An underwater high-density stable hydraulic energy storage and release system and control method thereof

Abstract

The present invention discloses an underwater high-density stable hydraulic energy storage and release system and a control method thereof, the system comprises a supporting system, a high-pressure liquid storage tank, a liquid level monitoring system and a bidirectional load energy conversion system; the supporting system is connected to the high-pressure liquid storage tank, and the liquid level monitoring system is arranged in the high-pressure liquid storage tank; the high-pressure liquid storage tank is connected to an atmospheric balance pipe and a filling and drainage pipe, the other end of the atmospheric balance pipe extends outside the horizontal plane, and the other end of the filling and drainage pipe is arranged below the horizontal plane; the bidirectional load energy conversion system comprises a bidirectional load generator and a water pump turbine, and a second electric valve and an anti-wave damping valve are arranged in the filling and drainage pipe; when storing energy, the water pump turbine discharges the water in the high-pressure liquid storage tank, and when releasing energy, the water enters the high-pressure liquid storage tank through the second electric valve and the anti-wave damping valve, pushes the water pump turbine, and drives the bidirectional load generator to generate electricity. The present invention realizes stable and high-energy-density energy storage and release by controlling the drainage and filling of the high-pressure liquid storage tank.

Description

Technical Field

[0001] The present invention relates to the field of offshore energy storage and release technology, and in particular to an underwater high-density stable hydraulic energy storage and release system and a control method thereof. Background Art

[0002] At present, offshore wind and solar power generation is vigorously developed. Wind and solar power storage can improve their intermittency, volatility and randomness, and reduce the wind and solar power abandonment rates of the power grid. Offshore wind and solar integrated charging stations usually use chemical batteries, are installed on the coast, and are equipped with more complex cooling, battery management and energy management systems. However, there are still safety issues such as overcharging leading to heat and combustion, and the cost of the entire life cycle may be high.

[0003] On-site commercial energy storage power stations at sea can use physical batteries based on hydraulic power. Existing offshore pumped-storage power stations choose islands to build upper reservoirs to form a natural head difference between the sea surface, but the construction conditions are harsh.

[0004] At present, there are still some defects and shortcomings in the energy storage technology composed of offshore hydraulic action:

[0005] For example, the patent publication number CN108757288A is a water-air co-containment tank power energy storage system and method using a deep-sea constant pressure gas storage tank at a constant pressure. It relies on the high-pressure air in the water-air co-containment tank to push the water to work on the turbine. It does not use the gravitational potential energy of seawater under natural conditions, and the heat of the compressed air process is discharged into the seawater, which has certain thermal pollution.

[0006] For example, the patent publication number CN111120208A is a hydraulic constant pressure energy storage and release system and intelligent control method, which mainly uses compressed air to store energy without considering compression heat discharge;

[0007] For example, the patent publication number CN116378885A is a large-scale underwater gas-liquid hybrid energy storage system and method without a gas transmission pipeline. It absorbs ocean renewable energy electricity and mainly stores it in the gas-liquid hybrid energy storage device as gas pressure potential energy. When releasing energy, the gas pressure potential energy is converted into seawater kinetic energy, and the seawater's own gravity potential energy is not used. In addition, there is compression heat emission of the gas.

[0008] For example, patent publication number CN110778442A discloses a method and system for storing energy by filling and discharging seawater in a vertical pipe to improve the energy efficiency of peak-shaving power supplies. This method only charges and discharges energy in vertical pipes, and has low energy storage density and stability.

[0009] Since offshore wind power and photovoltaic power have the characteristics of randomness and instability, and offshore wind power also has the characteristics of anti-peak regulation, a stable and high-density energy storage system needs to be configured. There is an urgent need for a high-density stable hydraulic energy storage and release technology in a seawater environment. Summary of the invention

[0010] In order to overcome the defects and shortcomings of the prior art, the present invention provides an underwater high-density stable hydraulic energy storage and release system and a control method thereof. The present invention utilizes the gravitational potential energy of seawater at a set depth, adopts an anti-wave damping valve to suppress the influence of sea surface wave height on the liquid pressure in the underwater high-pressure liquid storage tank, and utilizes an electric valve to adjust the filling and drainage flow of the high-pressure liquid storage tank to achieve the power generation and energy release of the impeller and the energy storage of the water pump. Due to the high density of seawater, a stable and high-energy-density energy storage and release system can be realized, thereby cooperating with the utilization of offshore renewable energy, and can further enhance the renewable energy absorption capacity, thereby reducing the wind and solar power abandonment rates, and providing effective technical means for promoting the flexible and efficient absorption of new energy.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] The present invention provides an underwater high-density stable hydraulic energy storage and release system, comprising: a load-bearing system, a high-pressure liquid storage tank, a liquid level monitoring system and a bidirectional load energy conversion system;

