Full-low-pressure liquid air energy storage system

Abstract

The utility model relates to the field of liquid air energy storage, and discloses a full-low-pressure liquid air energy storage system which comprises an air liquefaction unit, a cold storage unit and a nitrogen refrigeration unit, and the air liquefaction unit comprises a first air compressor, a main cold box and a liquid air storage tank which are sequentially connected through pipelines in the air flowing direction; the cold storage unit comprises a cold storage cold tank and a cold storage hot tank which are sequentially connected through a pipeline, and the pipeline between the cold storage cold tank and the cold storage hot tank is communicated with the main cold box; the nitrogen refrigeration unit comprises a first nitrogen compressor and a first nitrogen throttle valve which are sequentially connected through a pipeline in the circular flowing direction of nitrogen, a pipeline between a compression outlet of the first nitrogen compressor and a throttle inlet of the first nitrogen throttle valve forms a first nitrogen cold supply pipeline, and the first nitrogen cold supply pipeline is communicated with the main cold box. The full-low-pressure liquid air energy storage system can provide high-grade cold energy for air liquefaction, the air liquefaction pressure is reduced, and the air liquefaction efficiency is effectively improved.

Description

Technical Field

[0001] The present application belongs to the field of liquid air energy storage technology, and specifically relates to a full low-pressure liquid air energy storage system. Background Art

[0002] In the context of the rapid development of clean energy technology today, liquid air energy storage technology has attracted much attention as an innovative way of energy storage. The liquid air energy storage system is a system that can convert electricity into storage potential and then convert it back into electricity. It can help solve the problem of renewable energy volatility and improve the overall utilization efficiency of clean energy. At present, the air liquefaction pressure in the liquid air energy storage system is generally high, resulting in high equipment costs. At the same time, the quality of the cold source used for air liquefaction is low, resulting in low air liquefaction efficiency, which makes it difficult to meet the needs of low-pressure air liquefaction. Summary of the invention

[0003] In response to at least one of the above-mentioned defects or shortcomings of the prior art, the present application provides a fully low-pressure liquid air energy storage system, which can provide high-quality cold energy for air liquefaction, reduce the air liquefaction pressure, and effectively improve the air liquefaction efficiency.

[0004] In order to achieve the above objectives, the present application provides a full low-pressure liquid air energy storage system, the full low-pressure liquid air energy storage system comprising:

[0005] The air liquefaction unit comprises a first air compressor, a main cold box and a liquid air storage tank which are sequentially connected by pipelines along the flow direction of the air;

[0006] A cold storage unit comprises a cold storage tank (14) and a hot storage tank connected by pipelines along a circulation direction of a cold storage medium, wherein a pipeline between a cold tank outlet of the cold storage tank and a hot tank inlet of the hot storage tank is connected to the main cold box; and

[0007] The nitrogen refrigeration unit comprises a first nitrogen compressor and a first nitrogen throttle valve which are connected in sequence by pipelines along a circulating flow direction of the nitrogen, wherein a pipeline between a compression outlet of the first nitrogen compressor and a throttling inlet of the first nitrogen throttle valve forms a first nitrogen cooling pipeline, and the first nitrogen cooling pipeline is connected to the main cold box.

[0008] In some embodiments, a pipeline between the throttling outlet of the first nitrogen throttle valve and the compression inlet of the first nitrogen compressor forms a second nitrogen cooling pipeline, and the second nitrogen cooling pipeline is connected to the main cold box.

[0009] In some embodiments, a branch air outlet is formed at a section of the first nitrogen cooling pipeline between the main cold box and the first nitrogen throttle valve, a branch air return port is formed at a section of the second nitrogen cooling pipeline between the main cold box and the first nitrogen compressor, the nitrogen refrigeration unit further includes a second nitrogen compressor and a second nitrogen throttle valve, the branch air outlet, the second nitrogen compressor, the second nitrogen throttle valve and the branch air return port are sequentially connected by pipelines along the flow direction of the nitrogen, the pipeline between the second nitrogen compressor and the second nitrogen throttle valve forms a third nitrogen cooling pipeline, and the third nitrogen cooling pipeline is connected to the main cold box.

[0010] In some embodiments, the pipeline between the second nitrogen throttle valve and the branch air return port forms a fourth nitrogen cooling pipeline, and the fourth nitrogen cooling pipeline is connected to the main cold box.

