Low-energy-consumption double-medium compressed air energy storage system

Abstract

The invention discloses a low-energy-consumption double-medium compressed air energy storage system, which is characterized in that compressed air is used as a main medium for electricity compression energy storage / expansion energy release power generation, and carbon dioxide is used as a pressure stabilizing medium and does not participate in acting; when the compressed air in the first cavity is discharged in the energy release stage, the high-pressure carbon dioxide in the second cavity is heated by the carbon dioxide stable compression and release subsystem to reduce the density so as to enlarge the occupied volume, and the high-pressure carbon dioxide in the second cavity is cooled by the carbon dioxide stable compression and release subsystem to reduce the density; the volume of the carbon dioxide is scaled up and down, alternation of air and the carbon dioxide in the tank is completed through gas film shrinkage / expansion, and the pressure stabilizing effect of the two stages of energy storage and energy release is achieved; a large carbon dioxide storage bin at a traditional carbon dioxide energy storage low-pressure end is removed and replaced with inexhaustible air in the natural world, the air can be directly discharged into the atmosphere in the energy release stage, and the equipment cost and the occupied space cost of the low-pressure air storage end are saved.

Description

Technical Field

[0001] The invention relates to the technical field of energy storage systems, and in particular to a low-energy consumption dual-medium 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, economy, environmental protection and mature technology. It plays an important role in the future energy system, especially in promoting the use of renewable energy and improving the stability of the power grid.

[0003] Carbon dioxide energy storage (CES) technology is a new physical energy storage technology based on compressed air energy storage (CAES) and Brayton power generation cycle. As a new technology, carbon dioxide energy storage uses a multi-stage compressor to convert atmospheric pressure gaseous carbon dioxide into high-pressure liquid carbon dioxide during the low electricity price period, and converts electrical energy into the form of carbon dioxide internal energy for storage; during the peak period of electricity consumption, the high-pressure liquid carbon dioxide is expanded and converted into atmospheric pressure gaseous carbon dioxide through a multi-stage expander to generate electricity, and finally realize the storage and release of electrical energy. However, this system has some disadvantages: ① Huge equipment investment. The whole system consists of low-pressure gas storage warehouse, high-pressure storage tank, compressor unit, turbine unit, heat exchange system and a large number of cold and heat storage tanks. In particular, the low-pressure gas storage warehouse uses atmospheric pressure to store carbon dioxide. Taking a 10MW carbon dioxide energy storage system as an example, its low-pressure gas storage warehouse 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 huge, and the cost of technology promotion cannot be ignored and needs to be improved. Summary of the invention

[0004] A technical problem to be solved by the present application is to overcome the defects of the above-mentioned related technologies and provide a storage form that optimizes the traditional single-medium low-pressure storage of carbon dioxide energy storage and compressed air energy storage, and replaces it with a low-energy consumption dual-medium 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 low-energy dual-medium compressed air energy storage system, including a constant-pressure diaphragm air pressure tank and an air compression energy release subsystem, the space inside the constant-pressure diaphragm air pressure tank is divided into a first cavity and a second cavity by an air film, and the first cavity is connected to the air compression energy release subsystem; the air compression energy release subsystem is used to store compressed air into the first cavity in the energy storage stage, and to discharge the compressed air in the first cavity in the energy release stage; It also includes a carbon dioxide stabilizing compression and discharging subsystem, which is connected to the second cavity to form a carbon dioxide circulation pipeline; The carbon dioxide stabilization and compression and release subsystem is used to reduce the temperature of carbon dioxide in the second cavity during the energy storage stage to increase the density, thereby reducing the occupied volume of the second cavity; The carbon dioxide stabilizing and releasing subsystem is used to increase the temperature of carbon dioxide in the second cavity during the energy release stage to reduce the density, thereby expanding the occupied volume of the second cavity.

[0006] Compared with the related art, the present invention has the following advantages: the present invention adopts two energy storage media, compressed air is used as the main medium for electricity compression energy storage / expansion energy release and power generation, and carbon dioxide is used as a pressure-stable medium and does not participate in work. When compressed air is stored in the first cavity of the constant-pressure diaphragm air tank in the energy storage stage, the high-pressure carbon dioxide in the second cavity of the constant-pressure diaphragm air tank is cooled by the carbon dioxide stabilizing compression and release subsystem to increase the density so as to reduce the occupied volume. When the compressed air in the first cavity is discharged in the energy release stage, the high-pressure carbon dioxide in the second cavity is heated by the carbon dioxide stabilizing compression and release subsystem to reduce the density so as to expand the occupied volume. The volume expansion and contraction of carbon dioxide during the heating and cooling process completes the alternation of the two media, air and carbon dioxide, in the tank through the contraction / expansion of the gas film, thereby achieving the pressure stabilization effect in the two stages of energy storage and energy release. Compared with traditional carbon dioxide energy storage, the large carbon dioxide gas storage warehouse at the low-pressure end of traditional carbon dioxide energy storage has been eliminated and replaced by inexhaustible air in nature, which can be directly discharged into the atmosphere during the energy release stage, eliminating the equipment cost and land cost of the low-pressure gas storage end. In addition, in the process of carbon dioxide volume change, it is only a temperature change under stable pressure, and no phase change occurs. Only less energy is required to achieve volume change, which greatly reduces the energy consumption of the system operation process.