[0013] The object-carrying system is connected to a high-pressure liquid storage tank, and the liquid level monitoring system is arranged in the high-pressure liquid storage tank to monitor the liquid level depth of the high-pressure liquid storage tank;

[0014] An atmospheric balance pipe is provided on the upper end surface of the high-pressure liquid storage tank, one end of the atmospheric balance pipe is connected to the high-pressure liquid storage tank, and the other end of the atmospheric balance pipe extends to a position above the horizontal plane as an air inlet and outlet. A first electric valve is provided in the atmospheric balance pipe for switching the air intake and exhaust state;

[0015] A filling and drainage pipe is provided on one side of the high-pressure liquid storage tank, one end of the filling and drainage pipe is connected to the high-pressure liquid storage tank, and the other end of the filling and drainage pipe extends to a position below the horizontal plane to serve as a liquid inlet and outlet;

[0016] The bidirectional load energy conversion system includes a bidirectional load generator and a water pump turbine. A second electric valve and an anti-wave damping valve are provided in the filling and discharge pipes. The second electric valve is used to switch the liquid inlet and outlet states. The anti-wave damping valve is used to dynamically adjust the valve opening according to the liquid surface wave height.

[0017] When storing energy, the water pump turbine cooperates with the first electric valve, the second electric valve and the anti-wave damping valve to discharge the water from the high-pressure liquid storage tank. When releasing energy, water enters the high-pressure liquid storage tank through the second electric valve and the anti-wave damping valve, driving the water pump turbine and driving the bidirectional load generator to generate electricity.

[0018] As a preferred technical solution, the object-carrying system includes an object-carrying platform and foundation piles, the object-carrying platform is connected to the foundation piles, the foundation piles are fixed to the bottom of the seabed, and the object-carrying platform is connected to a high-pressure liquid storage tank, and the high-pressure liquid storage tank is arranged below the horizontal plane.

[0019] As a preferred technical solution, the liquid level monitoring system includes a float sensor, a float and a float base. The float sensor is also connected to a liquid level detector. The float sensor is used to collect float position change information and feed it back to the liquid level detector. The float base is connected to the float, and the float base is fixedly connected to the high-pressure liquid storage tank.

[0020] As a preferred technical solution, the air inlet and outlet are provided with an air filter.

[0021] As a preferred technical solution, a fixing system is also provided, which includes a net-cable structure and a fixing joint, the air filter is connected to the fixing joint through an underwater cable, and the fixing joint is connected to the net-cable structure.

[0022] As a preferred technical solution, the liquid inlet and outlet are provided with an underwater filter.

[0023] As a preferred technical solution, a spring device is provided inside the anti-wave damping valve, and different spring deformation amounts correspond to the hydrostatic pressure generated by different liquid surface wave heights.

[0024] As a preferred technical solution, a wind power generation device and a solar panel are also provided for storing energy at low power consumption or supplying power to the first electric valve, the second electric valve, and the bidirectional load energy conversion system;

[0025] And / or a storage battery is also provided for storing energy during off-peak hours or supplying power to the first electric valve, the second electric valve, and the bidirectional load energy conversion system.

[0026] The present invention also provides a control method for an underwater high-density stable hydraulic energy storage and release system, comprising the following steps:

[0027] During energy storage, the water pump turbine works in the water pump working condition, the bidirectional load generator works in the motor working condition, the first electric valve and the second electric valve are opened synchronously, the high-pressure liquid storage tank is in the drainage stage, and when the liquid level detector detects that the liquid level in the high-pressure liquid storage tank is 0, the first electric valve and the second electric valve are closed synchronously;

[0028] When releasing energy, the water pump turbine works in the water turbine working condition, the bidirectional load generator works in the generator working condition, the first electric valve and the second electric valve are opened synchronously, and the high-pressure liquid storage tank is in the water filling stage. When the liquid level detector detects that the liquid level in the high-pressure liquid storage tank reaches the preset full load height, the first electric valve and the second electric valve are closed synchronously;

[0029] The anti-wave damping valve dynamically adjusts the valve opening according to the wave height of the liquid surface to maintain the pressure on the high-pressure side of the pump turbine at a constant value.

