New compressed air energy storage system

Abstract

The present invention discloses a new compressed air energy storage system, including a constant-pressure diaphragm pressure tank, an air compression and energy release subsystem, and a working medium gas vapor-liquid conversion subsystem. An advantage of the system is that two types of energy storage media are used, air is used as a main medium for power generation through compression and expansion, the working medium gas, as a pressure-stabilizing medium, does not participate in doing work, and an alternation between the air in the tank and the working medium gas is completed through contraction / expansion of an air film, to achieve a pressure stabilization effect in two phases of energy storage and energy release. At energy storage and release ends, air is used for power generation through compression and expansion. Compared with conventional carbon dioxide energy storage, a large carbon dioxide gas storage tank at a conventional low-pressure carbon dioxide energy storage end is removed and replaced with inexhaustible air. In the energy release phase, the air is directly discharged into the atmosphere. This greatly reduces equipment costs and medium costs at a low-pressure gas storage end.

Description

NEW COMPRESSED AIR ENERGY STORAGE SYSTEMTECHNICAL FIELD

[0001] The present invention relates to the field of energy storage system technologies, and specifically, to a new compressed air energy storage system.BACKGROUND

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

[0003] A 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 is used in the conventional technology to convert atmospheric-pressure gaseous carbon dioxide into high-pressure liquid carbon dioxide by using a multi-stage compressor in a low electricity price period, so as to convert electric energy into carbon dioxide internal energy for storage. In a peak period of power consumption, high-pressure liquid carbon dioxide is expanded into atmospheric-pressure gaseous carbon dioxide by using a multi-stage expander, so as to generate power and finally store and release electric energy. However, the system has some disadvantages: (1) High equipment investment costs. The entire system includes a low-pressure gas storage tank, a high-pressure storage tank, a compressor unit, a turbine unit, a heat exchange system, and a large quantity of cold storage and heat storage tanks. In particular, the low-pressure gas storage tank stores carbon dioxide at atmospheric pressure. A 10 MW carbon dioxide energy storage system is used as an example. A low-pressure gas storage tank thereof reaches 1 million cubic meters, which incur high land costs in developed regions. Investment costs of these systems are very high. The costs of technology promotion cannot be ignored and need to be improved.SUMMARY

[0004] A technical problem to be resolved in this application is to overcome disadvantages of the above-mentioned related technology. A new compressed air energy storage system that combines compressed air and compressed carbon dioxide and is featuring lightweight equipment and high energy storage efficiency is provided to optimize and replace conventional energy storage forms of carbon dioxide energy storage and compressed air energy storage with single medium and low pressure.

[0005] A technical solution used in the present invention to resolve the technical problem is a new compressed air energy storage system, including a constant-pressure diaphragm pressure tank, an air compression and energy release subsystem, and a working medium gas vapor-liquid conversion subsystem.

[0006] The constant-pressure diaphragm pressure tank is divided into a first cavity and a second cavity by using an air film.

[0007] The first cavity is in communication with the air compression and energy release subsystem, and the air compression and energy release subsystem is configured to: store compressed air into the first cavity in an energy storage phase, and discharge the compressed air in the first cavity in an energy release phase.

[0008] The second cavity is in communication with the working medium gas vapor-liquid conversion subsystem, and the working medium gas vapor-liquid conversion subsystem includes a working medium gas liquid storage tank, a heat exchanger V, a low-temperature heat storage tank, and a low-temperature cold storage tank; in the energy storage phase, working medium gas discharged from the second cavity is liquefied by absorbing cold energy of the low-temperature cold storage tank by using the heat exchanger V and flows into the working medium gas liquid storage tank; and in the energy release phase, working medium gas flowing out of the working medium gas liquid storage tank is vaporized by absorbing heat energy of the low-temperature heat storage tank by using the heat exchanger V and then discharged into the second cavity.

[0009] Pressure in the first cavity is the same as that in the second cavity.

