A compressed air energy storage system and method

Abstract

This invention provides a compressed air energy storage system and method. The system includes an air compression unit, a dual-flow axial turbine unit, a compressed air storage device, and cold and hot fluid storage devices. The air compression unit includes a multi-stage air compressor and a multi-stage cooler. The dual-flow axial turbine unit includes a multi-stage dual-flow axial turbine and a multi-stage heater. The dual-flow axial turbine comprises two coaxial, symmetrically distributed turbine parts, with the air inlets of both parts located on one side of the middle of the turbine. This invention improves the turbine structure by employing a dual-flow axial turbine, designing the axial turbine as a symmetrical two-part turbine structure. This balances the horizontal thrust at both ends of the turbine, effectively shortens the rotor shaft length, increases the stability of the device operation, ensures continuous and stable operation of the compressed air energy storage system, and improves energy storage efficiency. The improved system has a simple structure, is easy to operate, has low cost, and is widely applicable.

Description

Technical Field

[0001] This invention belongs to the field of energy storage and power generation technology, and relates to a compressed air energy storage system and method. Background Technology

[0002] As a crucial technology and fundamental equipment supporting new power systems, the large-scale development of energy storage technology is an inevitable trend. Compressed air energy storage systems are an energy storage technology capable of storing large-capacity, long-term electrical energy. They offer advantages such as reliability, economy, and environmental friendliness. In power systems, they are primarily used for load balancing, renewable energy storage, and system backup, representing a technology with significant development potential in the energy storage field. Compressed air energy storage mainly stores excess electricity by compressing atmospheric pressure air to high pressure using a compressor. When electricity is needed, the high-pressure air is released and expands to generate electricity, achieving an energy storage efficiency of over 60%.

[0003] Currently, the charging and discharging processes of compressed air energy storage systems primarily utilize compressors during charging. These compressors use the heat from air compression to heat the feedwater, facilitating heat transfer and enabling multiple compressions. During discharging, turbines are the main equipment used, utilizing air expansion to perform work. The structure and type of turbine significantly impact energy utilization and power generation efficiency. Turbines can be categorized by the direction of medium flow, such as axial-flow and centripetal types. Existing compressed air energy storage systems using centripetal turbines as the work unit require thrust balancing pistons at both ends of the rotor to balance axial thrust, increasing rotor length and complicating rotor dynamics design and equipment manufacturing. If an axial-flow turbine is used, the axial thrust problem cannot be effectively balanced, necessitating additional fixing components or increased weight.

[0004] CN 113250775A discloses a large-capacity compressed air energy storage and power generation system and method with segmented expansion work. The system includes a compressed air energy storage module, a lithium bromide refrigeration module, a gas-fired power generation module, an air turbine power generation module, a gas-to-gas heat exchanger module, and an air reheater. The compressed air energy storage module is connected to a gas storage device. A heat transfer medium water module is used to cool the compression heat of the compressed air energy storage module and serves as the refrigeration heat source for the lithium bromide refrigeration module. The gas storage device is connected to the air turbine power generation module via the gas-to-gas heat exchanger module. The exhaust system of the air turbine power generation module is connected to the air reheater. The air reheater is connected to the gas-fired power generation module. The exhaust system of the gas-fired power generation module is connected to the gas-to-gas heat exchanger module and the heat exchange medium port of the air reheater. This system is essentially a coupling process of gas-fired power generation and compressed air energy storage power generation, supplementing the shortcomings of gas-fired power generation. It does not address the type or structural improvement of the air turbine.

[0005] CN 112594018A discloses an air turbine system and its starting method for a compressed air energy storage power generation system. The system includes a salt cavern, a gas-water heat exchanger, a first oil-gas heat exchanger, a second oil-gas heat exchanger, an air turbine high-pressure cylinder, a third oil-gas heat exchanger, a fourth oil-gas heat exchanger, and an air turbine low-pressure cylinder, connected in sequence. A quick-closing valve and a setting valve are sequentially installed on the pipeline between the salt cavern and the gas-water heat exchanger. A high-pressure inlet valve and a high-pressure regulating valve are sequentially installed on the pipeline between the second oil-gas heat exchanger and the air turbine high-pressure cylinder. A low-pressure inlet valve and a low-pressure regulating valve are sequentially installed on the pipeline between the fourth oil-gas heat exchanger and the air turbine low-pressure cylinder. This system is primarily designed for air turbine systems, but focuses on the starting method and process of the air turbine to improve its regulating capability. It does not address the issue of the axial thrust inherent in the turbine itself.

[0006] In summary, the design of turbine structures in compressed air energy storage systems requires addressing existing turbine problems and improving the turbine structure to balance axial thrust, thereby ensuring improved operational stability and power generation capacity of the air energy storage system. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention aims to provide a compressed air energy storage system and method. The system improves the turbine structure by adopting a dual-flow axial turbine, designing the axial turbine as a symmetrical two-part turbine structure, which can balance the horizontal thrust at both ends of the turbine, effectively shorten the rotor shaft length, increase the stability of the device operation, and ensure the continuous and stable operation of the compressed air energy storage system.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] On one hand, the present invention provides a compressed air energy storage system, the system comprising an air compression unit, a dual-flow axial turbine unit, a compressed air storage device, and a cold and hot fluid storage device; the air compression unit comprises a multi-stage air compressor and a multi-stage cooler, each stage of the air compressor corresponding to a stage of the cooler; the dual-flow axial turbine unit comprises a multi-stage dual-flow axial turbine and a multi-stage heater, each stage of the dual-flow axial turbine corresponding to a stage of the heater, the dual-flow axial turbine comprising two coaxial and symmetrically distributed turbine parts, the air inlets of the two turbine parts being located on one side of the middle of the dual-flow axial turbine;

[0010] The outlet of the air compression unit is connected to the inlet of the compressed air storage device, and the outlet of the compressed air storage device is connected to the inlet of the dual-flow axial turbine unit. The cold fluid storage device, cooler, hot fluid storage device and heater constitute a fluid circulation loop.

