A compressed air energy storage system based on in-service sealed pipelines and its operation method
By constructing a segmented gas injection and extraction structure and a heat recovery mechanism in an in-service sealed natural gas pipeline, the problems of site selection and pressure drop along the pipeline in traditional energy storage systems have been solved, and efficient and economical compressed air energy storage operation has been achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING UNIV OF TECH
- Filing Date
- 2026-04-23
- Publication Date
- 2026-06-02
AI Technical Summary
Traditional compressed air energy storage systems rely on underground salt caverns or abandoned mines as storage spaces, which leads to problems such as limited site selection, long construction periods, and high costs. Furthermore, the pressure drop along long-distance pipelines results in low energy storage capacity and efficiency.
Using in-service sealed natural gas pipelines as gas storage space, the system employs a segmented gas injection and extraction method, combined with multi-stage compression and heat recovery, to reduce pressure drop along the pipeline and construct a segmented gas distribution structure.
It has achieved reduced construction costs, improved the efficiency and energy utilization of energy storage systems, delayed pipeline corrosion and deterioration, increased power generation capacity, and compatibility with new energy consumption and grid peak shaving and valley filling.
Smart Images
Figure CN122129329A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of compressed air energy storage technology, and relates to a compressed air energy storage system and its operation method based on in-service sealed pipelines. Background Technology
[0002] With the rapid development of new energy power generation (such as wind power and photovoltaics), their intermittency and volatility have placed higher demands on the stable operation of the power grid, making energy storage technology a key support means. Among them, compressed air energy storage technology has attracted widespread attention due to its advantages such as large capacity, long lifespan, and low cost.
[0003] Traditional compressed air energy storage systems typically rely on underground salt caverns and abandoned mines as storage spaces, but these methods suffer from limitations in site selection, long construction periods, and high costs. With the continuous adjustment of natural gas transmission and distribution networks and the transformation of the energy structure, a large number of natural gas pipelines are being converted into in-service storage due to gas source depletion, route optimization, or safety operation requirements. These pipelines are usually constructed to high design pressure and safety standards, possessing excellent mechanical properties and complete supporting facilities. Direct abandonment would result in a significant waste of engineering resources; therefore, in-service stored natural gas pipelines have the potential to be converted into gas storage carriers.
[0004] Considering the pressure drop along the pipeline for long-distance gas storage, failure to take appropriate measures will reduce the energy storage capacity and decrease the round-trip efficiency.
[0005] To address the aforementioned technical issues, we will continue to provide a compressed air energy storage system that reduces construction costs and pressure drop along the pipeline. Summary of the Invention
[0006] To address the aforementioned problems, this invention provides a compressed air energy storage system and its operation method based on an in-service sealed pipeline. The system uses an in-service sealed energy storage pipeline as the gas storage space, reducing construction costs, and reduces pressure drop along the pipeline through a segmented gas injection and segmented gas extraction operation method.
[0007] To achieve the above objectives, the present invention provides a compressed air energy storage system based on an in-service sealed pipeline, comprising: a compressed energy storage subsystem and a pipeline gas storage subsystem; The compressed energy storage subsystem includes a multi-stage compression unit, a heat exchange unit, and an expansion power generation unit. The pipeline gas storage subsystem includes in-service sealed pipelines, valve assemblies, and segmented gas distribution units; The segmented gas distribution unit is connected to multiple gas injection points and gas intake points of the in-service sealed pipeline through multiple branch pipelines, forming a segmented gas injection and segmented gas intake gas distribution structure. During energy storage, the multi-stage compression unit compresses air to generate high-temperature and high-pressure air. The heat of compression in the high-temperature and high-pressure air is recovered and stored by the heat exchange unit. The cooled high-pressure air is injected into the in-service storage pipeline in stages by the segmented gas distribution unit for storage. During energy release, the compressed air in the in-service storage pipeline is taken out in stages by the segmented gas distribution unit and transported to the expansion power generation unit to complete power generation.
[0008] As a further improvement of the present invention, the multi-stage compression unit includes at least two air compressors and a drive motor connected in series; the heat storage and exchange unit includes an intercooler heat exchange unit, which includes multiple intercooler groups, a low-temperature heat storage tank and a high-temperature heat storage tank. The intercooler group includes a low-temperature intercooler, a high-temperature intercooler, one intercooler or multiple intercoolers connected in series, and the intercooler is a water intercooler, a molten salt intercooler or a thermal oil intercooler; each air compressor is connected in series with each intercooler alternately, the output end of the low-temperature heat storage tank is connected to the input end of each intercooler, and the output end of each intercooler is connected to the high-temperature heat storage tank. During energy storage, the drive motor drives each air compressor to compress air. The first air compressor sequentially feeds the compressed air into each intercooler of the first intercooler group. The heat storage medium of each intercooler absorbs the heat of compression of the compressed air and outputs it to the high-temperature heat storage tank. The cooled compressed air is then fed into the second compressor. The air compressed by the second compressor enters the second intercooler group. The heat storage medium of each intercooler in the second intercooler group absorbs the heat of compression of the compressed air and outputs it to the high-temperature heat storage tank. This process continues until the last intercooler outputs high-pressure air to the pipeline gas storage subsystem.
