Compressed air energy storage system

Abstract

The utility model relates to a compressed air energy storage system in the technical field of compressed air energy storage. The compressed air energy storage system comprises a compression unit, an energy storage unit, an expansion unit and an energy supplementing unit, the compression unit is a cascade type compression mechanism, the expansion unit is a cascade type expansion mechanism, the number of the compressors is the same as that of the expansion machines, and the energy storage unit receives compressed air output by the last-stage compressor and outputs the compressed air into the primary expansion machine; the energy complementing unit comprises energy complementing assemblies formed by connecting an air storage tank and a third heat exchanger in series, each stage of compressor located before the last stage communicates with each stage of expansion machine located after the first stage through one set of energy complementing assemblies, and part of compressed air output by the compressors is input into the air storage tank through branch pipelines. The compressed air in the air storage tank is mixed with the compressed air output by the self-expansion machine after being subjected to heat exchange through the third heat exchanger, and the temperature of the compressed air output by the third heat exchanger is higher than that of the compressed air output by the self-expansion machine. According to the utility model, the electricity-electricity conversion efficiency of the system can be effectively improved.

Description

Technical Field

[0001] This utility model relates to the field of compressed air energy storage technology, specifically, to a compressed air energy storage system. Background Technology

[0002] Compressed air energy storage, as a novel energy storage technology, boasts significant advantages such as large storage capacity, long lifespan, and relatively low cost, and is receiving widespread attention and demonstration applications. A compressed air energy storage system mainly consists of a compressor unit, an expander unit, an air storage system, and a heat exchange system. Among these, the heat exchange system is a key device for realizing energy recovery and reuse, and it is also a crucial component affecting the system's electro-electric conversion efficiency.

[0003] In compressed air energy storage systems, because the expander typically operates during peak electricity consumption periods and does not replenish the system with energy, the parameters of the compressed air vary significantly. The optimal efficiency point of the expander is determined during system design and cannot change with variations in compressed air parameters. When compressed air parameters such as pressure and temperature deviate significantly from design values, the expander's efficiency drops rapidly, reducing the overall system efficiency. Some systems supplement the expander after the primary expander by drawing compressed air from the high-pressure air tank of the energy storage unit, which can improve the expander's efficiency to some extent. However, the compressed air in the high-pressure air tank is high-pressure air formed after multi-stage compression. When compensating the lower-level expander, the pressure match between the high-pressure air and the compressed air discharged from the upper-level expander is poor, making it difficult to guarantee a proper mixing effect. For example, patent publication number CN108316982A discloses a compressed air energy storage expander system. The system includes a compressed air storage tank and a heat exchanger. The outlet of the compressed air storage tank is connected to a quick-closing valve, which is connected to a regulating valve and a make-up air valve. The regulating valve and the make-up air valve are connected to the cold-side inlet of the heat exchanger. The cold-side outlet of the heat exchanger is connected to the expander inlet. The expanders are connected by a drive shaft, with the rightmost expander connected to a generator drive shaft. The hot-side inlet of the heat exchanger is connected to a heat storage tank, and the hot-side outlet is connected to a cold storage tank. There are two or more expanders. By utilizing the regulating characteristics of the make-up air valve, the parameters of the compressed air before each expander are changed, ensuring that the output power of the system expanders is not less than the required power of the system. This patent suffers from the aforementioned related problems. Utility Model Content

[0004] In view of the deficiencies in the existing technology, the purpose of this utility model is to provide a compressed air energy storage system.

[0005] A compressed air energy storage system according to the present invention includes a compression unit, an energy storage unit, an expansion unit, and an energy replenishment unit;

[0006] The compression unit includes a cascaded compression mechanism formed by multiple compressors connected in series, and the expansion unit includes a cascaded expansion mechanism formed by multiple expanders connected in series. The number of compressors and expanders is the same. The energy storage unit receives the compressed air output by the final stage compressor and outputs it to the primary stage expander.

[0007] The energy replenishment unit includes an energy replenishment component formed by a gas storage tank and a third heat exchanger connected in series. Each stage of the compressor before the final stage and each stage of the expander after the primary stage are connected through a set of the energy replenishment components. Part of the compressed gas output from the compressor is input into the gas storage tank through a branch pipeline. The compressed air in the gas storage tank is mixed with the compressed air output from the expander after heat exchange by the third heat exchanger. The temperature of the compressed air output from the third heat exchanger is higher than the temperature of the compressed air output from the expander.