[0007] Preferably, the carbon dioxide stabilization and compression and release subsystem includes a first circulation pump, a first heat exchanger and a heat exchange component; the first circulation pump is connected to the circulation pipeline between the first heat exchanger and the second cavity, the heat exchange component is used to provide cold energy to the first heat exchanger in the energy storage stage, and the heat exchange component is used to provide heat energy to the first heat exchanger in the energy release stage. It is used to provide heat energy or cold energy in an orderly manner to increase the temperature and reduce the density of the high-pressure carbon dioxide in the second cavity to expand the volume or reduce the temperature and increase the density to reduce the volume.

[0008] Preferably, the heat exchange assembly includes a normal pressure heat storage tank and a second circulation pump connected to the first heat exchanger to form a heat cycle, as well as a normal pressure cold storage tank, a third circulation pump and a second heat exchanger; the normal pressure heat storage tank is used to provide heat energy to the first heat exchanger when the second circulation pump is working, and the normal pressure cold storage tank is used to provide cold energy to the first heat exchanger through the second heat exchanger when the third circulation pump is working. Only less energy is needed to achieve volume change, and only the normal pressure heat storage tank and the normal pressure cold storage tank need to be used, which reduces equipment costs.

[0009] Preferably, a compressor and a throttle valve are respectively provided on the medium circulation pipeline between the second heat exchanger and the first heat exchanger.

[0010] Preferably, the pressure of the compressed air in the first cavity and the carbon dioxide in the second cavity is the same as 15 MPa. Under high energy density, the occupied space of the system can be greatly reduced, and the land cost can be reduced.

[0011] Preferably, when energy storage is completed, the temperature of carbon dioxide in the second cavity is 32°C and the density is 833kg / m³; when energy release is completed, the temperature of carbon dioxide in the second cavity is 80°C and the density is 427kg / m³. Under 15Mpa, compared with the two temperatures, the density of carbon dioxide at 32°C is about twice that of carbon dioxide at 80°C, and the density difference is nearly doubled, that is, the volume of carbon dioxide at 32°C is about half of that at 80°C at the two temperatures, and the volume is reduced by nearly half when converted from 80°C to 32°C, and the volume is expanded by nearly double when converted from 32°C to 80°C. Moreover, 32°C and 80°C are normal temperatures, and only less energy is required to achieve mutual conversion, which greatly reduces the energy consumption of system operation.

[0012] Preferably, the air compression energy release subsystem includes an air compressor unit, an air turbine expansion generator unit and a heat exchange circulation mechanism mainly composed of a high-pressure heat storage tank and a high-pressure cold storage tank, the air compressor unit is connected to the air inlet of the first cavity, and the air turbine expansion generator unit is connected to the air outlet of the first cavity; the heat exchange circulation mechanism is used to provide the heat energy released by the air compressor unit in the energy storage stage to the air turbine expansion generator unit in the energy release stage.

[0013] As an improvement, the heat exchange assembly further includes a third heat exchanger, one heat exchange channel of the third heat exchanger is connected between the third circulation pump and the first heat exchanger, and another heat exchange channel of the third heat exchanger is connected between the high-pressure heat storage tank and the high-pressure cold storage tank. By releasing the stored waste heat through air compression to supply the heat required for the carbon dioxide to increase its temperature and volume, the energy consumption of the system operation can be better reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a connection diagram of the low-energy dual-medium compressed air energy storage system of the present application. DETAILED DESCRIPTION

[0015] First, those skilled in the art should understand that these implementations 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 to them as needed to adapt to specific application scenarios.