[0011] In some embodiments, the all-low-pressure liquid air energy storage system also includes an organic Rankine cycle unit, which includes a working fluid pump, an air cooling heat exchanger, a working fluid expander and a working fluid condenser connected in sequence by pipelines along the circulation flow direction of the organic working fluid, and the pipeline between the first air compressor and the main cold box is connected to the air cooling heat exchanger.

[0012] In some embodiments, the air liquefaction unit further includes a second air compressor disposed between the air cooling heat exchanger and the main cold box, and the second air compressor is transmission-connected to the working fluid expander.

[0013] In some embodiments, the air liquefaction unit further includes a gas-liquid separator disposed between the main cold box and the liquid air storage tank, and a separation outlet of the gas-liquid separator, the main cold box, and a refrigerant inlet of the working medium condenser are sequentially connected by pipelines.

[0014] In some embodiments, the refrigerant outlet of the working medium condenser is interconnected with a pipeline located between the first air compressor and the air cooling heat exchanger.

[0015] In some embodiments, the all-low-pressure liquid air energy storage system also includes an energy release unit, which includes a liquid air booster pump, a cold storage heat exchanger and an air expander connected in sequence by pipelines along the flow direction of the air, and the booster pump liquid inlet of the liquid air booster pump is connected to the tank liquid outlet of the liquid air storage tank.

[0016] In some embodiments, a pipeline between the hot tank outlet of the cold-storage hot tank and the cold tank inlet of the cold-storage cold tank is connected to the cold-storage heat exchanger.

[0017] Through the above technical scheme, in the energy storage process of the air liquefaction unit, in addition to using the cold storage medium circulating in the cold storage unit to provide cold energy for the low-pressure air of the main cold box, the refrigeration cycle of the nitrogen refrigeration unit can also be used to provide higher-quality cold energy for the low-pressure air, thereby greatly improving the air liquefaction efficiency and reducing the pressure required for air liquefaction, thereby reducing the difficulty of selecting related equipment and helping to save equipment investment costs.

[0018] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present application, but do not constitute a limitation on the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without creative work. In the drawings:

[0020] Figure 1 This is a schematic diagram of a full low-pressure liquid air energy storage system in a specific implementation manner of the present application.

[0021] Description of Reference Numerals

[0022] 1 First air compressor 2 Air cooling heat exchanger

[0023] 3 Working fluid pump 4 Working fluid condenser

[0024] 5 Working fluid expander 6 Second air compressor

[0025] 7 Main cold box 8 Air throttle valve

[0026] 9 Gas-liquid separator 10 Liquid air storage tank

[0027] 11 Liquid air booster pump 12 Cold storage heat exchanger

[0028] 13 Hot storage tank 14 Cold storage tank

[0029] 15 Air expander 16 First nitrogen compressor

[0030] 17 Second nitrogen compressor 18 First nitrogen throttle valve

[0031] 19 Second nitrogen throttle valve DETAILED DESCRIPTION

[0032] The specific implementation of the present application is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present application, and is not used to limit the present application.

[0033] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with exemplary embodiments.

[0034] like Figure 1 As shown, an exemplary embodiment of the present application provides a full low-pressure liquid air energy storage system, which includes an air liquefaction unit, a cold storage unit and a nitrogen refrigeration unit. Among them, the air liquefaction unit includes a first air compressor 1, a main cold box 7 and a liquid air storage tank 10 connected in sequence by pipelines along the flow direction of the air. The first air compressor 1 can be used as a power source to deliver low-pressure air to the main cold box 7. The main cold box 7 can condense and liquefy the air as a heat exchanger. The liquefied air can pass through the air throttle valve 8 and then enter the liquid air storage tank 10, so that the liquefied air is stored in the liquid air storage tank 10. The cold storage unit includes a cold storage tank 14 and a cold storage hot tank 13 connected in sequence by pipelines along the flow direction of the cold storage medium. The pipeline between the cold tank outlet of the cold storage tank 14 and the hot tank inlet of the cold storage hot tank 13 is connected to the main cold box, so that the cold storage medium as a refrigerant can provide coldness for the air located in the main cold box 7. The nitrogen refrigeration unit includes a first nitrogen compressor 16 and a first nitrogen throttle valve 18 which are connected in sequence by pipelines along the circulation flow direction of the nitrogen. The pipeline between the compression outlet of the first nitrogen compressor 16 and the throttling inlet of the first nitrogen throttle valve 18 forms a first nitrogen cooling pipeline. The first nitrogen cooling pipeline is connected to the main cold box 7, so that low-temperature nitrogen can enter the main cold box 7 through the first nitrogen cooling pipeline, providing high-quality cold energy for the air in the main cold box 7.