[0010] Compared with the related technology, the present invention has the following advantages: In the present invention, two types of energy storage media are used, air is used as a main medium for power generation through compression and expansion, the working medium gas, as a medium for pressure stabilization, does not participate in doing work, and an alternation between the air in the tank and the working medium gas is completed through contraction / expansion of an air film, to achieve a pressure stabilization effect in two phases of energy storage and energy release. At energy storage and release ends, air is used for power generation through compression and expansion. This is different from conventional carbon dioxide energy storage. A large carbon dioxide gas storage tank at a conventional low-pressure carbon dioxide energy storage end is removed and replaced with inexhaustible air. In the energy release phase, the air is directly discharged into the atmosphere. This greatly reduces equipment costs, land costs, and medium costs at a low-pressure gas storage end.

[0011] Preferably, the pressure in the first cavity of the constant-pressure diaphragm pressure tank is 3 Mpa to 15 Mpa. An occupied volume of the constant-pressure diaphragm pressure tank is reduced by 30 to 150 times compared with an atmospheric-pressure air tank. This greatly reduces land use costs.

[0012] In an improvement, the pressure in the first cavity of the constant-pressure diaphragm pressure tank is 6 Mpa, the working medium gas is carbon dioxide, and the second cavity is inside the first cavity. Based on the physical characteristics of carbon dioxide liquefaction at 22°C at 6 Mpa, a volume change generated by carbon dioxide gasification and liquefaction is used to achieve a pressure balance of air change in the constant-pressure diaphragm pressure tank, thereby resolving a risk of high-pressure alternating pressure operation of the constant-pressure diaphragm pressure tank, and implementing equipment miniaturization, lightweight equipment investment, high-quality energy storage, and a more flexible and changeable new energy storage mode.

[0013] Preferably, the air compression and energy release subsystem includes an air compression assembly, an air energy release assembly, and a heat exchange circulation mechanism mainly composed of a high-temperature heat storage tank and a high-temperature cold storage tank, and the heat exchange circulation mechanism is configured to provide heat energy released by the air compression assembly in the energy storage phase to the air energy release assembly in the energy release phase.

[0014] Preferably, the air compression assembly is formed by sequentially connecting a first-stage air compressor, a heat exchanger I, a second-stage air compressor, and a heat exchanger II.

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

[0016] Preferably, the working medium gas vapor-liquid conversion subsystem further includes 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 provides enough cold energy for carbon dioxide liquefaction and enough heat energy for carbon dioxide gasification.

[0017] Preferably, the refrigeration compressor unit includes a heat exchanger Ⅶ for internal circulation, 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 separately connected to the low-temperature heat storage tank and the low-temperature cold storage tank.BRIEF DESCRIPTION OF DRAWINGS

[0018] FIG. 1 is a schematic diagram of a connection of a new compressed air energy storage system according to this application.DESCRIPTION OF EMBODIMENTS

[0019] First, a person skilled in the art should understand that the implementations are merely used to explain the technical principles of embodiments of this application, and are not intended to limit the protection scope of the embodiments of this application. A person skilled in the art can make an adjustment as required, so as to adapt to a specific application scenario.

[0020] The following further describes the present invention in detail with reference to the accompanying drawings and specific embodiments.

[0021] This preferred embodiment is a new compressed air energy storage system shown in FIG. 1, including a constant-pressure diaphragm pressure tank, an air compression and energy release subsystem, and a working medium gas vapor-liquid conversion subsystem.

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

[0023] The first cavity is in communication with the air compression and energy release subsystem, and the air compression and energy release subsystem is configured to: store compressed air into the first cavity in an energy storage phase, and discharge the compressed air in the first cavity in an energy release phase.

[0024] The second cavity is in communication with the working medium gas vapor-liquid conversion subsystem, and the working medium gas vapor-liquid conversion subsystem includes a working medium gas liquid storage tank, a heat exchanger V, a low-temperature heat storage tank, and a low-temperature cold storage tank; in the energy storage phase, working medium gas discharged from the second cavity is liquefied by absorbing cold energy of the low-temperature cold storage tank by using the heat exchanger V and flows into the working medium gas liquid storage tank; and in the energy release phase, working medium gas flowing out of the working medium gas liquid storage tank is vaporized by absorbing heat energy of the low-temperature heat storage tank by using the heat exchanger V and then discharged into the second cavity.

[0025] Pressure in the first cavity is the same as that in the second cavity and remains constant. A volume change of compressed air in the energy storage phase and the energy release phase is balanced by liquefaction and gasification of the working medium gas. The air film is flexibly deformed with a change of reserves of the air and the working medium gas, and a volume of the first cavity and a volume of the second cavity correspondingly change to contract / expand the air film, so that air pressure in the constant-pressure diaphragm pressure tank remains constant.