[0011] In this invention, according to the needs of compressed air energy storage power generation systems, compressors and turbines are essential equipment. As an important device for releasing energy and converting it into electrical energy, the structure and operational stability of the turbine are crucial. Based on the problems of traditional centripetal turbines, this invention improves the turbine structure by adopting a dual-flow axial turbine. The axial turbine is designed as a symmetrical two-part turbine structure with opposite airflow directions in the two parts, which can balance the horizontal thrust at both ends of the turbine, effectively shorten the rotor shaft length, increase the stability of rotor dynamics, thereby ensuring the continuous and stable operation of the compressed air energy storage system and improving energy storage efficiency. The improved system structure is simple, requires no complex equipment, is easy to operate, has significant effects, low cost, and wide applicability.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0013] As a preferred embodiment of the present invention, both the air compressor and the cooler include at least 3 stages, such as 3, 4, 5, 6 or 8 stages, preferably 4 to 8 stages.

[0014] Preferably, the air compressor and cooler are arranged alternately in series.

[0015] Preferably, the inlet of the first-stage air compressor is connected to the atmosphere, the inlets of the remaining air compressors are connected to the hot-side outlet of the previous stage cooler, the outlets of each air compressor are connected to the hot-side inlets of the corresponding stage coolers, and the outlet of the last stage cooler is connected to the inlet of the compressed air storage device.

[0016] As a preferred embodiment of the present invention, the air compression unit further includes an electric motor, the output shaft of which is connected to the air compressor; the electric motor is used to drive the compressor.

[0017] Preferably, the air compressor includes a centrifugal compressor.

[0018] Preferably, the cooler includes any one or a combination of at least two of shell-and-tube heat exchangers, plate heat exchangers, or plate-fin heat exchangers. Typical but non-limiting examples of such combinations include: a combination of a shell-and-tube heat exchanger and a plate heat exchanger, a combination of a plate heat exchanger and a plate-fin heat exchanger, and a combination of a shell-and-tube heat exchanger, a plate heat exchanger, and a plate-fin heat exchanger.

[0019] Preferably, the compressed air storage device includes a high-pressure air tank.

[0020] As a preferred technical solution of the present invention, the dual-flow axial turbine and the heater both include at least 2 stages, such as 2 stages, 3 stages, 4 stages or 5 stages, preferably 2 to 4 stages.

[0021] Preferably, the inlet of the first-stage dual-flow axial turbine is connected to the outlet of the compressed air storage device, and the outlet of the last-stage dual-flow axial turbine is open to the atmosphere.

[0022] Preferably, the two turbines in the dual-flow axial turbine are divided into a high-pressure turbine and a low-pressure turbine in the order in which the compressed air flows.

[0023] Preferably, the heater corresponding to the first-stage dual-flow axial turbine is located between the high-pressure turbine and the low-pressure turbine, according to the order in which the compressed air flows.

[0024] Preferably, the outlet of the high-pressure turbine is connected to the cold-side inlet of the heater, the cold-side outlet of the heater is connected to the inlet of the low-pressure turbine, and the outlet of the low-pressure turbine is connected to the inlet of the high-pressure turbine in the next stage dual-flow axial turbine.

[0025] In this invention, the different turbine sections of the dual-flow axial turbine have different inlet pressures, and the two are arranged symmetrically. The inlets are all located on the inner side, that is, in the middle of the entire dual-flow axial turbine. This means that the high-temperature section is also concentrated in the middle, which can effectively reduce thermal stress. At the same time, the rotor bearing operates at a lower temperature, which is beneficial to bearing design.

[0026] As a preferred embodiment of the present invention, the dual-flow axial turbine unit further includes a generator, the input shaft of which is connected to the dual-flow axial turbine.

[0027] In this invention, multiple dual-flow axial turbines perform work under high-pressure air drive, generating electrical energy through a generator.

[0028] Preferably, the heater includes any one or a combination of at least two of shell-and-tube heat exchangers, plate heat exchangers, or plate-fin heat exchangers. Typical but non-limiting examples of such combinations include: a combination of a shell-and-tube heat exchanger and a plate heat exchanger, a combination of a plate heat exchanger and a plate-fin heat exchanger, and a combination of a shell-and-tube heat exchanger, a plate heat exchanger, and a plate-fin heat exchanger.

[0029] As a preferred embodiment of the present invention, the cold fluid storage device includes a cold tank, and the hot fluid storage device includes a hot tank.

[0030] Preferably, the outlet of the cold fluid storage device is connected to the cold-side inlet of each stage of cooler, the cold-side outlet of each stage of cooler is connected to the inlet of the hot fluid storage device, the outlet of the hot fluid storage device is connected to the hot-side inlet of each stage of heater, and the hot-side outlet of each stage of heater is connected to the inlet of the cold fluid storage device.

[0031] Preferably, the medium in the cold fluid storage device and the hot fluid storage device includes water.

[0032] On the other hand, the present invention provides a method for compressed air energy storage and release using the above-described system, the method comprising the following steps:

[0033] (1) After the air is compressed, the temperature and pressure increase. After the cold side fluid of the cooler exchanges heat, it flows to the compressed air storage device to store the pressure potential energy. At the same time, the temperature of the cold side fluid of the cooler increases after heat exchange, and the heat is stored to form a hot fluid.

[0034] (2) Release the compressed air obtained in step (1) and let it flow to the high-pressure turbine part of the dual-flow axial turbine to expand and do work. Then it exchanges heat with the hot side fluid of the heater and flows to the low-pressure turbine part of the dual-flow axial turbine to expand and do work until it is discharged. At the same time, the temperature of the hot side fluid of the heater decreases and it is returned to be used as a cold fluid.

[0035] In this invention, the operation of the compressed air energy storage system includes two processes: energy storage and energy release, as described in steps (1) and (2) above. The two processes are connected by the formation and utilization of compressed air, and cold and hot fluids circulate between them as energy storage media.

