Energy storage system

Abstract

The utility model provides an energy storage system which comprises an energy storage pipeline and an energy release pipeline, the energy storage pipeline stores electric energy through the compression process and the phase change process of carbon dioxide, and the energy release pipeline releases the electric energy through the phase change process and the expansion process of the carbon dioxide. Specifically, the energy storage system comprises a first storage cavern and a second storage cavern, in the energy storage stage, gaseous carbon dioxide output by the first storage cavern enters the second storage cavern after compression, phase change and pressurization, and in the energy release stage, liquid carbon dioxide output by the second storage cavern returns to the first storage cavern after phase change and expansion power generation. Meanwhile, the power generation efficiency is also improved; according to the system, the cold energy in the energy storage stage is applied to the energy release stage by arranging the cold storage heat exchanger, arrangement of other cooling components is avoided, full utilization of energy is achieved, the manufacturing cost is saved, and the system is optimized.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to an energy storage system. Background Art

[0002] Compressed gas energy storage technology originates from the Brayton air thermodynamic cycle. The Brayton thermodynamic cycle includes four basic processes: compression, heating, expansion, and cooling. By decoupling the compression process from the expansion process, compressed air is produced and stored using valley electricity or excess electricity, and released during peak electricity or electricity-demand periods as a gas source for the expander to generate electricity, thereby indirectly forming a compressed gas power storage function. Since air is difficult to liquefy, compressed air energy storage usually stores compressed air in a high-pressure gaseous form, which places high demands on the gas storage reservoir, resulting in a larger system size and complex structure, and the efficiency of compressed air energy storage is not very ideal. In addition, in the existing technology, the heat or cold in the energy storage stage is not fully applied to the energy release stage, which not only causes energy waste but also requires additional components. Utility Model Content

[0003] In view of this, the present application provides an energy storage system, which makes the system structure compact and simple, not only saving the setting of components but also improving the power generation efficiency.

[0004] In order to achieve the above objectives, this application provides the following technical solutions:

[0005] An energy storage system, comprising:

[0006] The energy storage pipeline includes a first reservoir, a first compressor, a first cooling device, a condenser, a power device, and a second reservoir connected in series, so as to store electrical energy by utilizing the compression process and phase change process of carbon dioxide;

[0007] an energy release pipeline, comprising the second reservoir, a heating device, an expander, and the first reservoir connected in series, so as to release electrical energy by utilizing the phase change and expansion process of the carbon dioxide;

[0008] a first pipeline connected to the outlet of the condenser and comprising a first throttle valve and a cold storage heat exchanger, wherein the first throttle valve is in communication with the condenser, and the cold storage heat exchanger comprises at least a first heat exchange pipeline and a second heat exchange pipeline, wherein the first heat exchange pipeline is used to connect the first throttle valve and the first reservoir, and the second heat exchange pipeline is used to connect the expander and the first reservoir;

[0009] The carbon dioxide in the first reservoir is in a coexisting state of gas, liquid and solid, and the carbon dioxide in the second reservoir is in a liquid state above the critical pressure;

[0010] The cold storage medium in the cold storage heat exchanger is used to absorb the cold released by the carbon dioxide flowing through the first heat exchange pipeline and transfer the cold to the carbon dioxide flowing through the second heat exchange pipeline.

[0011] Optionally, in the above energy storage system, the heating device includes a heat-releasing heat exchanger and a regenerator, the heat-releasing heat exchanger includes a third heat exchange pipeline and a fourth heat exchange pipeline, and the regenerator includes a fifth heat exchange pipeline and a sixth heat exchange pipeline;

[0012] The third heat exchange pipeline is used to connect the outlet of the second reservoir and the inlet of the fifth heat exchange pipeline;

[0013] The fourth heat exchange pipeline is used to connect the outlet of the sixth heat exchange pipeline and the inlet of the second heat exchange pipeline;

[0014] The fifth heat exchange pipeline is used to connect the outlet of the third heat exchange pipeline and the inlet of the expander;

[0015] The sixth heat exchange pipeline is used to connect the outlet of the expander and the inlet of the fourth heat exchange pipeline;

[0016] The carbon dioxide in the third heat exchange pipeline absorbs heat from the carbon dioxide in the fourth heat exchange pipeline; the carbon dioxide in the fifth heat exchange pipeline absorbs heat from the carbon dioxide in the sixth heat exchange pipeline, so that the carbon dioxide entering the expander is heated.