[0026] Preferably, the pressure in the first cavity of the constant-pressure diaphragm pressure tank is 3 Mpa to 15 Mpa. The atmospheric pressure is 0.1 Mpa. That is, an occupied volume of the constant-pressure diaphragm pressure tank is reduced by 30 to 150 times compared with an atmospheric-pressure air tank.

[0027] In the embodiments, the pressure in the first cavity of the constant-pressure diaphragm pressure tank is 6 Mpa, the working medium gas is carbon dioxide, and the second cavity is inside the first cavity. The working medium gas liquid storage tank is a carbon dioxide liquid storage tank. Pressure in the carbon dioxide liquid storage tank is also the same as the pressure in the first cavity and the pressure in the second cavity of the constant-pressure diaphragm pressure tank, and is 6 Mpa. A temperature of liquid carbon dioxide in the carbon dioxide liquid storage tank is 22°C. This can effectively resolve a risk of high-pressure alternating pressure operation of the constant-pressure diaphragm pressure tank.

[0028] The air compression and energy release subsystem includes an air compression assembly, an air energy release assembly, and a heat exchange circulation mechanism mainly composed of a high-temperature heat storage tank and a high-temperature cold storage tank, and the heat exchange circulation mechanism is configured to collect heat energy released by the air compression assembly in the energy storage phase and provide the heat energy to the air energy release assembly in the energy release phase.

[0029] In the embodiments, the air compression assembly is mainly formed by sequentially connecting a first-stage air compressor, a heat exchanger I (a heat exchanger 1 shown in the figure), a second-stage air compressor, and a heat exchanger II (a heat exchanger 2 shown in the figure). The first-stage air compressor is configured to absorb air in nature and compress the air to 6 Mpa. Certainly, another compressor can be added to reach compressed air with a pressure of 15 Mpa. The high-temperature heat storage tank is configured to store heat energy generated by air compression. A temperature of the high-temperature heat storage tank is about 200℃.

[0030] In the embodiments, the air energy release assembly is formed by sequentially connecting a heat exchanger III (a heat exchanger 3 shown in the figure), a first-stage air turbine, a heat exchanger IV (a heat exchanger 4 shown in the figure), and a second-stage air turbine. The first-stage air turbine is configured to expand the air with a pressure of 6 Mpa to 0.1 Mpa and then discharge the air into nature. The high-temperature heat storage tank is configured to provide heat energy required for air expansion, and the high-temperature cold storage tank is configured to store cold energy generated by air expansion.

[0031] Preferably, the working medium gas vapor-liquid conversion subsystem further includes a refrigeration compressor unit, and the refrigeration compressor unit is connected to the heat exchanger V (a heat exchanger 5 shown in the figure), the low-temperature heat storage tank, and the low-temperature cold storage tank. Certainly, the refrigeration compressor unit can also be replaced with another heat exchange, heat storage, and refrigeration compressor system. A temperature of the low-temperature heat storage tank is about 50℃.

[0032] The refrigeration compressor unit includes a heat exchanger Ⅶ (a heat exchanger 7 shown in the figure) for internal circulation, a compressor, a heat exchanger Ⅷ (a heat exchanger 8 shown in the figure), and a throttle valve, the heat exchanger Ⅶ is connected to the heat exchanger V, and the heat exchanger Ⅷ is separately connected to the low-temperature heat storage tank and the low-temperature cold storage tank.

[0033] In addition, a heat exchanger Ⅵ (a heat exchanger 6 shown in the figure) is further disposed between the low-temperature heat storage tank and the heat exchanger Ⅶ, and the heat exchanger Ⅵ is in communication with the high-temperature heat storage tank and the high-temperature cold storage tank. A pressure equalizing pipe is connected between the carbon dioxide liquid storage tank and the second cavity, and a normally-closed valve is disposed on the pressure equalizing pipe.

[0034] A running process of the new compressed air energy storage system of the present invention is as follows.

