A combined mechanical gravity energy storage system for hydropower stations and its design method

Abstract

This application relates to a combined mechanical gravity energy storage system and design method for a hydropower station. The combined mechanical gravity energy storage system includes a pumped storage power station and a mechanical gravity energy storage system. The pumped storage power station includes an upper reservoir, a lower reservoir, and an underground powerhouse. The upper and lower reservoirs are located upstream and downstream of the dam body, respectively, and there is a predetermined height difference between them. The upper and lower reservoirs are connected to the underground powerhouse through water diversion tunnels, and the underground powerhouse is located inside the dam body. The mechanical gravity energy storage system includes a rotary hoist, a loading bin, a unloading bin, and gravity blocks. The rotary hoist is located on the top of the dam body, and the loading and unloading bins are located on the dam body, with a predetermined height difference between them. The rotary hoist can transport the gravity blocks back and forth between the loading and unloading bins.

Description

Technical Field

[0001] This application relates to the field of pumped storage power station technology, specifically to a combined mechanical gravity energy storage system and design method for a hydropower station. Background Technology

[0002] With the goal of "carbon peaking and carbon neutrality" being proposed, and in order to protect the ecological environment and address the increasing depletion of non-renewable resources such as oil, new energy sources such as wind power, photovoltaic power, solar power, and wave power are widely used. However, the power generation of these new energy sources is random and intermittent, which poses certain challenges to the power grid's power balance, stability, and peak regulation. To ensure the stable and safe operation of the power grid, energy storage systems such as pumped storage hydroelectric power stations and mechanical gravity energy storage are the most effective and convenient measures. Pumped storage hydroelectric power stations mainly consist of an upper reservoir and a lower reservoir, which have a significant elevation difference. Gravity energy storage, as a new energy storage technology in China, faces the challenge of utilizing a significant elevation difference in its construction. However, there are currently no engineering cases in China of hydroelectric power stations combined with mechanical gravity energy storage systems. Summary of the Invention

[0003] The first aspect of this application provides a hydropower station combined with a mechanical gravity energy storage system. This system combines a pumped storage power station with a mechanical gravity energy storage system, which can greatly reduce the construction cost of the mechanical gravity energy storage system and serve as a backup power source for the power station, thereby increasing the total peak power generation.

[0004] The first aspect of this application provides a hydropower station combined mechanical gravity energy storage system comprising a pumped storage power station and a mechanical gravity energy storage system. The pumped storage power station includes an upper reservoir, a lower reservoir, and an underground powerhouse. The upper reservoir and the lower reservoir are located upstream and downstream of the main body of the dam, respectively, and there is a preset height difference between them. The upper reservoir and the lower reservoir are connected to the underground powerhouse through water diversion tunnels, and the underground powerhouse is located inside the main body of the dam. The mechanical gravity energy storage system includes a rotary hoisting device, a loading bin, a unloading bin, and gravity blocks. The rotary hoisting device is located on the top of the main body of the dam. The loading bin and the unloading bin are located on the main body of the dam, and there is a preset height difference between them. The rotary hoisting device is capable of transporting the gravity blocks back and forth between the loading bin and the unloading bin.

[0005] In addition, the hydropower station combined mechanical gravity energy storage system provided in this application may also have the following additional technical features:

[0006] In one alternative, the pumped storage power station and the mechanical gravity energy storage system share an underground cable, which is electrically connected to the power transmission and distribution substation and power transmission lines located on the main body of the dam.

[0007] In one optional embodiment, the rotary lifting equipment includes a first lifting boom, a second lifting boom, a luffing trolley, a hook, a generator set, a rotating device, and a standard section. The standard section is fixedly mounted on the dam body via a foundation platform. The first and second lifting booms are mounted on the upper part of the standard section via the rotating device. The generator set is mounted on the standard section. The luffing trolley is slidably mounted on the tracks of the first and second lifting booms, and the luffing trolley is connected to the hook via pulley blocks and wire ropes.

