Liquid air energy storage system

Abstract

The liquid air energy storage system comprises an air liquefaction subsystem and an LNG regasification subsystem, the air liquefaction subsystem comprises a seventh heat exchanger, and the first inlet end of the seventh heat exchanger is sequentially connected with a second heat exchanger, a second compressor, a first heat exchanger and a first compressor in series; the first outlet end is sequentially connected with a first stop valve and a liquid air storage tank in series; the LNG regasification subsystem comprises an LNG storage tank, a second booster pump and a fourth expansion machine which are sequentially connected in series; the second inlet end of the seventh heat exchanger is connected with the second booster pump, and the second outlet end of the seventh heat exchanger is connected with the fourth expansion machine. Clean air is used as an energy storage medium, a large amount of cold energy released in the LNG regasification process is used for air liquefaction, and electric energy is stored in the form of liquid air; and liquid air is gasified and expanded for power generation in the peak period of power utilization, and an organic Rankine cycle system is introduced to convert compression heat and cold energy into electric energy, so that the overall efficiency is further improved.

Description

Technical Field

[0001] The present invention relates to the field of air energy storage, and in particular to a liquid air energy storage system. Background Art

[0002] As the share of renewable energy sources such as wind and photovoltaic power increases, the intermittent and unstable nature of their generation puts pressure on the stable operation of the power grid. Liquid air energy storage (LAES) utilizes its "peak shaving" function to convert excess electricity into liquid air for storage and release during peak demand, mitigating grid fluctuations. As an emerging large-scale, long-duration energy storage technology, LAES, with its unique technical characteristics and comprehensive advantages, demonstrates significant potential in energy transition and renewable energy integration. Compared to other forms of energy storage, its core advantages include outstanding long-term energy storage capacity, flexible storage durations, scalability, high energy density, safety and reliability, environmental friendliness, and geographic compatibility. LNG, on the other hand, releases a significant amount of cryogenic cold energy (typically from -162°C to room temperature) during the regasification process. However, traditional receiving stations often use seawater heating for vaporization, resulting in waste of this cold energy. LAS systems, utilizing LNG cold energy for the air liquefaction stage, can significantly reduce system energy consumption while addressing the global challenge of LNG cold energy recovery. In addition, a large amount of waste heat is generated when air is compressed (such as the heat of compression in thermal oil), and a large amount of high-grade cold energy is also released during the air vaporization process, which is insufficiently utilized by traditional systems. The introduction of the organic Rankine cycle system can convert waste heat and cold energy into electrical energy, further improving overall efficiency. In the existing technology, a large amount of cold energy generated during the regasification of liquid air for power generation is stored using an intermediate medium and used for the next air liquefaction. This method of recycling and reusing cold energy will inevitably cause cold energy loss during the storage process, thereby reducing energy utilization efficiency. Summary of the Invention

[0003] The purpose of the present invention is to provide a liquid air energy storage system with the characteristics of flexible energy storage duration, high energy density, safety and reliability, flexible deployment, and high energy efficiency. It uses clean air as the energy storage medium, utilizes the large amount of cold energy released during the LNG regasification process to liquefy the air, and stores electrical energy in the form of liquid air; during peak electricity consumption periods, the liquid air is vaporized and expanded to generate electricity, and an organic Rankine cycle system is introduced to convert compression heat and cold energy into electrical energy, further improving the overall efficiency. It has broad development prospects and important practical application value.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention discloses a liquid air energy storage system, comprising an air liquefaction subsystem and an LNG regasification subsystem, wherein:

[0006] The air liquefaction subsystem includes a seventh heat exchanger, wherein a first inlet end of the seventh heat exchanger is sequentially connected in series with a second heat exchanger, a second compressor, a first heat exchanger, and a first compressor, and a first outlet end of the seventh heat exchanger is sequentially connected in series with a first stop valve and a liquid air storage tank;

[0007] The LNG regasification subsystem includes an LNG storage tank, a second boosting pump, and a fourth expander connected in series; the second inlet end of the seventh heat exchanger is connected to the second boosting pump, and the second outlet end is connected to the fourth expander.

[0008] A further solution includes a liquid air generator subsystem, which includes a second stop valve, a third heat exchanger, a fourth heat exchanger, a first expander, a fifth heat exchanger, and a second expander connected in series; the second stop valve is connected to the outlet end of the liquid air storage tank.