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

[0036] Energy release phase: In a peak period of power consumption at daytime, 6 Mpa high-pressure gaseous air in the constant-pressure diaphragm pressure tank is expanded to generate power by using an air turbine expansion generator unit to form atmospheric gaseous air, and the atmospheric gaseous air is discharged into the atmosphere. Heat energy required in the turbine expansion process comes from the high-temperature heat storage tank, and cold energy generated by the expansion is stored in the high-temperature cold storage tank. When there is less high-pressure air in the constant-pressure diaphragm pressure tank, to maintain pressure balance in the constant-pressure diaphragm pressure tank, 6 Mpa liquid carbon dioxide in the carbon dioxide liquid storage tank is gasified by using a circulating pump and the heat exchanger 5 to form 6 Mpa gaseous carbon dioxide, which is returned to the air film of the constant-pressure diaphragm pressure tank. Heat energy required for gasification comes from the low-temperature heat storage tank and the heat exchanger 6, and collected cold energy is stored in the low-temperature heat storage tank. The process of air energy release power generation and carbon dioxide gasification at daytime is finally completed.

[0037] In the process of carbon dioxide energy storage liquefaction and gasification, the refrigeration compressor unit provides enough cold energy for carbon dioxide liquefaction and enough heat energy for carbon dioxide gasification.

[0038] In the embodiments, the temperature of the high-temperature heat storage tank is higher than the temperature of the low-temperature heat storage tank, a temperature of the high-temperature cold storage tank is higher than a temperature of the low-temperature cold storage tank, and 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 change based on different operating conditions.

[0039] The above-mentioned descriptions are merely specific implementations of this application, but are not intended to limit the protection scope of this application. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in this application shall fall within the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.

Claims

1. A new compressed air energy storage system, comprising a constant-pressure diaphragm pressure tank, an air compression and energy release subsystem, and a working medium gas vapor-liquid conversion subsystem, whereinthe constant-pressure diaphragm pressure tank is divided into a first cavity and a second cavity by using an air film;the first cavity is in communication with the air compression and energy release subsystem, and the air compression and energy release subsystem is configured to: store compressed air into the first cavity in an energy storage phase, and discharge the compressed air in the first cavity in an energy release phase;the second cavity is in communication with the working medium gas vapor-liquid conversion subsystem, and the working medium gas vapor-liquid conversion subsystem comprises a working medium gas liquid storage tank, a heat exchanger V, a low-temperature heat storage tank, and a low-temperature cold storage tank; in the energy storage phase, working medium gas discharged from the second cavity is liquefied by absorbing cold energy of the low-temperature cold storage tank by using the heat exchanger V and flows into the working medium gas liquid storage tank; and in the energy release phase, working medium gas flowing out of the working medium gas liquid storage tank is vaporized by absorbing heat energy of the low-temperature heat storage tank by using the heat exchanger V and then discharged into the second cavity; andpressure in the first cavity is the same as that in the second cavity.

2. The new compressed air energy storage system according to claim 1, wherein the pressure in the first cavity of the constant-pressure diaphragm pressure tank is 3 Mpa to 15 Mpa.

3. The new compressed air energy storage system according to claim 2, wherein the pressure in the first cavity of the constant-pressure diaphragm pressure tank is 6 Mpa, the working medium gas is carbon dioxide, and the second cavity is inside the first cavity.

4. The new compressed air energy storage system according to claim 3, wherein the air compression and energy release subsystem comprises an air compression assembly, an air energy release assembly, and a heat exchange circulation mechanism mainly composed of a high-temperature heat storage tank and a high-temperature cold storage tank, and the heat exchange circulation mechanism is configured to provide heat energy released by the air compression assembly in the energy storage phase to the air energy release assembly in the energy release phase.

5. The new compressed air energy storage system according to claim 4, wherein the air compression assembly is formed by sequentially connecting a first-stage air compressor, a heat exchanger I, a second-stage air compressor, and a heat exchanger II.

6. The new compressed air energy storage system according to claim 4, wherein the air energy release assembly is formed by sequentially connecting a heat exchanger III, a first-stage air turbine, a heat exchanger IV, and a second-stage air turbine.

7. The new compressed air energy storage system according to any one of claims 1 to 6, wherein the working medium gas vapor-liquid conversion subsystem further comprises 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.

8. The new compressed air energy storage system according to claim 7, wherein the refrigeration compressor unit comprises a heat exchanger Ⅶ for internal circulation, 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 separately connected to the low-temperature heat storage tank and the low-temperature cold storage tank.

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