Compressed carbon dioxide energy storage system and method based on gravity driving

Abstract

The invention belongs to the field of energy storage, and discloses a compressed carbon dioxide energy storage system and method based on gravity driving, and the system comprises a carbon dioxide storage unit, a mechanical transmission device, an expansion machine and a power generator; the carbon dioxide storage unit comprises at least two carbon dioxide storage devices used for containing carbon dioxide, a plurality of gravity units are arranged above the carbon dioxide storage devices, and the mechanical transmission device is used for driving and adjusting the number of the gravity units arranged above the carbon dioxide storage devices. A gas outlet and a gas inlet are formed in the carbon dioxide storage device, the gas outlet is connected with the gas inlet end of the expansion machine, and the gas inlet is connected with the gas outlet end of the expansion machine; the power output end of the expansion machine is connected with the generator. Compression storage of gravitational potential energy on carbon dioxide gas is achieved, dependence of a traditional energy storage technology on stable electric energy is eliminated, and the method has important significance on long-term sustainable development of green independent power grids in remote areas.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage, and relates to a gravity-driven compressed carbon dioxide energy storage system and method. Background Art

[0002] Due to the special geographical environment in remote areas, such as long line extension distances and low load density caused by sparse population distribution, the power supply and maintenance costs of traditional power grids have become extremely high. These areas often face the challenges of unstable power supply, difficult infrastructure construction, and rising operation and maintenance costs. Traditional power grids not only need to lay long-distance transmission lines, but also need to regularly maintain and overhaul these lines, which not only increases the economic burden but also has a certain impact on the environment. Therefore, exploring new energy solutions is crucial for the sustainable development of remote areas. Renewable energy, such as wind power and solar energy, is regarded as a key way to solve energy problems in remote areas because of its clean and environmentally friendly characteristics and wide distribution of resources. These forms of energy can reduce dependence on fossil fuels and reduce greenhouse gas emissions, which is in line with the general trend of global energy transformation. However, the use of renewable energy is not without obstacles. Its energy density is relatively low, and it is affected by natural factors such as weather conditions and seasonal changes, showing strong volatility, which makes it difficult to directly use renewable energy for stable power supply. Especially in remote areas, this instability may be further exacerbated, affecting the quality of life of local residents and economic development.

[0003] Compressed gas energy storage technology, as an advanced energy storage method, provides a new idea for solving the volatility of renewable energy. This technology stores energy by compressing gas (such as carbon dioxide) and releases this energy to supply electricity when needed. As an energy storage medium, carbon dioxide has unique thermodynamic properties. Its critical temperature is only 31.4℃ and its critical pressure is 7.39MPa, which means that under normal temperature conditions, carbon dioxide can achieve high-density energy storage through physical phase change, showing great development potential.

[0004] However, conventional compressors face a key problem when compressing carbon dioxide: they are highly dependent on a stable power supply. In remote areas, due to the instability of power grid supply and the intermittent nature of renewable energy, obtaining stable power has become a major problem. This limits the promotion and application of conventional compressors in these areas, making it difficult to fully utilize the advantages of compressed gas energy storage technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a gravity-driven compressed carbon dioxide energy storage system and method.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a gravity-driven compressed carbon dioxide energy storage system, comprising a carbon dioxide storage unit, a mechanical transmission device, an expander and a generator; the carbon dioxide storage unit comprises at least two carbon dioxide gas storage devices for accommodating carbon dioxide, a plurality of gravity units are arranged above the carbon dioxide gas storage devices, the mechanical transmission device is used to adjust the number of gravity units arranged above each carbon dioxide gas storage device, the carbon dioxide gas storage device is provided with an air outlet and an air inlet, the air outlet of the carbon dioxide gas storage device is connected to the air inlet end of the expander, and the air inlet of the carbon dioxide gas storage device is connected to the air outlet end of the expander; the power output end of the expander is connected to the generator.

[0008] Optionally, the carbon dioxide storage device includes a concrete shaft and a flexible composite material liner arranged inside the concrete shaft.

[0009] Optionally, the concrete shaft is arranged underground.

[0010] Optionally, a heat exchange device is also included; the gas outlet of the carbon dioxide storage device is connected to the gas inlet end of the expander through the heat exchange device, which is used to heat the carbon dioxide gas flowing from the gas outlet to the gas inlet end of the expander.

[0011] Optionally, it also includes a renewable energy integration unit; the renewable energy integration unit is connected to both the mechanical transmission device and the heat exchange device.

