Deep geothermal energy large well depth evaporator and cogeneration system

Abstract

The invention discloses a deep geothermal energy large well depth evaporator and a combined heat and power system, and the deep geothermal energy large well depth evaporator comprises a first pipe body which is composed of an upper part located at a medium temperature section and a lower part located at a high temperature section; the first pipe body forms a high-temperature heat removal channel; the second pipe body is arranged outside the first pipe body and is positioned at the upper part of the first pipe body; a medium-temperature heat removal channel is formed between the second pipe body and the first pipe body; and the segmented open type buffer solution pool units are arranged on the lower part of the first pipe body and the second pipe body at intervals and are used for realizing step-by-step distribution and evaporation of a working medium. Compared with an existing deep geothermal energy closed type heat extraction technology, the large well depth evaporator heat extraction module adapts to reservoirs of different depths through the stepped variable-diameter pipe body structure, and graded heat extraction of high-grade and medium-grade steam heat energy is achieved. The heat extraction performance of the large well depth evaporator can be effectively enhanced, and meanwhile the heat-work conversion efficiency of a deep geothermal energy power generation system is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of geothermal energy extraction and utilization technology, specifically to a deep geothermal energy closed-loop heat extraction and combined heat and power system. Background Technology

[0002] Geothermal energy is a clean and stable renewable energy source that provides continuous power, unaffected by weather conditions such as sunshine, rain, snow, or day and night cycles. It is widely distributed and abundant in my country, with medium-deep geothermal energy accounting for over 99% of the total reserves. Deep geothermal energy (typically buried at depths greater than 3000 meters, with well bottom temperatures generally exceeding 150℃) is a clean and stable renewable energy source with higher energy density and the unique ability to directly drive efficient power generation.

[0003] Geothermal reservoirs are the fundamental carriers of deep geothermal energy. In my country, deep geothermal energy is mainly found in dense, low-porosity, and low-water carbonate rock reservoirs (porosity <5%), which vary significantly in depth, geothermal grade, lithology, and permeability. Therefore, there is an urgent need to explore and research suitable and efficient geothermal extraction and utilization theories, methods, and technologies. Furthermore, direct hydrothermal open-loop heat extraction technology faces a series of problems such as reinjection difficulties and ecological damage. Therefore, closed-loop heat extraction technology, which extracts heat but not water, has become the preferred solution. In particular, to meet the demand for clean heating with ultra-high loads and long cycles, the large-scale, efficient, and economical development of deep geothermal energy using closed-loop heat extraction systems is an inevitable trend. However, due to the dependence on external pumps during operation, coaxial casing schemes face challenges such as dramatically increased energy consumption and difficult equipment maintenance in deep wells deeper than 3000m, making it difficult to meet the needs of efficient development of deep geothermal resources. In recent years, ultra-long evaporator passive heat extraction technology has become a research hotspot in the geothermal energy field due to its advantages such as excellent heat transfer performance, no need for external power, and the ability to extract heat at great depths (up to several kilometers). This technology utilizes the spontaneous evaporation / condensation, upward flow, and condensation circulation mechanism of the working fluid in the heat extraction section to achieve heat transfer. However, existing research shows that this technology still has significant technical bottlenecks: First, the upward steam flow resistance and the frictional shear resistance and gravitational pressure drop of the working fluid flowing back down along the wall combine to result in low overall system heat extraction efficiency; second, liquid accumulation at the bottom of the tube inhibits evaporation / boiling behavior, weakening heat transfer performance; third, the different grades of heat in the geothermal reservoir cannot be fully utilized, resulting in low system heat-to-work conversion efficiency. Therefore, limited by the above technical problems, existing ultra-long evaporator passive heat extraction technology is difficult to adapt to the basic requirements of efficient heat extraction and utilization of deep geothermal energy and combined heat and power (CHP).

