A downhole geothermal energy thermoelectric power generation system

Abstract

This application provides a downhole geothermal energy photovoltaic power generation system, comprising: a conversion component including symmetrically arranged upper and lower pipe joints; the upper and lower pipe joints are respectively combined with the original geothermal power generation system casing structure to form an inflow channel and an outflow channel; a casing assembly connected between the upper and lower pipe joints; and a photovoltaic power generation system including multiple photovoltaic power generation modules built into the casing assembly; wherein each photovoltaic power generation module includes: multiple heat sinks and multiple layers of thermoelectric power generation modules, with one layer of thermoelectric power generation modules stacked between every two adjacent heat sinks; odd-numbered heat sinks are connected to the inflow channel and in contact with the cold end of each layer of thermoelectric power generation modules, while even-numbered heat sinks are connected to the outflow channel and in contact with the hot end of each layer of thermoelectric power generation modules. The system provided by this invention at least solves the problems of large modification requirements, high construction costs, large heat and electricity transmission losses, and low power generation efficiency in traditional geothermal power generation.

Description

Technical Field

[0001] This application relates to the field of geothermal in-situ power generation technology, and in particular to an underground geothermal photovoltaic power generation system. Background Technology

[0002] With the advancement of global industrialization, energy demand is increasing daily. Traditional fossil fuels emit large amounts of greenhouse gases during use, exacerbating global warming. Geothermal energy, as a clean energy source that is abundant, pollution-free, and renewable, has attracted widespread attention. Its heat primarily originates from molten magma and the decay of radioactive materials within the Earth, where internal temperatures can reach approximately 7000℃. Therefore, geothermal power generation has become one of the important development directions in the field of clean energy.

[0003] Currently, geothermal power generation typically involves directly extracting underground hot water to the surface, converting the heat energy into mechanical energy and generating electricity through a thermal power plant, and then reinjecting the cooled water back underground. This method suffers from problems such as difficulty in reinjection, potential groundwater pollution, and damage to the underground ecosystem. Furthermore, significant heat loss occurs during heat transfer, resulting in low power generation efficiency. In addition, underground equipment (such as submersible pumps and sensors) still relies on an electricity supply. If geothermal energy were transported to the surface for power generation and then supplied to the underground, not only would energy losses occur during the multiple conversions and transmissions of heat and electricity, but the complexity and construction cost of the power transmission system would also increase. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide an underground geothermal energy photovoltaic power generation system to solve the problems of large-scale modification, high construction costs, large heat and electricity transmission losses, and low power generation efficiency in traditional geothermal power generation.

[0005] A ground-mounted geothermal photovoltaic power generation system, the system comprising: A conversion component is used to connect to the original geothermal power generation system casing structure. The conversion component includes an upper pipe joint and a lower pipe joint arranged symmetrically. The upper pipe joint and the lower pipe joint are respectively combined with the original geothermal power generation system casing structure to form an inflow channel and an outflow channel. A sleeve assembly is connected between the upper pipe joint and the lower pipe joint; A thermal photovoltaic power generation system includes multiple thermal photovoltaic power generation modules, which are built into the bushing assembly; Each of the aforementioned thermal photovoltaic power generation modules includes: Multiple heat sinks and multiple layers of thermoelectric generator modules are provided, with one layer of thermoelectric generator modules stacked between every two adjacent heat sinks; an odd number of heat sinks are connected to the inflow channel and contact the cold end of each layer of thermoelectric generator modules, while an even number of heat sinks are connected to the outflow channel and contact the hot end of each layer of thermoelectric generator modules; as defined such that: The cold working fluid flows from the upper section of the casing structure of the original geothermal power generation system into the inlet channel of the upper pipe joint, enters the odd number of heat sinks through the inlet channel, then flows to the inlet channel of the lower pipe joint, and finally flows to the lower section of the casing structure of the original geothermal power generation system; the cold working fluid absorbs the geothermal energy transferred downhole and converts it into a thermal working fluid. The working fluid flows from the lower section of the original geothermal power generation system casing structure back to the outlet channel of the lower pipe joint, enters the even-numbered heat sink through the outlet channel, then flows to the outlet channel of the upper pipe joint, and finally flows back to the upper section of the original geothermal power generation system casing structure. Therefore, a temperature difference is formed between the cold end of each layer of thermoelectric power generation module that contacts the odd number of heat sinks and the hot end that contacts the even number of heat sinks, thereby realizing thermoelectric conversion in situ.

[0006] As one preferred embodiment, the casing structure of the original geothermal power generation system includes a first-layer casing, a second-layer casing, and a third-layer casing arranged from the outside in; the upper pipe joint and the lower pipe joint correspondingly include an outer casing, a middle casing, and an inner casing arranged from the outside in; wherein... The outer wall surface of the outer sleeve is provided with a first external thread and a second external thread, the second external thread being screwed to the first sleeve, and the first external thread being screwed to the sleeve assembly; the outer wall surface of the middle sleeve is provided with an intermediate thread that is screwed to the second sleeve, and the inner wall surface of the inner sleeve is provided with an internal thread that is screwed to the third sleeve.

[0007] As one of the preferred embodiments, the intermediate sleeve and the inner sleeve are stacked together, and a heat-insulating air gap is provided inside the wall of the intermediate sleeve.

[0008] As one of the preferred embodiments, a seat is provided on the side where the upper pipe joint and the lower pipe joint are connected to the sleeve assembly, and the outer sleeve, the middle sleeve and the inner sleeve are vertically arranged on the seat. The inflow channel is formed by the outer sleeve, the middle sleeve, and the seat, and the outflow channel is formed by the lumen of the inner sleeve and the seat. The base body has multiple cold end diversion holes at the position corresponding to the inflow channel, and multiple hot end diversion holes at the position corresponding to the outflow channel; The cold end diversion hole connects the inlet channel to the corresponding heat sink, and the hot end diversion hole connects the outlet channel to the corresponding heat sink.

