Gas-liquid two-phase coordinated regulation carbon dioxide energy storage system and control method thereof

Abstract

The invention discloses a gas-liquid two-phase coordinated regulation carbon dioxide energy storage system and a control method thereof. The carbon dioxide energy storage system comprises a gas storage unit, an energy storage assembly, a liquid storage unit and an energy release assembly which are sequentially connected in a closed loop mode, a gas-liquid two-phase mixed carbon dioxide working medium is stored in the liquid storage unit, a gas phase outlet and a liquid phase outlet are formed in the liquid storage unit, and the gas phase outlet is connected to an inlet of the energy release assembly through a first connecting pipeline; the liquid phase outlet is connected to an inlet of the energy release assembly through a second connecting pipeline, and an evaporator is arranged on the second connecting pipeline. Wherein the liquid storage unit conveys the carbon dioxide gas stored in the liquid storage unit to the energy release assembly at the starting operation stage of the energy release assembly; in the stable operation stage of the energy release assembly, the liquid storage unit conveys the liquid carbon dioxide gas stored in the liquid storage unit to the energy release assembly after being evaporated and gasified through the evaporator. According to the scheme, the starting duration of the turbine of the energy release assembly can be shortened, and the response speed of the energy storage system is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and in particular, to a carbon dioxide energy storage system with gas-liquid two-phase collaborative regulation and its control method. Background Art

[0002] Currently, the energy storage technology based on the carbon dioxide gas-liquid phase change cycle uses surplus power during the low electricity consumption period or clean energy to compress and condense gaseous carbon dioxide at normal temperature and pressure in the gas storage unit into liquid carbon dioxide, which is stored in the liquid storage unit, and stores the heat energy generated during the compression process. During the peak electricity consumption period, the stored heat energy is used to heat the liquid carbon dioxide to gas state, and the gaseous carbon dioxide drives the turbine to drive the generator for power generation. After doing work, the gaseous carbon dioxide returns to the gas storage unit for recycling. It has gradually attracted wide attention due to its advantages such as simple structure, flexible layout, and relatively high energy storage efficiency. In the existing carbon dioxide energy storage system based on the carbon dioxide gas-liquid phase change cycle, when the turbine of the energy release component starts, it is necessary to first evaporate and gasify the liquid carbon dioxide in the liquid storage unit and then superheat it to drive the turbine to start. The heating process of the liquid carbon dioxide is relatively slow, resulting in a long start-up time of the turbine and being unable to quickly respond to changes in power demand. Summary of the Invention

[0003] Aiming at the problems existing in the prior art, the present invention provides a carbon dioxide energy storage system with gas-liquid two-phase collaborative regulation and its control method to solve the problem of how to shorten the start-up duration of the turbine of the energy release component and thus improve the response speed.

[0004] To achieve the above object, the present invention adopts the following technical solutions: The first aspect of the present invention is to provide a carbon dioxide energy storage system with gas-liquid two-phase collaborative regulation, including a gas storage unit, an energy storage component, a liquid storage unit, and an energy release component that are connected in a closed loop in sequence. The liquid storage unit stores a carbon dioxide working medium in a gas-liquid two-phase mixture and is provided with a gas phase outlet and a liquid phase outlet. The gas phase outlet is connected to the inlet of the energy release component through a first connection pipeline, and the liquid phase outlet is connected to the inlet of the energy release component through a second connection pipeline. An evaporator is provided on the second connection pipeline. Wherein, at least within a third time period after the energy release component starts to operate, the liquid storage unit transports the carbon dioxide gas stored therein to the energy release component through the first connection pipeline; during the stable operation stage of the energy release component after the third time period, the liquid storage unit transports the liquid carbon dioxide stored therein to the energy release component through the second connection pipeline after evaporating and gasifying it through the evaporator.

[0005] In a specific solution, a first valve is provided on the first connection pipeline, and a second valve is provided on the second connection pipeline.

[0006] In a specific solution, the carbon dioxide energy storage system further includes a gas storage unit connected between the energy storage component and the energy release component. The gas storage unit is configured to: within a first time period after the energy storage component starts to operate and within a second time period before the energy storage component stops operating, the gas storage unit receives and stores the high-temperature carbon dioxide gas output from the energy storage component; before the energy release component starts to operate, the gas storage unit inputs the stored high-temperature carbon dioxide gas into the energy release component to displace the low-temperature carbon dioxide gas in the energy release pipeline of the energy release component with high-temperature carbon dioxide gas.

[0007] In a specific solution, the gas storage unit includes a gas storage container, a third connection pipeline, and a fourth connection pipeline. The inlet of the gas storage container is connected to the energy storage component through the third connection pipeline, and the outlet of the gas storage container is connected to the energy release component through the fourth connection pipeline. A third valve is provided on the third connection pipeline, and a fourth valve is provided on the fourth connection pipeline.

[0008] In a specific solution, the energy storage component includes a compressor and an energy storage heat exchanger. The energy storage heat exchanger is connected to the outlet of the compressor through an energy storage pipeline, and the inlet of the gas storage container is connected to the energy storage pipeline through the third connection pipeline; the energy release component includes a turbine and an energy release heat exchanger. The outlet of the energy release heat exchanger is connected to the inlet of the turbine through an energy release pipeline, and the outlet of the gas storage container is connected to the energy release pipeline through the fourth connection pipeline. The first connection pipeline and the second connection pipeline are respectively connected to the inlet of the energy release heat exchanger.