[0036] As a preferred technical solution of the present invention, the air compression and cooling operation in step (1) is repeated multiple times, for example, 3 times, 4 times, 5 times, 6 times or 8 times, preferably 4 to 8 times.

[0037] Preferably, the air temperature at the outlet of the primary compressor is 170–200°C, such as 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, or 200°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The pressure is 0.3–0.5 MPa, such as 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, or 0.5 MPa, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0038] Preferably, the temperature of the compressed air drops to 20-50°C after passing through the first-stage cooler, and the outlet temperature of each subsequent cooler is independently 20-50°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, or 45°C or 50°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, the pressure loss of each stage cooler is independently between 0 and 0.05 MPa, such as 0 MPa, 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa or 0.05 MPa, but is not limited to the listed values; other unlisted values ​​within this range also apply.

[0040] Preferably, the pressure of the compressed air at the outlet of the last stage compressor is 7 to 13 MPa, such as 7 MPa, 7.5 MPa, 8 MPa, 8.5 MPa, 9 MPa, 9.5 MPa, 10 MPa, 11 MPa, 12 MPa or 13 MPa, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] As a preferred technical solution of the present invention, the operation of compressing air expansion and heating in step (2) is repeated multiple times, for example, 2 times, 3 times, 4 times or 5 times, preferably 2 to 4 times.

[0042] Preferably, the inlet pressure of the high-pressure turbine section in the single-stage dual-flow axial turbine is 6–9 MPa, such as 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa, 8 MPa, 8.5 MPa, or 9 MPa, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The outlet pressure is 2.5–3 MPa, such as 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, 2.9 MPa, or 3 MPa, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0043] Preferably, the inlet temperature of the compressed air in the primary heater is 25–35°C, such as 25°C, 27°C, 30°C, 32°C, or 35°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The outlet temperature is 155–195°C, such as 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, or 195°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0044] Preferably, the pressure loss of each stage heater is independently between 0 and 0.05 MPa, such as 0 MPa, 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa or 0.05 MPa, but is not limited to the listed values; other unlisted values ​​within this range also apply.

[0045] Preferably, the outlet pressure of the low-pressure turbine section in the single-stage dual-flow axial turbine is 1.5 to 2 MPa, such as 1.5 MPa, 1.6 MPa, 1.7 MPa, 1.8 MPa, 1.9 MPa or 2 MPa, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the outlet pressure of the last-stage dual-flow axial turbine is atmospheric pressure.

[0047] As a preferred technical solution of the present invention, the temperature of the cold-side fluid before heat exchange in the cooler in step (1) is 15 to 25°C, such as 15°C, 16°C, 18°C, 20°C, 22°C, 24°C or 25°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, the temperature of the cold-side fluid in the cooler after heat exchange in step (1), i.e. the temperature of the hot-side fluid in the heater in step (2), is 160 to 200°C, such as 160°C, 170°C, 180°C, 190°C or 200°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] In this invention, when water is selected as the fluid in the cooler or heater under high pressure, it can still maintain the liquid phase when its temperature exceeds 100°C, but the temperature does not exceed 200°C under the pressure conditions of this invention.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] (1) The system described in this invention improves the structure of the turbine by adopting a dual-flow axial turbine and designing the axial turbine as a symmetrical two-part turbine structure, which can balance the horizontal thrust at both ends of the turbine, effectively shorten the length of the rotor shaft, increase the stability of the device operation, ensure the continuous and stable operation of the compressed air energy storage system, and improve the energy storage efficiency to more than 60%.

[0052] (2) The system improvement structure described in this invention is simple, requires no complex equipment, is easy to operate, has significant effects, low cost, and wide applicability. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the compressed air energy storage system provided in Embodiment 1 of the present invention;

[0054] Figure 2 This is a schematic diagram of the compressed air energy storage system provided in Embodiment 2 of the present invention;

[0055] Figure 3 This is a schematic diagram of the compressed air energy storage system provided in Embodiment 3 of the present invention;

[0056] Among them, 1-air compression unit, 11-first stage air compressor, 12-second stage air compressor, 13-third stage air compressor, 14-fourth stage air compressor, 15-fifth stage air compressor, 16-sixth stage air compressor, 17-seventh stage air compressor, 18-eighth stage air compressor, 21-first stage cooler, 22-second stage cooler, 23-third stage cooler, 24-fourth stage cooler, 25-fifth stage cooler, 26-sixth stage cooler, 27-seventh stage cooler, 28-eighth stage cooler, 3-compressed air storage device, 4-cold air storage device, 5-hot fluid storage device, 6-dual-flow axial turbine unit, 61- First-stage dual-flow axial turbine, 611-first-stage dual-flow axial turbine high-pressure turbine, 612-first-stage dual-flow axial turbine low-pressure turbine, 62-second-stage dual-flow axial turbine, 621-second-stage dual-flow axial turbine high-pressure turbine, 622-second-stage dual-flow axial turbine low-pressure turbine, 63-third-stage dual-flow axial turbine, 631-third-stage dual-flow axial turbine high-pressure turbine, 632-third-stage dual-flow axial turbine low-pressure turbine, 64-fourth-stage dual-flow axial turbine, 641-fourth-stage dual-flow axial turbine high-pressure turbine, 642-fourth-stage dual-flow axial turbine low-pressure turbine, 71-first-stage heater, 72-second-stage heater, 73-third-stage heater, 74-fourth-stage heater. Detailed Implementation

[0057] To better illustrate the present invention and facilitate understanding of its technical solutions, the present invention will be further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0058] The following are typical but non-limiting embodiments of the present invention:

[0059] Example 1:

[0060] This embodiment provides a compressed air energy storage system, the structural schematic diagram of which is shown below. Figure 1 As shown, it includes an air compression unit 1, a dual-flow axial turbine unit 6, a compressed air storage device 3, a cold air storage device 4, and a hot fluid storage device 5; the air compression unit 1 includes a four-stage air compressor and a four-stage cooler, with each stage of the air compressor corresponding to a stage of the cooler; the dual-flow axial turbine unit 6 includes a two-stage dual-flow axial turbine and a two-stage heater, with each stage of the dual-flow axial turbine corresponding to a stage of the heater; the dual-flow axial turbine includes two coaxial and symmetrically distributed turbine parts, with the air inlets of both turbine parts located on one side of the middle of the dual-flow axial turbine.

