A distributed compressed air segmented compression energy storage device and method thereof

Abstract

This invention discloses a distributed compressed air segmented compression energy storage device and method, belonging to the field of energy storage technology. The low-pressure compressor of this invention delivers medium-pressure air to an intercooler, which is connected to a storage tank and a buffer tank, with valves installed on both connecting pipelines. High-pressure air compressed by the high-pressure compressor enters an aftercooler, which is connected to the storage tank. Pressure sensors are installed in both the buffer tank and the storage tank. The low-temperature tank of the heat storage unit is connected to both the intercooler and the aftercooler. The second outlets of both the aftercooler and the intercooler are connected to a high-temperature tank. Valves are also installed on the first and second heat absorption pipelines. A control center receives the pressure values ​​detected by the pressure sensors and adjusts the opening and closing of the valves based on the detected pressure values. The control center also adjusts the speed of the first motor based on the pressure values ​​detected by the pressure sensor in the buffer tank. This invention can significantly improve system efficiency and operational stability.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, specifically to a distributed compressed air segmented compression energy storage device and method. Background Technology

[0002] Energy storage technology, as a key means to improve the flexibility and stability of the power system, can effectively mitigate the uncertainty caused by fluctuations in renewable energy output and promote the efficient use of energy. Among various energy storage technologies, compressed air energy storage systems have attracted widespread attention due to their large-scale energy storage capacity. However, traditional centralized compressed air energy storage systems have significant limitations in practical applications: on the one hand, their systems are bulky and typically rely on large high-pressure containers or specific underground geological structures to store high-pressure air, making it difficult to flexibly adapt to the spatial adaptability and deployment flexibility requirements of distributed energy scenarios; on the other hand, the overall efficiency of such systems is relatively low under non-steady-state variable operating conditions.

[0003] Compared to centralized systems, distributed energy storage systems have significant advantages in terms of spatial adaptability and equipment integration, making them more suitable for flexible and dispersed application scenarios. However, despite the advantages of distributed systems in terms of structure and deployment, existing distributed systems still face challenges—under varying operating conditions, the overall system efficiency is prone to decrease, and there are also issues with insufficient reliability, which restricts their large-scale application and development. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems in the prior art and provide a distributed compressed air segmented compression energy storage device and method, which can improve the overall operating efficiency of the system under variable operating conditions, while also improving the operational reliability.

[0005] The distributed compressed air segmented compression energy storage device of the present invention includes an air compression unit, comprising a low-pressure compressor, an intercooler, a buffer tank, a high-pressure compressor, an aftercooler, and a storage tank connected in sequence. The outlet of the low-pressure compressor is connected to the first inlet of the intercooler, and the first outlet of the intercooler is connected to the storage tank and the buffer tank respectively through two connecting pipes, each of which is equipped with a valve. The first outlet of the aftercooler is connected to the storage tank. The low-pressure compressor is connected to a first electric motor. The high-pressure compressor is connected to a second electric motor. Pressure sensors are installed in both the buffer tank and the storage tank. The air is compressed by the low-pressure compressor, cooled by the intercooler, and then enters the storage tank or the buffer tank. The air in the buffer tank is sequentially compressed by the high-pressure compressor, cooled by the aftercooler, and then enters the storage tank.

[0006] A heat storage unit includes a low-temperature tank for storing a low-temperature heat storage medium and a high-temperature tank for storing a high-temperature medium. The low-temperature tank is connected to the second inlet of an intercooler via a first heat absorption pipe, and the second outlet of the intercooler is connected to the high-temperature tank. The low-temperature tank is also connected to the second inlet of an aftercooler via a second heat absorption pipe, and the second outlet of the aftercooler is connected to the high-temperature tank. Valves are also provided on both the first heat absorption pipe and the second heat absorption pipe.

[0007] The control center is connected to the pressure sensors and the signals of each valve. The control center is used to receive the pressure values ​​detected by the pressure sensors and to regulate the opening and closing of each valve according to the detected pressure values. The control center is also used to regulate the speed of the first motor according to the pressure values ​​detected by the pressure sensors in the buffer tank.

