A constant pressure carbon dioxide energy storage system

Abstract

The present invention discloses a constant-pressure carbon dioxide energy storage system, which switches the energy storage system between the energy storage state and the energy release state, changes the pressure and temperature of carbon dioxide to achieve liquefaction and gasification, and completes the energy storage and energy release process; and a pressure-stabilizing tank and a matching on-off valve are arranged in the carbon dioxide energy storage system, so that the pressure in the low-pressure liquid storage module and the high-pressure liquid storage module of the carbon dioxide energy storage system in the energy storage state and the energy release state is balanced, and the liquid outlet pressure of the low-pressure liquid storage module and the high-pressure liquid storage module is stabilized. At the same time, the present invention uses the energy storage passage and the energy release passage to share the same pipeline in the cold storage and release components and the heat storage and release components, and converts the liquid carbon dioxide output by the low-pressure liquid storage module through a throttle valve, thereby reducing the demand for phase change materials and reducing the cost of building an energy storage system; in addition, the carbon dioxide in the present invention is stored in liquid form, which reduces the area occupied by the system.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage, and in particular relates to a constant-pressure carbon dioxide energy storage system. Background Art

[0002] In the context of rapid development of new energy, new energy storage has become one of the key links in building a new power system. Liquid carbon dioxide energy storage converts electrical energy into thermal energy and potential energy of carbon dioxide to achieve energy storage. Compared with air, carbon dioxide is easier to liquefy, does not need to rely on underground caves, and has more flexible site selection. In addition, carbon dioxide has high specific heat capacity, good heat transfer performance, lower parasitic energy consumption, and higher system efficiency. Therefore, liquid carbon dioxide energy storage has the advantages of ultra-long time, large scale, high flexibility, high efficiency, and high energy storage density, and has more development prospects.

[0003] However, during the carbon dioxide energy storage process, when the mass of carbon dioxide in the high-pressure storage tank and the low-pressure storage tank changes, the pressure in the high-pressure storage tank and the low-pressure storage tank will be unbalanced, so additional equipment or additional measures need to be added to maintain the pressure in the high-pressure storage tank and the low-pressure storage tank. For example, in the patent with publication number CN112901298A, entitled A Constant Pressure Compressed Carbon Dioxide Energy Storage System and Method, the pressure in the high-pressure storage tank and the low-pressure storage tank is maintained constant by moving the piston; but the pressure balance in the tank is maintained by adaptively modifying the volume of the liquid storage tank, which is more complicated to achieve. Summary of the invention

[0004] The object of the present invention is to provide a constant-pressure carbon dioxide energy storage system.

[0005] The present invention provides a constant-pressure carbon dioxide energy storage system, which includes a pressure-sustaining tank, a low-pressure liquid storage module, a first heat exchange component, a compression-expansion module, a second heat exchange component and a high-pressure liquid storage module; the compression-expansion module includes a compressor and an expander in parallel; the low-pressure liquid storage module, the first heat exchange component, the compressor, the second heat exchange component and the high-pressure liquid storage module form an energy storage passage. The high-pressure liquid storage module, the second heat exchange component, the expander, the first heat exchange component and the low-pressure liquid storage module form an energy release passage. The pressure-sustaining tank is connected to the low-pressure liquid storage module through a first on-off valve; the pressure-sustaining tank is connected to the high-pressure liquid storage module through a second on-off valve; the pressure-sustaining tank is connected to the second heat exchange component in the energy release passage. During operation, the energy storage system switches between an energy storage state and an energy release state.

[0006] In the energy storage state, the first on-off valve is opened and the second on-off valve is closed; the liquid carbon dioxide in the low-pressure liquid storage module is input into the energy storage path under the action of the pressure difference, and is stored in the high-pressure liquid storage module through the process of gasification, compressor work pressurization, and liquefaction. The pressure regulating tank delivers carbon dioxide gas to the low-pressure liquid storage module to keep the internal pressure of the low-pressure liquid storage module stable.

[0007] In the energy release state, the second on-off valve is opened and the first on-off valve is closed; the liquid carbon dioxide in the high-pressure liquid storage module is input into the energy release passage under the action of the pressure difference, and is stored in the low-pressure liquid storage module after the process of gasification, expansion and pressure reduction in the expander to release energy, and liquefaction. Part of the gaseous carbon dioxide generated by gasification in the second heat exchange component is filled into the pressure stabilizing tank and the high-pressure liquid storage module to keep the internal pressure of the high-pressure liquid storage module stable.

