High-efficiency compressed air energy storage system and method based on salt cavern gas storage

Abstract

The application discloses a kind of high-efficiency compressed air energy storage systems and methods based on salt cavern gas storage, water sprayer is used to spray water mist in the cylinder of compressor;Compressed air outlet of compressor is communicated with the inlet of salt cavern by first pipeline, first steam-water separator is arranged on first pipeline, the outlet of salt cavern is connected with the air inlet of expansion power module by second pipeline, second steam-water separator and dryer are sequentially arranged on second pipeline along the direction of airflow;Heat exchange cycle interface of compressor and heat exchange cycle interface of expansion power module are connected with waste heat utilization cycle system.The present application fully combines the characteristics of salt cavern gas storage, and designs a clever and reasonable system scheme for the problem of low energy conversion efficiency in the compressed air energy storage system.The present application is suitable for the characteristics and working conditions of salt cavern, and can effectively improve the energy efficiency of compressor and expander part, so that the overall efficiency of the system is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of energy storage technology, specifically relating to a high-efficiency compressed air energy storage system and method based on salt cavern gas storage. Background Technology

[0002] Underground energy storage often utilizes depleted oil and gas reservoirs, aquifers, and salt caverns for energy storage construction, showing broad application prospects and serving as a key technology to support the large-scale development of new energy sources and ensure energy security. Salt caverns, the caves left after underground salt extraction via leaching, are vast, structurally stable, and airtight, making them an important form of underground energy storage. Among various energy storage technologies, compressed air energy storage features large capacity and high power, enabling long-term energy transfer, i.e., peak shaving and valley filling, thereby improving energy utilization efficiency and alleviating power grid congestion. Furthermore, compressed air energy storage has lower requirements for geographical conditions. Therefore, storing high-pressure air in abandoned underground salt caverns can serve as both an energy reserve and a way to fully utilize idle underground space, achieving large-scale, efficient storage of various forms of energy. This is a crucial choice for achieving sustainable and green development strategies.

[0003] Existing compressed air energy storage systems generally have low efficiency, mainly due to the low energy conversion efficiency of the compressor. However, using salt caverns for gas storage introduces new problems. During salt extraction, water is injected underground to dissolve rock salt. This water is continuously circulated until the rock salt is completely extracted, leaving caverns for gas storage. Although some brine is subsequently removed through gas injection, a large amount of brine remains at the bottom of the caverns. Furthermore, compressed air is typically high-temperature and high-pressure, while salt caverns maintain a constant temperature of around 25°C year-round. The high-temperature air stored in the salt cavern will condense and release moisture as its temperature gradually decreases. Therefore, the high-pressure air exiting the salt cavern will carry a certain amount of water droplets. When this water-containing gas drives the expander, the impact of these droplets can damage the blades. In low-flow-rate conditions, the temperature may drop below freezing, causing the droplets to freeze. Small ice crystals moving at high speeds can directly damage the blades. These problems pose significant challenges to compressed air energy storage based on salt caverns. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention fully utilizes the "water storage" feature of salt caverns and, in response to the low energy conversion efficiency in compressor air energy storage systems, provides a high-efficiency compressed air energy storage system and method based on salt cavern gas storage. This invention is applicable to the characteristics and operating conditions of salt caverns and can effectively improve the energy efficiency of the compressor and expander components, thereby significantly improving the overall efficiency of the system.

[0005] The technical system used in this invention is as follows:

[0006] A high-efficiency compressed air energy storage system based on salt cavern gas storage includes a compressor, a water sprayer, a first gas-water separator, a salt cavern, an expansion work module, and a waste heat utilization circulation system. The water sprayer is used to spray water mist into the cylinder of the compressor.

[0007] The compressed air outlet of the compressor is connected to the inlet of the salt cavern through the first pipeline. The first steam-water separator is installed on the first pipeline. The outlet of the salt cavern is connected to the air inlet of the expansion work module through the second pipeline. The second pipeline is provided with a second steam-water separator and a dryer in sequence along the airflow direction.

[0008] Both the heat exchanger interface of the compressor and the heat exchanger interface of the expansion work module are connected to the waste heat utilization circulation system.

[0009] Preferably, the water outlets of the first and second steam-water separators are both connected to a water sprayer, and a water filter is provided on the pipeline connecting the second steam-water separator to the water sprayer.

[0010] Preferably, the high-efficiency compressed air energy storage system based on salt cavern gas storage of the present invention further includes a controller, which is connected to the water sprayer and the motor of the compressor. The controller is used to control the water sprayer to adjust the water spray volume in real time according to the input power of the motor, so that the water spray volume of the water sprayer cannot exceed the amount of water evaporated in the compressor cylinder during the gas compression process.

