Liquid compressed carbon dioxide energy storage system coupled with high-temperature heat pump and lithium bromide refrigeration unit

Abstract

This invention relates to the field of liquid compressed carbon dioxide energy storage technology, specifically to a liquid compressed carbon dioxide energy storage system coupled with a high-temperature heat pump and a lithium bromide refrigeration unit. The system includes: a compressed carbon dioxide energy storage subsystem for storing and releasing electrical energy within the energy storage system; a high-temperature heat pump unit as an auxiliary energy storage device; a portion of the high-grade heat energy in a second heat storage tank being used by the lithium bromide refrigeration unit to generate cooling capacity during the energy release phase; another portion of the high-grade heat energy in the second heat storage tank being used by a hot water reheater to heat the stored hot water in the compressed carbon dioxide energy storage subsystem; and a lithium bromide refrigeration unit generating cooling capacity to liquefy low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem and store the liquefied low-pressure carbon dioxide in a low-pressure carbon dioxide storage tank. By generating cooling energy through the aforementioned lithium bromide refrigeration unit, the liquefaction of low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem is achieved, thereby solving the problem of large gas storage chamber volume in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of liquid compressed carbon dioxide energy storage technology, and more specifically to a liquid compressed carbon dioxide energy storage system coupled with a high-temperature heat pump and a lithium bromide refrigeration unit. Background Technology

[0002] Under the "dual carbon" goal, my country will build a new power system based on renewable energy. However, the intermittency and volatility of this new power system will place enormous demands on its regulation capabilities. To address these issues, energy storage is one of the key supporting technologies for achieving power system transformation, and compressed air energy storage technology is one of the most promising large-scale energy storage technologies.

[0003] Compressed carbon dioxide energy storage, or CCES technology, is a novel physical energy storage technology based on compressed air energy storage and the Brayton cycle. It leverages the physical properties of carbon dioxide, building upon the advantages of compressed air energy storage systems. CCES systems offer advantages such as high efficiency, long lifespan, low emissions, and ease of coupling with carbon capture systems to achieve the utilization of captured carbon dioxide as a working fluid. Therefore, it is well-suited to the needs of large-scale, long-term energy storage system construction and sustainable development in my country, and has a very broad prospect for development and application.

[0004] The biggest difference between the aforementioned compressed carbon dioxide energy storage system (CCES) and compressed air energy storage system (CCES) lies in the fact that the CCES system is a closed-loop system, requiring a low-pressure storage chamber to store carbon dioxide. This leads to an increase in the volume of the storage chamber and a decrease in the system's energy storage density. Therefore, it places higher demands on the application environment. Based on these issues, those skilled in the art need to consider how to reduce the volume of the low-pressure storage chamber, thereby increasing the energy storage density of the CCES system and reducing its environmental requirements. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problems of large gas storage chamber volume and low system energy storage density in existing liquid compressed carbon dioxide energy storage systems. To this end, the present invention provides a liquid compressed carbon dioxide energy storage system coupled with a high-temperature heat pump and a lithium bromide refrigeration unit, comprising:

[0006] A compressed carbon dioxide energy storage subsystem is used to store and release electrical energy in the energy storage system. During the energy storage process, the compressor unit generates compression heat. First, the compression heat serves as a low-grade heat source in the high-temperature heat pump unit and as a heat source for the vaporizer at the outlet of the low-pressure carbon dioxide storage tank. Second, the excess compression heat is stored in the first heat storage tank and used to heat the high-pressure carbon dioxide during the energy release process.

[0007] A high-temperature heat pump unit, as an auxiliary energy storage device, converts the low-grade heat source generated during the energy storage process of the compressed carbon dioxide energy storage subsystem into high-grade heat energy, which is stored in a second heat storage tank. A portion of the high-grade heat energy in the second heat storage tank is used by the lithium bromide refrigeration unit to generate cooling capacity during the energy release stage. Another portion of the high-grade heat energy in the second heat storage tank is used to heat the stored hot water in the compressed carbon dioxide energy storage subsystem via a hot water reheater.

[0008] The lithium bromide refrigeration unit generates cooling capacity to complete the liquefaction of low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem and store the liquefied low-pressure carbon dioxide in the low-pressure carbon dioxide storage tank.