[0008] Preferably, in the energy storage state, liquid carbon dioxide entering the energy storage passage is converted into gaseous carbon dioxide through the first heat exchange component, and the released cold is stored by the first heat exchange component; the compressor increases the pressure of the gaseous carbon dioxide; the gaseous carbon dioxide is converted into liquid carbon dioxide in the second heat exchange component and input into the high-pressure liquid storage module, and the released heat is stored by the second heat exchange component.

[0009] In the energy release state, the liquid carbon dioxide entering the energy release passage is converted into gaseous carbon dioxide through the second heat exchange component, and the released heat is stored by the second heat exchange component; the gaseous carbon dioxide expands in the expander to release energy, and the pressure decreases; the gaseous carbon dioxide is converted into liquid carbon dioxide in the first heat exchange component and input into the high-pressure liquid storage module, and the released cold is stored by the second heat exchange component.

[0010] Preferably, the first heat exchange component includes one or multiple cold storage and release components connected in sequence; the second heat exchange component includes one or multiple heat storage and release components connected in sequence.

[0011] Preferably, the first heat exchange component includes a primary cold storage and release component and a secondary cold storage and release component, and the primary cold storage and release component is connected to the low-pressure liquid storage module; the second heat exchange component includes a primary heat storage and release component and a secondary heat storage and release component, and the secondary heat storage and release component is connected to the high-pressure liquid storage module; carbon dioxide undergoes phase change in the primary cold storage and release component and the secondary heat storage and release component.

[0012] Preferably, the cold storage and release components and the thermal storage and release components both use heat exchangers with phase change materials. The energy storage path and the energy release path share the same pipeline in the cold storage and release components and the thermal storage and release components. In the first heat exchange component, the cold released by the gasification of carbon dioxide in the energy storage state is stored in the phase change material of the cold storage and release component, and the carbon dioxide is supplied for liquefaction in the energy release state. In the second heat exchange component, the heat released by the liquefaction of carbon dioxide in the energy storage state is stored in the phase change material of the thermal storage and release component, and the carbon dioxide is supplied for gasification in the energy release state.

[0013] Preferably, the cold storage and release assembly and the heat storage and release assembly have the same structure, and both include a first heat exchanger, a heat storage tank, a second heat exchanger and a cold storage tank which are sequentially connected to form a circulation loop through a heat exchange medium pipeline. The first heat exchanger is connected in series in the energy storage path; the second heat exchanger is connected in series in the energy release path.

[0014] In the cold storage and release component, the cold released by the gasification of carbon dioxide in the energy storage state is stored in the cold storage tank by means of heat exchange between the first heat exchanger and the heat exchange medium, and is supplied to the liquefied carbon dioxide in the energy release state by means of heat exchange between the second heat exchanger and the heat exchange medium.

[0015] In the heat storage and heat release component, the heat released by the liquefaction of carbon dioxide in the energy storage state is stored in the heat storage tank by heat exchange between the second heat exchanger and the heat exchange medium, and is supplied to the gasified carbon dioxide in the energy release state by heat exchange between the first heat exchanger and the heat exchange medium.

[0016] Preferably, the energy storage circuit is provided with a throttle valve; the throttle valve is located between the low-pressure liquid storage module and the first heat exchange component. In the energy storage state, the flow cross-sectional area of ​​the liquid carbon dioxide output by the low-pressure liquid storage module is reduced when passing through the throttle valve, and is converted into gas-liquid two-phase carbon dioxide under the throttling gasification action.

[0017] Preferably, the input and output ends of the compressor are both provided with a fourth on-off valve in the energy storage path; the input and output ends of the expander are both provided with a fifth on-off valve in the energy release path. In the energy storage state, the fourth on-off valve is opened and the fifth on-off valve is closed; in the energy release state, the fourth on-off valve is closed and the fifth on-off valve is opened.

[0018] Preferably, the first heat exchange component is provided with a plurality of cold storage and release components; along the direction from the energy storage passage to the energy release passage, the phase change temperature of the phase change material in each cold storage and release component increases successively; each cold storage and release component absorbs the cold released by the gasification of carbon dioxide step by step in the energy storage state, and provides the cold required for liquefaction to carbon dioxide step by step in the energy release state; the second heat exchange component is provided with a heat storage and release component; along the direction from the energy storage passage to the energy release passage, the phase change temperature of the phase change material in each heat storage and release component decreases successively; each heat storage and release component absorbs the heat released by the liquefaction of carbon dioxide step by step in the energy storage state, and provides the heat required for gasification to carbon dioxide step by step in the energy release state.