[0035] It can be seen that in the liquefied energy storage process, the full low-pressure liquid air energy storage system of this exemplary embodiment can not only use the cold storage medium circulating in the cold storage unit to provide cold energy for the low-pressure air in the main cold box 7, but also use the refrigeration cycle of the nitrogen refrigeration unit to provide higher-quality cold energy for the low-pressure air in the main cold box 7, thereby greatly improving the air liquefaction efficiency and reducing the pressure required for air liquefaction, thereby reducing the difficulty of selecting related equipment and helping to save equipment investment costs.

[0036] Considering that the nitrogen passing through the first nitrogen throttle valve 18 generates pressure loss, its pressure and temperature both decrease. In order to further utilize the cold energy of the nitrogen, the pipeline between the throttling outlet of the first nitrogen throttle valve 18 and the compression inlet of the first nitrogen compressor 16 forms a second nitrogen cooling pipeline. The second nitrogen cooling pipeline is connected to the main cold box 7, so that the low-temperature nitrogen flowing out of the first nitrogen throttle valve 18 can enter the main cold box 7 through the second nitrogen cooling pipeline, thereby performing heat exchange with the air in the main cold box 7 again, providing sufficient high-grade cold energy for the air to be liquefied, and further improving the air liquefaction efficiency.

[0037] In an optional or preferred embodiment, referring to Figure 1 The first nitrogen cooling pipeline is located between the main cold box 7 and the first nitrogen throttle valve 18 and is formed with a branch air outlet. The second nitrogen cooling pipeline is located between the main cold box 7 and the first nitrogen compressor 16 and is formed with a branch air return port. The nitrogen refrigeration unit also includes a second nitrogen compressor 17 and a second nitrogen throttle valve 19. Further, the branch air outlet, the second nitrogen compressor 17, the second nitrogen throttle valve 19 and the branch air return port are connected in sequence along the flow direction of nitrogen, which is equivalent to forming a nitrogen branch bypass. In the nitrogen branch bypass, the pipeline between the second nitrogen compressor 17 and the second nitrogen throttle valve 19 is formed as a third nitrogen cooling pipeline, and the third nitrogen cooling pipeline is connected to the main cold box 7. Thus, the nitrogen that flows out after passing through the first nitrogen cooling pipeline and undergoing heat exchange in the main cold box 7 can flow to the second nitrogen compressor 17 through the branch outlet for secondary compression. The compressed nitrogen has a lower temperature and enters the main cold box 7 again through the third nitrogen cooling pipeline to provide cold energy to the air in the main cold box 7, so that the nitrogen refrigeration unit can achieve graded refrigeration and improve energy utilization.

[0038] Furthermore, after the nitrogen flowing out of the main cold box 7 passes through the second nitrogen throttle valve 19, its temperature and pressure are both reduced. In order to further utilize the cold capacity of the nitrogen, the pipeline between the second nitrogen throttle valve 19 and the branch return air port forms a fourth nitrogen cooling pipeline, and the fourth nitrogen cooling pipeline is connected to the main cold box 7, so that the low-temperature nitrogen flowing out of the second nitrogen throttle valve 19 can enter the main cold box 7 through the fourth nitrogen cooling pipeline, thereby performing heat exchange with the air in the main cold box 7 again, further providing more high-grade cold energy for the air to be liquefied, and improving the air liquefaction efficiency.

[0039] In an alternative or preferred embodiment, reference Figure 1The full low-pressure liquid air energy storage system also includes an organic Rankine cycle unit well known to those skilled in the art, which includes a working fluid pump 3, an air cooling heat exchanger 2, a working fluid expander 5 and a working fluid condenser 4 connected in sequence by pipelines along the circulation flow direction of the organic working fluid, wherein the pipeline between the first air compressor 1 and the main cold box 7 is connected to the air cooling heat exchanger 2. Thus, by using the organic Rankine cycle, heat exchange can be performed on the air compressed by the first air compressor 1, and the initial cooling of the compressed air can be achieved, which is conducive to improving the liquefaction efficiency of the air.

