Natural gas pipeline network energy storage and pressure regulation system and method based on constant pressure technology

Abstract

The invention relates to the technical field of energy storage, and discloses a natural gas pipeline network energy storage pressure regulating system and method based on a constant pressure technology. According to the natural gas pipeline network energy storage and pressure regulation system based on the constant pressure technology, the high-pressure tank and the normal-pressure tank are adopted as gas storage facilities, no special geological requirement is needed for a construction site, and the high-pressure tank and the normal-pressure tank can be arranged at any position along the pipeline network as needed; the constant-pressure liquid stored in the normal-pressure tank can be pumped into the high-pressure tank when the high-pressure tank outputs natural gas, the natural gas is directly extruded, the constant optimal pressure value is maintained when the high-pressure tank outputs the natural gas, the natural gas can be output at the stable and appropriate pressure, ultrahigh-pressure compression does not need to be carried out by consuming a huge amount of energy for maintaining the last-stage flow, and the energy consumption is reduced. No additional compressor is needed, and the overall energy consumption is reduced. Meanwhile, the electricity utilization time can be transferred, and therefore the operation cost is reduced, for example, the existing compressor is operated in the off-peak electricity period.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and more specifically to a natural gas pipeline energy storage pressure regulation system and method based on constant pressure technology. Background Technology

[0002] With the continuous growth of natural gas consumption and the expansion of long-distance gas transmission projects in my country, the stable operation and economical pressure regulation of natural gas pipeline networks have become crucial. Meanwhile, the Northwest region faces significant peak-valley differences and absorption pressures in renewable energy power generation. If surplus power during off-peak hours can be used to drive pipeline booster systems, and energy can be released for pressure regulation or power generation during peak hours, it can effectively achieve the spatial and temporal transfer and optimized allocation of energy, reduce pipeline transmission and distribution costs, and improve the overall flexibility and economy of the energy system.

[0003] Currently, pressure regulation and energy storage in natural gas pipeline networks largely rely on traditional compressor stations and specific geological gas storage facilities. Traditional compressor stations typically use multiple compressor units to directly pressurize the natural gas in the pipeline to compensate for pressure losses; geological gas storage facilities, on the other hand, perform sliding pressure storage and energy release.

[0004] However, large-scale geological gas storage facilities are heavily reliant on specific geological conditions, resulting in limited construction sites and substantial investments. Secondly, the constant-volume gas storage scheme employing sliding pressure operation requires the compressor's outlet pressure to always be higher than the pipeline's maximum pressure, leading to high compression energy consumption. Furthermore, upgrading existing compressor stations necessitates the addition of new high-pressure compressors. In short, existing pressure regulation and energy storage solutions result in multiple gas supply links, leading to higher end-user natural gas prices, which contradicts the initial goal of cost reduction and efficiency improvement. Summary of the Invention

[0005] In view of this, the present invention provides a natural gas pipeline energy storage and pressure regulation system and method based on constant pressure technology to solve the problem that existing solutions have multiple gas supply links, resulting in high natural gas terminal sales prices.

[0006] In a first aspect, the natural gas pipeline energy storage and pressure regulation system based on constant pressure technology provided by the present invention includes a compression unit, a thermal storage unit, a gas storage unit, and an energy release unit. A compression unit is used to pressurize natural gas from an upstream gas supply pipeline. A thermal storage unit, installed downstream of the compression unit along the natural gas flow direction, stores heat from the natural gas. The gas storage unit includes at least one high-pressure tank for storing high-pressure natural gas, at least one atmospheric pressure tank for storing constant-pressure liquid, and a constant-pressure pump. The constant-pressure pump's constant-pressure liquid outlet is connected to the high-pressure tank, and its constant-pressure liquid inlet is connected to the atmospheric pressure tank. The constant-pressure pump injects constant-pressure liquid into the high-pressure tank to maintain a constant output natural gas pressure. An energy release unit is connected between the high-pressure tank and the downstream gas pipeline along the natural gas flow direction. In energy storage mode, the compression unit injects pressurized natural gas into the high-pressure tank, and the heat is stored by the thermal storage unit. In energy release mode, the constant-pressure pump injects constant-pressure liquid from the atmospheric pressure tank into the high-pressure tank to maintain a constant output natural gas pressure. The natural gas in the tank is then transported to the downstream gas pipeline via the energy release unit.

