A new type of compressed air energy storage system

Abstract

The present invention discloses a novel compressed air energy storage system, which includes a constant-pressure diaphragm gas storage tank, an air compression and energy release subsystem, and a working fluid gas-liquid conversion subsystem. The advantages are as follows: two energy storage media are adopted, with air as the main medium for compression and expansion power generation, while the working fluid gas is used as a medium with stable pressure and does not participate in work. Through the contraction / expansion of the air film, the alternation of the two media, namely air and working fluid gas in the tank, is completed, achieving the voltage stabilization effect in the two stages of energy storage and energy release; air is used for compression and expansion power generation at the energy storage and energy release ends. Compared with the traditional carbon dioxide energy storage, the large carbon dioxide gas storage tank at the low-pressure end of the traditional carbon dioxide energy storage is eliminated and replaced by inexhaustible air, which is also directly discharged into the atmosphere during the energy release stage, greatly reducing the equipment cost and medium cost at the low-pressure gas storage end.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and specifically relates to a novel compressed air energy storage system. Background Art

[0002] Compressed air energy storage technology is a physical energy storage technology that uses compressed air to store energy. It has the advantages of large energy storage capacity, high safety, economic environmental protection, and mature technology, and plays an important role in the future energy system, especially in promoting the utilization of renewable energy and improving the stability of the power grid.

[0003] Carbon dioxide energy storage (CES) technology is a novel physical energy storage technology based on compressed air energy storage (CAES) and Brayton power generation cycle. As a new technology, in the existing technology applications, during the low electricity price period, multi-stage compressors are used to convert atmospheric gaseous carbon dioxide into high-pressure liquid carbon dioxide, and the electrical energy is stored in the form of the internal energy of carbon dioxide; during the peak electricity consumption period, multi-stage expanders are used to expand the high-pressure liquid carbon dioxide into atmospheric gaseous carbon dioxide for power generation, ultimately realizing the storage and release of electrical energy. However, this system has some disadvantages: ① The equipment investment is huge. The whole system includes parts such as a low-pressure gas storage tank, a high-pressure storage tank, a compressor unit, a turbine unit, a heat exchange system, and a large number of cold and heat storage tanks. Especially the low-pressure gas storage tank, which stores carbon dioxide at atmospheric pressure. Taking a 10MW carbon dioxide energy storage system as an example, its low-pressure gas storage tank will reach 1 million cubic meters, which will be a huge land cost in developed areas. The investment cost of these systems will be very large, and the technology promotion cost cannot be ignored and needs to be improved. Summary of the Invention

[0004] One technical problem to be solved by the present application is to overcome the defects of the above related technologies, and provide an energy storage form that optimizes the low-pressure storage of a single medium in traditional carbon dioxide energy storage and compressed air energy storage, and replaces it with a novel compressed air energy storage system that combines compressed air and compressed carbon dioxide with lightweight equipment and high energy storage efficiency.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a novel compressed air energy storage system, including a constant pressure diaphragm gas pressure tank, an air compression and energy release subsystem, and a working medium gas gas-liquid conversion subsystem.

[0006] The constant pressure diaphragm gas pressure tank is divided into a first cavity and a second cavity by a gas film.

[0007] The first cavity is connected to the air compression and energy release subsystem, and the air compression and energy release subsystem is used to store compressed air into the first cavity during the energy storage stage and discharge the compressed air in the first cavity during the energy release stage.

[0008] The second cavity is communicated with the working fluid gas gas-liquid conversion subsystem, which is composed of a working fluid gas liquid storage tank, a heat exchanger V, a low-temperature heat storage tank, and a low-temperature cold storage tank; during the energy storage stage, the working fluid gas discharged from the second cavity absorbs the cold energy of the low-temperature cold storage tank through the heat exchanger V and liquefies and then flows into the working fluid gas liquid storage tank; during the energy release stage, the working fluid gas flowing out of the working fluid gas liquid storage tank absorbs the heat energy of the low-temperature heat storage tank through the heat exchanger V, gasifies, and then is discharged into the second cavity;

[0009] The pressure of the first cavity is the same as that of the second cavity.

