Constant pressure type compressed air energy storage and gas storage system and gas storage method

Abstract

The invention relates to the technical field of underground energy storage, in particular to a constant-pressure compressed air energy storage and gas storage system and a gas storage method, a gas storage space type adopts a tunnel type, an underwater gas storage and an artificial chamber gas storage are combined, a series of flexible air bags are arranged in a gas storage tunnel along the axis and used for storing high-pressure gas, and the flexible air bags are used for storing the high-pressure gas. The bottom of the gas storage tunnel is connected with the high-level reservoir through a pressure water conveying pipeline, water flow of the high-level reservoir is introduced into the gas storage tunnel, and the constant-pressure gas storage effect is achieved by means of balance of hydrostatic pressure and internal pressure of the air bags. The space utilization rate and the compressed air energy storage efficiency of the manual chamber gas storage are effectively improved, the sealing effect is improved, the sealing difficulty of manual chamber gas storage and the construction cost of the gas storage are reduced, and meanwhile the problems that a conventional underwater gas storage is ballasted and site selection is not flexible enough are solved. The technical problems that an existing gas storage is low in space utilization rate and energy storage efficiency, poor in sealing effect and high in construction cost can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of underground energy storage, and in particular to a constant pressure compressed air energy storage system and a gas storage method. Background Art

[0002] Compressed air energy storage (CAES) is a technology that uses compressed air as a medium to store energy and generate electricity. It is a new type of power storage technology that offers low cost, large capacity, long-term operation, high efficiency, and flexible deployment. Currently, CAES reservoirs are primarily categorized into two types: constant volume and constant pressure.

[0003] Constant-volume gas storage structures primarily include salt caverns, artificial chambers, abandoned mines, and surface pipelines, steel pipes, or tube bundles (arrays). Salt caverns are limited, abandoned mines offer relatively poor airtightness, and surface pipelines, steel pipes, or tube bundles (arrays), are expensive, limiting their application. Artificial chambers, which largely overcome geographical constraints, offer a new gas storage method that increases site flexibility for large-scale compressed air energy storage projects. They have garnered increasing attention in recent years and have accumulated extensive implementation experience. However, existing artificial chamber gas storage solutions present issues such as airtightness. Conventional solutions primarily utilize steel plates for sealing, which must withstand both the high internal gas pressure and the external groundwater pressure. Consequently, these plates are thick and expensive. Furthermore, approximately 60-70% of the gas underfill within the storage facility cannot be utilized due to pressure fluctuations and pressure level variations, resulting in low compressed air utilization and a relatively short total usable energy storage and power generation time.

[0004] Constant-pressure gas storage is still in the research phase. The main approach involves placing the storage tank on the seabed or lake bottom, leveraging the hydrostatic pressure of water to store compressed air at a constant pressure. Compared to constant-volume gas storage, constant-pressure gas storage does not require a constant-volume backing gas, resulting in higher energy density and a smaller volume. Furthermore, during charging and discharging, it avoids drastic pressure and temperature fluctuations within the storage tank, allowing the compressor to operate efficiently at a constant discharge pressure. However, underwater gas storage requires a water depth of at least several hundred meters to achieve internal pressure balance and maintain a constant pressure. This requires proximity to deep sea or lakes, limiting its application in most inland areas. Furthermore, due to the significant density difference between air and water, gas storage tanks on the seabed or lake bottom experience significant buoyancy, requiring effective ballasting. This is not only costly but also challenging to construct in deep water. Underwater gas storage also carries the risk of infestation or attachment by local marine or lake bottom organisms, as well as instability due to seabed or lake bottom currents.

[0005] In summary, the existing gas storage methods have the problems of low space utilization, low compressed air energy storage efficiency, poor sealing effect, and high construction cost. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention proposes a constant-pressure compressed air energy storage system and method. This system organically combines underwater gas storage with artificial chamber gas storage, resolving the technical issues of existing gas storage methods, such as low storage space utilization, low compressed air energy storage efficiency, poor sealing, and high construction costs. This system not only improves the space utilization and compressed air energy storage efficiency of artificial chamber gas storage, but also enhances sealing, reducing the sealing difficulty and construction costs of existing artificial chamber gas storage. It also avoids the ballast issues and inflexible site selection inherent in existing underwater gas storage systems.