[0007] Beneficial Effects: By using high-pressure and atmospheric pressure tanks as gas storage facilities, there are no special geological requirements for the construction site. They can be arranged anywhere along the pipeline network as needed. Furthermore, by installing constant-pressure pumps, natural gas is pumped from the high-pressure tanks to the atmospheric pressure tanks, directly compressing the natural gas. This maintains a constant, optimal pressure when the high-pressure tanks output natural gas, ensuring a stable and suitable pressure output. This eliminates the need for massive energy expenditure on ultra-high-pressure compression to maintain the final flow rate, and avoids the need for additional compressors, thus reducing overall energy consumption. Simultaneously, during operation, the upstream compression unit of the high-pressure tank only needs to reach the constant design pressure required for gas storage; it does not need to provide pressures far exceeding this. This allows for the full utilization of the existing compressor unit's capacity and pressure rating when retrofitting existing compressor stations to add energy storage functionality. Only the gas storage, heat storage, and constant-pressure modules of this invention need to be added, greatly reducing the technical difficulty and cost of retrofitting and improving the utilization and compatibility of existing infrastructure.

[0008] In one optional embodiment, the compression unit includes a compressor, the natural gas inlet of which is connected to the end of an upstream gas supply pipeline; the heat storage unit includes a first heat exchanger, a cryogenic tank, and a high-temperature tank, the natural gas inlet of the first heat exchanger is connected to the natural gas outlet of the compressor, the heat exchange medium outlet of the cryogenic tank is connected to the heat exchange medium inlet of the first heat exchanger, the heat exchange medium inlet of the high-temperature tank is connected to the heat exchange medium outlet of the first heat exchanger, and the heat exchange medium outlet of the high-temperature tank is connected to the heat exchange medium inlet of the cryogenic tank.

[0009] In one optional embodiment, the energy release unit includes a second heat exchanger, the heat exchange medium inlet of the second heat exchanger being connected to the heat exchange medium outlet of the high-temperature tank, and the heat exchange medium outlet of the second heat exchanger being connected to the heat exchange medium inlet of the low-temperature tank.

[0010] In one alternative embodiment, the natural gas inlet of the second heat exchanger is connected to the natural gas outlet of the high-pressure tank, and the natural gas outlet of the second heat exchanger is connected to a downstream gas pipeline.

[0011] In one alternative embodiment, the energy release unit further includes a turbine, the natural gas inlet of which is connected to the natural gas outlet of the second heat exchanger, and the natural gas outlet of which is connected to a downstream gas pipeline.

[0012] In one optional embodiment, the gas storage unit further includes a circulation pump, the circulation pump having a constant pressure liquid inlet connected to the high pressure tank and a constant pressure liquid outlet connected to the atmospheric pressure tank, for driving the constant pressure liquid to flow back from the high pressure tank to the atmospheric pressure tank.

[0013] In one alternative implementation, the constant-pressure liquid is immiscible with natural gas.

[0014] Secondly, the present invention also provides a natural gas pipeline energy storage and pressure regulation method based on constant pressure technology, which is applied to the natural gas pipeline energy storage and pressure regulation system based on constant pressure technology in the previous aspect. The pressure regulation method includes: energy storage: after upstream natural gas is pressurized by a compression unit, it flows through a heat exchange unit to store heat in a heat storage unit, and the cooled high-pressure natural gas is injected into a high-pressure tank for storage; energy release: a constant pressure pump is started to inject constant pressure liquid from an atmospheric pressure tank into a high-pressure tank to maintain a constant output natural gas pressure, and according to downstream pressure demand, the natural gas in the high-pressure tank is directly or after being heated and expanded to generate electricity and then transported to the downstream gas transmission pipeline.

