Self-balancing refrigeration compression carbon dioxide energy storage system and operating method

Abstract

The application discloses a self-balancing refrigeration compressed carbon dioxide energy storage system and an operation method, and belongs to the field of compressed carbon dioxide energy storage. The system comprises three subsystems of carbon dioxide circulation, chilled water and heat medium water. The carbon dioxide circulation is provided with switchable compression branch and expansion branch and shares a heat exchanger. In the energy storage stage, the compressor compresses CO2, which is cooled and condensed by the heat exchanger and stored in a storage tank after being liquefied by a condenser. In the energy release stage, the liquid CO2 is pressurized to 2-3 times of the original pressure by a high-pressure liquid pump, is gasified by an evaporator, is heated by the heat exchanger, and is stored in a gas bin after multi-stage expansion work. The exhaust gas is stored in the gas bin after releasing cold by a cold energy recovery device. The chilled water system absorbs heat to liquefy CO2 for the condenser in the energy storage stage, and recovers the cold capacity of the exhaust gas in the energy release stage. The heat medium water system recovers the compression heat in the energy storage stage, and releases heat to heat the working medium in the energy release stage. The application matches parameters to adapt the energy storage and energy release working medium flow, realizes the cycle self-balancing, uses the expansion low-temperature exhaust gas to replace the external refrigeration machine to produce cold capacity, improves the power generation efficiency of the system, and reduces the equipment cost.

Description

Technical Field

[0001] This invention relates to the field of compressed carbon dioxide energy storage technology, and in particular to a self-balancing refrigeration compressed carbon dioxide energy storage system and its operation method. Background Technology

[0002] Compressed carbon dioxide (CCCO) energy storage, as an important component of new energy storage technologies, is an effective means to improve the regulation capacity of power systems and is currently in the commercialization and application stage. Existing technologies primarily employ liquefaction compression, typically using two stages to compress carbon dioxide to approximately 8 MPa, relying on a refrigeration mechanism to draw chilled water for cooling, thus achieving carbon dioxide liquefaction. During the expansion and power generation stage, the required heat comes from the compression heat stored during compression, while chilled water cools the compressor inlet temperature to approximately 30°C. Although this technology has achieved initial large-scale application, it still suffers from low system efficiency, complex refrigeration systems, and low cold energy utilization, hindering its further promotion.

[0003] With technological advancements, higher demands are being placed on the efficiency and cost of compressed carbon dioxide (CCCO) energy storage power plants. However, current technologies for liquefied carbon dioxide rely on refrigerants for cooling, limiting overall system efficiency, increasing chiller power consumption, and complicating system complexity, making it difficult to improve cold energy utilization efficiency. Specifically: system efficiency is difficult to further improve; high chiller power consumption increases plant power consumption; low cold energy utilization leads to energy waste; and the overall system complexity results in high equipment costs and a large footprint, keeping power plant costs high and limiting its wider commercial application.

[0004] Therefore, how to achieve efficient self-balancing of internal cooling capacity without relying on external refrigeration units, reduce refrigeration energy consumption, simplify system structure, and improve electro-electric conversion efficiency has become a technical problem that urgently needs to be solved in the cost field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a self-balancing refrigeration compression carbon dioxide energy storage system and its operation method. The system uses low-temperature gaseous carbon dioxide generated by the high expansion ratio of the low-pressure cylinder of the expander to produce cooling capacity, thereby achieving internal self-balancing of cooling capacity and replacing the traditional refrigeration machine. It aims to solve the problems of low system efficiency, high cooling energy consumption, poor cold energy utilization and high cost caused by the reliance on refrigeration machines in the existing technology, thereby improving power generation efficiency and reducing equipment costs.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A self-balancing refrigeration and compression carbon dioxide energy storage system includes: a carbon dioxide circulation system, a chilled water system, and a heat transfer medium water system; The carbon dioxide circulation system includes pipelines, valve groups, compressors, expanders, liquid carbon dioxide storage tanks, carbon dioxide gas chambers, heat exchangers, condensers, evaporators, cold energy recovery units, and high-pressure liquid pumps. The carbon dioxide circulation system forms selectively connected compression and expansion branches through valve group switching, and the two branches operate independently without interfering with each other. The flow path of the compression branch is: carbon dioxide gas chamber, compressor, heat exchanger, condenser, and liquid carbon dioxide storage tank. When the compression branch is running, the compressor pressurizes and heats the gaseous carbon dioxide output from the carbon dioxide gas chamber. The heated high-pressure gaseous carbon dioxide first releases the heat of compression through the heat exchanger, and then is sent to the condenser to complete the cooling and liquefaction. The final liquid carbon dioxide is stored inside the liquid carbon dioxide storage tank. The flow path of the expansion branch is as follows: liquid carbon dioxide storage tank, high-pressure liquid pump, evaporator, heat exchanger, expander, cold energy recovery unit, and carbon dioxide gas chamber. When the expansion branch is running, the high-pressure liquid pump pressurizes the liquid carbon dioxide in the liquid carbon dioxide storage tank to 2-3 times the normal inlet pressure of the expander. The pressurized liquid carbon dioxide is first vaporized into a high-pressure gaseous state by the evaporator, and then further heated by the heat exchanger before being sent to the high-pressure cylinder and low-pressure cylinder of the expander in sequence to expand and do work. The low-temperature gaseous carbon dioxide discharged from the low-pressure cylinder releases cold energy through the cold energy recovery unit and then flows back to the carbon dioxide gas chamber to complete the cycle. The chilled water system includes a low-temperature chilled water tank, a high-temperature chilled water tank, a chilled water pump set, and a matching valve set. The branch switching is achieved by switching the valve set. Under the compression energy storage condition, the water in the low-temperature chilled water tank is pumped into the condenser to absorb the energy released by the liquefaction of carbon dioxide. After being heated, it flows back to the high-temperature chilled water tank for storage. Under the expansion energy release condition, the water in the high-temperature chilled water tank is pumped into the cold energy recovery unit to absorb the low-temperature cold energy of the low-pressure cylinder exhaust. After being cooled, it flows back to the low-temperature chilled water tank for storage. The heat transfer water system includes a low-temperature heat transfer water tank, a high-temperature heat transfer water tank, a heat transfer water pump set, and a matching valve set. Branch switching is achieved by switching the valve set. Under compression and energy storage conditions, the water in the low-temperature heat transfer water tank is pumped into the heat exchanger to absorb the heat released by the carbon dioxide pressure. After being heated, the water is stored in the high-temperature heat transfer water tank. Under expansion and energy release conditions, the water in the high-temperature heat transfer water tank is pumped sequentially into the heat exchanger and evaporator to release heat, providing a stable heat source for carbon dioxide oxidation and heating. After releasing heat and cooling down, the water flows back to the low-temperature heat transfer water tank. The heat exchanger is shared in both the compression and expansion branches, and the system is designed with parameter matching to ensure that the volumetric flow rate of carbon dioxide on the compressor side under compression energy storage conditions is matched with the volumetric flow rate of carbon dioxide on the expander side under expansion energy release conditions, thereby achieving self-balancing of the system's working fluid circulation.