[0011] Preferably, the dryer is a type of dryer that generates heat during dehydration.

[0012] Preferably, quicklime is used as the desiccant in the dryer.

[0013] Preferably, the expansion work module is an expander.

[0014] Preferably, the high-efficiency compressed air energy storage system based on salt cavern gas storage of the present invention further includes a generator, which is connected to an expander.

[0015] Preferably, the waste heat utilization cycle system includes a cooler, a reheater, a cold accumulator, and a heat accumulator. The hot side of the cooler is connected to the heat exchange cycle interface of the compressor; the cold side of the reheater is connected to the heat exchange cycle interface of the expansion work module.

[0016] The cold-side outlet of the cooler is connected to the heat exchange medium inlet of the heat accumulator, and the cold-side inlet of the cooler is connected to the heat exchange medium outlet of the heat accumulator.

[0017] The hot-side outlet of the reheater is connected to the heat exchange medium inlet of the accumulator, and the hot-side inlet of the reheater is connected to the heat exchange medium outlet of the accumulator.

[0018] This invention also provides a method for high-efficiency compressed air energy storage based on salt cavern gas storage. This method employs the high-efficiency compressed air energy storage system based on salt cavern gas storage described above, and includes the following steps:

[0019] Energy storage stage: Surplus electricity from the power grid is used to drive the compressor. The compressor compresses air and delivers it to a salt cavern for storage through a first pipeline. A first steam-water separator separates the steam and water in the compressed air flowing through the first pipeline. During operation, water mist is sprayed into the compressor cylinder through a water sprayer. The sprayed water mist evaporates during the air compression process in the compressor, reducing the temperature inside the compressor cylinder. Waste heat is used to cool the compressor through a circulation system, and the absorbed heat is stored.

[0020] Energy release stage: Compressed air in the salt cavern enters the expansion work module through the second pipeline and performs work; as the compressed air flows in the second pipeline, it is sequentially separated into steam and water by the second steam-water separator and dried by the dryer; the waste heat is used to heat the expanded gas in the expansion work module through the circulation system.

[0021] Preferably, the waste heat utilization cycle system includes a cooler, a reheater, a cold accumulator, and a heat accumulator. The hot side of the cooler is connected to the heat exchange cycle interface of the compressor; the cold side of the reheater is connected to the heat exchange cycle interface of the expansion work module.

[0022] The cold-side outlet of the cooler is connected to the heat exchange medium inlet of the heat accumulator, and the cold-side inlet of the cooler is connected to the heat exchange medium outlet of the heat accumulator.

[0023] The hot-side outlet of the reheater is connected to the heat exchange medium inlet of the accumulator, and the hot-side inlet of the reheater is connected to the heat exchange medium outlet of the accumulator.

[0024] During the energy storage phase, the heat generated during the compressor compression process is circulated out through the heat exchange medium on the hot side of the cooler. The heat exchange medium in the accumulator flows through the cold side of the cooler and absorbs the heat from the hot side of the cooler before entering the accumulator for storage.

[0025] During the energy release phase, the heat exchange medium in the accumulator flows through the hot side of the reheater. The heat exchange medium on the cold side of the reheater absorbs the heat from the hot side of the reheater and then heats the expansion gas in the expansion work module. The heat exchange medium on the hot side of the reheater, after being cooled by heat exchange, enters the cold accumulator for storage.

[0026] The present invention has the following beneficial effects:

[0027] This invention provides a high-efficiency compressed air energy storage system based on salt cavern gas storage, suitable for salt cavern gas storage. Salt caverns contain residual moisture and maintain a constant temperature of 20-35°C, causing the stored high-temperature, high-pressure gas to continuously release moisture. This moisture can then be carried along with the gas as it flows out, potentially damaging the expansion module (such as an expander). While the salt cavern itself contains water, and water is released during the gas storage process, considering that the salt cavern structure will not be damaged by the presence of water, a higher water content is permissible in the incoming high-pressure gas. This invention incorporates a water sprayer that sprays water mist into the compressor cylinder. During air compression, the water mist evaporates and absorbs heat, reducing the temperature inside the compressor cylinder and improving the compressor's compression efficiency. Because the evaporation of water mist in the compressor results in moisture in the compressed air, this invention cleverly utilizes the "water storage" characteristics of salt caverns to provide a retention space for the water droplets that precipitate after water spray compression. This allows the "wet compression" of the compressor to be applied in the energy storage system. Furthermore, a second steam-water separator and dryer ensure the safe operation of the expansion work module, thereby improving the overall system's economy and reliability. This invention achieves near-isothermal operation of the compressor through the dual effects of water spray "wet compression" and waste heat recovery circulation system. The recovered waste heat from the compressor is used to warm the gas in the expansion work module, significantly improving system efficiency and economy. Attached Figure Description

[0028] Figure 1 This is an overall structural diagram of the high-efficiency compressed air energy storage system based on salt cavern gas storage according to the present invention.

