Water pressure balance type cavern compressed air energy storage device and method

Abstract

The invention provides a water pressure balance type cavern compressed air energy storage device and method. The device comprises a storage cavern, a gas inlet and outlet vertical shaft, an underground water inlet and outlet vertical shaft, a closed-loop reservoir, a compression unit, an expansion unit and a power generator. The first end of the storage cavern is connected with the bottom of the gas inlet and outlet vertical shaft distributed in the vertical direction, and the second end of the storage cavern is connected with the bottom of the underground water inlet and outlet vertical shaft distributed in the vertical direction. The closed-loop reservoir located on the ground is connected with the top of the underground water inlet and outlet vertical shaft. A compressed air input end and a compressed air output end are arranged at the top of the gas inlet and outlet vertical shaft, the compressed air input end is connected with the compression unit, and the compressed air output end is connected with the expansion unit. The method has the technical effects that the storage pressure of the compressed air in the air storage cavern can be kept constant, so that the system efficiency of the energy storage power station is improved, and the problems of large pressure fluctuation, low working efficiency and the like in the efficient inflation and deflation process of an existing compressed air energy storage power station are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of compressed air energy storage technology for rock caves, specifically relating to a water pressure balanced compressed air energy storage device and method for rock caves. Background Technology

[0002] Energy storage is an indispensable and crucial component of future new power systems dominated by new energy sources. Compressed air energy storage (CAES), as an important type of energy storage, possesses unique advantages not found in other types such as pumped hydro storage and electrochemical energy storage, and has significant development potential. Compared to pumped hydro storage, CAES has a shorter construction cycle, is relatively easier to select sites, is more environmentally friendly, and involves fewer resettlement and relocation issues. Compared to the currently more mature lithium-ion battery energy storage, CAES has a longer lifespan, more cycle lifespan, better safety, is clean and pollution-free, and its system performance does not degrade. Furthermore, CAES has frequency and voltage regulation capabilities similar to traditional thermal power, as well as rotational inertia and short-circuit current support, which is beneficial for the safe and stable operation of power systems in future scenarios with a high proportion of new energy sources.

[0003] Under current policy and market conditions, compressed air energy storage has wide applications in various scenarios such as the power supply side and the grid side of the power system. Conducting research on key technologies for compressed air energy storage and promoting its application can increase the consumption of renewable energy sources such as wind and solar power, and indirectly achieve large-scale carbon reduction.

[0004] Currently, underground compressed air energy storage facilities are mainly designed for sliding pressure. Because the gas pressure stored inside the cavern is constantly changing, the system efficiency of the power station is relatively low. Therefore, there is an urgent need for a water pressure balanced cavern compressed air energy storage device and method to significantly improve compressed air technology and system efficiency. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a new technical solution for a water pressure balanced rock cave compressed air energy storage device and method.

[0006] According to a first aspect of the present invention, a water pressure balanced compressed air energy storage device for rock caves is provided, comprising: The storage cavern, gas inlet and outlet shaft, and groundwater inlet and outlet shaft are provided. The first end of the storage cavern is connected to the bottom of the gas inlet and outlet shaft distributed vertically, and the second end of the storage cavern is connected to the bottom of the groundwater inlet and outlet shaft distributed vertically. The system includes a closed-loop water storage tank, a compression unit, an expansion unit, and a generator. The closed-loop water storage tank, located on the ground, is connected to the top of the groundwater inlet / outlet shaft. The top of the gas inlet / outlet shaft has a compressed air input end and a compressed air output end. The compressed air input end is connected to the compression unit, the compressed air output end is connected to the expansion unit, and the generator is coaxially connected to the expansion unit. During the energy storage phase, the air is compressed by the compression unit to form compressed air with a preset pressure. The compressed air enters the storage chamber through the gas inlet and outlet shaft for storage. At the same time, the groundwater in the storage chamber is pressed into the groundwater inlet and outlet shaft and transported to the closed-loop water storage tank. During the energy release phase, under the action of hydrostatic pressure in the closed-loop reservoir, compressed air in the gas storage chamber enters the expansion unit through the gas inlet and outlet shaft to do work and drive the generator to generate electricity.

[0007] Optionally, the water pressure balanced cavern compressed air energy storage device further includes a first connecting tunnel and a second connecting tunnel; Multiple storage chambers are spaced apart and arranged in parallel, with the first end of each storage chamber connected by the first connecting tunnel and the second end connected by the second connecting tunnel; the first connecting tunnel is connected to the bottom of the gas inlet / outlet shaft, and the second connecting tunnel is connected to the bottom of the groundwater inlet / outlet shaft.