[0009] In a specific solution, the energy release pipeline includes a first inlet, a second inlet, a first outlet, and a second outlet. The outlet of the energy release heat exchanger is connected to the first inlet of the energy release pipeline through a fifth valve, the inlet of the turbine is connected to the first outlet of the energy release pipeline through a sixth valve, and the fourth connection pipeline is connected to the second inlet of the energy release pipeline; a condenser is provided on the connection pipeline between the energy storage component and the liquid storage unit. The second outlet of the energy release pipeline is connected to the condenser through a fifth connection pipeline, and a seventh valve is provided on the fifth connection pipeline; the low-temperature carbon dioxide gas displaced from the energy release pipeline is output to the liquid storage unit after being condensed and liquefied by the condenser.

[0010] The second aspect of the present invention is to provide a control method for the carbon dioxide energy storage system as described above. The control method includes: S101. During the third time period after the energy release component starts running, control the liquid storage unit to transport the carbon dioxide gas stored therein to the energy release component through the first connection pipeline to rotate and accelerate the turbine in the energy release component; and, during the third time period, connect the evaporator to an external heat source so that the evaporator has the condition for evaporating and gasifying liquid carbon dioxide. S102. During the stable operation stage of the energy release component after the third time period, control the liquid storage unit to transport the liquid carbon dioxide gas stored therein to the energy release component through the second connection pipeline for energy release work after evaporation and gasification via the evaporator.

[0011] In a preferred solution, the control method as described above further includes: S103. During the fourth time period before the energy release component stops running, control the liquid storage unit to transport the carbon dioxide gas stored therein to the energy release component through the first connection pipeline for energy release work to reduce the pressure of the liquid storage unit.

[0012] The third aspect of the present invention is to provide another control method for the carbon dioxide energy storage system as described above, and the control method includes: S201. During the first time period after the energy storage component starts running, control the gas temporary storage unit to receive and store the high-temperature carbon dioxide gas output from the energy storage component. S202. During the stable operation stage of the energy storage component after the first time period, control the gas temporary storage unit to stop receiving the high-temperature carbon dioxide gas output from the energy storage component so that the high-temperature carbon dioxide gas is transported towards the liquid storage unit. S203. During the second time period before the energy storage component stops running, control the gas temporary storage unit to receive and store the high-temperature carbon dioxide gas output from the energy storage component until the energy storage component stops running. S204. Before the energy release component starts running, control the gas temporary storage unit to input the stored high-temperature carbon dioxide gas into the energy release component to replace the low-temperature carbon dioxide gas in the energy release pipeline in the energy release component with high-temperature carbon dioxide gas. S205. During the third time period after the energy release component starts running, control the liquid storage unit to transport the carbon dioxide gas stored therein to the energy release component through the first connection pipeline to rotate and accelerate the turbine in the energy release component; and, during the third time period, connect the evaporator to an external heat source so that the evaporator has the condition for evaporating and gasifying liquid carbon dioxide. S206. During the stable operation stage of the energy release component after the third time period, control the liquid storage unit to evaporate and gasify the liquid carbon dioxide gas stored therein through the second connection pipeline via the evaporator and then transport it to the energy release component for energy release and work.

[0013] In a preferred solution, the control method as described above further includes: S207. During the fourth time period before the energy release component stops operating, control the liquid storage unit to transport the carbon dioxide gas stored therein to the energy release component through the first connection pipeline for energy release and work, and reduce the pressure of the liquid storage unit.

[0014] The carbon dioxide energy storage system and its control method with gas-liquid two-phase collaborative regulation provided by the embodiments of the present invention. The liquid storage unit of the energy storage system stores a gas-liquid two-phase mixed carbon dioxide working medium and is provided with a gas phase outlet and a liquid phase outlet. The gas phase outlet is connected to the inlet of the energy release component through a first connection pipeline, and the liquid phase outlet is connected to the inlet of the energy release component through a second connection pipeline, and an evaporator is provided on the second connection pipeline. When the energy release component starts to operate, the liquid storage unit transports the carbon dioxide gas stored therein to the energy release component. The carbon dioxide gas is heated and then used to impulse the turbine to start and accelerate. There is no need to wait for the carbon dioxide gas formed by the evaporation and gasification of liquid carbon dioxide. Therefore, the start-up duration of the turbine can be shortened. Moreover, during the process of using the carbon dioxide gas of the liquid storage unit to impulse and accelerate the turbine, an external heat source is connected to the evaporator to increase the temperature, so that the evaporator has the condition to evaporate and gasify liquid carbon dioxide to generate a large amount of carbon dioxide gas. After the turbine is impulsed and accelerated to the rated speed, the liquid storage unit switches to transport the liquid carbon dioxide stored therein to the energy release component after evaporation and gasification through the evaporator to ensure the stable operation of the turbine for energy release. Thus, the carbon dioxide energy storage system of the present application can shorten the start-up duration of the turbine of the energy release component and improve the response speed of the energy storage system to the upper-level control center (such as the upper-level power grid dispatching center). Description of the Drawings

[0015] Figure 1 is a schematic structural diagram of the carbon dioxide energy storage system in Embodiment 1 of the present invention; Figure 2 is a schematic structural diagram of the carbon dioxide energy storage system in Embodiment 2 of the present invention. Detailed Embodiments

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will describe the detailed embodiments of the present invention in conjunction with the drawings. Examples of these preferred embodiments are illustrated in the drawings. The embodiments of the present invention shown in the drawings and described according to the drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0017] It should be noted that the same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", etc. indicating the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and cannot be understood as a limitation of this patent. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0018] Here, it should also be noted that in order to avoid obscuring the present invention due to unnecessary details, only the structures and / or processing steps closely related to the solution of the present invention are shown in the drawings, and other details less related to the present invention are omitted.