[0007] To achieve the above objectives, the present invention designs a constant pressure compressed air energy storage system, which includes a gas storage tunnel, a pressure water pipeline and a high-level reservoir, wherein the elevation of the high-level reservoir is greater than the elevation of the gas storage tunnel; The internal space of the gas storage tunnel is in the form of a tunnel. A flexible gas storage bag is arranged along the axis of the gas storage tunnel for storing compressed high-pressure gas. The top of the flexible gas storage bag is in contact with the top of the gas storage tunnel. An injection and production gas pipe connected to the flexible gas storage bag is provided at the top of the gas storage tunnel. The other end of the injection and production gas pipe is connected to an air compressor located on the ground. The bottom of the gas storage tunnel is connected to the high-level reservoir through a pressure water pipeline. The pressure water pipeline introduces the water flow in the high-level reservoir into the gas storage tunnel, and uses the static water pressure to balance the internal pressure of the flexible gas storage airbag to achieve a constant pressure gas storage effect of the gas storage system.

[0008] As a preferred solution, the upper part of the circumferential cross-section of the flexible air storage airbag after full inflation is circular and the lower part is elliptical. The radius of the upper circle is consistent with the radius of the circular cross-section of the gas storage tunnel, so as to ensure that the top of the flexible air storage airbag is tightly fitted with the top of the gas storage tunnel under the action of buoyancy; the upper part of the flexible air storage airbag is provided with an opening connected to the injection and production gas pipe; the radius of the major axis of the lower ellipse is consistent with the radius of the upper circle, and the circumferential cross-section size of the flexible air storage airbag is slightly smaller than the cross-section size of the gas storage tunnel, which is used to prevent the flexible air storage airbag from blocking the normal flow of water in the gas storage tunnel after it is fully inflated.

[0009] Furthermore, the volume of the flexible gas storage airbag after being fully inflated accounts for 74% of the volume of the gas storage tunnel, that is, the effective gas storage utilization rate of the physical space of the gas storage tunnel is 74%.

[0010] Furthermore, there are multiple flexible air storage bags arranged along the axis of the air storage tunnel. Each flexible air storage bag is capsule-shaped, and the length direction of the capsule is consistent with the axis direction of the air storage tunnel. A net distance of 1m is maintained between two adjacent flexible air storage bags.

[0011] Furthermore, the flexible air storage airbag is fixed to the top of the air storage tunnel by an airbag fixing rope to prevent the flexible air storage airbag from moving under the action of water flow inside the air storage tunnel. The airbag fixing rope only plays a limiting role and does not generate a large pulling force on the flexible air storage airbag.

[0012] As a preferred solution, the injection and production gas pipe includes an injection and production gas branch pipe, an axial injection and production gas main pipe, and a longitudinal injection and production gas main pipe that are interconnected. The injection and production gas branch pipe is arranged at the top of the flexible gas storage airbag and is connected to the top opening of the flexible gas storage airbag; the axial injection and production gas main pipe is arranged at the top of the gas storage tunnel along the axial direction of the gas storage tunnel and is connected to the injection and production gas branch pipe; the longitudinal injection and production gas main pipe is arranged at the top of the gas storage tunnel along the longitudinal direction of the gas storage tunnel and is connected to the axial injection and production gas main pipe. The end of the longitudinal injection and production gas main pipe is connected to the air compressor located on the ground, and an injection and production gas control valve is provided at the ground end of the longitudinal injection and production gas main pipe.

[0013] As a preferred option, a gas storage exhaust pipe connected to the top of the gas storage tunnel is also provided, the end of the gas storage exhaust pipe extends to the ground, and an exhaust pipe control valve is provided at the outlet end to discharge the air in the gas storage tunnel.

[0014] As a preferred solution, the pressure water supply pipeline is Z-shaped, and is provided with a high-level reservoir accident maintenance gate and a gas storage reservoir accident maintenance gate. The high-level reservoir accident maintenance gate is located on the water flow outlet side of the high-level reservoir, and the gas storage reservoir accident maintenance gate is located on the water flow inlet side of the gas storage reservoir tunnel.

[0015] Furthermore, a gas storage vent pipe is provided below the gas storage tunnel, which is connected to the bottom of the gas storage tunnel and the pressure water pipeline respectively. A gas storage vent pipe control valve is provided on the gas storage vent pipe. The gas storage vent pipe is connected to the gas storage construction branch tunnel or underground passage, and extends to the ground through the construction branch tunnel or underground passage. During maintenance, the water in the gas storage tunnel and the pressure water pipeline is discharged to the ground by gravity or pumping.