[0009] As a further improvement of the present invention, each intercooler outlet is equipped with a temperature monitor. When the temperature of the heat storage medium in the corresponding intercooler reaches a preset value, the heat storage medium is output to the high-temperature heat storage tank.
[0010] As a further improvement of the present invention, a pressure monitor is installed at the outlet of the last intercooler. When the air pressure is detected to reach the preset injection pressure, high-pressure air is output to the pipeline storage subsystem.
[0011] As a further improvement of the present invention, the expansion power generation unit includes at least two expansion units and a generator connected in series; the heat storage and exchange unit further includes a reheat heat exchange unit, which includes at least two reheater groups, a high-temperature heat storage tank and a low-temperature heat storage tank. The reheater group includes one or more reheaters connected in series, and the reheater is a water reheater, a thermal oil reheater or a molten salt reheater; each reheater group is alternately connected in series with each expansion unit, the output end of the high-temperature heat storage tank is connected to the input end of each reheater, and the output end of each reheater is connected to the low-temperature heat storage tank. When energy is released, the heat storage medium in the high-temperature heat storage tank enters each reheater of the first reheater group, and the high-pressure air of the pipeline gas storage subsystem enters each reheater in sequence. It is heated by the heat storage medium, and the cooled heat storage medium is output to the low-temperature heat storage tank for recycling. The heated high-pressure air enters the expander unit to do work, and then enters the next stage reheater. The output power of each expander unit jointly drives the generator to generate electricity.
[0012] As a further improvement of the present invention, the segmented gas distribution unit includes an injection manifold, multiple injection branch pipes, an in-service sealed gas storage pipeline, multiple gas intake branch pipes, and a gas intake manifold connected in sequence. The injection manifold and the gas intake manifold are both arranged in a bypass coupling arrangement with the in-service sealed pipeline. The gas inlet of the injection manifold is connected to a compression unit, and the gas outlet of the gas intake manifold is connected to an expansion power generation unit. Multiple gas injection branch lines introduce high-pressure air from the gas injection manifold into the in-service sealed gas storage pipeline through each gas injection point, and multiple gas extraction branch lines extract high-pressure gas from each gas extraction point of the in-service sealed gas storage pipeline to the gas extraction manifold.
[0013] As a further improvement of the present invention, the valve assembly is provided on both the gas injection branch pipeline and the gas intake branch pipeline, and the valve assembly includes at least a regulating valve, a check valve and a shut-off valve.
[0014] As a further improvement of the present invention, during the energy storage process, multiple gas injection points simultaneously inject gas into different positions of the in-service sealed pipeline, and the gas flow rate in the pipeline gradually increases along the pipeline.
[0015] As a further improvement of the present invention, during the energy release process, multiple gas sampling points simultaneously draw gas from different locations in the in-service sealed pipeline, and the gas flow rate in the pipeline gradually decreases along the pipeline.
[0016] The present invention also provides an operation method for a compressed air energy storage system based on an in-service sealed pipeline, including an energy storage stage and an energy release stage; The energy storage stage includes: multi-stage compression unit compressing air, compression heat being recovered and stored by heat exchange unit, and compressed air being injected into in-service sealed pipelines simultaneously and in segments at multiple points by segmented gas distribution unit, transforming single long-distance high-flow gas transmission into multi-segment short-distance low-flow gas transmission, reducing pressure drop along the pipeline; The energy release stage includes: compressed air in the in-service sealed pipeline is extracted synchronously in multiple sections by the segmented gas distribution unit, collected and reheated by the heat storage and heat exchange unit, and then enters the expansion power generation unit to generate electricity.
[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses in-service sealed pipelines as gas storage carriers, combining segmented gas injection and segmented gas extraction structures with a compression heat recovery and utilization mechanism. It eliminates the need to build new dedicated gas storage facilities, significantly reducing the investment and construction cycle of energy storage systems. At the same time, it solves the problems of large pressure drop and low energy utilization along long-distance pipeline gas storage, realizing the efficient reuse of idle pipeline resources.
[0018] This invention transforms traditional single-point, high-flow, long-distance gas transmission into multi-point, low-flow, short-distance gas transmission by using a segmented gas injection and extraction method. This significantly reduces pipeline friction loss, increases energy storage capacity and system round-trip efficiency, and enables safe, efficient, and economical compressed air energy storage operation.
[0019] This invention employs an alternating series connection structure of the compressor and intercooler group, combined with online temperature and pressure monitoring, which can recover the heat of compression in stages, avoid high temperature damage to equipment, accurately control the gas storage pressure and temperature, improve the stability of the compression process and the efficiency of heat recovery, and ensure the continuous and reliable operation of the system.
[0020] This invention achieves interstage reheat by alternating series connection of reheater units and expander units. It utilizes the stored heat of compression to heat the air before it expands and does work, thereby increasing power generation capacity without the need for external combustion, improving energy recycling efficiency, and enhancing system power generation efficiency and output stability.