[0008] In one alternative embodiment, the rotary lifting equipment further includes an intelligent cab, which is located on the upper part of the standard section. The intelligent cab is equipped with an intelligent driving system, which includes an automatic positioning module, an automatic lifting and lowering module, a remote control module, and a fault diagnosis module.

[0009] In one alternative embodiment, the loading hopper and the unloading hopper are storage-type hoppers, the storage-type hoppers are equipped with sliding rails, the top of the storage-type hoppers are equipped with openable and closable skylights, and the lower sidewalls of the storage-type hoppers are equipped with drainage holes; the gravity block is placed inside the storage-type hoppers.

[0010] In one alternative embodiment, the gravity block is a concrete block or a block made of corrosion-resistant and environmentally friendly materials, and a positioning chip is installed inside the gravity block.

[0011] In one alternative embodiment, the hydropower station combined with the mechanical gravity energy storage system has an energy storage phase and an energy release phase during operation. During the energy storage phase, the pumped storage power station uses excess electrical energy to pump water from the lower reservoir to the upper reservoir. The mechanical gravity energy storage system uses excess electrical energy to drive the rotary lifting equipment, which transports the gravity blocks in the unloading bin to the loading bin.

[0012] During the energy release phase, the hydroelectric power station converts the gravitational potential energy of water into electrical energy, and the mechanical gravity energy storage system converts the gravitational potential energy of the gravity block into electrical energy.

[0013] The second aspect of this application provides a design method for a hydropower station combined with a mechanical gravity energy storage system. This design method is used to design the hydropower station combined with a mechanical gravity energy storage system provided in the first aspect. The design method includes the following steps:

[0014] Based on the scale of the pumped storage power station and considering the mass energy storage density, the larger the mass energy storage density, the smaller the volume and mass of the mechanical gravity energy storage system required to store the same amount of electrical energy. Combined with the elevation of the dam body, the lifting height of the rotating hoisting equipment at the top of the dam body, the location of the loading and unloading yards, and the size and quantity of gravity blocks are determined.

[0015] An efficiency model is established to determine the configuration and parameter combination of the mechanical gravity energy storage system.

[0016] In one alternative approach, the efficiency model includes:

[0017] The mechanical gravity energy storage system converts electrical energy into gravitational potential energy for storage during the energy storage phase, and converts the gravitational potential energy back into electrical energy through the generator set of the rotating hoisting equipment during the energy release phase. The efficiency of the entire system is expressed as:

[0018] η = η EG ×η ES ;

[0019] For gravity-based energy storage, the mass energy storage density is expressed as: U m =mgx; Volumetric energy density is: Where m is the mass of a single gravity block, x is the displacement of the gravity block, and V is the volume of the gravity block. As can be seen from the above formula, the energy storage density of mechanical gravity energy storage is related to the displacement. Pumped storage power stations have a natural advantage in terms of high elevation. Energy storage density can be used to measure the mass and space occupied by mechanical gravity energy storage devices.

[0020] The main sources of loss in the mechanical gravity energy storage system during the lifting and transportation of the gravity block to the loading or unloading area are twofold: firstly, the drag coefficient caused by air resistance during the lifting / lowering of the gravity block; and secondly, friction loss caused by friction. The air resistance loss is expressed as follows:

[0021]

[0022] In the formula, A represents the windward area of ​​the gravity block, ρ is the air density, and C... w It is the air resistance coefficient, v(t) represents the upward / downward velocity, and t represents time;

[0023] Friction loss includes friction between the luffing trolley and the track during the translation of the gravity block, rotational friction of the rotating device, and friction between the conveyor tracks in the loading and unloading areas. The magnitude of the frictional force is positively correlated with the mass of the gravity block; therefore, the total friction loss is expressed as follows:

[0024] E f =E f1 +E f2 +Ef3 ;

[0025] E f3 =μ2mgx;

[0026] In the formula, γ, μ, and μ2 represent the correlation coefficients between friction force and the mass of the gravity block, which are relevant to actual engineering. v′(t) represents the moving speed of the variable amplitude trolley, ω(t) is the rotational angular velocity, r is the rotational radius, and x is the distance the object is transported by the conveyor track.