[0019] Preferably, the energy release passage is provided with a third on-off valve; the third on-off valve is located between the low-pressure liquid storage module and the first heat exchange component.

[0020] The present invention has the following beneficial effects:

[0021] 1. The present invention provides a pressure-stabilizing tank and a matching on-off valve in the carbon dioxide energy storage system, so that the pressure in the low-pressure liquid storage module and the high-pressure liquid storage module of the carbon dioxide energy storage system in the energy storage state and the energy release state is balanced, and the liquid outlet pressure of the low-pressure liquid storage module and the high-pressure liquid storage module is stabilized.

[0022] 2. The present invention uses the same pipeline for energy storage and release passages in both the cold storage and release components and the heat storage and release components, thereby reducing the cost of building the energy storage system; at the same time, the carbon dioxide in the present invention is stored in liquid form, reducing the system footprint. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the system structure of Example 1 of the present invention.

[0024] Figure 2 This is a schematic diagram of the system structure of Example 2 of the present invention.

[0025] Figure numerals: 1. low-pressure liquid storage module; 2. cold storage component; 3. compressor; 4. heat storage component; 5. high-pressure liquid storage module; 6. heat release component; 7. expander; 8. cold release component; 9. pressure-stabilizing tank; 10. throttle valve; 11. first on-off valve; 12. second on-off valve; 13. third on-off valve; 14. fourth on-off valve; 15. fifth on-off valve. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings.

[0027] Example 1

[0028] like Figure 1 As shown, a constant pressure carbon dioxide energy storage system includes a low pressure liquid storage module 1, a cold storage component 2, a compressor 3, a heat storage component 4, a high pressure liquid storage module 5, a heat release component 6, an expander 7, a cold release component 8 and a pressure stabilizing tank 9; the low pressure liquid storage module 1, the cold storage component 2, the compressor 3, the heat storage component 4 and the high pressure liquid storage module 5 form an energy storage path. The high pressure liquid storage module 5, the heat release component 6, the expander 7, the cold release component 8 and the low pressure liquid storage module 1 form an energy release path.

[0029] A throttle valve 10 is provided between the low-pressure liquid storage module 1 and the cold storage assembly 2. When the liquid carbon dioxide output by the low-pressure liquid storage module 1 passes through the throttle valve 10, the flow cross-sectional area is reduced and converted into gas-liquid two-phase carbon dioxide. The cold storage assembly 2 includes a primary cold storage device and a secondary cold storage device connected in series; the heat storage assembly 4 includes a primary heat storage device and a secondary heat storage device connected in series; the heat release assembly 6 includes a primary heat release device and a secondary heat release device connected in series; the cold release assembly 8 includes a primary heat release device and a secondary heat release device connected in series; a heat storage tank and a cold storage tank are connected in parallel between the primary cold storage device and the primary cold release device, between the secondary cold storage device and the secondary cold release device, between the primary heat storage device and the primary heat release device, and between the secondary heat storage device and the secondary heat release device. The pressure stabilizing tank 9 is connected to the low-pressure liquid storage module 1 through the first on-off valve 11; the pressure stabilizing tank 9 is connected to the high-pressure liquid storage module 5 through the second on-off valve 12; the pressure stabilizing tank 9 is connected between the primary heat storage device and the secondary heat storage device. During operation, the energy storage system switches between an energy storage state and an energy release state.