[0016] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] The preferred embodiment is as follows Figure 1 A low-energy consumption dual-medium compressed air energy storage system shown in the figure comprises a constant-pressure diaphragm air pressure tank and an air compression energy release subsystem, wherein the space inside the constant-pressure diaphragm air pressure tank is divided into a first cavity and a second cavity by an air film, wherein the first cavity is connected to the air compression energy release subsystem; the air compression energy release subsystem is used to store compressed air into the first cavity during the energy storage stage, and to discharge the compressed air in the first cavity during the energy release stage; It also includes a carbon dioxide stabilizing compression and discharging subsystem, which is connected to the second cavity to form a carbon dioxide circulation pipeline; The carbon dioxide stabilization and compression and release subsystem is used to reduce the temperature of carbon dioxide in the second cavity during the energy storage stage to increase the density, thereby reducing the occupied volume of the second cavity; The carbon dioxide stabilizing and releasing subsystem is used to increase the temperature of carbon dioxide in the second cavity during the energy release stage to reduce the density, thereby expanding the occupied volume of the second cavity.

[0018] The carbon dioxide stabilization and compression and release subsystem includes a first circulation pump, a first heat exchanger and a heat exchange component; the first circulation pump is connected to the circulation pipeline between the first heat exchanger (heat exchanger 6) and the second cavity, the heat exchange component is used to provide cold energy to the first heat exchanger during the energy storage stage, and the heat exchange component is used to provide heat energy to the first heat exchanger during the energy release stage.

[0019] The heat exchange assembly includes a normal pressure heat storage tank and a second circulation pump (circulation pump 3) connected to the first heat exchanger to form a heat cycle, as well as a normal pressure cold storage tank, a third circulation pump (circulation pump 2) and a second heat exchanger (heat exchanger 8); the normal pressure heat storage tank is used to provide heat energy to the first heat exchanger when the second circulation pump is working, and the normal pressure cold storage tank is used to provide cold energy to the first heat exchanger through the second heat exchanger when the third circulation pump is working. A compressor and a throttle valve are respectively provided on the medium circulation pipeline between the second heat exchanger and the first heat exchanger.

[0020] The pressure of the compressed air in the first cavity and the carbon dioxide in the second cavity is the same, which is 15 MPa.

[0021] When energy storage is completed, the temperature of the carbon dioxide in the second cavity is 32°C and the density is 833kg / m³; when energy release is completed, the temperature of the carbon dioxide in the second cavity is 80°C and the density is 427kg / m³.

[0022] The air compression energy release subsystem includes an air compressor unit, an air turbine expansion generator unit and a heat exchange circulation mechanism mainly composed of a high-pressure heat storage tank and a high-pressure cold storage tank. The air compressor unit is connected to the air inlet of the first cavity. The air compressor unit includes a primary compressor, a heat exchanger 1, a secondary compressor, a heat exchanger 2, a tertiary compressor and a heat exchanger 3, which are used to compress 0.1Mpa atmospheric air step by step into 15Mpa compressed air, and store heat in the high-pressure heat storage tank through the heat exchangers 1, 2 and 3; The air turbine expansion generator set is connected to the air outlet of the first cavity. The air turbine expansion generator set includes a heat exchanger 4, a first-stage turbine, a heat exchanger 5 and a second-stage turbine. The heat exchanger 4 and the heat exchanger 5 absorb the heat energy stored in the high-pressure heat storage tank during the expansion process, and gradually generate electricity to release energy. The 15Mpa compressed air is expanded into 0.1Mpa air and is directly released, and cold energy is stored in the high-pressure cold storage tank; that is, the heat exchange circulation mechanism is used to provide the heat energy released by the air compressor unit in the energy storage stage to the air turbine expansion generator set in the energy release stage.

[0023] The heat exchange assembly also includes a third heat exchanger (heat exchanger 7), one heat exchange channel of the third heat exchanger is connected between the third circulation pump and the first heat exchanger, and another heat exchange channel of the third heat exchanger is connected between the high-pressure heat storage tank and the high-pressure cold storage tank. The heat energy released by the air compressor unit in the energy storage stage is used as the main supplementary heat for heating the high-pressure carbon dioxide, which can reduce the energy consumption required by the compressor on the medium circulation pipeline.

[0024] The operation process of a low-energy consumption dual-medium compressed air energy storage system of the present invention is as follows.

[0025] Energy storage stage: During the low-peak period of electricity consumption at night, the normal temperature and pressure gaseous air in the atmosphere is compressed by the air compressor unit to form 15Mpa high-pressure gaseous air, and stored in the underground constant pressure diaphragm air tank. At the same time, the heat energy generated by the compressed air is stored in the high-pressure heat storage tank. When the high-pressure air in the constant pressure diaphragm air tank gradually increases, the 15Mpa 80℃ low-density and large-volume carbon dioxide in the air film is discharged out of the air tank, cooled by the heat exchanger 6, forming 15Mpa27℃ high-density and small-volume carbon dioxide, and returned to the air film of the constant pressure diaphragm air tank. When the nighttime air energy storage and carbon dioxide cooling and volume reduction process is finally completed, the air film contains 15Mpa 32℃ high-density and small-volume carbon dioxide.