[0010] Compared with the related technologies, the present invention has the following advantages: The present invention adopts two energy storage media. Air is used as the main medium for compressed expansion power generation, while the working fluid gas is used as a medium with stable pressure and does not participate in work. Through the contraction / expansion of the air film, the alternation of the two media of air and working fluid gas in the tank is completed, achieving the pressure stabilization effect in the two stages of energy storage and energy release; Air is used for compression and expansion power generation at the energy storage and energy release ends. Compared with traditional carbon dioxide energy storage, the large carbon dioxide gas storage tank at the low-pressure end of traditional carbon dioxide energy storage is removed and replaced with inexhaustible air, which is also directly discharged into the atmosphere during the energy release stage, greatly reducing the equipment cost, land occupation cost, and medium cost at the low-pressure gas storage end.

[0011] Preferably, the pressure in the first cavity of the constant pressure diaphragm air pressure tank is 3-15 Mpa. The constant pressure diaphragm air pressure tank reduces the occupied volume by 30-150 times compared with the atmospheric pressure air storage tank, greatly reducing the land use cost. <H

[0012] As an improvement, the pressure in the first cavity of the constant pressure diaphragm air pressure tank is 6 Mpa, the working fluid gas is carbon dioxide, and the second cavity is inside the first cavity. Utilizing the physical property that carbon dioxide liquefies at 22 °C under 6 Mpa, through the volume change generated by the gasification and liquefaction of carbon dioxide, it is used to achieve the pressure balance of the air change in the constant pressure diaphragm air pressure tank, solving the risk of high-pressure alternating pressure operation of the constant pressure diaphragm air pressure tank, thereby realizing a new energy storage mode with miniaturized equipment, lightweight equipment investment, high-quality energy storage, and more flexible and variable energy storage.

[0013] Preferably, the air compression and energy release subsystem includes an air compression component, an air energy release component, and a heat exchange cycle mechanism mainly composed of a high-temperature heat storage tank and a high-temperature cold storage tank. The heat exchange cycle mechanism is used to provide the heat energy released by the air compression component during the energy storage stage to the air energy release component during the energy release stage.

[0014] Preferably, the air compression component is composed of an air first-stage compressor, a heat exchanger I, an air second-stage compressor, and a heat exchanger II connected in sequence.

[0015] Preferably, the air energy release component is formed by connecting a heat exchanger III, an air first-stage turbine, a heat exchanger IV, and an air second-stage turbine in sequence.

[0016] Preferably, the working fluid gas gas-liquid conversion subsystem is further provided with a refrigeration compressor unit, and the refrigeration compressor unit is connected to a heat exchanger V, a low-temperature heat storage tank, and a low-temperature cold storage tank. The refrigeration compressor unit provides sufficient cold energy for carbon dioxide liquefaction and sufficient heat energy for carbon dioxide gasification.

[0017] Preferably, the refrigeration compressor unit includes a heat exchanger VII, a compressor, a heat exchanger VIII, and a throttle valve in an internal circulation. The heat exchanger VII is connected to the heat exchanger V, and the heat exchanger VIII is respectively connected to the low-temperature heat storage tank and the low-temperature cold storage tank. Description of the Drawings

[0018] Figure 1 It is a connection schematic diagram of the novel compressed air energy storage system of the present application. Detailed Embodiments

[0019] First of all, those skilled in the art should understand that these embodiments are only used to explain the technical principles of the embodiments of the present application and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments according to needs to adapt to specific application scenarios.

[0020] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0021] This preferred embodiment is a novel compressed air energy storage system as Figure 1 shown, including a constant-pressure diaphragm air tank, an air compression and energy release subsystem, and a working fluid gas gas-liquid conversion subsystem.