[0030] In the energy storage state, the liquid carbon dioxide in the low-pressure liquid storage module 1 passes through the opened throttle valve 10 under the action of pressure difference, and is converted into gas-liquid two-phase carbon dioxide under the action of throttling gasification, and enters the cold storage component 2; in the process of the low-pressure liquid storage module 1 outputting carbon dioxide, the first on-off valve 11 is opened and the second on-off valve 12 is closed; the pressure regulating tank 9 transports gaseous carbon dioxide to the low-pressure liquid storage module 1 to keep the internal pressure of the low-pressure liquid storage module 1 stable. The first-stage cold storage device and the second-stage cold storage device exchange heat with the carbon dioxide input into the cold storage component 2 through the heat exchange medium input from the corresponding heat storage tank, respectively, so that the gas-liquid two-phase carbon dioxide is gradually heated in the cold storage component 2, and the gaseous carbon dioxide is output, and the heat exchange medium is transported to the corresponding cold storage tank for storage. The compressor 3 consumes electric energy to pressurize the gaseous carbon dioxide output from the cold storage component 2, and then inputs it into the heat storage component 4. The primary heat storage device and the secondary heat storage device respectively exchange heat with the carbon dioxide input into the heat storage component 4 through the heat exchange medium input from the corresponding cold storage tank, so that the gaseous carbon dioxide is gradually cooled in the heat storage component 4, and liquid carbon dioxide is obtained and transported to the high-pressure liquid storage module 5 for storage. The heat exchange medium is transported to the corresponding heat storage tank for storage to complete energy storage.

[0031] In the energy release state, the liquid carbon dioxide in the high-pressure liquid storage module 5 is input into the secondary heat release device. The secondary heat release device exchanges heat with the carbon dioxide input into the secondary heat release device through the heat exchange medium input from the corresponding heat storage tank, converting the liquid carbon dioxide into gaseous carbon dioxide and outputting it. Part of the carbon dioxide output from the secondary heat release device enters the primary heat release device, and the other part enters the pressure-stabilizing tank 9, and the carbon dioxide gas is transported to the high-pressure liquid storage module 5 through the on-off valve opened between the high-pressure liquid storage module 5 and the pressure-stabilizing tank 9, so that the output port pressure of the high-pressure liquid storage module 5 is stable. The primary heat release device exchanges heat with the carbon dioxide input into the primary heat release device through the heat exchange medium input from the corresponding heat storage tank, further increasing the temperature of the carbon dioxide. The gaseous carbon dioxide heated in the primary heat release device is input into the expander 7, and the expander 7 performs work externally through the expansion of the gaseous carbon dioxide, and releases energy to complete the energy release. The first-stage cooling device and the second-stage cooling device respectively exchange heat with the carbon dioxide input into the cooling component 8 through the heat exchange medium input from the corresponding cooling tank, so that the gaseous carbon dioxide is gradually cooled in the cooling component 8, and liquid carbon dioxide is obtained and transported to the low-pressure liquid storage module 1 for storage through the third on-off valve 13, and the heat exchange medium is transported to the corresponding heat storage tank for storage.

[0032] Example 2

[0033] like Figure 2 As shown, a carbon dioxide energy storage system for heat recycling includes a pressure stabilizing tank 9, a low-pressure liquid storage module 1, a first heat exchange component, a compressor 3, an expander 7, a second heat exchange component and a high-pressure liquid storage module 5. The low-pressure liquid storage module 1, the first heat exchange component, the compressor 3, the second heat exchange component and the high-pressure liquid storage module 5 form an energy storage passage. The high-pressure liquid storage module 5, the second heat exchange component, the expander 7, the first heat exchange component and the low-pressure liquid storage module 1 form an energy release passage. A throttle valve 10 is provided on the energy storage passage; the throttle valve 10 is located between the low-pressure liquid storage module 1 and the first heat exchange component. The first heat exchange assembly and the second heat exchange assembly each include two heat exchangers, each heat exchanger stores phase change materials, and the phase change points of the four heat exchangers along the low-pressure liquid storage module 1 to the high-pressure liquid storage module 5 are 5°C, 20°C, 280°C, and 30°C respectively; the energy storage path and the energy release path share the same pipeline in the first heat exchange assembly and the second heat exchange assembly; the pressure stabilizing tank 9 is connected to the high-pressure liquid storage module 5 through the second on-off valve 12; the pressure stabilizing tank 9 is connected to the second heat exchange assembly in the energy release path. During operation, the energy storage system switches between the energy storage state and the energy release state.