[0012] Optionally, it also includes an automatic control system; the automatic control system includes batteries and measurement and control equipment, and the batteries and measurement and control equipment are connected to the renewable energy integration unit, mechanical transmission device, expander and heat exchanger, and are used to provide electrical energy and control the renewable energy integration unit, mechanical transmission device, expander and heat exchanger, respectively.

[0013] Optionally, the renewable energy integration unit includes one or more of the following: a wind drive unit, a water drive unit, a photothermal conversion unit and a photovoltaic power generation unit.

[0014] Optionally, at least two groups of carbon dioxide storage units are provided.

[0015] Optionally, the gas outlet and gas inlet of the carbon dioxide storage device are the same gas delivery port.

[0016] In a second aspect, the present invention provides a compressed carbon dioxide energy storage method based on the above-mentioned gravity-driven compressed carbon dioxide energy storage system, comprising: defining a carbon dioxide storage device with higher pressure in a carbon dioxide storage unit as a high-pressure carbon dioxide storage device, and a carbon dioxide storage device with lower pressure as a low-pressure carbon dioxide storage device; releasing the carbon dioxide in the high-pressure carbon dioxide storage device to the expander through the gas outlet and the gas inlet end of the expander, and driving the generator to generate electricity through the expander, and entering the low-pressure carbon dioxide storage device through the gas outlet end of the expander and the gas inlet of the low-pressure carbon dioxide storage device, and adjusting a plurality of gravity units above the high-pressure carbon dioxide storage device to above the low-pressure carbon dioxide storage device through a mechanical transmission device to complete the switching between the high-pressure carbon dioxide storage device and the low-pressure carbon dioxide storage device.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention is based on a gravity-driven compressed carbon dioxide energy storage system. The designed carbon dioxide storage unit includes at least two gas storage devices for accommodating carbon dioxide. The number of gravity units arranged above each carbon dioxide gas storage device is adjusted based on a mechanical transmission device to realize the switching of the carbon dioxide gas storage device between high pressure and low pressure states, thereby meeting the closed storage requirements and improving the utilization efficiency of the storage space of the gas storage device. By adjusting the gravity unit above the carbon dioxide gas storage device, the constant pressure accommodation of carbon dioxide in the carbon dioxide gas storage device under different pressure states is realized, and the efficiency of the supporting working equipment is improved. In addition, through the design of the gravity unit, the requirements for the quality of renewable energy are reduced, and the utilization efficiency of renewable energy such as wind energy and river energy is improved. At the same time, the compressed carbon dioxide energy storage technology has a high energy density, can replace pumped storage, is more suitable for areas with water scarcity, and reduces the dependence of traditional compressors on stable electricity, which can lay a solid technical foundation for the construction of an independent power grid with green and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of a gravity-driven compressed carbon dioxide energy storage system according to an embodiment of the present invention.

[0020] Among them: 1-renewable energy integration unit; 2-generator; 3-automatic control system; 4-heat exchange device; 5-carbon dioxide storage device; 6-gravity unit; 7-mechanical transmission device; 8-expander. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0024] See also Figure 1 In one embodiment of the present invention, a gravity-driven compressed carbon dioxide energy storage system is provided to optimize the energy storage method and improve the efficiency of the compressed carbon dioxide energy storage system. It can get rid of the dependence of traditional compressed carbon dioxide energy storage technology on stable electric energy, reduce the requirements for the quality of renewable energy, improve the utilization efficiency of renewable energy, and lay a solid technical foundation for the construction of a green independent power grid.

[0025] Specifically, the gravity-driven compressed carbon dioxide energy storage system of the present invention includes a carbon dioxide storage unit, a mechanical transmission device 7, an expander 8 and a generator 2. The carbon dioxide storage unit includes at least two carbon dioxide storage devices 5 for accommodating carbon dioxide. The mechanical transmission device 7 adjusts the number of gravity units 6 above each carbon dioxide storage device 5 to achieve different degrees of compression of the carbon dioxide contained in the carbon dioxide storage device 5. The carbon dioxide storage device 5 is provided with an outlet and an inlet, the outlet of the carbon dioxide storage device 5 is connected to the inlet end of the expander 8, and the inlet of the carbon dioxide storage device 5 is connected to the outlet end of the expander 8; the power output end of the expander 8 is connected to the generator 2.

