Geothermal well and heat energy utilization system with integrated thermoelectric power generation function

Abstract

This invention discloses a geothermal well and thermal energy utilization system integrating thermoelectric power generation, belonging to the field of geothermal energy development and thermoelectric power generation technology. It aims to solve the problems of low geothermal utilization rate, severe scaling and corrosion, unstable output, and poor reinjection sustainability in traditional systems. The system includes a layered geothermal acquisition module, a multi-stage thermoelectric power generation and energy storage coupling module, an intelligent scale and corrosion prevention module, a high-efficiency reinjection and waste heat reuse module, and an AI intelligent control module. This invention can realize full-gradient geothermal acquisition and cascade power generation at different depths, significantly improving thermal utilization rate and power generation efficiency, reducing extraction costs. Through coordinated scale and corrosion prevention, energy storage, and AI linkage, it achieves zero-pollution long-term operation and maintenance, stable power generation output, and can also recover reinjection waste heat and optimize the reinjection structure, achieving sustainable and cyclical development of geothermal resources.

Description

Technical Field

[0001] This invention relates to the field of geothermal well power generation technology, and in particular to a geothermal well and thermal energy utilization system that integrates thermoelectric power generation function. Background Technology

[0002] In the field of geothermal energy development and thermoelectric power generation, traditional geothermal wells and thermal energy utilization systems that integrate thermoelectric power generation functions have long faced three core pain points due to limitations in design concepts and defects in technical architecture: insufficient resource utilization, poor operational stability, and insufficient sustainability. The specific problems are as follows:

[0003] Firstly, traditional geothermal systems generally adopt a single-depth vertical well acquisition and single energy conversion architecture. On the one hand, the acquisition stage is mostly designed with vertical wells, which can only extract geothermal resources at a fixed depth. If drilling is carried out for deep high-temperature geothermal reservoirs, shallow medium- and low-temperature resources are wasted because they cannot be effectively acquired. If mixed acquisition is adopted to take into account medium- and low-temperature resources, it will lead to direct mixing of deep high-temperature fluids and shallow low-temperature fluids. The high-temperature fluids will not have sufficient heat exchange, and the medium- and low-temperature fluids will not be able to reach the power generation threshold, resulting in a low overall thermal utilization rate of the system. On the other hand, the energy conversion stage mostly relies on a single organic Rankine cycle (ORC) for power generation, without secondary utilization of the medium- and low-temperature waste heat discharged from the ORC, resulting in a low overall power generation efficiency. In addition, some projects need to drill multiple production wells at different depths to obtain multi-gradient geothermal resources, which not only increases drilling costs but also exacerbates the damage to underground rock formations. The comprehensive energy output of a single well can only meet the basic power supply needs, and it is impossible to achieve the goal of multi-purpose well and cascaded high-efficiency development.

[0004] Secondly, traditional geothermal systems face two major challenges in long-term operation. One is the high content of [unclear - possibly referring to a specific type of fluid or component] in the geothermal fluid. , Minerals easily deposit and form scale on the heat exchanger tube walls, with an annual scale thickness of 2-5 mm. At the same time, corrosive components such as H2S in the fluid accelerate tube corrosion, leading to a decrease in heat exchanger efficiency every year. To maintain system operation, it is necessary to shut down the system regularly for cleaning with chemical cleaning agents, 2-3 times a year, with each shutdown lasting 3-5 days. This not only causes a loss of power generation but also generates a large amount of acidic wastewater, polluting the soil and groundwater. Secondly, the temperature of geothermal fluids is prone to fluctuations of ±10-15℃ due to geological conditions. Traditional systems lack effective energy storage and dynamic control methods, resulting in high fluctuations in power output and an inability to provide stable power to users, limiting the application of the system in industrial power supply, residential centralized power supply, and other scenarios.

[0005] In addition, the reinjection process of traditional geothermal systems has obvious design flaws. On the one hand, the low-temperature fluid after power generation is directly reinjected into the ground without waste heat recovery. This waste heat accounts for 15%-20% of the total geothermal energy, which is directly wasted. This not only reduces energy utilization efficiency, but also affects the stability of the geothermal reservoir due to the large temperature difference between the reinjection fluid and the reservoir. On the other hand, reinjection wells mostly adopt open-hole well structures, which only remove large particulate impurities from the fluid through simple filtration devices. The filtration accuracy is poor, and the open-hole structure results in a small contact area between the reinjection fluid and the reservoir, leading to low heat exchange efficiency. This causes a large annual drop in reservoir pressure, which can easily lead to surface subsidence in the long term. At the same time, unfiltered fine impurities can clog the pores of the reservoir, shorten the service life of the geothermal field, and make it impossible to achieve long-term sustainable development of geothermal resources.