[0019] Embodiment 1 This embodiment first provides a carbon dioxide energy storage system, as Figure 1 shown, the carbon dioxide energy storage system mainly includes a gas storage unit 10, an energy storage component 20, a liquid storage unit 30, and an energy release component 40 that are connected in a closed loop in sequence. Among them, the gas storage unit 10 is used to store gaseous carbon dioxide at normal pressure, and the liquid storage unit 30 is used to store liquid carbon dioxide. The gaseous carbon dioxide flowing out of the gas storage unit 10 is converted into liquid carbon dioxide at a preset energy storage pressure through the energy storage component 20 and flows into the liquid storage unit 30, and the energy storage is completed in this process. The liquid carbon dioxide output from the liquid storage unit 30 releases energy through the energy release component 40 and is converted into gaseous carbon dioxide at normal pressure and flows into the gas storage unit 10, and the energy release and application are completed in this process. Generally, the energy storage component 20 compresses and liquefies gaseous carbon dioxide into liquid carbon dioxide and stores it in the liquid storage unit 30 during the low electricity consumption period or by using abandoned wind and solar power, and stores the energy as compression energy and heat energy; during the high electricity consumption period, the energy release component 40 vaporizes and expands the liquid carbon dioxide to do work, releases the stored energy and converts it into electric energy for use.

[0020] Among them, the specific component structures of the gas storage unit 10, the energy storage component 20, the liquid storage unit 30, and the energy release component 40 can be implemented with reference to the existing technologies. The gas storage unit 10 is also called a gas storage bin, a gas storage reservoir, a gas storage component, etc. in the existing technologies, and the liquid storage unit 30 is also called a liquid storage tank, a liquid storage container, an energy storage container, etc. in the existing technologies. For example, the technical solutions disclosed in the existing patent documents CN119289275A, CN116221616A, CN117628836A, and CN116857027A.

[0021] As a specific example, in this embodiment, as Figure 1 shown, the energy storage assembly 20 mainly includes a compressor 21 and an energy storage heat exchanger 22 connected between the gas storage unit 10 and the liquid storage unit 30. The energy storage heat exchanger 22 is connected to the outlet of the compressor 21 through an energy storage pipeline 23. Further, a condenser 51 is provided on the pipeline connecting the energy storage assembly 20 and the liquid storage unit 30. The gaseous carbon dioxide in the gas storage unit 10 is compressed by the compressor 21, cooled by heat exchange through the energy storage heat exchanger 22, and then liquefied by the condenser 51 to form liquid carbon dioxide, which is stored in the liquid storage unit 30.

[0022] In the carbon dioxide energy storage system, since the condenser 51 cannot completely liquefy the carbon dioxide gas, the high-pressure carbon dioxide gas cooled by heat exchange through the energy storage heat exchanger 22 forms a carbon dioxide working medium in a gas-liquid two-phase mixture after being liquefied by the condenser 51. Therefore, in the embodiment of the present application, the liquid storage unit 30 stores a carbon dioxide working medium in a gas-liquid two-phase mixture. Generally, the liquid carbon dioxide working medium is located at the bottom of the liquid storage unit 30, and the high-pressure gaseous carbon dioxide working medium is located at the top of the liquid storage unit 30.

[0023] As a specific example, in this embodiment, as Figure 1 shown, the energy release assembly 40 mainly includes an energy release heat exchanger 42 and a turbine 41 connected between the liquid storage unit 30 and the gas storage unit 10. The energy release heat exchanger 42 is connected to the inlet of the turbine 41 through an energy release pipeline 43. Further, a liquid pump 52 and an evaporator 53 are sequentially provided on the pipeline connecting the liquid storage unit 30 and the energy release assembly 40. The liquid carbon dioxide in the liquid storage unit 30 is pressurized by the liquid pump 52 and then input into the evaporator 53. After being heated and evaporated by the evaporator 53, it is input into the energy release heat exchanger 42 for further heating to increase the temperature, and then input into the turbine 41 to do work externally (for example, generate electricity) to release energy, and is converted into gaseous carbon dioxide at normal pressure and stored in the gas storage unit 10.

[0024] In the prior art, during the energy release stage, the startup operation process of the energy release assembly 40 includes the following steps: (1). Connect an external heat source to heat the evaporator 53 so that the evaporator 53 has the condition to heat and evaporate the liquid carbon dioxide.

[0025] (2). After the evaporator 53 has the condition to heat and evaporate the liquid carbon dioxide, start the liquid pump 52 to pressurize the liquid carbon dioxide in the liquid storage unit 30 and input it into the evaporator 53 for evaporation and gasification.

[0026] (3) The evaporated and vaporized carbon dioxide gas is input into the energy-releasing heat exchanger 42 for further heating and temperature rise, and then input into the turbine 41, and the turbine 41 starts to operate.

[0027] (4) Gradually increase the power of the liquid pump 52 so that the evaporator 53 outputs a large amount of carbon dioxide gas to impulse and increase the speed of the turbine 41 until the turbine 41 reaches the rated speed and enters the stable operation stage.

[0028] During the startup operation process as described above, since the heating and evaporation process of liquid carbon dioxide is relatively slow, the startup time of the turbine 41 is relatively long and it cannot quickly respond to changes in power demand.

[0029] To solve the above problems, in the carbon dioxide energy storage system provided in this embodiment, refer to Figure 1 , a gas phase outlet 31 and a liquid phase outlet 32 are provided in the liquid storage unit 30. The gas phase outlet 31 is connected to the inlet of the energy-releasing component 40 through a first connection pipe 33, and the liquid phase outlet 32 is connected to the inlet of the energy-releasing component 40 through a second connection pipe 34. The liquid pump 52 and the evaporator 53 are connected to the second connection pipe 34.

[0030] Among them, within the third time period after the energy-releasing component 40 starts to operate, the liquid storage unit 30 transports the stored carbon dioxide gas therein to the energy-releasing component 40 through the first connection pipe 33. During the stable operation stage of the energy-releasing component 40 after the third time period, the liquid storage unit 30 transports the stored liquid carbon dioxide therein to the energy-releasing component 40 through the second connection pipe 34 after evaporation and gasification by the evaporator 53.