[0034] In the energy storage state, the liquid carbon dioxide in the low-pressure liquid storage module 1 passes through the opened throttle valve 10 under the action of pressure difference, and is converted into gas-liquid two-phase carbon dioxide under the action of throttling gasification, and enters the first heat exchange component; in the process of the low-pressure liquid storage module 1 outputting carbon dioxide, the first on-off valve 11 is opened and the second on-off valve 12 is closed; the pressure regulating tank 9 transports gaseous carbon dioxide to the low-pressure liquid storage module 1 to keep the internal pressure of the low-pressure liquid storage module 1 stable. The phase change materials stored in the two heat exchangers in the first heat exchange component exchange heat with carbon dioxide respectively, so that the gas-liquid two-phase carbon dioxide is gradually heated in the first heat exchange component to obtain gaseous carbon dioxide. The gaseous carbon dioxide output by the first heat exchange component is input into the compressor 3 through the fourth on-off valve 14 provided at the input end of the compressor 3; after the compressor 3 consumes electric energy to pressurize the gaseous carbon dioxide output by the first heat exchange component, it is input into the second heat exchange component through the fourth on-off valve 14 provided at the output end of the compressor 3. The phase change materials stored in the two heat exchangers in the second heat exchange component exchange heat with carbon dioxide respectively, so that the gaseous carbon dioxide is gradually cooled in the second heat exchange component, liquid carbon dioxide is obtained, and transported to the high-pressure liquid storage module 5 for storage, thereby completing energy storage.

[0035] In the energy release state, the liquid carbon dioxide in the high-pressure liquid storage module 5 is input into the second heat exchange component; the phase change materials stored in the two heat exchangers in the second heat exchange component exchange heat with carbon dioxide respectively, and after the heat exchanger directly connected to the high-pressure liquid storage module 5 converts the liquid carbon dioxide into gaseous carbon dioxide, the second on-off valve 12 is opened and the first on-off valve 11 is closed; a part of the gaseous carbon dioxide is filled into the pressure-stabilizing tank 9 and the high-pressure liquid storage module 5, so that the internal pressure of the high-pressure liquid storage module 5 is kept stable. Another part of the gaseous carbon dioxide enters the heat exchanger directly connected to the expander 7 for further heat exchange, and is input into the expander 7 through the fifth on-off valve 15 provided at the input end of the expander 7. The expander 7 performs work externally through the expansion of the gaseous carbon dioxide and releases energy to complete the energy release. The carbon dioxide output by the expander 7 is input into the first heat exchange component through the fifth on-off valve 15 provided at the output end of the expander 7. The phase change materials stored in the two heat exchangers in the first heat exchange component exchange heat with carbon dioxide respectively, so that the gaseous carbon dioxide is gradually cooled in the first heat exchange component, liquid carbon dioxide is obtained, and is transported to the low-pressure liquid storage module 1 for storage through the third on-off valve 13.

Claims

1. A constant pressure carbon dioxide energy storage system, characterized in that: The system comprises a pressure stabilizing tank (9), a low-pressure liquid storage module (1), a first heat exchange component, a compression-expansion module, a second heat exchange component and a high-pressure liquid storage module (5); the compression-expansion module comprises a compressor (3) and an expander (7) connected in parallel; the low-pressure liquid storage module (1), the first heat exchange component, the compressor (3), the second heat exchange component and the high-pressure liquid storage module (5) form an energy storage passage; the high-pressure liquid storage module (5), the second heat exchange component, the expander (7), the first heat exchange component and the low-pressure liquid storage module (1) form an energy release passage; the pressure stabilizing tank (9) is connected to the low-pressure liquid storage module (1) via a first on-off valve (11); the pressure stabilizing tank (9) is connected to the high-pressure liquid storage module (5) via a second on-off valve (12); the pressure stabilizing tank (9) is connected to the second heat exchange component in the energy release passage; during operation, the energy storage system switches between an energy storage state and an energy release state; In the energy storage state, the first on-off valve (11) is opened and the second on-off valve (12) is closed; liquid carbon dioxide in the low-pressure liquid storage module (1) is input into the energy storage passage; the pressure regulating tank (9) transports gaseous carbon dioxide to the low-pressure liquid storage module (1) so that the internal pressure of the low-pressure liquid storage module (1) remains stable; In the energy release state, the second on-off valve (12) is opened and the first on-off valve (11) is closed; the liquid carbon dioxide in the high-pressure liquid storage module (5) is input into the energy release passage; part of the gaseous carbon dioxide generated by gasification in the second heat exchange component is charged into the pressure stabilizing tank (9) and the high-pressure liquid storage module (5), so that the internal pressure of the high-pressure liquid storage module (5) is kept stable; The energy storage passage is provided with a throttle valve (10); the throttle valve (10) is located between the low-pressure liquid storage module (1) and the first heat exchange component; in the energy storage state, the liquid carbon dioxide output by the low-pressure liquid storage module (1) has a reduced flow cross-sectional area when passing through the throttle valve (10), and is converted into gas-liquid two-phase carbon dioxide; The first heat exchange component includes one or multiple cold storage and release components connected in sequence; the second heat exchange component includes one or multiple heat storage and release components connected in sequence; The cold storage and release assembly and the heat storage and release assembly have the same structure, and both include a first heat exchanger, a heat storage tank, a second heat exchanger and a cold storage tank which are sequentially connected to form a circulation loop through a heat exchange medium pipeline; the first heat exchanger is connected in series in the energy storage path; the second heat exchanger is connected in series in the energy release path; In the cold storage and release component, the cold energy released by the gasification of carbon dioxide in the energy storage state is stored in the cold storage tank by means of heat exchange between the first heat exchanger and the heat exchange medium, and is supplied to the liquefied carbon dioxide in the energy release state by means of heat exchange between the second heat exchanger and the heat exchange medium; In the heat storage and heat release component, the heat released by the liquefaction of carbon dioxide in the energy storage state is stored in the heat storage tank by heat exchange between the second heat exchanger and the heat exchange medium, and is supplied to the gasified carbon dioxide in the energy release state by heat exchange between the first heat exchanger and the heat exchange medium.