[0008] Preferably, the first motor, the low-pressure compressor, the high-pressure compressor, and the second motor are coaxially connected, and a first 3S clutch is provided on the shaft between the low-pressure compressor and the high-pressure compressor, and a second 3S clutch is provided on the shaft between the high-pressure compressor and the second motor. The second motor is equipped with a speed sensor. The first 3S clutch, the second 3S clutch, and the speed sensor are all signal-connected to the control center. The control center is used to receive the speed signal from the speed sensor and regulate the closing and opening of the first 3S clutch and the second 3S clutch according to the speed signal.

[0009] Preferably, both the low-pressure compressor and the high-pressure compressor include an impeller, a blade diffuser, and a volute. The impeller is located at the center of the compressor unit and consists of a wheel disk and several three-dimensional twisted blades. The impeller hub is thickened, and the thickness distribution adopts a Spine curve to achieve a smooth gradient from the impeller inlet area to the outlet area.

[0010] The blade diffuser is adapted to the impeller, and the airflow angle at the blade inlet of the blade diffuser matches the airflow angle at the impeller outlet, so that the streamline transition from the impeller outlet to the blade diffuser inlet is uniform. The blade thickness of the blade diffuser adopts a Bezier curve along the chord direction.

[0011] The cross-sectional area of ​​the flow channel of the volute gradually increases along the circumference, and its inner wall profile adopts a multi-segment involute arc and an asymmetric flow channel section is selected.

[0012] Preferably, the radius of the rounded corner of the worm tongue is 10mm to 20mm.

[0013] The present invention also discloses a segmented compression energy storage method for the above-mentioned distributed compressed air segmented compression energy storage device, comprising the following steps:

[0014] The air at normal temperature and pressure is first compressed at low pressure to increase its pressure to the same as that of the storage tank. Then, the compressed air and the heat storage medium exchange heat for the first time: the air releases heat and cools down before being stored in the storage tank, while the heat storage medium absorbs heat and heats up before being stored as well. This completes the first stage of energy storage.

[0015] When the pressure in the gas storage tank rises to the same level as the pressure in the buffer tank, the second energy storage stage is initiated. At this time, the compressed air, after releasing heat and cooling down, first enters the buffer tank for buffering. During this process, the pressure inside the buffer tank needs to be kept stable. The air after buffering in the buffer tank is then compressed under high pressure. The air after being compressed again undergoes a second heat exchange with the heat storage medium that has already completed the first heat exchange, further releasing heat before being stored in the gas storage tank. The heat storage medium, after absorbing heat twice, is heated to a higher temperature and stored, thus completing the second energy storage stage.

[0016] When the low-pressure compressor and the high-pressure compressor reach the same speed, they are driven by the same motor, and the system enters the third energy storage stage. The energy storage process continues until the pressure in the gas storage tank reaches the set upper limit, at which point the entire energy storage process ends.

[0017] Preferably, before the start of the first energy storage stage, the valves on the connecting pipeline between the first outlet of the intercooler and the gas storage tank and the buffer tank, as well as the valves on the first heat absorption pipeline and the second heat absorption pipeline, are all in the closed state, and the buffer tank and the gas storage tank contain air at different pressures.

[0018] Preferably, when the energy storage process starts, the control center controls the valves on the connecting pipeline between the first outlet of the intercooler and the gas storage tank, as well as the valves on the first heat absorption pipeline between the cryogenic tank and the intercooler, to open, and the first energy storage stage begins. At room temperature and pressure air enters the low-pressure compressor, and the first electric motor drives the low-pressure compressor to compress the at room temperature and pressure air.

[0019] Preferably, before the second energy storage stage, the pressure sensor is used to monitor the pressure in the gas storage tank and the buffer tank. When the pressure in the gas storage tank is the same as that in the buffer tank, the control center controls the valves on the connecting pipeline between the intercooler and the buffer, and the valves on the connecting pipeline between the cryogenic tank and the first inlet of the aftercooler to be opened, and closes the valve on the connecting pipeline between the first outlet of the intercooler and the gas storage tank.

[0020] Preferably, in the second energy storage stage, the speed of the first motor is adjusted according to the pressure of the buffer tank. When the pressure sensor detects that the pressure of the buffer tank is lower than the set value, the speed of the first motor is increased; if the pressure of the buffer tank is higher than the set value, the speed of the first motor is decreased.