[0008] Optionally, the compression unit includes a first compressor and a second compressor, wherein the input end of the second compressor is connected to the first compressor, and the output end of the second compressor is connected to the compressed air input end; The expansion unit includes a first expander and a second expander. The input end of the second expander is connected to the compressed air output end, and the output end of the second expander is connected to the first expander.

[0009] Optionally, the water pressure balanced cavern compressed air energy storage device also includes a compressed heat storage tank, a first heat exchanger, and a second heat exchanger; The compressed heat storage tank includes a heat energy tank and a cold energy tank. The first heat exchanger is installed on the pipeline connecting the first compressor and the second compressor, and the second heat exchanger is installed on the pipeline connecting the second compressor and the compressed air input end. The cold energy tank and the hot energy tank are respectively connected to the first heat exchanger. The cold medium in the cold energy tank can exchange heat with the initial compressed air output by the first compressor through the first heat exchanger and then return to the hot energy tank to form a hot medium. The cold energy tank and the hot energy tank are respectively connected to the second heat exchanger. The cold medium in the cold energy tank can exchange heat with the secondary compressed air output by the second compressor through the second heat exchanger and then return to the hot energy tank to form a hot medium.

[0010] Optionally, the water pressure balanced cavern compressed air energy storage device also includes a third heat exchanger and a fourth heat exchanger; The third heat exchanger is installed on the pipe connecting the second expander and the compressed air output end, and the fourth heat exchanger is installed on the pipe connecting the second expander and the first expander; The cold energy tank and the hot energy tank are respectively connected to the third heat exchanger. The hot medium in the hot energy tank can exchange heat with the compressed air output from the storage chamber through the third heat exchanger and then return to the cold energy tank to form a cold medium. The cold energy tank and the hot energy tank are respectively connected to the fourth heat exchanger. The hot medium in the hot energy tank can exchange heat with the primary expansion air output by the second expander through the fourth heat exchanger and then return to the cold energy tank to form a cold medium.

[0011] Optionally, the longitudinal section of the storage chamber is trapezoidal.

[0012] Optionally, the water storage capacity of the closed-loop reservoir is twice the volume of the storage cavern.

[0013] Optionally, the storage cavern is located 600m below the groundwater level.

[0014] According to a second aspect of the present invention, a method for water pressure balanced compressed air energy storage in a rock cave is provided, applicable to a water pressure balanced compressed air energy storage device in a rock cave as described in the first aspect, comprising the following steps: During the energy storage phase, the air is compressed by the compression unit to form compressed air with a preset pressure. The compressed air enters the storage chamber through the gas inlet and outlet shaft for storage. At the same time, the groundwater in the storage chamber is pressed into the groundwater inlet and outlet shaft and transported to the closed-loop water storage tank. During the energy release phase, under the action of hydrostatic pressure in the closed-loop reservoir, compressed air in the gas storage chamber enters the expansion unit through the gas inlet and outlet shaft to do work and drive the generator to generate electricity.

[0015] Optionally, during the energy storage phase, the heat generated when the air is compressed is absorbed by the cold medium in the cold energy tank, and the cold medium absorbs the heat to form a hot medium which is stored in the hot energy tank. During the energy release phase, compressed air absorbs heat from the heat medium inside the heat energy tank. After the heat from the heat medium inside the heat energy tank is absorbed, it forms a cold medium that is stored in the cold energy tank.

[0016] One technical advantage of this invention is that: In this embodiment, during the energy storage phase, air is compressed by a compression unit to form compressed air with a preset pressure. This compressed air enters the storage chamber through a gas inlet / outlet shaft for storage. Simultaneously, groundwater within the storage chamber is forced into the groundwater inlet / outlet shaft and transported to a closed-loop reservoir. During the energy release phase, under the hydrostatic pressure in the closed-loop reservoir, the compressed air in the storage chamber enters the expansion unit through the gas inlet / outlet shaft to perform work and drive a generator to generate electricity. The surrounding rock of the storage chamber must possess good integrity and low permeability to ensure airtightness and reduce the risk of gas leakage.

[0017] Therefore, this application does not require the use of devices such as submersible pumps or booster pumps. It only uses the groundwater in the closed-loop reservoir to keep the pressure of compressed air in the storage cavern constant in order to improve power generation efficiency. By controlling the water level change of the closed-loop reservoir located on the ground, it achieves dynamic compensation for the volume change of compressed gas in the storage cavern, thereby maintaining the pressure stability of the entire device during the filling and releasing of gas in the storage cavern. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a water pressure balanced compressed air energy storage device for rock caves according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the storage chamber, gas inlet and outlet shaft, and groundwater inlet and outlet shaft of a water pressure balance type compressed air energy storage device for rock caves according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the air-filling stage of a water pressure balance type compressed air energy storage device for rock caves according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the venting stage of a water pressure balance type compressed air energy storage device for rock caves according to an embodiment of the present invention. Figure 5 This is a cross-sectional schematic diagram of the storage chamber of a water pressure balanced compressed air energy storage device for rock caves according to an embodiment of the present invention; Figure 6 This is a cross-sectional schematic diagram of the first or second connecting tunnel of a water pressure balance type compressed air energy storage device for rock caves according to an embodiment of the present invention.