[0030] As a preferred technical solution, the bidirectional load generator operates in the motor working condition, and the motor input power is:

[0031] ;

[0032] in, Indicates the input power of the motor. represents the density of water, represents the density of air, represents the acceleration due to gravity, Indicates the height of the filling and drainage pipe axis from the liquid surface. Indicates the liquid level in the high pressure liquid storage tank. Indicates the pressure difference of the anti-wave damping valve, represents the pump turbine flow rate, D Indicates the inner diameter of the filling and drainage pipe. Indicates the working efficiency of the pump. Indicates the efficiency of electric operation. It is controlled to a fixed value by the anti-wave damping valve;

[0033] And / or bidirectional load generator works in generator working condition, the generator output power is:

[0034] ;

[0035] in, represents the turbine operating efficiency, Indicates the efficiency of power generation operation;

[0036] The energy storage density is obtained based on the generator output power, which is expressed as:

[0037] ;

[0038] in, represents the energy storage density, It indicates the total time it takes for the high-pressure liquid storage tank to be filled with water until the liquid level reaches the preset full load height, that is, the continuous energy release time. t represents the time variable of the high-pressure liquid storage tank filling process, V Indicates the volume of the high pressure liquid storage tank.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0040] (1) The present invention utilizes the hydraulic power of seawater and the potential energy difference between the static pressure of deep-sea seawater and atmospheric pressure to construct a high-density stable hydraulic energy storage and release system, which can adapt to the fluctuation of unstable wind / solar power sources and make full use of external surplus electricity during the low-power consumption period, further promoting the flexible and efficient consumption of new energy and reducing the abandonment rate of wind and solar power.

[0041] (2) The present invention utilizes an anti-wave damping valve for feedforward dynamic adjustment. A spring device is provided inside the anti-wave damping valve. The hydrostatic pressure generated by different liquid surface wave heights corresponds to different spring deformations, thereby achieving the effect of dynamically adjusting the valve opening, realizing anti-wave feedforward dynamic adjustment of the inlet liquid pressure of the bidirectional load generator set, and cooperating with the second electric valve to achieve double-layer control of the filling and discharge flow rates, thereby solving the technical problem of unstable energy storage and release caused by seabed surges and sea surface fluctuations, and further enhancing the stability of the underwater hydraulic energy storage and release process, that is, achieving the effect of steady-state energy storage and release.

[0042] (3) Traditional pumped-storage power stations use the height difference between the upper and lower reservoirs to generate gravitational potential energy for power generation, and have strict requirements on geographical location. The present invention, however, is designed to achieve energy storage and release systems with different energy densities at different water depths, and is more suitable for on-site offshore wind power and photovoltaic power generation. It can realize the utilization of offshore renewable energy according to the distribution characteristics of offshore renewable energy power generation, alleviate the randomness, intermittency and volatility of offshore wind, light and other renewable energy sources, and has strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the overall structure of the underwater high-density stable hydraulic energy storage and release system of the present invention;

[0044] FIG2 (a) is a schematic diagram of the energy storage method of the underwater high-density stable hydraulic energy storage and release system of the present invention;

[0045] FIG2( b ) is a schematic flow chart of the energy release method of the underwater high-density stable hydraulic energy storage and release system of the present invention.

[0046] Among them, 1-wind power generation device, 2-solar panel, 3-load, 4-battery, 5-liquid level detector, 6-air filter, 7-water level, 8-atmospheric balance pipe, 9-first electric valve, 10-corrosion protection layer,

[0047] 11-float sensor, 12-float, 13-float base, 14-supporting platform, 15-foundation pile, 16-high-pressure liquid storage tank, 17-seabed, 18-bidirectional load generator, 19-pump turbine, 20-underwater filter, 21-spring device, 22-second electric valve, 23-anti-wave damping valve, 24-underwater cable, 25-net cable structure, 26-fixed joint, 27-filling and discharging pipes. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0049] Example 1

[0050] like Figure 1 As shown, this embodiment provides an underwater high-density stable hydraulic energy storage and release system, including: a load-bearing system, a high-pressure liquid storage tank 16, a liquid level monitoring system, a bidirectional load energy conversion system, and a fixing system;

[0051] The object-carrying system includes an object-carrying platform 14 and foundation piles 15. The object-carrying platform 14 and the foundation piles 15 are connected by corrosion-resistant flanges and sealing gaskets. In order to alleviate the impact of underwater surges, at least four vertical foundation piles 15 are installed at the lower end of the object-carrying platform 14 to enhance stability. The foundation piles 15 are fixed to the bottom of the seabed 17, thereby achieving a stabilizing effect.