[0006] Therefore, this invention proposes a geothermal well and thermal energy utilization system that integrates thermoelectric power generation function. Summary of the Invention

[0007] One objective of this invention is to propose a geothermal well and thermal energy utilization system integrating thermoelectric power generation. This invention can accurately extract shallow, middle, and deep geothermal fluids through a tree-like structure of one main well and three branch wells. Combined with a multi-level coupling architecture of supercritical ORC, flexible three-dimensional TEG, and phase change energy storage, it can significantly improve the system's thermal utilization rate and overall power generation efficiency. At the same time, it eliminates the cost of traditional multi-well mining and significantly increases the comprehensive energy output of a single well. Furthermore, through the synergistic anti-scaling of piezoelectric ceramic ultrasonic transducers and pulsed electric fields, and the dual protection of ceramic coating and sacrificial anode corrosion prevention, combined with the linkage control of phase change energy storage and AI deep reinforcement learning algorithms, it can significantly reduce the annual scale thickness of heat exchangers and extend the life of pipes. This can reduce the fluctuation range of system power generation output and meet the demand for stable power supply.

[0008] According to an embodiment of the present invention, a geothermal well and thermal energy utilization system integrating thermoelectric power generation function includes a layered geothermal acquisition module, a multi-stage thermoelectric power generation and energy storage coupling module, an intelligent anti-scaling and anti-corrosion module, an efficient reinjection and waste heat reuse module, and an AI intelligent control module.

[0009] The stratified geothermal acquisition module includes one main well and three branch wells, with a directional acquisition heat exchanger installed at the end of each branch well.

[0010] The multi-stage thermoelectric power generation and energy storage coupling module includes a supercritical ORC power generation unit, a flexible three-dimensional TEG array, and a phase change energy storage unit. The flexible three-dimensional TEG array is wound around the outer wall of the ORC condenser, and the phase change energy storage unit is filled with… Eutectic salt;

[0011] The intelligent anti-scaling and anti-corrosion module includes an ultrasonic vibration component, a pulsed electric field component, and a ceramic-based composite coating. The ultrasonic vibration component is installed on the outer wall of the heat exchanger pipe, the pulsed electric field component is located inside the heat exchanger, and the ceramic-based composite coating is sprayed onto the surface of the pipe that is in contact with the geothermal fluid.

[0012] The high-efficiency reinjection and waste heat reuse module includes a shell-and-tube waste heat exchanger and a porous medium reinjection well. The waste heat exchanger is used to preheat domestic water or shallow geothermal fluid. The inner wall of the porous medium reinjection well is lined with porous ceramic tubes, and the outside of the tubes is filled with a mixture of quartz sand and montmorillonite.

[0013] The AI ​​intelligent control module includes a sensor group, a deep reinforcement learning algorithm unit, and a PLC execution unit. The sensor group collects temperature, pressure, flow rate, and scale thickness data in real time. The DRL algorithm unit outputs optimized control commands, and the PLC execution unit drives the actions of the execution elements of each module.

[0014] Furthermore, in the stratified geothermal acquisition module, the main well has a depth of 2000-3000m, and the branch wells are respectively opened at depths of 500m, 1500m, and 2500m, and hydrogenated nitrile rubber bidirectional sealing rings are provided at the interface between each branch well and the main well.

[0015] Furthermore, the directional heat exchanger includes a deep heat exchanger and a shallow heat exchanger. The deep heat exchanger is an alloy spiral tube filled with a graphite and silicon carbide composite material. The shallow heat exchanger is a flexible corrugated tube coated with a coating. Nanocoating.

[0016] Furthermore, the flexible three-dimensional TEG array is composed of Composed of a flexible composite thermoelectric module with graphene, the thermoelectric module has a ZT value of 1.8-2.2, and each module contains 100 pairs of thermoelectric arms. The upper and lower surfaces of the thermoelectric arms are respectively bonded to a copper substrate and... The ceramic insulation layer is fixed to the outer wall of the ORC condenser by spiral winding and axial splicing. 20-25 Bi2Te3 and graphene flexible composite thermoelectric modules are arranged per meter of tube wall, and the modules are connected by a 10-series-5-parallel wiring method.

[0017] Furthermore, the phase change energy storage unit includes a stainless steel energy storage tank and a serpentine heat exchange tube. The eutectic salt has a melting point of 60-65℃. When the ORC output power decreases by more than 10%, the energy storage unit releases heat to heat the water to 80-90℃, driving a small screw expander to replenish energy.

[0018] Furthermore, the ultrasonic vibration component employs piezoelectric ceramic ultrasonic transducers, with one transducer arranged every 10m of pipe. The pulsed electric field component includes titanium alloy electrodes and a pulsed power supply, with an electrode spacing of 50-80mm. The ceramic-based composite coating is... The coating is prepared by atmospheric plasma spraying. The intelligent anti-scaling and anti-corrosion module also includes a zinc alloy sacrificial anode, with one set arranged every 500m of well shaft. A polytetrafluoroethylene insulating gasket is provided between the anode and the well shaft to reduce the consumption rate.