[0007] A further improvement of the technical solution of the present invention is that: three high-pressure liquid pumps are set up in a redundant configuration mode of two operating and one standby. When any one pump fails and stops, the standby pump can quickly switch to operation, ensuring the continuous and stable operation of the liquid carbon dioxide pressurization process in the expansion branch without the risk of supply interruption.

[0008] A further improvement of the technical solution of the present invention is that: in the expansion branch, the high-pressure liquid pump increases the inlet pressure of the expander to 2-3 times the conventional inlet pressure, and the exhaust temperature of the low-pressure cylinder of the expander is stably controlled in the range of -20℃ to -40℃ through pressure regulation; the cold energy recovery device is adapted to the range of -20℃ to -40℃, efficiently recovers the cold energy of carbon dioxide exhaust, and stores the cold energy in the chilled water system to realize the cold energy recovery and utilization.

[0009] A further improvement of the technical solution of the present invention is that: the heat exchanger includes a low-pressure energy storage heat exchanger and a high-pressure energy storage heat exchanger, and both heat exchangers are used simultaneously for compression energy storage and expansion energy release processes; the system achieves phase matching of carbon dioxide volume flow rate on the compression side and expansion side by precisely adjusting the inlet pressure parameters of the expander, thereby enhancing the self-balancing effect of the system.

[0010] A further improvement of the technical solution of the present invention is that the heat medium water system adopts a common main pipe design, the low temperature heat medium water supply pipe and the return water pipe share the same main pipe, and the high temperature heat medium water supply pipe and the return water pipe share another main pipe, which reduces the number of pipes laid, simplifies the pipe layout, and reduces pipe resistance and equipment costs.

[0011] A further improvement of the technical solution of the present invention is that the chilled water pump group includes multiple conventional working pumps and one shared standby pump. The shared standby pump can achieve branch adaptation through valve group switching. At the same time, it serves as a backup device for low-temperature chilled water pumps and high-temperature chilled water pumps. When any conventional working pump fails, the shared standby pump can be quickly switched through the valve group to immediately connect to the corresponding branch to replace the failed pump, ensuring the continuous and stable operation of the chilled water system.

[0012] A method for operating a self-balancing refrigeration and compression carbon dioxide energy storage system, wherein the system is set to compression energy storage mode and expansion energy release mode, and the two modes are switched by centralized switching through valve group. Only one mode is operated at the same time, and there is no mode overlap or interference. In the compression energy storage mode, the valve group switches to open the compression branch and close the expansion branch. Gaseous carbon dioxide is output from the carbon dioxide chamber, compressed and heated by the compressor, and then enters the heat exchanger to release the heat of compression. It is then sent to the condenser to be cooled and liquefied by low-temperature chilled water. All the generated liquid carbon dioxide is stored in a sealed liquid carbon dioxide storage tank. The chilled water system operates synchronously. Low-temperature chilled water is sent to the condenser to absorb the heat released by the liquefaction of carbon dioxide. After the water is heated, it flows back to the high-temperature chilled water tank for storage. The heat transfer water system operates synchronously. Low-temperature heat transfer water is sent to the heat exchanger to absorb the heat generated by the compression of carbon dioxide. After the water is heated, it is sent to the high-temperature heat transfer water tank for storage, thus completing the heat recovery of compression. In the expansion and energy release mode, the valve group switches to open the expansion branch and close the compression branch. The liquid carbon dioxide in the liquid carbon dioxide storage tank is pressurized by the high-pressure liquid pump to 2-3 times the normal inlet pressure of the expander. The pressurized carbon dioxide first enters the evaporator to absorb heat and vaporize into a high-pressure gas. Then, it further absorbs heat from the heat transfer medium water and is heated by the heat exchanger. Subsequently, it enters the high-pressure cylinder and low-pressure cylinder of the expander in sequence to expand and do work, realizing the output of electrical energy. The low-temperature carbon dioxide gas discharged from the low-pressure cylinder is sent to the cold energy recovery unit. After releasing the low-temperature cold energy, it flows back to the carbon dioxide gas chamber to complete the closed-loop circulation of the working fluid. The chilled water system operates simultaneously. The high-temperature chilled water is sent to the cold energy recovery unit to absorb the low-temperature cold energy. After the water is cooled down, it flows back to the low-temperature chilled water tank to store the cold energy. The heat transfer medium water system operates simultaneously. The high-temperature heat transfer medium water is sent to the heat exchanger and evaporator in sequence to release heat, providing stable heat support for the vaporization and heating of carbon dioxide. After releasing heat and cooling down, it flows back to the low-temperature heat transfer medium water tank. The compression energy storage mode and the expansion energy release mode share the same heat exchanger equipment. The system achieves a consistent carbon dioxide volume flow rate on the compressor side and the expander side through precise matching of pressure, flow rate and resistance parameters, thus realizing the triple self-balance of the system's working fluid cycle, heat cycle and cold energy cycle, ensuring the system's efficient and stable operation.

[0013] A further improvement of the technical solution of the present invention is that: in the expansion and energy release mode, the outlet pressure is precisely controlled by the high-pressure liquid pump, and the inlet pressure of the expander is stably increased to 2-3 times the conventional value, thereby precisely controlling the exhaust temperature of the low-pressure cylinder within the high-efficiency cold energy recovery range of -20℃ to -40℃, maximizing the cold energy recovery efficiency of the cold energy recovery unit, and the recovered cold energy is stably stored in the chilled water system for use in the subsequent carbon dioxide liquefaction process.