[0009] A further solution includes an organic Rankine cycle subsystem, which includes a third expander, a sixth heat exchanger, and a first booster pump connected in sequence; wherein the third heat exchanger is connected between the third expander and the first booster pump.

[0010] A further solution: also includes a waste heat recovery subsystem, which includes a low-temperature medium storage tank, a first circulation pump, a second circulation pump, and a high-temperature medium storage tank; wherein, one end of the low-temperature medium storage tank is connected to an outlet end of the sixth heat exchanger, and the other end is connected in series with the first circulation pump and then connected to an inlet end of the first heat exchanger; an outlet end of the first heat exchanger is connected in series with the high-temperature medium storage tank and the second circulation pump in sequence, and then connected to an inlet end of the sixth heat exchanger.

[0011] A further solution is that the inlet end of the high-temperature medium storage tank is connected to the first circulation pump through a second heat exchanger.

[0012] A further solution: the second circulation pump and the low-temperature medium storage tank are connected together through a fifth heat exchanger.

[0013] A further solution is that the inlet end of the second circulation pump and the low-temperature medium storage tank are connected together through a fourth heat exchanger.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] By coupling LNG regasification with the organic Rankine cycle, the present invention fully utilizes the cold energy released during the LNG regasification process and the waste heat and cold energy generated during the air liquefaction and gasification process, thereby solving the technical problems of the liquid air energy storage system coupled with LNG regasification and the organic Rankine cycle. It has certain practical engineering significance, realizes the efficient utilization and conversion of energy, and has the characteristics of flexible energy storage time, high energy density, safety and reliability, flexible deployment, and high energy efficiency. It has broad development prospects and important practical application value.

[0016] Specifically, the large amount of high-grade cold energy released during the LNG regasification process is fully utilized to liquefy air, thereby achieving the purpose of energy storage, reducing system energy consumption, and improving energy utilization; the cold energy generated during the liquid air regasification power generation process is directly converted into electrical energy through the organic Rankine cycle, thus eliminating the process of using an intermediate medium to store cold energy and reuse it, reducing cold energy loss, and improving energy conversion efficiency; the large amount of waste heat generated during air compression is utilized to increase the temperature of the air expansion and organic Rankine cycle evaporator, thereby increasing the power output; the LNG is pressurized, and then vaporized and expanded to output power, further improving the power output of the total system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the present invention;

[0018] In the figure: 1-first compressor; 2-first heat exchanger; 3-second compressor; 4-second heat exchanger; 5-first stop valve; 6-liquid air storage tank; 7-second stop valve; 8-third heat exchanger; 9-fourth heat exchanger; 10-first expander; 11-fifth heat exchanger; 12-second expander; 13-third expander; 14-sixth heat exchanger; 15-first booster pump; 16-low-temperature medium storage tank; 17-first circulating pump; 18-second circulating pump; 19-high-temperature medium storage tank; 20-LNG storage tank; 21-second booster pump; 22-seventh heat exchanger; 23-fourth expander. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0021] See also Figure 1 In this embodiment, a liquid air energy storage system includes an air liquefaction subsystem and an LNG regasification subsystem, wherein:

[0022] The air liquefaction subsystem includes a seventh heat exchanger 22, a first inlet end of the seventh heat exchanger 22 is sequentially connected in series with a second heat exchanger 4, a second compressor 3, a first heat exchanger 2, and a first compressor 1, and a first outlet end is sequentially connected in series with a first stop valve 5 and a liquid air storage tank 6;

[0023] The LNG regasification subsystem includes an LNG storage tank 20, a second booster pump 21, and a fourth expander 23, connected in series. The second inlet of the seventh heat exchanger 22 is connected to the second booster pump 21, and the second outlet is connected to the fourth expander 23. The seventh heat exchanger 22 transfers cold energy from the LNG regasification subsystem to the air liquefaction subsystem, replacing the energy consumed in the traditional liquefaction process. This significantly reduces system energy consumption and achieves efficient air liquefaction. The second booster pump 21 pressurizes the LNG, which is then vaporized in the seventh heat exchanger 22. Finally, the LNG is expanded in the fourth expander 23 to generate power, further increasing the overall system's electrical output.