[0009] Optionally, the refrigeration temperature range of the lithium bromide refrigeration unit is not lower than 5°C, and the heat exchanger has a heat exchange end difference of 5°C; the pressure of the low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem is not lower than 4.5MPa, so as to ensure that the low-pressure carbon dioxide is completely liquefied.

[0010] Optionally, the heat storage medium in the first and second heat storage tanks is water; during the energy storage process, the liquid compressed carbon dioxide energy storage system:

[0011] In the compressed carbon dioxide energy storage subsystem, the low-pressure carbon dioxide storage tank is vaporized by a vaporizer and then enters the compressor unit. The compressor unit is driven by surplus power from the power grid to generate high-pressure carbon dioxide.

[0012] The heat of compression generated by the compressor unit is absorbed by the first heat exchanger group, and the temperature of the stored water reaches above 60°C. This stored water is used as a low-grade heat source in the high-temperature heat pump unit and as a heat source for the vaporizer at the outlet of the low-pressure carbon dioxide storage tank. Excess heat of compression is stored in the first heat storage tank. The high-pressure carbon dioxide, after being cooled by the first heat exchanger group, is stored in the high-pressure carbon dioxide storage tank.

[0013] The high-temperature heat pump unit and the lithium bromide refrigeration unit perform energy storage: First, the medium-temperature, high-pressure refrigerant liquid in the refrigerant storage tank is throttled by the throttling valve to become a low-temperature, low-pressure refrigerant liquid, which then flows through the evaporator; the hot water in the compressed carbon dioxide energy storage subsystem is used as a heat source to heat and vaporize the low-temperature, low-pressure refrigerant liquid, and the heat absorbed by the low-temperature, low-pressure refrigerant liquid is converted into the latent heat of the refrigerant;

[0014] Driven by surplus power from the grid, the compressor of the high-temperature heat pump unit compresses the low-temperature, low-pressure refrigerant gas into a high-temperature, high-pressure refrigerant gas, thereby converting electrical energy into the internal energy of the refrigerant gas. The high-temperature, high-pressure refrigerant gas enters the condenser, where the hot water in the condenser absorbs the heat from the refrigerant gas. This hot water is stored in the second heat storage tank, and the refrigerant gas condenses into a medium-temperature, high-pressure refrigerant liquid, which returns to the refrigerant storage tank, thus completing the energy storage process of the high-temperature heat pump.

[0015] Optionally, during the energy release process, the liquid compressed carbon dioxide energy storage system:

[0016] In the compressed carbon dioxide energy storage subsystem, the high-pressure carbon dioxide storage tank releases carbon dioxide, which absorbs the heat energy stored in the first heat storage tank through the second heat exchanger group. After being heated, the carbon dioxide enters the expander unit to do work and generate electricity, which is then fed into the power grid.

[0017] In the above energy release process, the lithium bromide refrigeration unit utilizes the stored hot water in the hot water storage tank to generate cold energy. The specific process is as follows:

[0018] In the absorber of the lithium bromide refrigeration unit, the lithium bromide solution absorbs the vapor formed by the refrigerant of the refrigeration unit to form a dilute solution; during the above process, the vapor releases heat, and the temperature of the absorber is reduced by cooling water to maintain the absorption capacity of the lithium bromide solution;

[0019] The dilute solution discharged from the absorber is transferred to the generator; the hot water in the second heat storage tank heats the dilute solution, causing the refrigerant vapor in the dilute solution to separate; during the above process, the concentration and temperature of the dilute solution increase to form an enriched lithium bromide solution.

[0020] The refrigerant vapor enters the condenser, where it is condensed into a liquid state by a cooling tower and then flows back to the evaporator.

[0021] The liquid refrigerant evaporates in the evaporator and cools the circulating water in the compressed carbon dioxide energy storage subsystem; the cooled circulating water is used to cool the carbon dioxide at the outlet of the expander unit, and after being liquefied by the liquefier, the carbon dioxide is stored in the carbon dioxide low-pressure storage tank; the refrigerant vapor evaporated in the evaporator re-enters the absorber and is absorbed by the lithium bromide solution, and the cycle repeats.