[0016] The present invention also designs a gas storage method based on a constant pressure compressed air energy storage system, comprising the following steps: Before inflation and energy storage, the underground gas storage reservoir and the gas storage airbag contain normal pressure air. The high-level reservoir emergency maintenance gate, the gas storage reservoir emergency maintenance gate, the exhaust pipe valve, and the injection and production gas control valve on the pressure water pipeline are opened respectively. The water in the high-level reservoir enters the gas storage tunnel under the action of gravity, and the air in the gas storage tunnel and the flexible gas storage airbag is discharged through the gas storage exhaust pipe and the injection and production gas pipe respectively. During the gas charging and energy storage process, the exhaust pipe valve is closed, the high-level reservoir accident maintenance gate, the gas storage reservoir accident maintenance gate, and the injection and production gas control valve remain open, and the ground air compressor injects compressed air into the flexible gas storage bladder through the injection and production gas pipe. The volume of the flexible gas storage bladder increases, and the high-pressure water in the gas storage tunnel is reversely pressed into the high-level reservoir through the pressure water pipeline; During the gas discharge power generation process, the exhaust pipe valve is closed, the high-level reservoir accident maintenance gate, the gas storage reservoir accident maintenance gate, and the injection and production gas control valve remain open, and the high-pressure gas in the flexible gas storage airbag is discharged through the injection and production gas pipe to generate electricity. The volume of the flexible gas storage airbag is reduced, and the water flow in the high-level reservoir enters the gas storage tunnel through the pressure water pipeline; During the inflation and deflation process, the pressure in the flexible air storage bag is maintained in a stable range by controlling the fluctuation of the water level in the high-level reservoir, achieving a constant pressure energy storage effect.

[0017] Compared with the prior art, the present invention has the following significant advantages: The gas storage system and method of the present invention organically combine underwater gas storage with artificial chamber gas storage, resolving the technical issues of existing gas storage methods, such as low storage space utilization, low compressed air energy storage efficiency, poor sealing, and high construction costs. This not only improves the space utilization and compressed air energy storage efficiency of artificial chamber gas storage, but also enhances sealing, reducing the sealing difficulty and construction costs of existing artificial chamber gas storage. It also avoids the ballast issues and limited site selection flexibility associated with existing underwater gas storage systems.

[0018] (1) The present invention uses air bags to store air and tunnels to store water, and utilizes the hydrostatic pressure of a high-level reservoir to achieve constant-pressure storage of compressed air. Compared with conventional artificial chambers, it does not require bottom gas and the space utilization rate can reach more than 70%. The effective space utilization rate of traditional artificial chambers is only 20% to 30%. The present invention has higher space utilization and energy storage density, and requires a smaller volume.

[0019] (2) In the present invention, by controlling the water level fluctuation of the high-level reservoir, the pressure fluctuation is within 0.3 MPa, the pressure variation amplitude is within 5%, and it is basically maintained in a constant pressure state. The compressor and expander can operate efficiently under a constant pressure, effectively improving the compressed air energy storage efficiency.

[0020] (3) During the charge and discharge process of a conventional artificial chamber, the pressure inside the gas storage fluctuates cyclically between several MPa and more than ten MPa, and the temperature fluctuates from tens of degrees to hundreds of degrees. The pressure and stability inside the gas storage fluctuate violently, and the surrounding rock and lining of the artificial chamber are easily fatigued and damaged in the high pressure and high temperature changes, which places high demands on the geological conditions of the surrounding rock and the lining type. In the present invention, the artificial chamber only needs to withstand a basically constant water pressure of about 6 MPa. The pressure it withstands during operation is even lower, and there is no cyclic load effect, nor will there be violent temperature changes. Its stress conditions and operating conditions are far superior to those of conventional artificial chambers. Therefore, its requirements on the geological conditions of the surrounding rock of the chamber are not as high as those of conventional artificial chambers. The chamber lining can adopt cheaper concrete lining or reinforced concrete lining, which effectively reduces the cost of the artificial chamber.

[0021] (4) The present invention adopts a flexible air bag as the gas storage sealing material. There is no sealing requirement for the surrounding rock lining of the cavern. During operation, the internal pressure of the cavern is mainly borne by the surrounding rock of the cavern. During maintenance, external groundwater can penetrate into the cavern through the cracks between the linings. The surrounding rock lining of the cavern basically does not bear external pressure, avoiding the situation in conventional artificial caverns where thicker steel linings are used to reduce the large external water pressure, effectively reducing the investment and cost of the cavern lining.