[0004] In order to overcome the performance limitations of passive heat extraction technology of ultra-long evaporators, existing research has mostly optimized the performance of ultra-long evaporators through structural innovation, thereby promoting the efficient utilization of deep geothermal energy. However, the existing optimization schemes still have the following significant technical bottlenecks: (1) Existing ultra-long evaporators mostly adopt a single-diameter tube structure, which cannot adapt to the temperature gradient differences at different depths. High-pressure steam in the high-temperature zone will inhibit the vaporization phase change in the medium-temperature zone, resulting in the mixing and waste of high and medium grade steam and low heat extraction efficiency. At the same time, the pressure difference between the upper and lower parts of the ultra-long evaporator tube can reach more than 25 MPa (the pressure at the bottom of 3000 meters is ≈30 MPa, and the pressure at the shallow layer of 500 meters is ≈5 MPa). The huge pressure gradient causes the working fluid to form serious liquid accumulation in the middle and lower parts, which directly leads to the failure of evaporation phase change. (2) The ultra-long evaporator tube lacks targeted insulation design. During the kilometer-level transportation process, the steam heat loss is serious, and the effective heat energy grade is difficult to fully utilize. (3) Existing power generation systems mostly adopt single-stage turbine structures and are mostly split-type transmission designs. On the one hand, single-stage turbines can only adapt to high-temperature steam of a single grade, while the medium-temperature steam generated simultaneously during the heat extraction process cannot be effectively utilized because the pressure and temperature do not reach the work threshold of the single-stage turbine, resulting in a large amount of irreversible loss of medium-grade heat energy. On the other hand, the split-type transmission structure is prone to violent vibration under high-temperature and high-speed conditions, which directly affects the power generation efficiency and equipment stability, resulting in low overall heat-power conversion efficiency. (4) In conventional combined heat and power systems, a single power supply and heating mode is mostly adopted, lacking a precise adaptation mechanism. Due to the time-varying nature of electricity demand and the seasonal fluctuation of heating demand, the traditional system adopts manual pipeline switching and single fixed-value adjustment methods. Under the coupling of multiple parameters, dynamic adaptation cannot be achieved, often resulting in insufficient heating during the heating season and uncontrolled heat dissipation during the non-heating season, which in turn leads to a reduction in the efficiency of combined heat and power. Therefore, it is urgent to further innovate the pipe structure design, break through the limitations of existing technology, and achieve a comprehensive improvement in the heat extraction performance of ultra-long evaporators in deep thermal storage environments. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a deep geothermal closed-loop heat extraction and cogeneration system that improves heat extraction efficiency and system heat-to-work conversion efficiency.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: This invention first provides a deep geothermal energy large-well deep evaporator, comprising: The first tube body is composed of an upper part located in the medium temperature section and a lower part located in the high temperature section; the first tube body constitutes a high temperature heat extraction channel. The second tube is disposed outside the first tube and located above the first tube; the second tube and the first tube form a medium-temperature heat extraction channel. The segmented open buffer tank unit is spaced apart at the bottom of the first tube and on the second tube to achieve stepwise distribution and evaporation of the working fluid.

[0007] The segmented deep-well evaporator provided by this invention has a second tube body set above the first tube body to form a stepped variable diameter tube body with the first tube body. The stepped variable diameter tube body is adapted to reservoirs of different depths, realizing the staged heat extraction of high and medium grade steam heat energy, solving the problem of low heat extraction efficiency of traditional single-diameter tube bodies, and providing a stable grade steam source for subsequent cascade power generation.

[0008] The segmented deep-well evaporator provided by this invention features a stepped variable-diameter tube body with a casing section designed for enhanced insulation. The inner casing and outer casing of the intermediate-temperature section have an aerogel-filled composite insulation structure on their steam transport channels, achieving excellent insulation of the steam core area and reducing heat loss during long-distance heat transport over kilometers. Conventional ultra-long gravity heat pipes at depths of 3000m can reach pressures exceeding 30MPa at their bottom, while the pressure at a shallow depth of 500m is only about 5MPa. The working fluid inside is subject to a significant pressure gradient, easily leading to severe liquid accumulation in the lower part of the tube body, which in turn causes working fluid evaporation phase change failure. Therefore, the inner wall of each casing is equipped with multiple stepped open buffer pool units, achieving step-by-step distribution of the working fluid and precise control of the evaporation temperature through staged evaporation, effectively solving the problem of liquid accumulation in ultra-long evaporators.

[0009] The segmented deep-well evaporator provided by this invention features a tiered open buffer tank unit, with each unit including a main buffer tank and supporting facilities. m Secondary buffer pools ( m The system consists of an integer greater than or equal to 2, an overflow pipe, a distribution pipe, and a level valve. To prevent evaporation phase change failure due to deep well accumulation, the upper and lower main buffer tanks are connected by an overflow pipe. The top of the overflow pipe is slightly higher than the liquid level in the main buffer tank, and the bottom extends into the next-level main buffer tank, allowing the working fluid to flow stably along the overflow pipe under gravity. Each main buffer tank is connected to a main distribution pipe, and the secondary buffer tank is connected to the main distribution pipe of the corresponding main buffer tank through a branch distribution pipe. A level valve is installed in the branch distribution pipe. When the liquid level in the secondary buffer tank reaches a preset height, the level valve closes to ensure that the working fluid in this stage is fully evaporated into steam at the corresponding depth temperature zone, thereby achieving precise distribution of the working fluid in each open liquid tank of the evaporation section. After the liquid level in the main buffer tank rises to the overflow height, the working fluid enters the next-level main buffer tank through the overflow pipe, further realizing the staged heat extraction of high and medium grade thermal energy.