[0019] Furthermore, the sensor group of the AI ​​intelligent control module includes a temperature sensor, a pressure sensor, and an electromagnetic flowmeter. The temperature sensor is arranged every 50m in the main well and every 30m in the branch well. The pressure sensor is arranged at the wellhead, bottom of the main well, and inlet and outlet of the heat exchanger. The DRL algorithm unit constructs a neural network model using TensorFlow, with 15 parameters in the input layer, 3 hidden layers, and 8 control commands in the output layer.

[0020] Furthermore, the shell side of the shell-and-tube waste heat exchanger is supplied with pre-reinjection fluid at 25-35°C, while the tube side is supplied with domestic water at 15°C. When the domestic water demand is < When the electric three-way valve switches to the preheating shallow fluid mode, the shallow fluid is preheated from 60°C to 70-80°C. The inner wall of the porous medium reinjection well is lined with alumina porous ceramic pipes. The mass ratio of the quartz sand and montmorillonite mixed medium is 7:3, and the filling thickness is 50mm.

[0021] Furthermore, the DRL algorithm unit in the AI ​​intelligent control module takes multi-objective optimization as its objective, and its optimization objective function is:

[0022]

[0023] in, Let be the system state vector. For control vectors, The total power generation efficiency of the system. For system energy loss, Penalty for scaling / corrosion. , , Let be the weighting coefficient, satisfying ;

[0024] The reward function of the DRL algorithm is:

[0025]

[0026] in, Let be the reward value at time t. Let be the change in total power generation efficiency at time t. Let be the change in system energy loss at time t. Let t be the change in scaling / corrosion penalty at time t. , , It is a positive coefficient used to adjust the relative importance of each objective;

[0027] During each control cycle, the system updates the control variables according to the following strategy:

[0028]

[0029] in, This is the optimal control vector for period t+1. For the maximization operator, The optimal action value function. These are the parameters of a neural network, and they can be updated using gradient descent.

[0030]

[0031] in, For the algorithm's learning rate, This represents the gradient of the objective function with respect to the parameters.

[0032] Furthermore, when the ultrasonic thickness gauge detects a scale thickness > 0.3 mm on the pipe wall, the ultrasonic vibration component and the pulsed electric field component work together to remove the scale. The AI ​​intelligent control module can automatically increase the ultrasonic transducer power by 20%-30% and extend the pulsed electric field duration. The control law is as follows:

[0033]

[0034] in, The ultrasonic transducer power for period t+1. The current power of the ultrasonic transducer during period t. Let t be the scale thickness at time t, 0.25 be the maximum power boost coefficient, and 0.3 be the scale thickness warning threshold.

[0035] The beneficial effects of this invention are:

[0036] 1. This invention utilizes a tree-shaped, layered acquisition structure with one main well and three branch wells to accurately extract geothermal resources at depths of 500m, 1500m, and 2500m. It is complemented by a multi-stage coupled power generation architecture consisting of a supercritical ORC, a flexible three-dimensional TEG, and phase change energy storage. The deep-layer, high-temperature fluid-driven ORC achieves a conversion efficiency of 12.2%, and the 90°C waste heat discharged from the ORC is... The system utilizes a graphene TEG array for secondary power generation, and the waste heat from the TEG at 65°C is stored in eutectic salt for fluctuating energy replenishment. This mode greatly improves the system's thermal utilization rate and overall power generation efficiency, significantly improving upon traditional systems. It also enables multi-layer mining from a single well, eliminating the cost of separate mining from multiple wells in the traditional method. The comprehensive energy output of a single well is significantly higher than that of a traditional vertical well.

[0037] 2. In this invention, piezoelectric ceramic ultrasonic transducers and titanium alloy pulsed electric fields work together to disrupt scale growth, in conjunction with... The ceramic coating and zinc alloy sacrificial anode significantly reduce the annual scale thickness of the heat exchanger, extend the life of the pipes, and eliminate the need for chemical cleaning, achieving zero-pollution operation and maintenance. At the same time, the phase change energy storage unit is linked with the AI ​​deep reinforcement learning DRL algorithm. When the ORC output fluctuation is greater than 10%, the energy storage unit releases eutectic salt heat within 30 seconds to drive the energy expansion machine. Combined with the DRL algorithm, the parameters of each module are adjusted in real time, resulting in a smaller system output fluctuation amplitude, which far exceeds the stability level of traditional systems.

[0038] 3. In this invention, the waste heat of the fluid at 25-35℃ before reinjection is first recovered through a shell-and-tube heat exchanger. When the demand for domestic water is sufficient, the domestic water is preheated from 15℃ to 30-35℃. When the demand is insufficient, the shallow 60℃ fluid is preheated to 70-80℃, which greatly improves the waste heat recovery rate. It adopts a reinjection well structure with a porous ceramic tube, quartz sand and montmorillonite mixed medium. The mixed medium has high filtration accuracy. The porous ceramic tube increases the contact area between the fluid and the thermal reservoir, which effectively improves the heat exchange efficiency between the reinjection fluid and the thermal reservoir. The annual pressure drop of the thermal reservoir is controlled within 0.07MPa, and the reinjection rate reaches 100%, realizing the resource cycle of extraction, utilization and reinjection, and avoiding groundwater depletion and surface subsidence. Attached Figure Description

[0039] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0040] Figure 1 This is a schematic diagram of the overall framework of a geothermal well and thermal energy utilization system that integrates thermoelectric power generation function according to the present invention.