[0019] In the diagram: 1. Storage chamber; 2. Gas inlet / outlet shaft; 3. Groundwater inlet / outlet shaft; 4. Closed-loop reservoir; 51. First compressor; 52. Second compressor; 61. First expander; 62. Second expander; 71. First heat exchanger; 72. Second heat exchanger; 73. Third heat exchanger; 74. Fourth heat exchanger; 81. First connecting tunnel; 82. Second connecting tunnel; 9. Compression heat storage tank; 10. Generator; 11. Electric motor. Detailed Implementation

[0020] Various exemplary embodiments of this application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of this application.

[0021] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0022] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0023] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application 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 this application.

[0024] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0025] According to a first aspect of the invention, see Figures 1 to 6This invention provides a water pressure balanced compressed air energy storage device for rock caverns, which has the advantages of large scale, strong targeting, high reliability, wide applicability, and integration of multiple technologies and devices, and can be quickly applied to the construction of compressed air energy storage.

[0026] Specifically, the water pressure balanced cavern compressed air energy storage device includes: The storage chamber 1, the gas inlet and outlet shaft 2, and the groundwater inlet and outlet shaft 3 are provided. The first end of the storage chamber 1 is connected to the bottom of the gas inlet and outlet shaft 2, which is distributed vertically, and the second end of the storage chamber 1 is connected to the bottom of the groundwater inlet and outlet shaft 3, which is distributed vertically. The closed-loop water storage tank 4, compression unit, expansion unit, and generator 10 are located on the ground and connected to the top of the groundwater inlet / outlet shaft 3. The top of the gas inlet / outlet shaft 2 has a compressed air input end and a compressed air output end. The compressed air input end is connected to the compression unit, and the compressed air output end is connected to the expansion unit. The generator 10 is coaxially connected to the expansion unit. The closed-loop water storage tank 4 is used to provide hydrostatic compensation to maintain a constant pressure throughout the underground compressed gas storage cavern.

[0027] During the energy storage phase, the air is compressed by the compression unit to form compressed air with a preset pressure. The compressed air enters the storage chamber 1 through the gas inlet and outlet shaft 2 for storage. At the same time, the groundwater in the storage chamber 1 is pressed into the groundwater inlet and outlet shaft 3 and transported to the closed-loop water storage tank 4.

[0028] It should be noted that, see Figure 3 During the energy storage phase (i.e., the inflation phase), high-pressure, low-temperature compressed air is transported to the underground cavern through the gas inlet / outlet shaft 2. Hydrostatic compensation is used within the underground cavern to maintain a constant pressure of the high-pressure, low-temperature compressed air. As the high-pressure, low-temperature compressed air is continuously injected, groundwater within the underground cavern is forced into the groundwater inlet / outlet shaft 3 and transported to the closed-loop reservoir 4 on the surface. This eliminates the need for pumps or turbines; the constant pressure within the storage cavern 1 is sufficient to transport groundwater through the shaft 3 and to the closed-loop reservoir 4, thereby reducing system installation costs and improving energy storage efficiency.

[0029] During the energy release phase, under the action of the hydrostatic pressure in the closed-loop reservoir 4, the compressed air in the gas storage chamber enters the expansion unit through the gas inlet and outlet shaft 2 to do work and drive the generator 10 to generate electricity.

[0030] It should be noted that, see Figure 4During the energy release phase (i.e., the gas release phase), the hydrostatic pressure in the closed-loop reservoir 4 located on the ground forces the compressed air in the gas storage chamber to float to the ground through the gas inlet and outlet shaft 2 and drive the expansion unit to do work. There is no need to use devices such as submersible pumps or booster pumps. The groundwater in the closed-loop reservoir 4 can be used to keep the pressure of the compressed air constant to improve the power generation efficiency. The operation is simple.

[0031] In this embodiment, the surrounding rock of the gas storage cavern must have good integrity and low permeability to ensure airtightness and reduce the risk of gas leakage. Furthermore, this application does not require the use of submersible pumps or booster pumps; it only utilizes the groundwater in the closed-loop reservoir 4 to maintain a constant pressure of compressed air within the storage cavern 1 to improve power generation efficiency. Dynamic compensation for changes in the volume of compressed gas within the storage cavern 1 is achieved by controlling the water level changes in the closed-loop reservoir 4 located on the ground, thereby maintaining pressure stability throughout the entire device during the inflation and deflation process of the storage cavern 1.