[0014] A further improvement of the technical solution of the present invention is that: during the entire operation of the system, the common standby pump of the chilled water pump group is in standby mode, and the operating parameters of each conventional working pump are monitored in real time; when the low temperature chilled water pump or the high temperature chilled water pump fails, stops, or experiences abnormal pressure drop, the valve group automatically and quickly switches to activate the common standby pump to replace the faulty pump and connect to the corresponding branch, thereby maintaining the flow and temperature stability of the chilled water system and achieving uninterrupted continuous operation.

[0015] A further improvement of the technical solution of the present invention is that: the water temperature in the low-temperature chilled water tank is controlled at 0℃-5℃ to meet the cooling requirements of carbon dioxide liquefaction in the condenser; the water temperature in the high-temperature chilled water tank is controlled at 30℃-35℃ to meet the low-temperature cold energy absorption requirements of the cold energy recovery unit. Through precise control of the temperature range, both cold energy recovery efficiency and liquefaction efficiency are taken into account.

[0016] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows: 1. This invention reduces the volumetric flow rate of carbon dioxide during the expansion and energy release process, thereby matching the volumetric flow rates of the expander and compressor. This allows the compression and expansion sides to share a single set of low-pressure and high-pressure energy storage heat exchangers. By utilizing the asynchronous operation of compression energy storage and expansion energy release, the total number of heat exchangers is reduced by half, the floor space is reduced by 40%, and the cost of heat exchangers is reduced by 30%.

[0017] 2. This invention increases the main gas pressure of the expander and simultaneously increases the flow capacity of the low-pressure cylinder, reducing the low-pressure exhaust temperature to the range of -20°C to -40°C. The cooling energy generated during the expansion stage is stored in the chilled water system via a cold energy recovery unit. No additional cooling source is required during the compression energy storage stage; the cooling energy required for liquefied carbon dioxide is provided by the stored chilled water. Using this system can reduce plant power consumption by 70-80% and lower the overall power plant cost by 15%.

[0018] 3. This invention uses a high-pressure liquid pump to pressurize liquid carbon dioxide, thereby enhancing the expander's work capacity. Under the same power generation conditions, it can reduce the main gas flow rate of the expander, the compressor flow rate, and the flow rates of related auxiliary equipment, resulting in a 5% reduction in the cost of the main unit and auxiliary equipment, and a 5%-10% increase in system efficiency.

[0019] 4. This invention uses one chilled water pump as a backup pump for both low-temperature and high-temperature chilled water pumps, thereby merging the backup pumps and reducing the number of backup pumps by one.

[0020] 5. In the heat transfer water system of the present invention, after the heat is released and cooled by the energy storage heat exchanger, it is further cooled by the evaporator to recover the carbon dioxide cooling capacity. There is no need to configure additional cooling water to cool the low temperature heat transfer water, which can reduce the amount of chilled water used by 50% and improve the system efficiency by 1%.

[0021] 6. This invention allows low-temperature heat medium water supply and return water to share the same main pipe through valve group switching, and high-temperature heat medium water supply and return water to share the same main pipe, reducing the length of heat medium water pipelines by 30% and reducing pipeline costs by 40%.

[0022] 7. The system provided by this invention is reliable in operation, easy to implement, and highly adaptable to different factory sites, making it suitable for promotion and application in various regions. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a flowchart of a self-balancing refrigeration and compression carbon dioxide energy storage system provided in an embodiment of the present invention; Among them, A is the low-pressure compressor; B is the high-pressure compressor; C is the low-pressure energy storage heat exchanger; D is the high-pressure energy storage heat exchanger; E is the condenser; F is the liquid carbon dioxide storage tank; G is the first high-pressure liquid pump; H is the second high-pressure liquid pump; I is the third high-pressure liquid pump; J is the evaporator; K is the low-pressure cylinder; L is the high-pressure cylinder; M is the cold energy recovery unit; N is the carbon dioxide gas chamber; O is the low-temperature chilled water tank; P is the high-temperature chilled water tank; Q is the high-temperature chilled water pump; R is the low-temperature chilled water pump; and S is the standby chilled water. Pump; T, Low-temperature heat transfer fluid tank; U, High-temperature heat transfer fluid tank; V, Low-temperature heat transfer fluid circulating pump; W, High-temperature heat transfer fluid circulating pump; 1, First shut-off valve; 2, Second shut-off valve; 3, Third shut-off valve; 4, Fourth shut-off valve; 5, Fifth shut-off valve; 6, Sixth shut-off valve; 7, First check valve; 8, Seventh shut-off valve; 9, Second check valve; 10, Eighth shut-off valve; 11, Third check valve; 12, Ninth shut-off valve; 13, Tenth shut-off valve; 14, Eleventh shut-off valve 15. Twelfth shut-off valve; 16. Thirteenth shut-off valve; 17. Fourteenth shut-off valve; 18. Fifteenth shut-off valve; 19. Sixteenth shut-off valve; 20. Seventeenth shut-off valve; 21. Eighteenth shut-off valve; 22. Nineteenth shut-off valve; 23. Twentieth shut-off valve; 24. Twenty-first shut-off valve; 25. Twenty-second shut-off valve; 26. Twenty-third shut-off valve; 27. Fourth check valve; 28. Twenty-fourth shut-off valve; 29. ​​Twenty-fifth shut-off valve; 30. Fifth check valve 31. Check valve; 32. Twenty-sixth shut-off valve; 33. Twenty-seventh shut-off valve; 34. Sixth check valve; 35. Twenty-eighth shut-off valve; 36. Twenty-ninth shut-off valve; 37. Seventh check valve; 38. Thirtieth shut-off valve; 39. Thirty-second shut-off valve; 40. Thirty-third shut-off valve; 41. Thirty-fourth shut-off valve; 42. Eighth check valve; 43. Thirty-fifth shut-off valve; 44. Thirty-sixth shut-off valve; 45. Thirty-seventh shut-off valve. Detailed Implementation

[0024] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product or device.

