Compressed air energy storage system

Abstract

The utility model discloses a compressed air energy storage system, and relates to the technical field of novel energy storage. The compressed air energy storage system comprises a preheater and an expansion unit, the expansion unit comprises at least two stages of expansion machines, an inlet of each stage of expansion machine is provided with a reheater, and the preheater and all the reheaters use heat exchangers; hot side inlets of all the reheaters communicate with an outlet of the hot water tank, and hot side outlets of all the reheaters converge and then converge into a hot side inlet of the preheater; the high-temperature heat storage medium in the hot water tank is used for heating compressed air entering the expansion machine in a gradient mode through the preheater and all the reheaters. The compressed air energy storage system solves the technical problem that the temperature of the compressed air at the inlet of the expansion machine of the compressed air energy storage system in the prior art is low, and has the technical effects of improving the temperature of the compressed air at the inlet of the expansion machine and improving the efficiency of the expansion machine.

Description

Technical Field

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

[0002] Long-duration, large-scale energy storage refers to energy storage technologies capable of storing electrical energy and continuously releasing it for more than four hours. These technologies play a crucial role in building new power systems, achieving energy transition, and addressing climate change. Megawatt-scale compressed air energy storage technology, with its advantages of large scale, high efficiency, cost-effectiveness, and environmental friendliness, has become an important direction for the development of long-duration, large-scale energy storage technologies.

[0003] Those skilled in the art have discovered that for compressed air energy storage systems, increasing energy density can improve energy storage efficiency, while decreasing the temperature of the gas stored in the storage tank can increase energy density. However, lowering the temperature of the gas stored in the storage tank results in lower temperatures of the compressed air entering the expander inlet during expansion. These problems are more pronounced in large-scale compressed air energy storage systems with large-volume storage tanks. Low expander inlet temperatures can reduce expansion power generation efficiency, and in severe cases, lead to ice blockage in the expander pipeline, causing accidents and affecting the expander's lifespan and stability. Utility Model Content

[0004] The purpose of this invention is to provide a compressed air energy storage system to solve the above-mentioned problems.

[0005] To achieve this objective, a compressed air energy storage system is provided, comprising a preheater and an expander unit. The expander unit includes at least two stages of expanders, each stage having a reheater at its inlet. The preheater and all the reheaters utilize heat exchangers. The hot-side inlets of all the reheaters are connected to the outlet of a hot water tank, and the hot-side outlets of all the reheaters merge and flow into the hot-side inlet of the preheater. The cold-side inlet of the preheater is connected to the outlet of a gas storage tank, and the cold-side outlet of the preheater is connected to the cold-side inlet of the reheater before the inlet of the first-stage expander. The compressed air entering the expander is heated by the high-temperature heat storage medium in the hot water tank through the preheater and all the reheaters.

[0006] Furthermore, the cold-side outlet of each reheater is connected to the corresponding expander inlet, and the compressed air entering each stage expander is heated by the high-temperature heat storage medium in the hot water tank through each reheater.

[0007] Furthermore, the hot-side outlet of the preheater is connected to the inlet of the cold water tank.

[0008] Furthermore, it also includes a compressor unit, which includes at least two stages of compressors, and each stage of the compressor is equipped with a regenerator at its outlet; the compression heat of the compressor unit is recovered by using a low-temperature heat storage medium in the cold water tank through all the regenerators, and the compression heat is stored in the hot water tank in the form of a high-temperature heat storage medium.

[0009] Furthermore, the hot-side inlet of each of the regenerators is connected to the outlet of the corresponding compressor, and the hot-side outlet of each of the regenerators is connected to the inlet of the next-stage compressor; the cold-side inlet of the regenerator is connected to the outlet of the cold water tank, and the cold-side outlet of the regenerator is connected to the inlet of the hot water tank.

[0010] Furthermore, the heat storage medium is water.

[0011] One of the above technical solutions has the following advantages or beneficial effects:

[0012] The compressed air energy storage system of this embodiment includes a preheater and an expander unit. The expander unit includes at least two stages of expanders, and each stage of expander is equipped with a reheater at its inlet. The hot-side inlets of all reheaters are connected to the outlet of the hot water tank, and the hot-side outlets of all reheaters merge and flow into the hot-side inlet of the preheater. The cold-side inlet of the preheater is connected to the outlet of the gas storage tank, and the cold-side outlet of the preheater is connected to the cold-side inlet of the reheater before the inlet of the first-stage expander.