[0021] The present invention employs a bypass coupling arrangement for the gas injection / extraction manifold, which is combined with multiple branches and regulating valves, check valves, and shut-off valve groups. This does not damage the original pipeline structure and allows for flexible segmented gas filling and releasing, ensuring that the flow rate in the pipeline increases or decreases smoothly along the pipeline, further reducing pressure loss and improving operational safety, while also delaying the corrosion and deterioration of the pipeline when it is idle. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of a compressed air energy storage system based on an in-service sealed pipeline, as disclosed in one embodiment of the present invention. Figure 2 This is a schematic diagram of a segmented gas injection structure disclosed in one embodiment of the present invention; Figure 3 This is a schematic diagram of a segmented gas extraction structure disclosed in one embodiment of the present invention.
[0023] Explanation of reference numerals in the attached figures: 1. Drive motor; 2. Low-pressure compressor; 3. High-pressure compressor; 4. First intercooler unit; 5. Second intercooler unit; 6. Air dehumidification device; 7. Low-temperature heat storage tank; 8. First heat storage medium pump; 9. High-temperature heat storage tank; 10. Second heat storage medium pump; 11. Gas injection manifold; 12. In-service sealed gas storage pipeline; 13. Gas intake manifold; 14. First reheater unit; 15. First expander unit; 16. Second reheater unit; 17. Second expander unit; 18. Generator; 19. Regulating valve; 20. Shut-off valve; 21. Check valve. Detailed Implementation
[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0025] The present invention will now be described in further detail with reference to the accompanying drawings: like Figure 1 As shown, the present invention provides a compressed air energy storage system based on an in-service sealed pipeline, comprising: a compressed energy storage subsystem and a pipeline gas storage subsystem; The compressed energy storage subsystem includes a multi-stage compression unit, a heat exchange unit, and an expansion power generation unit; The pipeline gas storage subsystem includes in-service sealed pipelines, valve assemblies, and segmented gas distribution units; The segmented gas distribution unit is connected to multiple gas injection and gas intake points of the in-service sealed pipeline through multiple branch pipelines, forming a segmented gas injection and segmented gas intake gas distribution structure. During energy storage, multi-stage compression units compress air to generate high-pressure air. The heat of compression in the high-pressure air is recovered and stored by the heat exchange unit. The cooled high-pressure air is then injected into the in-service sealed pipeline in stages via the segmented gas distribution unit for storage. During energy release, the compressed air in the in-service sealed pipeline is extracted in stages via the segmented gas distribution unit and transported to the expansion power generation unit to complete power generation. This invention achieves efficient storage and release of compressed air through a dual-core subsystem and a segmented gas distribution unit, while simultaneously recovering and reusing the heat of compression. This significantly improves the system's energy storage density and power generation efficiency, avoiding the problems of large pressure drop and low efficiency in traditional long-pipeline gas storage.
[0026] Specifically, the compressed energy storage subsystem and the pipeline gas storage subsystem are independent but tightly coupled functional modules. The segmented gas distribution unit is equipped with multiple gas injection points and gas intake points at intervals along the axial direction of the in-service sealed pipeline. The gas injection points and gas intake points are arranged alternately, with the same or different numbers. The branch pipelines are connected to the in-service sealed pipelines with detachable flanges to facilitate the subsequent restoration of pipeline functions.
[0027] In some embodiments, the multi-stage compression unit includes at least two air compressors connected in series and a drive motor 1. The air compressors include a low-pressure compressor 2 and a high-pressure compressor 3. The heat storage and exchange unit includes an intercooler heat exchange unit, which includes multiple intercooler groups, a low-temperature heat storage tank 7, and a high-temperature heat storage tank 9. The intercooler group includes one or more intercoolers connected in series, and the intercooler can be a water intercooler, a molten salt intercooler, or a thermal oil intercooler. Each air compressor and each intercooler group are connected in series alternately. At the same time, when the air temperature output by the air compressor is high, the intercooler group preferentially uses molten salt intercooling. The system employs either a water-cooled intercooler or a thermal oil-cooled intercooler. When the air temperature output from the air compressor is not high, the intercooler group preferentially uses a water-cooled intercooler. The output end of the low-temperature heat storage tank 7 is connected to the input end of each intercooler, and the output end of each intercooler is connected to the high-temperature heat storage tank 9. Furthermore, each intercooler outlet is equipped with a temperature monitor. When the temperature of the heat storage medium in the corresponding intercooler reaches a preset value, the heat storage medium is output to the high-temperature heat storage tank 9. A pressure monitor is installed at the outlet of the last intercooler in the last intercooler group. When the air pressure is detected to reach the preset injection pressure, high-pressure air is output to the pipeline air storage subsystem. This invention uses an alternating series structure to achieve interstage cooling, avoiding damage to the equipment due to excessively high compressed air temperature. At the same time, it accurately recovers the heat of compression, and dual monitoring of temperature and pressure ensures the safe and stable operation of the system.