[0022] The enriched lithium bromide solution flows out of the generator, enters a heat exchanger for cooling, and then returns to the absorber to continue participating in the absorption process.

[0023] Optionally, the refrigerant in the refrigeration unit is an aqueous solution;

[0024] The refrigerant inlet of the first heat exchanger group is connected to a cooling water tank, which provides cooling water to the first heat exchanger group.

[0025] Optionally, the compressor unit includes at least two compressors; the expander unit includes at least two expanders.

[0026] The technical solution of this invention has the following advantages:

[0027] 1. The liquid compressed carbon dioxide energy storage system coupled with a high-temperature heat pump and a lithium bromide refrigeration unit provided by the present invention includes:

[0028] A compressed carbon dioxide energy storage subsystem is used to store and release electrical energy in the energy storage system. During the energy storage process, the compressor unit generates compression heat. First, the compression heat serves as a low-grade heat source in the high-temperature heat pump unit and as a heat source for the vaporizer at the outlet of the low-pressure carbon dioxide storage tank. Second, the excess compression heat is stored in the first heat storage tank and used to heat the high-pressure carbon dioxide during the energy release process.

[0029] A high-temperature heat pump unit, as an auxiliary energy storage device, converts the low-grade heat source generated during the energy storage process of the compressed carbon dioxide energy storage subsystem into high-grade heat energy, which is stored in a second heat storage tank. A portion of the high-grade heat energy in the second heat storage tank is used by the lithium bromide refrigeration unit to generate cooling capacity during the energy release stage. Another portion of the high-grade heat energy in the second heat storage tank is used to heat the stored hot water in the compressed carbon dioxide energy storage subsystem via a hot water reheater.

[0030] The lithium bromide refrigeration unit generates cooling capacity to complete the liquefaction of low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem and store the liquefied low-pressure carbon dioxide in the low-pressure carbon dioxide storage tank.

[0031] To address the problems of large storage chamber volume and low energy density in existing liquid compressed carbon dioxide energy storage systems, this invention utilizes a lithium bromide refrigeration unit to generate cold energy, thereby liquefying low-pressure carbon dioxide for the compressed carbon dioxide energy storage subsystem. The liquefied low-pressure carbon dioxide is stored in a low-pressure carbon dioxide storage tank, thus solving the problem of large storage chamber volume in existing technologies and achieving the goal of reducing the volume of the low-pressure storage chamber and increasing the energy density.

[0032] Furthermore, in this invention, the high-temperature heat pump unit converts the low-grade heat source generated during the energy storage process of the compressed carbon dioxide energy storage subsystem into high-grade heat energy, which is then stored in the second heat storage tank. This high-grade heat energy can not only be used by the lithium bromide refrigeration unit to produce cooling capacity during the energy release phase, but it can also reheat the hot water stored in the compressed carbon dioxide energy storage subsystem, increasing the inlet carbon dioxide temperature of the expander unit, enhancing the expander's work capacity, and thus improving the system efficiency of the compressed carbon dioxide energy storage subsystem.

[0033] The aforementioned high-temperature heat pump units and lithium bromide refrigeration units achieve efficient conversion of electrical energy into heat energy into cold energy by using low-grade compression heat, thereby improving energy utilization efficiency and enhancing the overall efficiency of the coupled system.

[0034] 2. The liquid compressed carbon dioxide energy storage system coupled with a high-temperature heat pump and a lithium bromide refrigeration unit provided by the present invention has a refrigeration temperature range of not less than 5°C and a heat exchanger with a heat exchange end difference of 5°C; the pressure of low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem is not less than 4.5MPa to ensure that the low-pressure carbon dioxide is completely liquefied.

[0035] In this invention, based on the refrigeration temperature range requirements of the lithium bromide refrigeration unit, ensuring the temperature difference at the heat exchange end of the heat exchanger can effectively guarantee the complete liquefaction of low-pressure carbon dioxide.