[0021] Preferably, the working pressure of the buffer tank is 360 kPa to 400 kPa, the initial pressure of the gas storage tank is 120 kPa to 150 kPa, and the upper limit of the gas storage tank pressure is 900 kPa to 950 kPa.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention employs a low-pressure compressor and a high-pressure compressor to perform segmented compression and energy storage of air. The low-pressure compressor can operate independently, and the low-pressure and high-pressure compressors can also operate in coordination to adapt to different pressure ranges. Simultaneously, by monitoring the pressure signal of the air storage tank and flexibly adjusting the operating modes of the low-pressure and high-pressure compressors based on the pressure signals in the air storage tank and buffer tank, both the low-pressure and high-pressure compressors have stable operating ranges, significantly improving system efficiency and operational stability. This solves the problem that the overall operating efficiency of existing distributed systems tends to decrease under varying operating conditions, and that there is insufficient reliability.

[0024] This invention employs segmented compression energy storage, reducing the limitation imposed by compressor operating conditions on the minimum operating pressure of the gas storage tank, broadening the operating pressure range of the gas storage tank, and effectively improving volume utilization. For the same energy storage capacity, the tank volume can be significantly reduced, making the system more compact and facilitating distributed system layout.

[0025] In order to adapt to the stable operation requirements of the compressor under a wide range of pressure changes, the present invention has made special designs for the low-pressure compressor and the high-pressure compressor. The optimized low-pressure compressor and the high-pressure compressor have the advantages of compact structure, high efficiency and high reliability. Attached Figure Description

[0026] Figure 1 This is a flowchart of the energy storage system structure according to an embodiment of the present invention.

[0027] Figure 2 This is a three-dimensional view of the compressor structure according to an embodiment of the present invention.

[0028] Figure 3 This is a front view of the impeller in an embodiment of the present invention.

[0029] Figure 4 This is a top view of the impeller in an embodiment of the present invention.

[0030] Figure 5 This is a cross-sectional view of the impeller portion of an embodiment of the present invention.

[0031] Figure 6 This is a schematic diagram of the volute structure according to an embodiment of the present invention.

[0032] Figure 7 This is a schematic diagram of the compressor's operating flow rate and output power according to an embodiment of the present invention.

[0033] Figure label:

[0034] 1. Low-pressure compressor; 2. Intercooler; 3. Buffer tank; 4. High-pressure compressor; 5. Aftercooler; 6. Gas receiver; 7. Cryogenic tank; 8. High-temperature tank; 11. First control valve; 12. Second control valve; 13. Third control valve; 14. Fourth control valve; 15. First 3S clutch; 16. Second 3S clutch; 21. First electric motor; 22. Second electric motor; 30. Control center; 31. Speed ​​sensor; 32. Pressure sensor. Detailed Implementation

[0035] 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, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” indicate that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; when the absolute position of the described objects changes, the relative positional relationship may also change accordingly.

[0037] like Figure 1As shown, this invention provides a distributed compressed air segmented compression energy storage device, including a gas compression unit, a heat storage unit, and a control center. The gas compression unit includes a low-pressure compressor 1, an intercooler 2, a buffer tank 3, a high-pressure compressor 4, an aftercooler 5, and a gas storage tank 6 connected in sequence. The inlet of the low-pressure compressor 1 is connected to the atmosphere, and the outlet is connected to the first inlet of the intercooler 2 to absorb heat from the medium-pressure gas. The first outlet of the intercooler 2 is divided into two paths: one path goes directly into the gas storage tank 6 through a first control valve 11; the other path is connected to the inlet of the buffer tank 3 through a second control valve 12. The outlet of the buffer tank 3 is connected to the inlet of the high-pressure compressor 4, and the outlet of the high-pressure compressor 4 is connected to the first inlet of the aftercooler 5 to further absorb heat from the high-pressure gas. The first outlet of the aftercooler 5 is connected to the second inlet of the gas storage tank 6.

[0038] like Figure 1 As shown, the first motor 21, the low-pressure compressor 1, the high-pressure compressor 4, and the second motor 22 are coaxially connected. A first 3S clutch 15 is provided on the shaft between the low-pressure compressor 1 and the high-pressure compressor 4, and a second 3S clutch 16 is provided on the shaft between the high-pressure compressor 4 and the second motor 22.