[0017] Optionally, in the above energy storage system, an external heat source heating component is provided between the outlet of the fifth heat exchange pipeline and the inlet of the expander, and the external heat source heating component is used to heat the carbon dioxide entering the expander.

[0018] Optionally, in the above energy storage system, a second compressor and a second cooling device are connected in series between the first cooling device and the condenser, and the second compressor is connected to the first cooling device.

[0019] Optionally, the above-mentioned energy storage system further includes a second pipeline connected between the outlet of the first compressor and the inlet of the first cooling device, the second pipeline includes a third compressor and a heat storage heat exchanger connected in series, the inlet of the third compressor is connected to the outlet of the first compressor, and the outlet of the heat storage heat exchanger is connected to the outlet of the second cooling device.

[0020] Optionally, the above-mentioned energy storage system further includes a cold tank and a hot tank. In the energy storage stage, the heat exchange medium in the cold tank absorbs the heat of the heat storage heat exchanger and enters the hot tank; in the energy release stage, the heat exchange medium in the hot tank transfers the heat to the heat release heat exchanger.

[0021] Optionally, the above-mentioned energy storage system also includes a gas-liquid separator, the inlet of the gas-liquid separator is connected to the outlet of the first heat exchange pipeline, the liquid outlet of the gas-liquid separator is connected to the liquid inlet of the first reservoir, and the gas outlet of the gas-liquid separator is connected to the inlet of the second compressor.

[0022] Optionally, in the above energy storage system, the energy release pipeline includes an inlet capable of extending into the first reservoir and extending below the liquid level formed by the carbon dioxide, so as to fully mix the gaseous carbon dioxide with the liquid carbon dioxide.

[0023] Optionally, in the above energy storage system, the energy storage pipeline includes an air outlet and a liquid inlet connected to the first reservoir, the air outlet is arranged at the top of the first reservoir, and the liquid inlet is arranged above the liquid level formed by the carbon dioxide.

[0024] Optionally, in the above energy storage system, a second throttle valve is provided between the liquid outlet of the gas-liquid separator and the liquid inlet of the first reservoir.

[0025] The present application provides an energy storage system, which includes a first reservoir and a second reservoir, and the carbon dioxide in the first reservoir is in a coexisting state of gas, liquid and solid. In the energy storage stage, the gaseous carbon dioxide output by the first reservoir enters the second reservoir after compression, phase change and pressurization. In the energy release stage, the liquid carbon dioxide output by the second reservoir returns to the first reservoir after phase change, expansion and power generation. In this way, not only the system is simplified and the structure is compact, but also the power generation efficiency is improved. The present application applies the cold energy in the energy storage stage to the energy release stage by setting a cold storage heat exchanger, avoiding the setting of other cooling components, not only realizing full utilization of energy, but also saving construction costs and optimizing the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0027] Figure 1 A diagram illustrating the working principle of an energy storage system provided in an embodiment of the present application.

[0028] exist Figure 1 middle:

[0029] 1. First reservoir; 2. First compressor; 3. First cooling device; 4. Condenser; 5. Power unit; 6. Second reservoir; 7. Expander; 8. First throttle valve; 9. Cold storage heat exchanger; 10. Heat release heat exchanger; 11. Regenerator; 12. External heat source heating component; 13. Second compressor; 14. Second cooling device; 15. Third compressor; 16. Heat storage heat exchanger; 17. Cold tank; 18. Hot tank; 19. Gas-liquid separator; 20. Second throttle valve. DETAILED DESCRIPTION

[0030] The present application provides an energy storage system, which makes the system structure compact and simple, not only saving the setting of components but also improving the power generation efficiency.