[0022] (5) The present invention uses a flexible airbag to store gas, which is low in cost and can be retracted, easily replaced, moved and recovered. The airbag is made of polymer material and has good sealing and corrosion resistance.

[0023] (6) The present invention uses a flexible airbag to store air. After the airbag is inflated, it floats on the top of the tunnel. The buoyancy of the airbag is offset by the lining and surrounding rock of the tunnel top, and there is no need to set up an additional ballast system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the overall arrangement diagram of the present invention; Figure 2 It is a longitudinal sectional view of the gas storage of the present invention; Figure 3 for Figure 2 A in the middle is an enlarged schematic diagram; Figure 4 This is a cross-sectional view of the gas storage of the present invention after inflation is completed; Figure 5 This is a cross-sectional view of the gas storage of the present invention when it is 50% inflated / deflated; Figure 6 This is a cross-sectional view of the gas storage of the present invention after degassing is completed.

[0025] In the figure: 1. Flexible gas storage airbag; 2. Injection and production gas branch pipe; 3-1. Axial injection and production gas main pipe; 3-2. Longitudinal injection and production gas main pipe; 4. Gas storage reservoir exhaust pipe; 5. Exhaust pipe control valve; 6. Injection and production gas control valve; 7. Pressure water pipeline; 8. Gas storage reservoir tunnel; 9. Airbag fixing rope; 10. Gas storage reservoir vent pipe; 11. Gas storage reservoir vent pipe control valve; 12. High-level reservoir; 13. High-level reservoir emergency maintenance gate; 14. Gas storage reservoir emergency maintenance gate. DETAILED DESCRIPTION

[0026] To help those skilled in the art better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the drawings are for illustrative purposes only and are not to be construed as limiting this patent. To better illustrate this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the dimensions of actual products. For those skilled in the art, the omission of certain well-known structures and their descriptions in the drawings is understandable. The positional relationships described in the drawings are for illustrative purposes only and are not to be construed as limiting this patent.

[0027] The present invention relates to a constant-pressure compressed air energy storage system and gas storage method. The gas storage space adopts a tunnel type, combining an underwater gas storage reservoir with an artificial cavern gas storage reservoir. A series of flexible airbags are arranged along the axis of the gas storage tunnel to store high-pressure gas. The bottom of the gas storage tunnel is connected to a high-level reservoir via a pressure water pipeline. Water flow from the high-level reservoir is introduced into the gas storage tunnel. The hydrostatic pressure is balanced with the pressure inside the airbags to achieve a constant-pressure gas storage effect. The present invention effectively improves the space utilization rate and compressed air energy storage efficiency of the artificial cavern gas storage reservoir, improves the sealing effect, reduces the sealing difficulty of the current artificial cavern gas storage and the gas storage construction cost, and avoids the ballast problem and inflexible site selection problems of conventional underwater gas storage reservoirs.

[0028] The present invention provides a constant pressure compressed air energy storage gas storage system, comprising a gas storage tunnel, a pressure water pipeline and a high-level water reservoir, wherein the elevation of the high-level water reservoir is greater than the elevation of the gas storage tunnel; The internal space of the gas storage tunnel is in the form of a tunnel. A flexible gas storage bag is arranged along the axis of the gas storage tunnel for storing compressed high-pressure gas. The top of the flexible gas storage bag is in contact with the top of the gas storage tunnel. An injection and production gas pipe connected to the flexible gas storage bag is provided at the top of the gas storage tunnel. The other end of the injection and production gas pipe is connected to an air compressor located on the ground. The bottom of the gas storage tunnel is connected to the high-level reservoir through a pressure water pipeline. The pressure water pipeline introduces the water flow in the high-level reservoir into the gas storage tunnel, and uses the static water pressure to balance the internal pressure of the flexible gas storage airbag to achieve a constant pressure gas storage effect of the gas storage system.