[0036] 3. The liquid compressed carbon dioxide energy storage system coupled with a high-temperature heat pump and a lithium bromide refrigeration unit provided by the present invention uses water as the heat storage medium in the first and second heat storage tanks; during the energy storage process, the liquid compressed carbon dioxide energy storage system:

[0037] In the compressed carbon dioxide energy storage subsystem, the low-pressure carbon dioxide storage tank is vaporized by a vaporizer and then enters the compressor unit. The compressor unit is driven by surplus power from the power grid to generate high-pressure carbon dioxide.

[0038] The heat of compression generated by the compressor unit is absorbed by the first heat exchanger group, and the temperature of the stored water reaches above 60°C. This stored water is used as a low-grade heat source in the high-temperature heat pump unit and as a heat source for the vaporizer at the outlet of the low-pressure carbon dioxide storage tank. Excess heat of compression is stored in the first heat storage tank. The high-pressure carbon dioxide, after being cooled by the first heat exchanger group, is stored in the high-pressure carbon dioxide storage tank.

[0039] The high-temperature heat pump unit and the lithium bromide refrigeration unit perform energy storage: First, the medium-temperature, high-pressure refrigerant liquid in the refrigerant storage tank is throttled by the throttling valve to become a low-temperature, low-pressure refrigerant liquid, which then flows through the evaporator; the hot water in the compressed carbon dioxide energy storage subsystem is used as a heat source to heat and vaporize the low-temperature, low-pressure refrigerant liquid, and the heat absorbed by the low-temperature, low-pressure refrigerant liquid is converted into the latent heat of the refrigerant;

[0040] Driven by surplus power from the grid, the compressor of the high-temperature heat pump unit compresses the low-temperature, low-pressure refrigerant gas into a high-temperature, high-pressure refrigerant gas, thereby converting electrical energy into the internal energy of the refrigerant gas. The high-temperature, high-pressure refrigerant gas enters the condenser, where the hot water in the condenser absorbs the heat from the refrigerant gas. This hot water is stored in the second heat storage tank, and the refrigerant gas condenses into a medium-temperature, high-pressure refrigerant liquid, which returns to the refrigerant storage tank, thus completing the energy storage process of the high-temperature heat pump.

[0041] The aforementioned high-temperature heat pump unit can achieve a thermoelectric conversion efficiency of over 3. For every unit of electrical energy consumed by the liquid compressed carbon dioxide energy storage system, two units of heat can be extracted from the low-temperature heat source, resulting in a combined output of three units of high-grade heat. Additionally, the aforementioned lithium bromide refrigeration unit also assists in energy storage, increasing the overall system efficiency.

[0042] 4. The liquid compressed carbon dioxide energy storage system coupled with a high-temperature heat pump and a lithium bromide refrigeration unit provided by the present invention, wherein the liquid compressed carbon dioxide energy storage system, during the energy release process:

[0043] In the compressed carbon dioxide energy storage subsystem, the high-pressure carbon dioxide storage tank releases carbon dioxide, which absorbs the heat energy stored in the first heat storage tank through the second heat exchanger group. After being heated, the carbon dioxide enters the expander unit to do work and generate electricity, which is then fed into the power grid.

[0044] In the above energy release process, the lithium bromide refrigeration unit utilizes the stored hot water in the hot water storage tank to generate cold energy. The specific process is as follows:

[0045] In the absorber of the lithium bromide refrigeration unit, the lithium bromide solution absorbs the vapor formed by the refrigerant of the refrigeration unit to form a dilute solution; during the above process, the vapor releases heat, and the temperature of the absorber is reduced by cooling water to maintain the absorption capacity of the lithium bromide solution;

[0046] The dilute solution discharged from the absorber is transferred to the generator; the hot water in the second heat storage tank heats the dilute solution, causing the refrigerant vapor in the dilute solution to separate; during the above process, the concentration and temperature of the dilute solution increase to form an enriched lithium bromide solution.

[0047] The refrigerant vapor enters the condenser, where it is condensed into a liquid state by a cooling tower and then flows back to the evaporator.

[0048] The liquid refrigerant evaporates in the evaporator and cools the circulating water in the compressed carbon dioxide energy storage subsystem; the cooled circulating water is used to cool the carbon dioxide at the outlet of the expander unit, and after being liquefied by the liquefier, the carbon dioxide is stored in the carbon dioxide low-pressure storage tank; the refrigerant vapor evaporated in the evaporator re-enters the absorber and is absorbed by the lithium bromide solution, and the cycle repeats.