[0009] As one preferred embodiment, each of the thermal photovoltaic power generation modules further includes: The flow channel connectors are provided at opposite ends of each heat sink. The flow channel connectors connect the corresponding heat sink to the inflow channel or the outflow channel through connecting pipes, and connect the heat sinks of two adjacent thermal photovoltaic power generation modules one by one. Two cover plates are disposed on the outer wall surfaces of the two heat sinks located on either side of the edge; At least one screw, each screw being fixed to two cover plates, presses and fixes multiple heat sinks and multiple layers of thermoelectric modules between the two cover plates.

[0010] As one of the preferred solutions, the positions of the two flow channel joints on the same heat sink are staggered, and the positions of the multiple heat sinks on the same end are staggered.

[0011] As one of the preferred options, each of the heat sinks has an organ pipe structure.

[0012] As one preferred embodiment, the sleeve assembly includes: The protective sleeve is connected to the upper pipe joint and the lower pipe joint at both ends by flanges respectively; the protective sleeve is also connected to the cover plate of each of the thermal photovoltaic power generation modules by multiple fastening screws; A connecting sleeve is fitted onto the outside of the protective sleeve, and both ends are screwed to the second external threads of the upper pipe joint and the lower pipe joint, respectively.

[0013] As a preferred embodiment, a rubber ring is provided between the protective sleeve and the connecting sleeve.

[0014] As one of the preferred options, the three-layer casing is also used to connect with surface equipment to transport the heat transfer medium after heat transfer to the thermoelectric power generation module to the surface, so as to utilize the waste heat of the heat transfer medium.

[0015] Compared with the prior art, this application has the following advantages: The system provided in this application embodiment can be directly installed in a geothermal well, completely isolated from the underground heat storage. Heat is transferred solely through thermal conduction, achieving in-situ thermoelectric conversion without extracting underground hot water. This directly powers underground equipment or supplies power to the surface for grid connection or other applications. This solution requires minimal modification to traditional geothermal wells, effectively reducing heat and electrical energy losses during transmission, improving overall system power generation efficiency, simplifying underground power line layout, and lowering construction and operating costs. Furthermore, this solution employs a fully closed-loop heat extraction cycle, truly achieving "heat extraction without water extraction," fundamentally avoiding the consumption, pollution, and thermal pollution of groundwater resources, thus protecting the underground ecological environment. Attached Figure Description

[0016] To more clearly illustrate the technical solution of this application, the drawings used in the description of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a front sectional view of a downhole geothermal photovoltaic power generation system according to an embodiment of this application; Figure 2 This is an axonometric sectional view of the conversion component according to an embodiment of this application; Figure 3 This is an exploded perspective view of a photovoltaic power generation system according to an embodiment of this application; Figure 4 This is an assembly schematic diagram of an embodiment of the underground geothermal photovoltaic power generation system described in this application; Figure 5 This is a schematic diagram of the working principle of an underground geothermal energy photovoltaic power generation system according to an embodiment of this application.

[0018] Explanation of reference numerals in the attached figures: 1. Conversion component; 1-1. First external thread; 1-2. Second external thread; 1-3. Cold end diversion hole; 1-4. Intermediate thread; 1-5. Insulation air gap; 1-6. Hot end diversion hole; 1-7. Internal thread; 2. Thermovolt-electric power generation system; 2-1. Flow channel connector; 2-2. Cover plate; 2-3. Heat sink; 2-4. Thermovolt-electric module; 2-5. Fastening screw; 3. Sleeve assembly; 3-1. Protective sleeve; 3-2. Connecting sleeve; 3-3. Flange; 3-4. Support; 3-5. Rubber ring; 3-6. Screw hole. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] It should be noted that extracting heat without extracting water is considered the best solution to the traditional geothermal extraction and irrigation method. This model uses in-situ heat exchange to directly install a thermoelectric conversion device in the geothermal well, extracting only the geothermal energy without extracting underground fluids. This avoids the problems of reinjection difficulties, groundwater pollution, and ecological damage that exist in the traditional geothermal extraction and irrigation method, and realizes in-situ heat energy conversion and direct output of electricity.

[0021] Under current technological conditions, although the "heat extraction without water extraction" geothermal utilization concept has significant advantages, there is still a lack of in-situ power generation systems truly adapted to the spatial characteristics and operating environment of geothermal wells. This makes direct thermoelectric conversion downhole difficult to achieve, thus limiting the engineering application of this concept. Therefore, developing an in-situ power generation system adapted to the spatial characteristics of geothermal wells to achieve in-situ geothermal power generation to supply power to downhole electrical equipment, while simultaneously transmitting power to the surface for other power supply equipment or into the power grid, will not only help promote the engineering realization of the "heat extraction without water extraction" model but also improve geothermal energy utilization efficiency, reduce environmental risks and system complexity. This has significant technical and economic implications for the efficient, safe, and sustainable development of geothermal resources.

[0022] Among related technologies, one proposed in-situ geothermal power generation system utilizes heat pipes to transport geothermal energy upwards. During this process, a thermoelectric generator located at the lower section of the heat pipe directly converts geothermal energy into electrical energy. Conversely, the vaporized circulating working fluid drives a magnetically levitated power generation device in the middle of the heat pipe to generate electricity. While this system also utilizes in-situ geothermal power generation, it requires significant modifications to the original geothermal power generation method, presenting high engineering challenges. Furthermore, extracting heat from deep geothermal reservoirs using heat pipes is difficult, as is replacing or repairing the heat pipes. Another proposed method and system for in-situ geothermal power generation associated with depleted shale reservoirs involves establishing a closed-loop thermal recovery system by modifying two depleted production wells in a high-temperature shale reservoir, effectively reducing well construction costs for geothermal development. However, this system uses an ORC (Organic Regeneration and Control) system located on the surface, making heat and energy losses during transportation unavoidable. Another method has been proposed for multiple in-situ power generation based on deep geothermal resources from abandoned coal mines. This method involves pre-burying circulation pipelines in the goaf, injecting organic working fluid into the pipelines, and generating steam after heating to drive an in-situ generator. However, this method suffers from the problem of easy damage and difficulty in replacing moving components such as the ORC system located underground.