[0027] In one alternative approach, the calculation of energy storage efficiency and power generation efficiency is also included when establishing the efficiency model;

[0028] During the energy storage phase, the mechanical gravity energy storage system drives the gravity block to rise. The gravity block does work to overcome air resistance. The gravity block needs to overcome friction to reach its position at the loading yard. Considering motor losses and bidirectional substation losses, the energy storage efficiency is expressed as:

[0029]

[0030] In the formula, E q η represents the energy consumed by the gravitational block as it rises. G For the efficiency of the integrated electric generator, η inv This represents the efficiency of a bidirectional substation;

[0031] During the energy release phase, the mechanical gravity energy storage system uses the gravity block's own weight as a power source. During descent, it overcomes wind resistance and performs work. The luffing trolley overcomes friction to move the gravity block from the loading area to above the unloading area. During descent, gravitational potential energy is converted into kinetic energy. Most of this energy is converted into electrical energy by a generator set, and then supplied to users through a bidirectional substation and transmission lines. The power generation efficiency is:

[0032]

[0033] In the formula, E q ′ represents the energy released when the gravity block falls.

[0034] The beneficial effects of this application are as follows:

[0035] The mechanical gravity energy storage system combined with the pumped storage power station in this application utilizes the high elevation of the pumped storage power station's terrain, constructing the mechanical gravity energy storage system within the main dam structure, thereby reducing construction costs. During off-peak electricity demand, the mechanical gravity energy storage system can effectively store electrical energy alongside the pumped storage power station. Furthermore, the mechanical gravity energy storage system can transport personnel or large construction materials when needed, assisting in the construction and maintenance of the power station. It can also serve as a backup power source for the pumped storage hydropower station, offering a cleaner alternative than traditional diesel engines. This system helps increase the total peak power output of the pumped storage power station, enhancing its economic efficiency. The mechanical gravity energy storage system generates electricity during both the storage and release phases, compensating for energy losses during system operation.

[0036] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of a hydropower station combined with mechanical gravity energy storage in a specific embodiment of this application;

[0038] Figure 2 A schematic diagram of the structure of the rotary lifting device provided in this application in a specific embodiment;

[0039] Figure 3 This is a schematic diagram of the structure of a storage silo provided in this application in a specific embodiment.

[0040] Attached reference numerals: Upper reservoir 11, Lower reservoir 12, Underground powerhouse 13, Water diversion tunnel 14, Loading silo 15, Unloading silo 16, Gravity block 17, Main dam 2, Rotary lifting equipment 3, First lifting boom 31, Second lifting boom 32, Luffing trolley 33, Hook 34, Generator set 35, Rotating device 36, Standard section 37, Foundation platform 38, Intelligent cab 39, Underground cable 4, Power transmission substation 5, Power transmission line 6, Storage silo 7, Slide rail 71, Skylight 72, Drainage hole 73.

[0041] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. Detailed Implementation

[0042] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0043] It should be understood that the described embodiments are merely some embodiments of this application, and not all embodiments. All other technical solutions obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0044] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0045] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0046] It should be noted that the directional terms such as "upper," "lower," "left," and "right" described in the embodiments of this application are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this application. Furthermore, in the context, it should be understood that when it is mentioned that an element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0047] like Figure 1-3 As shown, the first aspect of this application provides a hydropower station combined with a mechanical gravity energy storage system. The hydropower station combined with a mechanical gravity energy storage system includes a pumped storage power station and a mechanical gravity energy storage system. The mechanical gravity energy storage system is installed in the upper reservoir of the pumped storage power station as a backup power source for the power station. It is cleaner than traditional diesel engines and also assists the power station in peak shaving and frequency regulation.