[0013] The compressed air energy storage system of this embodiment includes a preheater and at least two reheaters installed on the compressed air pipeline at the outlet of the gas storage tank to heat the low-temperature compressed air flowing out of the gas storage tank. The heat from the preheater and reheaters comes from the compression heat recovered by the regenerator in the energy storage stage, which is stored in a hot water tank. By utilizing the high-temperature heat storage medium in the hot water tank through the preheater and all reheaters, the temperature of the compressed air entering the expander inlet is increased, thereby improving the efficiency of the expander and avoiding accidents caused by excessively low expander inlet temperature. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure and flow of the compressed air energy storage system in Example 1.

[0015] In the diagram: 111 - First-stage compressor; 112 - Second-stage compressor; 121 - First-stage regenerator; 122 - Second-stage regenerator; 211, 221 - Circulation pumps; 210 - Cold water tank; 220 - Hot water tank; 331 - Preheater; 321 - First-stage reheater; 311 - First-stage expander; 312 - Second-stage expander; 322 - Second-stage reheater; 400 - Gas storage tank; 410 - Gas storage tank outlet valve; 13 - Electric motor; 14 - Generator. Detailed Implementation

[0016] To make the technical problems solved by this utility model, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of this utility model will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0017] The compressed air energy storage system provided in this embodiment can be used for long-term, large-scale energy storage, belonging to the megawatt-level compressed air energy storage technology. It includes an energy storage phase and an energy release phase, with the energy release time reaching over 6 hours. During the energy storage phase, when the grid load is low or there is a power surplus, electrical energy is used to drive the compressor to compress air into a high-pressure state, which is then sealed and stored in a high-pressure air storage tank for use in the subsequent energy release phase.

[0018] The compressed air energy storage system provided in this embodiment includes a compressor unit, which includes at least two stages of compressors and can be driven by off-peak electricity.

[0019] Each stage compressor outlet is equipped with a regenerator, which can be any type of heat exchanger currently available. The compressor unit's compression heat is recovered through all regenerators using the low-temperature heat storage medium in the cold water tank, and stored in the hot water tank as a high-temperature heat storage medium. For ease of description, the hot water tank, cold water tank, and their corresponding pipes, pumps, and valves are referred to as heat storage units. The hot water tank stores the high-temperature heat storage medium, and the cold water tank stores the low-temperature heat storage medium. In this embodiment, water is used as the heat storage medium. Water has a very high specific heat capacity, enabling it to store and release a large amount of heat per unit mass. Furthermore, water is an inexpensive and widely available resource; using water as the heat storage medium can reduce system costs.

[0020] During the energy storage phase, the air pressure increases after being compressed by the compressor. Simultaneously, as the air is compressed, the distance between gas molecules decreases, and the average kinetic energy of the molecules increases, leading to an increase in gas temperature and generating heat of compression. In this embodiment of the compressed air energy storage system, each stage compressor outlet is equipped with a regenerator. The regenerator recovers the heat of compression generated after air compression and stores it in a hot water tank. Specifically, the hot-side inlet of the regenerator at the outlet of each stage compressor is connected to the outlet of that stage compressor, and the hot-side outlet of the regenerator is connected to the inlet of the next stage compressor or to the air storage tank. The cold-side inlet of the regenerator is connected to the outlet of the cold water tank, and the cold-side outlet of the regenerator is connected to the inlet of the hot water tank. Inside the regenerator, the low-temperature heat storage medium (hereinafter referred to as cold water) at the cold-side inlet exchanges heat with the high-temperature compressed air at the hot-side inlet, and the cold water carries the compressed heat away to the hot water tank. At the end of the energy storage phase, the heat storage medium in the hot water tank has absorbed the heat of compression from all the compressors in the compressor unit. The compressor units of a 100-megawatt compressed air storage system typically have at least 6 stages. The heat of compression of the first few compressor stages is less than that of the later compressor stages. Since all the heat of compression in the compressor unit is stored in the hot water tank, the heat storage temperature in the hot water tank can approach 100°C at the end of the energy storage phase, while the temperature of the compressed air stored in the air storage tank can approach 0°C.