[0039] like Figure 1 As shown, the heat storage module is used to absorb and store heat during compression, reducing compression power consumption. The system is equipped with a low-temperature tank 7 and a high-temperature tank 8. The outlet of the low-temperature tank 7 is divided into two paths: one path is connected to the second inlet of the intercooler 2 via the third control valve 13; the other path is connected to the second inlet of the aftercooler 5 via the fourth control valve 14. The outlets of the aftercooler 5 and the second outlet of the intercooler 2 are connected to the inlet of the high-temperature tank 8.

[0040] like Figure 1 As shown, a speed sensor 31 is arranged at the shaft end of the second motor 22 to transmit the component speed signal to the control center 30; a pressure sensor 32 is arranged in the air tank 6 to transmit the internal pressure signal of the component to the control center 30. The control center 30 is connected to the first control valve 11, the second control valve 12, the third control valve 13, the fourth control valve 14, the first 3S clutch 15, and the second 3S clutch 16 via signal lines to adjust the opening degree of the control valves and the state of the clutches.

[0041] Because the system has a large pressure ratio variation range, the low-pressure compressor and high-pressure compressor in this embodiment have been specially designed to adapt to this wide range of changes and to ensure a certain degree of operational stability. For example... Figure 2 As shown, the compressor includes an impeller A, a blade diffuser B, and a volute C. The impeller A is located at the center of the compressor and consists of a disc and several three-dimensional twisted blades, as shown in the figure. Figure 3 The angle formed by the tangent of the impeller blade airfoil at the centerline of the leading edge and the rotor axis is the inlet blade angle α. Figure 4As shown, the angle formed by the tangent of the impeller blade airfoil at the centerline of the trailing edge and the rotor radius is the outlet blade angle β. In this embodiment, the inlet blade angle α on the hub surface is different from that on the cover surface, which can effectively compensate for the inlet flow angle deviation caused by the difference in airflow velocity at different radial positions, allowing the airflow to enter the blade channel more smoothly. The outlet blade angle β on the hub surface and the cover surface is the same, which can make the outlet airflow distribution more uniform, reduce three-dimensional distortion and endwall loss, improve diffuser inlet conditions, thereby improving efficiency and operational stability, while simplifying manufacturing.

[0042] like Figure 5 As shown, the impeller's inlet inner diameter is D1, its inlet outer diameter is D2, and its outer diameter is D3. To meet the system's miniaturization design requirements, D1, D2, and D3 are designed to have a large inlet and a small outlet, resulting in a compressor impeller geometry with a large inlet area and a relatively small outlet area in this embodiment. This design aims to reduce the relative Mach number of the airflow entering the impeller, mitigate flow impact, and simultaneously create a strong compression effect at the impeller outlet.

[0043] To adapt to the high-speed operating conditions required by the system, and to ensure that the impeller back plate meets the structural strength requirements, the hub thickness x of the low-pressure compressor and the high-pressure compressor in this embodiment has been specially thickened. Its thickness distribution is defined using a Spine curve or a similar smooth continuous function, achieving a smooth gradient from the impeller inlet region to the outlet region, effectively avoiding stress concentration and improving the impeller's operational reliability.

[0044] In this embodiment, both the low-pressure compressor and the high-pressure compressor include blade diffusers and volutes that match the impellers. The geometric parameters of the blade diffuser, including the number of blades, inner and outer diameters, and inlet / outlet airflow angles, are all integrated and optimized based on the outlet airflow conditions of the upstream impeller. The core design principle is that the inlet airflow angle of the diffuser blades is highly matched to the outlet airflow angle of the impeller. This high matching refers to a smooth transition of the streamline from the impeller outlet to the diffuser inlet, allowing for smoother airflow entry into the diffuser for diffusion. Specifically, the matching of the diffuser blade inlet airflow angle and the impeller outlet airflow angle can be iteratively optimized through CFD simulation. More specifically, the impeller outlet airflow angle can be determined first, then simulated according to this angle, and the diffuser blade inlet airflow angle can be corrected based on the results to minimize aerodynamic losses caused by dynamic and static interference. Simultaneously, the outlet airflow angle is designed to achieve efficient airflow deceleration and diffusion. To balance structural strength and aerodynamic performance, the diffuser blade thickness is defined along the chord direction using a Bezier curve or a similar parametric curve, achieving a continuous and smooth transition in thickness distribution.