[0029] The present invention also provides a gas storage method based on a constant pressure compressed air energy storage system, comprising the following steps: Before inflation and energy storage, the underground gas storage reservoir and the gas storage airbag contain normal pressure air. The high-level reservoir emergency maintenance gate, the gas storage reservoir emergency maintenance gate, the exhaust pipe valve, and the injection and production gas control valve on the pressure water pipeline are opened respectively. The water in the high-level reservoir enters the gas storage tunnel under the action of gravity, and the air in the gas storage tunnel and the flexible gas storage airbag is discharged through the gas storage exhaust pipe and the injection and production gas pipe respectively. During the gas charging and energy storage process, the exhaust pipe valve is closed, the high-level reservoir accident maintenance gate, the gas storage reservoir accident maintenance gate, and the injection and production gas control valve remain open, and the ground air compressor injects compressed air into the flexible gas storage bladder through the injection and production gas pipe. The volume of the flexible gas storage bladder increases, and the high-pressure water in the gas storage tunnel is reversely pressed into the high-level reservoir through the pressure water pipeline; During the gas discharge power generation process, the exhaust pipe valve is closed, the high-level reservoir accident maintenance gate, the gas storage reservoir accident maintenance gate, and the injection and production gas control valve remain open, and the high-pressure gas in the flexible gas storage airbag is discharged through the injection and production gas pipe to generate electricity. The volume of the flexible gas storage airbag is reduced, and the water flow in the high-level reservoir enters the gas storage tunnel through the pressure water pipeline; During the inflation and deflation process, the pressure in the flexible air storage bag is maintained in a stable range by controlling the fluctuation of the water level in the high-level reservoir, achieving a constant pressure energy storage effect.

[0030] like Figures 1 to 6 As shown, in this embodiment, an artificial underground constant-pressure gas storage for compressed air energy storage mainly includes a flexible gas storage bag 1; an injection and production gas branch pipe 2; an axial injection and production gas main pipe 3-1; a longitudinal injection and production gas main pipe 3-2; a gas storage exhaust pipe 4; a gas storage exhaust pipe control valve 5; an injection and production gas control valve 6; a pressure water pipeline 7; a gas storage tunnel 8; a flexible air bag fixing rope 9; a gas storage vent pipe 10; a gas storage vent pipe control valve 11; a high-level reservoir 12; an emergency maintenance gate 13 on the high-level reservoir side of the pressure water pipeline; and an emergency maintenance gate 14 on the gas storage side of the pressure water pipeline.

[0031] like Figures 1-3As shown, the cross-sectional shape of the tunnel can be circular, gate-shaped, horseshoe-shaped, or any other shape. After the airbag is inflated, the upper circumferential cross-sectional shape should be consistent with the cross-sectional shape of the tunnel to ensure that the top of the airbag fits better with the tunnel under the action of buoyancy. In this embodiment, the air storage tunnel 8 is circular in cross-section with a radius of 8m and is lined with reinforced concrete. A series of flexible air storage airbags 1 are arranged along the axis of the tunnel. The flexible air storage airbags 1 are capsule-shaped, with a length aligned with the tunnel axis, and a clearance of 1m between each airbag. Each flexible air storage airbag 1 is 30m long and connected to the air storage tunnel 8 by an airbag fixing rope 9. To ensure that the top of the flexible air storage bag 1 fits perfectly within the gas storage tunnel 8 under the action of buoyancy, the circumferential cross-section of the bag 1 is circular at the top and elliptical at the bottom. The radius of the upper circle matches the radius of the gas storage tunnel 8, which is 8 meters. The lower ellipse has a major axis radius of 8 meters and a minor axis radius of 6 meters. The circumferential cross-section of the flexible air storage bag 1 is slightly smaller than the tunnel cross-section to prevent the bag from blocking the normal flow of water in the tunnel when fully inflated. The volume of the air storage bag accounts for 74% of the volume of the gas storage tunnel, which means that the effective gas storage utilization rate of the physical space of the gas storage tunnel is 74%, far exceeding the space utilization rate of 20% to 30% in traditional artificial caverns.

[0032] The flexible air storage bag 1 can be made of materials such as polyvinyl chloride (PVC), high-density polyethylene (HDPE), and thermoplastic polyolefin (TPO). These materials all exhibit good air impermeability, a tensile strength of 200% to 400% at break, and a tensile strength greater than 10 MPa. They also possess excellent elasticity and adaptability. The flexible air storage bag 1 is secured to the air storage tunnel 8 by a bag securing tether 9, preventing it from moving due to the water flow within the tunnel 8. The tether 9 serves only as a limiter and does not exert significant tension on the bag 1. A gas injection and production branch pipe 2 is provided at the top of the flexible gas storage airbag 1, and the gas injection and production branch pipe 2 is connected to the axial gas injection and production main pipe 3-1. The axial gas injection and production main pipe 3-1 is arranged at the top of the tunnel along the tunnel axis and is wrapped with concrete. The gas in the airbag is merged into the axial gas injection and production main pipe 3-1 through the gas injection and production branch pipe 2, and then transported to the ground through the longitudinal gas injection and production main pipe 3-2, and a gas injection and production control valve 6 is provided at the ground end.