[0026] The present invention is based on a gravity-driven compressed carbon dioxide energy storage system. The designed carbon dioxide storage unit includes two carbon dioxide gas storage devices 5 for accommodating carbon dioxide, and a plurality of gravity units 6 are arranged above each carbon dioxide gas storage device 5. The carbon dioxide contained in the carbon dioxide gas storage device 5 is compressed by the gravity of the gravity unit 6. The requirements for the quality of renewable energy are reduced through the design of the gravity unit 6, and the utilization efficiency of renewable energy such as wind energy and river energy is improved. In addition, the compressed carbon dioxide energy storage technology has a high energy density, can replace pumped storage, is more suitable for areas with scarce water resources, and reduces the dependence of traditional compressors on stable electricity, which can lay a solid technical foundation for the construction of an independent power grid with green and sustainable development. At the same time, a mechanical transmission device 7 is provided to adjust the number of gravity units 6 arranged above each carbon dioxide gas storage device 5, so as to realize different degrees of constant pressure accommodation of carbon dioxide in the carbon dioxide gas storage device 5, complete the switching of the carbon dioxide gas storage device 5 between high pressure and low pressure states, and improve the utilization efficiency of the storage space of the gas storage device.

[0027] Explanatory, the carbon dioxide storage unit includes at least two carbon dioxide storage devices 5 for accommodating carbon dioxide. The carbon dioxide storage devices 5 can be designed in pairs. By changing the number of weight units, for example, the gravity unit 6 set above one carbon dioxide storage device 5 can be moved above another carbon dioxide storage device 5, thereby realizing flexible interchange of high-pressure and low-pressure carbon dioxide storage devices 5, making full use of the storage space of the carbon dioxide storage device 5, and effectively reducing costs.

[0028] Explanatory note, in order to control the flow direction of carbon dioxide, corresponding valves may be provided on the carbon dioxide delivery pipeline to achieve corresponding control.

[0029] In a possible implementation, the carbon dioxide storage device 5 includes a concrete shaft and a flexible composite material liner arranged inside the concrete shaft.

[0030] Explanatory, a deformable flexible composite material is used as the inner lining, and a shell in the form of a concrete shaft is used as a carbon dioxide storage device. Among them, the flexible composite material lining ensures airtightness, and the concrete shaft is used as the main pressure-bearing structure to effectively avoid the limitations of special geological and geographical conditions, and significantly reduce the difficulty of building a compressed carbon dioxide energy storage system. At the same time, under the action of gravitational potential energy, combined with the free deformation of the flexible composite material lining, the constant pressure release of carbon dioxide can be guaranteed, thereby significantly improving the work efficiency of the expander 8.

[0031] In a possible embodiment, the concrete shaft is arranged underground.

[0032] Explanatory, underground concrete shafts can effectively utilize underground space resources and reduce the occupation of ground land, which is particularly important for areas with tight land resources and can also avoid the restrictions of special geological and geographical conditions. At the same time, the underground environment is relatively stable and the temperature changes little, which is conducive to maintaining the structural stability and air tightness of the carbon dioxide storage device 5 for a long time. In addition, as the main pressure-bearing structure, the underground concrete shaft is strong enough to withstand the potential impact of external geological activities, such as earthquakes and ground subsidence, thereby ensuring the safe operation of the carbon dioxide storage device 5. This design not only reduces the difficulty of construction, but also improves the overall reliability and durability of the system, providing a new solution for large-scale geological storage of carbon dioxide and energy storage.

[0033] In a possible embodiment, the gravity-driven compressed carbon dioxide energy storage system also includes a heat exchange device 4; the outlet of the carbon dioxide storage device 5 is connected to the air inlet end of the expander 8 through the heat exchange device 4, which is used to heat the carbon dioxide gas flowing from the outlet to the air inlet end of the expander 8, thereby improving the working capacity of the carbon dioxide working fluid.

[0034] Exemplarily, the heat exchange device 4 can be a heat exchange device 4 based on the photothermal effect. For example, the heat exchange device 4 includes a heat storage unit and a heat exchanger. Among them, the energy of the heat storage unit can be collected by a photothermal collector. Exemplarily, the photothermal collector adopts a high-efficiency light absorption material and a heat conduction structure, which can capture and convert solar radiation energy into thermal energy. The surface of the photothermal collector is coated with a high-absorption and low-reflectivity coating to ensure maximum absorption of sunlight. Heat pipes or fluid pipes are arranged inside the heat storage unit, and heat transfer media such as molten salt, heat transfer oil, etc. circulate in these pipes to absorb and transfer solar energy captured by the photothermal collector. The heat storage unit is used to store and release thermal energy during non-sunshine periods or when solar radiation is insufficient. High-density, high-heat capacity materials, such as molten salt heat storage tanks or phase change material heat storage systems, are usually used to ensure long-term storage and stable release of thermal energy. The heat exchanger is a key component connecting the heat storage unit and the air inlet end of the expander 8. When the carbon dioxide gas needs to be heated, the heat exchanger is started to transfer the heat energy in the heat storage unit to the carbon dioxide gas flowing through the heat exchanger. The heat exchanger is designed with efficient heat transfer structures such as finned tubes and spiral tubes to increase the heat transfer area and improve the heat transfer efficiency. By controlling the operating parameters of the heat exchanger, the heating process of the carbon dioxide gas can be precisely controlled.