[0045] like Figure 6As shown, the volute is used to collect airflow from the diffuser and further diffuse it. Its flow channel cross-sectional area gradually increases circumferentially, and the inner wall profile adopts a multi-segment involute arc or a similar involute profile, with an asymmetric flow channel cross-section. The geometric parameters of the volute, such as the inlet cross-sectional radius *a*, the outlet channel diameter *b*, and the outlet diffuser section length *c*, are all matched to the upstream diffuser and downstream piping system. Specifically, the volute tongue (… Figure 6 The geometry of the region (r shown in the middle) has been optimized. If the radius of curvature of the volute tongue is too large, it will have a significant impact on airflow. If it is too small, it will be difficult to process and manufacture. As a preferred embodiment, in order to ensure convenient processing and manufacturing, the radius of curvature of the volute tongue is not less than 10mm. At the same time, in order to ensure smooth airflow, the radius of curvature is less than 20mm. Therefore, 15mm is selected.

[0046] It features a suitable aerodynamic shape and radius of curvature to reduce airflow separation and pressure pulsation at this location. In this embodiment, the integrated diffuser and volute design enable good aerodynamic coupling with the impeller, forming a highly efficient compressor stage that provides sufficiently smooth diffusion, thereby improving the overall system's operating efficiency and stability.

[0047] In the distributed compressed air energy storage system of this embodiment, the significant advantages of using the aforementioned multi-stage centrifugal compressor in the compression energy storage stage are as follows:

[0048] Wide operating conditions and high efficiency: Centrifugal compressors have a wide high-efficiency operating range and can adapt well to the variable operating conditions of large pressure changes in the gas storage tank during energy storage, thus ensuring that the system can maintain high overall efficiency throughout the entire charge and discharge cycle.

[0049] High power density: Centrifugal / centripetal impeller machinery has a compact structure and high rotational speed, enabling it to handle large flow rates of working fluids and achieve high pressure ratios or expansion ratios within a small physical size. This characteristic is highly consistent with the goals of this invention: system miniaturization, compactness, and flexible distributed deployment.

[0050] Stable and reliable operation: Compared with other types of turbomachinery, the centrifugal impeller in this embodiment has a more robust structure, is not sensitive to changing operating conditions, operates stably, and has high reliability, which can meet the requirements for long-term stable operation of distributed energy stations.

[0051] like Figure 1 As shown, this embodiment also provides a distributed compressed air segmented compression energy storage method, including the following steps:

[0052] Normal temperature and pressure air is introduced into the low-pressure compressor 1 for compression to obtain medium temperature and medium pressure air. This medium temperature and medium pressure air then enters the intercooler 2 for cooling and is subsequently sent to the storage tank 6. The low-temperature heat storage medium in the low-temperature tank 7 absorbs heat and enters the high-temperature tank 8 for storage. For example, the heat storage medium in this embodiment can be quartz sand, ceramic balls, refractory bricks, molten salt, heat transfer oil, or paraffin wax, etc. When the pressure in the storage tank 6 reaches the same level as that in the buffer tank 3, the medium-pressure air is sent to the buffer tank 3 and then enters the high-pressure compressor 4 for further compression. After compression, the medium-pressure air enters the aftercooler 5 to release heat and cool down, and then enters the storage tank 6 for storage. The low-temperature heat storage medium from the low-temperature tank 7 absorbs heat and heats up in both the intercooler 2 and the aftercooler 5 before entering the high-temperature tank 8 for mixing and storage. When the speed of the high-pressure compressor 4 is the same as that of the low-pressure compressor 1, the first electric motor 21 simultaneously drives both the low-pressure compressor 1 and the high-pressure compressor 4. When the pressure in the gas storage tank 6 reaches the upper limit, the control center 30 sends a signal to shut down the control system and complete the energy storage process.

[0053] In this embodiment, the ambient air temperature is 25℃ and the pressure is 101.3 kPa. The working pressure of the buffer tank is 360 kPa to 400 kPa, the initial pressure of the gas storage tank is 120 kPa to 150 kPa, and the upper limit of the gas storage tank pressure is 900 kPa to 950 kPa. In this embodiment, the working pressure of the buffer tank is maintained within a range that ensures the outlet temperatures of the low-pressure compressor and the high-pressure compressor are the same. The gas pressure inside the gas storage tank in this embodiment is obtained by comprehensively considering the limitations of the overall system design and existing tank technology and compressor design technology.