[0048] Specifically, the pumped storage power station includes an upper reservoir 11, a lower reservoir 12, and an underground powerhouse 13. The upper reservoir 11 and the lower reservoir 12 are located on the upstream and downstream sides of the dam body 2, respectively, and there is a preset height difference between the upper reservoir 11 and the lower reservoir 12. The upper reservoir 11 and the lower reservoir 12 are connected to the underground powerhouse 13 through a water diversion tunnel 14, and the underground powerhouse 13 is located inside the dam body 2. The mechanical gravity energy storage system includes a rotary hoisting device 3, a loading bin 15, a unloading bin 16, and gravity blocks 17. The rotary hoisting device 3 is set on the top of the dam body 2, and the loading bin 15 and the unloading bin 16 are set on the dam body 2, with a preset height difference between the loading bin 15 and the unloading bin 16. The rotary hoisting device 3 can transport the gravity blocks 17 back and forth between the loading bin 15 and the unloading bin 16.

[0049] The upper reservoir 11 of the pumped storage power station is developed using natural landforms, newly excavated and constructed, or already constructed. The lower reservoir 12 of the pumped storage power station is developed using natural landforms, newly excavated and constructed, or already constructed. The water in the upper reservoir is introduced into the underground powerhouse 13 through the water diversion tunnel 14, and the water turbine generator unit in the underground powerhouse 13 generates electricity.

[0050] In this embodiment, the hydropower station combined with a mechanical gravity energy storage system leverages the high elevation of pumped storage power stations by constructing the mechanical gravity energy storage system within the main dam body 2, thereby reducing construction costs. During off-peak electricity demand, the mechanical gravity energy storage system can effectively store electrical energy alongside the pumped storage power station. Furthermore, the mechanical gravity energy storage system can transport personnel or large construction materials when needed, assisting in power station construction and maintenance. It can also serve as a backup power source for the pumped storage hydropower station, offering a cleaner alternative to traditional diesel engines. This system helps increase the total peak power output of the pumped storage power station, enhancing its economic efficiency. The mechanical gravity energy storage system generates electricity during both the storage and release phases, compensating for energy losses during system operation.

[0051] like Figure 1 As shown, in one specific embodiment, the pumped storage power station and the mechanical gravity energy storage system share an underground cable 4, which is electrically connected to the power transmission and distribution substation 5 and the power transmission line 6 located on the main body of the dam 2.

[0052] like Figure 1-2As shown, in one specific embodiment, the rotary lifting device 3 includes a first lifting boom 31, a second lifting boom 32, a luffing trolley 33, a hook 34, a generator set 35, a rotating device 36, and a standard section 37. The standard section 37 is fixedly mounted on the dam body 2 via a foundation platform 38. The first lifting boom 31 and the second lifting boom 32 are mounted on the upper part of the standard section 37 via the rotating device 36. The generator set 35 is mounted on the standard section 37. The luffing trolley 33 is slidably mounted on the tracks of the first lifting boom 31 and the second lifting boom 32, and is connected to the hook 34 via pulley blocks and wire ropes. The luffing trolley 33 enables the translation of heavy objects. The intelligent cab 39 automatically adjusts the position of the luffing trolley 33 according to the force applied, ensuring the balance of the device.

[0053] In addition, the rotary lifting equipment 3 also includes an intelligent cab 39, which is located on top of the standard section 37. The intelligent cab 39 houses an intelligent driving system that can monitor the operational safety data of the rotary lifting equipment 3 and diagnose faults based on the monitored data, including PLC data on the lifting arm's force, vibration, and noise, or other sensor data. It can achieve remote control, automatic positioning of the gravity block 17, and automatic raising and lowering of the gravity block 17 according to real-time requirements. The intelligent driving system includes an automatic positioning module, an automatic raising and lowering module, a remote control module, and a fault diagnosis module.

[0054] In this embodiment, the rotating lifting device 3 can be a tower crane with a double boom. It should be noted that although a tower crane with a double boom is used as the main lifting device for the mechanical gravity energy storage system, other lifting devices such as traditional tower cranes or tower cranes with multiple boom designs are not excluded as the main equipment. This article does not make specific limitations on this.