[0049] The enriched lithium bromide solution flows out of the generator, enters a heat exchanger for cooling, and then returns to the absorber to continue participating in the absorption process.

[0050] In this invention, the COP (Coefficient of Performance) of the aforementioned lithium bromide refrigeration unit can currently reach 0.8, meaning that one unit of thermal energy can provide 0.8 units of cooling energy. Combined with the high thermoelectric conversion rate of the aforementioned high-temperature heat pump unit, the high-temperature heat pump unit and the lithium bromide refrigeration unit can achieve the conversion of one unit of electrical energy into 2.4 units of cooling energy through a single energy storage and release process. Compared to directly using the refrigeration unit, its cooling efficiency is significantly improved. Therefore, the coupling system in this invention, through the strong coupling of the compressed carbon dioxide energy storage subsystem, the high-temperature heat pump unit, and the lithium bromide refrigeration unit, utilizes the compressed carbon dioxide energy storage subsystem to provide low-grade thermal energy to the high-temperature heat pump unit. The high-temperature heat pump unit efficiently heats, and the high-grade thermal energy is used for cooling by the lithium bromide refrigeration unit. Simultaneously, it is used to heat the high-pressure carbon dioxide at the inlet of the expansion unit, thereby improving the work capacity of carbon dioxide and increasing the energy storage efficiency of the liquid compressed carbon dioxide energy storage system. The cooling energy of the lithium bromide refrigeration unit is used to liquefy low-pressure carbon dioxide, which can significantly improve the energy storage density of the compressed carbon dioxide energy storage subsystem. Attached Figure Description

[0051] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific 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 from these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of the structure of the liquid compressed carbon dioxide energy storage system provided by the present invention.

[0053] Explanation of reference numerals in the attached figures:

[0054] 1 – Compressed carbon dioxide energy storage subsystem; 2 – High-temperature heat pump unit; 3 – Lithium bromide refrigeration unit; 4 – Compressor unit; 5 – Low-pressure carbon dioxide storage tank; 6 – Vaporizer; 7 – First heat storage tank; 8 – Second heat storage tank; 9 – Hot water reheater; 10 – First heat exchanger group; 11 – High-pressure carbon dioxide storage tank; 12 – Refrigerant storage tank; 13 – Throttling valve; 14 – Evaporator; 15 – Compressor; 16 – Condenser; 17 – Second heat exchanger group; 18 – Expander unit; 19 – Absorber; 20 – Generator; 21 – Condenser; 22 – Evaporator; 23 – Liquefaction unit; 24 – Cooling water tank. Detailed Implementation

[0055] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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 the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0057] Example 1

[0058] This embodiment provides a liquid compressed carbon dioxide energy storage system coupled with a high-temperature heat pump and a lithium bromide refrigeration unit, such as... Figure 1 The diagram shows a publicly disclosed structural schematic of a liquid compressed carbon dioxide energy storage system. It includes:

[0059] The compressed carbon dioxide energy storage subsystem 1 is used to store and release electrical energy in the energy storage system. During the energy storage process, the compressor unit 4 generates compression heat. First, the compression heat serves as a low-grade heat source in the high-temperature heat pump unit 2 and as a heat source for the vaporizer 6 at the outlet of the low-pressure carbon dioxide storage tank 5. Second, the excess compression heat is stored in the first heat storage tank 7, which heats the high-pressure carbon dioxide during the energy release process. The heat storage medium in the first heat storage tank 7 is water.

[0060] High-temperature heat pump unit 2, as an auxiliary energy storage device, converts the low-grade heat source generated during the energy storage process of the compressed carbon dioxide energy storage subsystem 1 into high-grade heat energy, which is stored in a second heat storage tank 8. A portion of the high-grade heat energy in the second heat storage tank 8 is used by the lithium bromide refrigeration unit 3 to produce cooling capacity during the energy release stage. Another portion of the high-grade heat energy in the second heat storage tank 8 is used to heat the stored hot water in the compressed carbon dioxide energy storage subsystem 1 via a hot water reheater 9. The heat storage medium in the second heat storage tank 8 is water.