[0010] The segmented deep-well evaporator provided by this invention has open buffer tanks arranged at intervals along the casing axis, with a total number of [number missing]. n ( n (Any integer greater than 2), the axial spacing between adjacent buffer cell units is d ,d The value must be appropriate for the depth arrangement requirements of the pipe axis; the width of the main buffer tank is set to... w 1. Set the height to h 1. Set the width of the secondary buffer pool to... w 2. Set the height to h 2. The geometry of the main buffer tank must meet the following requirements. w 1< D and h 1< D ( D (The inner diameter of the high-temperature or medium-temperature section sleeve), the geometry of the secondary buffer tank must meet the following requirements. w 2< w 1 and h 1< h 1. Ammonia is selected as the working medium filling the liquid pool.

[0011] This invention also provides a deep geothermal energy closed-loop heat extraction and combined heat and power system, comprising: The deep geothermal energy large-well deep evaporator described above; The first-stage turbine is connected to the high-temperature heat extraction channel and is used to convert the high-temperature steam flowing out of the high-temperature heat extraction channel into mechanical energy to drive the generator to generate electricity; The secondary turbine, connected to the medium-temperature heat extraction channel, is used to convert the medium-temperature steam flowing out of the medium-temperature heat extraction channel into mechanical energy to drive the generator to generate electricity.

[0012] The deep geothermal closed-loop heat extraction and cogeneration system provided by this invention combines a segmented large-well deep evaporator, a two-stage turbine power generation and cogeneration module. The two turbines effectively improve the system's heat-to-work conversion efficiency by performing work on steam of different grades in stages. The cogeneration module combines the system's condensation waste heat and the power supply from the two-stage turbines, achieving efficient seasonal cascade utilization of heat and power through parameter adaptive control. The insulation enhancement of the casing section effectively reduces heat loss during steam transport through the design of the inner casing and outer casing surfaces in the medium-temperature section.

[0013] The deep geothermal closed-loop heat extraction and combined heat and power (CHP) system provided by this invention includes a primary turbine that converts high-temperature steam flowing from the high-temperature section and the medium-temperature section of the inner casing into mechanical energy to drive a generator. The steam discharged from the primary turbine after its work is mixed with medium-temperature steam flowing from the outer casing of the heat extraction module and then enters the secondary turbine for power generation, effectively improving the system's heat-to-work conversion efficiency. The output of the secondary turbine is connected to a ground-based condensation module. The ground-based condensation module condenses the steam generated by power generation into a liquid working fluid and returns it to the segmented deep-well evaporator heat extraction module, while simultaneously recovering the heat released during condensation and transferring it to the CHP module. Addressing the difficulty of conventional CHP systems in accurately adapting to the time-varying nature of electricity consumption and the fluctuations in heating, the CHP module uses load tracking adaptive control to decouple system parameters and adaptively adjust pipeline valve openings, achieving dynamic CHP during the heating season and direct dissipation during the non-heating season.

[0014] The deep geothermal closed-loop heat extraction and combined heat and power system provided by this invention includes a turbine power generation module comprising a primary turbine, a secondary turbine, a direct-drive rotor, a steam input pipeline, and a steam exhaust pipeline. Conventional single-stage turbine power generation systems often employ a split-type transmission structure, which is prone to severe vibration under high-temperature and high-speed operating conditions, thus affecting power generation efficiency. Therefore, the turbine power generation module uses a direct-drive rotor to make the primary and secondary turbines rotate coaxially with the generator, and adjusts the stiffness and damping to control vibration, thereby maintaining synchronous operation of the two turbines and controlling vibration stability. At the same time, conventional single-stage turbine power generation systems can only adapt to high-temperature steam of a single grade, while the medium-temperature steam pressure and temperature generated simultaneously during the heat extraction process of the deep well evaporator cannot meet the work threshold of the single-stage turbine, leading to irreversible heat loss. High-temperature and high-pressure steam flowing out of the high-temperature section and the medium-temperature section inner section of the evaporative heat extraction module enters the first-stage turbine directly through the steam input pipeline and drives the generator to generate electricity. The steam discharged from the first-stage turbine after doing work mixes with the medium-temperature and medium-pressure steam flowing out of the outer tube of the heat extraction module and enters the second-stage turbine to generate electricity, providing a stable steam source for the second-stage turbine, effectively improving the system's heat-to-work conversion efficiency, and ensuring full utilization of the long-distance, deep thermal energy cascade. The steam generated by the second-stage turbine enters the ground condensation module through the steam exhaust pipeline.

