Liquid compressed CO2 energy storage device based on LNG (Liquefied Natural Gas) cold energy utilization

Abstract

The invention provides a liquid compressed CO2 energy storage device based on LNG cold energy utilization, and relates to the technical field of CO2 energy storage, the liquid compressed CO2 energy storage device comprises a solid phase cold storage device, and liquid CO2 output by the solid phase cold storage device is input into a low-pressure liquid CO2 storage tank; a CO2 inlet of the cold energy utilization device is communicated with a CO2 outlet of the low-pressure liquid CO2 storage tank, and a CO2 outlet of the cold energy utilization device is communicated with a CO2 inlet of the solid phase cold storage device. The invention provides a novel energy storage system which is high in efficiency, high in system integration degree, safe and pollution-free, and waste heat and waste cold resources of a peripheral park of an energy storage power station are fully utilized.

Description

Technical Field

[0001] This invention relates to the field of CO2 energy storage technology, specifically to a liquid compressed CO2 energy storage device based on the utilization of LNG cold energy. Background Technology

[0002] Liquefied natural gas (LNG) is a crucial component of the energy supply system. In recent years, China's demand for natural gas has been increasing annually, and in 2021, it surpassed Japan to become the world's largest LNG importer. Due to the extremely low temperatures involved in LNG transportation and storage, it contains valuable cold energy. If this cold energy is not utilized during the LNG reheating and regasification process, it will be released into the environment, causing cold pollution and impacting the local ecosystem. China's development of LNG cold energy utilization technology started relatively late. Currently, the mainstream LNG cold energy utilization technologies in China mainly include air separation, liquid air storage, cold energy power generation, dry ice preparation, and refrigeration. However, liquid air storage and cold energy power generation technologies require a large amount of high-grade cold energy, making it impossible to fully utilize the remaining medium- and low-grade LNG cold energy. Although this portion of cold energy can usually meet the temperature requirements of dry ice preparation and refrigeration technologies, the large-scale application of these technologies is limited by local cooling demands. Therefore, the large-scale utilization of medium- and low-grade cold energy has become one of the most pressing issues to be addressed in the field of LNG cold energy utilization.

[0003] CO2 energy storage is a novel physical energy storage technology that uses CO2 as the working fluid in an energy storage system. It achieves efficient electricity storage through the interconversion of four different forms of energy: electrical energy, mechanical energy, thermal energy, and internal energy. There are several existing CO2 energy storage technologies, including CO2 Carnot batteries, CO2 Brayton cycle power generation coupled with molten salt thermal storage, and compressed CO2 energy storage technology. Compressed CO2 energy storage technology is similar to compressed air energy storage technology, but the difference lies in CO2's excellent thermal properties and critical temperature of only 30.98℃. It can achieve supercritical liquid storage under high pressure and normal temperature conditions. However, since CO2 cannot be directly obtained from the external environment like air, nor can it be directly emitted, CO2 needs to be reused as the system's working fluid. Traditional compressed CO2 energy storage schemes use airbags to store CO2 at normal pressure and temperature, resulting in huge land requirements for project construction. Liquid compressed CO2 energy storage technology stores low-pressure, low-temperature liquid CO2 on the low-pressure side. During the energy storage phase, the cold energy of CO2 is recovered using a cold accumulator, while the CO2 is reheated and vaporized during the energy release phase. The heat generated during the CO2 compression process is recovered using a heat storage medium. When the CO2 is compressed to the supercritical pressure, the supercritical CO2 gas flow is cooled down to below the critical temperature by a cooler and liquefied and stored in a high-pressure CO2 storage tank. During the energy release process, the high-pressure liquid CO2 fluid is reheated, vaporized, and superheated to a higher temperature by the heat stored in the energy storage phase. It then expands to the low-pressure side storage pressure through a CO2 turbine and is finally cooled and completely liquefied by a cold accumulator before returning to the low-pressure CO2 storage tank for storage, awaiting the next energy storage process.

[0004] Although liquid compressed CO2 energy storage technology solves the problem of excessive footprint of conventional compressed CO2 energy storage technology, liquid compressed CO2 energy storage systems require the placement of a cold accumulator on the low-pressure side to vaporize / liquefy CO2. The essence of the cold accumulator is to use an intermediate fluid to transfer the cold energy released during the low-pressure, low-temperature liquid CO2 vaporization process in the energy storage stage to the energy release stage for cooling the gaseous CO2 at the outlet of the liquefaction turbine. Since the driving force of the heat transfer process is the temperature difference, CO2 needs to pass through the gas-liquid two-phase region during the gas-liquid two-phase transition on the low-pressure side. The temperature of CO2 does not change during the condensation and evaporation processes in this region. Therefore, a low-temperature throttling valve needs to be placed before the cold accumulator in the energy storage stage to reduce the pressure of CO2 entering the cold accumulator in the energy storage stage and reduce the inlet liquid temperature, so as to form a temperature difference range of "CO2-cold storage medium-CO2" in the gas-liquid two-phase region, thereby realizing the storage / release of cold energy by the cold storage medium. The presence of a cryogenic throttling valve results in a pressure difference between the inlet compressor pressure during the CO2 energy storage stage and the outlet turbine pressure during the energy release stage. Therefore, the system efficiency of liquid compressed CO2 energy storage devices differs significantly from that of conventional compressed CO2 energy storage devices. To avoid excessive efficiency drops due to cryogenic throttling in liquid compressed CO2 energy storage devices, and considering the issue of dry ice formation below the triple point pressure (0.518 MPa), the low-pressure, low-temperature CO2 fluid is typically not throttled to an even lower pressure during the energy storage stage. This prevents the working fluid from storing cold energy at a large temperature difference, forcing it to recover / release cold energy only through a "small temperature difference, large flow rate" approach. This directly leads to a huge storage capacity of the working fluid in the cold storage unit of liquid compressed CO2 energy storage devices, hindering their large-scale deployment. Meanwhile, external environmental heat radiation, heat convection, and heat conduction from the civil engineering structure generate heat input to the cold storage medium tank. The operating temperature range of the cold storage medium is relatively small, and even a small temperature rise in the cold storage medium caused by the heat input can prevent CO2 from being completely liquefied during the energy release stage. Therefore, it is necessary to install an auxiliary compression refrigeration unit in the cold storage unit to supplement the CO2 liquefaction process with high-grade cold energy so that CO2 can be fully liquefied. This further reduces the efficiency of the energy storage device system. Summary of the Invention

[0005] The present invention provides a liquid compressed CO2 energy storage device based on LNG cold energy utilization, which solves at least one of the technical problems mentioned in the background art.