[0035] In the compressed carbon dioxide energy storage system, the heat exchange device 4 can store solar thermal energy when there is sufficient sunlight, and release the heat energy when needed to heat the carbon dioxide gas at the inlet end of the expander 8. The heated carbon dioxide gas has a higher temperature and pressure, thereby improving the work capacity of the expander 8.

[0036] In a possible implementation, the gravity-driven compressed carbon dioxide energy storage system further includes a renewable energy integration unit 1 ; the renewable energy integration unit 1 is connected to both the mechanical transmission device 7 and the heat exchange device 4 .

[0037] Explanatory, the introduction of the renewable energy integration unit 1 into the gravity-driven compressed carbon dioxide energy storage system achieves a high degree of integration and optimization of energy utilization. This innovative design not only significantly improves the self-sufficiency of the system, but also enhances its application potential in the field of renewable energy. The renewable energy integration unit 1 provides driving force, and the mechanical transmission device 7 is used to compress the carbon dioxide gas in the carbon dioxide storage device 5 to a high pressure state. In addition, the heat generated during the compression process can also be supplied to the heat exchange device 4 for storage and utilization, and the photothermal effect or other high-efficiency heat exchange technology is used to preheat the carbon dioxide gas at the inlet end of the expander 8 to improve its working capacity. This integrated system design not only reduces the dependence on traditional fossil energy, but also gets rid of the restrictions on traditional stable electric energy, and realizes the cleanliness and efficiency of the entire process from production to storage and then to utilization of energy. In addition, the renewable energy integration unit 1 can also include an energy storage unit, which can effectively smooth the volatility of renewable energy power generation, improve the stability and reliability of the power system, and contribute to the construction of a green, low-carbon, safe and efficient energy system.

[0038] Exemplarily, the new energy power generation unit 1 includes one or more of the following: a wind drive unit and a water drive unit, a photothermal conversion unit and a photovoltaic power generation unit.

[0039] Explanatory, for remote mountainous areas lacking water resources, wind energy can be utilized through a wind drive unit, and the gravity unit 6 can be raised and lowered through a transmission device to convert wind energy into gravitational potential energy, thereby achieving compression and storage of carbon dioxide, and then converting it into electrical energy. For remote areas with river resources, river energy can be utilized through a hydraulic drive unit, and the gravity unit 6 can be raised and lowered through a transmission device to convert river energy into gravitational potential energy, thereby achieving compression and storage of carbon dioxide, and then converting it into electrical energy.

[0040] In a possible implementation, the gravity-driven compressed carbon dioxide energy storage system also includes an automatic control system 3; the automatic control system 3 includes a battery and a measurement and control device, and the battery and the measurement and control device are connected to the renewable energy integration unit 1, the mechanical transmission device 7, the expander 8 and the heat exchanger 4, and are respectively used to provide electrical energy and control the renewable energy integration unit 1, the mechanical transmission device 7, the expander 8 and the heat exchanger 4.

[0041] Explanatory, the gravity-driven compressed carbon dioxide energy storage system is further integrated into the automatic control system 3 to form a more complete and flexible energy management system. As the core of system regulation, the automatic control system 3 includes batteries and measurement and control equipment, which are closely connected with the renewable energy integration unit 1, the mechanical transmission device 7, the expander 8 and the heat exchanger 4 to jointly build a highly integrated, intelligent and coordinated energy storage and supply network. This design significantly enhances the energy storage and regulation capabilities of the system and improves energy utilization efficiency. At the same time, it can also flexibly adjust the charging and discharging strategy according to actual needs, further reduce the system operation cost, improve the overall economic benefits, and lay a solid foundation for the green transformation and sustainable development of the energy structure. In addition, the introduction of batteries in the automatic control system 3 also provides a solid guarantee for the stable operation of the system, and can provide emergency and necessary power supply even when renewable energy generation is interrupted due to extreme weather or emergencies.