[0015] The deep geothermal closed-loop heat extraction and combined heat and power (CHP) system provided by this invention includes a ground condensing module comprising a condenser, a storage tank, a working fluid pump, and a return pipe. The condenser exchanges heat with the steam supplied by the directly connected integrated turbine power generation module. After absorbing the heat from the steam, the heat exchange medium within the condenser carries the heat to the CHP module, achieving building heating during the heating season and direct heat dissipation during the non-heating season. The steam, after being cooled by the condenser, becomes a liquid working fluid and is stored in the storage tank to ensure the continuity and stability of the cycle. One side of the storage tank is connected to the working fluid pump and the return pipe. Driven by the working fluid pump, the condensed liquid working fluid is injected through the return pipe into the evaporator of the segmented deep-well evaporator heat extraction module to replenish the working fluid, thus completing a full heat extraction cycle.

[0016] The deep geothermal closed-loop heat extraction and combined heat and power (CHP) system provided by this invention includes a CHP module comprising a user terminal, a cooling tower, heating supply pipelines, a temperature rise rate monitoring unit, an online power consumption identification unit, a liquid replenishment controller, a load adaptive controller, and a condensing pressure controller. Conventional CHP systems suffer from complex multi-parameter coupling issues and rely on manual pipeline switching and single-value adjustments, making it impossible to accurately adapt to the time-varying nature of power demand and the fluctuations in heating demand. This leads to insufficient heating during the heating season and uncontrolled heat dissipation during the non-heating season, affecting condensing efficiency. Therefore, when the ground condensing module delivers the heat exchange medium of the condenser to the user end and the cooling tower through the heating supply pipeline, the temperature rise rate monitoring unit and the online power consumption identification unit identify the evaporator temperature rise and power load in real time, and feed the collected signals back to the liquid replenishment controller and the load adaptive controller respectively, so as to adaptively adjust the opening of the pipeline valves, thereby realizing dynamic cogeneration of the building during the heating season and direct dissipation during the non-heating season; after the heat exchange medium of the condenser is heat exchanged at the user end or the cooling tower, the condensing pressure controller adjusts the pressure in the condenser in real time according to the demand, thereby realizing decoupled control of the system and improving the efficiency and stability of the cogeneration system.

[0017] Compared with the prior art, the present invention has the following advantages: (1) To address the problems of low heat extraction efficiency, large heat loss during long-distance transport, and liquid accumulation in the lower part of conventional single-diameter ultra-long gravity heat pipes, the segmented deep-well evaporator heat extraction module adapts to reservoirs of different depths through a stepped variable-diameter pipe structure, realizing the staged heat extraction of high and medium-grade steam heat energy, solving the problem of low heat extraction efficiency of traditional single-diameter pipes, and providing a stable steam source for subsequent cascade power generation. In addition, the inner wall of the segmented deep-well evaporator is equipped with multiple stepped open buffer pool units. The buffer pools are connected by overflow pipes and level valves to realize the step-by-step distribution of evaporation working fluid and precise control of evaporation temperature, effectively solving the problem of liquid accumulation in ultra-long evaporators.

[0018] (2) To address the problems of low heat-to-work conversion efficiency and large irreversible heat loss in conventional single-stage turbines, a two-stage direct-drive turbine motor is adopted. The first-stage turbine converts the high-temperature steam flowing out of the high-temperature section and the inner section of the medium-temperature section into mechanical energy to drive the generator to generate electricity. The steam discharged after the first-stage turbine has done its work mixes with the medium-temperature steam flowing out of the outer tube of the heat extraction module and then enters the second-stage turbine to generate electricity, effectively improving the system's heat-to-work conversion efficiency and ensuring full utilization of the long-distance, deep thermal energy cascade.

[0019] (3) The steam in the lower part of the deep well evaporator has a large heat loss during long-distance transportation. Therefore, through the insulation enhancement design of the casing, an aerogel-filled composite insulation structure is provided on the surface of the steam transportation channel of the inner casing and the outer casing of the medium temperature section, which effectively reduces the heat loss of steam during long-distance heat transportation at the kilometer level.