[0015] Beneficial effects: Since the pressure regulation method for natural gas pipeline energy storage based on constant pressure technology is applied to natural gas pipeline energy storage pressure regulation system based on constant pressure technology, it has the same effect as the natural gas pipeline energy storage pressure regulation system based on constant pressure technology, and will not be elaborated here.

[0016] In one alternative implementation, when the pressure inside the high-pressure tank is higher than the required pressure of the downstream gas pipeline, the natural gas flows through the second heat exchanger, absorbs heat from the heat storage unit, drives the turbine to generate electricity, and then connects to the downstream gas pipeline.

[0017] In one alternative implementation, the compression unit starts up in a sliding pressure mode during the energy storage step, based on power consumption, during periods of low power consumption. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the structure of a natural gas pipeline energy storage and pressure regulation system based on constant pressure technology installed on the upstream and downstream gas supply pipelines, according to an embodiment of the present invention.

[0020] Figure 2 This is a schematic flowchart of a natural gas pipeline energy storage and pressure regulation method based on constant pressure technology, provided in an embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures:

[0022] 1. Natural gas pipeline energy storage and pressure regulation system based on constant pressure technology; 101. High-pressure tank; 102. Atmospheric pressure tank; 103. Constant pressure pump; 104. Compressor; 105. First heat exchanger; 106. Low-temperature tank; 107. High-temperature tank; 108. Second heat exchanger; 109. Turbine; 110. Circulation pump;

[0023] 2. Upstream gas supply pipeline;

[0024] 3. Downstream gas pipeline. Detailed Implementation

[0025] 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.

[0026] According to embodiments of the present invention, the natural gas pipeline energy storage and pressure regulation system and method based on constant pressure technology provided by the present invention can solve the problem that existing solutions have multiple gas supply links, resulting in high natural gas terminal sales prices.

[0027] The following is combined Figure 1 and Figure 2 The following describes embodiments of the present invention.

[0028] In a first aspect, the natural gas pipeline energy storage and pressure regulation system 1 based on constant pressure technology provided by the present invention includes a compression unit, a thermal storage unit, a gas storage unit, and an energy release unit.

[0029] Specifically, the compression unit is used to pressurize the natural gas from the upstream gas supply pipeline 2.

[0030] Along the direction of natural gas flow, the thermal storage unit is installed downstream of the compression unit. The thermal storage unit is used to store the heat in the natural gas.

[0031] like Figure 1 As shown, the gas storage unit includes at least one high-pressure tank 101 for storing high-pressure natural gas, at least one atmospheric pressure tank 102 for storing constant-pressure liquid, and a constant-pressure pump 103. The constant-pressure pump 103 has its constant-pressure liquid outlet connected to the high-pressure tank 101 and its constant-pressure liquid inlet connected to the atmospheric pressure tank 102. The constant-pressure pump 103 is used to inject constant-pressure liquid into the high-pressure tank 101 to maintain a constant output pressure of natural gas from the high-pressure tank 101.

[0032] Along the natural gas flow direction, the energy release unit is connected between the high-pressure tank 101 and the downstream gas pipeline 3.

[0033] In the energy storage mode, the compression unit injects the pressurized natural gas into the high-pressure tank 101, and the heat is stored by the heat storage unit. In the energy release mode, the constant pressure pump 103 injects the constant pressure liquid in the atmospheric pressure tank 102 into the high-pressure tank 101 to maintain the constant pressure of the natural gas output from the high-pressure tank 101. The natural gas in the tank is then transported to the downstream gas pipeline 3 through the energy release unit.