[0031] Specifically, as described above, the carbon dioxide working medium stored in the liquid storage unit 30 is a gas-liquid two-phase mixture, and the liquid carbon dioxide working medium is located at the bottom of the liquid storage unit 30, while the high-pressure gaseous carbon dioxide working medium is located at the top of the liquid storage unit 30. Therefore, in this embodiment, the gas phase outlet 31 is located at the top of the liquid storage unit 30, and the liquid phase outlet 32 is located at the bottom of the liquid storage unit 30. The first connection pipe 33 is connected between the gas phase outlet 31 and the inlet of the energy-releasing heat exchanger 42, and the second connection pipe 34 is connected between the liquid phase outlet 32 and the inlet of the energy-releasing heat exchanger 42.

[0032] Further, a first valve 71 is provided on the first connecting pipe 33, and a second valve 72 is provided on the second connecting pipe 34. By controlling the opening and closing states of the first valve 71 and the second valve 72, the working medium is selectively supplied to the energy release assembly 40 through the first connecting pipe 33 or the second connecting pipe 34.

[0033] Specifically, within a third time period after the energy release assembly 40 starts to operate, the first valve 71 is opened and the second valve 72 is closed, and the carbon dioxide gas in the liquid storage unit 30 is input into the energy release heat exchanger 42 through the first connecting pipe 33. During the stable operation stage of the energy release assembly 40 after the third time period, the first valve 71 is closed and the second valve 72 is opened, and the liquid carbon dioxide in the liquid storage unit 30 is evaporated and gasified through the evaporator 53 and then input into the energy release heat exchanger 42 through the second connecting pipe 34.

[0034] Based on the carbon dioxide energy storage system provided in this embodiment, when the energy release assembly 40 starts to operate, the carbon dioxide gas stored in the liquid storage unit 30 is transported to the energy release assembly 40. The carbon dioxide gas is heated and then rushes to rotate the turbine 41 to start accelerating, without waiting for the carbon dioxide gas formed by the evaporation and gasification of liquid carbon dioxide. Therefore, the start-up duration of the turbine 41 can be shortened.

[0035] The control method of the carbon dioxide energy storage system as described in the above embodiment includes the following steps: Step S101: Within a third time period after the energy release assembly 40 starts to operate, control the liquid storage unit 30 to transport the stored carbon dioxide gas to the energy release assembly 40 through the first connecting pipe 33 to rush and accelerate the turbine 41 in the energy release assembly 40. And within the third time period, the evaporator 53 is connected to an external heat source so that the evaporator 53 has the condition for evaporating and gasifying liquid carbon dioxide.

[0036] Specifically, when the energy release assembly 40 starts to operate, the first valve 71 is opened and the second valve 72 is closed, and the carbon dioxide gas in the liquid storage unit 30 is input into the energy release heat exchanger 42 through the first connecting pipe 33. The carbon dioxide gas is heated and then rushes to rotate the turbine 41 to start accelerating. And during the process of the turbine 41 starting to accelerate, an external heat source is connected to heat the evaporator 53 so that the evaporator 53 has the condition for heating and evaporating liquid carbon dioxide; after the evaporator 53 has the condition for heating and evaporating liquid carbon dioxide, the liquid pump 52 is started to pressurize the liquid carbon dioxide in the liquid storage unit 30 and then input it into the evaporator 53 for evaporation and gasification. At this time, the second valve 72 remains closed.

[0037] Among them, the third time period can be understood as the duration from the start of the turbine 41 to the speed increase to the rated speed.

[0038] Step S102, in the stable operation stage of the energy release component 40 after the third time period, control the liquid storage unit 30 to evaporate and gasify the liquid carbon dioxide gas stored therein through the second connection pipe 34 via the evaporator 53 and then transport it to the energy release component 40 for energy release and work.

[0039] Specifically, after the turbine 41 is impulsively rotated and the speed is increased to the rated speed and enters the stable operation stage, open the second valve 72 and close the first valve 71. The liquid storage unit 30 evaporates and gasifies the liquid carbon dioxide therein through the second connection pipe 34 via the evaporator 53 and then inputs it to the energy release heat exchanger 42. After being further heated and raised in temperature by the energy release heat exchanger 42, it is input to the turbine 41 to release energy and do work externally.

[0040] Compared with steps (1)-(4) in the start-up and operation process of the energy release component 40 in the prior art described above, for the control method of the carbon dioxide energy storage system provided in this embodiment, step S101 is equivalent to: the start-up and operation of the energy release component 40 directly start from step (3) in the prior art, without waiting for the process of the carbon dioxide gas formed by the evaporation and gasification of the liquid carbon dioxide in steps (1) and (2). Therefore, the start-up duration of the energy release component 40 can be shortened, and the response speed of the energy storage system to the upper-level control center (such as the upper-level power grid dispatching center) is improved; and, steps (1) and (2) are carried out simultaneously during the process of step (3), so that the evaporator 53 has the condition to evaporate and gasify the liquid carbon dioxide to generate a large amount of carbon dioxide gas. After the turbine 41 is impulsively rotated and the speed is increased to the rated speed, the liquid storage unit 30 switches to transport the liquid carbon dioxide stored therein to the energy release component 40 after evaporation and gasification through the evaporator 53, ensuring the stable operation of the turbine 41 for energy release.

[0041] As a preferred solution, in this embodiment, the control method of the carbon dioxide energy storage system further includes the following steps: Step S103, in the fourth time period before the energy release component 40 stops operating, control the liquid storage unit 30 to transport the carbon dioxide gas stored therein to the energy release component 40 through the first connection pipe 33 for energy release and work, and reduce the pressure of the liquid storage unit 30.