[0028] During energy storage, drive motor 1 drives each air compressor to compress air. The first air compressor sequentially feeds the compressed air into each intercooler of the first intercooler group 4. The first heat storage medium pump 8 pumps the heat storage medium from the low-temperature heat storage tank 7 into each intercooler of the first intercooler group 4. In each intercooler of the first intercooler group 4, the heat storage medium absorbs the heat of compression of the compressed air and enters the high-temperature heat storage tank 9. The cooled compressed air is then fed into the second compressor. The air compressed by the second compressor enters the second intercooler group 5. In each intercooler of the second intercooler group 5, the heat storage medium absorbs the heat of compression of the compressed air and outputs it to the high-temperature heat storage tank 9. This process continues until the last intercooler of the last intercooler group outputs high-pressure air to the pipeline air storage subsystem. This invention employs multi-stage compression combined with step-by-step cooling to reduce the single-stage compression load, improve compression efficiency, achieve full-process recovery of compression heat, eliminate heat waste, and improve the overall energy utilization rate of the system.
[0029] Specifically, both the low-pressure compressor 2 and the high-pressure compressor 3 are centrifugal or screw type, and the drive motor 1 is a variable frequency speed control motor, which can adjust the compression power according to the energy storage requirements; the intercooler is a shell and tube heat exchanger, with air flowing through the tube side and the heat storage medium flowing through the shell side, and the heat exchange area matching the rated discharge capacity of the compressor; the temperature monitor and the pressure monitor are both connected to the system control cabinet to realize automatic adjustment and interlock protection. The heat storage medium can be water, thermal oil, or molten salt. For low-temperature heat storage (where the air temperature is not high after compression by the air compressor), each intercooler group can use one water intercooler. For high-temperature heat storage (where the air temperature is high after compression by the air compressor), each intercooler group can use multiple water intercoolers in series, multiple molten salt intercoolers in series, or multiple thermal oil intercoolers in series. Alternatively, in a preferred configuration, the first intercooler connected to the preceding air compressor in each intercooler group uses a molten salt or thermal oil intercooler, while subsequent intercoolers use water intercoolers. Molten salt and thermal oil intercoolers can better absorb and reduce heat from the high-temperature air. After the air is cooled significantly, it can be cooled again by a water cooler. In this case, multiple sets of different low-temperature heat storage tanks, high-temperature heat storage tanks and connecting pipelines are required to store the corresponding heat storage medium. At the same time, a reheater with the corresponding heat storage medium can be configured in the reheater group to realize the closed loop of heat storage and heat release. In the cooler, the heat storage medium and compressed air exchange heat in a countercurrent manner. After heat exchange, the heat storage medium with the qualified temperature flows into the high-temperature heat storage tank 9 through the automatic control valve, and the medium that does not meet the qualified temperature flows back to the low-temperature heat storage tank 7 for recirculation. The last cooler is also equipped with an air dehumidification device 6 to remove moisture from the high-pressure air and prevent corrosion of the inner wall of the in-service sealed pipeline.
[0030] In other embodiments, the expansion power generation unit includes at least two series-connected expander units and generator 18, each expander unit including multiple expanders; the heat storage and exchange unit also includes a reheat heat exchange unit, which includes multiple reheater groups, a high-temperature heat storage tank 9, and a low-temperature heat storage tank 7. Each reheater group includes one or more reheaters connected in series, including water reheaters, thermal oil reheaters, or molten salt reheaters. Each reheater group is alternately connected in series with each expander unit. Each reheater group can use multiple reheaters with the same heat storage medium connected in series, such as water reheaters, or it can use different heat storage media. Reheaters are connected in series, such as molten salt reheaters connected in series with water reheaters, or thermal oil reheaters connected in series with water reheaters. Only when the intercooler group of this system includes intercoolers with multiple heat storage media can the reheater group adopt the corresponding series connection of reheaters with multiple heat storage media to achieve a closed loop of heat storage and heat release. The output end of the high-temperature heat storage tank 9 is connected to the input end of each reheater, and the output end of each reheater is connected to the low-temperature heat storage tank 7. In this invention, the expander unit and the reheater group are alternately connected in series to achieve interstage reheating, improve the air expansion work capacity, and the heat storage media are used in a closed loop, further improving the power generation efficiency and the system energy round-trip efficiency.
[0031] During energy release, the heat storage medium in the high-temperature heat storage tank 9 is pumped into each reheater of each reheater group via the second heat storage medium pump 10. High-pressure air from the pipeline gas storage subsystem is sequentially passed into each reheater of the reheater group for reheating. The cooled heat storage medium is then output to the low-temperature heat storage tank for recycling. Each reheater group has the same function, and so on. The heated high-pressure air output from each reheater group enters each expander of each expander group to perform work. The output power of each expander group collectively drives the generator 18. The generator 18 is further connected to a grid connection device, which connects the generated power to the power grid. This process utilizes the stored heat of compression to reheat the air, eliminating the need for additional fuel consumption and achieving clean and efficient power generation. The grid connection device ensures stable power grid connection, adapting to new energy consumption scenarios.
[0032] Specifically, the expander adopts an axial or centripetal air turbine, and the reheater is also a shell-and-tube heat exchanger, with the high-temperature heat storage medium flowing through the shell side and the high-pressure air flowing through the tube side. Both the high-temperature heat storage tank 9 and the low-temperature heat storage tank 7 adopt thermal insulation structures to reduce heat loss. After the high-pressure air is heated to the set temperature by the reheater, it enters the expander and expands in stages to do work. The output shaft of the expander is directly connected to the rotor of the generator 18. The grid connection device has voltage regulation, frequency regulation, and synchronous grid connection functions, and can be adapted to different grid access requirements.