[0034] This setup, using high-pressure tank 101 and atmospheric pressure tank 102 as gas storage facilities, requires no special geological conditions for the construction site and can be arranged at any location along the pipeline as needed. Furthermore, by installing a constant-pressure pump 103, the constant-pressure liquid stored in the atmospheric pressure tank 102 can be pumped into the high-pressure tank 101 to directly compress the natural gas. This ensures that the high-pressure tank 101 maintains a constant optimal pressure when outputting natural gas, allowing the natural gas to be output at a stable and appropriate pressure. This eliminates the need for consuming huge amounts of energy for ultra-high-pressure compression to maintain the final flow rate, and eliminates the need for additional compressors, thus reducing overall energy consumption.

[0035] Meanwhile, during use, the performance of the upstream compression unit of the high-pressure tank 101 only needs to reach the constant design pressure required for gas storage, without having the ability to provide pressures far exceeding this. This allows for full utilization of the capacity and pressure level of the existing compressor units when modifying existing compressor stations to add energy storage functions. Only the gas storage, heat storage, and constant pressure modules of this invention need to be added, which greatly reduces the technical difficulty and cost of modification and improves the utilization rate and compatibility of existing infrastructure.

[0036] It should be noted that those skilled in the art should recognize that "high pressure" in a high-pressure tank is a relative concept, and its specific value can vary depending on the actual system configuration, fluid medium, and downstream demands. Any scheme utilizing this pressure difference for energy recovery falls within the scope of protection sought by this patent.

[0037] In one embodiment, the compression unit includes a compressor 104, the natural gas inlet of which is connected to the end of the upstream gas supply pipeline 2.

[0038] Among them, such as Figure 1 As shown, the heat storage unit includes a first heat exchanger 105, a low-temperature tank 106, and a high-temperature tank 107. The natural gas inlet of the first heat exchanger 105 is connected to the natural gas outlet of the compressor 104. The heat exchange medium outlet of the low-temperature tank 106 is connected to the heat exchange medium inlet of the first heat exchanger 105. The heat exchange medium inlet of the high-temperature tank 107 is connected to the heat exchange medium outlet of the first heat exchanger 105, and the heat exchange medium outlet of the high-temperature tank 107 is connected to the heat exchange medium inlet of the low-temperature tank 106.

[0039] With this configuration, the temperature of natural gas will rise after compression. By providing a first heat exchanger 105 downstream of the compressor 104 and using a low-temperature tank 106 and a high-temperature tank 107, the heat exchange medium can fully exchange heat with the natural gas in the first heat exchanger 105. After the natural gas is cooled, it is stored in the high-pressure tank 101, while the heat exchange medium, after becoming a high-temperature medium, is stored in the high-temperature tank 107. This avoids the loss of this heat to the environment and the resulting energy waste. The compression work in the form of electrical or mechanical energy is stored as thermal energy, realizing the cascade utilization of energy, improving the overall energy utilization efficiency of the system, and directly reducing operating costs.

[0040] It should be noted that the core of this system lies in utilizing the temperature difference between fluids to achieve energy conversion or transport. Those skilled in the art should recognize that "high temperature" and "low temperature" are relative concepts, and their absolute values ​​can be significantly adjusted and optimized according to the system scale, working fluid selection, and environmental conditions. Any scheme that uses different temperature parameters but achieves the same or similar functions (such as work recovery, refrigeration, heating, etc.) should fall within the scope of protection sought by this patent.

[0041] It should be noted that this application does not limit the number of compressors 104. The minimum configuration can be made according to actual needs, or redundancy can be increased for future expansion, or the pressure margin of the pipeline network can be fully utilized for system-level energy storage. The configuration can be arranged as needed.

[0042] Preferably, the number of compressors 104 is one, two or more.

[0043] It should be noted that this application does not limit the number of the first heat exchanger 105; it can be set as needed.

[0044] Preferably, the first heat exchanger 105 corresponds one-to-one with the compressor 104.