[0020] (4) In view of the problem that conventional combined heat and power systems are difficult to accurately adapt to the time-varying nature of electricity consumption and the fluctuation of heating, the present invention decouples the parameters of the combined heat and power system through load tracking adaptive control, and adaptively adjusts the opening of pipeline valves to realize dynamic combined heat and power in the building during the heating season and direct dissipation during the non-heating season, thereby improving the efficiency and stability of the combined heat and power system. Attached Figure Description

[0021] Figure 1 This is a three-dimensional structural diagram of the segmented deep-well evaporator of the present invention; Figure 2 for Figure 1 A schematic diagram of the two-dimensional structure; Figure 3 for Figure 2 Enlarged schematic diagram of part A; Figure 4 A schematic diagram of two-dimensional reservoir heat exchange in a segmented deep-well evaporator. Figure 5 This is a schematic diagram of the deep geothermal energy closed-loop heat extraction and combined heat and power system of the present invention; Figure 6 This is a schematic diagram of the thermal insulation reinforcement structure of the casing section of the deep well evaporator of the present invention; Figure 7 for Figure 6 Enlarged schematic diagram of part B; Figure 8 This is a schematic diagram of the control logic for a combined heat and power system. Figure 9 This is a diagram of the model predictive controller structure.

[0022] In the diagram: 1. Cascade reducing pipe; 2. Outer sleeve; 3. Inner sleeve; 4. Main buffer tank; 5. Secondary buffer tank; 6. Overflow pipe; 7. Main distribution pipe; 8. Branch distribution pipe; 9. Liquid level valve; 10. Primary turbine; 11. Direct-connected rotor; 12. Secondary turbine; 13. Steam input pipe; 14. Steam exhaust pipe; 15. Condenser; 16. Liquid storage tank; 17. Working fluid pump; 18. Return pipe; 19. Cooling tower; 20. User end; 21. Aerogel-filled composite insulation structure. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] The following is based on Figures 1-9 This invention describes a specific implementation scheme for the deep geothermal energy large-well deep evaporator and combined heat and power system provided by the present invention.

[0025] Figure 1 This is a three-dimensional structural diagram of a deep geothermal energy large-well evaporator. The deep geothermal energy large-well evaporator adopts a stepped variable diameter tube body 1, which consists of an outer sleeve 2 and an inner sleeve 3. The inner sleeve 3 serves as the first tube body, and the outer sleeve 2 serves as the second tube body. The outer sleeve 2 is located above the inner sleeve 3. The stepped variable diameter tube body 1 is divided into a medium-temperature section and a high-temperature section from top to bottom to adapt to geothermal reservoirs at different depths. The medium-temperature section is a double-sleeve structure of the inner sleeve 3 and the outer sleeve 3, and the steam transport channel is insulated to reduce heat loss. The high-temperature section is the heat extraction section. At the same time, primary and secondary buffer pools with successively decreasing dimensions are arranged axially at intervals inside the outer sleeve 2 and the inner sleeve 3 to enhance heat exchange.

[0026] Within the stepped variable-diameter tube 1, stepped, segmented open buffer solution tank units A are distributed along the axial direction of the tube, such as... Figure 3 As shown. The open buffer tank units A, arranged in stepped segments along the axial direction of the tube, are equidistantly distributed on the evaporator sleeve wall. Each open buffer tank unit A includes one main buffer tank 4 and its associated... m 5 secondary buffer tanks ( m (Integers greater than or equal to 2). The main buffer tank 4 and secondary buffer tank 5 are arranged at intervals along the axial direction of the sleeve, and the total number of open buffer tank units is... n ( n (A positive integer greater than 2), the axial spacing between adjacent buffer cell units is d , dThe value of needs to be appropriate for the depth arrangement requirements of the pipe axis; the width of the main buffer tank 4 is set to w 1. Set the height to h 1. The width of the secondary buffer pool 5 is set to w 2. Set the height to h 2. The geometric dimensions of the main buffer tank 4 must meet the following requirements. w 1< D and h 1< D , D The inner diameter of the high-temperature or medium-temperature section sleeve, and the geometric dimensions of the secondary buffer tank 5 must meet the following requirements. w 2< w 1 and h 2< h 1. Ammonia is selected as the working medium filling the liquid pool.

[0027] More specifically, the upper and lower main buffer tanks are connected by an overflow pipe 6. The top of the overflow pipe is slightly higher than the liquid level in the main buffer tank 4, and the bottom extends into the next-level main buffer tank 4. Simultaneously, each main buffer tank 4 is connected to a main distribution pipe 7, and the secondary buffer tank 5 is connected to the main distribution pipe of the corresponding main buffer tank via branch distribution pipes 8. A level valve 9 is installed in the branch distribution pipe 8, which closes when the liquid level in the secondary buffer tank 5 reaches a preset height. After the liquid level in the main buffer tank 4 rises to the overflow height, the working fluid enters the next-level main buffer tank through the overflow pipe 6, further realizing the staged heat extraction of high and medium grade thermal energy.