[0024] Furthermore, it also includes a liquid air generator sub-system, which includes a second stop valve 7, a third heat exchanger 8, a fourth heat exchanger 9, a first expander 10, a fifth heat exchanger 11, and a second expander 12 connected in series in sequence; the second stop valve 7 is connected to the outlet end of the liquid air storage tank 6.

[0025] Furthermore, the system also includes an organic Rankine cycle subsystem, which comprises a third expander 13, a sixth heat exchanger 14, and a first booster pump 15, connected in sequence. The third heat exchanger 8 is connected between the third expander 13 and the first booster pump 15. The organic Rankine cycle subsystem directly absorbs the cooling energy released by the liquid-to-air generator system through the third heat exchanger 8, driving the organic working fluid to circulate and generate electricity.

[0026] Furthermore, a waste heat recovery subsystem is included, comprising a low-temperature medium storage tank 16, a first circulation pump 17, a second circulation pump 18, and a high-temperature medium storage tank 19. One end of the low-temperature medium storage tank 16 is connected to an outlet of the sixth heat exchanger 14, and the other end is connected in series with the first circulation pump 17, and then to an inlet of the first heat exchanger 2. The outlet of the first heat exchanger 2 is connected in series with the high-temperature medium storage tank 19 and the second circulation pump 18, and then to an inlet of the sixth heat exchanger 14. The waste heat recovery subsystem utilizes the large amount of waste heat generated during air compression to increase the temperature of the air expansion and organic Rankine cycle evaporator, thereby increasing the electrical output power.

[0027] Furthermore, the inlet end of the high-temperature medium storage tank 19 is connected to the first circulation pump 17 through the second heat exchanger 4 .

[0028] Furthermore, the second circulation pump 18 and the low-temperature medium storage tank 16 are connected together through the fifth heat exchanger 11 .

[0029] Furthermore, the inlet end of the second circulation pump 18 and the low-temperature medium storage tank 16 are connected together through the fourth heat exchanger 9 .

[0030] The operating principle of the present invention:

[0031] During periods when electrical energy storage is required, air enters the air liquefaction subsystem and first passes through the first compressor 1, first heat exchanger 2, second compressor 3, and second heat exchanger 4, becoming room-temperature, high-pressure air. The heat of compression generated in the first and second compressors 1 and 3 is absorbed by the intermediate medium in the waste heat recovery subsystem via the first and second heat exchangers 2 and 4. The room-temperature, high-pressure air then passes through the seventh heat exchanger 22, where it is cooled by the refrigeration of LNG in the vaporization subsystem and liquefied into liquid air. Finally, it passes through the first shut-off valve 5 and enters the liquid air storage tank 6 for storage.

[0032] The liquid air generator subsystem is connected to the organic Rankine cycle subsystem through the third heat exchanger 8 for heat exchange; the liquid air generator subsystem is connected to the waste heat recovery subsystem through the fifth heat exchanger 11 and the fourth heat exchanger 9 for heat exchange.

[0033] When electrical energy needs to be released, the liquid air in the liquid air storage tank 6 passes through the second shut-off valve 7 and enters the third heat exchanger 8 for heating and vaporization. The cooling energy is then carried away by the circulating medium in the organic Rankine cycle. The normal-temperature, high-pressure air then passes through the fourth heat exchanger 9, the first expander 10, the fifth heat exchanger 11, and the second expander 12 before being discharged into the environment. The high-pressure air exchanges heat with the high-temperature intermediate medium in the waste heat recovery subsystem in the fourth and fifth heat exchangers 9 and 11, heating it again. It then expands in the first and second expanders 10 and 12, generating electricity.

[0034] Furthermore, the organic Rankine cycle and the waste heat recovery subsystem are connected via the sixth heat exchanger 14 to perform heat exchange.

[0035] Furthermore, the circulating medium in the organic Rankine cycle absorbs the cold energy of the liquid air and liquefies in the third heat exchanger 8. After the pressure is increased by the first booster pump 17, it exchanges heat with the high-temperature intermediate medium in the waste heat recovery subsystem and vaporizes in the sixth heat exchanger 14. It then enters the third expander 13 to expand and reduce the pressure and output electrical energy. Finally, the low-pressure circulating medium enters the third heat exchanger 8 again for the next cycle.

