Double-hole pumped compressed air energy storage system

Abstract

The present invention relates to an operation method of the double-cavity pumped hydro-compressed air energy storage system. The technical solution of the present invention is as follows: A double-cavity pumped hydro-compressed air energy storage system, characterized in that it comprises: a water-air coexistence cavern; a high-pressure air storage cavern, arranged above the water-air coexistence cavern and communicated with the water-air coexistence cavern through a plurality of connecting shafts; a pumped storage unit, communicated with the bottom of the water-air coexistence cavern through an upper water diversion tunnel and a pressure maintaining valve; and a ground reservoir, communicated with the pumped storage unit through a lower water diversion tunnel. The present invention is applicable to the field of new energy energy storage technology.

Description

Technical Field

[0001] The present invention relates to a double-hole pumped compressed air energy storage system, which is applicable to the field of new energy energy storage technology. Background Art

[0002] With the acceleration of the construction process of the new power system, a large amount of clean and renewable energy such as photovoltaic power generation and wind power generation is incorporated into the power grid for power generation. Due to the intermittent and fluctuating characteristics of the above new energy power generation itself, it is imperative to vigorously develop large-scale energy storage systems. Through large-scale energy storage systems, electrical energy can be converted into other forms for storage during the peak period of new energy power generation, and the stored energy can be used for power generation and fed into the power grid during the low power generation period, thereby improving the power grid's ability to absorb renewable new energy.

[0003] Currently, there are mainly two large-scale long-term energy storage methods: pumped storage and compressed air energy storage. Pumped storage technology is mature and has a high energy conversion efficiency of up to 75%; however, its disadvantage is that it has high site selection requirements, especially the need to select areas where a large-capacity upper reservoir basin can be formed, which is difficult. Compressed gas energy storage has lower site selection requirements and can be built in large quantities in various geological and topographical areas. Currently, the unit technology has gradually matured, but its main disadvantages are: (1) Traditional non-adiabatic compressed air energy storage requires fossil fuel combustion supplementation, has a large dependence on natural gas supply, and has a low energy storage efficiency, generally only about 50%; (2) Advanced adiabatic compressed air energy storage requires multi-stage compression and heat storage, adding multiple heat exchangers and other equipment in the system, making the system have a large floor area, high unit cost, and complex process.

[0004] Chinese Patent with Publication No. CN102797613A, a pumped compressed air energy storage system, discloses a system that stores energy through a high-pressure gas tank and a reservoir. During the low power consumption period, the water in the reservoir is pumped into the high-pressure tank by a water pump, and then during the high power consumption period, the gas in the high-pressure tank presses the water out, driving the water turbine and driving the generator to generate electricity. Its disadvantage is that the contact area between the high-pressure gas and the water surface is large, and a large amount of oxygen, carbon dioxide, etc. in the high-pressure air will partially dissolve in the water body, and the volume of the high-pressure gas tank is generally small, resulting in difficulty in maintaining a high-pressure state for a long time.

[0005] Chinese Patent with Publication No. CN108425784A, a pumped compressed air energy storage system and its operation method, discloses a system that stores energy through a high-pressure gas-water tank, an atmospheric pressure reservoir, a generator, a water pump, and a water turbine. Its disadvantage is also that the contact area between the high-pressure gas and the water surface is large, and no air replenishing device is provided, making it difficult to ensure the gas storage effect. Summary of the Invention

[0006] The technical problem to be solved by the present invention is: in view of the above problems, to provide a double-cavity pumped-storage compressed air energy storage system.

[0007] The technical solution adopted by the present invention is: a double-cavity pumped-storage compressed air energy storage system, characterized by comprising:

[0008] A water-air coexistence cavity;

[0009] A high-pressure gas storage cavity, arranged above the water-air coexistence cavity, and communicated with the water-air coexistence cavity through a plurality of connecting shafts;

[0010] A pumped-storage unit, communicated with the bottom of the water-air coexistence cavity through an upper water diversion tunnel and a pressure maintaining valve;

[0011] A surface reservoir, communicated with the pumped-storage unit through a lower water diversion tunnel.

[0012] A gas replenishing device capable of replenishing gas to the high-pressure gas storage cavity is connected to the high-pressure gas storage cavity.