[0041] Figure 2 This is a schematic diagram showing the daily power generation of a geothermal well and thermal energy utilization system that integrates thermoelectric power generation function according to the present invention.

[0042] Figure 3 This is a comparison chart of the waste heat recovery rate of a geothermal well and thermal energy utilization system with integrated thermoelectric power generation function proposed in this invention and a traditional geothermal system. Detailed Implementation

[0043] To make the technical means and objectives and effects of the present invention easier to understand, the embodiments of the present invention will be described in detail below with reference to specific illustrations.

[0044] like Figure 1-3 As shown, this invention discloses a geothermal well and thermal energy utilization system with integrated thermoelectric power generation function, including a layered geothermal acquisition module, a multi-stage thermoelectric power generation and energy storage coupling module, an intelligent anti-scaling and anti-corrosion module, an efficient reinjection and waste heat reuse module, and an AI intelligent control module.

[0045] The stratified geothermal acquisition module includes one main well and three branch wells, with a directional acquisition heat exchanger installed at the end of each branch well;

[0046] The main well uses N80 grade steel oil casing, with a drilling depth of 2700m. The inner wall of the well is sandblasted to remove rust, ensuring the adhesion of the subsequent anti-corrosion coating.

[0047] Three branch wells were drilled laterally using directional drilling tools at depths of 500m, 1500m, and 2500m from the main well, respectively. L80-13Cr stainless steel casing was used. The angle between the branch well and the main well was controlled at 35°. The end extension length of each branch well was 70m.

[0048] Hydrogenated nitrile rubber bidirectional sealing rings are installed at the interfaces between each branch well and the main well. The seal is achieved by pre-tightening the flange bolts. Pressure testing showed no leakage, effectively preventing cross-flow and contamination of geothermal fluids at different depths.

[0049] Secondly, the directional heat exchanger includes a deep heat exchanger and a shallow heat exchanger. The deep heat exchanger is an alloy spiral tube filled with a graphite and silicon carbide composite material, while the shallow heat exchanger is a flexible corrugated tube with an outer coating. Nanocoating;

[0050] Specifically, the deep heat exchanger uses alloy spiral tubes, with the outside of the tubes filled with a graphite and silicon carbide composite material. After filling, the gaps are sealed with high-temperature cement grout, and the heat loss rate is less than 3% according to hot testing.

[0051] The shallow heat exchanger uses a flexible PTFE corrugated tube, and the outside of the tube is coated by sol-gel method. Nano-coating, its and With a mass ratio of 3:1, a coating thickness of 7μm, and an adhesion of 5.1MPa, the coating showed no peeling after immersion testing, and the initial scale adhesion was reduced by 60% compared to the uncoated pipe.

[0052] During the data collection process, the electric flow control valves at the inlet of each branch well are dynamically adjusted according to the geothermal fluid temperature: at a deep fluid temperature of 260℃, the valve opening is 82%, and the data collection flow rate is [not specified]. The intermediate fluid temperature is 145℃, the valve opening is 58%, and the flow rate is recorded. The shallow fluid temperature is 58℃, the valve opening is 42%, and the flow rate is recorded. After the three fluids converge in the mixing chamber at the top of the main well, the temperature stabilizes at 198℃ and the pressure at 18MPa. They are then transported to the multi-stage thermoelectric power generation and energy storage coupling module through insulated pipes.

[0053] The mixed 198°C geothermal fluid enters a multi-stage thermoelectric power generation and energy storage coupling module. This module includes a supercritical ORC power generation unit, a flexible three-dimensional TEG array, and a phase change energy storage unit. The flexible three-dimensional TEG array is wound around the outer wall of the ORC condenser, and the phase change energy storage unit is filled with… Eutectic salt;

[0054] Specifically, the supercritical ORC power generation unit is transported to a horizontal shell-and-tube evaporator via a variable frequency working fluid pump. After countercurrent heat exchange with the geothermal fluid, the working fluid is heated to a supercritical state of 125°C.

[0055] The supercritical working fluid enters the twin-screw expander, drives the rotor to rotate and drives the permanent magnet synchronous generator to generate electricity. The output voltage is 690V, which is converted into DC power by a three-phase bridge rectifier and then connected to the 380V system bus.

[0056] The working fluid discharged from the expander enters the plate condenser, condenses into a liquid state, and returns to the working fluid pump to complete the ORC cycle, with a cycle thermal efficiency of 12.2%.