2. A constant pressure carbon dioxide energy storage system according to claim 1, characterized in that: The energy release passage is provided with a third on-off valve (13); the third on-off valve (13) is located between the low-pressure liquid storage module (1) and the first heat exchange component.

3. A constant pressure carbon dioxide energy storage system according to claim 1, characterized in that: In the energy storage state, liquid carbon dioxide entering the energy storage passage is converted into gaseous carbon dioxide through the first heat exchange component, and the released cold energy is stored by the first heat exchange component; the compressor (3) increases the pressure of the gaseous carbon dioxide; the gaseous carbon dioxide is converted into liquid carbon dioxide in the second heat exchange component and input into the high-pressure liquid storage module (5), and the released heat energy is stored by the second heat exchange component; In the energy release state, the liquid carbon dioxide entering the energy release passage is converted into gaseous carbon dioxide through the second heat exchange component, and the released cold is stored by the second heat exchange component; the gaseous carbon dioxide expands in the expander (7) to release energy; the gaseous carbon dioxide is converted into liquid carbon dioxide in the first heat exchange component and input into the low-pressure liquid storage module (1), and the released heat is stored by the first heat exchange component.

4. A constant pressure carbon dioxide energy storage system according to claim 1, characterized in that: The first heat exchange component comprises a primary cold storage and release component and a secondary cold storage and release component, the primary cold storage and release component being connected to a low-pressure liquid storage module (1); the second heat exchange component comprises a primary heat storage and release component and a secondary heat storage and release component, the secondary heat storage and release component being connected to a high-pressure liquid storage module (5); carbon dioxide undergoes a phase change in the primary cold storage and release component and the secondary heat storage and release component.

5. A constant pressure carbon dioxide energy storage system, characterized in that: The system comprises a pressure stabilizing tank (9), a low-pressure liquid storage module (1), a first heat exchange component, a compression-expansion module, a second heat exchange component and a high-pressure liquid storage module (5); the compression-expansion module comprises a compressor (3) and an expander (7) connected in parallel; the low-pressure liquid storage module (1), the first heat exchange component, the compressor (3), the second heat exchange component and the high-pressure liquid storage module (5) form an energy storage passage; the high-pressure liquid storage module (5), the second heat exchange component, the expander (7), the first heat exchange component and the low-pressure liquid storage module (1) form an energy release passage; the pressure stabilizing tank (9) is connected to the low-pressure liquid storage module (1) via a first on-off valve (11); the pressure stabilizing tank (9) is connected to the high-pressure liquid storage module (5) via a second on-off valve (12); the pressure stabilizing tank (9) is connected to the second heat exchange component in the energy release passage; during operation, the energy storage system switches between an energy storage state and an energy release state; In the energy storage state, the first on-off valve (11) is opened and the second on-off valve (12) is closed; liquid carbon dioxide in the low-pressure liquid storage module (1) is input into the energy storage passage; the pressure regulating tank (9) transports gaseous carbon dioxide to the low-pressure liquid storage module (1) so that the internal pressure of the low-pressure liquid storage module (1) remains stable; In the energy release state, the second on-off valve (12) is opened and the first on-off valve (11) is closed; the liquid carbon dioxide in the high-pressure liquid storage module (5) is input into the energy release passage; part of the gaseous carbon dioxide generated by gasification in the second heat exchange component is charged into the pressure stabilizing tank (9) and the high-pressure liquid storage module (5), so that the internal pressure of the high-pressure liquid storage module (5) is kept stable; The energy storage passage is provided with a throttle valve (10); the throttle valve (10) is located between the low-pressure liquid storage module (1) and the first heat exchange component; in the energy storage state, the liquid carbon dioxide output by the low-pressure liquid storage module (1) has a reduced flow cross-sectional area when passing through the throttle valve (10), and is converted into gas-liquid two-phase carbon dioxide; The first heat exchange component includes one or multiple cold storage and release components connected in sequence; the second heat exchange component includes one or multiple heat storage and release components connected in sequence; The cold storage and release components and the thermal storage and release components both use a heat exchanger containing phase change materials; the energy storage path and the energy release path share the same pipeline in the cold storage and release components and the thermal storage and release components; in the cold storage and release components, the cold released by the gasification of carbon dioxide in the energy storage state is stored in the phase change material of the cold storage and release components, and is supplied to the liquefied carbon dioxide in the energy release state; in the thermal storage and release components, the heat released by the liquefaction of carbon dioxide in the energy storage state is stored in the phase change material of the thermal storage and release components, and is supplied to the gasified carbon dioxide in the energy release state.