[0061] A lithium bromide refrigeration unit 3 generates cooling capacity to liquefy low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem 1 and store the liquefied low-pressure carbon dioxide in the low-pressure carbon dioxide storage tank 5. In this embodiment, the refrigeration temperature range of the lithium bromide refrigeration unit 3 is not lower than 5°C, and the heat exchanger has a heat exchange end difference of 5°C; the pressure of the low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem 1 is not lower than 4.5 MPa to ensure complete liquefaction of the low-pressure carbon dioxide.

[0062] In this embodiment, the liquid compressed carbon dioxide energy storage system performs the following during the energy storage process:

[0063] In the compressed carbon dioxide energy storage subsystem 1, the low-pressure carbon dioxide storage tank 5 is vaporized by the vaporizer 6 and then enters the compressor unit 4. The compressor unit 4 is driven by the surplus power of the power grid to generate high-pressure carbon dioxide.

[0064] The compression heat generated by the compressor unit 4 is absorbed by the first heat exchanger group 10, and the temperature of the stored water reaches above 60°C. This stored water is used as a low-grade heat source in the high-temperature heat pump unit 2 and as a heat source for the vaporizer 6 at the outlet of the low-pressure carbon dioxide storage tank 5. Excess compression heat is stored in the first heat storage tank 7. The high-pressure carbon dioxide, cooled by the first heat exchanger group 10, is stored in the high-pressure carbon dioxide storage tank 11. The refrigerant inlet of the first heat exchanger group 10 is connected to the cooling water tank 24, which provides cooling water to the first heat exchanger group 10. The compressor unit 4 includes two compressors.

[0065] The high-temperature heat pump unit 2 and the lithium bromide refrigeration unit 3 perform energy storage: First, the medium-temperature and high-pressure refrigerant liquid in the refrigerant storage tank 12 is throttled by the throttling valve 13 and becomes a low-temperature and low-pressure refrigerant liquid. This low-temperature and low-pressure refrigerant liquid flows through the evaporator 14. The hot water in the compressed carbon dioxide energy storage subsystem 1 is used as a heat source to heat and vaporize this low-temperature and low-pressure refrigerant liquid. The heat absorbed by the low-temperature and low-pressure refrigerant liquid is converted into the latent heat of the refrigerant.

[0066] Driven by surplus power from the grid, the compressor 15 of the high-temperature heat pump unit 2 compresses the low-temperature, low-pressure refrigerant gas into a high-temperature, high-pressure refrigerant gas, thereby converting electrical energy into the internal energy of the refrigerant gas. The high-temperature, high-pressure refrigerant gas enters the condenser 16, where the hot water in the condenser 16 absorbs the heat from the refrigerant gas. This hot water is stored in the second heat storage tank 8. The refrigerant gas condenses into a medium-temperature, high-pressure refrigerant liquid and returns to the refrigerant storage tank 12, thus completing the energy storage process of the high-temperature heat pump.

[0067] In this embodiment, during the energy release process of the liquid compressed carbon dioxide energy storage system:

[0068] In the compressed carbon dioxide energy storage subsystem 1, the high-pressure carbon dioxide gas storage tank 11 releases carbon dioxide. The carbon dioxide absorbs the heat energy stored in the first heat storage tank 7 through the second heat exchanger group 17, and after being heated, it enters the expander unit 18 to do work and generate electricity, which is then connected to the power grid. The expander unit 18 includes two expanders.

[0069] In the above-mentioned energy release process, the lithium bromide refrigeration unit 3 utilizes the stored hot water in the hot water storage tank to generate cold energy. The specific process is as follows:

[0070] In the absorber 19 of the lithium bromide refrigeration unit 3, the lithium bromide solution absorbs the vapor formed by the refrigerant of the refrigeration unit to form a dilute solution; in the above process, the vapor releases heat, and the temperature of the absorber 19 is reduced by cooling water to maintain the absorption capacity of the lithium bromide solution; the refrigerant of the refrigeration unit is an aqueous solution.