[0006] To address the aforementioned technical problems, this invention discloses a liquid compressed CO2 energy storage device based on LNG cold energy utilization, comprising: Solid-phase cold storage device, the liquid CO2 output from the solid-phase cold storage device is input into a low-pressure liquid CO2 storage tank; The cold energy utilization device has a CO2 inlet connected to the CO2 outlet of a low-pressure liquid CO2 storage tank, and a CO2 outlet connected to the CO2 inlet of a solid-phase cold storage device.

[0007] Preferably, the solid-phase cold storage device includes: The liquefied cold box heat exchanger has its CO2 outlet connected to the inlet of a low-pressure liquid CO2 storage tank, and its CO2 inlet connected to the CO2 outlet of the cold energy utilization device. The solid phase cold storage medium storage tank has its top connected to the air inlet of the induced draft fan and the air outlet of the blower, and its bottom connected to the air inlet of the liquefied cold box heat exchanger and the air outlet of the LNG heat exchanger.

[0008] Preferably, the cold energy utilization device includes: The system includes a first-stage turbine preheater, a first-stage CO2 turbine, a second-stage turbine preheater, and a second-stage CO2 turbine. The CO2 outlet of the second-stage CO2 turbine is connected to the CO2 inlet of the liquefied cold box heat exchanger 2. The CO2 inlet of the second-stage CO2 turbine is connected to the CO2 outlet of the second-stage turbine preheater. The CO2 inlet of the second-stage turbine preheater is connected to the CO2 outlet of the first-stage CO2 turbine. The CO2 inlet of the first-stage CO2 turbine is connected to the CO2 outlet of the first-stage turbine preheater. The CO2 inlet of the first-stage turbine preheater is connected to the outlet of the low-pressure liquid CO2 storage tank. The inlet of the ambient temperature water tank is connected to the outlet of the first-stage turbine preheater and the second-stage turbine preheater. The inlets of the first-stage turbine preheater and the second-stage turbine preheater are connected to the outlet of the high-temperature water tank.

[0009] Preferably, the CO2 inlet of the first-stage turbine preheater is directly connected to the outlet of the low-pressure liquid CO2 storage tank via a pipeline; the cold energy utilization device also includes: The preheater has its inlet connected to the outlet of the normal temperature water tank and its outlet connected to the inlet of the high temperature water tank.

[0010] Preferably, the cold energy utilization device further includes: The outlet of the rewarming cold box heat exchanger and the outlet of the low-pressure liquid CO2 storage tank are connected to the inlet of the rewarming cold box heat exchanger. The outlet of the rewarming cold box heat exchanger is connected to the CO2 inlet of the carbon dioxide compressor unit. The CO2 outlet of the carbon dioxide compressor unit is connected to the CO2 inlet of the subcooler. The CO2 outlet of the subcooler is connected to the inlet of the high-pressure liquid CO2 storage tank. The outlet of the high-pressure liquid CO2 storage tank is connected to the CO2 inlet of the first-stage CO2 turbine. The outlet of the carbon dioxide compressor unit is connected to the inlet of the high-temperature water tank.

[0011] Preferably, the carbon dioxide compressor unit includes: The system includes a medium-pressure CO2 compressor, a medium-pressure compressor-stage aftercooler, a high-pressure CO2 compressor, a high-pressure compressor-stage aftercooler, and a subcooler. The CO2 inlet of the medium-pressure CO2 compressor is connected to the CO2 outlet of the reheat cold box heat exchanger. The CO2 outlet of the medium-pressure CO2 compressor is connected to the CO2 inlet of the medium-pressure compressor-stage aftercooler. The CO2 outlet of the medium-pressure compressor-stage aftercooler is connected to the CO2 inlet of the high-pressure CO2 compressor. The CO2 outlet of the high-pressure CO2 compressor is connected to the CO2 inlet of the high-pressure compressor-stage aftercooler. The CO2 outlet of the high-pressure compressor-stage aftercooler is connected to the CO2 inlet of the subcooler. The CO2 outlet of the subcooler is connected to the CO2 inlet of the high-pressure liquid CO2 storage tank. The CO2 outlet of the high-pressure liquid CO2 storage tank is connected to the CO2 inlet of the first-stage turbine preheater. The outlets of the medium-pressure compressor stage aftercooler and the high-pressure compressor stage aftercooler are connected to the inlet of the high-temperature water tank.

[0012] Preferably, the outlet of the low-pressure liquid CO2 storage tank is connected to the inlet of the rewarming cold box heat exchanger via a cryogenic CO2 pump; Excess hot water from outside is fed into the high-temperature water tank; the outlet of the normal temperature water tank is also connected to the inlet of the reheating cold box heat exchanger, which outputs cooling water to the outside.

[0013] Preferably, the cold energy utilization device further includes: The preheater has its inlet connected to the CO2 outlet of the high-pressure liquid CO2 storage tank, and its CO2 inlet connected to the CO2 inlet of the first-stage turbine preheater.

[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a cold storage device to recover cold energy from LNG receiving stations near the energy storage power station or from upstream LNG, leveraging the user's surplus low-quality cold energy to cool the carbon dioxide after liquefaction and energy release. This eliminates the need for large-scale cold storage media in the original liquid compressed carbon dioxide energy storage scheme, and removes the low-temperature throttling valve required to increase the heat exchange temperature difference of the cold storage device. This significantly improves the electro-electric conversion efficiency of the energy storage device, increasing the revenue of the energy storage power station. Because a large amount of low-quality heat is difficult to recover after carbon dioxide compression in the original scheme due to the special physical properties near the carbon dioxide critical temperature, it needs to be discharged to the outside via cooling water. This heat can be used to heat the low-pressure liquid carbon dioxide. Furthermore, the first solution proposed in this invention can utilize low-quality waste heat from surrounding factories, improving the efficiency of the heat storage section and thus enhancing the overall system efficiency.

[0016] The second scheme proposed in this invention is based on the existence of a large number of available medium- and high-quality heat sources (industrial waste heat, geothermal energy, or steam extraction from thermal power units during periods of negative electricity prices) in the vicinity of Scheme 1. That is, the energy storage system does not need to prepare more heat for the carbon dioxide expansion power generation process in the energy release stage during the energy storage stage. At this time, the working fluid pump can be used to pressurize the low-pressure carbon dioxide once to replace the low-pressure carbon dioxide compressor in Scheme 1, which greatly reduces the power consumption in the energy storage stage and improves the efficiency of the energy storage device system.