[0021] Figure 1 This diagram illustrates an implementation of a compressed air energy storage system comprising a two-stage compressor unit. Each stage of the compressor unit has a regenerator at its outlet, resulting in two stages of regenerators. At the start of the energy storage phase, the electric motor 13 uses off-peak electricity to drive the compressor unit. Air enters the inlet of the first-stage compressor, where it is compressed, increasing in temperature and pressure. The compressed air from the outlet of the first-stage compressor 111 enters the hot side of the first-stage regenerator 121. The circulation pump 211 at the outlet of the cold water tank 210 is activated, allowing the low-temperature heat storage medium in the cold water tank to enter the cold side of the first-stage regenerator. The cold-side outlet of the first-stage regenerator is connected to the inlet of the hot water tank 220, storing the heat of compression from the first-stage compressor 111 in the hot water tank 220. The compressed air flowing from the hot-side inlet of the first-stage regenerator 121 enters the inlet of the second-stage compressor 112. After recovering the heat of compression through the second-stage regenerator 122, the compressed air enters the air storage chamber 400 from the hot-side outlet of the second-stage regenerator 122. After the energy storage phase is completed, the low-temperature high-pressure air is stored in the gas storage tank 400, and the heat of compression is stored in the hot water tank 220.

[0022] The compressed air energy storage system in this embodiment also includes an expander unit, which comprises at least two stages of expanders. Each expander stage has a reheater at its inlet; the reheater can be any type of heat exchanger currently available. The hot-side inlet of each reheater is connected to a hot water tank, and the cold-side outlet of each reheater is connected to the corresponding expander inlet. During energy release, hot water from the hot water tank enters the hot side of each reheater through pipelines. The cold side of each reheater is compressed air. Each reheater uses the high-temperature heat storage medium in the hot water tank to heat the compressed air entering each expander stage. The system also includes a preheater, which can also be any type of heat exchanger currently available. The hot-side outlet pipelines of all reheaters converge and flow into the hot-side inlet of the preheater; that is, the hot-side inlet of the preheater is connected to the hot-side outlets of all reheaters, and the water flowing out from the hot side of each reheater flows into the hot-side inlet of the preheater. The cold-side inlet of the preheater is connected to the outlet of the gas storage tank. The cold-side inlet of the preheater is low-temperature compressed air. The cold-side outlet of the preheater is connected to the cold-side inlet of the first-stage reheater. The cold-side outlet of the first-stage reheater is connected to the inlet of the first-stage expander.

[0023] Therefore, in this embodiment of the compressed air energy storage system, during energy release, the circulation pump of the hot water tank is turned on, and the hot water enters the hot side of each reheater. After flowing out from the hot side of each reheater, the hot water merges and enters the hot side of the preheater. The outlet valve of the gas storage tank is opened, and the low-temperature compressed air in the gas storage tank enters the cold side of the preheater. The preheater uses all the waste heat of the reheater to heat the low-temperature compressed air flowing out of the gas storage tank, which is the first heating of the compressed air entering the first-stage expander. Usually, the temperature of the compressed air after the first heating can reach above 30°C. The compressed air flowing out from the cold side of the preheater enters the cold side of the reheater before the inlet of the first-stage expander. The first-stage reheater uses the hot water inside the hot water tank to further heat the compressed air. The temperature of the compressed air in the reheater can be heated to close to the temperature of the hot water in the hot water tank, usually close to 100°C. At this time, the temperature of the compressed air entering the inlet of the first-stage expander can make the expander reach the optimal operating state, that is, the high-efficiency operating point. The hot-side outlet of the preheater is connected to the inlet of the cold water tank. After flowing out of the hot-side outlet of the preheater, it enters the cold water tank for storage and can be used to recover compression heat during the energy storage stage. In this embodiment, the high-temperature heat storage medium in the hot water tank is utilized in stages through the preheater and all reheaters. After being utilized in stages, the high-temperature heat storage medium in the hot water tank becomes a low-temperature heat storage medium, which is stored in the cold water tank for use by the reheater to recover compression heat during energy storage.