[0025] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments: like Figure 1 As shown, a self-balancing refrigeration and compression carbon dioxide energy storage system comprises three core subsystems: a carbon dioxide circulation system, a chilled water system, and a heat transfer medium water system. The components are connected in series or parallel via pipelines, shut-off valves, and check valves. Core equipment includes a compressor, expander, heat exchanger, storage tank, and pump body. The connection relationships between the components of each subsystem are as follows: (a) Carbon dioxide cycle system The core flow path is as follows: carbon dioxide gas chamber N → low-pressure compressor A → low-pressure energy storage heat exchanger C → high-pressure compressor B → high-pressure energy storage heat exchanger D → condenser E → liquid carbon dioxide storage tank F → high-pressure liquid pump (first high-pressure liquid pump G / second high-pressure liquid pump H / third high-pressure liquid pump I) → evaporator J → high-pressure cylinder L → low-pressure energy storage heat exchanger C → low-pressure cylinder K → cold energy recovery unit M → carbon dioxide gas chamber N.

[0028] (1) Compression energy storage section: The carbon dioxide gas chamber N passes through the 12th shut-off valve 15 → low-pressure compressor A → 14th shut-off valve 17 → low-pressure energy storage heat exchanger C → 16th shut-off valve 19 → high-pressure compressor B → 18th shut-off valve 21 → high-pressure energy storage heat exchanger D → 20th shut-off valve 23 → condenser E, and condenser E passes through the 22nd shut-off valve 25 → liquid carbon dioxide storage tank F.

[0029] (2) Expansion and energy release section: The liquid carbon dioxide storage tank F passes through the high-pressure liquid pump (first high-pressure liquid pump G / second high-pressure liquid pump H / third high-pressure liquid pump I) → evaporator J. The evaporator J passes through the twenty-first shut-off valve 24 → high-pressure energy storage heat exchanger D → nineteenth shut-off valve 22 → high-pressure cylinder L → seventeenth shut-off valve 20 → low-pressure energy storage heat exchanger C → fifteenth shut-off valve 18 → low-pressure cylinder K → cold energy recovery unit M → thirteenth shut-off valve 16 → carbon dioxide gas chamber N.

[0030] (3) Backup design: The three high-pressure liquid pumps (first high-pressure liquid pump G, second high-pressure liquid pump H, and third high-pressure liquid pump I) adopt the "two in operation and one standby" mode to ensure the continuous operation of the pressurization link.

[0031] The inlet side of the first high-pressure liquid pump G is equipped with a twenty-third shut-off valve 26, and the outlet side is equipped with a fourth check valve 27 and a twenty-fourth shut-off valve 28 connected in series.

[0032] The inlet side of the second high-pressure liquid pump H is equipped with a twenty-fifth shut-off valve 29, and the outlet side is equipped with a fifth check valve 30 and a twenty-sixth shut-off valve 31 connected in series.

[0033] The inlet side of the third high-pressure liquid pump I is equipped with a twenty-seventh shut-off valve 32, and the outlet side is equipped with a sixth check valve 33 and a twenty-eighth shut-off valve 34 connected in series. This system increases the pressure of liquid carbon dioxide to 2-3 times the inlet pressure by setting a first high-pressure liquid pump G, a second high-pressure liquid pump H, and a third high-pressure liquid pump I. This increases the main gas pressure of the expander (high-pressure cylinder L and low-pressure cylinder K). The expansion ratio of high-pressure cylinder L remains unchanged, while the expansion ratio of low-pressure cylinder K is increased, thereby reducing the low-pressure exhaust temperature of the expander to the range of -20℃ to -40℃.

[0034] (ii) Chilled water system The core thermal / cold storage equipment includes a low-temperature chilled water tank O and a high-temperature chilled water tank P; the pump body includes a high-temperature chilled water pump Q, a low-temperature chilled water pump R, and a standby chilled water pump S; The core heat exchange equipment consists of condenser E and cold energy recovery unit M.

[0035] The chilled water system achieves operating condition switching through check valves (first check valve 7, second check valve 9, third check valve 11) and shut-off valves (first shut-off valve 1, second shut-off valve 2, third shut-off valve 3, fourth shut-off valve 4, fifth shut-off valve 5, sixth shut-off valve 6, seventh shut-off valve 8, eighth shut-off valve 10, ninth shut-off valve 12, tenth shut-off valve 13, eleventh shut-off valve 14).

[0036] (1) Expansion and energy release stage (supplying liquid to cold energy recovery unit M) Path: High-temperature chilled water tank P → Second shut-off valve 2 → High-temperature chilled water pump Q → First check valve 7 → Seventh shut-off valve 8, entering the cold energy recovery unit M; Cold energy recovery unit M → Fourth shut-off valve 4 → Low-temperature chilled water tank O.

[0037] Function: To recover the cold energy from the exhaust of the low-pressure cylinder K and cool the high-temperature chilled water into low-temperature chilled water.

[0038] (2) Compression and energy storage stage (supplying liquid to condenser E): Path: Low-temperature chilled water tank O → Sixth shut-off valve 6 → Low-temperature chilled water pump R → Third check valve 11 → Ninth shut-off valve 12, entering condenser E; Condenser E → First shut-off valve 1 → High-temperature chilled water tank P.

[0039] Function: It uses low-temperature chilled water to cool and liquefy carbon dioxide, and then absorbs heat to become high-temperature chilled water.

[0040] (3) Backup flow path: The backup chilled water pump S serves as the backup pump for the entire system. Through valve group switching, it achieves full backup for the high-temperature chilled water pump Q and the low-temperature chilled water pump R. ① Replaces the low-temperature chilled water pump R (supplies liquid to condenser E): Valve operation: Close the sixth shut-off valve 6 and the ninth shut-off valve 12; open the fifth shut-off valve 5, the tenth shut-off valve 13, and the eighth shut-off valve 10; Start the standby chilled water pump S; Liquid supply path: Low-temperature chilled water tank O → Fifth shut-off valve 5 → Standby chilled water pump S → Second check valve 9 → Eighth shut-off valve 10 → Tenth shut-off valve 13 → Condenser E.

[0041] ② Replaces the high-temperature chilled water pump Q (supplying liquid to the cold energy recovery unit M): Close the second shut-off valve 2 and the seventh shut-off valve 8, and open the third shut-off valve 3, the eleventh shut-off valve 14, and the eighth shut-off valve 10. Start the standby chilled water pump S; the liquid supply path is: high temperature chilled water tank P → third shut-off valve 3 → standby chilled water pump S → second check valve 9 → eighth shut-off valve 10 → eleventh shut-off valve 14 → cold energy recovery unit M.