[0042] In a possible implementation manner, at least two groups of carbon dioxide storage units are provided.

[0043] Explanatory, the setting of multiple groups of carbon dioxide storage units realizes the effective expansion of energy storage capacity, which can meet the needs of larger-scale and longer-term energy storage, and enhance the energy regulation and supply capacity of the system. Secondly, through group management, the system can more flexibly control the compression, storage and release process of carbon dioxide gas, optimize energy utilization efficiency, improve system response speed, and better adapt to changes in power load and the uncertainty of renewable energy generation. In addition, multiple groups of carbon dioxide storage units can also realize energy safety backup and redundant design to a certain extent. Even if a group of carbon dioxide storage units fails or is maintained, other groups can continue to work, ensuring the continuous and stable operation of the system, and enhancing the reliability and safety of the system. This innovative design not only improves the overall performance of the compressed carbon dioxide energy storage system, but also provides strong support for the large-scale access and efficient utilization of renewable energy, and accelerates the green transformation process of the energy structure.

[0044] In a possible implementation manner, the gas outlet and the gas inlet of the carbon dioxide storage device 5 are the same gas delivery port.

[0045] Explanatory note: the gas outlet and the gas inlet cleverly share the same gas transmission port. This design not only simplifies the structure of the carbon dioxide storage device 5, reduces the manufacturing cost and maintenance complexity, but also avoids the complex valve system and pipeline layout, reduces energy loss and leakage risks, and improves the overall energy efficiency of the system.

[0046] In another embodiment of the present invention, a compressed carbon dioxide energy storage method based on the gravity-driven compressed carbon dioxide energy storage system is provided, comprising the following steps:

[0047] The carbon dioxide storage device 5 with higher pressure in the carbon dioxide storage unit is defined as a high-pressure carbon dioxide storage device, and the carbon dioxide storage device 5 with lower pressure is defined as a low-pressure carbon dioxide storage device; the carbon dioxide in the high-pressure carbon dioxide storage device is released to the expander 8 through the gas outlet and the gas inlet end of the expander 8, and the generator 2 is driven by the expander 8 to generate electricity, and enters the low-pressure carbon dioxide storage device through the gas outlet end of the expander 8 and the gas inlet of the low-pressure carbon dioxide storage device, and the several gravity units 6 above the high-pressure carbon dioxide storage device are adjusted to above the low-pressure carbon dioxide storage device through the mechanical transmission device 7, so as to complete the switching between the high-pressure carbon dioxide storage device and the low-pressure carbon dioxide storage device.

[0048] Explanatory, the compressed carbon dioxide energy storage method of the present invention can be subdivided into an energy release process and an energy storage process.

[0049] Energy release process: The high-pressure carbon dioxide in the high-pressure carbon dioxide storage device enters the expander 8 after being heated by the heat exchange device 4, pushing the expander 8 to do work and driving the generator 2 to generate electricity, thereby converting the carbon dioxide compression energy into electrical energy. The carbon dioxide at the outlet of the expander 8 enters the low-pressure carbon dioxide storage device, realizing the closed operation of the compressed carbon dioxide energy storage system.

[0050] During operation, under the action of constant gravitational potential energy, as carbon dioxide is released in the high-pressure carbon dioxide gas storage device, the flexible composite material lining is deformed, and the height slowly decreases under the action of the gravitational potential energy of the gravity units 6, thereby maintaining a constant energy release pressure. Similarly, the back pressure at the outlet of the expander 8 is kept constant in the low-pressure carbon dioxide gas storage device, thereby significantly improving the operating efficiency of the expander 8.

[0051] Energy storage process: After the carbon dioxide gas in the high-pressure carbon dioxide storage device is completely released, the weight unit above the high-pressure carbon dioxide storage device is moved to the top of the low-pressure carbon dioxide storage device through the mechanical transmission device 7, so that the gravity mass above the low-pressure carbon dioxide storage device slowly increases, and the gravitational potential energy is used to compress the carbon dioxide gas in the low-pressure carbon dioxide storage device to complete energy storage.