[0013] The gas replenishing device includes a gas replenishing compressor, and the gas replenishing compressor is communicated with the top of the high-pressure gas storage cavity through a gas replenishing channel and a gas replenishing valve.

[0014] A pressure monitoring device for monitoring the pressure in the high-pressure gas storage cavity is arranged in the high-pressure gas storage cavity, and the pressure monitoring device is electrically connected with the pressure maintaining valve and the gas replenishing compressor, and is used for controlling the gas replenishing compressor to start when the pressure maintaining valve is closed and the pressure in the high-pressure gas storage cavity is monitored to drop by more than a preset value.

[0015] The water-air coexistence cavity and the high-pressure gas storage cavity are arranged in a mountain body.

[0016] The volume of the water-air coexistence cavity is more than 2 times the volume of the high-pressure gas storage cavity.

[0017] The height L of the connecting shaft, that is, the distance between the high-pressure gas storage cavity and the water-air coexistence cavity, is designed according to the following formula:

[0018] L≥5D

[0019] Wherein, D is the larger value of the diameter of the high-pressure gas storage cavity and the diameter of the water-air coexistence cavity.

[0020] The diameter d and the number N of the height of the connecting shaft are designed according to the following formula:

[0021]

[0022] Wherein, μ is the flow coefficient of the connecting shaft, Q is the maximum operating flow of the pumped-storage unit, and H min is the minimum operating head of the pumped-storage unit

[0023] An operating method for the double - hole pumped - hydro compressed - air energy storage system, characterized in that:

[0024] During the pumping process, the pumped - storage unit is in the pump state, and the external power grid supplies power to the pumped - storage unit. The water in the surface reservoir is pumped to the gas - water co - storage cavern through the cooperation of the pumped - storage unit, the lower diversion tunnel and the upper diversion tunnel. The gas in the gas - water co - storage cavern is compressed and stored in the high - pressure gas storage cavern through the connecting shaft until the gas - water interface rises to the middle height of the connecting shaft, then the pressure - maintaining valve of the upper diversion tunnel is closed and enters the high - pressure pressure - maintaining state;

[0025] During the power generation process, the pumped - storage unit is in the hydro - turbine power generation state. The pressure - maintaining valve is opened, and the high - pressure gas expands to do work, pushing the water in the gas - water co - storage cavern to be transported to the surface reservoir through the upper diversion tunnel, the pumped - storage unit and the lower diversion tunnel, driving the pumped - storage unit to generate electricity, and the electricity generated by the pumped - storage unit enters the external power grid; when the gas fills the gas - water co - storage cavern and the gas - water interface drops to the elevation of the top of the upper diversion tunnel, the pressure - maintaining valve is closed and enters the low - pressure pressure - maintaining state.

[0026] The energy storage capacity W of the pumped - hydro compressed - air energy storage system is calculated according to the following formula:

[0027]

[0028] Wherein, V1 is the volume of the high - pressure gas storage cavern; V2 is the volume of the gas - water co - storage cavern; P1 is the pressure in the low - pressure pressure - maintaining state.

[0029] The maximum operating head H of the pumped - storage unit is calculated according to the following formula:

[0030]

[0031] Wherein, V1 is the volume of the high - pressure gas storage cavern; V2 is the volume of the gas - water co - storage cavern; P1 is the pressure in the low - pressure pressure - maintaining state.

[0032] The maximum pump power of the pumped - storage unit is P Pump It is calculated according to the following formula:

[0033]

[0034] Wherein, T is the energy storage duration required by the power grid.

[0035] The beneficial effects of the present invention are as follows: The present invention is connected between a high-pressure gas storage cavern and a water-gas co-storage cavern through several connecting vertical shafts, and when maintaining high pressure, the water-gas interface is located within the connecting vertical shafts, thereby reducing the contact area between water and high-pressure air, decreasing the dissolution rate of high-pressure air, facilitating the pressure maintenance of the high-pressure cavern, and improving the energy storage efficiency.