[0061] The outlet of the air compression unit 1 is connected to the inlet of the compressed air storage device 3, and the outlet of the compressed air storage device 3 is connected to the inlet of the dual-flow axial turbine unit 6. The cold fluid storage device 4, the cooler, the hot fluid storage device 5, and the heater constitute a fluid circulation loop.

[0062] The air compressor and cooler are arranged alternately in series.

[0063] The inlet of the first-stage air compressor 11 is connected to the atmosphere, and the outlet of the first-stage air compressor 11 is connected to the hot-side inlet of the first-stage cooler 21. The inlet of the second-stage air compressor 12 is connected to the hot-side outlet of the first-stage cooler 21, and the outlet of the second-stage air compressor 12 is connected to the hot-side inlet of the second-stage cooler 22. The inlet of the third-stage air compressor 13 is connected to the hot-side outlet of the second-stage cooler 22, and the outlet of the third-stage air compressor 13 is connected to the hot-side inlet of the third-stage cooler 23. The inlet of the fourth-stage air compressor 14 is connected to the hot-side outlet of the third-stage cooler 23, and the outlet of the fourth-stage air compressor 14 is connected to the hot-side inlet of the fourth-stage cooler 24.

[0064] The air compression unit 1 also includes an electric motor, the output shaft of which is connected to the air compressor.

[0065] The air compressor is a centrifugal compressor; the cooler is a shell-and-tube heat exchanger.

[0066] The inlet of the compressed air storage device 3 is connected to the outlet of the fourth-stage cooler 24, and the outlet of the compressed air storage device 3 is connected to the inlet of the high-pressure turbine 611 in the first-stage dual-flow axial turbine 61. The outlet of the cold fluid storage device 4 is connected to the cold-side inlets of the first-stage cooler 21, the second-stage cooler 22, the third-stage cooler 23, and the fourth-stage cooler 24, respectively. The inlet of the hot fluid storage device 5 is connected to the cold-side outlets of the first-stage cooler 21, the second-stage cooler 22, the third-stage cooler 23, and the fourth-stage cooler 24, respectively.

[0067] The compressed air storage device 3 is a high-pressure air tank; the cold fluid storage device 4 is a cold tank; and the hot fluid storage device 5 is a hot tank.

[0068] The outlet of the high-pressure turbine 611 in the first-stage dual-flow axial turbine 61 is connected to the cold-side inlet of the first-stage heater 71. The inlet of the low-pressure turbine 612 in the first-stage dual-flow axial turbine 61 is connected to the cold-side outlet of the first-stage heater 71. The outlet of the low-pressure turbine 612 in the first-stage dual-flow axial turbine 61 is connected to the inlet of the high-pressure turbine 621 in the second-stage dual-flow axial turbine 62. The outlet of the high-pressure turbine 621 in the second-stage dual-flow axial turbine 62 is connected to the cold-side inlet of the second-stage heater 72. The inlet of the low-pressure turbine 622 in the second-stage dual-flow axial turbine 62 is connected to the cold-side outlet of the second-stage heater 72. The outlet of the low-pressure turbine 622 in the second-stage dual-flow axial turbine 62 is connected to the atmosphere.

[0069] The dual-flow axial turbine unit 6 also includes a generator, the input shaft of which is connected to the dual-flow axial turbine.

[0070] The heater is a shell-and-tube heat exchanger.

[0071] Example 2:

[0072] This embodiment provides a compressed air energy storage system, the structural schematic diagram of which is shown below. Figure 2 As shown, it includes an air compression unit 1, a dual-flow axial turbine unit 6, a compressed air storage device 3, a cold air storage device 4, and a hot fluid storage device 5; the air compression unit 1 includes a six-stage air compressor and a six-stage cooler, with each stage of the air compressor corresponding to a stage of the cooler; the dual-flow axial turbine unit 6 includes a three-stage dual-flow axial turbine and a three-stage heater, with each stage of the dual-flow axial turbine corresponding to a stage of the heater; the dual-flow axial turbine includes two coaxial and symmetrically distributed turbine parts, with the air inlets of both turbine parts located on one side of the middle of the dual-flow axial turbine.

[0073] The outlet of the air compression unit 1 is connected to the inlet of the compressed air storage device 3, and the outlet of the compressed air storage device 3 is connected to the inlet of the dual-flow axial turbine unit 6. The cold fluid storage device 4, the cooler, the hot fluid storage device 5, and the heater constitute a fluid circulation loop.

[0074] The air compressor and cooler are arranged alternately in series.

[0075] The inlet of the first-stage air compressor 11 is connected to the atmosphere. The connection sequence of the first-stage air compressor 11, first-stage cooler 21, second-stage air compressor 12, second-stage cooler 22, third-stage air compressor 13, third-stage cooler 23, fourth-stage air compressor 14, and fourth-stage cooler 24 is the same as in Example 1. A fifth-stage air compressor 15, a fifth-stage cooler 25, a sixth-stage air compressor 16, and a sixth-stage cooler 26 are added, with the connection relationship as follows: the inlet of the fifth-stage air compressor 15 is connected to the hot-side outlet of the fourth-stage cooler 24. The outlet of compressor 15 is connected to the hot-side inlet of five-stage cooler 25, the inlet of six-stage air compressor 16 is connected to the hot-side outlet of five-stage cooler 25, the outlet of six-stage air compressor 16 is connected to the hot-side inlet of six-stage cooler 26, the hot-side outlet of six-stage cooler 26 is connected to compressed air storage device 3, the cold-side inlets of five-stage cooler 25 and six-stage cooler 26 are connected to the outlet of cold fluid storage device 4, and the cold-side outlets of five-stage cooler 25 and six-stage cooler 26 are connected to the inlet of hot fluid storage device 5.