[0023] It is evident that while existing technologies have explored pathways for in-situ geothermal power generation to varying degrees, they still suffer from problems such as complex structures, difficult maintenance, high energy loss, insufficient environmental adaptability, and high difficulty in engineering promotion. A truly suitable in-situ power generation system that is well-suited to the spatial characteristics of geothermal wells, has a simple and reliable structure, and is easy to implement in engineering has not yet been formed.

[0024] In view of this, the present invention aims to develop an underground in-situ thermoelectric conversion system that is completely isolated from the geothermal storage, transferring heat only through conduction. The system achieves thermoelectric conversion in situ, realizing a "heat extraction without water extraction" geothermal utilization method. This method not only reduces the disturbance risk to the groundwater system caused by traditional extraction-injection geothermal utilization methods, but also improves the comprehensive utilization efficiency of geothermal energy, simplifies the system structure, and enhances the system's operational stability and maintainability. It can become a potentially important research direction in the field of geothermal power generation.

[0025] To achieve this objective, the present invention proposes a specific implementation method in its practical application. (Refer to...) Figure 1 As shown, Figure 1 This is a front cross-sectional view of the downhole geothermal photovoltaic power generation system shown in this invention. Figure 1 As shown, this invention provides a downhole geothermal energy photovoltaic power generation system. The system includes: a conversion component 1 for connecting to the casing structure of the original geothermal power generation system; the conversion component 1 includes symmetrically arranged upper and lower pipe joints; the upper and lower pipe joints are combined with the casing structure of the original geothermal power generation system to form an inflow channel and an outflow channel, respectively; a casing assembly 3 connected between the upper and lower pipe joints; a photovoltaic power generation system 2 including multiple photovoltaic power generation modules, which are built into the casing assembly 3; wherein each photovoltaic power generation module includes: multiple heat sinks 2-3 and multiple layers of thermoelectric power generation modules 2-4, with one layer of thermoelectric power generation modules 2-4 stacked between every two adjacent heat sinks 2-3; odd-numbered heat sinks 2-3 are connected to the inflow channel and in contact with the cold end of each layer of thermoelectric power generation modules 2-4, and even-numbered heat sinks 2-3 are connected to the outflow channel and in contact with the hot end of each layer of thermoelectric power generation modules 2-4; as defined such that: The cold working fluid flows from the upper section of the original geothermal power generation system casing structure into the inlet channel of the upper pipe joint, enters the odd-numbered heat sink 2-3 through the inlet channel, then flows into the inlet channel of the lower pipe joint, and finally flows to the lower section of the original geothermal power generation system casing structure; the cold working fluid absorbs the geothermal energy transferred downhole and converts it into a hot working fluid; the hot working fluid flows from the lower section of the original geothermal power generation system casing structure back to the outlet channel of the lower pipe joint, enters the even-numbered heat sink 2-3 through the outlet channel, then flows into the outlet channel of the upper pipe joint, and finally flows back to the upper section of the original geothermal power generation system casing structure; therefore, a temperature difference is formed between the cold end of each layer of thermoelectric power generation module 2-4 that contacts the odd-numbered heat sink 2-3 and the hot end that contacts the even-numbered heat sink 2-3, thereby realizing in-situ thermoelectric conversion.

[0026] Specifically, in this embodiment of the invention, a prefabricated downhole circulation system is first formed on the basis of the original geothermal power generation system casing structure. The conversion component 1 is connected to the original geothermal power generation system casing structure through upper and lower pipe joints, forming an inflow channel and an outflow channel. Since it does not change the main structure of the original well or carry out large-scale modification of the wellbore structure, it is compatible with existing geothermal wells, has strong engineering adaptability, and low modification cost.

[0027] In some embodiments, the upper and lower pipe joints have the same structure and are arranged symmetrically with respect to the radial direction. The structure of the upper pipe joint will be fully described below, and the structure of the upper pipe joint can be referred to accordingly, but the vertical direction can be understood by referring to it in reverse. The upper pipe joint can be at least a double-layer coaxial nested structure, forming two physically isolated inlet and outlet channels. For example, the annular gap formed between the two layers is the inlet channel, and the inner layer surrounding the cavity serves as the outlet channel. Preferably, the upper pipe joint is a three-layer coaxial nested structure, adapted to the three-layer casing structure of the original geothermal power generation system.

[0028] Then, the upper and lower pipe joints are connected by the casing assembly 3, which is located between the upper and lower pipe joints. The thermal photovoltaic power generation system 2 is built into the casing assembly 3, thereby protecting the thermal photovoltaic power generation system 2. At the same time, it serves as a pressure-bearing structure, supporting the thermal photovoltaic power generation system 2 at the bottom of the well. In some embodiments, the casing assembly 3 may include a single-layer pressure-bearing casing, a double-layer insulated casing, or a two / multi-layer functional combination casing, etc.

[0029] Taking the direction from the surface to the bottom of the well as the reference, the lower end of the upper section of the original geothermal power generation system casing structure is connected to the upper pipe joint, the upper pipe joint is connected to the upper end of the casing assembly 3, the lower end of the casing assembly 3 is connected to the lower pipe joint, and the lower end of the lower pipe joint continues to be connected to the upper end of the lower section of the original geothermal power generation system casing structure. Along the original length direction of the geothermal well, an in-well casing adapter embedded structure is formed. Multiple thermal photovoltaic power generation modules are distributed from top to bottom in the cavity of the casing assembly 3, and the heat sinks 2-3 of multiple thermal photovoltaic power generation modules are connected sequentially through pipes. Thermoelectric power generation modules 2-4 are connected in multiple stages through wires (series output / parallel output / series-parallel hybrid connection).