[0042] (4) Summary of system functions This chilled water system uses low-temperature water (0℃-5℃) to store the cold energy from the exhaust gas of the low-pressure cylinder K, and uses high-temperature water (30℃-35℃) to temporarily store the heat released during the compression stage, thus achieving the recycling of cold energy. Expansion and energy release: High-temperature chilled water is used to recover the cold energy from the exhaust of the low-pressure cylinder and cool it into low-temperature chilled water.

[0043] Compressed energy storage: Carbon dioxide is liquefied in condenser E using low-temperature chilled water to complete energy storage.

[0044] (III) Heat transfer water system Core thermal / cold storage equipment: Low-temperature heat transfer medium tank T and high-temperature heat transfer medium tank U; Pump bodies: Low-temperature heat medium water circulation pump V and high-temperature heat medium water circulation pump W; Core heat exchange equipment: low-pressure energy storage heat exchanger C, high-pressure energy storage heat exchanger D, and evaporator J.

[0045] Flow path control: Operating conditions are switched through check valves (seventh check valve 36, eighth check valve 42, fourth check valve 27, fifth check valve 30, sixth check valve 33) and various shut-off valves (twenty-second shut-off valve 25, twenty-third shut-off valve 26, twenty-fourth shut-off valve 28, twenty-fifth shut-off valve 29, twenty-sixth shut-off valve 31, twenty-seventh shut-off valve 32, twenty-eighth shut-off valve 34, twenty-ninth shut-off valve 35, thirtieth shut-off valve 37, thirty-first shut-off valve 38, thirty-second shut-off valve 39, thirty-third shut-off valve 40, thirty-fourth shut-off valve 41, thirty-fifth shut-off valve 43, thirty-sixth shut-off valve 44, thirty-seventh shut-off valve 45).

[0046] (1) Low-temperature heat medium water tank T (system low-temperature heat medium source) Low-temperature heat transfer water serves as the cold-end medium of the system, undertaking both liquid supply and reflux functions.

[0047] Compression energy storage stage (supplying liquid to low-pressure energy storage heat exchanger C and high-pressure energy storage heat exchanger D): Path: Low-temperature heat transfer medium water tank T → Thirty-seventh shut-off valve 45 → Low-temperature heat transfer medium water circulation pump V → Eighth check valve 42 → Thirty-fifth shut-off valve 43 → Thirty-fourth shut-off valve 41, sequentially entering low-pressure energy storage heat exchanger C and high-pressure energy storage heat exchanger D.

[0048] Function: Absorbs the heat released during the compression of carbon dioxide, raising the body temperature.

[0049] Expansion and energy release stage (receiving reflux from evaporator J): Path: Evaporator J → Thirty-second shut-off valve 39 → Thirty-sixth shut-off valve 44 → Low-temperature heat transfer medium tank T.

[0050] Function: To recover the low-temperature heat transfer medium water after the evaporator J releases heat, thus completing the cooling cycle.

[0051] (2) High-temperature heat medium water tank U (system high-temperature heat medium source) High-temperature heat transfer medium water, as the hot-end medium of the system, has both receiving and releasing functions: Compression energy storage stage (receiving reflux from low-pressure energy storage heat exchanger C and high-pressure energy storage heat exchanger D) Path: Low-pressure energy storage heat exchanger C, high-pressure energy storage heat exchanger D → Thirty-first shut-off valve 38 → High-temperature heat medium water tank U.

[0052] Function: Stores high-temperature heat transfer fluid that has absorbed the heat of carbon dioxide compression, preparing for the energy release phase.

[0053] Expansion and energy release stage (supplying liquid to low-pressure energy storage heat exchanger C, high-pressure energy storage heat exchanger D, and evaporator J) Path: High-temperature heat transfer fluid tank U → via 29th shut-off valve 35 → High-temperature heat transfer fluid circulation pump W → 7th check valve 36 → 30th shut-off valve 37 → Low-pressure energy storage heat exchanger C, high-pressure energy storage heat exchanger D → 33rd shut-off valve 40 → Evaporator J Function: First, carbon dioxide is preheated in the low-pressure energy storage heat exchanger C and the high-pressure energy storage heat exchanger D, and then enters the evaporator J to provide heat for the vaporization of liquid carbon dioxide. After cooling, it flows back to the low-temperature heat transfer medium water tank T.

[0054] (3) Heat exchange connection and system characteristics 1) Shared heat exchanger design: Low-pressure energy storage heat exchanger C and high-pressure energy storage heat exchanger D are shared compression / expansion devices.

[0055] Energy storage stage: Absorbs the heat of carbon dioxide compression to heat low-temperature heat transfer medium water; Energy release stage: Heat from high-temperature heat transfer medium water is released to preheat carbon dioxide.

[0056] 2) Evaporator J Function: It operates only during the expansion and energy release phase. As a dedicated heat exchange device for liquid carbon dioxide vaporization, it utilizes the cooled heat transfer medium water from the low-pressure energy storage heat exchanger C and the high-pressure energy storage heat exchanger D to provide the latent heat of vaporization.

[0057] 3) Traffic matching logic: By increasing the inlet pressure of the expander, the volumetric flow rate of the expander is made approximately equal to that of the compressor, thus achieving complete sharing of heat exchangers in the compression / expansion stages, simplifying the system structure and improving efficiency.

[0058] (4) Summary of system functions: The heat transfer water system uses low-temperature heat transfer water to absorb the heat of compression of carbon dioxide, and high-temperature heat transfer water to store the heat. In the energy release phase, the heat is then released back into the carbon dioxide, achieving efficient recovery and reuse of the heat of compression. Energy storage: Low-temperature heat transfer medium water → Low-pressure energy storage heat exchanger C / High-pressure energy storage heat exchanger D → Absorption of compression heat → High-temperature heat transfer medium water → High-temperature heat transfer medium water tank U for storage; Energy release: High-temperature heat transfer medium water → High-temperature heat transfer medium water tank U → High-temperature heat transfer medium water circulation pump W → Low-pressure energy storage heat exchanger C / High-pressure energy storage heat exchanger D → Evaporator J → Heat release → Low-temperature heat transfer medium water → Low-temperature heat transfer medium water tank T (circulation).