[0071] The dilute solution discharged from the absorber 19 is transferred to the generator 20; the hot water in the second heat storage tank 8 heats the dilute solution, causing the refrigerant vapor in the dilute solution to separate; during the above process, the concentration and temperature of the dilute solution increase to form an enriched lithium bromide solution.

[0072] The refrigerant vapor enters the condenser 21, where it is condensed into a liquid state by a cooling tower and then flows back to the evaporator 22.

[0073] The liquid refrigerant evaporates in the evaporator 22 and cools the circulating water in the compressed carbon dioxide energy storage subsystem 1; the cooled circulating water is used to cool the carbon dioxide at the outlet of the expander 18, and after being liquefied by the liquefier 23, the carbon dioxide is stored in the carbon dioxide low-pressure storage tank 5; the refrigerant vapor evaporated in the evaporator 22 re-enters the absorber 19 and is absorbed by the lithium bromide solution, and the cycle repeats.

[0074] The enriched lithium bromide solution flows out of the generator 20, enters the heat exchanger for cooling, and returns to the absorber 19 after the temperature is reduced to continue participating in the absorption process.

[0075] Of course, this embodiment does not specifically limit the pressure value of the low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem 1. In other embodiments, the pressure of the low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem 1 is 5 MPa, or a value greater than 4.5 MPa.

[0076] Of course, this embodiment does not specifically limit the number of compressors and expanders included in compressor unit 4 and expander unit 18. In other embodiments, the compressor unit 4 includes 3 compressors or other numbers of compressors; the expander unit 18 includes 3 expanders or other numbers of expanders.