[0045] In one embodiment, such as Figure 1 As shown, the energy release unit includes a second heat exchanger 108. The heat exchange medium inlet of the second heat exchanger 108 is connected to the heat exchange medium outlet of the high-temperature tank 107, and the heat exchange medium outlet of the second heat exchanger 108 is connected to the heat exchange medium inlet of the low-temperature tank 106.

[0046] With this configuration, the stored natural gas can be heated before entering the downstream gas pipeline 3 by setting up a second heat exchanger 108. The heat from the compression process, which is pre-stored in the high-temperature tank 107 of the heat storage unit, is transferred to the low-temperature natural gas from the high-pressure tank 101 through the heat exchange medium, so that the temperature of the low-temperature natural gas can be raised to a safe transmission temperature, avoiding all safety hazards caused by low temperature, such as preventing the low temperature of natural gas from causing cold embrittlement to the downstream pipeline materials, maintaining the thermal stability of natural gas transmission, and ensuring the continuity and reliability of the gas transmission process.

[0047] Meanwhile, by setting up a second heat exchanger 108, the waste heat generated by the system itself can be reduced, the dependence on external heat sources can be reduced, and cost reduction and efficiency improvement can be achieved.

[0048] It can be noted that the natural gas inlet of the second heat exchanger 108 is connected to the natural gas outlet of the high-pressure tank 101, and the natural gas outlet of the second heat exchanger 108 is connected to the downstream gas transmission pipeline 3.

[0049] This configuration ensures the continuity and reliability of the gas transmission process by heating the low-temperature natural gas to a safe temperature range that meets the requirements of the pipeline network by passing the natural gas from the outlet of the high-pressure tank 101 through the second heat exchanger 108 before entering the downstream gas transmission pipeline 3.

[0050] In one embodiment, such as Figure 1 As shown, the energy release unit also includes a turbine 109, the natural gas inlet of which is connected to the natural gas outlet of the second heat exchanger 108, and the natural gas outlet of the turbine 109 is connected to the downstream gas pipeline 3.

[0051] With this configuration, by adding a turbine 109, the natural gas in the high-pressure tank 101 isentropically expands within it, effectively converting the pressure energy and thermal energy of the gas into mechanical energy, which can be used to directly drive power generation and feed it back to the grid or for the system's own use, thereby reducing external power consumption.

[0052] In one embodiment, such as Figure 1As shown, the gas storage unit also includes a circulation pump 110, whose constant pressure liquid inlet is connected to the high pressure tank 101, and whose constant pressure liquid outlet is connected to the atmospheric pressure tank 102, for driving the constant pressure liquid to flow back from the high pressure tank 101 to the atmospheric pressure tank 102.

[0053] With this configuration, the constant-pressure liquid stored in the high-pressure tank 101 can be reliably transported back to the atmospheric pressure tank 102 by the circulation pump 110, ensuring that it is ready for the next energy storage stage, meeting the needs of the power grid or pipeline network for rapid peak shaving, and improving the system's response speed and usability.

[0054] It should be noted that, in this application, the constant pressure liquid is preferably made of a material that is immiscible with natural gas.

[0055] This configuration, by setting the constant-pressure liquid to a material that is immiscible with natural gas, prevents the liquid components from vaporizing or dissolving into the natural gas, thereby avoiding any impact on the quality of the natural gas. This ensures that the natural gas output to the downstream gas pipeline 3 is consistent with the natural gas output from the upstream gas pipeline, guaranteeing that the concentration and quality of the natural gas meet the usage requirements.

[0056] Preferably, the constant pressure liquid is selected from liquid media such as water or ethylene glycol aqueous solution that do not undergo physical and chemical reactions with natural gas under high pressure.

[0057] The natural gas pipeline energy storage and pressure regulating system 1 based on constant pressure technology mentioned in the above embodiments can be upgraded on existing booster stations, retaining the original compression units without the need to add compression equipment. That is, when applied to existing systems, the constant pressure scheme, through the setting of gas storage units, can achieve system flexibility and improve regulation capacity, and can also reduce the number of compressors.