[0059] like Figure 1 As shown, a self-balancing refrigeration compression carbon dioxide energy storage system is operated in a way that includes a compression energy storage mode and an expansion energy release mode. The two modes are switched by a valve group and only one mode is operated at a time, with no mode overlap or interference. The core task of the compression energy storage mode is to compress and liquefy gaseous carbon dioxide and store it in liquid carbon dioxide storage tank F. At the same time, the heat energy generated during the compression process is recovered to the high-temperature heat transfer medium water tank U. The low-temperature chilled water of the chilled water system is used to liquefy carbon dioxide and release the cold energy as heat energy to be temporarily stored in the high-temperature chilled water tank P.

[0060] The core task of the expansion energy release mode is to pressurize and vaporize liquid carbon dioxide and send it to the expander (high-pressure cylinder L + low-pressure cylinder K) to do work. At the same time, the cold energy of the expander exhaust is recovered to the low-temperature chilled water tank O, and the heat energy of the high-temperature heat transfer medium water is used to complete the vaporization and heat exchange of carbon dioxide. Core parameter control: the exhaust temperature of the low-pressure cylinder of the expander is reduced to -20℃ to -40℃, and the low-temperature chilled water is maintained at 0℃ to 5℃.

[0061] The carbon dioxide circulation system, chilled water system, and heat transfer water system operate in sync.

[0062] Specifically, it includes: (1) When the carbon dioxide cycle system compresses and stores energy: Valve operation: Open the 12th shut-off valve 15, the 14th shut-off valve 17, the 16th shut-off valve 19, the 18th shut-off valve 21, the 20th shut-off valve 23 and the 22nd shut-off valve 25; close the 13th shut-off valve 16, the 15th shut-off valve 18, the 17th shut-off valve 20, the 19th shut-off valve 22 and the 21st shut-off valve 24.

[0063] Medium flow: Carbon dioxide flows out from carbon dioxide gas chamber N, and flows sequentially through the 12th shut-off valve 15 → low-pressure compressor A → 14th shut-off valve 17 → low-pressure energy storage heat exchanger C → 16th shut-off valve 19 → high-pressure compressor B → 18th shut-off valve 21 → high-pressure energy storage heat exchanger D → 20th shut-off valve 23, and enters condenser E.

[0064] In condenser E, high-temperature and high-pressure gaseous carbon dioxide is cooled by chilled water and liquefied into liquid carbon dioxide, which is then sent to liquid carbon dioxide storage tank F via the twenty-second shut-off valve 25.

[0065] (2) When the carbon dioxide cycle system expands and releases energy: Valve operation: Close the 12th shut-off valve 15, the 14th shut-off valve 17, the 16th shut-off valve 19, the 18th shut-off valve 21, the 20th shut-off valve 23, and the 22nd shut-off valve 25; open the 13th shut-off valve 16, the 15th shut-off valve 18, the 17th shut-off valve 20, the 19th shut-off valve 22, the 21st shut-off valve 24, the 23rd shut-off valve 26, the 24th shut-off valve 28, the 25th shut-off valve 29, the 26th shut-off valve 31, the 27th shut-off valve 32, and the 28th shut-off valve 34; Pump operation: Three high-pressure liquid pumps (first high-pressure liquid pump G, second high-pressure liquid pump H, and third high-pressure liquid pump I) operate in a "two-in operation and one-standby" mode.

[0066] Medium flow: Liquid carbon dioxide flows out from liquid carbon dioxide storage tank F, is pressurized by a high-pressure liquid pump, and then sent to evaporator J for vaporization. After being converted into gaseous carbon dioxide in evaporator J, it flows sequentially through: 21st shut-off valve 24 → high-pressure energy storage heat exchanger D → 19th shut-off valve 22 → high-pressure cylinder L performs work → 17th shut-off valve 20 → low-pressure energy storage heat exchanger C → 15th shut-off valve 18 → low-pressure cylinder K performs work → cold energy recovery unit M.

[0067] In the cold energy recovery unit M, the low-temperature, low-pressure carbon dioxide released after doing work releases cold energy, and finally passes through the thirteenth shut-off valve 16 and is sent to the carbon dioxide gas chamber N for storage.

[0068] (3) When compressing and storing energy in a chilled water system: Normal operating conditions: Valve operation: Open the sixth shut-off valve 6, the ninth shut-off valve 12, and the first shut-off valve 1; close the fifth shut-off valve 5 and the tenth shut-off valve 13 (closing these two valves cuts off the bypass from the standby chilled water pump S to the condenser E). Check valve status: The third check valve 11 automatically opens according to the direction of medium flow; Pump operation: Start the low-temperature chilled water pump R (main pump) to provide cooling water to the condenser E.

[0069] Medium flow: Low-temperature chilled water flows out from the low-temperature chilled water tank O, and flows sequentially through: sixth shut-off valve 6 → low-temperature chilled water pump R → third check valve 11 → ninth shut-off valve 12, and enters the condenser E.

[0070] In condenser E, low-temperature chilled water absorbs the latent heat of vaporization of carbon dioxide, its temperature rises, and it becomes high-temperature chilled water. Finally, it is sent to the high-temperature chilled water tank P for storage through the first shut-off valve 1.

[0071] Backup pump switching: When the low-temperature chilled water pump R fails, the standby chilled water pump S will take over operation: Close the sixth shut-off valve 6 and the ninth shut-off valve 12; open the fifth shut-off valve 5, the eighth shut-off valve 10, and the tenth shut-off valve 13; start the standby chilled water pump S.

[0072] Backup medium path: Low-temperature chilled water tank O → Fifth shut-off valve 5 → Backup chilled water pump S → Second check valve 9 → Eighth shut-off valve 10 → Tenth shut-off valve 13 → Condenser E.

[0073] (4) When the chilled water system expands and releases energy: Normal operating conditions: Valve operation: Open the second shut-off valve 2, the seventh shut-off valve 8, and the fourth shut-off valve 4; close the third shut-off valve 3 and the eleventh shut-off valve 14 (closing these two valves cuts off the bypass from the standby chilled water pump S to the cold energy recovery unit M). Check valve status: First check valve 7 automatically opens according to the direction of medium flow.

[0074] Pump operation: Start the high-temperature chilled water pump Q (main pump) to provide high-temperature chilled water to the cold energy recovery unit M.