[0052] In the present embodiment, the high-pressure liquid storage tank 16 is coated with a corrosion-resistant protective layer 10, and the energy storage and release process is realized by drainage and water filling. The lower end surface of the high-pressure liquid storage tank 16 is fixedly connected to the object-carrying platform 14, and can be fixed by welding. The upper end surface of the high-pressure liquid storage tank 16 is provided with a flexible and corrosion-resistant atmospheric balance pipe 8 to construct a pressure difference between the horizontal plane 7 and the high-pressure liquid storage tank 16 at a set depth. A first electric valve 9 is provided inside the atmospheric balance pipe 8, which is opened or closed synchronously with the second electric valve 22 to switch the air intake and exhaust state. One end of the atmospheric balance pipe 8 is connected to the high-pressure liquid storage tank 16, and the other end extends to a position higher than the horizontal plane 7 as an air inlet and outlet. An air filter 6 is provided at the air inlet and outlet. A filling and drainage pipe 27 is provided on one side of the high-pressure liquid storage tank 16. One end of the filling and drainage pipe 27 is connected to the high-pressure liquid storage tank 16, and the other end extends to a position lower than the horizontal plane 7 as a liquid inlet and outlet.

[0053] In this embodiment, the atmospheric balance pipe 8 and the filling and discharging pipe 27 both adopt a pressure-resistant flexible structure, which can effectively resist the influence of waves and thus adapt to the underwater fluctuating environment.

[0054] In this embodiment, the bidirectional load energy conversion system includes a bidirectional load generator 18 and a pump turbine 19;

[0055] Specifically, an underwater filter 20, a second electric valve 22 and an anti-wave damping valve 23 are arranged at the front end of the bidirectional load generator 18 and the pump-turbine 19. The anti-wave damping valve 23 generates dynamic hydrostatic pressure according to the wave height of the liquid surface, and dynamically adjusts the opening of the valve. Specifically, a spring device 21 is arranged inside the anti-wave damping valve 23. The hydrostatic pressure generated by different liquid surface wave heights corresponds to different spring deformation amounts, so as to achieve the effect of dynamically adjusting the valve opening, keep the pressure on the high-pressure side of the pump-turbine 19 at a constant value, and then keep the liquid pressure flowing into the high-pressure liquid storage tank 16 at a constant value, realize the stable conversion of energy, thereby eliminating the influence of waves on the power of the bidirectional load energy conversion system and realizing a steady-state process; during the filling process of the high-pressure liquid storage tank 16, water enters the high-pressure liquid storage tank 16 through the underwater filter 20, the second electric valve 22, etc., and the liquid drives the pump-turbine 19 to operate stably, thereby driving the bidirectional load generator 18 to generate electricity and realize the release of energy;

[0056] In this embodiment, the liquid level monitoring system is arranged inside the high-pressure liquid storage tank 16, and the liquid level depth in the high-pressure liquid storage tank 16 is monitored in real time to achieve the purpose of real-time monitoring of the storage and release energy state. The liquid level monitoring system includes a float sensor 11, a float 12 and a float base 13. The upper end of the float sensor 11 is connected to the liquid level detector 5. The float sensor 11 collects the position change information of the float 12 and feeds it back to the liquid level detector. The liquid level detector obtains the liquid level information of the high-pressure liquid storage tank in real time. The liquid storage volume can be obtained according to the liquid level depth in the high-pressure liquid storage tank. The energy storage density can be calculated in combination with the output power of the generator for energy storage system design.