[0054] More specifically, in this embodiment, in the initial state, the valves on the connecting pipelines between the first outlet of the intercooler and the air storage tank and the buffer tank, as well as the valves on the first heat absorption pipeline and the second heat absorption pipeline, are all in the closed state; the first 3S clutch and the second 3S clutch are in the disengaged state, and the buffer tank 3 and the air storage tank 6 contain air at different pressures. In this embodiment, the buffer tank 3 and the air storage tank 6 store air at different pressures in advance to ensure that the outlet pressure of the low-pressure compressor and the high-pressure compressor are higher than their respective inlet pressures, ensuring that the low-pressure compressor and the high-pressure compressor can work normally.

[0055] When the energy storage process begins, the control center 30 sends a signal to open the first control valve 11 and the third control valve 13, thus initiating the first energy storage stage. At room temperature and pressure, air enters the low-pressure compressor 1. The first electric motor 21 drives the low-pressure compressor 1 to compress the air. The compressed air pressure remains the same as that in the air storage tank 6, ensuring that the inlet pressure of the high-pressure compressor 4 remains constant and that the low-pressure compressor operates under stable conditions, guaranteeing the stability of the system. The compressed air then enters the intercooler 2 to release heat and cool down, transferring the heat to the low-temperature heat storage medium from the low-temperature tank 7, before entering the air storage tank 6 for storage. The heat storage medium, heated by the heat absorption in the intercooler 2, enters the high-temperature tank 8 for storage, thus completing the first energy storage stage.

[0056] The control center 30 monitors the system's operating status by receiving pressure signals from the pressure sensor 32. As the first energy storage phase progresses, the pressure in the gas storage tank 6 continuously increases. When the pressure in the gas storage tank 6 equals that in the buffer tank 3, the control center 30 sends a signal to open the second control valve 12 and the fourth control valve 14, close the first control valve 11, and engage the second 3S clutch 16, thus entering the second energy storage phase. During this phase, to ensure the high-pressure compressor 4 operates efficiently and stably, a key task for the control center 30 is to precisely maintain pressure stability within the buffer tank 3.

[0057] In another preferred embodiment, the working pressure of the buffer tank is maintained within a range that ensures the outlet temperatures of the low-pressure compressor and the high-pressure compressor are the same. To achieve this, the control center in this embodiment is also used to receive the outlet temperature detection values ​​of the low-pressure compressor and the high-pressure compressor, and calculate the working pressure of the buffer tank based on the temperature detection values. This can be achieved, for example, through a closed-loop feedback control system: the control system uses the outlet temperature difference of the two-stage compressor as an input signal, and according to the adjustment rule that the set value is reduced when the low-pressure outlet temperature is high and increased when the high-pressure outlet temperature is high, it outputs an adjustment command for the working pressure of the buffer tank. More specifically, in this embodiment, the working pressure of the buffer tank is 360 kPa to 400 kPa.

[0058] In a preferred embodiment, to accurately maintain the pressure within the buffer tank 3 and keep it within the working pressure, this embodiment employs a closed-loop feedback control system based on a pressure sensor. More specifically, the control center 30 monitors the pressure within the buffer tank 3 in real time. When the pressure fluctuates due to the consumption of the high-pressure compressor 4, the control center 30 adjusts the speed of the first motor 21 driving the low-pressure compressor 1 in real time and precisely via a frequency converter / speed changer. If the buffer tank pressure tends to decrease relative to the buffer tank pressure setpoint, the speed of the first motor 21 is increased to increase the output flow of the low-pressure compressor 1, compensating for the buffer tank pressure. If the buffer tank pressure tends to increase relative to the buffer tank pressure setpoint, the speed of the first motor 21 is decreased to reduce the flow entering the buffer tank. Through this active and dynamic speed adjustment, the inlet of the high-pressure compressor 4 is always kept stable near the preset optimal working pressure point, thereby greatly improving the overall operating efficiency and reliability of the compression system under varying operating conditions.

[0059] The buffered medium-pressure air then enters the high-pressure compressor 4 driven by the second electric motor 22 for further compression. After compression, the medium-pressure air enters the aftercooler 5 to release heat and cool down, and then enters the storage tank 6 for storage. The low-temperature heat storage medium from the low-temperature tank 7 absorbs heat and heats up in the intercooler 2 and aftercooler 5 respectively, and then enters the high-temperature tank 8 for mixing and storage, thus completing the second energy storage stage.