[0029] In the diagram: 11-Compressor, 12-Electric motor, 21-Expander, 22-Generator, 33-Salt cavern, 41-Controller, 42-Water sprayer, 43-First steam-water separator, 44-Second steam-water separator, 45-Dryer, 46-Water filter, 51-Cooler, 52-Reheater, 53-Heat accumulator, 54-Cold accumulator, 55-First pipeline, 56-Second pipeline. Detailed Implementation

[0030] In the following, specific embodiments of this application will be described in detail with reference to the accompanying drawings. Based on these detailed descriptions, those skilled in the art will be able to clearly understand and implement this application. Without departing from the principles of this application, features from various embodiments can be combined to obtain new implementations, or certain features from some embodiments can be substituted to obtain other preferred implementations.

[0031] It should be noted that similar or identical parts are referred to by the same reference numerals in the accompanying drawings or description. Implementations not shown or described in the drawings are forms known to those skilled in the art. Furthermore, directional terms mentioned in the embodiments, such as "up," "down," "left," "right," "front," "back," "center," "inner," "outer," "near," and "farthest," indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. These are used solely 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.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features.

[0033] In this invention, unless otherwise explicitly specified and limited, terms such as "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] Existing compressed air energy storage systems suffer from low energy conversion efficiency, primarily because the continuously rising gas temperature inside the cylinder during gas pressurization necessitates increased compressor work, and the heat generated by the compressor is directly dissipated, resulting in energy loss. For salt cavern gas storage facilities, which are maintained at a relatively low, constant temperature similar to the Earth's surface year-round, and where leaching extraction leaves significant moisture residue at the bottom, the high-pressure gas mixed with water droplets continuously cools as it performs work in the expander. At lower flow rates, this cooling can cause ice crystals to condense, damaging the expander blades. Therefore, this invention provides a high-efficiency compressed air energy storage system based on salt cavern gas storage.

[0035] Specifically, such as Figure 1As shown, the high-efficiency compressed air energy storage system based on salt cavern gas storage of the present invention mainly includes a compressor 11, which is driven by its motor 12 when working; the compressor 11 is connected to the inlet of the salt cavern 33 through a first pipeline 55, a first steam-water separator 43 is provided on the first pipeline 55, the gas port of the first steam-water separator 43 is connected to the first pipeline 55, the upper end of the first steam-water separator 43 is the separated water outlet, the separated water outlet of the first steam-water separator 43 is connected to a water sprayer 42, and the compressed air dried by the first steam-water separator 43 is introduced into the salt cavern 33 for storage; the water sprayer 42 is connected to the controller 41 through a line, and the water sprayer 42 is also connected to the compressor 11, which can spray water mist into the cylinder of the compressor 11.

[0036] A compressed air outlet is provided on the right side of the salt cavern 33. The compressed air outlet of the salt cavern 33 is connected to the air inlet of the expander through the second pipeline 56. A second steam-water separator 44 and a dryer 45 are arranged sequentially along the airflow direction on the second pipeline 56. The upper end of the second steam-water separator 44 is the separated water outlet. The separated water outlet of the second steam-water separator 44 is connected to the water filter 46 through a pipeline. The upper end of the water filter 46 is the purified water outlet. The purified water outlet of the water filter 46 is connected to the water sprayer 42 through a pipeline. The air outlet of the expander 21 is directly vented into the atmosphere. The expander 21 is connected to the generator 22 through a line.

[0037] The heat exchange circulation interface of compressor 11 is connected to the hot side of cooler 51. The heat exchange medium on the hot side of cooler 51 circulates internally between compressor 11 and the hot side of cooler 51. The heat exchange medium on the cold side of cooler 51 exits from the cold side outlet of cooler 51 through a pipeline and enters heat accumulator 53. The outlet of heat accumulator 53 is connected to the hot side inlet of reheater 52 through a pipeline. The heat exchange medium flowing out from the hot side of reheater 52 enters cold accumulator 54 through a pipeline for storage. The heat exchange medium exiting from the outlet of cold accumulator 54 continues to enter the cold side of cooler 51 to absorb heat. In this way, the heat exchange medium circulates between cooler → heat accumulator → reheater → cold accumulator → cooler. The heat exchange medium on the cold side of reheater 52 circulates internally between expander 21 and reheater 52 to heat the expanding gas in expander 21.