[0042] Specifically, when the liquid level of the liquid storage unit 30 reaches the lowest control value and then the energy release component 40 plans to shut down, the shutdown process in the prior art is as follows: gradually reduce the power of the liquid pump 52, gradually reduce the flow rate of the carbon dioxide gas input into the energy release component 40, and the turbine 41 also gradually reduces its rotational speed until it finally stops running completely. At this time, there is still a relatively large amount of high-pressure carbon dioxide gas in the liquid storage unit 30, and the pressure in the liquid storage unit 30 is relatively high. When the energy storage component 20 is in the energy storage condition later, after the compressor 21 in the energy storage component 20 starts, the pressure at the outlet of the compressor 21 needs to reach above the pressure of the liquid storage unit 30 before the high-pressure carbon dioxide gas output by the compressor 21 can be transported towards the liquid storage unit 30 to start liquefaction, which will increase the startup duration of the energy storage component 20.

[0043] In this embodiment, as in step S103 above, when the liquid level of the liquid storage unit 30 reaches the lowest control value and then the energy release component 40 plans to shut down, open the first valve 71 and close the second valve 72, stop the operation of the liquid pump 52, and the liquid storage unit 30 inputs the carbon dioxide gas therein into the energy release heat exchanger 42 through the first connection pipe 33. After being further heated and raised in temperature by the energy release heat exchanger 42, it is input into the turbine 41, and the high-pressure carbon dioxide gas at the top of the liquid storage unit 30 is used to continue to release energy and do work to reduce the pressure of the liquid storage unit 30. Control the gas flow rate according to the pressure of the liquid storage unit 30. After the pressure of the liquid storage unit 30 drops to the set pressure value, gradually reduce the output gas flow rate until the turbine 41 stops running completely, and then close the first valve 71.

[0044] Among them, the fourth time period can be understood as the duration from the time point when the liquid level of the liquid storage unit 30 drops to the lowest control value to the time when the turbine 41 stops running completely.

[0045] Therefore, in the carbon dioxide energy storage system and its control method provided in this embodiment, based on step S103 above: on the one hand, it can reduce the pressure of the liquid storage unit 30, create a low-pressure startup condition for the upcoming energy storage condition, which is beneficial to reducing the startup power consumption of the compressor 21 of the energy storage component 20 and enabling the energy storage condition to be liquefied in advance, so as to realize the rapid and flexible switching between the energy release condition and the energy storage condition; on the other hand, it can also stop the operation of the liquid pump 52 and the evaporator 53 in advance, saving the energy consumption of the carbon dioxide energy storage system.

[0046] Embodiment 2 In the carbon dioxide energy storage system, the compressor 21 in the energy storage component 20 is a core component. During the energy storage process: when the compressor 21 starts to operate, the intake air volume at the inlet of the compressor 21 needs to be gradually increased, and the gas pressure at the outlet of the compressor 21 also gradually increases; when the compressor 21 plans to stop operating, the intake air volume at the inlet of the compressor 21 needs to be gradually decreased, and the gas pressure at the outlet of the compressor 21 also gradually decreases. Since there is a certain pressure both in the liquid storage unit 30 itself and in the conveying pipeline on the energy storage side connected to the inlet of the liquid storage unit 30, when the gas pressure at the outlet of the compressor 21 does not exceed the pressure of the liquid storage unit 30, the carbon dioxide gas output by the compressor 21 cannot be transported to the liquid storage unit 30. Therefore, the compressor 21 is prone to surge phenomena during the start-up stage and the stop stage. In order to prevent the compressor 21 from entering the surge condition, in the prior art, an anti-surge valve is usually connected to the outlet end of the compressor 21, and the high-temperature carbon dioxide gas output by the compressor 21 during the start-up stage and the stop stage is discharged or returned to the inlet end of the compressor 21 through the anti-surge valve. Whether the high-temperature carbon dioxide gas is discharged or returned to the compressor inlet end, it will cause the energy of the carbon dioxide energy storage system not to be effectively utilized, resulting in energy waste and increased operating costs.

[0047] To solve the above problems, in a carbon dioxide energy storage system provided in Embodiment 2, further improvements are made on the basis of the carbon dioxide energy storage system provided in Embodiment 1. Specifically, referring to Figure 2 , the carbon dioxide energy storage system provided in this embodiment further includes a gas storage unit 60. The gas storage unit 60 is connected between the energy storage component 20 and the energy release component 40. The gas storage unit 60 is configured to: within a first time period after the energy storage component 20 starts to operate and within a second time period before the energy storage component 20 stops operating, the gas storage unit 60 receives and stores the high-temperature carbon dioxide gas output from the energy storage component 20, thereby preventing the compressor 21 in the energy storage component 20 from entering the surge condition and improving the operating stability of the energy storage system; before the energy release component 40 starts to operate, the gas storage unit 60 inputs the stored high-temperature carbon dioxide gas into the energy release component 40, replacing the low-temperature carbon dioxide gas in the energy release pipeline 43 of the energy release component 40 with high-temperature carbon dioxide gas. Thus, the high-temperature carbon dioxide gas that originally needed to be discharged or returned to avoid surge is applied to the energy release component 40, which can not only avoid wasting energy and improve the energy utilization rate of the system to reduce operating costs, but also create favorable conditions for the rapid start of the energy release condition by replacing the low-temperature carbon dioxide gas in the energy release pipeline 43 with high-temperature carbon dioxide gas, improving the operating efficiency of the system.

[0048] It should be noted that the specific durations of the first time period and the second time period need to be specifically set according to the actual operating conditions of the energy storage component 20, with the basic requirement of avoiding the compressor 21 from entering the surge condition.