[0057] Among them, the flexible three-dimensional TEG array consists of Composed of a flexible composite thermoelectric module with graphene, the thermoelectric module has a ZT value of 1.8-2.2, and each module contains 100 pairs of thermoelectric arms. The upper and lower surfaces of the thermoelectric arms are respectively bonded to a copper substrate and... Ceramic insulation layer, with silicone rubber sealing at the module edges;

[0058] The flexible three-dimensional TEG array is fixed to the outer wall of the ORC condenser using a spiral winding and axial splicing method, with 20-25 arrays arranged per meter of tube wall. It is a flexible composite thermoelectric module with graphene, and the modules are connected in a 10-series-5-parallel wiring method.

[0059] The TEG cold end is maintained by a cooling water branch, and the temperature difference between the cold and hot ends is stabilized at 64℃. The actual power generation is 61kW, and the conversion efficiency is 8.3%, which is more than 15% higher than that of traditional planar TEG arrays.

[0060] Secondly, the phase change energy storage unit includes a stainless steel storage tank and a serpentine heat exchange tube. The storage tank is made of 304 stainless steel and is filled with... Eutectic salt, with a melting point of 60-65℃, when the ORC output power drops by more than 10%, the energy storage unit releases heat to heat water to 80-90℃, driving a small screw expander to replenish energy;

[0061] The serpentine heat exchange tubes are made of B10 copper-nickel alloy. The 65°C waste heat fluid discharged from the TEG array exchanges heat with the eutectic salt through the heat exchange tubes. The eutectic salt melts from a solid to a liquid state in 4.5 hours, and stores heat after complete melting. ;

[0062] When fluctuations in the local thermal fluid temperature cause an 11% decrease in ORC output power, the AI ​​intelligent control module issues a command, and the energy storage unit switches to heat release mode:

[0063] Molten eutectic salt heats tap water to 85°C, and the high-temperature water drives a small screw expander to replenish energy. The energy replenishment response time is 28 seconds, and the total output fluctuation of the system is controlled within 4.5%.

[0064] In this embodiment, the operating parameters of the supercritical ORC power generation unit and the flexible three-dimensional TEG array are compared in Table 1, which can intuitively demonstrate the synergistic power generation effect of the two:

[0065] Table 1. Operating parameters of supercritical ORC power generation unit and flexible three-dimensional TEG array

[0066] Input fluid temperature (°C) 198 (Mixed Geothermal Fluids) 90 (ORC residual heat) Output fluid temperature (°C) 90 (to TEG) 65 (to waste heat exchanger) Rated power (kW) 500 63 Actual operating power (kW) 488 61 Conversion efficiency (%) 12.2 8.3 Average daily power generation (kWh) 8200 1050

[0067] Throughout the system's operation, the intelligent anti-scaling and anti-corrosion module provides long-term protection for pipes through a triple protection design of ultrasonic vibration, pulsed electric field, and ceramic-based composite coating, as well as limitations on component parameters and control logic.

[0068] Specifically, the intelligent anti-scaling and anti-corrosion module includes an ultrasonic vibration component, a pulsed electric field component, and a ceramic-based composite coating;

[0069] The ultrasonic vibration component uses piezoelectric ceramic ultrasonic transducers, with one transducer arranged for every 10m of pipeline. Specifically, a total of 12 transducers can be arranged on the outer wall of the inlet and outlet pipelines of the ORC evaporator, TEG heat exchanger, and waste heat exchanger. The transducers are fixed with high-temperature resistant adhesive, and the vibration amplitude is 0.12mm.

[0070] Secondly, the pulsed electric field component includes titanium alloy electrodes and a pulsed power supply. The electrodes are made of TA2 pure titanium alloy and are arranged in pairs inside each heat exchanger with a spacing of 65mm between the electrodes. The electrodes are connected to the pulsed power supply.

[0071] When the ultrasonic thickness gauge detected that the scale thickness on the ORC evaporator tube wall reached 0.35mm, the AI ​​intelligent control module automatically increased the ultrasonic transducer power to 104W and adjusted the pulse electric field working cycle from 60min / time to 30min / time; after working together for 40 minutes, the scale thickness on the tube wall dropped to 0.11mm, the scale removal rate was 91%, and there was no chemical cleaning wastewater discharge, which met the environmental protection requirements.

[0072] In addition, ceramic-based composite coatings are The coating was prepared by atmospheric plasma spraying, and the coating raw material was... Powder, under the parameters of spraying power 40kW, spraying distance 150mm, and spraying speed 75mm / s, forms a 125μm thick coating on the inner surface of the main well casing and heat exchanger tubes; after spraying, it is annealed in a vacuum furnace, and the coating hardness reaches 1280HV, the adhesion is 15.5MPa, and after being immersed in geothermal fluid at 260℃ for 180 days, the corrosion rate is only 0.0018mm / year;

[0073] It is worth mentioning that the intelligent anti-scaling and anti-corrosion module also includes zinc alloy sacrificial anodes, with one set arranged every 500m of wellbore. One set can be arranged at the main well depths of 500m, 1000m, 1500m, 2000m, and 2500m. A polytetrafluoroethylene insulating gasket is installed between the anode and the wellbore to reduce the consumption rate. It is fixed by a bracket. According to monitoring, the annual consumption rate of the anode is 4.5kg, which can extend the service life of the wellbore to 19 years.