[0032] For example, the operating pressure of this pressure-balanced rock cavern compressed air energy storage device is relatively constant, typically 6MPa-7MPa. During the inflation and deflation process, static compensation is achieved through a closed-loop water storage tank 4 located on the ground. Moreover, during the operation of this pressure-balanced rock cavern compressed air energy storage device, the fluctuating water volume in and out of the vertical shaft 3 needs to compensate for the gas loss caused during compressed air injection and extraction, as well as the pressure difference ΔPdip caused by the compressed air merging into the groundwater.

[0033] Optionally, the water pressure balanced cavern compressed air energy storage device further includes a first connecting tunnel 81 and a second connecting tunnel 82; Multiple storage chambers 1 are spaced apart and arranged in parallel, and the first ends of the multiple storage chambers 1 are connected by the first connecting tunnel 81, and the second ends are connected by the second connecting tunnel 82; the first connecting tunnel 81 is connected to the bottom of the gas inlet and outlet shaft 2, and the second connecting tunnel 82 is connected to the bottom of the groundwater inlet and outlet shaft 3.

[0034] Optionally, the compression unit includes a first compressor 51 and a second compressor 52, the input end of the second compressor 52 is connected to the first compressor 51, and the output end of the second compressor 52 is connected to the compressed air input end; wherein, both the first compressor 51 and the second compressor 52 are connected to the electric motor 11, and the electric motor 11 can provide electrical energy to the first compressor 51 and the second compressor 52.

[0035] The expansion unit includes a first expander 61 and a second expander 62. The input end of the second expander 62 is connected to the compressed air output end, and the output end of the second expander 62 is connected to the first expander 61.

[0036] In the above embodiment, the first expander 61 and the second expander 62 enable multi-stage expanders to perform work and drive the generator 10 to generate electricity on demand, thereby significantly improving the efficiency of compressed air. No fuel is used during the power generation process, achieving zero emissions.

[0037] Optionally, the water pressure balanced cave compressed air energy storage device also includes a compressed heat storage tank 9, a first heat exchanger 71, and a second heat exchanger 72. The compressed heat storage tank 9 includes a heat energy tank and a cold energy tank. The first heat exchanger 71 is installed on the pipeline connecting the first compressor 51 and the second compressor 52, and the second heat exchanger 72 is installed on the pipeline connecting the second compressor 52 and the compressed air input end. The cold energy tank and the hot energy tank are respectively connected to the first heat exchanger 71. The cold medium in the cold energy tank can exchange heat with the initial compressed air output by the first compressor 51 through the first heat exchanger 71 and then return to the hot energy tank to form a hot medium. The cold energy tank and the hot energy tank are respectively connected to the second heat exchanger 72. The cold medium in the cold energy tank can exchange heat with the secondary compressed air output by the second compressor 52 through the second heat exchanger 72 and then return to the hot energy tank to form a hot medium.

[0038] In the above embodiment, the heat generated during compression is extracted from the high-temperature, high-pressure gas flow by the first compressor 51 and the second compressor 52, captured by the cold energy tank of the compression heat storage tank 9, and stored in the ground-based heat storage tank for subsequent reuse. This energy storage method using sensible heat storage improves overall utilization efficiency and eliminates the need for fossil fuels during operation.

[0039] Optionally, the water pressure balanced cavern compressed air energy storage device also includes a third heat exchanger 73 and a fourth heat exchanger 74; The third heat exchanger 73 is installed on the pipe connecting the second expander 62 and the compressed air output end, and the fourth heat exchanger 74 is installed on the pipe connecting the second expander 62 and the first expander 61. The cold energy tank and the hot energy tank are respectively connected to the third heat exchanger 73. The hot medium in the hot energy tank can exchange heat with the compressed air output from the storage chamber 1 through the third heat exchanger 73 and then return to the cold energy tank to form a cold medium. The cold energy tank and the hot energy tank are respectively connected to the fourth heat exchanger 74. The hot medium in the hot energy tank can exchange heat with the primary expansion air output by the second expander 62 through the fourth heat exchanger 74 and then return to the cold energy tank to form a cold medium.

[0040] In the above embodiment, the third heat exchanger 73 and the fourth heat exchanger 74 provide heat for the expansion process of compressed air, which helps to ensure the stability of the work done in the expansion process.

[0041] Optionally, the longitudinal section of the storage chamber 1 along its length is trapezoidal, which helps to store compressed air and groundwater, and also helps to ensure stable operation during the inflation and deflation phases.

[0042] For example, the longitudinal section of storage chamber 1 along the width direction is oval, which helps to withstand higher storage pressure.