[0033] A gas storage exhaust pipe 4 is installed at the top of gas storage tunnel 8 and extends to the ground. An exhaust pipe control valve 5 is installed at the outlet to promptly exhaust air from gas storage tunnel 8 so that high-pressure water can be introduced into the tunnel. When the exhaust pipe control valve 5 detects that the pressure inside gas storage tunnel 8 exceeds a threshold, it automatically opens, exhausting the air inside to balance the pressure and maintain structural stability.

[0034] A pressure water pipe 7 is provided at the bottom of the gas storage tunnel 8, which is connected to the high-level reservoir 12. The pressure water pipe 7 consists of an upper flat section, a first-level vertical shaft, a lower flat section, and a connecting section. The cross-sectional diameter is 2m, and the water flow velocity in the pipe is 4m / s.3 / s, and can be unlined, concrete lined, or reinforced concrete lined. Steel lining can be used in localized sections with poor geological conditions. The pressure water pipeline 7 is equipped with a high-level reservoir emergency maintenance gate 13 on the high-level reservoir side and a gas storage emergency maintenance gate 14 near the gas storage tunnel, for maintenance and emergency braking in the event of an accident. A gas storage vent pipe 10 and a gas storage vent pipe control valve 11 are installed near the bottom of the gas storage tunnel 8. The gas storage vent pipe 10 has a cross-sectional diameter of 1 meter and is connected to the gas storage construction branch tunnel or underground passage. It then extends to the surface through the construction branch tunnel or underground passage. During maintenance, water in the gas storage tunnel 8 and pressure water pipeline 7 is discharged to the surface by gravity or pumping.

[0035] The elevated reservoir 12 can be a natural lake, artificial reservoir, or water tank. Its elevation difference from the gas storage reservoir should be no less than 600 meters to ensure a hydrostatic pressure of no less than 6 MPa within the gas storage tunnel 8 without causing hydraulic fracturing. The water level fluctuation should be no more than 30 meters to ensure that the hydrostatic pressure within the gas storage tunnel 8 remains within 0.3 MPa, with a pressure change rate of less than 5%, achieving pressure stability. The effective storage capacity of the elevated reservoir 12 should be greater than the combined volume of the gas storage tunnel 8, the penstock 7, and evaporation and leakage losses.

[0036] Before inflation and energy storage, the underground gas storage tunnel 8 and the flexible gas storage airbag 1 are filled with normal pressure air. The high-level reservoir accident maintenance gate 13, the gas storage accident maintenance gate 14, the gas storage exhaust pipe control valve 5 and the injection and production gas control valve 6 on the pressure water pipeline are opened. The water flow in the high-level reservoir 12 enters the gas storage tunnel 8 under the action of gravity, and is discharged from the gas storage tunnel 8 and the flexible gas storage airbag 1 through the gas storage exhaust pipe 4 and the injection and production gas branch pipe 2, the axial injection and production gas main pipe 3-1, and the longitudinal injection and production gas main pipe 3-2.

[0037] like Figure 4 、 5 As shown, during the inflation and energy storage process, exhaust pipe valve 5 is closed, high-level reservoir emergency maintenance gate 13, gas storage reservoir emergency maintenance gate 14, and injection and production gas control valve 6 remain open, and the above-ground air compression system injects compressed air into flexible air storage bladder 1 through injection and production gas branch pipe 2, axial injection and production gas main pipe 3-1, and longitudinal injection and production gas main pipe 3-2. The flexible air storage bladder 1 increases in volume, forcing high-pressure water from gas storage tunnel 8 back into high-level reservoir 12 through penstock 7. By controlling the water level fluctuation of high-level reservoir 12, the pressure within flexible air storage bladder 1 can be maintained within a stable range, achieving constant-pressure inflation.

[0038] like Figure 5 、 6As shown, during the deflation power generation process, exhaust pipe valve 5 is closed, while high-level reservoir emergency maintenance gate 13, gas storage reservoir emergency maintenance gate 14, and injection and production gas control valve 6 remain open. High-pressure gas within flexible gas storage bladder 1 is deflated through injection and production gas branch pipe 2, axial injection and production gas main pipe 3-1, and longitudinal injection and production gas main pipe 3-2 to generate electricity. The volume of flexible gas storage bladder 1 decreases, and water from high-level reservoir 12 flows through pressure water pipeline 7 into gas storage tunnel 8. By controlling the amplitude of the water level in high-level reservoir 12, the pressure within flexible gas storage bladder 1 can be maintained within a stable range, achieving a constant-pressure deflation effect.

