon dioxide from the outlet of the second turbine (15) and the hot side outlet of the low-temperature regenerator (4). After absorbing heat, the circulating water provides heat energy to the user (19). The supercritical carbon dioxide after heat exchange is further cooled and then enters the main compressor (2).

5. The system according to claim 1, characterized in that: The turbine bypass valve (17) is connected in parallel between the inlet and outlet of the second turbine (15) to regulate the flow rate of the working fluid entering the second turbine (15) so as to achieve coordinated control of power generation and heating demand.

6. A method for operating the system according to any one of claims 1 to 5, characterized in that: Control commands are generated based on the grid load status, and the first regulating valve (3), the second regulating valve (10), the third regulating valve (14) and the turbine bypass valve (17) are controlled in a coordinated manner based on the control commands, so that the system switches between benchmark power generation, load reduction, load increase, geothermal independent power generation and heating regulation operation.

7. The method according to claim 6, characterized in that: When the grid load is stable, the first regulating valve (3) is opened and the second regulating valve (10) and the third regulating valve (14) are closed, so that the supercritical carbon dioxide can complete the power generation operation in the recompression Brayton cycle. When the grid load decreases, the first regulating valve (3) and the second regulating valve (10) are opened, the third regulating valve (14) is closed, and the opening of the first regulating valve (3) and the second regulating valve (10) is adjusted so that some of the supercritical carbon dioxide after being pressurized by the main compressor (2) enters the injection well (11) through the second regulating valve (10) and is injected into the deep geothermal reservoir (12) for storage. The remaining supercritical carbon dioxide working fluid maintains the ground circulation power generation, thereby reducing the mass flow rate of the circulating working fluid and realizing the system load reduction operation and working fluid regulation. When the grid load increases, the first regulating valve (3) and the third regulating valve (14) are opened, the second regulating valve (10) is closed, and the opening of the first regulating valve (3) and the third regulating valve (14) is adjusted so that the high temperature and high pressure supercritical carbon dioxide stored in the deep geothermal reservoir (12) is extracted through the production well (13) and enters the second turbine (15) through the third regulating valve (14) to expand and do work to drive the second generator (16) to generate electricity; the working fluid at the outlet of the second turbine (15) is supplemented to the supercritical carbon dioxide circulation system, thereby increasing the mass flow rate and output power of the circulating working fluid, and realizing the rapid load increase and peak operation of the system.

8. The method according to claim 6, characterized in that: When the supercritical carbon dioxide circulation system is shut down, under maintenance, or running at low load, the system switches to geothermal independent power generation mode, closes the supercritical carbon dioxide circulation branch, and only retains the main compressor (2), precooler (1) and deep geothermal system; closes the first regulating valve (3), and opens the second regulating valve (10) and the third regulating valve (14). The supercritical carbon dioxide is pressurized by the main compressor (2) and injected into the deep geothermal reservoir (12) through the second regulating valve (10). After absorbing geothermal energy underground, it enters the second turbine (15) through the production well (13) and the third regulating valve (14) to generate electricity and then returns to the precooler (1) and circulates.

9. The method according to claim 6, characterized in that: Under any operating condition, by adjusting the opening of the turbine bypass valve (17), the ratio of working fluid entering the second turbine (15) and directly entering the precooler (1) is controlled, thereby achieving coordinated regulation between power generation and heat supply.

10. The method according to claim 6, characterized in that: When the heating demand increases, the system simultaneously activates the supercritical carbon dioxide cycle power generation mode and the geothermal power generation mode. The first regulating valve (3), the second regulating valve (10) and the third regulating valve (14) are opened, and the opening of the turbine bypass valve (17) is adjusted so that some of the high-temperature and high-pressure supercritical carbon dioxide from the deep geothermal reservoir (12) bypasses the second turbine (15) and directly enters the precooler (1) to exchange heat with the circulating water, thereby reducing the work done by the second turbine (15) and improving the system's heating capacity.

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