[0031] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0032] like Figure 1 As shown, an embodiment of the present application provides an energy storage system, including an energy storage pipeline, an energy release pipeline and a first pipeline. It should be noted that the carbon dioxide in the first reservoir 1 is in a coexistence state of gaseous, liquid and solid states, and the carbon dioxide in the second reservoir 6 is in a liquid state higher than the critical pressure. Specifically, the first reservoir 1, the first compressor 2, the first cooling device 3, the condenser 4, the power device 5, and the second reservoir 6 connected in series in sequence constitute an energy storage pipeline. The gaseous carbon dioxide output by the first reservoir 1 enters the second reservoir 6 for storage after compression, cooling, liquefaction and pressurization. This process realizes the storage of electrical energy; the second reservoir 6, the heating device, the expander 7, and the first reservoir 1 connected in series in sequence constitute an energy release pipeline. The liquid carbon dioxide output by the second reservoir 6 enters the first reservoir 1 after gasification, expansion and power generation. This process realizes the release of electrical energy; the first pipeline The cold storage heat exchanger 9 includes a first throttle valve 8 and a cold storage heat exchanger 9. The first throttle valve 8 is connected to the condenser 4. The cold storage heat exchanger 9 includes at least a first heat exchange pipeline and a second heat exchange pipeline. The first heat exchange pipeline is used to connect the first throttle valve 8 and the first reservoir 1. The second heat exchange pipeline is used to connect the expander 7 and the first reservoir 1. The cold storage medium in the cold storage heat exchanger 9 is used to absorb the cold released by the carbon dioxide flowing through the first heat exchange pipeline and transfer the cold to the carbon dioxide flowing through the second heat exchange pipeline.

[0033] It can be seen that the present application uses carbon dioxide to store and release electrical energy, which not only reduces the volume of the energy storage reservoir but also makes the system more compact compared to compressed air energy storage. The setting of the cold storage heat exchanger 9 uses the cold energy released by the carbon dioxide in the energy storage process to cool the carbon dioxide in the energy release process, avoiding the actual setting of cooling components, improving the energy utilization rate within the system, and improving the simplicity of the system.

[0034] It should be noted that the energy storage system in this application can perform intermittent electricity storage and power generation based on peak and valley electricity, and can also operate continuously as a thermal power generation cycle.

[0035] It should also be noted that the power device 5 can be but is not limited to a booster pump; the cold storage medium can be but is not limited to an organic solution or liquid organic matter or a phase change cold storage material, etc.; preferably, the first reservoir 1 is an insulated pressure vessel.

[0036] Furthermore, the heating device includes a heat-releasing heat exchanger 10 and a regenerator 11. The heat-releasing heat exchanger 10 includes a third heat exchange pipeline and a fourth heat exchange pipeline, and the regenerator 11 includes a fifth heat exchange pipeline and a sixth heat exchange pipeline. The third heat exchange pipeline is used to connect the outlet of the second reservoir 6 and the inlet of the fifth heat exchange pipeline. The fourth heat exchange pipeline is used to connect the outlet of the sixth heat exchange pipeline and the inlet of the second heat exchange pipeline. The fifth heat exchange pipeline is used to connect the outlet of the third heat exchange pipeline and the inlet of the expander 7. The sixth heat exchange pipeline is used to connect the outlet of the expander 7 and the inlet of the fourth heat exchange pipeline. The carbon dioxide in the third heat exchange pipeline absorbs the heat of the carbon dioxide in the fourth heat exchange pipeline. The carbon dioxide in the fifth heat exchange pipeline absorbs the heat of the carbon dioxide in the sixth heat exchange pipeline, thereby increasing the temperature of the carbon dioxide entering the expander 7. As can be seen from the above, the present application utilizes the heat of the carbon dioxide discharged from the expander 7 to heat the carbon dioxide about to enter the expander 7, thereby achieving heat exchange between energy storage media and improving power generation efficiency.

[0037] Furthermore, an external heat source heating assembly 12 is provided between the outlet of the fifth heat exchange pipeline and the inlet of the expander 7. The external heat source heating assembly 12 is used to heat the carbon dioxide entering the expander 7. The external heat source heating assembly 12 includes an external heat source and a heater provided between the outlet of the fifth heat exchange pipeline and the inlet of the expander 7 (it may also be other components commonly used in the art that can achieve this function). The heater is used to provide heat from the external heat source to the carbon dioxide, that is, the heat is transferred to the heater through the external heat source. The heater allows the carbon dioxide to pass through and heats the carbon dioxide. In this way, the temperature of the carbon dioxide entering the expander 7 is increased. As the temperature of the carbon dioxide increases, it means that it can release more heat energy, thereby doing more work during the expansion process, thereby improving the efficiency of expansion power generation.