[0043] See Figure 5 and Figure 6 The two ends of the storage cavern 1 adopt a 1:1 slope, gradually transitioning the cross-sectional form along the width direction of the storage cavern 1 to the smaller cross-sectional size along the width direction of the first connecting tunnel 81 or the second connecting tunnel 82, so as to ensure the stability of the connection between the storage cavern 1 and the first connecting tunnel 81 or the second connecting tunnel 82, making the water flow and air flow distribution more uniform, and improving the overall operating efficiency and safety.

[0044] In one specific implementation, the longitudinal section of storage chamber 1 along its width is oval-shaped, measuring 18m wide × 26m high, with a perimeter of 75.94m and an area of ​​396.3733m². 2 ,like Figure 5 As shown. The longitudinal section of the first connecting tunnel 81 and the second connecting tunnel 82 along the width direction is a straight-walled circular arch, 4.5m wide × 5m high, with a perimeter of 20.08m and an area of ​​20.34m². 2 ,like Figure 6 As shown.

[0045] Both the gas inlet / outlet shaft 2 and the groundwater inlet / outlet shaft 3 have circular cross-sections, with a diameter of 5m, a circumference of 15.7m, and an area of ​​19.625m². 2 .

[0046] Optionally, the water storage capacity of the closed-loop reservoir 4 is twice the volume of the storage cavern 1. This, after considering factors such as surface evaporation and runoff, ensures the safe and stable operation of the pressure-balanced rock cavern compressed air energy storage device. Of course, the water storage capacity of the closed-loop reservoir 4 can also be optimized and adjusted according to the hydrological information and climate characteristics of the actual project.

[0047] Optionally, the storage chamber 1 is located 600m below the groundwater level.

[0048] In the above-described embodiments, automatic hydrostatic pressure compensation and balance can be achieved. By combining pumped hydro storage with compressed air storage, and by setting up a closed-loop reservoir 4 on the ground to provide hydrostatic compensation to maintain a constant pressure throughout the underground compressed air storage cavern, underwater compressed air storage reduces the limitations of onshore construction. The above parameters can be calculated and determined based on the actual construction scale and land acquisition area to determine the burial depth of the gas storage cavern, the volume of the surface reservoir, and the layout scheme.

[0049] Compared with traditional constant-capacity compressed air energy storage technology, this application uses constant-pressure compressed air energy storage to avoid the unavoidable buffer air in constant-capacity compressed air energy storage systems, enabling the compression unit and expansion unit to operate efficiently under constant discharge pressure and eliminating throttling losses before the expansion unit.

[0050] The water pressure balance type compressed air energy storage device in the cave mainly consists of two independent processes: compression energy storage and expansion energy release. However, by setting up a closed-loop water storage tank 4 on the ground, hydrostatic compensation is provided to maintain a constant pressure in the entire underground compressed air energy storage cavern.

[0051] In one specific implementation, the compression unit is operated using off-peak or surplus energy from the power grid or renewable energy sources to generate high-temperature, high-pressure compressed air. The heat generated during compression is extracted from the high-temperature, high-pressure airflow and captured by the cold energy tank of the compression heat storage tank 9, then stored in a ground-based heat storage tank for subsequent reuse. This energy storage method, which uses sensible heat storage, improves overall utilization efficiency and eliminates the need for fossil fuels during operation.

[0052] like Figure 3 As shown, once the heat is extracted, the high-pressure, low-temperature compressed air is transported to the storage chamber 1 through the gas inlet / outlet shaft 2. The storage chamber 1 uses hydrostatic compensation to maintain a constant pressure of the high-pressure, low-temperature compressed air. As the high-pressure, low-temperature compressed air is continuously injected, the groundwater in the storage chamber 1 is forced into the groundwater inlet / outlet shaft 3 and transported to the closed-loop reservoir 4 on the surface.

[0053] Since the storage cavern 1 maintains a constant pressure of about 6-7 MPa, there is no need to install a water pump or turbine. The groundwater can be pumped into the groundwater inlet and outlet shaft 3 and transported to the closed-loop reservoir 4 on the ground simply by relying on the constant pressure in the storage cavern 1, thereby reducing the system installation cost and improving energy storage efficiency.

[0054] According to a second aspect of the present invention, a method for water pressure balanced compressed air energy storage in a rock cave is provided, applicable to a water pressure balanced compressed air energy storage device in a rock cave as described in the first aspect, comprising the following steps: During the energy storage phase, the air is compressed by the compression unit to form compressed air with a preset pressure. The compressed air enters the storage chamber 1 through the gas inlet and outlet shaft 2 for storage. At the same time, the groundwater in the storage chamber 1 is pressed into the groundwater inlet and outlet shaft 3 and transported to the closed-loop water storage tank 4. During the energy release phase, under the action of the hydrostatic pressure in the closed-loop reservoir 4, the compressed air in the gas storage chamber enters the expansion unit through the gas inlet and outlet shaft 2 to do work and drive the generator 10 to generate electricity.