[0036] Furthermore, in the waste heat recovery system, during the power storage phase, the low-temperature intermediate medium in the low-temperature medium storage tank 16 is divided into two paths after passing through the first circulation pump 17. These paths enter the second heat exchanger 4 through the a1-b1 path and the first heat exchanger 2 through the a2-b2 path. After absorbing the heat of compression in the air liquefaction subsystem, the high-temperature intermediate medium is converted into a high-temperature intermediate medium and then enters the high-temperature medium storage tank 19 for storage. During the power release phase, the high-temperature intermediate medium in the high-temperature medium storage tank 19 is divided into three paths after passing through the second circulation pump 18. These paths enter the fifth heat exchanger 11 through the c1-d1 path, the fourth heat exchanger 9 through the c2-d2 path, and the sixth heat exchanger 14 through the c3-d3 path. After exchanging heat with air and the circulating medium of the organic Rankine cycle, the high-temperature intermediate medium is converted into a low-temperature intermediate medium and finally returns to the low-temperature medium storage tank 16.

[0037] Furthermore, in the LNG regasification subsystem, the pressure of the LNG in the LNG storage tank 20 increases after passing through the second booster pump 21, and then enters the seventh heat exchanger 22 to exchange heat with the air in the air liquefaction subsystem and gasify, and then enters the fourth expander 23 to expand and reduce the pressure and output electrical energy, and finally delivers the natural gas to the user end.

[0038] Although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0039] Therefore, the above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application; that is, all equivalent modifications made according to the scope of the claims of the present application are within the scope of protection of the claims of the present application.

Claims

1. A liquid air energy storage system, characterized in that: It includes air liquefaction subsystem and LNG regasification subsystem, including: The air liquefaction subsystem comprises a seventh heat exchanger (22), wherein a first inlet end of the seventh heat exchanger (22) is sequentially connected in series with a second heat exchanger (4), a second compressor (3), a first heat exchanger (2), and a first compressor (1), and a first outlet end of the seventh heat exchanger (22) is sequentially connected in series with a first stop valve (5) and a liquid air storage tank (6); The LNG regasification subsystem comprises an LNG storage tank (20), a second boosting pump (21), and a fourth expander (23) connected in series; the second inlet end of the seventh heat exchanger (22) is connected to the second boosting pump (21), and the second outlet end is connected to the fourth expander (23).

2. The liquid air energy storage system according to claim 1, characterized in that: The invention also includes a liquid air generator subsystem, which includes a second stop valve (7), a third heat exchanger (8), a fourth heat exchanger (9), a first expander (10), a fifth heat exchanger (11), and a second expander (12) connected in series in sequence; the second stop valve (7) is connected to the outlet end of the liquid air storage tank (6).

3. The liquid air energy storage system according to claim 1, characterized in that: The organic Rankine cycle subsystem is also included, and the organic Rankine cycle subsystem includes a third expander (13), a sixth heat exchanger (14), and a first booster pump (15) connected in sequence; wherein the third heat exchanger (8) is connected between the third expander (13) and the first booster pump (15).

4. The liquid air energy storage system according to claim 1, characterized in that: The invention also includes a waste heat recovery subsystem, which includes a low-temperature medium storage tank (16), a first circulation pump (17), a second circulation pump (18), and a high-temperature medium storage tank (19); wherein one end of the low-temperature medium storage tank (16) is connected to an outlet end of the sixth heat exchanger (14), and the other end is connected in series with the first circulation pump (17) and then connected to an inlet end of the first heat exchanger (2); and an outlet end of the first heat exchanger (2) is connected in series with the high-temperature medium storage tank (19) and the second circulation pump (18) in sequence, and then connected to an inlet end of the sixth heat exchanger (14).

5. The liquid air energy storage system according to claim 4, characterized in that: The inlet end of the high-temperature medium storage tank (19) is connected to the first circulation pump (17) through the second heat exchanger (4).

6. The liquid air energy storage system according to claim 4, characterized in that: The second circulation pump (18) and the low-temperature medium storage tank (16) are connected together via a fifth heat exchanger (11).

7. The liquid air energy storage system according to claim 4, characterized in that: The inlet end of the second circulation pump (18) and the low-temperature medium storage tank (16) are connected together through the fourth heat exchanger (9).

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