[0058] Specifically, when upgrading an existing booster station, the operating mode is as follows: upstream natural gas enters the booster station (including the natural gas pipeline energy storage and pressure regulation system 1 based on constant pressure technology) via upstream gas supply pipeline 2. It is pressurized by the compression unit. The pressurized natural gas releases heat through the first heat exchanger 105. The heat is carried away by the heat exchange medium in the low-temperature tank 106 and stored in the high-temperature tank 107. The resulting low-temperature high-pressure natural gas working medium is stored in the high-pressure tank 101 to complete energy storage. When gas is needed, the constant pressure pump 103 pumps the constant pressure liquid into the high-pressure tank 101 to maintain the constant gas transmission pressure of the high-pressure tank 101. When the pressure in the compression unit and the high-pressure tank 101 is basically consistent with that in the downstream gas transmission pipeline 3, the natural gas is sent into the downstream gas transmission pipeline 3 to complete energy release.

[0059] Furthermore, during the energy release process, the compression unit can be activated simultaneously to supply gas to the downstream gas pipeline 3 based on the downstream gas supply volume.

[0060] The natural gas pipeline energy storage and pressure regulation system 1 based on constant pressure technology mentioned in the above embodiments can also be applied to newly added booster stations. By using constant pressure transmission, the configuration of compression units can be reduced, the overall energy storage duration can be extended, the cost investment of compression units can be reduced, and peak-valley arbitrage can also be carried out.

[0061] Specifically, when applied to newly built systems, each unit can be configured with minimal resources based on its actual role; or redundancy can be increased for future expansion; or the pressure margin of the pipeline network can be fully utilized for system-level energy storage, such as... Figure 1 As shown by the dashed line on the upstream side of the second heat exchanger 108, when the compressor 104 is configured with a pressure higher than that of the pipeline network, the power consumption should be further increased. At this time, the pressure in the pipeline is higher than the actual required pressure. When the power is distributed downstream, the turbine 109 is used to recover the power, thereby reducing the investment in infrastructure. That is, the turbine 109 is used to recover the excess pressure energy in the natural gas working fluid and convert it into electrical energy for reuse. This setting not only meets the transmission requirements but also saves the cost of building other pressure reducing facilities.

[0062] It can be explained that the operating mode applied to the newly built system is as follows: upstream natural gas enters the newly built booster station (including the natural gas pipeline energy storage and pressure regulation system 1 based on constant pressure technology) through the upstream gas supply pipeline 2. It is boosted by the compression unit. The pressurized natural gas releases heat through the first heat exchanger 105. The heat is carried away by the heat exchange medium in the low temperature tank 106 and stored in the high temperature tank 107. The resulting low temperature and high pressure natural gas working fluid is stored in the high pressure tank 101 to complete the energy storage. When gas is needed, the constant pressure pump 103 pumps the constant pressure liquid into the high pressure tank 101 to keep the gas transmission pressure of the high pressure tank 101 constant.

[0063] When the pressure inside the compression unit and high-pressure tank 101 is basically the same as that in the downstream gas pipeline 3, natural gas is sent into the downstream gas pipeline 3 to complete the energy release.

[0064] Of course, when the pressure inside the compression unit and high-pressure tank 101 is higher than that in the downstream gas pipeline 3, it needs to pass through the second heat exchanger 108 and turbine 109 before being connected to the downstream gas pipeline 3 to complete the energy release. This configuration allows the system to utilize not only the natural gas in the high-pressure tank 101, but also the high-pressure gas stored in the pipeline to increase the system's power generation and further enhance its cost reduction and efficiency improvement capabilities.

[0065] Furthermore, during the energy release process, the compression unit can be activated simultaneously to supply gas to the downstream gas pipeline 3 based on the downstream gas supply volume.

[0066] The natural gas pipeline energy storage and pressure regulation system 1 mentioned in the above embodiments, by setting up a gas storage unit, can achieve constant pressure transmission of natural gas, reduce energy storage cost investment, utilize the natural gas pipeline system for energy storage, realize peak-valley arbitrage, and further reduce the proportion of natural gas system transmission and distribution costs.