[0076] The air compression unit 1 also includes an electric motor, the output shaft of which is connected to the air compressor.

[0077] The air compressor is a centrifugal compressor; the cooler is a plate heat exchanger.

[0078] The compressed air storage device 3 is a high-pressure air tank; the cold fluid storage device 4 is a cold tank; and the hot fluid storage device 5 is a hot tank.

[0079] The connection relationships of the high-pressure turbine 611, the first-stage dual-flow axial turbine 61, the first-stage heater 71, the low-pressure turbine 612 in the first-stage dual-flow axial turbine 61, the high-pressure turbine 621, the second-stage heater 72, and the low-pressure turbine 622 in the second-stage dual-flow axial turbine 62 are the same as in Embodiment 1. The high-pressure turbine 631, the third-stage heater 73, and the low-pressure turbine 632 in the third-stage dual-flow axial turbine 63 are further added. The connection relationship is as follows: the inlet of the high-pressure turbine 631 in the three-stage dual-flow axial turbine 63 is connected to the outlet of the low-pressure turbine 622 in the two-stage dual-flow axial turbine 62; the outlet of the high-pressure turbine 631 in the three-stage dual-flow axial turbine 63 is connected to the cold-side inlet of the three-stage heater 73; the inlet of the low-pressure turbine 632 in the three-stage dual-flow axial turbine 63 is connected to the cold-side outlet of the three-stage heater 73; and the outlet of the low-pressure turbine 632 in the three-stage dual-flow axial turbine 63 is connected to the atmosphere.

[0080] The dual-flow axial turbine unit 6 also includes a generator, the input shaft of which is connected to the dual-flow axial turbine.

[0081] The heater is a plate-fin heat exchanger.

[0082] Example 3:

[0083] This embodiment provides a compressed air energy storage system, the structural schematic diagram of which is shown below. Figure 3 As shown, it includes an air compression unit 1, a dual-flow axial turbine unit 6, a compressed air storage device 3, a cold air storage device 4, and a hot fluid storage device 5; the air compression unit 1 includes an eight-stage air compressor and an eight-stage cooler, with each stage of the air compressor corresponding to a stage of the cooler; the dual-flow axial turbine unit 6 includes a four-stage dual-flow axial turbine and a four-stage heater, with each stage of the dual-flow axial turbine corresponding to a stage of the heater; the dual-flow axial turbine includes two coaxial and symmetrically distributed turbine parts, with the air inlets of both turbine parts located on one side of the middle of the dual-flow axial turbine.

[0084] The outlet of the air compression unit 1 is connected to the inlet of the compressed air storage device 3, and the outlet of the compressed air storage device 3 is connected to the inlet of the dual-flow axial turbine unit 6. The cold fluid storage device 4, the cooler, the hot fluid storage device 5, and the heater constitute a fluid circulation loop.

[0085] The air compressor and cooler are arranged alternately in series.

[0086] The inlet of the first-stage air compressor 11 is connected to the atmosphere. The connection sequence of the first-stage air compressor 11, first-stage cooler 21, second-stage air compressor 12, second-stage cooler 22, third-stage air compressor 13, third-stage cooler 23, fourth-stage air compressor 14, fourth-stage cooler 24, fifth-stage air compressor 15, fifth-stage cooler 25, sixth-stage air compressor 16, and sixth-stage cooler 26 is the same as in Example 2. A seventh-stage air compressor 17, fifth-stage cooler 27, eighth-stage air compressor 18, and eighth-stage cooler 28 are added, and their connection relationship is as follows: the inlet of the seventh-stage air compressor 17 is connected to the sixth-stage cooler... The hot-side outlet of the cooler 26 is connected, the outlet of the seven-stage air compressor 17 is connected to the hot-side inlet of the seven-stage cooler 27, the inlet of the eight-stage air compressor 18 is connected to the hot-side outlet of the seven-stage cooler 27, the outlet of the eight-stage air compressor 18 is connected to the hot-side inlet of the eight-stage cooler 28, the hot-side outlet of the eight-stage cooler 28 is connected to the compressed air storage device 3, the cold-side inlets of the seven-stage cooler 27 and the eight-stage cooler 28 are connected to the outlet of the cold fluid storage device 4, and the cold-side outlets of the seven-stage cooler 27 and the eight-stage cooler 28 are connected to the inlet of the hot fluid storage device 5.

[0087] The air compression unit 1 also includes an electric motor, the output shaft of which is connected to the air compressor.

[0088] The air compressor is a centrifugal compressor; the cooler includes a shell-and-tube heat exchanger and a plate-fin heat exchanger.

[0089] The compressed air storage device 3 is a high-pressure air tank; the cold fluid storage device 4 is a cold tank; and the hot fluid storage device 5 is a hot tank.

[0090] The connection relationships of the high-pressure turbine 611, primary heater 71, low-pressure turbine 612 in the first-stage dual-flow axial turbine 61, high-pressure turbine 621, secondary heater 72, low-pressure turbine 622 in the second-stage dual-flow axial turbine 62, and high-pressure turbine 631, tertiary heater 73, and low-pressure turbine 632 in the third-stage dual-flow axial turbine 63 are the same as in Embodiment 2. The connection relationship of the high-pressure turbine 641 and tertiary heater 622 in the fourth-stage dual-flow axial turbine 64 is further added. The low-pressure turbine 642 in the four-stage dual-flow axial turbine 64 is connected as follows: the inlet of the high-pressure turbine 641 in the four-stage dual-flow axial turbine 64 is connected to the outlet of the low-pressure turbine 632 in the three-stage dual-flow axial turbine 63; the outlet of the high-pressure turbine 641 in the four-stage dual-flow axial turbine 64 is connected to the cold-side inlet of the four-stage heater 74; the inlet of the low-pressure turbine 642 in the four-stage dual-flow axial turbine 64 is connected to the cold-side outlet of the four-stage heater 74; and the outlet of the low-pressure turbine 642 in the four-stage dual-flow axial turbine 64 is connected to the atmosphere.