[0055] In this embodiment, the water pressure-balanced compressed air energy storage method in a rock cavern utilizes a closed-loop reservoir 4 for static compensation during the charging and discharging process to maintain a constant storage pressure within the storage chamber 1. This improves the system efficiency of the energy storage power station and effectively solves the problems of large pressure fluctuations and low operating efficiency in the efficient charging and discharging process of existing compressed air energy storage power stations. Furthermore, this water pressure-balanced compressed air energy storage method allows for appropriate adjustment of device parameters based on actual operating conditions, offering significant optimization potential.

[0056] In addition, this water pressure balance type compressed air energy storage method for rock caverns has important application value for various underground engineering and underground space projects such as underground compressed air energy storage facilities and underground compressed carbon dioxide energy storage facilities.

[0057] Optionally, during the energy storage phase, the heat generated when the air is compressed is absorbed by the cold medium in the cold energy tank, and the cold medium absorbs the heat to form a hot medium which is stored in the hot energy tank. During the energy release phase, compressed air absorbs heat from the heat medium inside the heat energy tank. After the heat from the heat medium inside the heat energy tank is absorbed, it forms a cold medium that is stored in the cold energy tank.

[0058] The above implementation method helps to make full use of the heat generated during the air compression process and improve resource utilization.

[0059] It should be noted that this water pressure balanced cavern compressed air energy storage device and method systematically provides a complete set of technologies and solutions for the construction of water pressure balanced cavern compressed air energy storage, promoting the advancement of long-term energy storage technology and ensuring the healthy development of the energy storage economy. Based on the construction principle of water pressure balanced cavern compressed air energy storage and the functional requirements of static compensation constant pressure storage, this invention designs the functions and structures of different individual units such as the ground facilities (i.e., closed-loop reservoir), storage caverns, connecting tunnels, and shafts, taking into account practical engineering needs. It also designs the working pressure of the storage caverns and the static compensation of the ground reservoir. Only moderately strong hard rock strata are needed to meet all construction requirements, demonstrating extremely high tolerance for geological conditions and applicability to various scenarios including different engineering geology, hydrogeology, and underground engineering layouts. Moreover, by integrating various ground facilities, underground units, structures, and devices, a large-scale, highly targeted, highly reliable, easy-to-operate, low-cost, and widely applicable method is provided for the construction of water pressure balanced rock cavern compressed air energy storage. This method can be quickly applied to the construction of long-term compressed air energy storage, effectively reducing the cost of compressed air storage, improving economic efficiency, and thus promoting the healthy development of the energy storage industry chain.

[0060] In the embodiments of this application, the water pressure balanced rock cave compressed air energy storage device and method have the following technical effects: Firstly, this invention addresses the significant limitations of existing compressed air energy storage systems due to geological structures, geographical resources, and site location, resulting in limited applicability. It creates a water pressure balanced compressed air energy storage device to solve the technical problems of small energy storage capacity, low efficiency, high cost, and difficult site selection in existing compressed air energy storage power stations. This is of great significance for overcoming the bottleneck of long-term energy storage construction.

[0061] Secondly, this invention solves the technical problems of existing compressed air storage methods, such as small scale, high cost, and great limitations in geological conditions and geographical location. It only requires the selection of hard rock strata with moderate strength to meet all construction requirements, has a very high tolerance for geological conditions, and has a wide range of applications.

[0062] Thirdly, the working pressure, energy storage capacity, surface closed-loop water storage tank, underground storage cavern, connecting tunnel, and vertical shaft of the water pressure balance type compressed air energy storage device of the present invention can all be appropriately adjusted according to the actual working conditions, and there is a large optimization space.

[0063] Fourthly, the water pressure balanced cave compressed air energy storage device of the present invention can be used not only for compressed air energy storage, but also for compressed carbon dioxide energy storage.

[0064] Fifthly, this invention integrates various ground facilities, underground units, structures, and devices to provide a large-scale, highly targeted, highly reliable, convenient, low-cost, and widely applicable method for constructing water pressure balanced cavern compressed air energy storage. It can be quickly applied to the construction of long-term compressed air energy storage, effectively reducing the cost of compressed air storage, improving economic efficiency, and thus promoting the healthy development of the energy storage industry chain.

[0065] For example, the closed-loop reservoir in this embodiment has a water storage capacity of 10 × 10⁴ m³. 3 Water from fissures within the underground caverns during construction is collected and stored in a closed-loop reservoir on the surface for recycling throughout the entire energy storage system.