[0030] like Figure 5The diagram illustrates the working principle of a downhole geothermal photovoltaic (TGV) power generation system, where arrows indicate the direction of heat flow. Taking a single TGV module as an example, the TGV module includes multiple heat sinks 2-3 and multiple layers of thermoelectric generator modules 2-4. The heat sinks 2-3 and thermoelectric generator modules 2-4 are arranged radially, with one heat sink 2-3 and one thermoelectric generator module 2-4 alternately overlapping radially, but the outermost layer is always a heat sink 2-3. This ensures that the hot and cold ends of each layer of thermoelectric generator modules 2-4 can contact two heat sinks 2-3 with opposing hot and cold working fluids, thereby establishing a temperature difference. In the multiple spaced TGV modules, the upper end of the heat sink 2-3 of the uppermost TGV module is connected to the upper pipe joint, and the lower end of the heat sink 2-3 is connected to the upper end of the heat sink 2-3 of the next TGV module, until the lower end of the heat sink 2-3 of the lowermost TGV module is connected to the lower pipe joint.

[0031] The odd- and even-numbered heat sinks 2-3 are alternately connected to the flow channels of conversion component 1 through their embedded flow channels. The odd-numbered heat sinks 2-3 are connected to the inlet channel, where a cold working fluid flows from the upper pipe joint to the lower pipe joint, supplying cooling to the cold end of the thermoelectric generator module 2-4 during this flow. The even-numbered heat sinks 2-3 are connected to the outlet channel, where a hot working fluid (e.g., steam) formed after the cold working fluid absorbs geothermal energy at the bottom of the well flows. This hot working fluid flows from the lower pipe joint to the upper pipe joint, supplying heat to the hot end of the thermoelectric generator module 2-4. Since the thermoelectric power generation module 2-4 is sandwiched between two heat sinks 2-3 with different temperatures of cold and hot working fluids, the cold working fluid flows downward and the hot working fluid flows upward. Therefore, the cold and hot working fluids form countercurrent heat exchange at the opposite end faces of the thermoelectric power generation module 2-4, thereby establishing a temperature difference between the cold and hot ends of the thermoelectric power generation module 2-4. The temperature difference formed at the cold and hot ends drives the thermoelectric power generation system 2 to generate electricity, thereby realizing in-situ power supply downhole and reducing energy loss in multi-stage conversion.

[0032] Therefore, the system adopts a closed-loop design, eliminating the need for groundwater extraction and reinjection. It extracts heat solely through thermal conduction, truly achieving "heat extraction without water extraction" and avoiding various problems associated with traditional methods. The system can operate independently or work in conjunction with surface systems, significantly reducing multiple energy losses during heat extraction and electrical transmission. This improves overall energy efficiency, simplifies the complexity of underground power supply lines, and helps reduce construction and maintenance costs.

[0033] In some embodiments, the heat sink 2-3 may be an aluminum alloy plate, copper plate, graphite plate, or metal plate, etc., but it is internally provided with a cavity as a flow channel for the heat sink 2-3 to communicate with the flow channel of the conversion component 1, allowing the cold or hot working fluid to flow up and down. This embodiment does not specifically limit the shape, size, or number of the flow channels built into the heat sink 2-3 structure. In some embodiments, the thermoelectric power generation module 2-4 between the heat sink 2-3 with cold working fluid and the heat sink 2-3 with hot working fluid can also be formed by combining multiple thermoelectric power generation units.

[0034] As a further explanation of this embodiment, one thermoelectric power generation module corresponds to one segment of the bushing assembly 3, and multiple thermoelectric power generation modules are arranged in multiple segments of the bushing assembly 3. Therefore, the thermoelectric power generation system 2 adopts a modular design, and its thermoelectric power generation modules 2-4 can be flexibly added or removed according to power generation needs. Furthermore, when a single thermoelectric unit fails, the system can still maintain some power generation functions, improving reliability. Of course, in practical applications, the number of thermoelectric power generation modules contained in each segment can also be flexibly adjusted according to power generation needs, that is, multiple thermoelectric power generation modules 2-4 can also be arranged in the same segment of the bushing assembly 3.

[0035] It is worth mentioning that the operating mode of the cold working fluid absorbing geothermal energy can be controlled according to the actual conditions of the geothermal well, such as well depth, formation thermal reservoir type, wellbore heat flux density, flow rate of the cold working fluid, and heat transfer coefficient. For example, the cold working fluid can absorb geothermal energy from the well wall along the way during its downward flow, gradually increasing in temperature, and finally becoming a hot working fluid near the lower pipe joint. Alternatively, the cold working fluid may remain at a relatively low temperature during its downward flow and reach the lower section of the original geothermal power generation system casing structure via the lower pipe joint, where it efficiently absorbs heat in the high-temperature zone at the bottom of the well, forming a high-temperature hot working fluid before rising and flowing back as a whole.

[0036] This system can select either a flow-through heat absorption mode or a bottom-concentrated heat absorption mode based on the temperature distribution characteristics of the geothermal well, both of which can achieve in-situ thermoelectric conversion. Preferably, the temperature at the bottom of the well is significantly higher than that in the upper section. Cold working fluid is continuously transported to the bottom of the well, where it absorbs heat in the high-temperature zone to form a high-temperature working fluid before rising. Simultaneously, because the heat sink 2-3, which is in contact with the cold end of the thermoelectric power generation module 2-4, circulates a consistently low-temperature working fluid, while the heat sink 2-3, which is in contact with the hot end of the thermoelectric power generation module 2-4, circulates high-temperature hot steam, a larger temperature difference can be formed between the cold and hot ends of the thermoelectric power generation module 2-4. This improves the thermoelectric conversion efficiency and facilitates natural circulation, reducing fluid-driven energy consumption.