[0038] When the high-efficiency compressed air energy storage system based on salt cavern gas storage is applied, the specific working process during energy storage and release is as follows:

[0039] During energy storage, the surplus electricity delivered by the front-end power grid drives the motor 12 to work. The motor 12 drives the compressor 11 to pressurize the ambient air. The high-temperature and high-pressure air compressed by the compressor 11 is stored in the salt cavern 33. During the energy release phase, the high-pressure air in the salt cavern 33 drives the expander 21 to do work. The expander 21 drives the generator to generate electricity. The generator outputs electrical energy and connects it to the user's power grid.

[0040] Specifically, during the energy storage phase, when the compressor 11 is running, it adopts a water spray wet compression method. During this process, the water spray volume of the water sprayer 42 is adjusted in real time by the controller 41 according to the input power of the motor 12, so that the water sprayed into the compressor 11 by the water sprayer 42 can be quickly evaporated during the gas compression process, so as to prevent the remaining droplets from corroding and damaging the compressor blades. In addition, the water absorbs heat during the vaporization process, so that the temperature inside the cylinder of the compressor 11 is reduced to a certain extent.

[0041] The high-temperature and high-pressure gas from the exhaust end of the compressor 11 flows to the salt cavern 33 through the first pipeline 55. During the flow, liquid water is continuously condensed in the first pipeline 55. Therefore, the high-pressure gas needs to pass through the first steam-water separator 43 to remove water before being injected into the salt cavern. The first steam-water separator 43 is usually a mechanical steam-water separator. The high-pressure air with water removed is injected into the salt cavern 33 for storage. The water separated by the first steam-water separator 43 is returned to the water sprayer 42 for recycling.

[0042] During the energy storage process, the compressor 11 generates a large amount of heat when it runs. The heat generated by the compressor 11 during the compression process is absorbed by the hot side of the cooler 51. The hot side of the cooler 51 transfers the absorbed heat to the cold side of the cooler 51. The cold side of the cooler 51 stores the absorbed heat in the heat accumulator 53. The combined action of the cooler 51 and the water sprayer 42 can basically enable the compressor 11 to operate at an isothermal temperature, which greatly improves the compressor efficiency.

[0043] Salt cavern 33 is usually isothermal with the stratum, maintaining a temperature of 20-35°C year-round. The high-pressure gas discharged from compressor 11 usually has a high temperature, and even after cooling, its temperature will remain at around 40°C. After this high-pressure gas is injected into salt cavern 33, it will gradually decrease to around 25°C. The cooled gas will continue to release some moisture, which will mix with the moisture that was originally present in the salt cavern.

[0044] During energy release, high-pressure gas flows out of the salt cavern 33. This high-pressure gas disturbs the water layer during its flow, carrying water droplets from the salt cavern with it. The mixed flow exiting the salt cavern first passes through a second steam-water separator 44 to remove liquid water, and then passes through a dryer 45 to remove water vapor from the high-pressure air. The water removed in the second steam-water separator 44 is then filtered through a water filter 46 to remove impurities before being recycled back into the water sprayer 42.

[0045] After the high-pressure air undergoes preliminary separation of liquid water in the second steam-water separator 44, it enters the dryer 45 for further drying. The selected dryer 45 preferentially uses drying materials such as quicklime, and the applied reaction is exothermic, which avoids further cooling of the gas. After dehydration and drying, the high-pressure gas contains almost no moisture. When passing through the expander 21, even at a low flow rate, there will be no further low-temperature condensation of water droplets or ice crystals.

[0046] High-pressure air expands and does work in expander 21, which drives generator 22 to generate electricity, which is then fed into the user's power grid. After the high-pressure air does work in expander 21, its temperature continuously decreases. At this time, the heat exchange medium in heat accumulator 53 is introduced into the hot side of reheater 52 to heat the cold side of reheater 52. After absorbing heat, the cold side of reheater 52 enters expander 21 and heats the expanding gas in expander 21, increasing the gas temperature and thus improving the efficiency of expander 21. At the same time, the temperature of the heat exchange medium that releases heat in the hot side of reheater 52 decreases, and it then enters cold accumulator 54 for storage, to be used for subsequent cooling of compressor 11.