[0049] In a specific implementation, as Figure 2 shown, the gas storage unit 60 mainly includes a gas storage container 61, a third connecting pipe 62, and a fourth connecting pipe 63. The inlet of the gas storage container 61 is connected to the energy storage component 20 through the third connecting pipe 62, specifically to the energy storage pipe 23. The outlet of the gas storage container 61 is connected to the energy release component 40 through the fourth connecting pipe 63, specifically to the energy release pipe 43. A third valve 73 is provided on the third connecting pipe 62, and a fourth valve 74 is provided on the fourth connecting pipe 63. By controlling the opening and closing states of the third valve 73 and the fourth valve 74, the gas storage unit 60 receives high-temperature carbon dioxide gas or outputs high-temperature carbon dioxide gas.

[0050] Specifically, within the first time period after the energy storage component 20 starts operating and within the second time period before the energy storage component 20 stops operating, the third valve 73 is opened and the fourth valve 74 is closed, and the high-temperature carbon dioxide gas output by the compressor 21 is input into the gas storage container 61 for storage; before the energy release component 40 starts operating, the third valve 73 is closed and the fourth valve 74 is opened, and the high-temperature carbon dioxide gas stored in the gas storage container 61 is input into the energy release pipe 43 to displace the low-temperature carbon dioxide gas in the energy release pipe 43 with high-temperature carbon dioxide gas.

[0051] Specifically, as Figure 2 shown, the energy release pipe 43 includes a first inlet 431, a second inlet 432, a first outlet 433, and a second outlet 434. The outlet of the energy release heat exchanger 42 is connected to the first inlet 431 of the energy release pipe 43 through a fifth valve 75, the inlet of the turbine 41 is connected to the first outlet 433 of the energy release pipe 43 through a sixth valve 76, the fourth connecting pipe 63 is connected to the second inlet 432 of the energy release pipe 43, and the second outlet 434 of the energy release pipe 43 is connected to the connecting pipeline between the energy storage component 20 and the liquid storage unit 30 through a fifth connecting pipe 64. A seventh valve 77 is provided on the fifth connecting pipe 64.

[0052] Before the energy release component 40 starts to operate, open the fourth valve 74 and the seventh valve 77, and close the fifth valve 75 and the sixth valve 76. At this time, the high-temperature carbon dioxide gas stored in the gas storage container 61 is input into the energy release pipeline 43 from the second inlet 432, and the low-temperature carbon dioxide gas in the energy release pipeline 43 is output from the second outlet 434 and conveyed towards the liquid storage unit 30 via the fifth connecting pipeline 64. After completely displacing the low-temperature carbon dioxide gas in the energy release pipeline 43, close the fourth valve 74 and the seventh valve 77, open the fifth valve 75 and the sixth valve 76. After the energy release component 40 starts to operate, the high-temperature carbon dioxide gas output by the energy release heat exchanger 42 is input into the energy release pipeline 43 from the first inlet 431 and then output to the turbine 41 via the first outlet 433.

[0053] In this embodiment, the first inlet 431 and the second outlet 434 are disposed adjacent to each other at the first end of the energy release pipeline 43, and the first outlet 433 and the second inlet 432 are disposed adjacent to each other at the second end of the energy release pipeline 43. Further, a gas temperature sensor 80 is connected to the energy release pipeline 43 at a position adjacent to the first outlet 433. The gas temperature sensor 80 is used to detect the temperature of the carbon dioxide gas in the energy release pipeline 43. On the one hand, it can monitor whether the low-temperature carbon dioxide gas in the energy release pipeline 43 can be completely displaced to reach a preset higher temperature, and on the other hand, it can monitor the gas temperature at the inlet end of the turbine 41 during the operation of the energy release component 40.

[0054] As a preferred solution, in this embodiment, the second outlet 434 of the energy release pipeline 43 is connected to the condenser 51 through the fifth connecting pipeline 64. Thus, the low-temperature carbon dioxide gas displaced from the energy release pipeline 43 is output to the liquid storage unit 30 after being condensed and liquefied by the condenser 51.

[0055] This embodiment also provides a control method for the carbon dioxide energy storage system as described above, including the following steps: Step S201, within the first time period after the energy storage component 20 starts to operate, control the gas temporary storage unit 60 to receive and store the high-temperature carbon dioxide gas output from the energy storage component 20.

[0056] Specifically, within the first time period after the energy storage component 20 starts to operate, open the third valve 73 and close the fourth valve 74, so that the high-temperature carbon dioxide gas output by the compressor 21 is input into the gas storage container 61 for storage.

[0057] Step S202. During the stable operation stage of the energy storage component 20 after the first time period, control the gas storage unit 60 to stop receiving the high-temperature carbon dioxide gas output from the energy storage component 20, so that the high-temperature carbon dioxide gas is transported towards the liquid storage unit 30.

[0058] Specifically, after the first time period, the energy storage component 20 enters a stable operation state, the third valve 73 is closed, and the high-temperature carbon dioxide gas output by the compressor 21 is no longer input into the gas storage container 61. The high-temperature carbon dioxide gas output by the compressor 21 is input into the energy storage heat exchanger 22 for heat exchange and cooling, and then liquefied by the condenser 51 to form a gas-liquid two-phase carbon dioxide working medium stored in the liquid storage unit 30.

[0059] Step S203. During the second time period before the energy storage component 20 stops operating, control the gas storage unit 60 to receive and store the high-temperature carbon dioxide gas output from the energy storage component 20 until the energy storage component 20 stops operating.

[0060] Specifically, during the second time period before the energy storage component 20 stops operating, the third valve 73 is opened again. At this time, the fourth valve 74 remains closed, and the high-temperature carbon dioxide gas output by the compressor 21 is input into the gas storage container 61 for storage until the compressor 21 completely stops operating and then the third valve 73 is closed.

[0061] Step S204. Before the energy release component 40 starts operating, control the gas storage unit 60 to input the stored high-temperature carbon dioxide gas into the energy release component 40 to replace the low-temperature carbon dioxide gas in the energy release pipeline 43 of the energy release component 40 with high-temperature carbon dioxide gas.