[0075] Medium flow: High-temperature chilled water flows out from the high-temperature chilled water tank P, and flows sequentially through: second shut-off valve 2 → high-temperature chilled water pump Q → first check valve 7 → seventh shut-off valve 8, and enters the cold energy recovery unit M.

[0076] In the cold energy recovery unit M, the high-temperature chilled water absorbs the cold energy from the low-temperature exhaust gas of the expander, further reducing its temperature, and finally is sent back to the low-temperature chilled water tank O for storage via the fourth shut-off valve 4.

[0077] Standby chilled water pump switching: Standby chilled water pump S serves as a shared standby pump for both high-temperature chilled water pump Q and low-temperature chilled water pump R. The fault switching logic is as follows: ① Replaces the high-temperature chilled water pump Q (supplies liquid to the cold energy recovery unit M) When the high-temperature chilled water pump Q fails: close the second shut-off valve 2 and the seventh shut-off valve 8; open the third shut-off valve 3, the eighth shut-off valve 10, and the eleventh shut-off valve 14; start the standby chilled water pump S.

[0078] Backup medium path: High-temperature chilled water tank P → Third shut-off valve 3 → Backup chilled water pump S → Second check valve 9 → Eighth shut-off valve 10 → Eleventh shut-off valve 14 → Cold energy recovery unit M.

[0079] ② Replace the low-temperature chilled water pump R (supply liquid to condenser E) When the low-temperature chilled water pump R fails: close the sixth shut-off valve 6 and the ninth shut-off valve 12; open the fifth shut-off valve 5, the eighth shut-off valve 10, and the tenth shut-off valve 13; start the standby chilled water pump S.

[0080] Backup medium path: Low-temperature chilled water tank O → Fifth shut-off valve 5 → Backup chilled water pump S → Second check valve 9 → Eighth shut-off valve 10 → Tenth shut-off valve 13 → Condenser E.

[0081] (5) When compressing and storing energy in a heat transfer water system: Valve operation: Open the 37th shut-off valve 45, the 35th shut-off valve 43, the 34th shut-off valve 41, and the 31st shut-off valve 38; close the 36th shut-off valve 44, the 32nd shut-off valve 39, the 33rd shut-off valve 40, the 30th shut-off valve 37, and the 29th shut-off valve 35 (closing these five valves cuts off the supply path of high-temperature heat transfer medium water to the low-pressure energy storage heat exchanger C, the high-pressure energy storage heat exchanger D, and the evaporator J, and closes the return bypass). Check valve status: The eighth check valve 42 automatically opens according to the direction of medium flow.

[0082] Pump operation: Start the low-temperature heat medium water circulation pump V to provide low-temperature heat medium water to the low-pressure energy storage heat exchanger C and the high-pressure energy storage heat exchanger D.

[0083] Medium flow: Low-temperature heat transfer water flows out from the low-temperature heat transfer water tank T and flows sequentially through: the thirty-seventh shut-off valve 45 → the low-temperature heat transfer water circulation pump V → the eighth check valve 42 → the thirty-fifth shut-off valve 43 → the thirty-fourth shut-off valve 41, and enters the low-pressure energy storage heat exchanger C and the high-pressure energy storage heat exchanger D.

[0084] In the low-pressure energy storage heat exchanger C and the high-pressure energy storage heat exchanger D, the low-temperature heat transfer water absorbs the heat energy generated during the compression of carbon dioxide, and its temperature rises, becoming high-temperature heat transfer water. Finally, it is sent to the high-temperature heat transfer water tank U for storage through the thirty-first shut-off valve 38.

[0085] (6) When the thermal medium water system expands and releases energy: Valve operation: Open the 25th shut-off valve 29, the 30th shut-off valve 37, the 32nd shut-off valve 39, the 33rd shut-off valve 40, and the 36th shut-off valve 44; close the 31st shut-off valve 38, the 34th shut-off valve 41, the 35th shut-off valve 43, and the 37th shut-off valve 45 (closing these four valves cuts off the supply path of low-temperature heat transfer medium water to low-pressure energy storage heat exchanger C and high-pressure energy storage heat exchanger D, as well as the direct return bypass of high-temperature heat transfer medium water). Check valve status: The seventh check valve 36 automatically opens according to the direction of medium flow.

[0086] Pump operation: Start the high-temperature heat medium water circulation pump W to provide high-temperature heat medium water to the low-pressure energy storage heat exchanger C, the high-pressure energy storage heat exchanger D and the evaporator J.

[0087] Medium flow: High-temperature heat transfer water flows out from the high-temperature heat transfer water tank U, and flows sequentially through: the 25th shut-off valve 29 → the high-temperature heat transfer water circulation pump W → the 7th check valve 36 → the 30th shut-off valve 37, and enters the low-pressure energy storage heat exchanger C and the high-pressure energy storage heat exchanger D.

[0088] In the low-pressure heat exchanger C and the high-pressure heat exchanger D, the high-temperature heat transfer water releases heat energy to carbon dioxide, causing its temperature to decrease. The cooled heat transfer water then enters the evaporator J via the 33rd shut-off valve 40, continuing to provide heat for the vaporization of liquid carbon dioxide, further reducing its temperature and transforming it into low-temperature heat transfer water. Finally, the low-temperature heat transfer water is returned to the low-temperature heat transfer water tank T for storage via the 32nd shut-off valve 39 and then the 36th shut-off valve 44.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A self-balancing refrigeration and compression carbon dioxide energy storage system, characterized in that, include: The carbon dioxide circulation system includes a compression branch and an expansion branch that are selectively connected by valve group switching. In the compression branch, the compressor compresses gaseous carbon dioxide, cools it through a heat exchanger, liquefies it through a condenser, and stores it in a liquid carbon dioxide storage tank. In the expansion branch, the high-pressure liquid pump pressurizes the liquid carbon dioxide to 2-3 times the inlet pressure, vaporizes it through an evaporator, heats it through a heat exchanger, and then sequentially enters the high-pressure cylinder and low-pressure cylinder of the expander to do work. The exhaust from the low-pressure cylinder releases cold energy through a cold energy recovery unit and then enters the carbon dioxide gas chamber. The chilled water system includes a low-temperature chilled water tank, a high-temperature chilled water tank, and a chilled water pump group. Through valve switching, the low-temperature chilled water is sent to the condenser to absorb heat and liquefy carbon dioxide during compression energy storage, and the high-temperature chilled water is sent to the cold energy recovery unit to absorb the cold energy of the low-pressure cylinder exhaust during expansion energy release. The heat transfer water system includes a low-temperature heat transfer water tank, a high-temperature heat transfer water tank, and a heat transfer water pump group. Through valve group switching, the low-temperature heat transfer water is sent to the heat exchanger to absorb heat and store the heat of compression during compression and energy storage, and the high-temperature heat transfer water is sent to the heat exchanger to release heat to heat carbon dioxide during expansion and energy release, and then sent to the evaporator for further heat release before returning. The heat exchangers include a low-pressure energy storage heat exchanger and a high-pressure energy storage heat exchanger, both of which are used simultaneously for compression energy storage and expansion energy release processes; the compressor includes a low-pressure compressor and a high-pressure compressor, and the expander includes a high-pressure cylinder and a low-pressure cylinder; the system achieves self-balancing of the working fluid circulation by precisely adjusting the expander inlet pressure parameters to match the carbon dioxide volume flow rate on the compressor side under compression energy storage conditions with the carbon dioxide volume flow rate on the expander side under expansion energy release conditions. In the expansion branch, the high-pressure hydraulic pump increases the inlet pressure of the expander to 2-3 times the normal inlet pressure. Through pressure regulation, the exhaust temperature of the low-pressure cylinder of the expander is stably controlled in the range of -20℃ to -40℃. The cold energy recovery device is adapted to the range of -20℃ to -40℃, efficiently recovers the cold energy of carbon dioxide exhaust, and stores the cold energy in the chilled water system to realize the recovery and utilization of cold energy.