[0038] It should be noted that the external heat source can be a fuel combustion heat source, a nuclear reaction heat source, solar thermal energy, etc.; the heat supply of the external heat source can be determined according to the system.

[0039] In some optional embodiments, a second compressor 13 and a second cooling device 14 are connected in series between the first cooling device 3 and the condenser 4, and the second compressor 13 is connected to the first cooling device 3. It can be understood that the first cooling device 3 is provided between the first compressor 2 and the second compressor 13, that is, a two-stage compression and intercooling arrangement is adopted to reduce compression work loss and improve energy storage efficiency. At the same time, the carbon dioxide is cooled by the cooling device after compression. Cooling can reduce the increase in power consumption during the carbon dioxide compression process caused by the increase in temperature, thereby improving the overall energy storage efficiency.

[0040] Furthermore, the energy storage system also includes a second pipeline connected between the outlet of the first compressor 2 and the inlet of the first cooling device 3. The second pipeline includes a third compressor 15 and a heat storage heat exchanger 16 connected in series. The inlet of the third compressor 15 is connected to the outlet of the first compressor 2, and the outlet of the heat storage heat exchanger 16 is connected to the outlet of the second cooling device 14. It can be understood that after the carbon dioxide is compressed by the first compressor 2, a part of the carbon dioxide continues to enter the second compressor 13 for further compression, while the other part enters the third compressor 15, and then the above two parts of carbon dioxide are merged. This diversion and re-merger design can improve the flexibility and efficiency of the system because it allows for more precise temperature and pressure control of different parts of the fluid. In addition, this design can also improve the thermodynamic performance of the system because it helps to optimize the heat exchange process and reduce irreversible losses, thereby improving the energy storage efficiency of the entire energy storage system.

[0041] In addition, the energy storage system also includes a cold tank 17 and a hot tank 18. During the energy storage phase, the heat exchange medium in cold tank 17 absorbs heat from the heat storage heat exchanger 16 and enters the hot tank 18. During the energy release phase, the heat exchange medium in hot tank 18 transfers heat to the heat release heat exchanger 10. This allows for efficient energy storage and release, achieving full heat utilization. This design allows the system to store and utilize thermal energy at different temperature levels, thereby improving overall energy storage efficiency.

[0042] It should be noted that the heat exchange medium can be, but is not limited to, water or thermal oil.

[0043] In some optional embodiments, the energy storage system further includes a gas-liquid separator 19, the inlet of the gas-liquid separator 19 being connected to the outlet of the first heat exchange pipeline, the liquid outlet of the gas-liquid separator 19 being connected to the liquid inlet of the first reservoir 1, and the gas outlet of the gas-liquid separator 19 being connected to the inlet of the second compressor 13. After the liquid carbon dioxide passes through the first heat exchange pipeline of the cold storage heat exchanger 9, it becomes a gas-liquid two-phase, wherein the gaseous carbon dioxide is connected to the inlet of the second compressor 13 for further energy storage, and the liquid carbon dioxide returns to the first reservoir 1 to prepare for the next step of energy storage. The separated liquid and gaseous carbon dioxide can be thermally managed more effectively.

[0044] In some optional embodiments, the energy release pipeline includes an inlet that can extend into the first reservoir 1 and extend below the liquid level formed by the carbon dioxide. Because the carbon dioxide entering the second reservoir 6 during the energy release stage is in gaseous form, the above-mentioned setting allows the gaseous carbon dioxide and liquid carbon dioxide to be fully mixed.

[0045] In some optional embodiments, the energy storage pipeline includes an air outlet and a liquid inlet connected to the first reservoir 1. The air outlet is arranged at the top of the first reservoir 1, and the liquid inlet is arranged above the liquid level formed by the carbon dioxide. Such an arrangement facilitates the inflow and outflow of carbon dioxide.