[0091] The dual-flow axial turbine unit 6 also includes a generator, the input shaft of which is connected to the dual-flow axial turbine.

[0092] The heater includes a shell-and-tube heat exchanger and a plate heat exchanger.

[0093] Example 4:

[0094] This embodiment provides a method for storing and releasing energy using compressed air. The method employs the system described in Embodiment 1 and includes the following steps:

[0095] (1) After being compressed by the first-stage air compressor 11, the air's temperature and pressure increase to 190°C and 0.3 MPa. The air exchanges heat with the cold water in the first-stage cooler 21, causing its temperature to drop to 30°C. The cold-side water in the first-stage cooler 21 then flows to a heat tank to store heat. After being compressed by the second-stage air compressor 12, the air's temperature and pressure increase to 190°C and 1 MPa. The air exchanges heat with the cold water in the second-stage cooler 22, causing its temperature to drop to 35°C. The cold-side water in the second-stage cooler 22 then flows to a heat tank to store heat. The air then passes through the third-stage air compressor 1... After compression, the air temperature and pressure increase to 190℃ and 3MPa. The air exchanges heat with the cold water in the three-stage cooler 23, and the temperature drops to 40℃. The cold-side water temperature of the three-stage cooler 23 increases and flows into the hot tank to store heat. After compression by the four-stage air compressor 14, the air temperature and pressure increase to 190℃ and 7.5MPa. The air exchanges heat with the cold water in the four-stage cooler 24, and the temperature drops to 42℃. The cold-side water temperature of the four-stage cooler 24 increases and flows into the hot tank to store heat. After passing through the four-stage cooler 24, the air flows into the high-pressure gas tank to store pressure potential energy.

[0096] (2) Air flows from the high-pressure tank to the high-pressure turbine 611 in the first-stage dual-flow axial turbine 61 to expand and do work. The inlet pressure is 7.5 MPa and the outlet pressure is 6 MPa. The air exchanges heat with the hot-side water of the first-stage heater 71. The air inlet temperature of the first-stage heater 71 is 35°C and the outlet temperature is 185°C. After being heated, the air enters the low-pressure turbine 612 in the first-stage dual-flow axial turbine 61 to expand and do work, and the pressure drops to 3 MPa. The air flows out from the low-pressure turbine 612 in the first-stage dual-flow axial turbine 61 to the high-pressure turbine 621 in the second-stage dual-flow axial turbine 62 to expand and do work, and the pressure drops to 1 MPa. The air exchanges heat with the hot-side water of the second-stage heater 72. The air inlet temperature of the second-stage heater 72 is 35°C and the outlet temperature is 185°C. After being heated, the air enters the low-pressure turbine 622 in the second-stage dual-flow axial turbine 62 to expand and do work, and the pressure drops to atmospheric pressure.

[0097] Example 5:

[0098] This embodiment provides a method for storing and releasing energy using compressed air. The method employs the system described in Embodiment 2 and includes the following steps:

[0099] (1) After being compressed by the first-stage air compressor 11, the air temperature and pressure increase to 180°C and 0.4 MPa. The air exchanges heat with the cold water in the first-stage cooler 21, and the temperature drops to 40°C. The cold-side water in the first-stage cooler 21 increases in temperature and flows into a hot tank to store heat. After being compressed by the second-stage air compressor 12, the air temperature and pressure increase to 180°C and 0.9 MPa. The air exchanges heat with the cold water in the second-stage cooler 22, and the temperature drops to 35°C. The cold-side water in the second-stage cooler 22 increases in temperature and flows into a hot tank to store heat. After being compressed by the third-stage air compressor 13, the air temperature and pressure increase to 180°C and 2.5 MPa. The air exchanges heat with the cold water in the third-stage cooler 23, and the temperature drops to 30°C. The cold-side water in the third-stage cooler 23 increases in temperature and flows into a hot tank to store heat. The air then passes through the fourth-stage air compressor... After compression by compressor 14, the air's temperature and pressure increase to 180°C and 5MPa. It then exchanges heat with the cold water in the fourth-stage cooler 24, causing its temperature to drop to 38°C. The cold-side water in the fourth-stage cooler 24 heats up and flows into a hot tank to store heat. After compression by the fifth-stage air compressor 15, the air's temperature and pressure increase to 180°C and 7MPa. It then exchanges heat with the cold water in the fifth-stage cooler 25, causing its temperature to drop to 25°C. The cold-side water in the fifth-stage cooler 25 heats up and flows into a hot tank to store heat. After compression by the sixth-stage air compressor 16, the air's temperature and pressure increase to 180°C and 9MPa. It then exchanges heat with the cold water in the sixth-stage cooler 26, causing its temperature to drop to 32°C. The cold-side water in the sixth-stage cooler 26 heats up and flows into a hot tank to store heat. Finally, after passing through the sixth-stage cooler 26, the air flows into a high-pressure tank to store pressure potential energy.