[0022] The constant-pressure diaphragm air tank is divided into a first cavity and a second cavity by an air film;

[0023] The first cavity is communicated with the air compression and energy release subsystem, and the air compression and energy release subsystem is used to store compressed air into the first cavity during the energy storage stage and discharge the compressed air in the first cavity during the energy release stage;

[0024] The second cavity is communicated with the working fluid gas gas-liquid conversion subsystem, and the working fluid gas gas-liquid conversion subsystem is composed of a working fluid gas storage tank, a heat exchanger V, a low-temperature heat storage tank, and a low-temperature cold storage tank; during the energy storage stage, the working fluid gas discharged from the second cavity is liquefied by absorbing the cold energy of the low-temperature cold storage tank through the heat exchanger V and then flows into the working fluid gas storage tank; during the energy release stage, the working fluid gas flowing out of the working fluid gas storage tank is gasified by absorbing the heat energy of the low-temperature heat storage tank through the heat exchanger V and then discharged into the second cavity;

[0025] The pressures in the first cavity and the second cavity are the same and remain constant. By liquefying and vaporizing the working medium gas, the volume change of the compressed air in the energy storage stage and the energy release stage is balanced. The air film deforms flexibly with the change in the storage amounts of air and the working medium gas. The corresponding volume changes in the first cavity and the second cavity cause the air film to contract / expand, keeping the air pressure in the constant-pressure diaphragm air tank constant.

[0026] Preferably, the pressure in the first cavity of the constant-pressure diaphragm air tank is 3 - 15 Mpa. The air pressure under normal conditions is 0.1 Mpa, that is, the air chamber of the constant-pressure diaphragm air tank has a reduced occupied volume by 30 - 150 times compared to the air under normal pressure.

[0027] In this embodiment, the pressure in the first cavity of the constant-pressure diaphragm air tank is 6 Mpa, the working medium gas is carbon dioxide, and the second cavity is inside the first cavity. The working medium gas storage tank is the carbon dioxide storage tank. The pressure in the carbon dioxide storage tank is also 6 Mpa, the same as the pressures in the first cavity and the second cavity of the constant-pressure diaphragm air tank. The temperature of the liquid carbon dioxide in the carbon dioxide storage tank is 22°C, which can effectively solve the risk of high-pressure alternating pressure operation of the constant-pressure diaphragm air tank.

[0028] Among them, the air compression and energy release subsystem includes an air compression component, an air energy release component, and a heat exchange and circulation mechanism mainly composed of a high-temperature heat storage tank and a high-temperature cold storage tank. The heat exchange and circulation mechanism is used to collect the heat energy released by the air compression component during the energy storage stage and supply it to the air energy release component during the energy release stage.

[0029] In this embodiment, the air compression component is mainly composed of an air first-stage compressor, heat exchanger I (marked as heat exchanger 1 in the figure), an air second-stage compressor, and heat exchanger II (marked as heat exchanger 2 in the figure) connected in sequence. The air first-stage compressor is used to absorb the air in nature and compress it to 6 Mpa. Of course, additional compressors can be added to achieve compressed air of 15 Mpa. The high-temperature heat storage tank is used to store the heat energy generated by air compression, and the temperature of the high-temperature heat storage tank is about 200°C.

[0030] In this embodiment, the air energy release component is composed of heat exchanger III (marked as heat exchanger 3 in the figure), an air first-stage turbine, heat exchanger IV (marked as heat exchanger 4 in the figure), and an air second-stage turbine connected in sequence. The air first-stage turbine is used to expand the 6-Mpa air to 0.1 Mpa and then discharge it into nature. The high-temperature heat storage tank is used to provide the heat energy required for air expansion, and the high-temperature cold storage tank is used to store the cold energy generated by air expansion.

[0031] Preferably, the working fluid gas-liquid conversion subsystem is also provided with a refrigeration compressor unit, which is connected to heat exchanger V (marked as heat exchanger 5 in the figure), a low-temperature heat storage tank, and a low-temperature cold storage tank. Of course, other heat exchange, heat storage, and refrigeration compressor systems can also be used as replacements for the refrigeration compressor unit. The temperature of the low-temperature heat storage tank is about 50 °C.