[0047] As can be seen from the above scheme, the present invention has the following characteristics: 1. The high-efficiency compressed air energy storage system provided by the present invention is suitable for salt cavern gas storage. Salt caverns contain residual moisture and are maintained at 20-35℃ year-round, causing the stored high-temperature, high-pressure gas to continuously release moisture. This moisture can then be carried along with the gas as it flows out, potentially damaging the expander. The system of the present invention cleverly utilizes the water-storing characteristic of salt caverns to provide storage space for the water droplets released after water compression, enabling the application of "wet compression" in the energy storage system. Furthermore, the subsequent water removal and drying processes ensure the safe operation of the expander, thereby improving the overall economy and reliability of the system.

[0048] 2. This compressed air energy storage system utilizes the dual effects of water spray "wet compression" and a cooler to achieve near-isothermal operation of the compressor, and uses the recovered waste heat from the compressor to heat the gas in the expander, which can greatly improve the system's efficiency and economic benefits.

[0049] 3. In this compressed air energy storage system, the water separated from the salt cavern is separated and recovered at the inlet end, and the water droplets entrained are removed and dried at the exhaust end of the salt cavern. The water in the two steam-water separators is returned to the water sprayer in the compressor. In this way, the water in the entire system can be effectively recycled, and the water content in each part is almost in a balanced state, ensuring the stability of the system.

Claims

1. A high efficient compressed air energy storage method based on salt cavern gas storage, characterized in that, The method is carried out by using a high-efficiency compressed air storage system based on salt cavern gas storage, which comprises a compressor (11), a water sprayer (42), a first water-gas separator (43), a salt cavern (33), an expansion power module and a waste heat utilization circulation system, the water sprayer (42) is used for spraying water mist into the cylinder of the compressor (11); The compressed air outlet of the compressor (11) is communicated with the inlet of the salt cavern (33) through a first pipeline (55), the first water-gas separator (43) is arranged on the first pipeline (55), the outlet of the salt cavern (33) is connected with the air inlet of the expansion power module through a second pipeline (56), and the second pipeline (56) is sequentially provided with a second water-gas separator (44) and a dryer (45) along the air flow direction; The heat exchange circulation interfaces of the compressor (11) and the expansion power module are connected with the waste heat utilization circulation system; The separated water outlets of the first water-gas separator (43) and the second water-gas separator (44) are connected with the water sprayer (42), and a water filter (46) is arranged on the pipeline, through which the second water-gas separator (44) is connected with the water sprayer (42); The high-efficiency compressed air storage system based on salt cavern gas storage further comprises a controller (41), which is connected with the water sprayer (42) and the motor (12) of the compressor (11), and is used for controlling the water sprayer (42) to adjust the water spraying amount in real time according to the input power of the motor (12), so that the water spraying amount of the water sprayer (42) cannot be higher than the evaporation amount of the water in the cylinder of the compressor (11) in the gas compression process; The dryer (45) is a dryer capable of generating heat during dehydration; The drying agent in the dryer (45) is quicklime; The expansion power module adopts an expander (21); There is residual water in the salt cavern, and the temperature in the salt cavern is 20-35 ℃; The high-efficiency compressed air storage method based on salt cavern gas storage comprises: The energy storage stage: the surplus electric energy of the power grid is used to drive the compressor (11) to work, the compressor (11) compresses air, and the compressed air is transported to the salt cavern (33) through the first pipeline (55) for storage, and the first water-gas separator (43) separates water and gas of the compressed air flowing through the first pipeline (55); when the compressor (11) is running, the water sprayer (42) sprays water mist into the cylinder of the compressor (11), and the sprayed water mist evaporates in the process of air compression in the compressor (11), so that the temperature in the cylinder of the compressor (11) is reduced; the waste heat utilization circulation system cools the compressor (11) and stores the absorbed heat; The energy release stage: the compressed air in the salt cavern (33) enters the expansion power module through the second pipeline (56) and does work outside; the compressed air is sequentially separated by the second water-gas separator (44) and dried by the dryer (45) when flowing in the second pipeline (56); the waste heat utilization circulation system heats the expanded gas of the expansion power module; In the energy storage stage, the heat generated during the compression of the compressor (11) is led out through the heat exchange medium circulating in the hot side of the cooler (51), the heat exchange medium in the cold accumulator (54) flows through the cold side of the cooler (51) and absorbs the heat of the hot side of the cooler (51), and then enters the heat accumulator (53) for storage; In the energy release stage, the heat exchange medium in the heat accumulator (53) flows through the hot side of the reheater (52), the heat exchange medium on the cold side of the reheater (52) absorbs the heat of the hot side of the reheater (52), then heats the expanded gas of the expansion work module, and the heat exchange medium on the hot side of the reheater (52) is cooled and enters the cold accumulator (54) for storage.

2. The highly efficient compressed air energy storage method based on salt cavern gas storage according to claim 1, characterized in that, It also includes a generator (22), which is connected with the expander (21).

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