[0100] (2) Air flows from the high-pressure tank to the high-pressure turbine 611 in the first-stage dual-flow axial turbine 61 for expansion and work. The inlet pressure is 9 MPa and the outlet pressure is 7.5 MPa. The air exchanges heat with the hot-side water of the first-stage heater 71. The air's inlet temperature in the first-stage heater 71 is 35°C and the outlet temperature is 175°C. After being heated, the air enters the low-pressure turbine 612 in the first-stage dual-flow axial turbine 61 for expansion and work, reducing the pressure to 4.5 MPa. The air flows out from the low-pressure turbine 612 in the first-stage dual-flow axial turbine 61 to the high-pressure turbine 621 in the second-stage dual-flow axial turbine 62 for expansion and work, reducing the pressure to 2.3 MPa. The air exchanges heat with the hot-side water of the second-stage heater 72. In the water heat exchange stage, the air in the secondary heater 72 has an inlet temperature of 35°C and an outlet temperature of 175°C. After being heated, the air enters the low-pressure turbine 622 of the secondary dual-flow axial turbine 62 for expansion and work, reducing the pressure to 1 MPa. The air then flows from the low-pressure turbine 622 of the secondary dual-flow axial turbine 62 to the high-pressure turbine 631 of the tertiary dual-flow axial turbine 63 for expansion and work, reducing the pressure to 0.4 MPa. The air then exchanges heat with the hot-side water of the tertiary heater 73. The air in the tertiary heater 73 has an inlet temperature of 35°C and an outlet temperature of 175°C. After being heated, the air enters the low-pressure turbine 632 of the tertiary dual-flow axial turbine 63 for expansion and work, reducing the pressure to atmospheric pressure.

[0101] Example 6:

[0102] This embodiment provides a method for storing and releasing energy using compressed air. The method employs the system described in Embodiment 3 and includes the following steps:

[0103] (1) After being compressed by the first-stage air compressor 11, the air's temperature and pressure increase to 170°C and 0.3 MPa. The air exchanges heat with the cold water in the first-stage cooler 21, causing its temperature to drop to 40°C. The cold-side water in the first-stage cooler 21 then increases in temperature and flows into a hot water tank to store heat. This process is repeated through the second-stage air compressor 12, the second-stage cooler 22, the third-stage air compressor 13, the third-stage cooler 23, the fourth-stage air compressor 14, the fourth-stage cooler 24, the fifth-stage air compressor 15, the fifth-stage cooler 25, the sixth-stage air compressor 16, and the sixth-stage cooler 26. The air then undergoes a seventh-stage air compression. After compression by compressor 7, the temperature and pressure increase to 170°C and 10MPa. The air exchanges heat with the cold water in the seventh-stage cooler 27, and the temperature drops to 40°C. The cold-side water in the seventh-stage cooler 27 increases in temperature and flows into the hot tank to store heat. After compression by the eighth-stage air compressor 18, the temperature and pressure increase to 170°C and 13MPa. The air exchanges heat with the cold water in the eighth-stage cooler 28, and the temperature drops to 28°C. The cold-side water in the eighth-stage cooler 28 increases in temperature and flows into the hot tank to store heat. After passing through the eighth-stage cooler 28, the air flows into the high-pressure gas tank to store pressure potential energy.

[0104] (2) Air flows from the high-pressure tank to the high-pressure turbine 611 in the first-stage dual-flow axial turbine 61 for expansion and work. The inlet pressure is 13 MPa and the outlet pressure is 11.5 MPa. The air exchanges heat with the hot-side water of the first-stage heater 71. The air's inlet temperature in the first-stage heater 71 is 30°C and its outlet temperature is 165°C. After being heated, the air enters the low-pressure turbine 612 in the first-stage dual-flow axial turbine 61 for expansion and work, and the pressure drops to 8 MPa. This process is repeated, passing through the high-pressure turbine 621 in the second-stage dual-flow axial turbine 62, the second-stage heater 72, and the low-pressure turbine 612 in the second-stage dual-flow axial turbine 62. 22. The high-pressure turbine 631, the three-stage dual-flow axial turbine 63, the three-stage heater 73, and the low-pressure turbine 632 in the three-stage dual-flow axial turbine 63; the air flows from the low-pressure turbine 632 in the three-stage dual-flow axial turbine 63 to the high-pressure turbine 641 in the four-stage dual-flow axial turbine 64 to expand and do work, and the pressure drops to 0.28 MPa. The air exchanges heat with the hot-side water of the four-stage heater 74. The air inlet temperature of the four-stage heater 74 is 30°C and the outlet temperature is 165°C. After being heated, the air enters the low-pressure turbine 642 in the four-stage dual-flow axial turbine 64 to expand and do work, and the pressure drops to atmospheric pressure.

[0105] The compressed air energy storage power generation system and method described in the above embodiments have strong operational stability and can improve energy storage efficiency to over 60%.

[0106] As can be seen from the above embodiments, the system of the present invention improves the turbine structure by adopting a dual-flow axial turbine, designing the axial turbine as a symmetrical two-part turbine structure. This balances the horizontal thrust at both ends of the turbine, effectively shortens the rotor shaft length, increases the stability of the device operation, ensures the continuous and stable operation of the compressed air energy storage system, and improves the energy storage efficiency to over 60%. The improved system structure is simple, requires no complex equipment, is easy to operate, has significant effects, low cost, and a wide range of applications.

[0107] The present invention has been illustrated with the above embodiments to describe the detailed system and method of the present invention. However, the present invention is not limited to the detailed system and method described above, that is, it does not mean that the present invention must rely on the detailed system and method described above to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the system of the present invention, additions of auxiliary equipment, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A compressed air energy storage system, characterized in that, The system includes an air compression unit, a dual-flow axial turbine unit, a compressed air storage device, and a cold and hot fluid storage device; the air compression unit includes a multi-stage air compressor and a multi-stage cooler, with each stage of the air compressor corresponding to a stage of the cooler. The air compressors and coolers are arranged alternately in series; the inlet of the first-stage air compressor is connected to the atmosphere, the inlets of the remaining air compressors are connected to the hot-side outlet of the previous stage cooler, the outlets of each air compressor are connected to the hot-side inlets of the corresponding stage coolers, and the outlet of the last stage cooler is connected to the inlet of the compressed air storage device. The dual-flow axial turbine unit includes a multi-stage dual-flow axial turbine and a multi-stage heater. Each stage of the dual-flow axial turbine corresponds to a stage of heater. The dual-flow axial turbine includes two turbine parts that are coaxial and symmetrically distributed in the same cylinder. The air inlets of the two turbine parts are located on one side of the middle of the dual-flow axial turbine. The dual-flow axial turbine consists of two turbine sections, a high-pressure turbine and a low-pressure turbine, arranged sequentially according to the order of compressed air flow. A heater corresponding to the first-stage dual-flow axial turbine is located between the high-pressure and low-pressure turbines, following the same compressed air flow order. The outlet of the high-pressure turbine is connected to the cold-side inlet of the heater, the cold-side outlet of the heater is connected to the inlet of the low-pressure turbine, and the outlet of the low-pressure turbine is connected to the inlet of the high-pressure turbine in the next stage of the dual-flow axial turbine. The dual-flow axial turbine unit also includes a generator, which is coaxially connected to the multi-stage dual-flow axial turbine. The outlet of the air compression unit is connected to the inlet of the compressed air storage device, and the outlet of the compressed air storage device is connected to the inlet of the dual-flow axial turbine unit. The cold fluid storage device, cooler, hot fluid storage device, and heater constitute a fluid circulation loop. The outlet of the cold fluid storage device is connected to the cold side inlet of each stage of cooler, the cold side outlet of each stage of cooler is connected to the inlet of the hot fluid storage device, the outlet of the hot fluid storage device is connected to the hot side inlet of each stage of heater, and the hot side outlet of each stage of heater is connected to the inlet of the cold fluid storage device.