[0028] Figure 4 This is a schematic diagram of a two-dimensional reservoir heat exchange in a segmented deep-well evaporator. The segmented deep-well evaporator adapts to reservoirs of different depths through a stepped variable-diameter pipe body 1, enabling graded heat extraction of high- and medium-grade steam thermal energy.

[0029] This invention provides a deep geothermal closed-loop heat extraction and combined heat and power (CHP) system, comprising a segmented deep-well evaporator heat extraction module, a turbine power generation module, a surface condensation module, and a CHP module. For example... Figure 5As shown, the segmented deep-well evaporator heat extraction module adapts to reservoirs of different depths through a stepped variable-diameter pipe body 1, achieving graded heat extraction of high- and medium-grade steam thermal energy. The pipe body adopts a casing section insulation enhancement method, which insulates the surface of the steam transport channel of the medium-temperature section inner casing 3 and the medium-temperature section outer casing 2, to reduce heat loss of steam during long-distance heat transport. Its output end is connected to the turbine power generation module via the steam input pipeline 13. The turbine power generation module adopts a two-stage turbine motor, in which the first-stage turbine 10 converts the high-temperature steam flowing out of the high-temperature section casing and the medium-temperature section inner casing 3 into mechanical energy to drive the generator to generate electricity. The steam discharged from the first-stage turbine 10 after performing work mixes with the medium-temperature steam flowing out of the outer casing 2 of the heat extraction module and enters the second-stage turbine 12 for power generation. The output end of the second-stage turbine is connected to the ground condensation module via the steam exhaust pipe 14. The ground condensation module condenses the steam after power generation into a liquid working fluid, which is then fed back to the segmented deep-well evaporator heat extraction module. At the same time, it recovers the heat released during condensation and transfers it to the combined heat and power (CHP) module. The CHP module uses load tracking adaptive control to decouple the system parameters and adaptively adjust the opening of pipeline valves to achieve dynamic CHP in the heating season and direct heat and power dissipation in the non-heating season.

[0030] Figure 6 This is a schematic diagram of the insulation reinforcement structure of the casing section of the deep-well evaporator according to the present invention. The stepped variable-diameter pipe body of the deep-well evaporator adopts the casing section insulation reinforcement design B, as shown in Figure 1. Figure 7 As shown, the surface of the steam transport channel of the inner and outer casings of the medium-temperature section is provided with an aerogel-filled composite insulation structure 21, which achieves good insulation of the steam core area and reduces the heat loss of steam during long-distance heat transport over kilometers.

[0031] The turbine power generation module includes a primary turbine 10, a direct-drive rotor 11, a secondary turbine 12, a steam input pipeline 13, and a steam exhaust pipeline 14. High-temperature, high-pressure steam flowing from the high-temperature section and the inner section of the medium-temperature section of the evaporative heat extraction module enters the primary turbine 10 directly through the steam input pipeline 13, driving the generator to generate electricity. The steam discharged from the primary turbine 10 after performing work mixes with the medium-temperature, medium-pressure steam flowing from the outer casing of the heat extraction module before entering the secondary turbine 12 to generate electricity, providing a stable steam source for the secondary turbine 12. This effectively improves the system's heat-to-work conversion efficiency and ensures full utilization of the long-distance, deep-seated thermal energy cascade.

[0032] The ground-based condensing module includes a condenser 15, a liquid storage tank 16, a working fluid pump 17, and a return pipe 18. The condenser exchanges heat with the steam supplied by the direct-connected integrated turbine power generation module. After absorbing the heat from the steam, the heat exchange medium in the condenser 15 carries the heat to the combined heat and power (CHP) module, enabling heating at the user end 20 during the heating season and direct dissipation of heat in the cooling tower 19 during the non-heating season. The steam, after being cooled by the condenser 15, becomes a liquid working fluid and is stored in the liquid storage tank 16 to ensure the continuity and stability of the cycle. One side of the liquid storage tank 16 is connected to the working fluid pump 17 and the return pipe 18. Driven by the working fluid pump 17, the condensed liquid working fluid is injected through the return pipe 18 into the evaporator of the segmented deep-well evaporator heat extraction module to replenish the working fluid, thus completing a complete heat extraction cycle.