[0066] The storage chamber in this embodiment has a spatial volume of 5×10. 4 m 3 With a storage pressure of 6-7 MPa and a storage chamber buried more than 600m underground, automatic hydrostatic pressure balancing can be achieved. The energy storage time is 4 hours and the number of cycles per day is 6. Therefore, the energy storage capacity of this embodiment is 50MW / 300MWh, and the system efficiency reaches more than 70%.

[0067] The cavity pressure caused by compressed air dissolving into the fissure water can be calculated using the formula ΔP. dip Then, additional groundwater is added as needed to achieve a pressure balance.

[0068] ; In the formula: The pressure drop in the cavity caused by air dissolving into the fissure water is expressed in mbar / h. 'a' represents the amount of air dissolved in water, expressed in mL / L. Refer to Table 1 for the value and then convert it to m. 3 / m 3 ; This represents the direct change in groundwater level within the cave, expressed in meters (m). 3 ; The gas pressure in the storage chamber, expressed in MPa; V gas2 The volume occupied by the gas in the storage chamber, expressed in m³. 3 .

[0069] Table 1 shows the equilibrium solubility of air in water (10 MPa).

[0070] Taking this embodiment as an example, the storage chamber has a capacity of 5×10 4 m 3The storage pressure is constant at 6 MPa, and the temperature inside the storage chamber is constant at 20℃ (293.15 K). Assume the volume of compressed air already stored in the storage chamber is 4 × 10⁻⁶. 4 m 3 1×10 4 m 3 After the compressed air inside the cave is compressed, the remaining compressed air volume is 3 × 10⁻⁶. 4 m 3 It is necessary to replenish 20% of the groundwater, that is, 1×10 4 m 3 ,but: =18.68×10 -3 ×1×10 4 ×6 / (3×10 4 =0.038 MPa.

[0071] Due to changes in gas solubility, additional groundwater needs to be added to compensate for the pressure loss caused by ΔPdip. This can be calculated using the following formula: ; The indirect change value of groundwater within the cave, in meters. 3 ; Based on the results of this embodiment, it can be concluded that =18.68×10 -3 ×1×10 4 =186.8 m 3 .

[0072] Therefore, the final groundwater replenishment amount in this embodiment is =1.19×10 4 m 3 .

[0073] If the constant pressure design of this invention is not adopted, the pressure difference ΔP inside the tunnel caused by the change in gas volume can be solved using the ideal equation of state: ; ; ; In the formula: The gas pressure difference caused by compressed air injection / extraction, expressed in Pa; R is the ideal gas constant, approximately 8.314 J / (mol·K); T represents the temperature inside the cave, measured in Kelvin (K). V1 is the volume inside the tunnel before compressed air extraction, in meters. 3 ; V2 is the volume inside the tunnel after compressed air is extracted, in meters. 3 ; n1 represents the amount of material before compressed air extraction. For example, in this embodiment, the amount of air material stored in the tunnel before injection and extraction is 1.23 × 10⁻⁶ m³. 8 mol; n2 represents the amount of material produced after compressed air extraction. For example, in this embodiment, the amount of air material produced after 30,000 cubic meters of compressed air is 9.84 × 10⁻⁶. 7 mol; Taking this embodiment as an example, the storage chamber has a capacity of 5×10 4 m 3 The room temperature is 20℃, or 293.15 K. After 20% of the compressed air is extracted through the air shaft, the gas pressure inside the tunnel becomes... =(9.84×10 7 ×8.314×293.15) / (5×10 4 ≈4.8MPa, pressure difference ≈1.2MPa.

[0074] In summary, if the hydrostatic pressure balance replenishment scheme of the present invention is not adopted, a single injection and extraction can cause the storage pressure of compressed air in the tunnel to drop from 6MPa to 4.8MPa, thereby greatly affecting the power generation efficiency of the ground energy storage power station.

[0075] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A water pressure balanced compressed air energy storage device for rock caves, characterized in that, include: The storage cavern, gas inlet and outlet shaft, and groundwater inlet and outlet shaft are provided. The first end of the storage cavern is connected to the bottom of the gas inlet and outlet shaft distributed vertically, and the second end of the storage cavern is connected to the bottom of the groundwater inlet and outlet shaft distributed vertically. The system includes a closed-loop water storage tank, a compression unit, an expansion unit, and a generator. The closed-loop water storage tank, located on the ground, is connected to the top of the groundwater inlet / outlet shaft. The top of the gas inlet / outlet shaft has a compressed air input end and a compressed air output end. The compressed air input end is connected to the compression unit, the compressed air output end is connected to the expansion unit, and the generator is coaxially connected to the expansion unit. During the energy storage phase, the air is compressed by the compression unit to form compressed air with a preset pressure. The compressed air enters the storage chamber through the gas inlet and outlet shaft for storage. At the same time, the groundwater in the storage chamber is pressed into the groundwater inlet and outlet shaft and transported to the closed-loop water storage tank. During the energy release phase, under the action of hydrostatic pressure in the closed-loop reservoir, compressed air in the gas storage chamber enters the expansion unit through the gas inlet and outlet shaft to do work and drive the generator to generate electricity.