[0017] The third scheme proposed in this invention is the extreme case of the second scheme. When there is a sufficient amount of external heat source, the low, medium and high CO2 compressors in the first scheme can be eliminated. The low-pressure carbon dioxide is pumped to high pressure by a low-temperature CO2 pump. In order to reduce the system investment cost, this device does not need to be equipped with the high-pressure liquid CO2 storage tank of the other schemes mentioned above. The device is turned on in the energy release stage. At this time, the liquid compressed carbon dioxide energy storage device becomes a carbon dioxide Rankine cycle power generation device with LNG as cold trap and external waste heat as heat source.

[0018] This invention primarily utilizes the residual low-to-medium grade cold energy from LNG cold energy utilization at the user side to improve the efficiency of liquid compressed CO2 energy storage systems. Based on the varying quantity and quality of waste heat resources surrounding the energy storage power station, three different liquid compressed CO2 energy storage system schemes coupled with LNG cold energy utilization are proposed. Compared to existing schemes, the new schemes significantly improve system efficiency, reduce the number of devices, increase system integration, decrease plant footprint, and enhance system economic performance. Furthermore, the residual low-to-medium grade cold energy from LNG cold energy utilization is difficult to fully utilize when local cooling demand is saturated. LNG receiving terminals typically require natural gas return pipeline temperatures above 0°C, meaning users need to expend resources to process this waste cold. The new liquid compressed CO2 energy storage scheme not only achieves a high-efficiency, highly integrated, safe, and pollution-free energy storage system but also fully utilizes the waste heat and cold resources in the surrounding area of ​​the energy storage power station. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is an overall schematic diagram of Scheme 1 of the present invention; Figure 2 This is an overall schematic diagram of Scheme 2 of the present invention; Figure 3 This is a schematic diagram of the overall structure of Scheme 3 of the present invention.

[0020] In the diagram: 1. Low-pressure liquid CO2 storage tank; 3. Reheating cold box heat exchanger; 4. Low-pressure CO2 compressor; 5. Low-pressure compressor stage aftercooler; 6. Medium-pressure CO2 compressor; 7. Medium-pressure compressor stage aftercooler; 8. High-pressure CO2 compressor; 9. High-pressure compressor stage aftercooler; 10. Subcooler; 11. High-pressure liquid CO2 storage tank; 12. Ambient temperature water tank; 13. First-stage turbine preheater; 14. First-stage CO2 turbine; 15. Second-stage turbine preheater; 16. Second-stage CO2 turbine; 17. High-temperature water tank; 18. Solid-phase cold storage medium storage tank; 19. Exhaust fan; 20. Blower; 21. Liquefied cold box heat exchanger; 22. LNG heat exchanger; 23. Preheater; 24. Cryogenic CO2 pump. Detailed Implementation

[0021] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0022] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] The present invention provides the following embodiments: This invention provides a liquid compressed CO2 energy storage device based on LNG cold energy utilization, such as... Figures 1-3 As shown, it includes: Solid-phase cold storage device, the liquid CO2 output from the solid-phase cold storage device is input into low-pressure liquid CO2 storage tank 1; The cold energy utilization device has a CO2 inlet connected to the CO2 outlet of a low-pressure liquid CO2 storage tank 1, and a CO2 outlet connected to the CO2 inlet of a solid-phase cold storage device.

[0024] Preferably, the solid-phase cold storage device includes: The liquefied cold box heat exchanger 21 has its CO2 outlet connected to the inlet of the low-pressure liquid CO2 storage tank 1, and its CO2 inlet connected to the CO2 outlet of the cold energy utilization device. The solid phase cold storage medium storage tank 18 has its top connected to the air inlet of the induced draft fan 19 and the air outlet of the blower 20, respectively, and its bottom connected to the air inlet of the liquefied cold box heat exchanger 21 and the air outlet of the LNG heat exchanger 22.

[0025] This means that the temperature distribution of the cold storage medium inside the solid phase cold storage tank is that the temperature is high at the top and low at the bottom.

[0026] During the energy storage and resting phases, the cold storage medium does not need to cool CO2. The top of the solid-phase cold storage medium tank is connected to the air inlet of the induced draft fan, and the bottom is connected to the air outlet of the LNG heat exchanger. After the induced draft fan starts working, the internal nitrogen gas flow is heated by the high-temperature cold storage solid at the top of the tank and then enters the air inlet of the LNG heat exchanger to heat the LNG or cold medium. At the same time, the gas flow recovers the cold energy of the LNG or cold medium. The air enters from the bottom of the solid-phase cold storage medium tank and cools the cold storage solid in the tank from bottom to top. During the process, the gas flow is heated again, thus forming a cycle.

[0027] During the energy release phase, the cold storage device needs to cool CO2 to liquefy it. The top of the solid cold storage medium tank is connected to the air outlet of the blower, and the bottom is connected to the air inlet of the liquefaction cold box heat exchanger. At this time, the airflow is heated by CO2 from the CO2 turbine outlet in the liquefaction cold box heat exchanger. The airflow enters from the top of the tank and heats the cold storage solid in the cold storage medium tank from top to bottom. After the airflow exits from the bottom of the tank, the airflow has been cooled to a lower temperature by the cold storage medium in the tank. The airflow re-enters the liquefaction cold box heat exchanger to cool CO2 to liquefy it. During the process, the airflow is heated, thus forming a cycle.

[0028] Preferably, the LNG cold energy input to the LNG heat exchanger 22 comes from the medium-to-low grade cold energy output from the LNG cold energy utilization device; the LNG cold energy is then transported to the LNG cold energy utilization device after being rehumidified by the LNG heat exchanger 22.

[0029] This invention relates to a cold energy utilization device, and there are three schemes. The common feature of the three schemes is: Cold energy utilization devices include: The system includes a first-stage turbine preheater 13, a first-stage CO2 turbine 14, a second-stage turbine preheater 15, and a second-stage CO2 turbine 16. The CO2 outlet of the second-stage CO2 turbine 16 is connected to the CO2 inlet of the liquefied cold box heat exchanger 21. The CO2 inlet of the second-stage CO2 turbine 16 is connected to the CO2 outlet of the second-stage turbine preheater 15. The CO2 inlet of the second-stage turbine preheater 15 is connected to the CO2 outlet of the first-stage CO2 turbine 14. The CO2 inlet of the first-stage CO2 turbine 14 is connected to the CO2 outlet of the first-stage turbine preheater 13. The CO2 inlet of the first-stage turbine preheater 13 is connected to the outlet of the low-pressure liquid CO2 storage tank 1. Ambient temperature water tank 12, the inlet of ambient temperature water tank 12 is connected to the outlet of the first turbine stage preheater 13 and the second turbine stage preheater 15, and the inlet of the first turbine stage preheater 13 and the second turbine stage preheater 15 is connected to the outlet of high temperature water tank 17. Option 3 (e.g.) Figure 3 In addition to the common features mentioned above, the device also includes: the CO2 inlet of the first-stage turbine preheater 13 is directly connected to the outlet of the low-pressure liquid CO2 storage tank 1 via a pipeline; the cold energy utilization device also includes: The preheater 23 has its inlet connected to the outlet of the normal temperature water tank 12, and its outlet connected to the inlet of the high temperature water tank 17.