[0077] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A liquid compressed carbon dioxide energy storage system coupled with a high-temperature heat pump and a lithium bromide refrigeration unit, characterized in that, include: A compressed carbon dioxide energy storage subsystem (1) is used to store and release electrical energy in the energy storage system; During the energy storage process, the compressor unit (4) generates heat of compression. First, the heat of compression serves as a low-grade heat source in the high-temperature heat pump unit (2) and a heat source for the vaporizer (6) at the outlet of the low-pressure carbon dioxide storage tank (5). Second, the excess heat of compression is stored in the first heat storage tank (7) and heats the high-pressure carbon dioxide during the energy release process. The high-temperature heat pump unit (2) serves as an auxiliary energy storage device. The high-temperature heat pump unit (2) converts the low-grade heat source generated during the energy storage process of the compressed carbon dioxide energy storage subsystem (1) into high-grade heat energy, which is stored in the second heat storage tank (8). A portion of the high-grade heat energy in the second heat storage tank (8) is used by the lithium bromide refrigeration unit (3) to generate cooling capacity during the energy release stage. Another portion of the high-grade heat energy in the second heat storage tank (8) is used to heat the hot water in the compressed carbon dioxide energy storage subsystem (1) via the hot water reheater (9). The lithium bromide refrigeration unit (3) generates cooling capacity to complete the liquefaction of low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem (1) and store the liquefied low-pressure carbon dioxide in the low-pressure carbon dioxide storage tank (5). The heat storage medium in the first heat storage tank (7) and the second heat storage tank (8) is hot water; the liquid compressed carbon dioxide energy storage system in the energy storage process: In the compressed carbon dioxide energy storage subsystem (1), the low-pressure carbon dioxide storage tank (5) is vaporized by the vaporizer (6) and then enters the compressor unit (4). The compressor unit (4) is driven by the surplus power of the power grid to generate high-pressure carbon dioxide. The heat generated by the compressor unit (4) is absorbed by the first heat exchanger group (10), and the temperature of the stored water reaches above 60°C. It is used as a low-grade heat source in the high-temperature heat pump unit (2) and as a heat source for the vaporizer (6) at the outlet of the low-pressure carbon dioxide storage tank (5). The excess heat generated by the compressor is stored in the first heat storage tank (7). The high-pressure carbon dioxide cooled by the first heat exchanger group (10) is stored in the high-pressure carbon dioxide storage tank (11). The high-temperature heat pump unit (2) and the lithium bromide refrigeration unit (3) perform energy storage: First, the medium-temperature high-pressure refrigerant liquid in the refrigerant storage tank (12) of the high-temperature heat pump unit (2) is throttled by the throttling valve (13) and becomes a low-temperature low-pressure refrigerant liquid. The low-temperature low-pressure refrigerant liquid flows through the evaporator (14) of the heat pump unit. The hot water in the compressed carbon dioxide energy storage subsystem (1) is used as a heat source to heat and vaporize the low-temperature low-pressure refrigerant liquid. The heat absorbed by the low-temperature low-pressure refrigerant liquid is converted into the latent heat of the refrigerant. The compressor (15) of the high-temperature heat pump unit (2) compresses the low-temperature and low-pressure refrigerant gas under the drive of surplus power from the grid to form a high-temperature and high-pressure refrigerant gas, so as to realize the conversion of electrical energy into the internal energy of the refrigerant gas; the high-temperature and high-pressure refrigerant gas enters the condenser (16) of the heat pump unit, the hot water in the condenser (16) of the heat pump unit absorbs the heat of the refrigerant gas, the hot water is stored in the second heat storage tank (8), and the refrigerant gas condenses into a medium-temperature and high-pressure refrigerant liquid and returns to the refrigerant storage tank (12) to complete the energy storage process of the high-temperature heat pump; During the energy release process, the liquid compressed carbon dioxide energy storage system: In the compressed carbon dioxide energy storage subsystem (1), the high-pressure carbon dioxide gas storage tank (11) releases carbon dioxide. The carbon dioxide absorbs the heat energy stored in the first heat storage tank (7) through the second heat exchanger group (17), and after being heated, it enters the expander unit (18) to do work and generate electricity. The electricity is then connected to the power grid. During the above energy release process, the lithium bromide refrigeration unit (3) uses the stored hot water in the second thermal storage tank (8) to generate cold energy. The specific process is as follows: In the absorber (19) of the lithium bromide refrigeration unit (3), the lithium bromide solution absorbs the vapor formed by the refrigerant of the refrigeration unit to form a dilute solution; in the above process, the vapor releases heat, and the temperature of the absorber (19) is reduced by cooling water to maintain the absorption capacity of the lithium bromide solution; The dilute solution discharged from the absorber (19) is transferred to the generator (20); the hot water in the second heat storage tank (8) heats the dilute solution, causing the refrigerant vapor in the dilute solution to separate; during the above process, the concentration and temperature of the dilute solution increase to form an enriched lithium bromide solution; The refrigerant vapor enters the condenser (21) of the lithium bromide refrigeration unit, where it is condensed into liquid through a cooling tower and flows back to the evaporator (22) of the lithium bromide refrigeration unit. The liquid refrigerant evaporates in the evaporator (22) of the lithium bromide refrigeration unit and cools the circulating water in the compressed carbon dioxide energy storage subsystem (1); the cooled circulating water is used in the liquefaction unit 23 to cool the carbon dioxide at the outlet of the expander unit (18), and after being liquefied by the liquefaction unit (23), the carbon dioxide is stored in the carbon dioxide low-pressure storage tank (5); the refrigerant vapor evaporated in the evaporator (22) of the lithium bromide refrigeration unit re-enters the absorber (19) and is absorbed by the lithium bromide solution, and the cycle repeats. The enriched lithium bromide solution flows out of the generator (20), enters the heat exchanger for cooling, and returns to the absorber (19) after the temperature is reduced to continue participating in the absorption process; The refrigerant in the refrigeration unit is an aqueous solution; The refrigerant inlet of the first heat exchanger group (10) is connected to the cooling water tank (24), which provides cooling water to the first heat exchanger group (10); the hot water stored at the outlet of the first heat storage tank (7) flows sequentially through the hot water reheater (9), the second heat exchanger group (17), and the cooling water tank (24).

2. The liquid compressed carbon dioxide energy storage system according to claim 1, characterized in that, The refrigeration temperature range of the lithium bromide refrigeration unit (3) is not lower than 5°C; the pressure of the low-pressure carbon dioxide in the compressed carbon dioxide energy storage subsystem (1) is not lower than 4.5 MPa, so as to ensure that the low-pressure carbon dioxide is completely liquefied.

3. The liquid compressed carbon dioxide energy storage system according to claim 1, characterized in that, The compressor unit (4) includes at least two compressors; the expander unit (18) includes at least two expanders.

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