[0074] The high-efficiency reinjection and waste heat reuse module includes a shell-and-tube waste heat exchanger and a porous media reinjection well. The waste heat exchanger is used to preheat domestic water or shallow geothermal fluids. The inner wall of the porous media reinjection well is lined with porous ceramic tubes, and the outside of the tubes is filled with a mixture of quartz sand and montmorillonite.

[0075] The shell side is supplied with pre-reinjection fluid at 27°C, while the tube side is supplied with domestic water at 15°C. Through counter-current heat exchange, the domestic water is heated to 32°C, meeting the domestic water needs of 180 households in the area, with a waste heat recovery rate of 91.5%.

[0076] When the demand for domestic water in summer drops At that time, the AI ​​intelligent control module controls the electric three-way valve to switch to the preheating shallow fluid mode. Before reinjection, the fluid is transported to the inlet of the shallow heat exchanger through the bypass pipe and mixed with the shallow geothermal fluid at 58°C, raising the temperature of the shallow fluid to 72°C. After the temperature is raised, the input temperature of the TEG array increases from 90°C to 96°C, and the power generation increases to 64kW, which is 4.9% higher than the original power, realizing the secondary efficient utilization of waste heat.

[0077] Secondly, the porous medium reinjection well has a depth of 2600m, an inner diameter of 177.8mm, and an inner wall lined with porous alumina ceramic pipes. The ceramic pipe sections are connected with graphite gaskets, and no leakage was found after pressure testing.

[0078] The space between the ceramic tube and the reinjection well casing is filled with a mixture of quartz sand and montmorillonite, with a mass ratio of 7:3 and a filling thickness of 50 mm. The permeability of the mixture is... Through particle size distribution design, it can filter impurities ≥10μm in the reinjection fluid, avoiding pore blockage in the thermal reservoir;

[0079] During the reinjection process, the reinjection flow rate is controlled by a variable frequency reinjection pump, the reinjection pressure is maintained at 8.2 MPa, and the reinjection rate is 100%. After 12 months of continuous operation, the pressure of the thermal reservoir only dropped by 0.07 MPa (≤0.1 MPa) as monitored by the pressure monitoring well, effectively preventing surface subsidence.

[0080] The AI ​​intelligent control module serves as the central nervous system of the system, including a sensor group, a deep reinforcement learning algorithm unit, and a PLC execution unit. The sensor group collects temperature, pressure, flow rate, and scale thickness data in real time. The DRL algorithm unit outputs optimized control commands, and the PLC execution unit drives the actions of the execution elements of each module.

[0081] The sensor array specifically includes temperature sensors, pressure sensors, electromagnetic flowmeters, and ultrasonic thickness gauges. Temperature sensors are installed every 50m in the main well and every 30m in the branch wells to monitor the temperature of geothermal fluids, heat exchanger working fluid, and energy storage media. Pressure sensors are installed at the wellhead, bottom, and inlet / outlet of each heat exchanger to monitor wellbore pressure, heat exchange system pressure, and reservoir pressure. Electromagnetic flowmeters are installed at the outlet of each branch well, the ORC working fluid pipe, and the reinjection pipe to monitor and collect flow rate, working fluid flow rate, and reinjection flow rate. Ultrasonic thickness gauges are installed at the inlet / outlet pipes of each heat exchanger to monitor the thickness of scale buildup on the pipe walls.

[0082] All sensor data is uploaded to the central control system in real time via a 4G industrial wireless transmission module. The data sampling frequency is once every 10 seconds for temperature, pressure, and flow data, and once every 5 minutes for scale thickness data, ensuring the timeliness and completeness of the data.

[0083] The DRL algorithm unit is based on the TensorFlow framework to build a neural network model. Its structure is an input layer with 15 parameters, a hidden layer with 3 layers, and an output layer with 8 control instructions.

[0084] The input layer includes the temperatures at 500m / 1500m / 2500m in the main well, the inlet and outlet temperatures of the ORC evaporator, the hot and cold end temperatures of the TEG, the temperature of the phase change storage salt, the temperature of the reinjection fluid, the pressure at the wellhead of the main well, the pressure of the thermal reservoir, the flow rates collected in the deep / shallow / middle layers, the reinjection flow rate, and the scale thickness on the heat exchanger tube wall; there are three hidden layers, containing 128, 64, and 32 neurons respectively, with ReLU as the activation function; the output layer includes the opening degree of the flow valves in the deep / shallow / middle layers, the flow rate of the ORC working fluid, the flow rate of the TEG cooling water, the power of the ultrasonic transducer, the working cycle of the pulse electric field, and the switching command of the waste heat exchanger.