[0067] According to an embodiment of the present invention, in another aspect, the present invention also provides a natural gas pipeline network energy storage pressure regulation method based on constant pressure technology, which is applied to the aforementioned natural gas pipeline network energy storage pressure regulation system 1 based on constant pressure technology.

[0068] Among them, the natural gas pipeline energy storage and pressure regulation method based on constant pressure technology includes: a constant pressure process, which includes an energy storage stage and an energy release stage.

[0069] Specifically, energy storage: After the upstream natural gas is pressurized by the compression unit, it flows through the heat exchange unit to store the heat in the heat storage unit. The cooled high-pressure natural gas is then injected into the high-pressure tank 101 for storage. Energy release: The constant pressure pump 103 is started to inject the constant pressure liquid in the atmospheric pressure tank 102 into the high-pressure tank 101 to maintain the constant pressure of its output natural gas. According to the downstream pressure demand, the natural gas in the high-pressure tank 101 is directly or after being heated and expanded to generate electricity and then transported to the downstream gas pipeline 3.

[0070] This setup is because the pressure regulation method for natural gas pipeline energy storage based on constant pressure technology, when applied to the pressure regulation system 1 for natural gas pipeline energy storage based on constant pressure technology, has the same effect as the pressure regulation system 1 for natural gas pipeline energy storage based on constant pressure technology, and will not be elaborated further here.

[0071] In one embodiment, when the pressure inside the high-pressure tank 101 is higher than the required pressure of the downstream gas pipeline 3, natural gas flows through the second heat exchanger 108, and after absorbing the heat from the heat storage unit, it drives the turbine 109 to generate electricity, which is then connected to the downstream gas pipeline 3.

[0072] In one embodiment, the compression unit starts up in a sliding mode during low power consumption periods, based on power consumption during the energy storage step.

[0073] With this setup, the compression unit starts operating during periods of low power consumption (i.e., periods of low or flat electricity prices) to store energy, helping the grid absorb excess power and reducing grid load. This reduces operating costs and achieves cost reduction and efficiency improvement.

[0074] It can be explained that by implementing a sliding pressure compression and constant pressure transportation scheme, the investment in incompressible fluid work recovery equipment can be reduced, and the equipment for transporting natural gas can be simplified, thereby reducing costs. At the same time, compared with conventional gas storage methods, the gas storage volume is smaller, thereby reducing the geographical limitations on the gas storage unit.

[0075] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A natural gas pipeline network energy storage pressure regulating system based on constant pressure technology, characterized in that, The system comprises: a compression unit for pressurizing natural gas from an upstream gas supply pipeline (2); a heat storage unit installed downstream of the compression unit in the direction of natural gas flow, the heat storage unit being configured to store heat generated by the pressurized natural gas; a gas storage unit comprising at least one high-pressure tank (101) for storing high-pressure natural gas, at least one normal-pressure tank (102) for storing constant-pressure liquid, and a constant-pressure pump (103) having a constant-pressure liquid outlet connected to the high-pressure tank (101) and a constant-pressure liquid inlet connected to the normal-pressure tank (102), the constant-pressure pump (103) being configured to inject constant-pressure liquid into the high-pressure tank (101) to maintain a constant pressure of the natural gas output by the high-pressure tank (101); a discharge unit connected between the high-pressure tank (101) and a downstream gas transmission pipeline (3) in the direction of natural gas flow; wherein, in the energy storage mode, the compression unit injects pressurized natural gas into the high-pressure tank (101), and the heat storage unit stores the heat; in the energy discharge mode, the constant-pressure pump (103) injects constant-pressure liquid from the normal-pressure tank (102) into the high-pressure tank (101) to maintain a constant pressure of the natural gas output by the high-pressure tank (101), and the natural gas in the tank is transmitted to the downstream gas transmission pipeline (3) through the discharge unit.