[0030] Option 2 (e.g.) Figure 2 In addition to the common features mentioned above, cold energy utilization devices also include: The outlet of the rewarming cold box heat exchanger 3 and the low-pressure liquid CO2 storage tank 1 are connected to the inlet of the rewarming cold box heat exchanger 3. The outlet of the rewarming cold box heat exchanger 3 is connected to the CO2 inlet of the carbon dioxide compressor unit. The CO2 outlet of the carbon dioxide compressor unit is connected to the CO2 inlet of the supercooler 10. The CO2 outlet of the supercooler 10 is connected to the inlet of the high-pressure liquid CO2 storage tank 11. The outlet of the high-pressure liquid CO2 storage tank 11 is connected to the CO2 inlet of the first-stage CO2 turbine 14. The outlet of the carbon dioxide compressor unit is connected to the inlet of the high-temperature water tank 17.

[0031] The carbon dioxide compressor unit includes: The system includes a medium-pressure CO2 compressor 6, a medium-pressure compressor stage aftercooler 7, a high-pressure CO2 compressor 8, a high-pressure compressor stage aftercooler 9, and a subcooler 10. The CO2 inlet of the medium-pressure CO2 compressor 6 is connected to the CO2 outlet of the reheating cold box heat exchanger 3. The CO2 outlet of the medium-pressure CO2 compressor 6 is connected to the CO2 inlet of the medium-pressure compressor stage aftercooler 7. The CO2 outlet of the medium-pressure compressor stage aftercooler 7 is connected to the CO2 inlet of the high-pressure CO2 compressor 8. The CO2 outlet of the high-pressure CO2 compressor 8 is connected to the CO2 inlet of the high-pressure compressor stage aftercooler 9. The CO2 outlet of the high-pressure compressor stage aftercooler 9 is connected to the CO2 inlet of the subcooler 10. The CO2 outlet of the subcooler 10 is connected to the CO2 inlet of the high-pressure liquid CO2 storage tank 11. The CO2 outlet of the high-pressure liquid CO2 storage tank 11 is connected to the CO2 inlet of the first-stage turbine preheater 13. The outlets of the medium-pressure compressor stage aftercooler 7 and the high-pressure compressor stage aftercooler 9 are connected to the inlet of the high-temperature water tank 17. The cold energy utilization device also includes: The preheater 23 has its inlet connected to the CO2 outlet of the high-pressure liquid CO2 storage tank 11, and its CO2 inlet connected to the CO2 inlet of the first-stage turbine preheater 13.

[0032] Option 1 (e.g.) Figure 1 In addition to the common features mentioned above, cold energy utilization devices also include: The outlet of the rewarming cold box heat exchanger 3 and the low-pressure liquid CO2 storage tank 1 are connected to the inlet of the rewarming cold box heat exchanger 3. The outlet of the rewarming cold box heat exchanger 3 is connected to the CO2 inlet of the carbon dioxide compressor unit. The CO2 outlet of the carbon dioxide compressor unit is connected to the CO2 inlet of the supercooler 10. The CO2 outlet of the supercooler 10 is connected to the inlet of the high-pressure liquid CO2 storage tank 11. The outlet of the high-pressure liquid CO2 storage tank 11 is connected to the CO2 inlet of the first-stage CO2 turbine 14. The outlet of the carbon dioxide compressor unit is connected to the inlet of the high-temperature water tank 17.

[0033] The carbon dioxide compressor unit includes: The system includes a medium-pressure CO2 compressor 6, a medium-pressure compressor stage aftercooler 7, a high-pressure CO2 compressor 8, a high-pressure compressor stage aftercooler 9, and a subcooler 10. The CO2 inlet of the medium-pressure CO2 compressor 6 is connected to the CO2 outlet of the reheating cold box heat exchanger 3. The CO2 outlet of the medium-pressure CO2 compressor 6 is connected to the CO2 inlet of the medium-pressure compressor stage aftercooler 7. The CO2 outlet of the medium-pressure compressor stage aftercooler 7 is connected to the CO2 inlet of the high-pressure CO2 compressor 8. The CO2 outlet of the high-pressure CO2 compressor 8 is connected to the CO2 inlet of the high-pressure compressor stage aftercooler 9. The CO2 outlet of the high-pressure compressor stage aftercooler 9 is connected to the CO2 inlet of the subcooler 10. The CO2 outlet of the subcooler 10 is connected to the CO2 inlet of the high-pressure liquid CO2 storage tank 11. The CO2 outlet of the high-pressure liquid CO2 storage tank 11 is connected to the CO2 inlet of the first-stage turbine preheater 13. The outlets of the medium-pressure compressor stage aftercooler 7 and the high-pressure compressor stage aftercooler 9 are connected to the inlet of the high-temperature water tank 17. The outlet of the low-pressure liquid CO2 storage tank 1 is connected to the inlet of the rewarming cold box heat exchanger 3 via a cryogenic CO2 pump 24.

[0034] Hot water from outside is fed into high-temperature water tank 17; the outlet of normal temperature water tank 12 is also connected to the inlet of reheating cold box heat exchanger 3, and the reheating cold box heat exchanger 3 outputs cooling water to the outside.

[0035] Due to the low system efficiency of liquid compressed CO2 energy storage devices, and the difficulty in effectively utilizing the large amount of medium and low grade LNG cold energy in large-scale LNG cold energy utilization scenarios, this invention proposes a liquid compressed CO2 energy storage device coupled with LNG cold energy utilization, as well as several improvement schemes, to solve the above problems.

[0036] A basic liquid compressed CO2 energy storage system (hereinafter referred to as the basic scheme) generally consists of a low-pressure / high-pressure liquid CO2 storage tank, a cold storage device, a heat storage device, a CO2 compressor, a CO2 turbine, a cryogenic throttling valve, a compression refrigeration unit, and auxiliary pipelines, instruments, valves, and other components.