[0085] The DRL algorithm unit in the AI ​​intelligent control module aims at multi-objective optimization, and its objective function is:

[0086]

[0087] in, Let be the system state vector. For control vectors, The total power generation efficiency of the system. For system energy loss, Penalty for scaling / corrosion. , , Let be the weighting coefficient, satisfying ;

[0088] in, , , These values ​​can be set to 0.45, 0.3, and 0.25 respectively, prioritizing power generation efficiency.

[0089] The reward function of the DRL algorithm is:

[0090] The reward function of the DRL algorithm is:

[0091]

[0092] in, Let be the reward value at time t. Let be the change in total power generation efficiency at time t. Let be the change in system energy loss at time t. Let t be the change in scaling / corrosion penalty at time t. , , It is a positive coefficient used to adjust the relative importance of each objective;

[0093] in, , , It can be set to 0.55, 0.25, and 0.2 respectively. Within each control cycle, through... Select the optimal control action, where The optimal action value function. For neural network parameters, and through The algorithm updates neural network parameters, converges quickly, and has high control precision.

[0094] The PLC execution unit can receive control commands output by the DRL algorithm unit and convert them into electrical signals to drive the actions of various execution elements, such as controlling the opening degree of the electric flow valve, the frequency of the frequency converter pump, the power of the ultrasonic transducer, and the working cycle of the pulse power supply.

[0095] For example, when the reservoir pressure drops to 8.0 MPa, the PLC controls the reinjection pump flow rate to... Down to At the same time, the acquisition valve of the 500m shallow branch well is closed to avoid over-exploitation of the thermal reservoir and ensure long-term stable operation of the system.

[0096] like Figure 2-3 As shown, the system in this embodiment has been running continuously for one year, and actual monitoring data shows that:

[0097] Energy utilization efficiency: The system generates an average of 9320 kWh of electricity per day, including 8200 kWh from ORC, 1050 kWh from TEG, and 70 kWh from energy storage, with a total power generation efficiency of 19.5%. It supplies an average of 1500 m³ of 32°C domestic hot water per day, meeting the needs of 180 households. The waste heat recovery rate is 91.5%, which is 25% higher than that of traditional geothermal systems.

[0098] Stability and durability: The system output fluctuation is 4.2% (≤5%), the annual scale thickness on the heat exchanger tube wall is 0.25mm (<0.3mm), the annual pressure drop in the thermal reservoir is 0.07MPa (≤0.1MPa), the annual corrosion rate of the pipe is 0.0018mm / year, and the overall service life of the system is expected to reach 18 years.

[0099] Economic and environmental benefits: The system's levelized cost of electricity is 0.155 yuan / kWh, and annual emissions are reduced. Approximately 7,600 tons, with no wastewater or exhaust gas emissions, meeting the requirements of the national "dual carbon" policy.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A geothermal well and heat energy utilization system integrated with a thermoelectric power generation function, characterized in that, It includes a layered geothermal collection module, a multi-stage thermoelectric power generation and energy storage coupling module, an intelligent anti-scaling and anti-corrosion module, an efficient reinjection and waste heat reuse module, and an AI intelligent control module. The stratified geothermal acquisition module includes one main well and three branch wells, with a directional acquisition heat exchanger installed at the end of each branch well. The multi-stage thermoelectric power generation and energy storage coupling module comprises a supercritical ORC power generation unit, a flexible three-dimensional TEG array and a phase change energy storage unit, the flexible three-dimensional TEG array is wound on the outer wall of the ORC condenser, and the phase change energy storage unit is filled co-crystal salt; The intelligent anti-scaling and anti-corrosion module includes an ultrasonic vibration component, a pulsed electric field component, and a ceramic-based composite coating. The ultrasonic vibration component is installed on the outer wall of the heat exchanger pipe, the pulsed electric field component is located inside the heat exchanger, and the ceramic-based composite coating is sprayed onto the surface of the pipe that is in contact with the geothermal fluid. The high-efficiency reinjection and waste heat reuse module includes a shell-and-tube waste heat exchanger and a porous medium reinjection well. The waste heat exchanger is used to preheat domestic water or shallow geothermal fluid. The inner wall of the porous medium reinjection well is lined with porous ceramic tubes, and the outside of the tubes is filled with a mixture of quartz sand and montmorillonite. The AI ​​intelligent control module includes a sensor group, a deep reinforcement learning algorithm unit, and a PLC execution unit. The sensor group collects temperature, pressure, flow rate, and scale thickness data in real time. The DRL algorithm unit outputs optimized control commands, and the PLC execution unit drives the actions of the execution elements of each module.

2. The geothermal well and heat energy utilization system integrated with a thermoelectric function according to claim 1, characterized in that, The stratified geothermal acquisition module has a main well depth of 2000-3000m, and branch wells are respectively opened at depths of 500m, 1500m, and 2500m. Hydrogenated nitrile rubber bidirectional sealing rings are installed at the interface between each branch well and the main well.