[0057] A float base 13 is provided at the lower end of the float 12, and the float base 13 is installed inside the high-pressure liquid storage tank 16, and the float base 13 and the high-pressure liquid storage tank 16 are fixed by a corrosion-resistant flange;

[0058] In this embodiment, the fixing system includes a net cable structure 25 and a fixed joint 26. The air filter 6 is connected to the underwater cable 24 and the fixed joint 26. The fixed joint 26 is connected to the net cable structure 25. The air filter 6 is fixed by gravity anchor with the help of the net cable structure 25 that carries heavy objects. The net cable structure 25 is preferably a rubber bag, and the fixed joint 26 is preferably a stainless steel joint, which is connected to the air filter through the underwater cable 24 to fix the air filter.

[0059] Specifically, two lifting rings need to be provided on the lower end surface of the air filter 6 to facilitate connection with the underwater cable 24 .

[0060] In this embodiment, the atmospheric balance pipe 8, the filling and drainage pipe 27, the support platform 14, the foundation pile 15, the high-pressure liquid storage tank 16, and the mesh cable structure 25 are all coated with sealing, corrosion-resistant and heat-insulating materials.

[0061] In this embodiment, a wind power generation device 1 and a solar panel 2 are also provided for storing and utilizing energy. The wind power generation device 1 and the solar panel 2 can store energy during the low electricity consumption period to improve the energy waste situation. During the peak electricity consumption period, the wind power generation device 1 and the solar panel 2 can supply energy to various electric valves, generator sets, etc. to improve the peak-shaving capacity.

[0062] In this embodiment, a load 3 and a battery 4 are also included, and the load 3 and the battery 4 are used to enhance the flexibility of regulating the distribution of electricity during the off-peak period and the peak period.

[0063] Example 2

[0064] As shown in FIG. 2 (a) and FIG. 2 (b), this embodiment provides a control method for an underwater high-density stable hydraulic energy storage and release system, which is provided with the underwater high-density stable hydraulic energy storage and release system of the above-mentioned embodiment 1, wherein stable energy storage and release is achieved by the cooperation of a high-pressure liquid storage tank, an anti-wave damping valve, a first electric valve, and a second electric valve, specifically comprising:

[0065] The two stages of energy storage and energy release correspond to the drainage and filling processes of the high-pressure liquid storage tank respectively. In the drainage process, the water pump turbine works in the water pump condition, and the bidirectional load energy conversion system works in the motor condition; in the filling process, the water pump turbine works in the turbine condition, and the bidirectional load energy conversion system works in the generator condition.

[0066] In the drainage stage, the first electric valve 9 and the second electric valve 22 are opened synchronously, and the water pump turbine 19 works in the water pump working condition. When the liquid level detector detects that the liquid level in the high-pressure liquid storage tank is 0, the first electric valve 9 and the second electric valve 22 are closed synchronously;

[0067] In the water filling stage, the first electric valve 9 and the second electric valve 22 are opened synchronously, the water pump turbine 19 works in the water turbine working condition, and the seabed water passes through the underwater filter 20, the anti-wave damping valve 23, the second electric valve 22, the water pump turbine 19, and finally enters the high-pressure liquid storage tank 16. When the liquid level detector detects that the liquid level in the high-pressure liquid storage tank reaches the preset full load height, the first electric valve 9 and the second electric valve 22 are closed synchronously, and the water filling is completed;

[0068] In this embodiment, the anti-wave damping valve 23 receives the signal of the liquid pressure of different liquid surface wave heights, dynamically changes the deformation of the spring device 21, further adjusts the opening of the anti-wave damping valve 23, and uses the precise control ability of the second electric valve 22 to adjust the fluid flow rate according to actual needs, thereby achieving a double-layer control effect;

[0069] Set the liquid pressure behind the second electric valve 22 p0, in order to maintain steady-state operation, the opening of the anti-wave damping valve 23 can be dynamically adjusted according to the wave height of the liquid surface to keep the pressure on the high-pressure side of the pump turbine at a constant value, thereby eliminating the influence of waves on the power of the bidirectional load energy conversion system, and then realizing constant pressure energy storage and release;

[0070] Assume that the densities of water and air are and , the height of the filling and drainage pipe axis from the liquid surface is h ; Hydrostatic height of anti-wave damping valve h 0, set to a fixed value; the liquid level in the high-pressure liquid storage tank is ; The inner diameter of the filling and drainage pipe is D ; Pump turbine flow rate is ; The pressure difference of the anti-wave damping valve is ; The efficiency of the water pump and the electric motor are , The turbine operating efficiency and power generation efficiency are , .