2. The natural gas pipeline network energy storage and pressure regulation system based on constant-pressure technology according to claim 1, wherein: the compression unit comprises a compressor (104) having a natural gas inlet connected to the end of the upstream gas supply pipeline (2); the heat storage unit comprises a first heat exchanger (105), a low-temperature tank (106), and a high-temperature tank (107), the first heat exchanger (105) having a natural gas inlet connected to the natural gas outlet of the compressor (104), the low-temperature tank (106) having a heat medium outlet connected to the heat medium inlet of the first heat exchanger (105), the high-temperature tank (107) having a heat medium inlet connected to the heat medium outlet of the first heat exchanger (105), and the high-temperature tank (107) having a heat medium outlet connected to the heat medium inlet of the low-temperature tank (106).

3. The natural gas pipeline network energy storage and pressure regulation system based on constant-pressure technology according to claim 2, wherein: the discharge unit comprises a second heat exchanger (108) having a heat medium inlet connected to the heat medium outlet of the high-temperature tank (107) and a heat medium outlet connected to the heat medium inlet of the low-temperature tank (106).

4. The natural gas pipeline network energy storage and pressure regulation system based on constant-pressure technology according to claim 3, wherein: the natural gas inlet of the second heat exchanger (108) is connected to the natural gas outlet of the high-pressure tank (101), and the natural gas outlet of the second heat exchanger (108) is connected to the downstream gas transmission pipeline (3).

5. The natural gas pipeline network energy storage and pressure regulation system based on constant-pressure technology according to claim 4, wherein: The energy releasing unit further comprises a turbine (109), a natural gas inlet of the turbine (109) being connected to a natural gas outlet of the second heat exchanger (108), and a natural gas outlet of the turbine (109) being connected to the downstream gas pipeline (3).

6. The natural gas pipeline network energy storage pressure regulating system based on the constant pressure technology according to any one of claims 1-5, characterized in that, The gas storage unit further comprises a circulating pump (110), a constant pressure liquid inlet of the circulating pump (110) being connected to the high-pressure tank (101), and a constant pressure liquid outlet of the circulating pump (110) being connected to the atmospheric-pressure tank (102), for driving the constant pressure liquid to flow back from the high-pressure tank (101) to the atmospheric-pressure tank (102).

7. The natural gas pipeline network energy storage pressure regulating system based on the constant pressure technology according to any one of claims 1-5, characterized in that, The constant pressure liquid is immiscible with the natural gas.

8. A method for natural gas pipeline network energy storage pressure regulating based on constant pressure technology, characterized in that, The pressure regulating method is applied to the natural gas pipeline network energy storage pressure regulating system based on the constant pressure technology according to any one of claims 1-7, and comprises: Energy storage: the upstream natural gas is pressurized by the compression unit, flows through the heat exchange unit to store heat to the heat storage unit, and the cooled high-pressure natural gas is injected into the high-pressure tank (101) for storage; Energy releasing: the constant pressure pump (103) is started, the constant pressure liquid in the atmospheric-pressure tank (102) is injected into the high-pressure tank (101) to maintain the output natural gas pressure constant, and the natural gas in the high-pressure tank (101) is directly or after being expanded to generate electricity and then delivered to the downstream gas pipeline (3) according to the downstream pressure demand.

9. The natural gas pipeline network energy storage pressure regulating method based on the constant pressure technology according to claim 8, characterized in that, When the pressure in the high-pressure tank (101) is higher than the demand pressure of the downstream gas pipeline (3), the natural gas flows through the second heat exchanger (108), drives the turbine (109) to generate electricity after absorbing the heat of the heat storage unit, and is then merged into the downstream gas pipeline (3).

10. The natural gas pipeline network energy storage pressure regulating method based on the constant pressure technology according to claim 8, characterized in that, During the energy storage step, the compression unit is started and operated in a sliding pressure mode according to the power consumption.

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