[0033] The load tracking adaptive control logic for the combined heat and power module is divided into a main load tracking loop, a condensing pressure control loop, and two auxiliary loops: a liquid supply flow control loop and a liquid tracking main loop. Figure 8 Based on the actual application background of the combined heat and power system, the main control target is power generation. The actual power demand of the user side is tracked in real time, and the opening of the turbine inlet valve is controlled to achieve precise matching of power supply load. The auxiliary control targets are the condensing pressure of the heating circuit and the temperature rise rate of the working fluid in the heat pipe. The speed of the working fluid pump and the heating pump is adjusted by feedforward. The auxiliary control circuit adopts a PI controller, as shown in equation (1); the main control circuit adopts a model predictive controller (MPC) based on online identification and update prediction model. The controller structure is as follows. Figure 9 .

[0034] (1) The adaptive control method relies on high-precision linearized mathematical model identification. A recursive least squares method with a forgetting factor is introduced to identify the dynamic response relationship between turbine power generation and intake valve opening online. A second-order state-space equation is selected to describe this characteristic, and its mathematical expression is: (2) in: (3) In the formula: τ For time, the integral in τ Indicates from 0 to τ A continuous time variable at any given moment; u ( τ ) for controller τ Output signal at time; k p This is the proportional gain coefficient; e ( τ )for τ Error signal at time; x kThis is a state variable vector, which in this invention is a 2×1 column matrix, with two elements representing turbine power generation and the rate of change of power generation, respectively. x k+1 (Indicates the next moment); u k The input signal, in this invention, refers to the intake valve opening. y k This is the system output signal, corresponding to the measured value of turbine power generation; A Here is the state transition matrix. a ij For matrix A The elements reflect the dynamic characteristics of the system. B For the input matrix, b i For matrix B The elements reflect the weights of the input's influence on the state; C For the output matrix, c i For matrix C The elements reflect the weights of the state's contribution to the output; D This is the direct pathway matrix, which is set to 0 in this study. d For matrix D scalar elements; T This is the transpose symbol.

[0035] Using recursive least squares with a forgetting factor for parameter estimation can enhance the sensitivity of the identification process to new data by reducing the weight of historical data, thereby tracking time-varying parameters. Performance metrics are then used. J for: (4) In the formula: λ Forgetting factor (0 < λ <1), in this study, the value is 0.97; L This represents the total number of steps taken from the start to the current position. k For the summation variable; y ( k )for k The actual system output at any given time; The regression vector includes all input and output data. The parameter vector to be estimated is updated in real time over time.

[0036] The parameter estimation formula is: (5) in: (6) In the formula: for kThe latest update i Group parameters; for k- The 1st update i Group parameters; K i ( k ) is the gain matrix, P i ( k ) is the covariance matrix. a i , b i As weight.

[0037] Furthermore, this invention introduces an adaptive model predictive controller (AMPC), which linearizes the dynamic relationship between turbine power generation and inlet valve opening using a recursive least squares method with a forgetting factor. This linearized state-space model is updated in real time, thereby updating the AMPC prediction model and enhancing the precise control of the combined heat and power (CHP) system's electrical load. For this research object, considering the prediction model of the aforementioned system, turbine power generation and its change are selected as state variables, and inlet valve opening is selected as the input variable. To achieve the control objective, the following cost function is constructed: (7) In the formula: Q This is the error weight matrix; r ( k () is used as the reference trajectory; y ( k () is the system output; r ( k )- y ( k The tracking error is the difference between the target and the actual value. R To control the weight matrix, u Input signals to the controller.

[0038] Based on the initial state-space equations, k Predicting the future k+ 1 to k+N- All inputs and outputs at time 1 ( N To predict the time-domain step size, the optimal input signal for the controller is calculated using a cost function. u and only k+ Execution at 1 moment k The controller signal calculated at time 1 is used, while the predictive control signals at other times are discarded. Then, based on... k+The real-time output at time 1 is recalculated to update the controller signal for the next time step, thus realizing the rolling optimization process. In this invention, the prediction step size is set to 30, the control step size is set to 3, the input error weight is set to 0.25, and the output error weight is set to 0.75.

[0039] During adaptive control, the controller updates the prediction model in real time based on the dynamic response relationship between turbine power generation and turbine inlet valve opening. With the objective function of accurately tracking user-side electricity demand, it achieves closed-loop feedback regulation of the inlet valve opening. Simultaneously, it adjusts the working fluid pump speed according to the temperature rise rate to match the liquid supply and improve the effective power of the working fluid. Furthermore, it adjusts the heating pump speed based on condensing pressure feedback to maintain stable condensing pressure and achieve stable building heating. Ultimately, this achieves efficient and stable adaptive control of combined heat and power (CHP), significantly improving the economics of the CHP system.

[0040] The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. The parameters can be appropriately adjusted according to the specific working conditions to achieve the best implementation effect.