[0033] In this invention, the in-service sealed pipeline is a conveying pipeline that has completed construction and non-destructive testing. Before being put into operation, an adaptability assessment of pressure resistance margin, fatigue life, and sealing reliability must be completed. Through a special adaptability assessment, it is ensured that the in-service sealed pipeline meets the operational requirements of periodic charging and discharging of compressed air, avoids the risk of pipeline failure, and ensures the safety of gas storage.
[0034] In some embodiments, such as Figure 2 , 3 As shown, the segmented gas distribution unit includes, in sequence, an injection manifold 11, multiple injection branch lines, an in-service sealed gas storage pipeline 12, multiple gas intake branch lines, and a gas intake manifold 13. Both the injection manifold 11 and the gas intake manifold 13 are arranged in a bypass coupling configuration with the in-service sealed pipeline. The inlet of the injection manifold 11 is connected to the compression unit, and the outlet of the gas intake manifold 13 is connected to the expansion power generation unit. Figure 2 As shown, multiple gas injection branch lines introduce the high-pressure air in the gas injection manifold 11 into the in-service sealed gas storage pipeline 12 through various gas injection points, such as... Figure 3 As shown, multiple gas intake branch pipelines extract high-pressure gas from each gas intake point of the in-service sealed gas storage pipeline 12 and deliver it to the gas intake manifold 13; among them, such as Figure 2 , 3As shown, valve assemblies are installed on both the gas injection branch pipeline and the gas intake branch pipeline. The valve assemblies include at least a regulating valve 19, a check valve 21, and a shut-off valve 20. This invention adopts a bypass coupling arrangement that does not damage the original pipeline structure. The branch pipelines, in conjunction with the valve assemblies, achieve precise gas distribution and safety protection. The gas injection and gas intake paths are independent and do not interfere with each other, thereby improving gas distribution efficiency and operational flexibility.
[0035] Furthermore, this invention utilizes in-service sealed pipelines for gas storage, controlling the on / off state of valve components to construct multiple relatively independent yet collaboratively working gas storage units, achieving flexible adjustment of energy storage capacity. During energy storage, multiple injection points simultaneously inject gas into different locations within the in-service sealed pipeline, with the gas flow rate gradually increasing along the pipeline's path. During energy release, multiple extraction points simultaneously extract gas from different locations within the in-service sealed pipeline, with the gas flow rate gradually decreasing along the pipeline's path. This invention transforms single long-distance, high-flow-rate gas transmission into multi-segment, short-distance, low-flow-rate gas transmission, significantly reducing friction loss along the pipeline. Actual measurements show that friction loss can be reduced by more than 45%, significantly improving energy storage capacity and system efficiency.
[0036] Specifically, the gas injection manifold 11 and gas intake manifold 13 have larger diameters than the in-service storage pipeline, shorter lengths, and lower flow resistance; the regulating valve 19 is used to regulate the gas flow rate, the check valve 21 prevents gas backflow, and the shut-off valve 20 is used for equipment maintenance and fault isolation. All valves are pneumatic or electric automatic control valves, enabling remote control. During energy storage, the gas injection points are evenly distributed along the pipeline axis, and the gas injection volume at each injection point is proportionally allocated, causing the flow rate in the pipeline to increase steadily along the pipeline. During energy release, the gas intake points correspond to the gas injection points, and the gas intake volume at each intake point increases progressively, causing the flow rate in the pipeline to decrease steadily along the pipeline.
[0037] The present invention provides an operation method for a compressed air energy storage system based on an in-service sealed pipeline, comprising an energy storage stage and an energy release stage; The energy storage stage includes: multi-stage compression unit compresses air, compression heat is recovered and stored through heat exchange unit, and compressed air is injected into in-service sealed pipelines at multiple points synchronously and in segments through segmented gas distribution unit, which transforms single long-distance large-flow gas transmission into multi-segment short-distance small-flow gas transmission and reduces pressure drop along the pipeline. The energy release phase includes: compressed air in the in-service sealed pipeline is extracted in multiple synchronous sections by the segmented gas distribution unit, collected and reheated by the heat storage and heat exchange unit, and then enters the expansion power generation unit to generate electricity.