[0008] In some embodiments, the energy replenishment component is further provided with an electric regulating valve and a flow meter, wherein the electric regulating valve and the flow meter are connected in series on the pipeline between the compressor and the gas storage tank.

[0009] In some embodiments, the energy replenishment unit further includes a hot molten salt storage tank and a cold molten salt storage tank, the heat exchange medium inlet of the third heat exchanger is connected to the outlet of the hot molten salt storage tank, and the heat exchange medium outlet of the third heat exchanger is connected to the inlet of the cold molten salt storage tank.

[0010] In some embodiments, the compression unit further includes a first heat exchanger, which is disposed between two adjacent stages of the compressor and between the final stage compressor and the energy storage unit. The compressed air output by the compressor is delivered to the first heat exchanger and the air storage tank through the main pipeline and branch pipeline, respectively.

[0011] In some embodiments, the energy storage unit includes a high-pressure air tank, a cold demineralized water tank, and a hot demineralized water tank. The compressor in the final stage is connected to the high-pressure air tank through the first heat exchanger. The heat exchange medium inlet of the first heat exchanger is connected to the outlet of the cold demineralized water tank, and the heat exchange medium outlet of the first heat exchanger is connected to the inlet of the hot demineralized water tank.

[0012] In some embodiments, the expansion unit further includes a second heat exchanger disposed between the primary expander and the high-pressure air tank and between two adjacent expanders. The heat exchange medium inlet of the second heat exchanger is connected to the outlet of the hot demineralized water tank, and the heat exchange medium outlet of the second heat exchanger is connected to the inlet of the cold demineralized water tank.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] This invention establishes a one-to-one energy replenishment structure between the expander and the compressor through an energy replenishment unit. This can simultaneously increase the inlet air temperature of the multi-stage expander, widen the operating temperature range of the multi-stage expander, and improve the system's electro-electric conversion efficiency. At the same time, it effectively solves technical problems such as poor air-mixing degree caused by setting branch pipes for energy replenishment through energy storage tanks, poor energy utilization when high-pressure air is used in low-stage expanders, and increased costs caused by setting up separate energy replenishment devices. Attached Figure Description

[0015] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0016] Figure 1 This is a schematic diagram of the compressed air energy storage system of this utility model. Detailed Implementation

[0017] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0018] This utility model provides a compressed air energy storage system, such as Figure 1 As shown, it mainly includes a compression unit, an energy storage unit, an expansion unit, and a replenishment unit.

[0019] The compression unit mainly includes a cascaded air compression mechanism formed by multiple compressors 110 connected in series, and multiple first heat exchangers 120 connected in series between adjacent compressors 110 and between the compressors 110 and the energy storage unit. The first heat exchangers 120 are used to cool the compressed air output from the compressors 110 through heat exchange. This embodiment uses... Figure 1 The compressor 110 shown is illustrated using three compressors as an example. The three compressors, from primary to final stage, are respectively designated as compressor 111, compressor 112, and compressor 113. Compressed air from compressor 111 is cooled by heat exchanger 120 and then fed into compressor 112. Compressed air from compressor 111 is further compressed to medium-pressure air, which is then cooled by heat exchanger 120 and fed into compressor 113. Compressed air from compressor 113 is further compressed to high-pressure air and fed into high-pressure air tank 210 of the energy storage unit.

[0020] The energy storage unit mainly includes a high-pressure air tank 210, a cold demineralized water tank 220, and a hot demineralized water tank 230. Compressed air output from the third compressor 113 is cooled by heat exchange with the heat exchange medium in the first heat exchanger 120 and then enters the high-pressure air tank 210. The inlet of the heat exchange medium in the first heat exchanger 120 is connected to the outlet of the cold demineralized water tank 220, receiving cooling liquid from the cold demineralized water tank 230. The outlet of the heat exchange medium in the first heat exchanger 120 is connected to the hot demineralized water tank 230, sending the liquid heated by heat exchange with the compressed air into the hot demineralized water tank 230. The liquids in both the cold demineralized water tank 220 and the hot demineralized water tank 230 are demineralized water. In this embodiment, the hot demineralized water tank 230 and the cold demineralized water tank 220 store demineralized water, and the operating temperature range of the demineralized water is 30℃~210℃. Demineralized water, as a heat transfer medium between hot air on the compression side and cold air on the expansion side, can store the heat after multi-stage compression of air and transfer the heat to air before multi-stage expansion, thus saving energy and improving system efficiency.