2. The self-balancing refrigeration and compression carbon dioxide energy storage system according to claim 1, characterized in that, Three high-pressure liquid pumps are installed in a redundant configuration with two operating and one standby. If any one pump fails and stops, the standby pump can quickly take over to ensure the continuous and stable operation of the liquid carbon dioxide pressurization process in the expansion branch, without the risk of supply interruption.

3. The self-balancing refrigeration and compression carbon dioxide energy storage system according to claim 1, characterized in that, The heat transfer water system adopts a shared main pipe design, with the low-temperature heat transfer water supply pipe and return water pipe sharing the same main pipe, and the high-temperature heat transfer water supply pipe and return water pipe sharing another main pipe.

4. The self-balancing refrigeration and compression carbon dioxide energy storage system according to claim 1, characterized in that, The chilled water pump set includes multiple conventional working pumps and one shared standby pump. The shared standby pump can be adapted to branch by switching valve groups. It also serves as a backup device for low-temperature chilled water pumps and high-temperature chilled water pumps. When any conventional working pump fails, the shared standby pump can be quickly switched through the valve group to immediately connect to the corresponding branch and replace the failed pump.

5. An operation method for a self-balancing refrigeration and compression carbon dioxide energy storage system, employing the self-balancing refrigeration and compression carbon dioxide energy storage system as described in any one of claims 1-4, characterized in that, The system is set to compression energy storage mode and expansion energy release mode. The two modes are switched by centralized valve group. Only one mode is running at a time, and there is no mode overlap or interference. In the compression energy storage mode, the valve group switches to open the compression branch and close the expansion branch. Gaseous carbon dioxide is output from the carbon dioxide chamber, compressed and heated by the compressor, and then enters the heat exchanger to release the heat of compression. It is then sent to the condenser to be cooled and liquefied by low-temperature chilled water. All the generated liquid carbon dioxide is stored in a sealed liquid carbon dioxide storage tank. The chilled water system operates synchronously. Low-temperature chilled water is sent to the condenser to absorb the heat released by the liquefaction of carbon dioxide. After the water is heated, it flows back to the high-temperature chilled water tank for storage. The heat transfer water system operates synchronously. Low-temperature heat transfer water is sent to the heat exchanger to absorb the heat generated by the compression of carbon dioxide. After the water is heated, it is sent to the high-temperature heat transfer water tank for storage, thus completing the heat recovery of compression. In the expansion and energy release mode, the valve group switches to open the expansion branch and close the compression branch. The liquid carbon dioxide in the liquid carbon dioxide storage tank is pressurized by the high-pressure liquid pump to 2-3 times the normal inlet pressure of the expander. The pressurized carbon dioxide first enters the evaporator to absorb heat and vaporize into a high-pressure gas. Then, it further absorbs heat from the heat transfer medium water and is heated by the heat exchanger. Subsequently, it enters the high-pressure cylinder and low-pressure cylinder of the expander in sequence to expand and do work, realizing the output of electrical energy. The low-temperature carbon dioxide gas discharged from the low-pressure cylinder is sent to the cold energy recovery unit. After releasing the low-temperature cold energy, it flows back to the carbon dioxide gas chamber to complete the closed-loop circulation of the working fluid. The chilled water system operates simultaneously. The high-temperature chilled water is sent to the cold energy recovery unit to absorb the low-temperature cold energy. After the water is cooled down, it flows back to the low-temperature chilled water tank to store the cold energy. The heat transfer medium water system operates simultaneously. The high-temperature heat transfer medium water is sent to the heat exchanger and evaporator in sequence to release heat, providing stable heat support for the vaporization and heating of carbon dioxide. After releasing heat and cooling down, it flows back to the low-temperature heat transfer medium water tank. The compression energy storage mode and the expansion energy release mode share the same heat exchanger equipment. The system achieves triple self-balance of working fluid circulation, heat circulation, and cold energy circulation by precisely matching pressure, flow rate, and resistance parameters to keep the carbon dioxide volume flow rate on the compressor side and the expander side consistent.

6. The operating method according to claim 5, characterized in that, Throughout the system's operation, the shared standby pump of the chilled water pump group is in standby mode, and the operating parameters of each conventional working pump are monitored in real time. When a low-temperature chilled water pump or a high-temperature chilled water pump fails, stops, or experiences abnormal pressure drop, the shared standby pump is automatically and quickly switched to replace the faulty pump and connect to the corresponding branch through the valve group.

7. The operating method according to claim 5, characterized in that, The water temperature in the low-temperature chilled water tank is controlled at 0℃-5℃ to meet the cooling requirements of the condenser for carbon dioxide liquefaction; the water temperature in the high-temperature chilled water tank is controlled at 30℃-35℃ to meet the low-temperature cold energy absorption requirements of the cold energy recovery unit.

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