[0037] It is also worth mentioning that by alternately connecting the sequentially arranged heat sinks 2-3 to the inflow and outflow channels respectively to receive hot and cold working fluids, and enclosing the thermoelectric power generation module 2-4 between the two alternating hot and cold heat sinks 2-3, a counter-current heat exchange system can be constructed downhole, forming a stable temperature difference field with opposing hot and cold elements at both ends of each thermoelectric module. Accordingly, in some embodiments, the cold working fluid can also flow downwards along the even-numbered heat sinks 2-3, while the hot working fluid rises upwards along the odd-numbered heat sinks 2-3. Correspondingly, the odd-numbered heat sinks 2-3 can be connected to the outflow channel, and the even-numbered heat sinks 2-3 can be connected to the inflow channel. In this way, the counter-current heat exchange structure makes the temperature difference of the thermoelectric power generation module 2-4 larger, and the thermoelectric module is directly attached between the two hot and cold heat sinks 2-3, resulting in low contact thermal resistance and a short heat conduction path.

[0038] In some embodiments, the total number of heat sinks 2-3 can be odd or even. This embodiment does not limit this. Correspondingly, the number of thermoelectric power generation modules 2-4 can also be odd or even, and one less than the total number of heat sinks 2-3.

[0039] In summary, this invention, while maintaining the basic structure of the original geothermal power generation system, modifies the well structure of traditional geothermal power generation to integrate a modular thermal photovoltaic (TPV) power generation system 2 underground, achieving in-situ conversion of geothermal energy. The generated electricity can directly power underground equipment or be transmitted to the surface power grid. The in-situ geothermal TPV power generation system mainly consists of an upper and lower pipe joint, the TPV power generation system 2, and a casing assembly 3. This system connects to the three-layer casing of the original geothermal power generation system by converting the upper and lower pipe joints, and is connected to the TPV power generation system 2. The casing assembly 3 secures and protects the TPV power generation system 2. During operation, the circulating working fluid flows into the upper pipe joint through the original geothermal well pipes, and then is diverted into odd-numbered heat sinks 2-3, supplying heat to the cold end of the TPV power generation system 2. Simultaneously, the circulating working fluid heated at the bottom of the geothermal well is diverted through the lower pipe joint into even-numbered heat sinks 2-3, supplying heat to the hot end of the TPV power generation system 2. The temperature difference between the cold and hot ends of each thermoelectric power generation module 2-4 in the thermoelectric power generation system 2 drives the thermoelectric power generation system 2 to generate electricity, realizing in-situ thermoelectric conversion of geothermal energy in a single well using thermoelectric power generation technology. After power generation in the well, the hot end fluid still has a high temperature and can be recovered and transported to the surface for continued use by conventional power generation systems.

[0040] Therefore, the system provided in this embodiment of the invention can be directly installed in a geothermal well, completely isolated from the underground heat storage. Heat is transferred solely through thermal conduction, achieving in-situ thermoelectric conversion without extracting underground hot water. This directly powers underground electrical equipment or supplies power to the surface for grid connection or other electrical equipment. This solution requires minimal modification to traditional geothermal wells, effectively reducing heat and electrical energy losses during transmission, improving overall system power generation efficiency, simplifying underground power supply line layout, and reducing construction and operating costs. Furthermore, this solution employs a fully closed-loop heat extraction cycle, truly achieving "heat extraction without water extraction," fundamentally avoiding the consumption, pollution, and thermal pollution of groundwater resources, and protecting the underground ecological environment.

[0041] like Figure 2 As shown, Figure 2 This is an axial sectional view of the conversion component 1. As a further explanation of this embodiment, the in-situ geothermal power generation system casing structure includes a first-layer casing, a second-layer casing, and a third-layer casing arranged from the outside in; the upper pipe joint and lower pipe joint correspondingly include an outer casing, a middle casing, and an inner casing arranged from the outside in; wherein, the outer wall surface of the outer casing is provided with a first external thread 1-1 and a first external thread 1-2, the first external thread 1-2 being screwed to the first-layer casing, and the first external thread 1-1 being screwed to the casing component 3; the outer wall surface of the middle casing is provided with a middle thread 1-4 screwed to the second-layer casing, and the inner wall surface of the inner casing is provided with an internal thread 1-7 screwed to the third-layer casing. In this embodiment, the casing structure of the original geothermal power generation system is a mainstream three-layer casing structure. This embodiment is specifically designed to retain the original structure of traditional geothermal wells to minimize the scope of modification, save modification costs, and preserve the integrity of the original well. The upper pipe joint corresponds to the original well's three-layer design with coaxially nested inner, middle, and outer casings, forming an outer low, middle high, and inner low profile. All three casings are central pipe structures, with the inner casing's lumen being the outflow and the annular gap between the middle and outer layers being the inflow. The outer wall surfaces of the upper and lower sections of the outer casing are respectively provided with first external threads 1-1 and 1-2. The upper pipe joint is connected to the connecting casing 3-2 of the casing assembly 3 of the thermal power generation system 2 through its lower first external thread 1-1, and to the first layer of casing of the original geothermal well through its upper first external thread 1-2, so as to assemble the entire system onto the slightly modified original well pipeline. The outer wall of the upper section of the intermediate casing is provided with intermediate threads 1-4 that are screwed to the second-layer casing, preserving the heat insulation air gap formed by the second-layer casing of the original geothermal well and maintaining the heat insulation effect of the entire power generation system. The third-layer casing of the original geothermal well is connected to the inner casing through internal threads 1-7.