[0055] like Figure 3 As shown, in one specific embodiment, the upper hopper 15 and the lower hopper 16 are storage hoppers 7. The storage hopper 7 is equipped with a sliding rail 71, and its top has an openable and closable skylight 72. The lower sidewall of the storage hopper 7 has drainage holes 73. Gravity blocks 17 are vertically arrayed within the storage hopper 7. The drainage holes 73 effectively prevent water accumulation in the storage hopper 7 during the rainy season. The upper hopper 15 and the lower hopper 16 can also serve as temporary warehouses for storing construction materials or essential living supplies. Furthermore, the gravity blocks 17 are made of concrete blocks or environmentally friendly materials with good corrosion resistance in humid environments and are recyclable. Positioning chips are pre-embedded within the gravity blocks 17, facilitating the intelligent cab 39 to locate their positions for picking, transporting, and placing. If special needs arise, the gravity blocks 17 can be replaced with personnel or construction materials to assist in power plant construction and maintenance.

[0056] The hydropower station combined with the mechanical gravity energy storage system has an energy storage phase and an energy release phase during operation. During the energy storage phase, the pumped storage power station uses excess electrical energy to pump water from the lower reservoir 12 to the upper reservoir 11, and the mechanical gravity energy storage system uses excess electrical energy to drive the rotary hoisting equipment 3, which transports the gravity blocks 17 in the lower hopper 16 to the upper hopper 15. During the energy release phase, the hydropower station converts the gravitational potential energy of the water into electrical energy, and the mechanical gravity energy storage system converts the gravitational potential energy of the gravity blocks 17 into electrical energy.

[0057] Specifically, the energy storage process: At night, when electricity demand is at its lowest, the pumped storage power station uses the excess electricity to pump water from the lower reservoir 12 to the upper reservoir 11. At this time, the electricity is converted into the gravitational potential energy of the water and stored. The mechanical gravity energy storage system also utilizes excess electrical energy for driving. The slide rail 71 of the unloading hopper 16 moves the gravity block 17 to the position of the skylight 72. The autopilot automatically positions the gravity block 17, and the second lifting arm 32 lowers the hook 34 to lift the gravity block 17. Simultaneously, the luffing trolley 33 moves the gravity block 17 to balance the device. The rotating device 36 rotates the second lifting arm 32 to the loading hopper 15 while the first lifting arm 31 rotates to the unloading hopper 16, lifting the gravity block 17 and balancing the device by moving its position using the luffing trolley 33. At this time, the luffing trolley 33 of the second lifting arm 32 moves the gravity block 17 above the loading hopper 15, and lowers it into the hopper using its own weight, thus converting excess electrical energy into gravitational potential energy for storage. The gravity blocks 17 are placed in a vertical array within the loading and unloading hoppers 16. When a certain height is reached, the slide rail 71 transports the gravity blocks 17 into the hopper for storage. During the descent of gravity block 17, it drives generator set 35 to convert a small portion of gravitational potential energy into electrical energy, making up for some of the power loss.

[0058] Energy release process: When electricity demand reaches its peak, the pumped storage power station opens the gates of the upper reservoir 11 to release water, converting the gravitational potential energy of the water into electrical energy. The slide rail 71 of the loading hopper 15 of the mechanical gravity energy storage system moves the gravity block 17 to the position of the skylight 72. The autopilot automatically positions the gravity block 17 and controls the first lifting arm 31 to lift it. Simultaneously, the luffing trolley 33 performs the operation of the balancing device of the gravity block 17. The rotating device 36 rotates the gravity block 17 lifted by the first lifting arm 31 to the top of the skylight 72 of the unloading hopper 16 and places it, realizing the conversion of gravitational potential energy into electrical energy. The operation mode of the energy release process is the opposite of that of the energy storage process. The electrical energy generated by both processes is transmitted to the substation and transmission line 6 through the underground cable 4 to supply users. At this time, the mechanical gravity energy storage device also plays a role in peak shaving and frequency regulation.

[0059] The second aspect of this application provides a design method for a hydropower station combined with a mechanical gravity energy storage system. This design method is used to design the hydropower station combined with a mechanical gravity energy storage system as described in the first aspect embodiment. The design method includes the following steps:

[0060] Based on the scale of the pumped storage power station, and considering the mass energy storage density, which is the amount of energy stored per unit volume or weight, the greater the mass energy storage density, the smaller the volume and mass of the mechanical gravity energy storage system required to store the same amount of electrical energy. In conjunction with the elevation of the dam main body, the lifting height of the rotating hoisting equipment at the top of the dam main body, the location of the loading and unloading yards, and the size and quantity of gravity blocks are determined.