[0021] The expansion unit mainly includes a cascaded expansion mechanism formed by multiple expanders 310 connected in series, and multiple second heat exchangers 320 connected in series between adjacent expanders 310 and between expanders 310 and high-pressure air tank 210. The number of expanders 310 is the same as the number of compressors 110, and in this embodiment, there are three. The three expanders 310 from the primary stage to the final stage are respectively referred to as the first expander 311, the second expander 312, and the third expander 313. The heat exchange medium inlet of the second heat exchanger 320 is connected to the outlet of the hot demineralized water tank 230, and the heat exchange medium outlet of the second heat exchanger 320 is connected to the inlet of the cold demineralized water tank 220. The first expander 311 receives high-pressure air from the high-pressure air tank 210, and the resulting medium-pressure air is heated by the second heat exchanger 320 before being fed into the second expander 312. The low-pressure air generated by the second expander 312 is heated by the second heat exchanger 320 before being fed into the third expander 313 to perform work. The compressed air generated by the third expander 313 is then discharged.

[0022] The energy replenishment unit mainly includes an energy replenishment component 410, a hot molten salt storage tank 420, and a cold molten salt storage tank 430. There are multiple sets of energy replenishment components 410. Each set connects the compressor 110 located before the final stage to the corresponding expander located after the primary stage. Specifically, in this embodiment, there are two sets of energy replenishment components 410: one set connects the second compressor 112 and the second expander 312, and the other set connects the first compressor 111 and the third expander 313. Specifically, the energy replenishment component 410 mainly includes a gas storage tank 411 and a third heat exchanger 412. Taking the connection between the second compressor 112 and the second expander 312 as an example, the inlet of the gas storage tank 411 is connected to the compressed air outlet of the second compressor 112, and this connection is located before the inlet of the first heat exchanger 120. That is, the medium-pressure air discharged from the second compressor 112 is not cooled by the first heat exchanger 120 and is discharged into the gas storage tank 411 with heat. Medium-pressure air entering the storage tank 411 is heated by heat exchange in the third heat exchanger 412 and then sent to the inlet of the second expander 312. Before entering, it mixes with compressed air discharged from the first expander 311, which has been heated by heat exchange in the second heat exchanger 320. The temperature of the medium-pressure air discharged from the third heat exchanger 412 is higher than that of the compressed air discharged from the second heat exchanger 320. After the temperature of the mixed compressed air rises to a predetermined temperature, it enters the second expander 312 to perform work. The heat exchange medium inlet of the third heat exchanger 412 is connected to the outlet of the hot molten salt storage tank 420, which provides the third heat exchanger 412 with a high-temperature heat exchange medium. The heat exchange medium outlet of the third heat exchanger 412 is connected to the inlet of the cold molten salt storage tank 430, which receives the cooled heat exchange medium after heat exchange in the third heat exchanger 412. In this embodiment, the energy replenishment component 410 is also equipped with an electric regulating valve 413 and a flow meter 414. The electric regulating valve 413 and the flow meter 414 are connected in series on the pipeline before the inlet of the gas storage tank 411. The electric regulating valve 413 and the flow meter 414 improve the precise control of the gas pipeline. In this embodiment, the hot molten salt storage tank 420 and the cold molten salt storage tank 430 store ternary salt. The components of the ternary salt are potassium nitrate, sodium nitrite, and sodium nitrate. The operating temperature range of the ternary salt is 142℃~425℃. Within this temperature range, the ternary salt is stable and in a liquid state, and can participate in air heat exchange.

[0023] The working principle of this embodiment is as follows: First, during the air compression process, while the first compressor 111 is compressing air and inputting it into the second compressor 112, the electric regulating valve 413 in the first group of energy replenishment components 410 adjusts its opening to deliver a predetermined amount of air into the air storage tank 411. Similarly, while the second compressor 112 is compressing air and inputting it into the third compressor 113, the electric regulating valve 413 in the second group of energy replenishment components 410 adjusts its opening to deliver a predetermined amount of air into the air storage tank 411. Secondly, during the air expansion process, the high-pressure air in the high-pressure air tank 210 is heated by heat exchange in the second heat exchanger 320 before entering the first expander 311 to perform work. The compressed air output from the first expander 311 is heated by heat exchange in the second heat exchanger 320 and then output to the second expander 312. Before entering the second expander 312, the switching valve of the second set of energy replenishment components 410 connected to the second expander 312 is opened. The compressed air in its storage tank 411 is heated by heat exchange in the third heat exchanger 413 before entering the second expander 312 and mixing with the compressed gas output from the first expander 311 before entering the second expander 312. Since the temperature of the compressed air in the storage tank 411 after heat exchange with molten salt is higher than the temperature of the compressed air output from the expander after heat exchange with demineralized water, the temperature of the mixture can be increased. Similarly, the compressed air in the storage tank 411 of the first energy replenishment component 410 is mixed with the compressed air output from the second expander 312 after heat exchange with hot molten salt and then with the compressed air after heat exchange with demineralized water before entering the third expander 313.