[0071] In this embodiment, the height of the filling and drainage pipe axis from the liquid surface h :

[0072] ;

[0073] Among them, Δ H is the horizontal elevation difference between the anti-wave damping valve and the filling and discharge pipes, which is a constant.

[0074] Relative pressure at the inlet of the second electric valve 22 for:

[0075] ;

[0076] in, δ is the wave height, Δ p The pressure difference of the anti-wave damping valve is controlled by the deformation of the spring device, so Can be controlled to be a constant.

[0077] Therefore, the relative pressure at the inlet of the second electric valve Can be controlled as a constant, that is It is controlled to a fixed value by the anti-wave damping valve.

[0078] The motor input power can be obtained through the above parameters E 1. Generator output power E 2 and energy storage density .

[0079] During the drainage process, the electric power input to the motor is:

[0080] ;

[0081] in, is the local gravitational acceleration, h 0 represents the hydrostatic action height of the anti-wave damping valve, which is set to a fixed value. The hydrostatic pressure fluctuations generated by the waves are automatically balanced by the deformation of the spring device. It is controlled to a fixed value by the anti-wave damping valve;

[0082] During the water filling process, the generator output power is:

[0083] ;

[0084] Energy storage density: ;

[0085] in, represents the energy storage density, It indicates the total time it takes for the high-pressure liquid storage tank to be filled with water until the liquid level reaches the preset full load height, that is, the continuous energy release time. t represents the time variable of the high-pressure liquid storage tank filling process, V Indicates the volume of the high pressure liquid storage tank.

[0086] During the period of low electricity consumption, due to the reduction of demand-side load, there is excess power output. Part of the excess power is supplied to end users such as load 3 and battery 4 through the energy recovery system, and the other part can be transmitted to power-consuming equipment such as bidirectional load generator 18, first electric valve 9 and second electric valve 22.

[0087] During peak hours of electricity consumption, the direct current stored in the battery 4 is supplied to the first electric valve 9 and the second electric valve 22. After the gas in the high-pressure liquid storage tank 16 is discharged through the atmospheric balance pipe 8 and the first electric valve 9, the corresponding volume of water enters the high-pressure liquid storage tank 16 through the underwater filter 20, the second electric valve 22 and the anti-wave damping valve 23, and drives the water pump turbine 19 to rotate, thereby outputting electrical energy.

[0088] The liquid flowing into the high-pressure liquid storage tank 16 maintains a stable flow, and the valve opening is flexibly adjusted according to the liquid surface wave height to keep the pressure on the high-pressure side of the pump turbine at a constant value, thereby eliminating the influence of waves on the power of the bidirectional load energy conversion system.

[0089] This embodiment dynamically adjusts the opening of the anti-wave damping valve according to the wave height of the liquid surface, maintains the pressure on the high-pressure side of the pump turbine at a constant value, thereby eliminating the influence of waves on the power of the bidirectional load energy conversion system, and ultimately achieving a stable energy storage and release process.

[0090] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An underwater high-density stable hydraulic energy storage and release system, characterized in that: include: Carrying system, high-pressure liquid storage tank, liquid level monitoring system and bidirectional load energy conversion system; The object-carrying system is connected to a high-pressure liquid storage tank, and the liquid level monitoring system is arranged in the high-pressure liquid storage tank to monitor the liquid level depth of the high-pressure liquid storage tank; An atmospheric balance pipe is provided on the upper end surface of the high-pressure liquid storage tank, one end of the atmospheric balance pipe is connected to the high-pressure liquid storage tank, and the other end of the atmospheric balance pipe extends to a position above the horizontal plane as an air inlet and outlet. A first electric valve is provided in the atmospheric balance pipe for switching the air intake and exhaust state; A filling and drainage pipe is provided on one side of the high-pressure liquid storage tank, one end of the filling and drainage pipe is connected to the high-pressure liquid storage tank, and the other end of the filling and drainage pipe extends to a position below the horizontal plane to serve as a liquid inlet and outlet; The bidirectional load energy conversion system includes a bidirectional load generator and a water pump turbine. A second electric valve and an anti-wave damping valve are provided in the filling and discharge pipes. The second electric valve is used to switch the liquid inlet and outlet states. The anti-wave damping valve is used to dynamically adjust the valve opening according to the liquid surface wave height. When storing energy, the water pump turbine cooperates with the first electric valve, the second electric valve and the anti-wave damping valve to discharge the water from the high-pressure liquid storage tank. When releasing energy, water enters the high-pressure liquid storage tank through the second electric valve and the anti-wave damping valve, driving the water pump turbine and driving the bidirectional load generator to generate electricity. During energy storage, the pump turbine works in the pump condition, the bidirectional load generator works in the motor condition, and the motor input power is: ； in, Indicates the input power of the motor. represents the density of water, represents the density of air, represents the acceleration due to gravity, Indicates the height of the filling and drainage pipe axis from the liquid surface. Indicates the liquid level in the high pressure liquid storage tank. Indicates the pressure difference of the anti-wave damping valve, represents the pump turbine flow rate, D Indicates the inner diameter of the filling and drainage pipe. Indicates the working efficiency of the pump. Indicates the efficiency of electric operation. It is controlled to a fixed value by the anti-wave damping valve; When releasing energy, the pump turbine works in turbine condition, the bidirectional load generator works in generator condition, and the generator output power is: ； in, represents the turbine operating efficiency, Indicates the efficiency of power generation operation; The energy storage density is obtained based on the generator output power, which is expressed as: ； in, represents the energy storage density, It indicates the total time it takes for the high-pressure liquid storage tank to be filled with water until the liquid level reaches the preset full load height, that is, the continuous energy release time. t represents the time variable of the high-pressure liquid storage tank filling process, V Indicates the volume of the high pressure liquid storage tank.