[0040] Furthermore, the air liquefaction unit further includes a second air compressor 6 disposed between the air cooling heat exchanger 2 and the main cold box 7. The second air compressor 6 can be used to perform secondary compression on the compressed air after the initial cooling to further reduce its temperature. In addition, the second air compressor 6 is transmission-connected to the working fluid expander 5, so that the working fluid expander 5 can drive the second air compressor 6 to work, thereby making full use of the energy generated by the organic Rankine cycle unit and reducing energy loss.

[0041] Considering that the air flowing out of the main cold box 7 after condensation contains gaseous air and liquid air, in order to separate the two, refer to Figure 1 The air liquefaction unit also includes a gas-liquid separator 9 disposed between the main cold box 7 and the liquid air storage tank 10. Thus, the mixed air flowing out of the main cold box 7 can be separated into liquid air and gaseous air by the gas-liquid separator 9. The liquid air enters the liquid air storage tank 10 through the liquid separation outlet of the gas-liquid separator 9 to achieve air energy storage. On the other hand, the separated gaseous air can be recycled and liquefied again. However, considering that the separated gaseous air has a certain amount of coldness, the coldness of the gaseous air can be recycled first. For example, referring to Figure 1 The separation outlet of the gas-liquid separator 9, the main cold box 7 and the refrigerant inlet of the working medium condenser 4 are connected in sequence by pipelines, so that the gaseous air separated from the gas-liquid separator 9 can re-enter the main cold box 7 to provide cooling for the air to be liquefied, and then enter the working medium condenser 4 to provide cooling for the organic working medium in the organic Rankine cycle unit, thereby effectively recovering the cooling of the gaseous air and improving energy utilization.

[0042] Further, in order to liquefy the gaseous air after the second heating, refer to Figure 1 The refrigerant outlet of the working medium condenser 4 is interconnected with the pipeline between the first air compressor 1 and the air cooling heat exchanger 2, so that the gaseous air after cooling through the working medium condenser 4 can flow back to the air inlet pipeline of the air liquefaction unit, thereby realizing effective recovery of the de-cooled air.

[0043] In an alternative or preferred embodiment, reference Figure 1The full low-pressure liquid air energy storage system also includes an energy release unit, which includes a liquid air booster pump 11, a cold storage heat exchanger 12, and an air expander 15 connected in sequence by pipelines along the flow direction of the air, wherein the booster pump liquid inlet of the liquid air booster pump 11 is connected to the tank liquid outlet of the liquid air storage tank 10. Therefore, in practical applications, when energy release is required, the liquid air booster pump 11 can be used to pump the liquid air in the liquid air storage tank 10 to the cold storage heat exchanger 12 for heat exchange, so that the liquid air is initially heated, and then pumped to the air expander 15 for pressure release, and then the air expander 15 can drive the generator to work, so as to realize the conversion of the internal energy of the liquid air into electrical energy.

[0044] Furthermore, in order to make full use of the cold energy of liquid air and improve the energy release efficiency of liquid air, in this embodiment, the pipeline between the hot tank outlet of the cold storage hot tank 13 and the cold tank inlet of the cold storage cold tank 14 is connected to the cold storage heat exchanger 12 (the connecting pipelines between the cold storage heat exchanger 12 and the cold storage hot tank 13 and the cold storage cold tank 14 are omitted in the accompanying drawings). In this way, the higher temperature cold storage medium can be input from the cold storage hot tank 13 to the cold storage heat exchanger 12, thereby obtaining the cold energy of the liquid air in the energy release process, and then the cooled cold storage medium is re-input into the cold storage cold tank 14, so as to realize the reuse of the cold energy of the liquid air and effectively reduce the overall energy consumption. It should be noted that the cold storage medium described in this exemplary embodiment is propane. In other embodiments, butane, carbon dioxide and other refrigerants can also be selected as cold storage media, and this application does not limit this.

[0045] In summary, the fully low-pressure liquid air energy storage system of the present application is suitable for power stations that use clean energy or fossil energy as energy. By converting excess electrical energy into air internal energy, it can efficiently complete the power peak-shaving task and alleviate the pressure on the equipment caused by the use of power plant equipment and the fluctuation of renewable energy. At the same time, the fully low-pressure liquid air energy storage system of the present application makes up for the disadvantage of low air liquefaction rate and reduces the demand for air liquefaction pressure, thereby reducing the difficulty of selecting related equipment and saving the overall construction cost of the system, which has great guiding significance for the construction of the project.