[0024] This invention establishes a one-to-one energy replenishment structure between the expander and the compressor through an energy replenishment unit. This can simultaneously increase the inlet air temperature of the multi-stage expander, widen the operating temperature range of the multi-stage expander, and improve the system's electro-electric conversion efficiency. At the same time, it effectively solves technical problems such as poor air-mixing degree caused by setting branch pipes for energy replenishment through energy storage tanks, poor energy utilization when high-pressure air is used in low-stage expanders, and increased costs caused by setting up separate energy replenishment devices.

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

[0026] The specific embodiments of this utility model have been described above. It should be understood that this utility model is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the substantive content of this utility model. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A compressed air energy storage system, characterized in that, It includes a compression unit, an energy storage unit, an expansion unit, and a replenishment unit; The compression unit includes a cascaded compression mechanism formed by multiple compressors (110) connected in series, and the expansion unit includes a cascaded expansion mechanism formed by multiple expanders (310) connected in series. The number of compressors (110) and expanders (310) is the same. The energy storage unit receives the compressed air output by the final stage compressor (110) and outputs it to the primary expander (310). The energy replenishment unit includes an energy replenishment component (410) formed by a gas storage tank (411) and a third heat exchanger (412) connected in series. Each stage of the compressor (110) before the final stage and each stage of the expander (310) after the primary stage are connected through a set of energy replenishment components (410). Part of the compressed gas output from the compressor (110) is input into the gas storage tank (411) through a branch pipeline. The compressed air in the gas storage tank (411) is mixed with the compressed air output from the expander (310) after heat exchange by the third heat exchanger (412). The temperature of the compressed air output by the third heat exchanger (412) is higher than the temperature of the compressed air output by the expander (310).

2. The compressed air energy storage system according to claim 1, characterized in that, The energy replenishment component (410) is also provided with an electric regulating valve (413) and a flow meter (414), which are connected in series on the pipeline between the compressor (310) and the gas storage tank (411).

3. The compressed air energy storage system according to claim 2, characterized in that, The energy replenishment unit also includes a hot molten salt storage tank (420) and a cold molten salt storage tank (430). The heat exchange medium inlet of the third heat exchanger (412) is connected to the outlet of the hot molten salt storage tank (420), and the heat exchange medium outlet of the third heat exchanger (412) is connected to the inlet of the cold molten salt storage tank (430).

4. The compressed air energy storage system according to claim 3, characterized in that, The compression unit also includes a first heat exchanger (120), which is disposed between two adjacent stages of the compressor (110) and between the last stage compressor (110) and the energy storage unit. The compressed air output by the compressor (110) is delivered to the first heat exchanger (120) and the air storage tank (411) through the main pipeline and the branch pipeline respectively.

5. The compressed air energy storage system according to claim 4, characterized in that, The energy storage unit includes a high-pressure air tank (210), a cold demineralized water tank (220), and a hot demineralized water tank (230). The compressor (110) in the final stage is connected to the high-pressure air tank (210) through the first heat exchanger (120). The heat exchange medium inlet of the first heat exchanger (120) is connected to the outlet of the cold demineralized water tank (220), and the heat exchange medium outlet of the first heat exchanger (120) is connected to the inlet of the hot demineralized water tank (230).

6. The compressed air energy storage system according to claim 5, characterized in that, The expansion unit further includes a second heat exchanger (320), which is disposed between the primary expander (310) and the high-pressure air tank (210) and between two adjacent expanders (310). The heat exchange medium inlet of the second heat exchanger (320) is connected to the outlet of the hot demineralized water tank (230), and the heat exchange medium outlet of the second heat exchanger (320) is connected to the inlet of the cold demineralized water tank (220).

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