3. The geothermal well and heat energy utilization system integrated with a thermoelectric function according to claim 1, characterized in that, The directional heat exchanger includes a deep heat exchanger and a shallow heat exchanger. The deep heat exchanger is an alloy spiral tube filled with a graphite and silicon carbide composite material. The shallow heat exchanger is a flexible corrugated tube with an outer coating. Nanocoating.

4. The geothermal well and heat energy utilization system integrated with a thermoelectric function according to claim 1, characterized in that, The flexible three-dimensional TEG array is composed of Composed of a flexible composite thermoelectric module with graphene, the thermoelectric module has a ZT value of 1.8-2.2, and each module contains 100 pairs of thermoelectric arms. The upper and lower surfaces of the thermoelectric arms are respectively bonded to a copper substrate and... The ceramic insulation layer, the array of flexible three-dimensional TEG arrays, is fixed to the outer wall of the ORC condenser by spiral winding and axial splicing, with 20-25 arrays arranged per meter of tube wall. It is a flexible composite thermoelectric module with graphene, and the modules are connected in a 10-series-5-parallel configuration.

5. The geothermal well and thermal energy utilization system integrated with a thermoelectric function according to claim 1, characterized in that, The phase change energy storage unit includes a stainless steel energy storage tank and a serpentine heat exchange tube. The eutectic salt has a melting point of 60-65℃. When the ORC output power decreases by more than 10%, the energy storage unit releases heat to heat water to 80-90℃, driving a small screw expander to replenish energy.

6. A geothermal well and thermal energy utilization system integrating thermoelectric power generation function according to claim 1, characterized in that, The ultrasonic vibration component uses piezoelectric ceramic ultrasonic transducers, with one transducer arranged every 10m of pipe. The pulsed electric field component includes titanium alloy electrodes and a pulsed power supply. The electrode spacing is 50-80mm. The ceramic-based composite coating is... The coating is prepared by atmospheric plasma spraying. The intelligent anti-scaling and anti-corrosion module also includes a zinc alloy sacrificial anode, with one set arranged every 500m of well shaft. A polytetrafluoroethylene insulating gasket is provided between the anode and the well shaft to reduce the consumption rate.

7. A geothermal well and thermal energy utilization system integrating thermoelectric power generation function according to claim 1, characterized in that, The sensor group of the AI ​​intelligent control module includes a temperature sensor, a pressure sensor, and an electromagnetic flowmeter. The temperature sensor is arranged every 50m in the main well and every 30m in the branch well. The pressure sensor is arranged at the wellhead, bottom of the main well, and inlet and outlet of the heat exchanger. The DRL algorithm unit constructs a neural network model using TensorFlow. The input layer contains 15 parameters, the hidden layer has 3 layers, and the output layer contains 8 control commands.

8. The geothermal well and thermal energy utilization system integrated with a thermoelectric function according to claim 1, characterized in that, The shell-and-tube waste heat exchanger is supplied with a pre-reinjection fluid at 25-35°C on the shell side and with domestic hot water at 15°C on the tube side. This allows for adjustments based on domestic hot water demand. When the electric three-way valve switches to the preheating shallow fluid mode, the shallow fluid is preheated from 60°C to 70-80°C. The inner wall of the porous medium reinjection well is lined with alumina porous ceramic pipes. The mass ratio of the quartz sand and montmorillonite mixed medium is 7:3, and the filling thickness is 50mm.

9. The geothermal well and thermal energy utilization system integrated with a thermoelectric function according to claim 1, characterized in that, The DRL algorithm unit in the AI ​​intelligent control module aims at multi-objective optimization, and its optimization objective function is: in, Let be the system state vector. For control vectors, The total power generation efficiency of the system. For system energy loss, Penalty for scaling / corrosion. , , Let be the weighting coefficient, satisfying ; The reward function of the DRL algorithm is: in, Let be the reward value at time t. Let be the change in total power generation efficiency at time t. Let be the change in system energy loss at time t. Let t be the change in scaling / corrosion penalty at time t. , , It is a positive coefficient used to adjust the relative importance of each objective; During each control cycle, the system updates the control variables according to the following strategy: wherein, is the t+1 period optimal control vector, is the maximization operator, is the optimal action value function, are neural network parameters and can be updated by gradient descent. where, is the algorithm learning rate, is the gradient of the objective function with respect to the parameters.

10. The geothermal well and thermal energy utilization system integrated with a thermoelectric function according to claim 9, characterized in that, When the ultrasonic thickness gauge detects that the scale thickness on the pipe wall is >0.3mm, the ultrasonic vibration component and the pulse electric field component work together to remove the scale. The AI ​​intelligent control module can automatically increase the ultrasonic transducer power by 20%-30% and extend the pulse electric field duration. The control law is as follows: in, The ultrasonic transducer power for period t+1. The current power of the ultrasonic transducer during period t. Let t be the scale thickness at time t, 0.25 be the maximum power boost coefficient, and 0.3 be the scale thickness warning threshold.

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