[0046] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0047] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0048] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0049] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A fully low-pressure liquid air energy storage system, characterized in that: The full low-pressure liquid air energy storage system comprises: An air liquefaction unit comprises a first air compressor (1), a main cold box (7) and a liquid air storage tank (10) which are sequentially connected by pipelines along the flow direction of air; A cold storage unit comprises a cold storage tank (14) and a cold storage hot tank (13) connected by pipelines along a circulation direction of a cold storage medium, wherein a pipeline between a cold tank outlet of the cold storage tank (14) and a hot tank inlet of the cold storage hot tank (13) is connected to the main cold box (7); and A nitrogen refrigeration unit comprises a first nitrogen compressor (16) and a first nitrogen throttle valve (18) which are connected in sequence by pipelines along a circulating flow direction of nitrogen, wherein a pipeline between a compression outlet of the first nitrogen compressor (16) and a throttling inlet of the first nitrogen throttle valve (18) forms a first nitrogen cooling pipeline, and the first nitrogen cooling pipeline is connected to the main cold box (7).

2. The all-low-pressure liquid air energy storage system according to claim 1, characterized in that: The pipeline between the throttling outlet of the first nitrogen throttle valve (18) and the compression inlet of the first nitrogen compressor (16) forms a second nitrogen cooling pipeline, and the second nitrogen cooling pipeline is connected to the main cold box (7).

3. The all-low-pressure liquid air energy storage system according to claim 2 is characterized in that: A branch air outlet is formed at a section of the first nitrogen cooling pipeline between the main cold box (7) and the first nitrogen throttle valve (18); a branch air return port is formed at a section of the second nitrogen cooling pipeline between the main cold box (7) and the first nitrogen compressor (16); the nitrogen refrigeration unit further comprises a second nitrogen compressor (17) and a second nitrogen throttle valve (19); the branch air outlet, the second nitrogen compressor (17), the second nitrogen throttle valve (19) and the branch air return port are sequentially connected by pipelines along the flow direction of the nitrogen; the pipeline between the second nitrogen compressor (17) and the second nitrogen throttle valve (19) forms a third nitrogen cooling pipeline; and the third nitrogen cooling pipeline is connected to the main cold box (7).

4. The all-low-pressure liquid air energy storage system according to claim 3 is characterized in that: The pipeline between the second nitrogen throttle valve (19) and the branch air return port forms a fourth nitrogen cooling pipeline, and the fourth nitrogen cooling pipeline is connected to the main cold box (7).

5. The all-low-pressure liquid air energy storage system according to claim 1, characterized in that: The all-low-pressure liquid air energy storage system also includes an organic Rankine cycle unit, which includes a working fluid pump (3), an air cooling heat exchanger (2), a working fluid expander (5) and a working fluid condenser (4) which are sequentially connected by pipelines along the circulation flow direction of the organic working fluid, and the pipeline between the first air compressor (1) and the main cold box (7) is connected to the air cooling heat exchanger (2).

6. The all-low-pressure liquid air energy storage system according to claim 5, characterized in that: The air liquefaction unit further comprises a second air compressor (6) arranged between the air cooling heat exchanger (2) and the main cold box (7), and the second air compressor (6) is transmission-connected to the working fluid expander (5).

7. The all-low-pressure liquid air energy storage system according to claim 5, characterized in that: The air liquefaction unit further comprises a gas-liquid separator (9) arranged between the main cold box (7) and the liquid air storage tank (10), and a gas separation outlet of the gas-liquid separator (9), the main cold box (7) and a refrigerant inlet of the working medium condenser (4) are sequentially connected by pipelines.

8. The all-low-pressure liquid air energy storage system according to claim 7, characterized in that: The refrigerant outlet of the working medium condenser (4) is in communication with a pipeline located between the first air compressor (1) and the air cooling heat exchanger (2).

9. The all-low-pressure liquid air energy storage system according to claim 1, characterized in that: The full low-pressure liquid air energy storage system also includes an energy release unit, which includes a liquid air booster pump (11), a cold storage heat exchanger (12), and an air expander (15) which are sequentially connected by pipelines along the flow direction of the air, and the booster pump liquid inlet of the liquid air booster pump (11) is connected to the tank liquid outlet of the liquid air storage tank (10).

10. The all-low-pressure liquid air energy storage system according to claim 9, characterized in that: The pipeline between the hot tank outlet of the cold storage hot tank (13) and the cold tank inlet of the cold storage cold tank (14) is connected to the cold storage heat exchanger (12).

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