[0037] CO2 has a low critical temperature. If cooling water is used to subcool high-pressure CO2 below the critical temperature, the cooling water, heated during the energy storage phase, will struggle to heat the high-pressure liquid CO2 to a higher temperature during the energy release phase due to the heat transfer temperature difference in the heat exchanger. This heat is difficult to recover. Furthermore, the low-pressure side storage pressure of the liquid CO2 needs to be kept stable, and the cryogenic medium requires a heat transfer temperature difference to store / release CO2 cooling capacity. Therefore, the inlet pressure of CO2 entering the compressor during the energy storage phase and the turbine outlet pressure during the expansion phase cannot be synchronized. These unfavorable conditions all lead to a reduction in the system efficiency of the basic scheme.

[0038] The present invention proposes a novel liquid compressed CO2 energy storage device scheme one (hereinafter referred to as novel scheme one), see Figure 1 As shown, a solid-phase cold storage device is deployed to recover the cold energy of LNG and utilize the residual low-grade cold energy of the user's LNG to cool and liquefy the CO2 turbine exhaust during the energy release process. During the energy storage process, low-grade hot water generated in the subcooler is used to heat the low-pressure, low-temperature CO2 for rewarming and vaporization. This decouples the cold storage unit of the liquid compressed CO2 energy storage system from the energy storage and energy release stages. During the energy storage stage, the low-pressure CO2 does not need to be throttled to supplement the cold storage device with cooling capacity. During the energy release stage, no additional compression refrigeration unit is needed to cool the turbine exhaust. During the quiescent stage, the low-pressure CO2 can obtain more subcooling to cope with the temperature rise of CO2 in the storage tank caused by external heat input. Simultaneously, the high-pressure CO2 in the energy storage stage needs to be subcooled and liquefied by cooling water. The new scheme utilizes this heat for rewarming and vaporizing the low-pressure liquid CO2 in the energy storage stage to reduce environmental heat input and improve the heat quality of the storage unit. Therefore, by utilizing external low-grade cold energy, the liquid compressed CO2 energy storage system achieves significantly improved system efficiency compared to the basic solution, and the working fluid consumption of the cold storage unit is greatly reduced, which is conducive to improving system integration and reducing investment costs.

[0039] If there is available low-grade waste heat around the energy storage power station, this waste heat can be used to preheat high-pressure liquid CO2 and convert it into supercritical gas, reducing the consumption of high-quality hot water stored in the energy storage process during preheating, increasing the turbine inlet temperature, and thus improving the system's power generation and system efficiency.

[0040] Considering that LNG receiving terminals are generally built in port areas with developed coastal manufacturing and chemical industries, there may be potential waste heat resources available for utilization within the industrial park. When a certain quantity and quality of external heat sources are available, to further improve the efficiency of the liquid compressed CO2 energy storage system, a cryogenic CO2 pump is added as a primary pressurization device, and the CO2 compressor as a secondary pressurization device. This also reduces the number of compressor stages, thereby reducing CO2 compression work and heat output. The proposed novel liquid compressed CO2 energy storage device scheme two (hereinafter referred to as novel scheme two) is shown in the attached figure. Figure 2 As shown, waste water converted from an external heat source is used to supplement the energy release stage, fully heating the high-pressure CO2 to cause it to expand and do work, significantly improving the energy storage system's work capacity and further enhancing system efficiency.

[0041] When there are sufficient external heat sources, the high-pressure liquid CO2 storage tank can be eliminated. The head of the cryogenic CO2 pump can be increased to enhance the working potential of the working fluid. External heat sources can be used to heat high-pressure water to a higher temperature, and this high-pressure, high-temperature water can then heat the CO2 gas at each inlet of the turbine, increasing the system's power generation. The novel liquid compressed CO2 energy storage device scheme three (hereinafter referred to as novel scheme three) proposed in this invention is shown in the attached figure. Figure 3 As shown in Figure 4, since the energy storage system no longer has an energy storage process, the liquid compressed CO2 energy storage system becomes an intermittently operating LNG cold energy power generation device that uses low-grade LNG cold energy as a cold trap, an external heat source as a heat source, and CO2 as a circulating working fluid.

[0042] 1. The novel liquid compressed CO2 energy storage schemes proposed in this invention are 1, 2, and 3 (see attached figures). Figure 1 Attached Figure Figure 1 Attached Figure Figure 1 The system utilizes the residual low-to-medium grade cold energy of LNG to cool and liquefy the CO2 at the turbine outlet during the energy release stage. This significantly reduces the amount of cold storage medium used in the original cold storage unit. At the same time, the CO2 pressure at the compressor inlet and turbine outlet is restored to the same level, reducing compression power consumption and improving system efficiency.

[0043] 2. The second novel liquid compressed CO2 energy storage scheme proposed in this invention (see attached figure) Figure 2 Depending on the quality and quantity of waste heat resources available around the energy storage power station, the system can utilize a low-temperature CO2 pump and a CO2 compressor for staged pressurization, thereby reducing the power consumption of the CO2 compressor during the pressurization process and improving system efficiency.

[0044] 3. The third novel liquid compressed CO2 energy storage scheme proposed in this invention (see attached figure) Figure 3 As the extreme case of Scheme 2, it can generate electricity as an independent cold energy power generation process.

[0045] The beneficial effects of the above technical solution are as follows: This invention utilizes a cold energy storage device to recover cold energy from LNG receiving stations near the energy storage power station or from upstream LNG, and leverages the user's surplus low-quality cold energy to cool the carbon dioxide after liquefaction and energy release. This eliminates the need for large-scale cold energy storage media in the original liquid compressed carbon dioxide energy storage scheme, and removes the low-temperature throttling valve required to increase the heat exchange temperature difference of the cold energy storage device. This significantly improves the electro-to-electrical conversion efficiency of the energy storage device, increasing the revenue of the energy storage power station. Because a large amount of low-quality heat is difficult to recover after carbon dioxide compression in the original scheme due to the special properties of carbon dioxide's critical point, it needs to be discharged to the outside via cooling water. This heat can be used to heat the low-pressure liquid carbon dioxide. Furthermore, the first solution proposed in this invention can utilize low-quality waste heat from surrounding factories, improving the efficiency of the heat storage section and thus enhancing the overall system efficiency.

[0046] The second scheme proposed in this invention is based on the existence of a large number of available medium- and high-quality heat sources (industrial waste heat, geothermal energy, or steam extraction from thermal power units during periods of negative electricity prices) in the vicinity of Scheme 1. That is, the energy storage system does not need to prepare more heat for the carbon dioxide expansion power generation process in the energy release stage during the energy storage stage. At this time, the working fluid pump can be used to pressurize the low-pressure carbon dioxide once to replace the low-pressure carbon dioxide compressor in Scheme 1, which greatly reduces the power consumption in the energy storage stage and improves the efficiency of the energy storage device system.