[0042] Therefore, the design of the conversion component 1 in this embodiment, while basically maintaining the original structure of the traditional geothermal well, realizes the coaxial embedded installation and integration of the power generation casing component 3 of the in-situ thermal photovoltaic power generation system 2, and ensures the physical isolation of the inflow channel and the outflow channel, realizes counter-current heat exchange and system disassembly and maintenance, thereby taking into account structural strength, sealing reliability and engineering feasibility.

[0043] Preferably, the intermediate casing and the inner casing are stacked together, and the inner wall of the intermediate casing has an insulating air gap 1-5. In this embodiment, the intermediate casing and the inner casing can be a single piece, but they are arranged with the outer side higher than the inner side. Threads are provided on the upper middle section of the outer wall and the upper section of the inner wall, thus dividing the casing into an outer intermediate casing and an inner inner casing, maintaining the utilization rate of the wellbore space. Therefore, within the limited space of the wellbore, the built-in insulating air gap 1-5 effectively suppresses radial heat conduction between cold and hot fluids in the inflow and outflow channels, thereby ensuring the stable establishment of the temperature difference required by the thermal photovoltaic power generation system 2 and reducing the overall heat loss of the system.

[0044] Preferably, the position of the thermal insulation gap 1-5 corresponds to the position of the inner sleeve, that is, the axial length of the thermal insulation gap 1-5 can be greater than, equal to, or slightly less than the length of the inner sleeve, and the radial projection of the thermal insulation gap 1-5 overlaps or intersects with the radial projection of the inner sleeve. For example, the lower end of the thermal insulation gap 1-5 is flush with or slightly higher than the lower end of the inner sleeve, while the upper end of the thermal insulation gap 1-5 is flush with or slightly lower than the upper end of the inner sleeve. Therefore, the thermal insulation coverage of the thermal insulation gap 1-5 matches the effective heat exchange section of the hot and cold flow channels, so that the shortest heat conduction path between the hot and cold fluids is cut off by the gap, enhancing the suppression of radial heat conduction between the hot and cold fluids in the inlet and outlet channels, and improving the stable temperature difference and power generation efficiency at both ends of the thermoelectric power generation module 2-4.

[0045] Among them, the inner sleeve is covered at any position in the radial direction of the heat insulation air gap 1-5, that is, the heat insulation air gap 1-5 surrounds the circumference, and uniform heat insulation is achieved by full circumference coverage.

[0046] Furthermore, a seat is provided on the side where the upper and lower pipe joints are connected to the sleeve assembly 3. The outer sleeve, the middle sleeve, and the inner sleeve are vertically arranged on the seat. An inflow channel is formed by the outer sleeve, the middle sleeve, and the seat, and an outflow channel is formed by the cavity of the inner sleeve and the seat. Multiple cold end diversion holes 1-3 are opened at the position corresponding to the inflow channel on the seat, and multiple hot end diversion holes 1-6 are opened at the position corresponding to the outflow channel. The cold end diversion holes 1-3 connect the inflow channel and the corresponding heat sink 2-3, and the hot end diversion holes 1-6 connect the outflow channel and the corresponding heat sink 2-3.

[0047] In this embodiment, the base and the three-layer sleeve can be integrally formed by draft molding, making the three-layer sleeve coaxial. The cold working fluid flows out from the annular gap formed by the outer sleeve and the middle sleeve, and flows from several cold-end diversion holes 1-3 located in the annular gap of the base to the flow channels of several odd-numbered heat sinks 2-3. Similarly, the hot working fluid flows from the flow channels of several even-numbered heat sinks 2-3 to several hot-end diversion holes 1-6 located in the tubular cavity of the base, and finally flows out from the tubular cavity of the inner sleeve. Therefore, in the three-layer coaxial counter-flow structure, uniform flow is achieved through the base, so that the cold and hot fluids are evenly distributed and enter the multiple corresponding heat sinks 2-3, thereby forming a multi-stage counter-flow thermoelectric power generation system in space.

[0048] In the specific implementation process, the cold working fluid flows from the first layer of the original geothermal power generation system into the upper pipe joint, and then enters the photovoltaic power generation system 2 through its cold end diversion hole 1-3. After the photovoltaic power generation system 2 completes heat exchange, the cold working fluid returns to the outer layer of the lower pipe joint through the cold end diversion hole 1-3, then flows back to the first layer of the casing, and is transported to the bottom of the geothermal well for heating. The fully heated working fluid rises from the bottom of the well, enters the lower pipe joint from the third layer of the original geothermal well, and enters the photovoltaic power generation system 2 through the hot end diversion hole 1-6. After the photovoltaic power generation system 2 releases heat, the hot working fluid returns to the inner layer of the upper pipe joint through the hot end diversion hole 1-6, then flows back to the third layer of the casing, and is finally transported to the surface for power generation.

[0049] like Figure 3 As shown, Figure 3 This is an exploded perspective view of a thermoelectric power generation module. This embodiment is used to illustrate the thermoelectric power generation module. Each thermoelectric power generation module further includes: flow channel connectors 2-1 disposed at opposite ends of each heat sink 2-3, the flow channel connectors 2-1 connecting the corresponding heat sink 2-3 to the inflow channel or outflow channel respectively through connecting pipes, and connecting the heat sinks 2-3 of two adjacent thermoelectric power generation modules one-to-one; two cover plates 2-2 disposed on the outer wall surfaces of the two heat sinks 2-3 located on both sides of the edge; at least one screw, each screw fixed on the two cover plates 2-2, pressing and fixing multiple heat sinks 2-3 and multi-layer thermoelectric power generation modules 2-4 between the two cover plates 2-2.