[0061] Establish an efficiency model to determine the optimal configuration and parameter combination for the mechanical gravity energy storage system:

[0062] The mechanical gravity energy storage system converts electrical energy into gravitational potential energy for storage during the energy storage phase, and converts the gravitational potential energy back into electrical energy through the generator set of the rotating hoisting equipment during the energy release phase. The efficiency of the entire system is expressed as:

[0063] η = η EG ×η ES ;

[0064] For gravity-based energy storage, the mass energy storage density is expressed as: U m =mgx; Volumetric energy density is: Where m is the mass of a single gravity block, x is the displacement of the gravity block, and V is the volume of the gravity block. As can be seen from the above formula, the energy storage density of mechanical gravity energy storage is related to the displacement. Pumped storage power stations have a natural advantage in terms of high elevation. Energy storage density can be used to measure the mass and space occupied by mechanical gravity energy storage devices. Reasonable consideration can save costs and facilitate installation.

[0065] In addition, the main sources of loss in mechanical gravity energy storage systems during the lifting and transportation of gravity blocks to the loading or unloading area are twofold: firstly, the drag coefficient caused by air resistance during the lifting / lowering of the gravity blocks; and secondly, friction loss caused by friction. The air resistance loss is expressed as follows:

[0066]

[0067] In the formula, A represents the windward area of ​​the gravity block, ρ is the air density, and C... w It is the air resistance coefficient, v(t) represents the upward / downward velocity, and t represents time;

[0068] Friction loss includes friction between the luffing trolley and the track during the translation of the gravity block, rotational friction of the rotating device, and friction between the conveyor tracks in the loading and unloading areas. The magnitude of the frictional force is positively correlated with the mass of the gravity block; therefore, the total friction loss is expressed as follows:

[0069] E f =E f1 +E f2 +E f3 ;

[0070] E f3 =μ2mgx;

[0071] In the formula, γ, μ, and μ2 represent the correlation coefficients between friction force and the mass of the gravity block, which are relevant to actual engineering. v′(t) represents the moving speed of the variable amplitude trolley, ω(t) is the rotational angular velocity, r is the rotational radius, and x is the distance the object is transported by the conveyor track.

[0072] During the energy storage phase, the mechanical gravity energy storage system drives the gravity block to rise. The gravity block does work to overcome air resistance. To reach the corresponding position in the loading area, the gravity block needs to overcome friction. Considering motor losses and bidirectional substation losses, the energy storage efficiency is expressed as:

[0073]

[0074] In the formula, E q η represents the energy consumed by the gravitational block as it rises. G For the efficiency of the integrated electric generator, η inv This represents the efficiency of a bidirectional substation;

[0075] During the energy release phase, the mechanical gravity energy storage system relies on the gravity of the gravity block itself as its power source. During descent, it overcomes wind resistance, and the luffing trolley overcomes friction to move the gravity block from the loading area to above the unloading area. During descent, gravitational potential energy is converted into kinetic energy. Most of this energy is converted into electrical energy by generator sets, and then supplied to users through a bidirectional substation and transmission lines. The power generation efficiency is:

[0076]

[0077] In the formula, E q ′ represents the energy released when the gravity block falls.

[0078] In the various embodiments of this application, pumped storage power stations are constructed in combination with mechanical gravity energy storage systems. The mechanical gravity energy storage system can utilize the unique geographical conditions of the hydropower station to reduce construction costs; store excess electrical energy; assist the hydropower station in peak shaving, frequency regulation, and backup; and improve the overall peak power generation efficiency of the power station. During construction after design completion, the rotating lifting equipment of the mechanical gravity energy storage system utilizes the existing 100-meter elevation scale of the pumped storage power station's dam, reducing its construction height and keeping construction costs under control. Furthermore, the foundation platform can be considered in the early stages of pumped storage power station design and construction, with pre-embedded components to distribute construction costs and reduce the difficulty of later secondary development, resulting in good economic efficiency.