6. A constant pressure carbon dioxide energy storage system according to claim 5, characterized in that: The input end and the output end of the compressor (3) are both provided with a fourth on-off valve (14) in an energy storage path; the input end and the output end of the expander (7) are both provided with a fifth on-off valve (15) in an energy release path; in the energy storage state, the fourth on-off valve (14) is opened and the fifth on-off valve (15) is closed; in the energy release state, the fourth on-off valve (14) is closed and the fifth on-off valve (15) is opened.

7. A constant pressure carbon dioxide energy storage system according to claim 5, characterized in that: The first heat exchange component is provided with a plurality of cold storage and release components; along the direction from the energy storage passage to the energy release passage, the phase change temperature of the phase change material in each cold storage and release component increases successively; each cold storage and release component absorbs the cold released by the gasification of carbon dioxide step by step in the energy storage state, and provides the cold required for liquefaction of carbon dioxide step by step in the energy release state; the second heat exchange component is provided with a heat storage and release component; along the direction from the energy storage passage to the energy release passage, the phase change temperature of the phase change material in each heat storage and release component decreases successively; each heat storage and release component absorbs the heat released by the liquefaction of carbon dioxide step by step in the energy storage state, and provides the heat required for gasification of carbon dioxide step by step in the energy release state.

8. A constant pressure carbon dioxide energy storage system according to claim 5, characterized in that: The energy release passage is provided with a third on-off valve (13); the third on-off valve (13) is located between the low-pressure liquid storage module (1) and the first heat exchange component.

9. A constant pressure carbon dioxide energy storage system according to claim 5, characterized in that: In the energy storage state, liquid carbon dioxide entering the energy storage passage is converted into gaseous carbon dioxide through the first heat exchange component, and the released cold energy is stored by the first heat exchange component; the compressor (3) increases the pressure of the gaseous carbon dioxide; the gaseous carbon dioxide is converted into liquid carbon dioxide in the second heat exchange component and input into the high-pressure liquid storage module (5), and the released heat energy is stored by the second heat exchange component; In the energy release state, the liquid carbon dioxide entering the energy release passage is converted into gaseous carbon dioxide through the second heat exchange component, and the released cold is stored by the second heat exchange component; the gaseous carbon dioxide expands in the expander (7) to release energy; the gaseous carbon dioxide is converted into liquid carbon dioxide in the first heat exchange component and input into the low-pressure liquid storage module (1), and the released heat is stored by the first heat exchange component.

10. A constant pressure carbon dioxide energy storage system according to claim 5, characterized in that: The first heat exchange component comprises a primary cold storage and release component and a secondary cold storage and release component, the primary cold storage and release component being connected to a low-pressure liquid storage module (1); the second heat exchange component comprises a primary heat storage and release component and a secondary heat storage and release component, the secondary heat storage and release component being connected to a high-pressure liquid storage module (5); carbon dioxide undergoes a phase change in the primary cold storage and release component and the secondary heat storage and release component.

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