[0050] In this embodiment, the thermoelectric power generation module is connected to the cold end diversion hole 1-3 and the hot end diversion hole 1-6 of the base of the conversion component 1 through multiple flow channel joints 2-1. The other end of each flow channel joint 2-1 is connected to the heat sink 2-3. The heat sink 2-3 adopts a harmonica tube-type flow channel structure to uniformly distribute the working fluid and improve heat transfer efficiency. Between every two adjacent heat sinks 2-3, 3-4 thermoelectric power generation modules 2-4 can be set. When a temperature difference is formed at both ends of the thermoelectric power generation module 2-4, the thermoelectric power generation module 2-4 can generate electricity. For example, a single thermoelectric power generation module can be composed of nine heat sinks 2-3 and eight layers of thermoelectric power generation modules 2-4 stacked alternately. The outermost two ends of the module are equipped with cover plates 2-2, and the heat sinks 2-3, thermoelectric power generation modules 2-4 and cover plates 2-2 are pressed and fixed by multiple bolts and screws to ensure good thermal contact and mechanical stability between the components.

[0051] Therefore, the thermal photovoltaic power generation system 2 in this embodiment adopts a modular design, which enables the system to have good scalability and operational reliability. On the one hand, the number of modules can be flexibly configured according to the actual power generation demand; on the other hand, when a single module fails, the system as a whole can still maintain a portion of its power generation capacity, thereby ensuring the continuity and stability of power supply.

[0052] Preferably, the positions of the two flow channel joints 2-1 on the same heat sink 2-3 are staggered, and the positions of multiple heat sinks 2-3 at the same end are also staggered. In this embodiment, each heat sink 2-3 is provided with a flow channel joint 2-1 at both the upper and lower ends, but the two flow channel joints 2-1 at the upper and lower ends are staggered to the left and right. At the same time, all the flow channel joints 2-1 located at the upper end of the heat sink 2-3 are also arranged alternately to the left and right. Therefore, the flow path of the circulating working fluid from the flow channel joint 2-1 of each heat sink 2-3 into the harmonica-shaped cavity of the heat sink 2-3 is longer, and the overall temperature of the heat sink 2-3 is more uniform, thereby improving the temperature difference utilization efficiency between the multi-stage heat sinks 2-3 and the overall power generation performance of the system. At the same time, in the limited well diameter space, multiple flow channel joints 2-1 and the connecting pipes connecting the flow channel joints 2-1 are easy to arrange in a small space, improving space utilization and structural strength balance.

[0053] In another technical solution, the sleeve assembly 3 includes: a protective sleeve 3-1, with both ends connected to the upper pipe joint and the lower pipe joint via flanges 3-3 respectively; the protective sleeve 3-1 is also connected to the cover plate 2-2 of each thermal photovoltaic power generation module via multiple fastening screws 2-5; and a connecting sleeve 3-2, sleeved on the outside of the protective sleeve 3-1, with both ends screwed to the first external threads 1-2 of the upper and lower pipe joints respectively. Preferably, a rubber ring 3-5 is provided between the protective sleeve 3-1 and the connecting sleeve 3-2.

[0054] In this embodiment, a sleeve assembly 3 is provided on the outside of the thermal photovoltaic power generation system 2 for fixing and protecting it. Specifically, the sleeve assembly 3 includes a protective sleeve 3-1 that directly covers and fixes the thermal photovoltaic power generation system 2, and a connecting sleeve 3-2 that is sleeved outside the protective sleeve 3-1. The upper end of the protective sleeve 3-1 is provided with a flange 3-3, which is used to connect and fix it to the conversion assembly 1; the connecting sleeve 3-2 is connected to the conversion assembly 1 by a threaded connection. At the lower end of the base of the conversion assembly 1, a support member 3-4, such as a screw and a rubber pad, is provided to provide auxiliary support for the system. A rubber ring 3-5, such as an O-ring or other type of rubber ring 3-5, is fitted between the protective sleeve 3-1 and the connecting sleeve to further enhance the fixing and support effect of the system. In addition, a screw hole 3-6 is opened on the protective sleeve 3-1, and a screw passes through the screw hole 3-6 to connect to the cover plate 2-2 on the thermal photovoltaic power generation module, thereby realizing the support and fixing of the internal system.

[0055] Therefore, this invention incorporates rubber O-rings and screws at each section of the pipeline. This design provides reliable radial constraint and support for long underground pipeline sections, effectively preventing pipeline displacement or deformation, thereby significantly improving the structural stability of the system during engineering installation and long-term operation.

[0056] Furthermore, this invention employs threaded connections at all pipe joints and includes corresponding installation and positioning techniques. This connection method not only facilitates on-site assembly and alignment but also ensures high structural stability and sealing reliability at each interface under complex downhole stress environments, thereby guaranteeing the overall system's robust connection and long-term safe operation.

[0057] In summary, this invention provides a downhole geothermal photovoltaic power generation system, employing a modular structure composed of multiple photovoltaic power generation modules. In this embodiment, each power generation unit consists of four photovoltaic power generation modules, each module being connected and fixed to the corresponding screw holes 3-6 on the protective casing 3-1 via screws. Figure 4The connection relationship between the conversion component 1, the thermoelectric power generation system 2, and its casing assembly 3 is shown. The system installation process is carried out in the following steps: First, multiple thermoelectric power generation modules 2-4 are connected in series through pipes to form a basic power generation unit; then, the protective casing 3-1 is installed on the outside of the series-connected thermoelectric power generation modules 2-4 and connected and fixed; then, the conversion component 1 is connected to the three-layer casing of the traditional geothermal power generation system and connected to the protective casing 3-1 of the already assembled thermoelectric power generation system 2; subsequently, the connecting casing 3-2 of the thermoelectric power generation system 2 is connected to the conversion pipe; at the same time, on the other side, the pre-connected lower pipe joint and the three-layer casing assembly 3 are connected to the connecting casing 3-2 at the other end of the thermoelectric power generation system 2; finally, the connection between the internal thermoelectric power generation system 2 and the conversion pipe is completed through the manhole provided on the connecting casing 3-2, and then the manhole is closed, thus completing the system installation.

[0058] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0059] It should also be noted that, in this document, the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations, nor should they be construed as indicating or implying relative importance. Moreover, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device.