2. The water pressure balanced compressed air energy storage device for rock caves according to claim 1, characterized in that, It also includes the first connecting tunnel and the second connecting tunnel; Multiple storage chambers are spaced apart and arranged in parallel, with the first end of each storage chamber connected by the first connecting tunnel and the second end connected by the second connecting tunnel; the first connecting tunnel is connected to the bottom of the gas inlet / outlet shaft, and the second connecting tunnel is connected to the bottom of the groundwater inlet / outlet shaft.

3. The water pressure balanced compressed air energy storage device for rock caves according to claim 2, characterized in that, The compression unit includes a first compressor and a second compressor, the input end of the second compressor is connected to the first compressor, and the output end of the second compressor is connected to the compressed air input end; The expansion unit includes a first expander and a second expander. The input end of the second expander is connected to the compressed air output end, and the output end of the second expander is connected to the first expander.

4. The water pressure balanced compressed air energy storage device for rock caves according to claim 3, characterized in that, It also includes a compression heat storage tank, a first heat exchanger, and a second heat exchanger; The compressed heat storage tank includes a heat energy tank and a cold energy tank. The first heat exchanger is installed on the pipeline connecting the first compressor and the second compressor, and the second heat exchanger is installed on the pipeline connecting the second compressor and the compressed air input end. The cold energy tank and the hot energy tank are respectively connected to the first heat exchanger. The cold medium in the cold energy tank can exchange heat with the initial compressed air output by the first compressor through the first heat exchanger and then return to the hot energy tank to form a hot medium. The cold energy tank and the hot energy tank are respectively connected to the second heat exchanger. The cold medium in the cold energy tank can exchange heat with the secondary compressed air output by the second compressor through the second heat exchanger and then return to the hot energy tank to form a hot medium.

5. The water pressure balanced compressed air energy storage device for rock caves according to claim 4, characterized in that, It also includes a third heat exchanger and a fourth heat exchanger; The third heat exchanger is installed on the pipe connecting the second expander and the compressed air output end, and the fourth heat exchanger is installed on the pipe connecting the second expander and the first expander; The cold energy tank and the hot energy tank are respectively connected to the third heat exchanger. The hot medium in the hot energy tank can exchange heat with the compressed air output from the storage chamber through the third heat exchanger and then return to the cold energy tank to form a cold medium. The cold energy tank and the hot energy tank are respectively connected to the fourth heat exchanger. The hot medium in the hot energy tank can exchange heat with the primary expansion air output by the second expander through the fourth heat exchanger and then return to the cold energy tank to form a cold medium.

6. The water pressure balanced compressed air energy storage device for rock caves according to claim 1, characterized in that, The longitudinal section of the storage chamber is trapezoidal.

7. The water pressure balanced compressed air energy storage device for rock caves according to claim 1, characterized in that, The closed-loop reservoir has a water storage capacity that is twice the volume of the storage cavern.

8. The water pressure balanced compressed air energy storage device for rock caves according to claim 1, characterized in that, The storage cavern is located 600m below the groundwater level.

9. A water pressure balanced compressed air energy storage method for rock caverns, characterized in that, The application of the water pressure balanced cavern compressed air energy storage device as described in any one of claims 1 to 8 includes the following steps: During the energy storage phase, the air is compressed by the compression unit to form compressed air with a preset pressure. The compressed air enters the storage chamber through the gas inlet and outlet shaft for storage. At the same time, the groundwater in the storage chamber is pressed into the groundwater inlet and outlet shaft and transported to the closed-loop water storage tank. During the energy release phase, under the action of hydrostatic pressure in the closed-loop reservoir, compressed air in the gas storage chamber enters the expansion unit through the gas inlet and outlet shaft to do work and drive the generator to generate electricity.

10. The water pressure balance type compressed air energy storage method for rock caves according to claim 9, characterized in that, During the energy storage phase, the heat generated when the air is compressed is absorbed by the cold medium in the cold energy tank. After absorbing the heat, the cold medium forms a hot medium that is stored in the hot energy tank. During the energy release phase, compressed air absorbs heat from the heat medium inside the heat energy tank. After the heat from the heat medium inside the heat energy tank is absorbed, it forms a cold medium that is stored in the cold energy tank.

Images