[0052] The present invention is based on a gravity-driven compressed carbon dioxide energy storage method, which realizes energy conversion and storage by switching between high-pressure and low-pressure carbon dioxide gas storage devices. During the release of high-pressure carbon dioxide, it not only drives the expander 8 to generate electricity, realizing the immediate use of energy, but also optimizes the air intake mode of the expander 8 through constant-pressure energy release, significantly improving the energy conversion efficiency of the entire system. At the same time, the dynamic adjustment mechanism of the gravity unit 6 is used to flexibly transfer the gravitational potential energy, realize seamless switching between high-pressure and low-pressure gas storage devices, enhance the flexibility of the system, and effectively reduce the requirements for the quality of renewable energy, thereby improving the utilization efficiency of renewable energy. In addition, the method also has high environmental adaptability, can operate stably under different working conditions, and provides strong technical support for the large-scale application of renewable energy.

[0053] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A gravity-driven compressed carbon dioxide energy storage system, characterized in that: It comprises a carbon dioxide storage unit, a mechanical transmission device (7), an expander (8) and a generator (2); The carbon dioxide storage unit comprises at least two carbon dioxide storage devices (5) for accommodating carbon dioxide, a plurality of gravity units (6) are arranged above the carbon dioxide storage devices (5), a mechanical transmission device (7) is used to adjust the number of gravity units (6) arranged above each carbon dioxide storage device (5), the carbon dioxide storage device (5) is provided with an air outlet and an air inlet, the air outlet of the carbon dioxide storage device (5) is connected to the air inlet end of the expander (8), and the air inlet of the carbon dioxide storage device (5) is connected to the air outlet end of the expander (8); the power output end of the expander (8) is connected to the generator (2).

2. The gravity-driven compressed carbon dioxide energy storage system according to claim 1 is characterized in that: The carbon dioxide gas storage device (5) comprises a concrete shaft and a flexible composite material liner arranged inside the concrete shaft.

3. The gravity-driven compressed carbon dioxide energy storage system according to claim 2, characterized in that: The concrete shaft is arranged underground.

4. The gravity-driven compressed carbon dioxide energy storage system according to claim 1, characterized in that: It also includes a heat exchange device (4); the gas outlet of the carbon dioxide storage device (5) is connected to the gas inlet end of the expander (8) through the heat exchange device (4) to heat the carbon dioxide gas flowing from the gas outlet to the gas inlet end of the expander (8).

5. The gravity-driven compressed carbon dioxide energy storage system according to claim 4, characterized in that: It also comprises a renewable energy integration unit (1); the renewable energy integration unit (1) is connected to both the mechanical transmission device (7) and the heat exchange device (4).

6. The gravity-driven compressed carbon dioxide energy storage system according to claim 5, characterized in that: The invention also comprises an automatic control system (3); the automatic control system (3) comprises a storage battery and a measurement and control device, the storage battery and the measurement and control device are connected to the renewable energy integration unit (1), the mechanical transmission device (7), the expander (8) and the heat exchange device (4), and are respectively used to provide electric energy and control the renewable energy integration unit (1), the mechanical transmission device (7), the expander (8) and the heat exchange device (4).

7. The gravity-driven compressed carbon dioxide energy storage system according to claim 5, characterized in that: The renewable energy integration unit (1) comprises one or more of the following: a wind drive unit, a water drive unit, a photothermal conversion unit and a photovoltaic power generation unit.

8. The gravity-driven compressed carbon dioxide energy storage system according to claim 1, characterized in that: The carbon dioxide storage units are provided in at least two groups.

9. The gravity-driven compressed carbon dioxide energy storage system according to claim 1, characterized in that: The gas outlet and the gas inlet of the carbon dioxide gas storage device (5) are the same gas delivery port.

10. A compressed carbon dioxide energy storage method based on the gravity-driven compressed carbon dioxide energy storage system according to any one of claims 1 to 9, characterized in that: include: The carbon dioxide storage device (5) with a higher pressure in the carbon dioxide storage unit is defined as a high-pressure carbon dioxide storage device, and the carbon dioxide storage device (5) with a lower pressure is defined as a low-pressure carbon dioxide storage device; the carbon dioxide in the high-pressure carbon dioxide storage device is released to the expander (8) through the gas outlet and the gas inlet end of the expander (8), and the expander (8) drives the generator (2) to generate electricity, and enters the low-pressure carbon dioxide storage device through the gas outlet end of the expander (8) and the gas inlet of the low-pressure carbon dioxide storage device; and the plurality of gravity units (6) above the high-pressure carbon dioxide storage device are adjusted to above the low-pressure carbon dioxide storage device through the mechanical transmission device (7), thereby completing the switching between the high-pressure carbon dioxide storage device and the low-pressure carbon dioxide storage device.

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