[0036] The present invention eliminates the upper reservoir of the traditional pumped-storage power station and uses the potential energy of high-pressure gas to replace the gravitational potential energy of the water body in the upper reservoir, overcoming the topographical limitations in the selection of the upper reservoir site and having better promotion and applicability. Compared with the traditional compressed air energy storage system and the pumped compressed air energy storage system, the present invention uses the pumped-storage units commonly used in existing pumped-storage power stations, with more mature and reliable technology and higher energy storage efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic structural diagram of the high-pressure pressure-maintaining state in the embodiment.

[0038] Figure 2 It is a schematic structural diagram of the low-pressure pressure-maintaining state in the embodiment.

[0039] 1. High-pressure gas storage cavern; 2. Water-gas co-storage cavern; 3. Connecting vertical shaft; 4. Pumped-storage unit; 5. Upper water diversion tunnel; 6. Lower water diversion tunnel; 7. Surface reservoir; 8. Mountain body; 9. Pressure-maintaining valve; 10. Cable; 11. Transformer substation; 12. External power grid; 13. Air replenishing valve; 14. Air replenishing channel; 15. Air replenishing compressor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] This embodiment is a double-cavern pumped compressed air energy storage system, which has a water-gas co-storage cavern, a high-pressure gas storage cavern, a pumped-storage unit, a surface reservoir, and an air replenishing device.

[0041] In this example, the water-gas co-storage cavern is located within the mountain body, with a volume of approximately 1.5 million m 3 ; the high-pressure gas storage cavern is located within the mountain body, directly above the water-gas co-storage cavern, with a volume of approximately 0.5 million m 3 , and the water-gas co-storage cavern and the high-pressure gas storage cavern are interconnected through multiple connecting vertical shafts.

[0042] In this embodiment, the bottom of the water-gas co-storage cavern is connected to the pumped-storage unit through the upper water diversion tunnel, and a pressure-maintaining valve is provided at the connection between the upper water diversion tunnel and the water-gas co-storage cavern; the pumped-storage unit is connected to the surface reservoir through the lower water diversion tunnel, and the regulating storage capacity of the surface reservoir is 3 million m 3 .

[0043] In this example, the pumped-storage unit is connected to a transformer substation outside the mountain through a cable and is connected to the external power grid through the transformer substation.

[0044] In this embodiment, the air replenishing device includes an air replenishing compressor and an air replenishing valve. The air replenishing valve is arranged at the top of the high-pressure gas storage cavern. The air replenishing valve is connected to the air replenishing compressor outside the mountain through an air replenishing channel to meet the air replenishing and pressure maintaining requirements. The air replenishing channel can also be used as a maintenance access channel. Maintenance personnel can enter the high-pressure gas storage cavern after the high-pressure gas is emptied to check the condition of the cavern.

[0045] In this embodiment, a pressure monitoring device is provided for monitoring the pressure inside the high-pressure gas storage cavern. The pressure monitoring device has a pressure monitoring sensor arranged on the air replenishing valve and used for collecting the pressure data inside the high-pressure gas storage cavern. The pressure monitoring sensor is electrically connected to a controller, and the controller is electrically connected to a pressure maintaining valve.

[0046] In this embodiment, the height L of the connecting shaft is the distance between the high-pressure gas storage cavern and the water-gas co-storage cavern, and is designed according to the following formula:

[0047] L≥5D

[0048] Wherein, D is the larger of the diameter of the high-pressure gas storage cavern and the diameter of the water-gas co-storage cavern.

[0049] In this example, the diameter d and the number N of the connecting shaft are designed according to the following formula:

[0050]

[0051] Wherein, μ is the flow coefficient of the connecting shaft, Q is the maximum operating flow of the pumped-storage unit, and H min is the minimum operating head of the pumped-storage unit; generally, N is not less than 2, and d can be taken as:

[0052]

[0053] In this embodiment, by optimizing parameters such as the size and quantity of the connecting shaft, the contact surface between water and high-pressure air is reduced while ensuring the normal operation of the system.

[0054] The operation method of the double-cavern pumped-storage compressed air energy storage system in this embodiment is as follows:

[0055] During the pumping process, the pumped-storage unit is in the water pump state. The external power grid supplies power to the pumped-storage unit through a transformer substation. The energy storage unit pumps water through the lower water diversion tunnel and the upper water diversion tunnel to the water-gas co-storage cavern. The gas in the water-gas co-storage cavern is compressed and continuously stored in the high-pressure gas storage cavern through the connecting shaft until the water-gas interface rises to the middle height of the connecting shaft, and then the pressure maintaining valve of the upper water diversion tunnel is closed to enter the high-pressure pressure maintaining state.