[0060] The above provides a detailed description of an underground geothermal photovoltaic power generation system provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand this application, and the content of this specification should not be construed as a limitation of this application. Furthermore, those skilled in the art will recognize that, based on this application, there will be various modifications in specific implementation methods and application scope. It is neither necessary nor possible to exhaustively list all implementation methods here, and any obvious variations or modifications derived therefrom are still within the protection scope of this application.

Claims

1. A geothermal photovoltaic power generation system for underground wells, characterized in that the system... include: A conversion component is used to connect to the original geothermal power generation system casing structure. The conversion component includes an upper pipe joint and a lower pipe joint arranged symmetrically. The upper pipe joint and the lower pipe joint are respectively combined with the original geothermal power generation system casing structure to form an inflow channel and an outflow channel. A sleeve assembly is connected between the upper pipe joint and the lower pipe joint; A thermal photovoltaic power generation system includes multiple thermal photovoltaic power generation modules, which are built into the bushing assembly; Each of the aforementioned thermal photovoltaic power generation modules includes: Multiple heat sinks and multiple layers of thermoelectric generator modules are provided, with one layer of thermoelectric generator modules stacked between every two adjacent heat sinks; an odd number of heat sinks are connected to the inflow channel and contact the cold end of each layer of thermoelectric generator modules, while an even number of heat sinks are connected to the outflow channel and contact the hot end of each layer of thermoelectric generator modules; as defined such that: The cold working fluid flows from the upper section of the casing structure of the original geothermal power generation system into the inlet channel of the upper pipe joint, enters the odd number of heat sinks through the inlet channel, then flows to the inlet channel of the lower pipe joint, and finally flows to the lower section of the casing structure of the original geothermal power generation system; the cold working fluid absorbs the geothermal energy transferred downhole and converts it into a thermal working fluid. The working fluid flows from the lower section of the original geothermal power generation system casing structure back to the outlet channel of the lower pipe joint, enters the even-numbered heat sink through the outlet channel, then flows to the outlet channel of the upper pipe joint, and finally flows back to the upper section of the original geothermal power generation system casing structure. Therefore, a temperature difference is formed between the cold end of each layer of thermoelectric power generation module that contacts the odd number of heat sinks and the hot end that contacts the even number of heat sinks, thereby realizing thermoelectric conversion in situ.

2. The underground geothermal photovoltaic power generation system according to claim 1, characterized in that, The original geothermal power generation system casing structure includes a first-layer casing, a second-layer casing, and a third-layer casing arranged from the outside in; the upper pipe joint and the lower pipe joint correspondingly include an outer casing, a middle casing, and an inner casing arranged from the outside in; wherein... The outer wall surface of the outer sleeve is provided with a first external thread and a second external thread, the second external thread being screwed to the first sleeve, and the first external thread being screwed to the sleeve assembly; the outer wall surface of the middle sleeve is provided with an intermediate thread that is screwed to the second sleeve, and the inner wall surface of the inner sleeve is provided with an internal thread that is screwed to the third sleeve.

3. The underground geothermal photovoltaic power generation system according to claim 2, characterized in that, The intermediate sleeve and the inner sleeve are stacked together, and the inner wall of the intermediate sleeve has a heat-insulating air gap.

4. A downhole geothermal photovoltaic power generation system according to claim 2, characterized in that, A seat is provided on the side where the upper pipe joint and the lower pipe joint are connected to the sleeve assembly, and the outer sleeve, the middle sleeve and the inner sleeve are vertically arranged on the seat. The inflow channel is formed by the outer sleeve, the middle sleeve, and the seat, and the outflow channel is formed by the lumen of the inner sleeve and the seat. The base body has multiple cold end diversion holes at the position corresponding to the inflow channel, and multiple hot end diversion holes at the position corresponding to the outflow channel; The cold end diversion hole connects the inlet channel to the corresponding heat sink, and the hot end diversion hole connects the outlet channel to the corresponding heat sink.

5. A downhole geothermal photovoltaic power generation system according to claim 1, characterized in that, Each of the aforementioned thermal photovoltaic power generation modules also includes: The flow channel connectors are provided at opposite ends of each heat sink. The flow channel connectors connect the corresponding heat sink to the inflow channel or the outflow channel through connecting pipes, and connect the heat sinks of two adjacent thermal photovoltaic power generation modules one by one. Two cover plates are disposed on the outer wall surfaces of the two heat sinks located on either side of the edge; At least one screw, each screw being fixed to two cover plates, presses and fixes multiple heat sinks and multiple layers of thermoelectric modules between the two cover plates.

6. A downhole geothermal photovoltaic power generation system according to claim 5, characterized in that, The positions of the two flow channel joints on the same heat sink are staggered, and the positions of multiple heat sinks on the same end are staggered.

7. A downhole geothermal photovoltaic power generation system according to claim 1, characterized in that, Each of the heat sinks has an organ pipe structure.

8. A downhole geothermal photovoltaic power generation system according to claim 1, characterized in that, The sleeve assembly includes: The protective sleeve is connected to the upper pipe joint and the lower pipe joint at both ends by flanges respectively; the protective sleeve is also connected to the cover plate of each of the thermal photovoltaic power generation modules by multiple fastening screws; A connecting sleeve is fitted onto the outside of the protective sleeve, and both ends are screwed to the second external threads of the upper pipe joint and the lower pipe joint, respectively.

9. A downhole geothermal photovoltaic power generation system according to claim 8, characterized in that, A rubber ring is provided between the protective sleeve and the connecting sleeve.

10. A downhole geothermal photovoltaic power generation system according to claim 2, characterized in that, The three-layer casing is also used to connect with surface equipment to transport the heat transfer medium after heat transfer to the thermoelectric power generation module to the surface, so as to utilize the waste heat of the heat transfer medium.

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