[0039] During maintenance, the injection and production gas control valve 6 is opened. After the flexible gas storage bag 1 is completely deflated, the pressure water pipeline emergency maintenance gate 13 or 14 is closed, and the exhaust pipe control valve 5 and vent pipe control valve 10 are opened to drain the water from the pressure water pipeline 7 and the gas storage tunnel 8 through the gas storage vent pipe 10, allowing maintenance to proceed. When the gas storage is rapidly emptied (such as during emergency pressure relief or maintenance), if the tunnel water is pumped out and no air enters, the internal pressure may drop suddenly, potentially forming a vacuum (negative pressure). The exhaust pipe control valve 5 automatically opens when it detects that the internal pressure of the gas storage falls below a threshold, drawing in external air to balance the pressure and maintain structural stability.

[0040] Based on the description and drawings of the present invention, those skilled in the art can easily manufacture or use the artificial underground constant pressure gas storage structure for compressed air energy storage of the present invention, and can produce the positive effects described in the present invention.

[0041] Unless otherwise specified, in the present invention, if there are terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", etc. indicating orientation or positional relationships, they are based on the orientation or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the orientation or positional relationships in the present invention are only used for illustrative purposes and cannot be understood as limiting this patent. For those skilled in the art, the specific meanings of the above terms can be understood in conjunction with the accompanying drawings and according to specific circumstances.

[0042] Unless otherwise specified or limited, the terms "disposed," "connected," and "connected" in this disclosure should be interpreted broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal connections between two components. Those skilled in the art will understand the specific meanings of these terms in this disclosure based on the specific circumstances.

[0043] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A constant pressure compressed air energy storage system, characterized by: It includes a gas storage tunnel (8), a pressure water pipeline (7) and a high-level reservoir (12), wherein the elevation of the high-level reservoir (12) is greater than the elevation of the gas storage tunnel (8); The internal space of the gas storage tunnel (8) is in the form of a tunnel. A flexible gas storage bag (1) is provided along the axis of the gas storage tunnel (8) for storing compressed high-pressure gas. The top of the flexible gas storage bag (1) is fitted with the top of the gas storage tunnel (8). An injection and production gas pipe communicating with the flexible gas storage bag (1) is provided at the top of the gas storage tunnel (8). The other end of the injection and production gas pipe is communicated with an air compressor located on the ground. The bottom of the gas storage tunnel (8) is connected to the high-level water reservoir (12) through a pressure water pipeline (7). The pressure water pipeline (7) introduces the water flow in the high-level water reservoir (12) into the gas storage tunnel (8), and utilizes the hydrostatic pressure to balance the internal pressure of the flexible gas storage airbag (1) to achieve a constant pressure gas storage effect of the gas storage system.

2. A constant pressure compressed air energy storage system according to claim 1, characterized in that: When the flexible air storage airbag is fully inflated, the upper part of the circumferential section is circular and the lower part is elliptical. The radius of the upper circle is consistent with the radius of the circular section of the gas storage tunnel to ensure that the top of the flexible air storage airbag is tightly fitted with the top of the gas storage tunnel under the action of buoyancy; the upper part of the flexible air storage airbag is provided with an opening connected to the injection and production gas pipe; the radius of the major axis of the lower ellipse is consistent with the radius of the upper circle, and the circumferential section size of the flexible air storage airbag is slightly smaller than the section size of the gas storage tunnel, which is used to prevent the flexible air storage airbag from blocking the normal flow of water in the gas storage tunnel after it is fully inflated.

3. A constant pressure compressed air energy storage system according to claim 2, characterized in that: The volume of the flexible gas storage airbag after full inflation accounts for 74% of the volume of the gas storage tunnel, that is, the effective gas storage utilization rate of the physical space of the gas storage tunnel is 74%.

4. A constant pressure compressed air energy storage system according to claim 3, characterized in that: There are multiple flexible air storage bags arranged along the axis of the air storage tunnel. Each flexible air storage bag is capsule-shaped, and the length direction of the capsule is consistent with the axis of the air storage tunnel. A net distance of 1m is maintained between two adjacent flexible air storage bags.