[0046] In some optional embodiments, a second throttle valve 20 is provided between the liquid outlet of the gas-liquid separator 19 and the liquid inlet of the first reservoir 1. The provision of the second throttle valve 20 can further regulate (i.e., reduce) the pressure of the liquid carbon dioxide entering the first reservoir 1, so that the second throttle valve 20 can share part of the function of the first throttle valve 8, making the selection of the first throttle valve 8 and the second throttle valve 20 more flexible. At the same time, the provision of the second throttle valve 20 can also temporarily assume the entire pressure regulation function of the liquid carbon dioxide in the event that the first throttle valve 8 is damaged.

[0047] The working principle of the energy storage system in this application is as follows.

[0048] Energy storage stage:

[0049] The first reservoir 1 is at a first pressure and outputs gaseous carbon dioxide. At this time, the liquid carbon dioxide in the first reservoir 1 changes phase to a solid state. The gaseous carbon dioxide is compressed to a second pressure by the first compressor 2 and separated into two streams. The first stream of carbon dioxide is cooled by the first cooling device 3, merged with the carbon dioxide from the gas-liquid separator 19, and then compressed to a third pressure by the second compressor 13. It is then cooled by the second cooling device 14. The second stream of carbon dioxide is compressed to the third pressure by the third compressor 15, and then the compression heat is recovered by the thermal storage and release device. Then, the two streams of carbon dioxide are merged and enter the condenser 4 for liquefaction. The main stream is boosted to a fourth pressure by the booster pump and then input into the second reservoir 6. The diverted stream is expanded and reduced in pressure by the first throttle valve 8, and then released a portion of the cold energy by the cold storage heat exchanger 9. It is then separated by the gas-liquid separator 19. The gas is merged into the second compressor 13, and the liquid is expanded and reduced in pressure by the second throttle valve 20 and returned to the first reservoir 1.

[0050] Energy release stage:

[0051] The second storage tank 6 outputs liquid carbon dioxide, which absorbs heat through the heat-releasing heat exchanger 10, then absorbs heat through the regenerator 11, and then absorbs heat through the heater. The heat of the heater comes from an external heat source. The high-temperature and high-pressure gaseous carbon dioxide enters the expander 7 to expand and generate electricity and is reduced in pressure to the fifth pressure. The exhaust of the expander 7 releases waste heat through the regenerator 11 and the heat-releasing heat exchanger 10, and then returns to the first storage tank 1 after being cooled by the cold storage heat exchanger 9, and exchanges heat with the solid energy storage working fluid in the energy storage tank to change into liquid state.

[0052] The basic principles of the present application have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this application are merely illustrative and not restrictive, and it should not be assumed that these advantages, strengths, and effects are required of each embodiment of this application. In addition, the specific details disclosed above are merely illustrative and facilitating understanding, and are not restrictive. The above details do not limit this application to necessarily being implemented using the above specific details.

[0053] The block diagrams of the devices, devices, equipment, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, devices, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "include," "comprise," "have," and the like are open-ended words, meaning "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0054] It should also be noted that in the apparatus, device, and energy storage system of the present application, each component or each step can be decomposed and / or recombined. Such decomposition and / or recombination should be regarded as equivalent solutions of the present application.

[0055] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0056] It should be understood that the qualifiers "first", "second", "third", "fourth", "fifth" and "sixth" used in the description of the embodiments of the present application are only used to more clearly illustrate the technical solutions and cannot be used to limit the scope of protection of the present application.

[0057] The above description has been provided for the purpose of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. An energy storage system, characterized in that: include: An energy storage pipeline comprises a first reservoir (1), a first compressor (2), a first cooling device (3), a condenser (4), a power device (5), and a second reservoir (6) which are sequentially connected in series, so as to utilize the compression process and phase change process of carbon dioxide to store electrical energy; An energy release pipeline comprises the second reservoir (6), a heating device, an expander (7), and the first reservoir (1) connected in series, so as to release electrical energy by utilizing the phase change process and expansion process of the carbon dioxide; A first pipeline is connected to the outlet of the condenser (4) and includes a first throttle valve (8) and a cold storage heat exchanger (9), wherein the first throttle valve (8) is in communication with the condenser (4), and the cold storage heat exchanger (9) includes at least a first heat exchange pipeline and a second heat exchange pipeline, wherein the first heat exchange pipeline is used to connect the first throttle valve (8) and the first reservoir (1), and the second heat exchange pipeline is used to connect the expander (7) and the first reservoir (1); The carbon dioxide in the first reservoir (1) is in a coexisting state of gas, liquid and solid, and the carbon dioxide in the second reservoir (6) is in a liquid state with a pressure higher than the critical pressure; The cold storage medium in the cold storage heat exchanger is used to absorb the cold released by the carbon dioxide flowing through the first heat exchange pipeline and transfer the cold to the carbon dioxide flowing through the second heat exchange pipeline.