[0056] During the power generation process, the pumped-storage unit is in the hydroelectric power generation state. The pressure-maintaining valve is opened, and the high-pressure gas expands and does work, pushing the water in the water-gas coexistence cavern to enter the surface reservoir successively through the upper water diversion tunnel, the pumped-storage unit, and the lower water diversion tunnel. During this process, the water drives the pumped-storage unit to generate electricity, and the electricity generated by the pumped-storage unit enters the external power grid through the transformer substation. When the gas fills the water-gas coexistence cavern and the water-gas interface drops to the elevation of the top of the upper water diversion tunnel, the pressure-maintaining valve is closed, and the low-pressure pressure-maintaining state is entered.

[0057] In this embodiment, the low-pressure pressure-maintaining state, the pumping condition, the high-pressure pressure-maintaining state, and the power generation condition are cycled in sequence, realizing the conversion of electric energy into other forms of energy storage during the peak period of new energy power generation; and then the stored energy is generated and fed into the power grid during the low power generation period, improving the power grid's consumption capacity for renewable new energy.

[0058] In this embodiment, when the controller collects through the pressure monitoring sensor that the pressure in the high-pressure gas storage cavern 1 drops by 5% and the pressure-maintaining valve is in the closed state at this time (the system is in the pressure-maintaining state), the air replenishing compressor is started to maintain the pressure in the cavern through air replenishment.

[0059] In this example, let the volume of the high-pressure gas storage cavern be V1, the volume of the water-gas coexistence cavern be V2, the volume of the connecting shaft can be ignored, and the pressure in the low-pressure pressure-maintaining state be P1. Then the energy storage capacity W of the double-cavern pumped-storage compressed air energy storage system is calculated according to the following formula:

[0060]

[0061] To improve the energy storage capacity of the pumped-storage compressed air energy storage system, the pressure P1 in the low-pressure pressure-maintaining state should be not less than 1 MPa, and the volume of the water-gas coexistence cavern should be more than twice that of the high-pressure gas storage cavern, that is:

[0062] V2≥2V1(2)

[0063] In this example, the pumped-storage unit adopts a variable-speed reversible water turbine unit to meet the operation requirements under different pressure states, and its maximum operating head should meet:

[0064]

[0065] In the formula, P1 is the pressure in the low-pressure pressure-maintaining state.

[0066] The maximum pump power of the pumped-storage unit in this embodiment is P Pump , and it should meet

[0067]

[0068] In the formula, T is the energy storage duration required by the power grid.

[0069] In this embodiment, the surface reservoir should satisfy that its regulating storage capacity V3 is greater than the volume V2 of the gas-water co-storage cavern, that is:

[0070] V3≥V2(5)

[0071] Under the low-pressure pressure-maintaining state, the internal pressure P1 of the high-pressure gas storage cavern 1 and the gas-water co-storage cavern 2 is 1.5 MPa. Substituting it into Equation (1) for calculation, the energy storage capacity of the system is W = 5200 GJ ≈ 1444 MW / h. The maximum operating head of the pumped-storage unit is 650 m, which can meet the pumped compressed air demand; the maximum pump power is about 300 MW, and then the calculated maximum energy storage duration is about 4.8 h, which meets the minimum 4 h energy storage duration requirement of the power grid.

[0072] The above is only used to illustrate the specific implementation cases of the present invention, and is not used to limit the scope of implementation of the present invention. All equivalent changes or modifications completed by those skilled in the art without departing from the spirit and principle indicated by the present invention should still be covered by the scope of the claims of the present invention.