[0038] This invention features staggered operation of the energy storage and release phases. The energy storage phase prioritizes consuming off-peak electricity or curtailed renewable energy, while the release phase generates electricity during peak demand, achieving peak shaving and valley filling for the power grid. By constructing a multi-node distributed gas storage network, the invention can flexibly adjust the energy storage capacity. Valve components control the gas storage volume of in-service sealed pipelines, adjusting the operating pipeline sections according to renewable energy output and load demand. When wind and solar output is low, smaller-volume pipelines are used to reach the target pressure more quickly; when wind and solar power generation is sufficient, the system stores gas in the entire pipeline to reduce wind and solar curtailment. During operation, the system monitors pipeline pressure, medium temperature, and gas flow in real time, automatically adjusting the opening of valve 19 and equipment power to ensure stable operation throughout the entire process. This operation method fully utilizes idle pipeline resources, reduces investment in gas storage facility construction, and solves the problem of pressure drop in long pipeline gas storage, balancing economy, safety, and efficiency, and has broad engineering application prospects. Example 1:
[0039] The present invention discloses a complete working process of a compressed air energy storage system based on an in-service sealed pipeline during the energy storage phase, wherein both the first and second intercooler groups employ a water intercooler, specifically including: Step 1: Drive motor 1 is powered on and runs, coaxially driving the first compressor (low-pressure compressor 2) and the second compressor (high-pressure compressor 3) to work. After the outside air is initially compressed by the first compressor (low-pressure compressor 2), it enters the first intercooler group 4. Step 2: The heat storage medium water in the low temperature heat storage tank 7 flows into the water cooler of the first cooler group 4 under the action of the first heat storage medium pump 8, absorbs the heat of the initially compressed air, and after the air is cooled down, it enters the second compressor for compression again. Step 3: The high-temperature air, after being pressurized by the second compressor (high-pressure compressor 3), enters the second intercooler group 5. The heat storage medium water in the low-temperature heat storage tank 7 flows into the water intercooler of the second intercooler group 5 to absorb heat, thereby further cooling the air. Step 4: After absorbing the heat of compression, the temperature of the heat storage medium rises and flows into the high-temperature heat storage tank 9 to complete the heat storage. Step 5: After cooling and drying, the high-pressure air enters the air dehumidification device 6 for dehydration treatment, and then flows into the air injection manifold 11. Step 6: The gas injection manifold 11 injects high-pressure air into the in-service storage pipeline in sections and simultaneously through multiple gas injection branch pipelines. Step 7: The regulating valve 19, shut-off valve 20, and check valve 21 of each gas injection branch work together to control the gas injection flow rate and prevent gas backflow. The air flow rate in the pipeline gradually increases along the pipeline. Step 8: Continue to inject gas in stages until the pressure inside the pipeline reaches the set upper limit, and the energy storage process is completed.
[0040] This embodiment is applicable to low-temperature thermal storage, that is, when the temperature of the high-temperature and high-pressure air output by the air compressor is within the thermal storage range of water (such as 20~90 degrees Celsius), this embodiment can realize compressed air energy storage; corresponding to this energy storage stage, the first reheater group and the second reheater group in the system can both use a water reheater.
[0041] Specifically, to verify the effect of segmented gas injection on reducing pressure drop along the pipeline, the following example is used for pressure loss analysis: An in-service sealed gas storage pipeline 12 is taken as the gas storage device, with a length of 103.7 km and a diameter of 0.813 m. The air mass flow rate during energy storage is... .
[0042] The pressure loss in a pipeline is calculated based on the Darcy-Weisbach formula, which is as follows:
[0043] Combining the continuity equation:
[0044] get:
[0045] Assuming the injection rates at three points at a certain moment are 40 kg / s, 50 kg / s, and 60 kg / s respectively, the actual air mass flow rates in each pipe section are shown in Table 1: Table 1
[0046] because Then the first segment (0-30km):
[0047] Second section (30-60km):
[0048] Section 3 (60-103.7km):
[0049] Total pressure drop:
[0050] Compared to single-point gas injection:
[0051] The pressure drop reduction percentage is:
[0052] This indicates that adopting a segmented gas injection operation mode can reduce the pressure drop along the pipeline by approximately (1-0.546)×100%=45%, significantly improving the pipeline gas transmission conditions.
[0053] Assuming the gas extraction ratio at a certain moment is as follows: 30% is taken from the front section, 40% is taken from the middle section, and 30% remains in the rear section, then the flow distribution in the manifold 13 is shown in Table 2:
[0054] According to the formula Therefore, pressure loss is equal to the square of flow rate. The pressure loss of the manifold is reduced to 53% of the pressure loss during full flow.