[0024] Figure 1The diagram illustrates an implementation of a system expander unit comprising a two-stage expander. Upon initial energy release, the circulation pump 221 of the hot water tank is activated, allowing hot water from the tank to enter the hot side of each reheater. The hot water then flows out from the hot side outlet of each reheater and converges before entering the hot side of the preheater 331. The outlet valve 410 of the gas storage tank is opened, allowing low-temperature compressed air flowing from the gas storage tank to enter the cold side of the preheater 331, where it is first heated. The compressed air then flows out from the cold side of the preheater 331 and enters the cold side of the first-stage reheater 321, where it is heated again. The reheated compressed air then flows out from the cold side of the first-stage reheater 321 and enters the inlet of the first-stage expander 311, where it drives the expander unit to generate electricity. The compressed air exiting the first-stage expander 311 experiences a decrease in pressure and temperature, entering the cold side of the second-stage reheater 322. After being heated by the hot side of the second-stage reheater 322, the compressed air enters the inlet of the second-stage expander, where it expands and performs work. During the energy release phase, the expander unit drives the generator 34 to generate electricity. Long-term, large-scale compressed air energy storage expander units typically have six or more stages. As mentioned above, after passing through six or more reheaters and expanders, the compressed air pressure approaches atmospheric pressure and can be directly discharged into the atmosphere.

[0025] The compressed air energy storage system of this embodiment includes a preheater and at least two reheaters installed on the compressed air pipeline at the outlet of the gas storage tank to heat the low-temperature compressed air flowing out of the gas storage tank. The heat from the preheater and reheaters comes from the compression heat recovered by the regenerator in the energy storage stage, which is stored in a hot water tank. By utilizing the high-temperature heat storage medium in the hot water tank through the preheater and all reheaters, the temperature of the compressed air entering the expander inlet is increased, thereby improving the efficiency of the expander and avoiding accidents caused by excessively low expander inlet temperature.

[0026] Moreover, in large-scale compressed air energy storage systems with large-capacity gas storage tanks, the compressor units have many stages, a lot of compression heat, and a lot of heat in the hot water tank. Therefore, the temperature of the compressed air after being heated by the preheater and all the reheaters can always be kept at a high level, so that the temperature of the compressed air entering the expander inlet can be kept at a high level for a long time, enabling the expander unit to continuously expand and generate electricity, thus achieving long-term energy storage.

[0027] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" 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. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0028] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0029] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A compressed air energy storage system, characterized in that, It includes a preheater and an expander unit, the expander unit includes at least two stages of expanders, each stage of the expander is provided with a reheater at its inlet, and the preheater and all the reheaters use heat exchangers; All the hot-side inlets of the reheaters are connected to the outlet of the hot water tank, and the hot-side outlets of all the reheaters merge and flow into the hot-side inlet of the preheater; the cold-side inlet of the preheater is connected to the outlet of the gas storage tank, and the cold-side outlet of the preheater is connected to the cold-side inlet of the reheater before the inlet of the first-stage expander; the compressed air entering the expander is heated by the high-temperature heat storage medium in the hot water tank through the preheaters and all the reheater stages.

2. The compressed air energy storage system according to claim 1, characterized in that, The cold-side outlet of each reheater is connected to the corresponding expander inlet, and the compressed air entering each stage expander is heated by the high-temperature heat storage medium in the hot water tank through each reheater.

3. The compressed air energy storage system according to claim 1, characterized in that, The hot-side outlet of the preheater is connected to the inlet of the cold water tank.

4. The compressed air energy storage system according to claim 3, characterized in that, It also includes a compressor unit, which includes at least two stages of compressors, and each stage of the compressor is equipped with a regenerator at its outlet; The compressor unit's compression heat is recovered by all of the regenerators using a low-temperature heat storage medium in the cold water tank, and the compression heat is stored in the hot water tank in the form of a high-temperature heat storage medium.

5. The compressed air energy storage system according to claim 4, characterized in that, The hot-side inlet of each of the regenerators is connected to the outlet of the corresponding compressor, and the hot-side outlet of each of the regenerators is connected to the inlet of the next-stage compressor; the cold-side inlet of the regenerator is connected to the outlet of the cold water tank, and the cold-side outlet of the regenerator is connected to the inlet of the hot water tank.

6. The compressed air energy storage system according to any one of claims 1-5, characterized in that, The heat storage medium is water.

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