[0060] The control center 30 monitors the system's operating status by receiving speed signals from the speed sensor 31. As the second energy storage phase progresses, the speeds of the high-pressure compressor 4 and the second electric motor 22 rapidly increase. When the speed of the high-pressure compressor 4 matches that of the low-pressure compressor 1, the control center 30 sends a signal to close the first 3S clutch 15 and disengage the second 3S clutch 16, thus initiating the third energy storage phase. At this time, the first electric motor 21 simultaneously drives both the low-pressure compressor 1 and the high-pressure compressor 4.

[0061] When the pressure in the gas storage tank 6 reaches the upper limit, the control center 30 sends a signal to stop the control system, close all control valves, disengage all clutches, and the energy storage process ends.

[0062] Dimensionless power is used to characterize the operational stage of an energy storage process, defined as the ratio of the current output power to the rated output power, such as... Figure 7 As shown, points 1-2-3-4-8 represent the time-varying power output of the low-pressure compressor alone, and points 6-7-8 represent the time-varying power output of the high-pressure compressor alone. The power curves of the low-pressure compressor (1-2-3-4-8) and the high-pressure compressor (3-5-8) together constitute the time-varying power output. Because the low-pressure compressor power curve (1-2-3-4-8) coincides with the total power curve, it is not shown separately in the figure.

[0063] As can be seen, with the initiation of the energy storage phase, the low-pressure compressor starts up quickly and reaches a stable operating state within a short period, its output power rapidly increasing from zero to a stable value, corresponding to process 1-2-3 in the diagram. Once the gas tank pressure reaches the set value, the high-pressure compressor starts operating, working in conjunction with the low-pressure compressor; its output power change corresponds to process 3-5. At this time, the low-pressure compressor maintains stable operation, corresponding to process 3-4. Subsequently, both compressors continue to operate in steady state until the gas storage pressure reaches its upper limit, at which point the energy storage phase ends and the compressors shut down, corresponding to processes 5-8 and 4-8. Throughout the system's operation, its mass flow rate remains constant, making the heat exchange and energy storage processes between the downstream heat exchanger and the gas tank more efficient and balanced, resulting in a more stable system.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A distributed compressed air segmented compressed energy storage device, characterized by, The application relates to a heat storage system, which comprises an air compression unit, a heat storage unit and a control center. The air compression unit comprises a low-pressure compressor, an intercooler, a buffer tank, a high-pressure compressor, a post-cooler and a gas storage tank which are connected in sequence. The outlet of the low-pressure compressor is connected with the first inlet of the intercooler, the first outlet of the intercooler is connected with the gas storage tank and the buffer tank through two connecting pipelines respectively, and valves are arranged on the two connecting pipelines respectively; the first outlet of the post-cooler is connected with the gas storage tank; the low-pressure compressor is connected with a first motor; the high-pressure compressor is connected with a second motor; pressure sensors are arranged in the buffer tank and the gas storage tank; the air is compressed by the low-pressure compressor, is cooled by the intercooler, and then is stored in the gas storage tank or the buffer tank; the air in the buffer tank is compressed by the high-pressure compressor in sequence, is cooled by the post-cooler, and then is stored in the gas storage tank. The heat storage unit comprises a low-temperature tank for storing a low-temperature heat storage medium and a high-temperature tank for storing a high-temperature medium; the low-temperature tank is connected with the second inlet of the intercooler through a first heat absorption pipeline; the second outlet of the intercooler is connected with the high-temperature tank; the low-temperature tank is also connected with the second inlet of the post-cooler through a second heat absorption pipeline; the second outlet of the post-cooler is connected with the high-temperature tank; valves are arranged on the first heat absorption pipeline and the second heat absorption pipeline respectively. The control center is connected with the pressure sensors and the valves, receives the pressure values detected by the pressure sensors, and controls the opening and closing of the valves according to the pressure values; the control center also controls the rotating speed of the first motor according to the pressure value detected by the pressure sensor in the buffer tank. The low-pressure compressor and the high-pressure compressor each comprise an impeller, a blade diffuser and a volute; the impeller is arranged at the central position of the compressor device and is composed of a wheel disc and a plurality of three-dimensional twisted blades; the hub of the impeller is thickened, and the thickness distribution adopts a Spine curve to realize smooth transition from the inlet area to the outlet area of the impeller; The blade inlet flow angle of the blade diffuser matches the outlet flow angle of the impeller to make the flow lines from the outlet of the impeller to the blade inlet of the blade diffuser transition uniformly, and the blade thickness of the blade diffuser adopts a Bezier curve along the chord direction; The flow channel sectional area of the volute gradually increases along the circumferential direction, the inner wall profile of the volute adopts a plurality of involute arcs, and an asymmetric flow channel section is selected.