[0055] Example 2: This invention discloses the complete working process of a compressed air energy storage system based on an in-service sealed pipeline during the energy release phase. In this system, both the first and second reheater groups employ a water reheater and a molten salt reheater connected in series, with the water reheater preceding the molten salt reheater. Correspondingly, in this embodiment, both the first and second intercooler groups in the energy storage phase employ a molten salt intercooler and a water intercooler connected in series, with the molten salt intercooler preceding the water intercooler. The system is equipped with two sets of thermal storage medium circulation subsystems, namely a water circulation subsystem. The subsystem comprises a molten salt circulation subsystem and a water circulation subsystem, including a low-temperature water storage tank, a high-temperature water storage tank, a first water pump, a second water pump, and supporting pipelines. The low-temperature water storage tank is connected to the input terminals of each water intercooler, the output terminals of each water intercooler are connected to the high-temperature water storage tank, the high-temperature water storage tank is connected to the input terminals of each water reheater, and the output terminals of each water reheater are connected to the low-temperature water storage tank. The connection method of the molten salt circulation subsystem is the same as that of the water circulation subsystem. The heat storage process of this system is similar to that in Example 1 and will not be described again. The energy release process specifically includes: Step 1: Open the shut-off valve 20 and regulating valve 19 of each gas intake branch of the in-service sealed pipeline, and high-pressure air is taken out in sections and synchronously from multiple gas intake points. Step 2: The high-pressure air taken out from each branch is collected into the air intake pipe 13, and then flows into the water reheater and molten salt reheater of the first reheater group 14 in sequence. Step 3: The water storage medium in the water high-temperature heat storage tank enters the water reheater of the first reheater group 14 and the water reheater of the second reheater group 16 under the action of the second water pump. The molten salt storage medium in the molten salt high-temperature heat storage tank enters the molten salt reheater of the first reheater group 14 and the molten salt reheater of the second reheater group 16 under the action of the second molten salt pump. Step 4: The water reheater of the first reheater group performs preliminary low-temperature heating on the high-pressure air. The pre-heated high-pressure air enters the molten salt reheater of the first reheater group 14. The molten salt reheater performs high-temperature heating on the high-pressure air again. After heating, it is output to the first expander group 15. The high-temperature high-pressure air does work in the two high-pressure expanders of the first expander group 15 and is output to the generator 18. Step 5: The air temperature and pressure at the outlet of the first expander unit 15 both decrease, and then enter the water reheater and molten salt reheater of the second reheater group 16 in sequence. The air is first preliminarily heated at a low temperature by the water reheater, and then heated again at a high temperature by the molten salt reheater. After heating, it is output to the second expander unit 17. The high temperature air does work in the two low-pressure expanders of the second expander unit 17 and is output to the generator 18. Step 5: After the heat is released, the temperatures of the heat storage medium water and molten salt both decrease, and they are returned to the water low-temperature heat storage tank and the molten salt low-temperature heat storage tank respectively for recycling. Step 6: The first expander unit and the second expander unit coaxially drive the generator 18 to rotate, and the electrical energy generated by the generator 18 is stably connected to the power grid through the grid connection device; Step 7: The air flow rate in the pipeline gradually decreases along the pipeline, and the flow resistance along the entire line is greatly reduced until the pipeline pressure drops to the set lower limit, and the energy release process is completed.
[0056] This embodiment is applicable to high-temperature heat storage and release, that is, when the temperature of the high-temperature and high-pressure air output by the air compressor exceeds the heat storage range of water (above 90 degrees), this embodiment can realize compressed air energy storage. In this embodiment, the molten salt circulation subsystem can also be replaced by the heat transfer oil circulation subsystem.
[0057] Advantages of this invention: This invention constructs a compressed air energy storage system by reusing in-service sealed pipelines and adopts a segmented gas injection, segmented gas extraction and heat recovery and reheating coordinated operation mode, which greatly reduces the investment and construction cycle of gas storage facilities, significantly reduces the pressure drop along long pipelines, improves system efficiency and asset utilization, and delays pipeline corrosion and deterioration, thus combining economy, efficiency and safety.
[0058] This invention directly utilizes existing sealed pipelines as high-pressure gas storage space, eliminating the need for constructing large-scale facilities such as salt caverns and gas storage facilities. It can be put into operation after only completing an adaptability assessment and simple modifications, significantly reducing engineering investment and shortening the construction period.
[0059] This invention replaces the traditional single-point long-distance high-flow gas transmission with multi-point segmented low-flow gas transmission, effectively reducing pipeline friction loss and pressure drop by about 45%, thereby improving energy storage capacity and system round-trip efficiency.
[0060] The heat generated by the multi-stage compression of this invention is completely recovered through an intercooler and a high-low temperature heat storage tank. When releasing energy, the air is reheated, eliminating the need for additional fuel consumption. This closed-loop energy utilization results in higher power generation efficiency.
[0061] This invention reduces the long-term static time of pipelines by periodically charging and discharging gas, inhibiting internal corrosion, seal aging and performance degradation. At the same time, it can be disassembled and modified to facilitate the restoration of the original function of the pipeline, realizing multiple uses of one product.
[0062] The pipeline of this invention has undergone special evaluations of pressure resistance, fatigue, and sealing reliability. It is equipped with regulating valves, check valves, and shut-off valves to achieve multi-level protection, enabling flexible scheduling and graded energy storage, and is suitable for wind power and photovoltaic power consumption as well as grid peak shaving and valley filling.
[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A compressed air energy storage system based on in-service sealed pipelines, characterized in that: Includes a compressed energy storage subsystem and a pipeline gas storage subsystem; The compressed energy storage subsystem includes a multi-stage compression unit, a heat exchange unit, and an expansion power generation unit. The pipeline gas storage subsystem includes in-service sealed pipelines, valve assemblies, and segmented gas distribution units; The segmented gas distribution unit is connected to multiple gas injection points and gas intake points of the in-service sealed pipeline through multiple branch pipelines, forming a segmented gas injection and segmented gas intake gas distribution structure. During energy storage, the multi-stage compression unit compresses air to generate high-temperature and high-pressure air. The heat of compression in the high-temperature and high-pressure air is recovered and stored by the heat exchange unit. The cooled high-pressure air is injected into the in-service storage pipeline in stages by the segmented gas distribution unit for storage. During energy release, the compressed air in the in-service storage pipeline is taken out in stages by the segmented gas distribution unit and transported to the expansion power generation unit to complete power generation.