[0047] The third scheme proposed in this invention is the extreme case of the second scheme. When there is a sufficient amount of external heat source, the low, medium and high CO2 compressors in the first scheme can be eliminated. The low-pressure carbon dioxide is pumped to high pressure by a low-temperature CO2 pump. In order to reduce the system investment cost, this device does not need to be equipped with the high-pressure liquid CO2 storage tank of the other schemes mentioned above. The device is turned on in the energy release stage. At this time, the liquid compressed carbon dioxide energy storage device becomes a carbon dioxide Rankine cycle power generation device with LNG as cold trap and external waste heat as heat source.

[0048] This invention primarily utilizes the residual low-to-medium grade cold energy from LNG cold energy utilization at the user side to improve the efficiency of liquid compressed CO2 energy storage systems. Based on the varying quantity and quality of waste heat resources surrounding the energy storage power station, three different liquid compressed CO2 energy storage system schemes coupled with LNG cold energy utilization are proposed. Compared to existing schemes, the new schemes significantly improve system efficiency, reduce the number of devices, increase system integration, decrease plant footprint, and enhance system economic performance. Furthermore, the residual low-to-medium grade cold energy from LNG cold energy utilization is difficult to fully utilize when local cooling demand is saturated. LNG receiving terminals typically require natural gas return pipeline temperatures above 0°C, meaning users need to expend resources to process this waste cold. The new liquid compressed CO2 energy storage scheme not only achieves a high-efficiency, highly integrated, safe, and pollution-free energy storage system but also fully utilizes the waste heat and cold resources in the surrounding area of ​​the energy storage power station.

[0049] In one embodiment, the solid-phase cold storage device further includes: Storage module: Stores: Under the conditions of baseline CO2 flow rate and baseline solid-phase cold storage medium circulation characteristic parameters, the LNG flow rate-air cooling capacity curve of liquefied cold box heat exchanger 21; Under baseline CO2 and LNG flow conditions, the solid-phase cold storage medium circulation characteristic coefficient-air temperature difference curve (air inlet temperature difference of liquefied cold box heat exchanger - air outlet temperature difference of liquefied cold box heat exchanger). Blower detection module: Used to detect the airflow at the outlet of blower 20; Calculation Module 1: Used to determine the circulation characteristic parameters of the solid-phase cold storage medium based on the fan detection module (solid-phase cold storage medium circulation characteristic coefficient = actual solid-phase cold storage medium circulation characteristic parameter ÷ reference solid-phase cold storage medium circulation characteristic parameter; cold storage medium circulation characteristic parameter = air flow rate × air density). Detection module: Used to detect the CO2 parameters at the CO2 inlet of the liquefied cold box heat exchanger 21. The CO2 parameters include: CO2 flow rate, CO2 temperature, and CO2 pressure. Calculation Module 2: Used to calculate the coupling heat transfer characteristic coefficient of CO2 based on the detection module; The coupling heat transfer characteristic coefficient of CO2 = CO2 flow rate × (CO2 inlet temperature - CO2 liquefaction reference temperature under pressure) × pressure correction coefficient; In this scheme, the reference CO2 coupled heat transfer characteristic coefficient refers to the coupled heat transfer characteristic coefficient of CO2 under reference operating conditions (usually the standard operating conditions of design or normal operation, including parameters such as reference CO2 flow rate, reference gas pressure, and reference temperature).

[0050] The pressure correction factor is based on the influence of the deviation between the actual CO2 pressure and the reference pressure on heat transfer characteristics, and is obtained through experimental calibration or engineering experience fitting. The specific process is as follows: select different pressure conditions, and under fixed parameters such as CO2 flow rate and temperature, measure the changes in heat transfer characteristics; compare the heat transfer characteristics under the reference pressure (usually the standard pressure under the design conditions), and fit the quantitative relationship between pressure and the degree of heat transfer correction, that is, the pressure correction factor (with a value of 0.9 to 1.1).

[0051] Acquisition module: used to acquire the latest preset time heat exchange efficiency (ratio of actual heat exchange to theoretical heat exchange) data of the liquefied cold box heat exchanger 21; Analysis Module 1: Used to determine the required cooling capacity for CO2 condensation by combining CO2 flow rate and CO2 temperature, and to determine the range of required air cooling capacity based on the required cooling capacity for CO2 condensation, the coupling heat transfer characteristic coefficient of CO2, and the acquisition module. Determining the cooling requirement for CO2 condensation: Combining the detected CO2 flow rate and CO2 temperature, and based on the phase change thermodynamic characteristics of CO2 (such as latent heat of condensation, sensible heat change, etc.), the cooling requirement required for CO2 to condense into a liquid from its current state is calculated. This is the basis for subsequent cooling demand and is the existing technology.

[0052] Determine the required air cooling capacity range by combining multi-dimensional data: Based on the "air flow rate-heat exchange efficiency curve of liquefied cold box heat exchanger 21", this curve reflects the heat exchange efficiency of the heat exchanger under different air flow rates and can be used to determine the effective range of air flow rate under a specific heat exchange efficiency.

[0053] Combining the heat exchange efficiency data obtained from the "acquisition module", and taking into account the cooling requirement for CO2 condensation, the above curves, and the coupling heat transfer characteristic coefficient, the air cooling requirement range is finally determined to meet the requirements for CO2 condensation by deriving the formula (required air cooling range = required cooling requirement for CO2 condensation ÷ predicted efficiency range, where the predicted efficiency range is determined by the coupling heat transfer characteristic coefficient and the heat exchange efficiency data). This provides a basis for subsequent module adjustments to the fan and LNG flow rates.

[0054] C = Average heat transfer efficiency obtained by the acquisition module × Coupling heat transfer characteristic coefficient of CO2 ÷ Coupling heat transfer characteristic coefficient of reference CO2; The above average value is the arithmetic mean. Predicted efficiency range = [0.9C, C]; Analysis Module 2: This module combines the LNG flow rate with the air cooling capacity curve of the liquefied cold box heat exchanger 21 to find the corresponding LNG flow rate range (the range of LNG flow rates that match the air cooling capacity in the curve). Analysis Module 3: Based on the solid-phase cold storage medium circulation characteristic coefficient and the LNG flow range, find the corresponding optimal range of the solid-phase cold storage medium circulation characteristic coefficient (specifically, through experimental calibration: under different LNG flow ranges, test the energy consumption and heat exchange effect corresponding to the solid-phase cold storage medium circulation characteristic coefficient, and select the range with the best "energy consumption-heat exchange effect ratio" as the optimal range of the characteristic coefficient; the optimal range of the solid-phase cold storage medium circulation characteristic coefficient is determined in advance through experimental calibration and the formation of a mapping table), and determine the target fan speed; Control module: Used to control the actual speed of blower 20 to the target blower speed, and to control the actual LNG flow rate to be within the LNG flow rate range.