[0032] The refrigeration compressor unit includes an internally circulating heat exchanger VII (marked as heat exchanger 7 in the figure), a compressor, a heat exchanger VIII (marked as heat exchanger 8 in the figure), and a throttle valve. The heat exchanger VII is connected to heat exchanger V, and the heat exchanger VIII is respectively connected to the low-temperature heat storage tank and the low-temperature cold storage tank.

[0033] In addition, a heat exchanger VI (marked as heat exchanger 6 in the figure) is also provided between the low-temperature heat storage tank and the heat exchanger VII. The heat exchanger VI is connected and communicated with the high-temperature heat storage tank and the high-temperature cold storage tank. A pressure balance pipe is connected between the carbon dioxide liquid storage tank and the second cavity, and a normally closed valve is provided on the pressure balance pipe.

[0034] The operation process of the novel compressed air energy storage system of the present invention is as follows.

[0035] Energy storage stage: During the low electricity consumption period at night, the normal temperature and pressure air in the atmosphere is compressed by an air compressor unit to form 6 Mpa high-pressure air, which is stored in an underground constant-pressure diaphragm air pressure tank. At the same time, the heat energy generated by the compression is stored in the high-temperature heat storage tank. When there is more and more high-pressure air in the constant-pressure diaphragm air pressure tank, the 6 Mpa high-pressure gaseous carbon dioxide in the air film is discharged out of the constant-pressure diaphragm air pressure tank and liquefied through heat exchanger 5 to form 6 Mpa liquid carbon dioxide, which is stored in the carbon dioxide liquid storage tank. Finally, the process of night air energy storage and carbon dioxide liquefaction is completed.

[0036] Energy release stage: During the high electricity consumption period during the day, the 6 Mpa high-pressure gaseous air in the constant-pressure diaphragm air pressure tank expands and generates electricity through an air turbine expansion generator set, forming normal pressure gaseous air and discharging it into the atmosphere. The heat energy required during the turbine expansion process comes from the high-temperature heat storage tank, and the cold energy generated by the expansion is stored in the high-temperature cold storage tank. When there is less and less high-pressure air in the constant-pressure diaphragm air pressure tank, in order to maintain the pressure balance in the constant-pressure diaphragm air pressure tank, the 6 Mpa liquid carbon dioxide in the carbon dioxide liquid storage tank is gasified through a circulation pump and heat exchanger 5 to generate 6 Mpa gaseous carbon dioxide and return to the air film in the constant-pressure diaphragm air pressure tank. The heat energy required for gasification comes from the low-temperature heat storage tank and heat exchanger 6, and the collected cold energy is stored in the low-temperature heat storage tank. Finally, the process of daytime air energy release power generation and carbon dioxide gasification is completed.

[0037] During the carbon dioxide energy storage liquefaction and gasification processes, the refrigeration compressor unit provides sufficient cold energy for carbon dioxide liquefaction and sufficient heat energy for carbon dioxide gasification.

[0038] In this embodiment, the temperature of the high-temperature heat storage tank is higher than that of the low-temperature heat storage tank, and the temperature of the high-temperature cold storage tank is higher than that of the low-temperature cold storage tank. The temperatures of the high-temperature heat storage tank, the high-temperature cold storage tank, the low-temperature heat storage tank, and the low-temperature cold storage tank will change according to different working conditions.