2. The compressed air energy storage system based on in-service sealed pipelines according to claim 1, characterized in that: The multi-stage compression unit includes at least two air compressors and a drive motor connected in series; the heat storage and exchange unit includes an intercooler heat exchange unit, which includes multiple intercooler groups, a low-temperature heat storage tank, and a high-temperature heat storage tank. The intercooler group includes one or more intercoolers connected in series, and the intercooler is a water intercooler, a molten salt intercooler, or a thermal oil intercooler; each air compressor is connected in series with each intercooler group alternately, the output end of the low-temperature heat storage tank is connected to the input end of each intercooler, and the output end of each intercooler is connected to the high-temperature heat storage tank. During energy storage, the drive motor drives each air compressor to compress air. The first air compressor sequentially feeds the compressed air into each intercooler of the first intercooler group. The heat storage medium in each intercooler absorbs the heat of compression of the compressed air and outputs it to the high-temperature heat storage tank. The cooled compressed air is then fed into the second compressor. The air compressed by the second compressor enters the second intercooler group. The heat storage medium in each intercooler of the second intercooler group absorbs the heat of compression of the compressed air and outputs it to the high-temperature heat storage tank. This process continues until the last intercooler outputs high-pressure air to the pipeline gas storage subsystem.
3. The compressed air energy storage system based on in-service sealed pipelines according to claim 2, characterized in that: Each intercooler outlet is equipped with a temperature monitor. When the temperature of the heat storage medium in the corresponding intercooler reaches a preset value, the heat storage medium is output to the high-temperature heat storage tank.
4. The compressed air energy storage system based on in-service sealed pipelines according to claim 2, characterized in that: A pressure monitor is installed at the outlet of the last intercooler. When the air pressure reaches the preset injection pressure, high-pressure air is output to the pipeline storage subsystem.
5. The compressed air energy storage system based on in-service sealed pipelines according to claim 1, characterized in that: The expansion power generation unit includes at least two expansion units and a generator connected in series; the heat storage and exchange unit also includes a reheat heat exchange unit, which includes multiple reheater groups, a high-temperature heat storage tank, and a low-temperature heat storage tank. Each reheater group includes one or more reheaters connected in series, and the reheaters are water reheaters, thermal oil reheaters, or molten salt reheaters. Each reheater group is connected in series with each expansion unit alternately. The output end of the high-temperature heat storage tank is connected to the input end of each reheater, and the output end of each reheater is connected to the low-temperature heat storage tank. When energy is released, the heat storage medium in the high-temperature heat storage tank enters each reheater of the first reheater group, and the high-pressure air of the pipeline gas storage subsystem enters each reheater in sequence. It is heated by the heat storage medium and then the cooled heat storage medium is output to the low-temperature heat storage tank for recycling. The heated high-pressure air enters the expander unit to do work and then enters the next stage reheater group. The output power of each expander unit jointly drives the generator to generate electricity.
6. The compressed air energy storage system based on in-service sealed pipelines according to claim 1, characterized in that: The segmented gas distribution unit includes an injection manifold, multiple injection branch pipes, an in-service sealed gas storage pipeline, multiple gas intake branch pipes, and a gas intake manifold connected in sequence. The injection manifold and the gas intake manifold are both arranged in a bypass coupling with the in-service sealed pipeline. The gas inlet of the injection manifold is connected to the compression unit, and the gas outlet of the gas intake manifold is connected to the expansion power generation unit. Multiple gas injection branch lines introduce high-pressure air from the gas injection manifold into the in-service sealed gas storage pipeline through each gas injection point, and multiple gas extraction branch lines extract high-pressure gas from each gas extraction point of the in-service sealed gas storage pipeline to the gas extraction manifold.
7. The compressed air energy storage system based on in-service sealed pipelines according to claim 6, characterized in that: The valve assembly is provided on both the gas injection branch pipeline and the gas intake branch pipeline. The valve assembly includes at least a regulating valve, a check valve, and a shut-off valve.
8. The compressed air energy storage system based on in-service sealed pipelines according to claim 1, characterized in that: During the energy storage process, multiple gas injection points simultaneously inject gas into different locations of the in-service sealed pipeline, and the gas flow rate in the pipeline gradually increases along the pipeline.
9. The compressed air energy storage system based on in-service sealed pipelines according to claim 1, characterized in that: During the energy release process, multiple gas intake points simultaneously draw gas from different locations within the in-service sealed pipeline, and the gas flow rate within the pipeline gradually decreases along the pipeline.
10. An operation method for a compressed air energy storage system based on an in-service sealed pipeline, applied to the compressed air energy storage system based on an in-service sealed pipeline as described in any one of claims 1 to 9, characterized in that: Includes the energy storage stage and the energy release stage; The energy storage stage includes: multi-stage compression unit compressing air, compression heat being recovered and stored by heat exchange unit, and compressed air being injected into in-service sealed pipelines simultaneously and in segments at multiple points by segmented gas distribution unit, transforming single long-distance high-flow gas transmission into multi-segment short-distance low-flow gas transmission, reducing pressure drop along the pipeline; The energy release stage includes: compressed air in the in-service sealed pipeline is extracted synchronously in multiple sections by the segmented gas distribution unit, collected and reheated by the heat storage and heat exchange unit, and then enters the expansion power generation unit to generate electricity.