[0079] Pumped-storage power stations use water as the energy storage medium. During periods of low electricity demand, water is pumped from the lower reservoir to the upper reservoir, converting electrical energy into the gravitational potential energy of the water for storage. This provides excellent peak-shaving, frequency regulation, energy storage, and backup functions, and the upper and lower reservoirs have a significant height difference. Mechanical gravity energy storage devices, on the other hand, use concrete blocks or environmentally friendly materials that are not easily corroded in humid environments as the energy storage medium. Pumped-storage power stations provide highly favorable natural height conditions for mechanical gravity energy storage devices, effectively reducing the construction height of the device itself. Furthermore, the mechanical gravity energy storage system can be pre-embedded during the early stages of dam construction, creating a solid foundation and spreading construction costs, resulting in good economic efficiency. Excess electricity from pumped-storage power stations is supplied to mechanical gravity energy storage devices for storage. Mechanical gravity energy storage devices can also assist in peak-shaving and frequency regulation of the power station, increasing the total peak power generation. As a backup power source for hydropower stations, it is cleaner than using traditional diesel generators as backup power.

[0080] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A hydropower station combined with mechanical gravity energy storage system, characterized in that, The system includes a pumped-storage power station and a mechanical gravity energy storage system. The pumped-storage power station includes an upper reservoir, a lower reservoir, and an underground powerhouse. The upper reservoir and the lower reservoir are located on the upstream and downstream sides of the dam body, respectively, and there is a preset height difference between the upper reservoir and the lower reservoir. The upper reservoir and the lower reservoir are connected to the underground powerhouse through water diversion tunnels. The underground powerhouse is located inside the dam body. The mechanical gravity energy storage system includes a rotary lifting device, a loading bin, a unloading bin, and gravity blocks. The rotary lifting device is located on the top of the dam body, and the loading bin and the unloading bin are located on the dam body, with a preset height difference between them. The rotary lifting device can transport the gravity blocks back and forth between the loading bin and the unloading bin. The configuration and parameter combination of the mechanical gravity energy storage system are determined through the following design method: Based on the scale of the pumped storage power station and considering the mass energy storage density, the larger the mass energy storage density, the smaller the volume and mass of the mechanical gravity energy storage system required to store the same amount of electrical energy. Combined with the elevation of the dam body, the lifting height of the rotating hoisting equipment at the top of the dam body, the location of the loading and unloading yards, and the size and quantity of gravity blocks are determined. An efficiency model is established to determine the configuration and parameter combination of the mechanical gravity energy storage system.

2. The hydropower station combined with mechanical gravity energy storage system according to claim 1, characterized in that, When establishing an efficiency model, the following should be included: The mechanical gravity energy storage system converts electrical energy into gravitational potential energy for storage during the energy storage phase, and converts the gravitational potential energy back into electrical energy through the generator set of the rotating hoisting equipment during the energy release phase. The efficiency of the entire system is expressed as: ； For gravity-based energy storage, the mass energy storage density is expressed as: The volumetric energy storage density is: ; Where m is the mass of a single gravity block, x is the displacement of the gravity block, and V is the volume of the gravity block. As can be seen from the above formula, the energy storage density of mechanical gravity energy storage is related to the displacement. Pumped storage power stations have a natural advantage in terms of high elevation. Energy storage density can be used to measure the mass and space occupied by mechanical gravity energy storage devices. The main sources of loss in the mechanical gravity energy storage system during the lifting and transportation of the gravity block to the loading or unloading area are twofold: firstly, the drag coefficient caused by air resistance during the lifting / lowering of the gravity block; and secondly, friction loss caused by friction. The air resistance loss is expressed as follows: ； In the formula, A represents the windward area of ​​the gravity block, ρ is the air density, and C... w It is the air resistance coefficient, v(t) represents the upward / downward velocity, and t represents time; Friction loss includes friction between the luffing trolley and the track during the translation of the gravity block, rotational friction of the rotating device, and friction between the conveyor tracks in the loading and unloading areas. The magnitude of the frictional force is positively correlated with the mass of the gravity block; therefore, the total friction loss is expressed as follows: ； ； ； ； In the formula, γ, μ, and μ2 represent the correlation coefficients between frictional force and the mass of the gravity block, which are relevant to actual engineering. This indicates the speed of the variable amplitude trolley. ω is the rotational angular velocity, r is the rotational radius, and x is the distance the object is transported by the transport track.