[0055] Reference CO2 flow rate: refers to the CO2 medium flow rate value used as a reference standard under design or normal operating conditions. It is one of the reference conditions for various subsequent curves (such as LNG flow rate-air cooling capacity curve, solid phase cold storage medium circulation characteristic coefficient-air temperature difference curve, etc.).

[0056] Reference solid-phase cold storage medium circulation characteristic parameters: solid-phase cold storage medium under reference operating conditions (such as reference...) Cyclic characteristic parameters (including the theoretical / rated wind speed of the corresponding fan) under CO2 flow rate (in the liquefied cold box heat exchanger, the rated flow rate can be used) and benchmark LNG flow rate (in the LNG heat exchanger, the rated flow rate can be used) are provided.

[0057] LNG flow rate - air cooling capacity curve of liquefied cold box heat exchanger 21: Under the conditions of reference CO2 flow rate and reference solid phase cold storage medium circulation characteristic parameters, the curve reflects the relationship between LNG flow rate and the air cooling capacity required by liquefied cold box heat exchanger 21 (cooling capacity per unit time, in J / s).

[0058] To obtain the "LNG flow rate-air cooling capacity curve of the liquefied cold box heat exchanger 21 under the conditions of baseline CO2 flow rate and baseline solid-phase cold storage medium circulation characteristic parameters": First, the CO2 flow rate and solid-phase cold storage medium circulation characteristic parameters are fixed at baseline values. Then, the LNG flow rate is gradually adjusted (LNG temperature is rated / baseline), and the air cooling capacity of the liquefied cold box heat exchanger 21 is measured under each LNG flow rate condition (this can be calculated from the air flow rate, temperature change, and air specific heat capacity of the liquefied cold box heat exchanger 21, which is existing technology). Finally, the air cooling capacity data corresponding to different LNG flow rates are processed and fitted to obtain the relationship curve between the two.

[0059] To obtain the "solid-phase cold storage medium circulation characteristic coefficient - air temperature difference curve (air inlet temperature difference of the liquefied cold box heat exchanger - air outlet temperature difference of the liquefied cold box heat exchanger) under baseline CO2 and LNG flow rates": First, fix the CO2 and LNG flow rates at baseline values. Next, adjust the circulation state of the solid-phase cold storage medium (e.g., adjust the circulation characteristic parameters by changing the fan parameters). Under each solid-phase cold storage medium circulation characteristic coefficient condition, measure the air inlet and outlet temperature differences of the liquefied cold box heat exchanger. Finally, fit the solid-phase cold storage medium circulation characteristic coefficient with the corresponding air temperature difference data to obtain the relationship curve.

[0060] The beneficial effects of the above technical solution are as follows: Analysis module one accurately calculates the required cooling capacity for CO2 condensation by combining CO2 flow rate and temperature. Then, it determines the required air cooling capacity range using the "air flow rate-heat transfer efficiency curve" and "coupled heat transfer characteristic coefficient," ensuring a perfect match between the air cooling capacity and the cooling capacity requirement for CO2 condensation. This avoids incomplete CO2 condensation or excessive cooling, guaranteeing the stability of the CO2 condensation process. Simultaneously, analysis module two links this cooling demand with the "air cooling capacity-LNG flow rate curve" for LNG liquefaction, achieving coordinated cooling capacity allocation for CO2 condensation and LNG liquefaction, ensuring stable operation of both processes.

[0061] The multi-parameter closed-loop control system forms a complete closed loop, from fan airflow detection and CO2 parameter detection to characteristic parameter calculation, cooling capacity range analysis, and fan speed and LNG flow control. For example, when CO2 flow or temperature fluctuates, the system can adjust the air cooling capacity and LNG flow in real time to prevent process parameters from deviating from design values ​​and ensure continuous and stable production of CO2 condensation and LNG liquefaction.

[0062] Dynamic optimization of heat exchange efficiency is based on the latest heat exchange efficiency data over a preset period. The system can dynamically adjust the air cooling capacity to ensure that the liquefied gas cold box heat exchanger always operates within the high-efficiency range. For example, when the air flow deviates from the optimal value, the analysis module will trigger the fan speed adjustment to maintain the heat exchange efficiency within the preset high-efficiency range, reducing energy waste caused by low heat exchange efficiency.

[0063] The precise quantification of coupled heat exchange characteristics enables a more accurate match between CO2 heat exchange requirements and air cooling, avoiding insufficient or excessive cooling due to estimation errors in heat exchange characteristics, and improving energy utilization efficiency.

[0064] The precise control and analysis module three for blower speed combines the "solid-phase cold storage medium circulation characteristic coefficient" and the "LNG flow range" to determine the target blower speed, ensuring that blower 20 always operates at the lowest energy consumption speed that meets the cooling demand. For example, when the cooling demand decreases, the blower speed automatically decreases, avoiding ineffective energy consumption due to "high speed and low load," and significantly reducing power consumption.

[0065] LNG flow rate is controlled within a range that matches the air cooling capacity, avoiding resource waste caused by excessive LNG transportation. Simultaneously, precise control using a "baseline curve" reduces energy loss during LNG transportation and liquefaction, lowering system operating costs.

[0066] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A liquid compressed CO2 energy storage device based on LNG cold energy utilization, characterized in that: include: Solid-phase cold storage device, the liquid CO2 output from the solid-phase cold storage device is input into a low-pressure liquid CO2 storage tank (1); The cold energy utilization device has a CO2 inlet connected to the CO2 outlet of a low-pressure liquid CO2 storage tank (1) and a CO2 outlet connected to the CO2 inlet of a solid-phase cold storage device.

2. The liquid compressed CO2 energy storage device based on LNG cold energy utilization according to claim 1, characterized in that: The solid-phase cold storage device includes: The CO2 outlet of the liquefied cold box heat exchanger (21) is connected to the inlet of the low-pressure liquid CO2 storage tank (1), and the CO2 inlet of the liquefied cold box heat exchanger (21) is connected to the CO2 outlet of the cold energy utilization device. The solid phase cold storage medium storage tank (18) is connected to the air inlet of the induced draft fan (19) and the air outlet of the blower (20) at the top, and to the air inlet of the liquefied cold box heat exchanger (21) and the air outlet of the LNG heat exchanger (22) at the bottom.