2. The energy storage system according to claim 1, characterized in that The heating device comprises a heat-releasing heat exchanger (10) and a regenerator (11), wherein the heat-releasing heat exchanger (10) comprises a third heat exchange pipeline and a fourth heat exchange pipeline, and the regenerator (11) comprises a fifth heat exchange pipeline and a sixth heat exchange pipeline; The third heat exchange pipeline is used to connect the outlet of the second reservoir (6) and the inlet of the fifth heat exchange pipeline; The fourth heat exchange pipeline is used to connect the outlet of the sixth heat exchange pipeline and the inlet of the second heat exchange pipeline; The fifth heat exchange pipeline is used to connect the outlet of the third heat exchange pipeline and the inlet of the expander (7); The sixth heat exchange pipeline is used to connect the outlet of the expander (7) and the inlet of the fourth heat exchange pipeline; The carbon dioxide in the third heat exchange pipeline absorbs the heat of the carbon dioxide in the fourth heat exchange pipeline; and the carbon dioxide in the fifth heat exchange pipeline absorbs the heat of the carbon dioxide in the sixth heat exchange pipeline, so that the temperature of the carbon dioxide entering the expander (7) is increased.

3. The energy storage system according to claim 2, characterized in that: An external heat source heating component (12) is provided between the outlet of the fifth heat exchange pipeline and the inlet of the expander (7), and the external heat source heating component (12) is used to heat the carbon dioxide entering the expander (7).

4. The energy storage system according to claim 1, characterized in that A second compressor (13) and a second cooling device (14) are connected in series between the first cooling device (3) and the condenser (4), and the second compressor (13) is in communication with the first cooling device (3).

5. The energy storage system according to claim 4, characterized in that: The invention also includes a second pipeline connected between the outlet of the first compressor (2) and the inlet of the first cooling device (3), wherein the second pipeline includes a third compressor (15) and a heat storage heat exchanger (16) connected in series, wherein the inlet of the third compressor (15) is connected to the outlet of the first compressor (2), and the outlet of the heat storage heat exchanger (16) is connected to the outlet of the second cooling device (14).

6. The energy storage system according to claim 5, characterized in that: The invention also includes a cold tank (17) and a hot tank (18). In the energy storage stage, the heat exchange medium in the cold tank (17) absorbs the heat of the heat storage heat exchanger (16) and enters the hot tank (18); in the energy release stage, the heat exchange medium in the hot tank (18) transfers the heat to the heat release heat exchanger (10).

7. The energy storage system according to claim 4, characterized in that: It also includes a gas-liquid separator (19), the inlet of the gas-liquid separator (19) is connected to the outlet of the first heat exchange pipeline, the liquid outlet of the gas-liquid separator (19) is connected to the liquid inlet of the first reservoir (1), and the gas outlet of the gas-liquid separator (19) is connected to the inlet of the second compressor (13).

8. The energy storage system according to claim 1, characterized in that: The energy release pipeline comprises an inlet capable of extending into the first reservoir (1) and extending below the liquid level formed by the carbon dioxide, so as to fully mix the gaseous carbon dioxide with the liquid carbon dioxide.

9. The energy storage system according to claim 1, characterized in that: The energy storage pipeline comprises an air outlet and a liquid inlet communicated with the first reservoir (1), the air outlet is arranged at the top of the first reservoir (1), and the liquid inlet is arranged above the liquid level formed by the carbon dioxide.

10. The energy storage system according to claim 7, characterized in that: A second throttle valve (20) is provided between the liquid outlet of the gas-liquid separator (19) and the liquid inlet of the first reservoir (1).

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