Claims

1. A double-hole pumped compressed air energy storage system, characterized in that, Comprising: A water-vapor co-storage cavern; A high-pressure gas storage cavern, which is arranged above the water-vapor co-storage cavern and is connected to the water-vapor co-storage cavern through a number of connecting shafts. When maintaining high pressure, the water-vapor interface is located in the connecting shafts; A pumped-storage unit, which is connected to the bottom of the water-vapor co-storage cavern through an upper water diversion tunnel and a pressure-maintaining valve; A surface reservoir, which is connected to the pumped-storage unit through a lower water diversion tunnel; The high-pressure gas storage cavern is connected with a gas replenishing device capable of replenishing gas to the high-pressure gas storage cavern; The height L of the connecting shaft, which is the distance between the high-pressure gas storage cavern and the water-vapor co-storage cavern, is designed according to the following formula: ； Wherein, D is the larger of the diameters of the high-pressure gas storage cavern and the water-vapor co-storage cavern.

2. The double-hole pumped compressed air energy storage system according to claim 1, wherein: The gas replenishing device includes a gas replenishing compressor, and the gas replenishing compressor is connected to the top of the high-pressure gas storage cavern through a gas replenishing channel and a gas replenishing valve.

3. The dual-hole pumped compressed air energy storage system according to claim 2, wherein: A pressure monitoring device for monitoring the pressure in the high-pressure gas storage cavern is arranged in the high-pressure gas storage cavern. The pressure monitoring device is electrically connected to the pressure-maintaining valve and the gas replenishing compressor, and is used to control the start of the gas replenishing compressor when the pressure-maintaining valve is closed and the pressure drop in the high-pressure gas storage cavern exceeds a preset value.

4. The dual-hole pumped compressed air energy storage system according to claim 1, characterized in that: The water-vapor co-storage cavern and the high-pressure gas storage cavern are arranged in the mountain body.

5. The double-hole pumped compressed air energy storage system according to claim 1, wherein: The volume of the water-vapor co-storage cavern is more than twice the volume of the high-pressure gas storage cavern.

6. The double-hole pumped compressed air energy storage system according to claim 1, characterized in that: The diameter d and the number N of the connecting shafts are designed according to the following formula: ； Among them, is the flow coefficient of the connecting shaft, and Q is the maximum operating flow of the pumped-storage unit, is the minimum operating head of the pumped-storage unit.

7. An operation method of the double-cavern pumped-storage compressed air energy storage system according to any one of claims 1 to 6, characterized in that: During the pumping process, the pumped-storage unit is in the water pump state, and the external power grid supplies power to the pumped-storage unit. The water in the surface reservoir is pumped to the water-vapor co-storage cavern through the pumped-storage unit, the lower water diversion tunnel and the upper water diversion tunnel. The gas in the water-vapor co-storage cavern is compressed and stored in the high-pressure gas storage cavern through the connecting shafts until the water-vapor interface rises to the middle height of the connecting shafts, and then the pressure-maintaining valve of the upper water diversion tunnel is closed to enter the high-pressure pressure-maintaining state; During the power generation process, the pumped-storage unit is in the hydroelectric power generation state, the pressure-maintaining valve is opened, the high-pressure gas expands and does work, and the water in the water-vapor co-storage cavern is pushed through the upper water diversion tunnel, the pumped-storage unit and the lower water diversion tunnel to the surface reservoir, driving the pumped-storage unit to generate electricity, and the electricity generated by the pumped-storage unit enters the external power grid; when the gas fills the water-vapor co-storage cavern and the water-vapor interface drops to the elevation of the top of the upper water diversion tunnel, the pressure-maintaining valve is closed to enter the low-pressure pressure-maintaining state.

8. The operating method according to claim 7, characterized in that The energy storage capacity W of the pumped-storage compressed air energy storage system is calculated according to the following formula: ； Wherein, V1 is the volume of the high-pressure gas storage cavern; V2 is the volume of the water-vapor co-storage cavern; P1 is the pressure in the low-pressure pressure-maintaining state.

9. The operating method according to claim 7, characterized in that, The maximum operating head H of the pumped-storage unit is calculated according to the following formula: ； Wherein, V1 is the volume of the high-pressure gas storage cavern; V2 is the volume of the water-vapor co-storage cavern; P1 is the pressure in the low-pressure pressure-maintaining state.

10. The operating method according to claim 8, characterized in that, The maximum pump power of the pumped-storage unit is Calculated according to the following formula: ； Wherein, T is the energy storage duration required by the power grid.

Images