3. The hydropower station combined with mechanical gravity energy storage system according to claim 2, characterized in that, The calculation of energy storage efficiency and power generation efficiency is also included when establishing the efficiency model; During the energy storage phase, the mechanical gravity energy storage system drives the gravity block to rise. The gravity block does work to overcome air resistance. The gravity block needs to overcome friction to reach its position at the loading yard. Considering motor losses and bidirectional substation losses, the energy storage efficiency is expressed as: ； In the formula, This represents the energy consumed by the gravity block as it rises. For the efficiency of the integrated electric generator, This represents the efficiency of a bidirectional substation; During the energy release phase, the mechanical gravity energy storage system uses the gravity block's own weight as a power source. During descent, it overcomes wind resistance and performs work. The luffing trolley overcomes friction to move the gravity block from the loading area to above the unloading area. During descent, gravitational potential energy is converted into kinetic energy. Most of this energy is converted into electrical energy by a generator set, and then supplied to users through a bidirectional substation and transmission lines. The power generation efficiency is: ； In the formula, This represents the energy released when the gravity block falls.

4. The hydropower station combined with mechanical gravity energy storage system according to claim 3, characterized in that, The pumped storage power station and the mechanical gravity energy storage system share underground cables, which are electrically connected to the power transmission and distribution substation and power transmission lines located on the main body of the dam.

5. The hydropower station combined with mechanical gravity energy storage system according to claim 1 or 4, characterized in that, The rotating lifting equipment includes a first lifting boom, a second lifting boom, a luffing trolley, a hook, a generator set, a rotating device, and a standard section. The standard section is fixedly mounted on the main body of the dam via a foundation platform. The first and second lifting booms are mounted on the upper part of the standard section via the rotating device. The generator set is mounted on the standard section. The luffing trolley is slidably mounted on the tracks of the first and second lifting booms, and the luffing trolley is connected to the hook via a pulley system and wire rope.

6. The hydropower station combined with mechanical gravity energy storage system according to claim 5, characterized in that, The rotary lifting equipment also includes an intelligent cab, which is located on the upper part of the standard section. The intelligent cab is equipped with an intelligent driving system, which includes an automatic positioning module, an automatic lifting and lowering module, a remote control module, and a fault diagnosis module.

7. The hydropower station combined with mechanical gravity energy storage system according to claim 5, characterized in that, The loading hopper and the unloading hopper are storage-type hoppers. The storage-type hopper is equipped with a sliding rail. The top of the storage-type hopper is equipped with a skylight that can be opened and closed. The lower side wall of the storage-type hopper is equipped with drainage holes. The gravity block is placed inside the storage-type hopper.

8. The hydropower station combined with mechanical gravity energy storage system according to claim 7, characterized in that, The gravity block is a concrete block or a block made of corrosion-resistant and environmentally friendly materials, and a positioning chip is installed inside the gravity block.

9. The hydropower station combined with mechanical gravity energy storage system according to any one of claims 1-4 or 6-8, characterized in that, The hydropower station combined with the mechanical gravity energy storage system has an energy storage phase and an energy release phase during operation. In the energy storage phase, the pumped storage power station uses excess electrical energy to pump water from the lower reservoir to the upper reservoir, and the mechanical gravity energy storage system uses excess electrical energy to drive the rotary hoist, which transports the gravity blocks in the lower hopper to the upper hopper. In the energy release phase, the hydropower station converts the gravitational potential energy of the water into electrical energy, and the mechanical gravity energy storage system converts the gravitational potential energy of the gravity blocks into electrical energy.

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