[0062] Specifically, before the energy release component 40 starts operating, keep the third valve 73 closed, open the fourth valve 74 and the seventh valve 77, and close the fifth valve 75 and the sixth valve 76. At this time, the high-temperature carbon dioxide gas stored in the gas storage container 61 is input into the energy release pipeline 43, and the low-temperature carbon dioxide gas in the energy release pipeline 43 is output via the fifth connection pipeline 64, thereby replacing the low-temperature carbon dioxide gas in the energy release pipeline 43 with high-temperature carbon dioxide gas.

[0063] Further, during the replacement process, the temperature of the carbon dioxide gas in the energy release pipeline 43 is detected by the gas temperature sensor 80. When the detected temperature reaches the preset temperature, it is determined that the low-temperature carbon dioxide gas in the energy release pipeline 43 has been completely replaced. At this time, the fourth valve 74 and the seventh valve 77 are closed, and the fifth valve 75 and the sixth valve 76 are opened.

[0064] Step S205: During the third time period after the energy release component 40 starts to operate, control the liquid storage unit 30 to transport the stored carbon dioxide gas therein to the energy release component 40 through the first connection pipeline 33 to perform impulse speed increase on the turbine 41 in the energy release component 40. Moreover, during the third time period, the evaporator 53 is connected to an external heat source so that the evaporator 53 has the condition for evaporating and gasifying liquid carbon dioxide. This step S205 is the same as step S101 in Embodiment 1 and will not be elaborated in detail here.

[0065] Step S206: During the stable operation stage of the energy release component 40 after the third time period, control the liquid storage unit 30 to transport the stored liquid carbon dioxide gas therein to the energy release component 40 through the second connection pipeline 34 after evaporation and gasification via the evaporator 53 for energy release and work. This step S206 is the same as step S102 in Embodiment 1 and will not be elaborated in detail here.

[0066] As a preferred solution, in this embodiment, the control method of the carbon dioxide energy storage system further includes the following steps: Step S207: During the fourth time period before the energy release component 40 stops operating, control the liquid storage unit 30 to transport the stored carbon dioxide gas therein to the energy release component 40 through the first connection pipeline 33 for energy release and work to reduce the pressure of the liquid storage unit 30. This step S207 is the same as step S103 in Embodiment 1 and will not be elaborated in detail here.

[0067] Based on the carbon dioxide energy storage system and its control method provided in the above Embodiment 2, compared with the prior art, it has the following beneficial effects: (1) During the first time period after the energy storage component starts to operate and during the second time period before the energy storage component stops operating, the gas temporary storage unit receives and stores the high-temperature carbon dioxide gas output from the energy storage component, thereby avoiding the compressor in the energy storage component from entering the surge condition and improving the operation stability of the energy storage system.

[0068] (2) Before the energy release component starts to operate, the gas storage unit inputs the stored high-temperature carbon dioxide gas into the energy release component, replacing the low-temperature carbon dioxide gas in the energy release pipeline of the energy release component with high-temperature carbon dioxide gas, and applying the high-temperature carbon dioxide gas that originally needed to be vented or recycled to avoid surge to the energy release component. This can not only avoid wasting energy, improve the energy utilization rate of the system, and reduce the operating cost, but also create favorable conditions for the rapid start of the energy release condition by replacing the low-temperature carbon dioxide gas in the energy release pipeline with high-temperature carbon dioxide gas, thereby improving the operating efficiency of the system.

[0069] (3) When the energy release component starts to start and operate, the liquid storage unit transports the stored carbon dioxide gas to the energy release component. The carbon dioxide gas is heated and then impels the turbine to start and accelerate. There is no need to wait for the carbon dioxide gas formed by the evaporation and gasification of liquid carbon dioxide. Therefore, the start-up duration of the turbine can be shortened, and the response speed of the energy storage system to the upper-level control center (such as the upper-level power grid dispatching center) can be improved. Moreover, during the process of using the carbon dioxide gas of the liquid storage unit to impel the turbine to accelerate, an external heat source is connected to the evaporator to increase the temperature, enabling the evaporator to have the condition to evaporate and gasify liquid carbon dioxide to generate a large amount of carbon dioxide gas. After the turbine impels and accelerates to the rated speed, the liquid storage unit switches to transporting the stored liquid carbon dioxide to the energy release component after evaporation and gasification through the evaporator, ensuring the stable operation of the turbine for energy release.

[0070] (4) In the fourth time period before the energy release component stops operating, the liquid storage unit transports the stored carbon dioxide gas to the energy release component to continue energy release power generation. This can not only reduce the pressure of the liquid storage unit, create a low-pressure start condition for the upcoming energy storage condition, be beneficial to reducing the start-up power consumption of the compressor of the energy storage component and liquefying the energy storage condition in advance, so as to realize the rapid and flexible switching between the energy release condition and the energy storage condition, but also can stop the operation of the liquid pump and the evaporator in advance, saving the energy consumption of the carbon dioxide energy storage system.

[0071] The above is only the specific implementation manner of the present application. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present application, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A carbon dioxide energy storage system with coordinated regulation of gas-liquid two-phase, comprising a gas storage unit, an energy storage component, a liquid storage unit and an energy release component connected in a closed loop in sequence, characterized in that, The liquid storage unit stores a gas-liquid two-phase mixture of carbon dioxide working medium and is provided with a gas phase outlet and a liquid phase outlet. The gas phase outlet is connected to the inlet of the energy release component through a first connecting pipe, and the liquid phase outlet is connected to the inlet of the energy release component through a second connecting pipe. An evaporator is arranged on the second connecting pipe. Wherein, at least within a third time period after the energy release component starts to operate, the liquid storage unit transports the stored carbon dioxide gas therein to the energy release component through the first connecting pipe; during the stable operation stage of the energy release component after the third time period, the liquid storage unit transports the stored liquid carbon dioxide therein to the energy release component through the second connecting pipe after evaporation and gasification via the evaporator.