5. A constant pressure compressed air energy storage system according to claim 4, characterized in that: The flexible air storage airbag is fixed to the top of the air storage tunnel by an airbag fixing rope to prevent the flexible air storage airbag from moving under the action of water flow inside the air storage tunnel. The airbag fixing rope only plays a limiting role and does not generate a large pulling force on the flexible air storage airbag.

6. The constant pressure compressed air energy storage system according to claim 1, characterized in that: The injection and production gas pipe includes an injection and production gas branch pipe, an axial injection and production gas main pipe, and a longitudinal injection and production gas main pipe that are interconnected. The injection and production gas branch pipe is arranged at the top of the flexible gas storage airbag and is connected to the top opening of the flexible gas storage airbag; the axial injection and production gas main pipe is arranged at the top of the gas storage tunnel along the axial direction of the gas storage tunnel and is connected to the injection and production gas branch pipe; the longitudinal injection and production gas main pipe is arranged at the top of the gas storage tunnel along the longitudinal direction of the gas storage tunnel and is connected to the axial injection and production gas main pipe. The end of the longitudinal injection and production gas main pipe is connected to the air compressor located on the ground, and an injection and production gas control valve is provided at the ground end of the longitudinal injection and production gas main pipe.

7. The constant pressure compressed air energy storage system according to claim 1, characterized in that: A gas storage exhaust pipe connected to the top of the gas storage tunnel is also provided. The end of the gas storage exhaust pipe extends to the ground, and an exhaust pipe control valve is provided at the outlet end to discharge the air in the gas storage tunnel.

8. The constant pressure compressed air energy storage system according to claim 1, characterized in that: The pressure water supply pipeline is Z-shaped and is provided with a high-level reservoir accident maintenance gate and a gas storage reservoir accident maintenance gate. The high-level reservoir accident maintenance gate is located on the water flow outlet side of the high-level reservoir, and the gas storage reservoir accident maintenance gate is located on the water flow inlet side of the gas storage reservoir tunnel.

9. The constant pressure compressed air energy storage system according to claim 1, characterized in that: A gas storage vent pipe is provided below the gas storage tunnel and is connected to the bottom of the gas storage tunnel and the pressure water pipeline respectively. A gas storage vent pipe control valve is provided on the gas storage vent pipe. The gas storage vent pipe is connected to the gas storage construction branch tunnel or underground passage, and extends to the ground through the construction branch tunnel or underground passage. During maintenance, the water in the gas storage tunnel and the pressure water pipeline is discharged to the ground by gravity or pumping.

10. A gas storage method based on the constant pressure compressed air energy storage system according to any one of claims 1 to 9, characterized in that: The following steps are involved: Before the gas is inflated and stored, the underground gas storage reservoir and the gas storage airbag contain normal pressure air. The high-level reservoir accident maintenance gate (13), the gas storage reservoir accident maintenance gate (14), the exhaust pipe valve (5) and the injection and production gas control valve (6) on the pressure water pipeline are opened respectively. The water flow in the high-level reservoir (12) enters the gas storage reservoir tunnel (8) under the action of gravity, and the air in the gas storage reservoir tunnel (8) and the flexible gas storage airbag (1) is discharged respectively through the gas storage reservoir exhaust pipe (4) and the injection and production gas pipe; During the gas charging and energy storage process, the exhaust pipe valve (5) is closed, the high-level reservoir accident maintenance gate (13), the gas storage reservoir accident maintenance gate (14), and the injection and production gas control valve (6) are kept open, and the ground air compressor injects compressed air into the flexible gas storage airbag (1) through the injection and production air pipe. The volume of the flexible gas storage airbag (1) increases, and the high-pressure water in the gas storage tunnel (8) is reversely pressed into the high-level reservoir (12) through the pressure water pipeline (7); During the gas discharge power generation process, the exhaust pipe valve (5) is closed, the high-level reservoir accident maintenance gate (13), the gas storage reservoir accident maintenance gate (14), and the injection and production gas control valve (6) remain open, and the high-pressure gas in the flexible gas storage airbag (1) is discharged through the injection and production gas pipe to generate electricity, the volume of the flexible gas storage airbag (1) is reduced, and the water flow in the high-level reservoir (12) enters the gas storage reservoir tunnel (8) through the pressure water pipeline (7); During the inflation and deflation process, the pressure in the flexible air storage bag (1) is maintained within a stable range by controlling the water level fluctuation of the high-level water reservoir (12), thereby achieving a constant-pressure energy storage effect.

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