2. The distributed compressed air segmented compressed energy storage device of claim 1, wherein, The first motor, the low-pressure compressor, the high-pressure compressor and the second motor are coaxially connected; a first 3S clutch is arranged on the shaft between the low-pressure compressor and the high-pressure compressor; a second 3S clutch is arranged on the shaft between the high-pressure compressor and the second motor; a rotating speed sensor is arranged on the second motor; the first 3S clutch, the second 3S clutch and the rotating speed sensor are connected with the control center; the control center receives the rotating speed signal of the rotating speed sensor and controls the closing and opening of the first 3S clutch and the second 3S clutch according to the rotating speed signal.

3. The distributed compressed air segmented compressed energy storage device of claim 1, wherein, The round corner radius of the volute tongue is 10mm-20mm.

4. The method of segmented compressed air energy storage of a distributed compressed air energy storage system according to any one of claims 1-3, wherein, The application further relates to a method for controlling the heat storage system. The air at normal temperature and pressure is first compressed at low pressure to raise its pressure to the same pressure as that of the gas storage tank; then, the compressed air is subjected to first heat exchange with the heat storage medium: the air is cooled by heat release and then stored in the gas storage tank, and the heat storage medium is heated and then stored, thus completing the first energy storage stage; When the pressure of the gas storage tank rises to the same pressure as that of the buffer tank, the second energy storage stage starts; at this time, the compressed air is cooled by heat release and then enters the buffer tank for buffering, and this process needs to maintain the stable pressure in the buffer tank, and the air buffered in the buffer tank is compressed at high pressure; the air compressed again is subjected to second heat exchange with the heat storage medium which has completed the first heat exchange, and is stored in the gas storage tank after further heat release; the heat storage medium is heated to a higher temperature after two heat absorption and is stored, thus completing the second energy storage stage; When the rotation speeds of the low-pressure compressor and the high-pressure compressor are consistent, they are driven by the same motor, and the system enters the third energy storage stage; the energy storage process continues until the pressure in the gas storage tank reaches the set upper limit, at which time the entire energy storage process ends.

5. The method of claim 4, wherein, Before the first energy storage stage starts, the valves on the connecting pipelines of the first outlet of the intercooler with the gas storage tank and the buffer tank and the valves on the first heat absorption pipeline and the second heat absorption pipeline are closed, and the buffer tank and the gas storage tank store air at different pressures.

6. The method of claim 4, wherein the method further comprises: When the energy storage process starts to work, the control center controls the valves on the connecting pipelines of the first outlet of the intercooler with the gas storage tank and the first heat absorption pipeline between the low-temperature tank and the intercooler to open, and the first energy storage stage starts, and the air at normal temperature and pressure enters the low-pressure compressor, and the first motor drives the low-pressure compressor to compress the air at normal temperature and pressure.

7. The method of claim 4, wherein the method further comprises: Before the second energy storage stage, the pressure sensor is used to monitor the pressures in the gas storage tank and the buffer tank, and when the pressure of the gas storage tank is the same as that of the buffer tank, the control center controls the valves on the connecting pipelines of the intercooler with the buffer tank and the valves on the connecting pipelines of the first inlet of the aftercooler with the low-temperature tank to open, and the valve on the connecting pipeline between the first outlet of the intercooler and the gas storage tank is closed.

8. The method of claim 4, wherein the method further comprises: In the second energy storage stage, the rotation speed of the first motor is regulated according to the pressure of the buffer tank, and when the pressure sensor detects that the pressure of the buffer tank is lower than the set value, the rotation speed of the first motor is increased; if the pressure of the buffer tank is higher than the set value, the rotation speed of the first motor is decreased.

9. The method of claim 1, wherein, The working pressure of the buffer tank is 360kPa~400kPa, the initial pressure of the gas storage tank is 120kPa~150kPa, and the upper limit of the pressure of the gas storage tank is 900kPa~950kPa.

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