2. The compressed air energy storage system according to claim 1, characterized in that, Both the air compressor and the cooler have at least three stages.

3. The compressed air energy storage system according to claim 2, characterized in that, Both the air compressor and the cooler have 4 to 8 stages.

4. The compressed air energy storage system according to claim 1, characterized in that, The air compression unit also includes an electric motor, the output shaft of which is connected to the air compressor.

5. The compressed air energy storage system according to claim 1, characterized in that, The air compressor includes a centrifugal compressor.

6. The compressed air energy storage system according to claim 1, characterized in that, The cooler includes any one or a combination of at least two of the following: shell-and-tube heat exchangers, plate heat exchangers, or plate-fin heat exchangers.

7. The compressed air energy storage system according to claim 1, characterized in that, The compressed air storage device includes a high-pressure air tank.

8. The compressed air energy storage system according to claim 1, characterized in that, Both the dual-flow axial turbine and the heater comprise at least two stages.

9. The compressed air energy storage system according to claim 8, characterized in that, Both the dual-flow axial turbine and the heater consist of 2 to 4 stages.

10. The compressed air energy storage system according to claim 8, characterized in that, The inlet of the first-stage dual-flow axial turbine is connected to the outlet of the compressed air storage device, and the outlet of the last-stage dual-flow axial turbine is open to the atmosphere.

11. The compressed air energy storage system according to claim 1, characterized in that, The heater includes any one or a combination of at least two of the following: shell-and-tube heat exchangers, plate heat exchangers, or plate-fin heat exchangers.

12. The compressed air energy storage system according to claim 1, characterized in that, The cold fluid storage device includes a cold tank, and the hot fluid storage device includes a hot tank.

13. The compressed air energy storage system according to claim 1, characterized in that, The medium in the cold fluid storage device and the hot fluid storage device is water.

14. A method for storing and releasing energy in compressed air using the system described in any one of claims 1-13, characterized in that, The method includes the following steps: (1) After the air is compressed, the temperature and pressure increase. After the cold side fluid of the cooler exchanges heat, it flows to the compressed air storage device to store the pressure potential energy. At the same time, the temperature of the cold side fluid of the cooler increases after heat exchange, and the heat is stored to form a hot fluid. (2) Release the compressed air obtained in step (1) and let it flow to the high-pressure turbine part of the dual-flow axial turbine to expand and do work. Then it exchanges heat with the hot side fluid of the heater and flows to the low-pressure turbine part of the dual-flow axial turbine to expand and do work until it is discharged. At the same time, the temperature of the hot side fluid of the heater decreases and it is returned to be used as a cold fluid.

15. The method according to claim 14, characterized in that, The air compression and cooling operations described in step (1) are repeated multiple times.

16. The method according to claim 15, characterized in that, The air compression and cooling operation described in step (1) is performed 4 to 8 times.

17. The method according to claim 14, characterized in that, The air temperature at the outlet of the primary compressor is 170~200℃, and the pressure is 0.3~0.5MPa.

18. The method according to claim 14, characterized in that, After passing through the first-stage cooler, the temperature of the compressed air drops to 20~50℃, and the outlet temperature of each subsequent cooler is independently 20~50℃.

19. The method according to claim 14, characterized in that, The pressure loss of each stage cooler is 0 to 0.05 MPa independently.

20. The method according to claim 14, characterized in that, The pressure of the compressed air at the outlet of the last stage compressor is 7~13MPa.

21. The method according to claim 14, characterized in that, The operation of expanding and heating the compressed air in step (2) is repeated multiple times.

22. The method according to claim 21, characterized in that, The operation of expanding and heating the compressed air in step (2) is repeated 2 to 4 times.

23. The method according to claim 14, characterized in that, The inlet pressure of the high-pressure turbine section in a single-stage dual-flow axial turbine is 7~13MPa, and the outlet pressure is 6~12MPa.

24. The method according to claim 14, characterized in that, The inlet temperature of the compressed air in the primary heater is 25~35℃, and the outlet temperature is 155~195℃.

25. The method according to claim 14, characterized in that, The pressure loss of each heater stage is 0 to 0.05 MPa independently.

26. The method according to claim 14, characterized in that, The outlet pressure of the low-pressure turbine section in a single-stage dual-flow axial turbine is 3~8MPa.

27. The method according to claim 14, characterized in that, The outlet pressure of the final stage dual-flow axial turbine is atmospheric pressure.

28. The method according to claim 14, characterized in that, In step (1), the temperature of the cold-side fluid in the cooler before heat exchange is 15~25℃.

29. The method according to claim 14, characterized in that, The temperature of the cold-side fluid in the cooler after heat exchange in step (1), i.e. the temperature of the hot-side fluid in the heater in step (2), is 160~200℃.

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