[0039] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A new type of compressed air energy storage system, characterized in that, It includes a constant-pressure diaphragm air pressure tank, an air compression energy release subsystem, and a working medium gas gas-liquid conversion subsystem. The constant-pressure diaphragm air pressure tank is divided into a first cavity and a second cavity by an air film; the pressures in the first cavity and the second cavity are the same. The first cavity is connected to the air compression energy release subsystem, and the air compression energy release subsystem is used to store compressed air into the first cavity during the energy storage stage and discharge the compressed air in the first cavity during the energy release stage. The air compression energy release subsystem includes an air compression component, an air energy release component, and a heat exchange cycle mechanism mainly composed of a high-temperature heat storage tank and a high-temperature cold storage tank. The heat exchange cycle mechanism is used to provide the heat energy released by the air compression component during the energy storage stage to the air energy release component during the energy release stage. The second cavity is connected to the working medium gas gas-liquid conversion subsystem, and the working medium gas gas-liquid conversion subsystem is composed of a working medium gas liquid storage tank, a heat exchanger V, a low-temperature heat storage tank, and a low-temperature cold storage tank. The working medium gas gas-liquid conversion subsystem is also provided with a refrigeration compressor unit, and the refrigeration compressor unit is connected to the heat exchanger V, the low-temperature heat storage tank, and the low-temperature cold storage tank. The refrigeration compressor unit includes an internally circulating heat exchanger VII, a compressor, a heat exchanger VIII, and a throttle valve. The heat exchanger VII is connected to the heat exchanger V, and the heat exchanger VIII is respectively connected to the low-temperature heat storage tank and the low-temperature cold storage tank. Energy storage stage: The normal-temperature and normal-pressure air in the atmosphere is compressed by an air compressor unit to form high-pressure air and stored in the constant-pressure diaphragm air pressure tank. At the same time, the heat energy generated by the compression is stored in the high-temperature heat storage tank. When there is more and more high-pressure air in the constant-pressure diaphragm air pressure tank, the high-pressure gaseous working medium gas in the air film is discharged out of the constant-pressure diaphragm air pressure tank, absorbs the cold energy of the low-temperature cold storage tank through the heat exchanger V to be liquefied, forms liquid working medium gas, and is stored in the working medium gas liquid storage tank. Energy release stage: The high-pressure gaseous air in the constant-pressure diaphragm air pressure tank expands and generates electricity through an air turbine expansion generator set, forms normal-pressure gaseous air and is discharged into the atmosphere. The heat energy required during the turbine expansion process comes from the high-temperature heat storage tank, and the cold energy generated by the expansion is stored in the high-temperature cold storage tank. When there is less and less high-pressure air in the constant-pressure diaphragm air pressure tank, the liquid working medium gas in the working medium gas liquid storage tank is gasified by a circulating pump and the heat exchanger V to generate gaseous working medium gas and return to the air film in the constant-pressure diaphragm air pressure tank to maintain the pressure balance in the constant-pressure diaphragm air pressure tank. The heat energy required for gasification comes from the low-temperature heat storage tank, and the collected cold energy is stored in the low-temperature cold storage tank.

2. A novel compressed air energy storage system according to claim 1, characterized in that, A heat exchanger VI is also provided between the low-temperature heat storage tank and the heat exchanger VII, and the heat exchanger VI is connected to the high-temperature heat storage tank and the high-temperature cold storage tank. The heat energy required for gasification during the energy release stage comes from the low-temperature heat storage tank and the heat exchanger VI.

3. A novel compressed air energy storage system according to claim 1 or 2, characterized in that, The pressure in the first cavity of the constant-pressure diaphragm air pressure tank is 3 - 15 Mpa.

4. A novel compressed air energy storage system according to claim 3, characterized in that, The pressure in the first cavity of the constant-pressure diaphragm air pressure tank is 6 Mpa, the working medium gas is carbon dioxide, and the second cavity is inside the first cavity.

5. A novel compressed air energy storage system according to claim 1 or 2, characterized in that, The air compression component is sequentially composed of an air first-stage compressor, a heat exchanger I, an air second-stage compressor, and a heat exchanger II.

6. A novel compressed air energy storage system according to claim 1 or 2, characterized in that, The air energy release component is composed of a heat exchanger III, an air first-stage turbine, a heat exchanger IV, and an air second-stage turbine connected in sequence.

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