[0026] Energy release stage: During the peak period of electricity consumption during the day, the high-pressure gaseous air in the constant-pressure diaphragm air tank passes through the heat exchanger 4 to heat the high-pressure air with the heat energy generated in the compression stage, and then the air turbine expansion generator set generates electricity, and forms normal-pressure gaseous air and releases it into the atmosphere. When the high-pressure air in the constant-pressure diaphragm air tank becomes less and less, the high-density, small-volume carbon dioxide at 15Mpa 32°C in the air film is heated through the heat exchanger 6 to form a low-density, large-volume carbon dioxide at 15Mpa 80°C, and returns to the air film of the constant-pressure diaphragm air tank. At the same time, the 80°C carbon dioxide can transfer heat to the high-pressure air through the air film, so that the high-pressure air is heated to 80°C, preheating before expansion is achieved, and improving the energy conversion efficiency. Finally, the process of air energy release and carbon dioxide temperature increase and volume expansion during the day is completed.

[0027] The above is only a specific implementation 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 a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A low-energy consumption dual-medium compressed air energy storage system, comprising a constant-pressure diaphragm air pressure tank and an air compression energy release subsystem, wherein the space inside the constant-pressure diaphragm air pressure tank is divided into a first cavity and a second cavity by an air film, and the first cavity is connected to the air compression energy release subsystem; the air compression energy release subsystem is used to store compressed air into the first cavity during the energy storage stage, and to discharge the compressed air in the first cavity during the energy release stage; It is characterized in that It also includes a carbon dioxide stabilizing compression and discharging subsystem, which is connected to the second cavity to form a carbon dioxide circulation pipeline; The carbon dioxide stabilization and compression and release subsystem is used to reduce the temperature of carbon dioxide in the second cavity during the energy storage stage to increase the density, thereby reducing the occupied volume of the second cavity; The carbon dioxide stabilizing and releasing subsystem is used to increase the temperature of carbon dioxide in the second cavity during the energy release stage to reduce the density, thereby expanding the occupied volume of the second cavity.

2. A low-energy consumption dual-medium compressed air energy storage system according to claim 1, characterized in that: The carbon dioxide stabilization and compression and release subsystem includes a first circulation pump, a first heat exchanger and a heat exchange component; the first circulation pump is connected to the circulation pipeline between the first heat exchanger and the second cavity, the heat exchange component is used to provide cold energy to the first heat exchanger during the energy storage stage, and the heat exchange component is used to provide heat energy to the first heat exchanger during the energy release stage.

3. A low-energy consumption dual-medium compressed air energy storage system according to claim 2, characterized in that: The heat exchange assembly includes a normal pressure heat storage tank and a second circulation pump connected to the first heat exchanger to form a heat cycle, as well as a normal pressure cold storage tank, a third circulation pump and a second heat exchanger; the normal pressure heat storage tank is used to provide heat energy to the first heat exchanger when the second circulation pump is working, and the normal pressure cold storage tank is used to provide cold energy to the first heat exchanger through the second heat exchanger when the third circulation pump is working.

4. A low-energy consumption dual-medium compressed air energy storage system according to claim 3, characterized in that: A compressor and a throttle valve are respectively provided on the medium circulation pipeline between the second heat exchanger and the first heat exchanger.

5. A low-energy consumption dual-medium compressed air energy storage system according to any one of claims 1 to 4, characterized in that: The pressure of the compressed air in the first cavity and the carbon dioxide in the second cavity are both 15 MPa.

6. A low-energy consumption dual-medium compressed air energy storage system according to claim 5, characterized in that: When energy storage is completed, the temperature of the carbon dioxide in the second cavity is 32°C and the density is 833kg / m³; when energy release is completed, the temperature of the carbon dioxide in the second cavity is 80°C and the density is 427kg / m³.

7. A low-energy consumption dual-medium compressed air energy storage system according to claim 6, characterized in that: The air compression energy release subsystem includes an air compressor unit, an air turbine expansion generator unit and a heat exchange circulation mechanism mainly composed of a high-pressure heat storage tank and a high-pressure cold storage tank. The air compressor unit is connected to the air inlet of the first cavity, and the air turbine expansion generator unit is connected to the air outlet of the first cavity; the heat exchange circulation mechanism is used to provide the heat energy released by the air compressor unit in the energy storage stage to the air turbine expansion generator unit in the energy release stage.

8. A low-energy consumption dual-medium compressed air energy storage system according to claim 7, characterized in that: The heat exchange assembly also includes a third heat exchanger, one heat exchange channel of the third heat exchanger is connected between the third circulation pump and the first heat exchanger, and another heat exchange channel of the third heat exchanger is connected between the high-pressure heat storage tank and the high-pressure cold storage tank.

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