2. The underwater high-density stable hydraulic energy storage and release system according to claim 1, characterized in that: The object-carrying system comprises an object-carrying platform and foundation piles, wherein the object-carrying platform is connected to the foundation piles, the foundation piles are fixed to the bottom of the seabed, and the object-carrying platform is connected to a high-pressure liquid storage tank, which is arranged below the horizontal plane.

3. The underwater high-density stable hydraulic energy storage and release system according to claim 1, characterized in that: The liquid level monitoring system includes a float sensor, a float and a float base. The float sensor is also connected to a liquid level detector. The float sensor is used to collect float position change information and feed it back to the liquid level detector. The float base is connected to the float, and the float base is fixedly connected to the high-pressure liquid storage tank.

4. The underwater high-density stable hydraulic energy storage and release system according to claim 1, characterized in that: The air inlet and outlet are provided with an air filter.

5. The underwater high-density stable hydraulic energy storage and release system according to claim 4, characterized in that: A fixing system is also provided, which includes a net-cable structure and a fixing joint. The air filter is connected to the fixing joint through an underwater cable, and the fixing joint is connected to the net-cable structure.

6. The underwater high-density stable hydraulic energy storage and release system according to claim 1, characterized in that: The liquid inlet and outlet are provided with an underwater filter.

7. The underwater high-density stable hydraulic energy storage and release system according to claim 1, characterized in that: A spring device is arranged inside the anti-wave damping valve, and different spring deformation amounts correspond to the hydrostatic pressure generated by different liquid surface wave heights.

8. The underwater high-density stable hydraulic energy storage and release system according to claim 1, characterized in that: A wind power generation device and a solar panel are also provided to store energy at low power consumption or to supply power to the first electric valve, the second electric valve, and a two-way load energy conversion system; And / or a storage battery is also provided for storing energy during off-peak hours or supplying power to the first electric valve, the second electric valve, and the bidirectional load energy conversion system.

9. The control method of the underwater high-density stable hydraulic energy storage and release system according to any one of claims 1 to 8, characterized in that: The steps include: During energy storage, the water pump turbine works in the water pump working condition, the bidirectional load generator works in the motor working condition, the first electric valve and the second electric valve are opened synchronously, the high-pressure liquid storage tank is in the drainage stage, and when the liquid level detector detects that the liquid level in the high-pressure liquid storage tank is 0, the first electric valve and the second electric valve are closed synchronously; When releasing energy, the water pump turbine works in the water turbine working condition, the bidirectional load generator works in the generator working condition, the first electric valve and the second electric valve are opened synchronously, and the high-pressure liquid storage tank is in the water filling stage. When the liquid level detector detects that the liquid level in the high-pressure liquid storage tank reaches the preset full load height, the first electric valve and the second electric valve are closed synchronously; The anti-wave damping valve dynamically adjusts the valve opening according to the wave height of the liquid surface to maintain the pressure on the high-pressure side of the pump turbine at a constant value.

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