Claims

1. A deep geothermal energy large-well deep evaporator, characterized in that, include: The first tube body is composed of an upper part located in the medium temperature section and a lower part located in the high temperature section; the first tube body constitutes a high temperature heat extraction channel. The second tube is disposed outside the first tube and located above the first tube; the second tube and the first tube form a medium-temperature heat extraction channel. The segmented open buffer tank unit is spaced apart at the bottom of the first tube and on the second tube to achieve stepwise distribution and evaporation of the working fluid.

2. The deep geothermal energy large-well deep evaporator according to claim 1, characterized in that, The segmented open buffer tank unit includes one main buffer tank and supporting facilities. m Each secondary buffer tank is connected to the primary buffer tank via an overflow pipe. The top of the overflow pipe is slightly higher than the liquid level in the primary buffer tank, and the bottom extends into the next primary buffer tank, allowing the working fluid to flow stably and spontaneously along the overflow pipe under gravity. Each primary buffer tank is connected to a main distribution pipe, and the secondary buffer tanks are connected to the main distribution pipes of the corresponding primary buffer tanks via branch distribution pipes. Each branch distribution pipe is equipped with a level valve, which closes when the liquid level in the secondary buffer tank reaches a preset height, ensuring that the working fluid in this stage is fully evaporated into vapor in the corresponding depth temperature zone, thereby achieving precise distribution of the working fluid in each open liquid tank of the evaporation section.

3. The deep geothermal energy large-well deep evaporator according to claim 2, characterized in that, The geometry of the main buffer tank satisfies w 1< D and h 1< D ,in, D The inner diameter of the first tube. w 1 is the width of the main buffer pool. h 1. The height of the primary buffer tank is set; the geometry of the secondary buffer tank satisfies... w 2< w 1 and h 2< h 1, w 2 represents the width of the secondary buffer pool. h 2 represents the height of the secondary buffer pool.

4. The deep geothermal energy large-well deep evaporator according to claim 1, characterized in that, A heat-insulating and reinforcing structure is provided on the upper part of the first tube and on the second tube.

5. The deep geothermal energy large-well deep evaporator according to claim 4, characterized in that, The thermal insulation enhancement structure is an aerogel-filled composite insulation structure set on the surface of the medium-temperature heat extraction channel.

6. A deep geothermal energy closed-loop heat extraction and combined heat and power system, characterized in that, include: The deep geothermal energy large-well deep evaporator according to any one of claims 1-5; The first-stage turbine is connected to the high-temperature heat extraction channel and is used to convert the high-temperature steam flowing out of the high-temperature heat extraction channel into mechanical energy to drive the generator to generate electricity; The secondary turbine, connected to the medium-temperature heat extraction channel, is used to convert the medium-temperature steam flowing out of the medium-temperature heat extraction channel into mechanical energy to drive the generator to generate electricity.

7. The deep geothermal closed-loop heat extraction and combined heat and power system according to claim 6, characterized in that, Also includes: The steam generated by the secondary turbine power generation enters the ground condensation module through the steam exhaust pipe.

8. The deep geothermal closed-loop heat extraction and combined heat and power system according to claim 6, characterized in that, The ground condensation module includes a condenser, a liquid storage tank, a working fluid pump, and a return pipe; the condenser condenses steam into a liquid working fluid and stores it in the liquid storage tank; the working fluid pump is used to pump the working fluid in the liquid storage tank through the return pipe to the segmented open buffer pool unit.

9. The deep geothermal closed-loop heat extraction and combined heat and power system according to claim 6, characterized in that, Also includes: The combined heat and power (CHP) module includes a user terminal, a cooling tower, heating supply pipelines, a temperature rise rate monitoring unit, an online power consumption identification unit, a liquid replenishment controller, a load adaptive controller, and a condensing pressure controller. When the ground-mounted condensing module delivers the heat exchange medium from the condenser to the user terminal and cooling tower via the heating supply pipelines, the temperature rise rate monitoring unit and the online power consumption identification unit identify the evaporator temperature rise and power load in real time, feeding back the collected signals to the liquid replenishment controller and the load adaptive controller, respectively, to adaptively adjust the pipeline valve openings, achieving dynamic CHP during the heating season and direct heat dissipation during the non-heating season. After the heat exchange medium from the condenser undergoes heat exchange at the user terminal or cooling tower, the condensing pressure controller adjusts the pressure inside the condenser in real time according to demand, achieving decoupled control of the system and improving the efficiency and stability of the CHP system.

10. The deep geothermal closed-loop heat extraction and combined heat and power system according to claim 6, characterized in that, The steam discharged after the first-stage turbine performs its work mixes with the medium-temperature steam flowing out of the medium-temperature heat extraction channel and then enters the second-stage turbine for power generation.

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