2. The carbon dioxide energy storage system according to claim 1, wherein A first valve is arranged on the first connecting pipe, and a second valve is arranged on the second connecting pipe.

3. The carbon dioxide energy storage system according to claim 1 or 2, characterized in that, The carbon dioxide energy storage system further includes a gas temporary storage unit connected between the energy storage component and the energy release component. The gas temporary storage unit is configured to: within a first time period after the energy storage component starts to operate and within a second time period before the energy storage component stops operating, the gas temporary storage unit receives and stores the high-temperature carbon dioxide gas output from the energy storage component; before the energy release component starts to operate, the gas temporary storage unit inputs the stored high-temperature carbon dioxide gas into the energy release component to replace the low-temperature carbon dioxide gas in the energy release pipe of the energy release component with high-temperature carbon dioxide gas.

4. The carbon dioxide energy storage system according to claim 3, characterized in that, The gas temporary storage unit includes a gas storage container, a third connecting pipe, and a fourth connecting pipe. The inlet of the gas storage container is connected to the energy storage component through the third connecting pipe, the outlet of the gas storage container is connected to the energy release component through the fourth connecting pipe. A third valve is arranged on the third connecting pipe, and a fourth valve is arranged on the fourth connecting pipe.

5. The carbon dioxide energy storage system according to claim 4, wherein The energy storage component includes a compressor and an energy storage heat exchanger. The energy storage heat exchanger is connected to the outlet of the compressor through an energy storage pipe, and the inlet of the gas storage container is connected to the energy storage pipe through the third connecting pipe; the energy release component includes a turbine and an energy release heat exchanger. The outlet of the energy release heat exchanger is connected to the inlet of the turbine through the energy release pipe, the outlet of the gas storage container is connected to the energy release pipe through the fourth connecting pipe, and the first connecting pipe and the second connecting pipe are respectively connected to the inlet of the energy release heat exchanger.

6. The carbon dioxide energy storage system according to claim 5, wherein The energy-releasing pipeline includes a first inlet, a second inlet, a first outlet, and a second outlet. The outlet of the energy-releasing heat exchanger is connected to the first inlet of the energy-releasing pipeline through a fifth valve. The inlet of the turbine is connected to the first outlet of the energy-releasing pipeline through a sixth valve. The fourth connecting pipeline is connected to the second inlet of the energy-releasing pipeline. A condenser is provided on the connecting pipeline between the energy storage component and the liquid storage unit. The second outlet of the energy-releasing pipeline is connected to the condenser through a fifth connecting pipeline, and a seventh valve is provided on the fifth connecting pipeline. The low-temperature carbon dioxide gas displaced from the energy-releasing pipeline is condensed and liquefied by the condenser and then output to the liquid storage unit.

7. A control method for a carbon dioxide energy storage system according to any one of claims 1 or 2, characterized in that, The control method includes: S101. In the third time period after the energy-releasing component starts to operate, control the liquid storage unit to transport the carbon dioxide gas stored therein to the energy-releasing component through the first connecting pipeline to rotate and accelerate the turbine in the energy-releasing component. And, in the third time period, the evaporator is connected to an external heat source so that the evaporator has the condition to evaporate and gasify liquid carbon dioxide. S102. In the stable operation stage of the energy-releasing component after the third time period, control the liquid storage unit to transport the liquid carbon dioxide gas stored therein to the energy-releasing component through the second connecting pipeline after evaporating and gasifying through the evaporator to perform energy-releasing work.

8. The control method of the carbon dioxide energy storage system according to claim 7, characterized in that, The control method further includes: S103. In the fourth time period before the energy-releasing component stops operating, control the liquid storage unit to transport the carbon dioxide gas stored therein to the energy-releasing component through the first connecting pipeline to perform energy-releasing work and reduce the pressure of the liquid storage unit.

9. A control method for a carbon dioxide energy storage system according to any one of claims 3-6, characterized in that, The control method includes: S201. In the first time period after the energy storage component starts to operate, control the gas temporary storage unit to receive and store the high-temperature carbon dioxide gas output from the energy storage component. S202. In the stable operation stage of the energy storage component after the first time period, control the gas temporary storage unit to stop receiving the high-temperature carbon dioxide gas output from the energy storage component so that the high-temperature carbon dioxide gas is transported towards the liquid storage unit. S203. In the second time period before the energy storage component stops operating, control the gas temporary storage unit to receive and store the high-temperature carbon dioxide gas output from the energy storage component until the energy storage component stops operating. S204. Before the energy-releasing component starts to operate, control the gas temporary storage unit to input the stored high-temperature carbon dioxide gas into the energy-releasing component to displace the low-temperature carbon dioxide gas in the energy-releasing pipeline in the energy-releasing component with high-temperature carbon dioxide gas. S205. During the third time period after the energy release component starts to operate, control the liquid storage unit to transport the stored carbon dioxide gas to the energy release component through the first connection pipeline to impulse and increase the speed of the turbine in the energy release component; and, during the third time period, connect the evaporator to an external heat source so that the evaporator has the condition for evaporating and gasifying liquid carbon dioxide. S206. During the stable operation stage of the energy release component after the third time period, control the liquid storage unit to transport the stored liquid carbon dioxide gas to the energy release component through the second connection pipeline after evaporation and gasification via the evaporator for energy release and work.

10. The control method of the carbon dioxide energy storage system according to claim 9, wherein, The control method further includes: S207. During the fourth time period before the energy release component stops operating, control the liquid storage unit to transport the stored carbon dioxide gas to the energy release component through the first connection pipeline for energy release and work to reduce the pressure of the liquid storage unit.

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