3. The liquid compressed CO2 energy storage device based on LNG cold energy utilization according to claim 1, characterized in that: Cold energy utilization devices include: The first-stage turbine preheater (13), the first-stage CO2 turbine (14), the second-stage turbine preheater (15), and the second-stage CO2 turbine (16) are connected. The CO2 outlet of the second-stage CO2 turbine (16) is connected to the CO2 inlet of the liquefied cold box heat exchanger (21). The CO2 inlet of the second-stage CO2 turbine (16) is connected to the CO2 outlet of the second-stage turbine preheater (15). The CO2 inlet of the second-stage turbine preheater (15) is connected to the CO2 outlet of the first-stage CO2 turbine (14). The CO2 inlet of the first-stage CO2 turbine (14) is connected to the CO2 outlet of the first-stage turbine preheater (13). The CO2 inlet of the first-stage turbine preheater (13) is connected to the outlet of the low-pressure liquid CO2 storage tank (1). A room temperature water tank (12) has its inlet connected to the outlets of the first-stage turbine preheater (13) and the second-stage turbine preheater (15), and the inlets of the first-stage turbine preheater (13) and the second-stage turbine preheater (15) are connected to the outlet of the high temperature water tank (17).

4. A liquid compressed CO2 energy storage device based on LNG cold energy utilization according to claim 3, characterized in that: The CO2 inlet of the first-stage turbine preheater (13) is directly connected to the outlet of the low-pressure liquid CO2 storage tank (1) via a pipeline; the cold energy utilization device also includes: The preheater (23) has its inlet connected to the outlet of the normal temperature water tank (12) and its outlet connected to the inlet of the high temperature water tank (17).

5. A liquid compressed CO2 energy storage device based on LNG cold energy utilization according to claim 3, characterized in that: The cold energy utilization device also includes: The outlet of the reheating cold box heat exchanger (3) and the low-pressure liquid CO2 storage tank (1) are connected to the inlet of the reheating cold box heat exchanger (3). The outlet of the reheating cold box heat exchanger (3) is connected to the CO2 inlet of the carbon dioxide compressor unit. The CO2 outlet of the carbon dioxide compressor unit is connected to the CO2 inlet of the supercooler (10). The CO2 outlet of the supercooler (10) is connected to the inlet of the high-pressure liquid CO2 storage tank (11). The outlet of the high-pressure liquid CO2 storage tank (11) is connected to the CO2 inlet of the first-stage CO2 turbine (14). The outlet of the carbon dioxide compressor unit is connected to the inlet of the high-temperature water tank (17).

6. A liquid compressed CO2 energy storage device based on LNG cold energy utilization according to claim 5, characterized in that: The carbon dioxide compressor unit includes: Medium-pressure CO2 compressor (6), medium-pressure compressor stage aftercooler (7), high-pressure CO2 compressor (8), high-pressure compressor stage aftercooler (9), subcooler (10); the CO2 inlet of the medium-pressure CO2 compressor (6) is connected to the CO2 outlet of the reheating cold box heat exchanger (3), the CO2 outlet of the medium-pressure CO2 compressor (6) is connected to the CO2 inlet of the medium-pressure compressor stage aftercooler (7), the CO2 outlet of the medium-pressure compressor stage aftercooler (7) is connected to the CO2 inlet of the high-pressure CO2 compressor (8), the CO2 outlet of the high-pressure CO2 compressor (8) is connected to the CO2 inlet of the high-pressure compressor stage aftercooler (9), the CO2 outlet of the high-pressure compressor stage aftercooler (9) is connected to the CO2 inlet of the subcooler (10), the CO2 outlet of the subcooler (10) is connected to the CO2 inlet of the high-pressure liquid CO2 storage tank (11), and the CO2 outlet of the high-pressure liquid CO2 storage tank (11) is connected to the CO2 inlet of the first-stage turbine preheater (13); The outlets of the medium-pressure compressor stage aftercooler (7) and the high-pressure compressor stage aftercooler (9) are connected to the inlet of the high-temperature water tank (17).

7. A liquid compressed CO2 energy storage device based on LNG cold energy utilization according to claim 5, characterized in that: The outlet of the low-pressure liquid CO2 storage tank (1) is connected to the inlet of the reheating cold box heat exchanger (3) via a cryogenic CO2 pump (24); Hot water from the outside is fed into the high-temperature water tank (17); the outlet of the normal temperature water tank (12) is also connected to the inlet of the reheating cold box heat exchanger (3), and the reheating cold box heat exchanger (3) outputs cooling water to the outside.

8. A liquid compressed CO2 energy storage device based on LNG cold energy utilization according to claim 7, characterized in that: The cold energy utilization device also includes: The preheater (23) has its inlet connected to the CO2 outlet of the high-pressure liquid CO2 storage tank (11), and its CO2 inlet connected to the CO2 inlet of the first-stage turbine preheater (13).

9. A liquid compressed CO2 energy storage device based on LNG cold energy utilization according to claim 2, characterized in that: Also includes: Storage module: Stores: Under the conditions of baseline CO2 flow rate and baseline solid-phase cold storage medium circulation characteristic parameters, the air cooling capacity curve of LNG flow rate-liquefied cold box heat exchanger (21) is shown. Under baseline CO2 and LNG flow conditions, the solid-phase cold storage medium circulation characteristic coefficient-air temperature difference curves are used. Fan detection module: used to detect the air flow at the outlet of the blower (20); Calculation Module 1: Used to determine the circulation characteristic parameters of the solid-phase cold storage medium based on the fan detection module; Detection module: used to detect the CO2 parameters at the CO2 inlet of the liquefied cold box heat exchanger (21). The CO2 parameters include: CO2 flow rate, CO2 temperature, and CO2 pressure. Calculation Module 2: Used to calculate the coupling heat transfer characteristic coefficient of CO2 based on the detection module; Acquisition module: used to acquire the latest heat exchange efficiency data of the liquefied cold box heat exchanger (21) for the latest preset duration; Analysis Module 1: Used to determine the required cooling capacity for CO2 condensation by combining CO2 flow rate and CO2 temperature, and to determine the range of required air cooling capacity based on the required cooling capacity for CO2 condensation, the coupling heat transfer characteristic coefficient of CO2, and the acquisition module. Analysis Module 2: Used to combine the air cooling capacity curve of LNG flow rate and liquefied cold box heat exchanger (21) to find the corresponding LNG flow rate range according to the required air cooling capacity range.

10. A liquid compressed CO2 energy storage device based on LNG cold energy utilization according to claim 9, characterized in that: Also includes: Analysis Module 3: Based on the solid-phase cold storage medium circulation characteristic coefficient and LNG flow range, find the corresponding optimal range of solid-phase cold storage medium circulation characteristic coefficient and determine the target fan speed; Control module: Used to control the actual speed of the blower (20) to the target blower speed, and to control the actual LNG flow rate to be within the LNG flow rate range.

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