Seabed pumped storage system and working method and maintenance method thereof

Abstract

The invention relates to a seabed pumped storage system and a working method and a maintenance method thereof. The system comprises an energy storage shell, a low-pressure cavity is formed after seawater is pumped out of the shell, and gravitational potential energy is stored through the difference between external deep sea hydrostatic pressure and internal low pressure; the energy storage sleeve is detachably connected with the energy storage shell in a sealed mode through a flange. A breather pipe and a water conveying pipeline are integrated in the energy storage sleeve. The deepwater ball valve, the reversible water pump / water turbine and the coaxial motor / generator are sequentially arranged from top to bottom in the axial direction of the water conveying pipeline. Under the energy storage working condition, the unit in the energy storage sleeve discharges seawater in the shell to deep sea, and energy storage is completed; under the energy release working condition, high-pressure seawater flows back to drive the water turbine to generate electricity. When the system is maintained, a sea surface work ship vertically pulls the whole set of cylinder to a deck through a hoisting system, core component maintenance or whole replacement is completed in a normal pressure environment and then reinstallation is performed, and deep diving operation is not needed. In-situ large-scale energy storage of the deep and far sea renewable power supply is realized, and the operation and maintenance cost and risk are remarkably reduced.

Description

Technical Field

[0001] This invention relates to the fields of marine engineering technology and marine energy storage technology, specifically to a subsea pumped storage system and its working and maintenance methods. Background Technology

[0002] As the global energy structure shifts towards renewable energy, offshore wind power has become an important direction for clean energy development due to its abundant resources, stable wind speeds, and lack of reliance on land resources. However, like all wind power, offshore wind power suffers from significant intermittency and volatility, with its output varying drastically with wind speed and being difficult to predict accurately. This instability poses a significant challenge to the real-time power balance and safe and stable operation of the power grid, often leading to curtailment and energy waste, and hindering the large-scale, high-proportion grid connection and consumption of offshore wind power.

[0003] To address this issue, equipping wind power with large-scale, long-term energy storage systems to achieve "on-site storage and stable transmission" is a key technological path for promoting the sustainable development of deep-sea wind power. Currently, on land, pumped hydro storage is the most mature, largest-capacity, and most economical energy storage method. Applying its principles to the marine environment to construct subsea pumped hydro storage systems, utilizing the natural high water pressure of the deep seabed as a reservoir, and converting potential energy into electrical energy by filling and draining seawater into subsea tanks, is one of the better options for solving the problem of on-site energy storage for offshore wind power.

[0004] However, deploying pumped-storage hydroelectric systems on the seabed presents extremely severe maintenance and repair challenges. The seabed environment is characterized by high pressure, strong corrosiveness, and poor accessibility. Traditionally, any maintenance of core rotating equipment such as generators, pumps, and turbines relies on large deep-sea submersibles or complex saturation diving systems for underwater operations. This method is not only time-consuming and extremely risky, but also incredibly expensive, becoming a major bottleneck restricting the commercialization of seabed pumped-storage technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a subsea pumped storage system and its operating and maintenance methods to solve the aforementioned problems.

[0006] This invention provides the following technical solution: A subsea pumped-storage energy system includes: an energy storage shell fixed to the seabed, with a low-pressure chamber formed inside by pumping out water, storing potential energy using the pressure difference between the external deep-sea high pressure and the internal low pressure; an energy storage sleeve connected to the energy storage shell in a detachable and sealed manner, with a vent pipe and a water supply pipe installed inside the sleeve; the lower end of the vent pipe connects to the interior of the energy storage shell, and the upper end extends above the sea surface to communicate with the atmosphere; the lower end of the water supply pipe connects to the interior of the energy storage shell, and the upper end connects to the deep sea; a deep-water ball valve, a water pump / turbine, and a motor / generator are arranged sequentially from top to bottom along the axial direction of the water supply pipe; wherein, the deep-water ball valve is located at the top of the energy storage shell; the water pump / turbine acts as a water pump to draw seawater from the shell during energy storage, and acts as a water turbine driven to rotate by the high-pressure seawater during energy release; the motor / generator is coaxially connected to the water pump / turbine, and acts as a motor to drive the water pump during energy storage, and as a generator to output electrical energy during energy release.

[0007] Furthermore, the energy storage sleeve is connected to the energy storage shell via a connecting flange.

[0008] Furthermore, the energy storage sleeve is connected to the upper flange of the sealing hatch neck on the top of the energy storage shell via the connecting flange at its top.

[0009] Furthermore, the system also includes a flow meter installed on the water supply pipeline for real-time measurement of the flow rate of seawater entering and exiting the shell.

[0010] Furthermore, the system also includes a watertight chamber fixed to the upper part of the energy storage sleeve, which is filled with dry air or inert gas.

[0011] Furthermore, a control system is installed inside the watertight compartment.

[0012] This invention also discloses a working method for the aforementioned subsea pumped storage system, including an energy storage mode and an energy release mode. In the energy storage mode, when there is excess electrical energy from offshore wind or wave power, the electric motor / generator operates as an electric motor, thereby driving the water pump / turbine to operate as a water pump. The deep-water ball valve opens, and the water pump extracts seawater from the energy storage shell. When all the seawater is extracted, the energy storage reaches its maximum value. In the energy release mode, when the power consumer requires additional power, the deep-water ball valve opens, and under the immense hydrostatic pressure of the deep sea, seawater enters the water delivery pipeline, driving the water turbine to rotate, thereby driving the generator to operate and supplying electrical energy to the power consumer.

[0013] Furthermore, the control system adjusts the pump power or generator power based on the data monitored in real time by the flow meter.

[0014] This invention also discloses a maintenance method for the aforementioned subsea pumped storage system, comprising the following steps: S1, a surface workboat is positioned above the system, and an inspection is assisted by a remotely operated vehicle (ROV), using the ship's hoisting system to connect to the top of the energy storage sleeve; S2, after disconnecting the electrical connection, the flange connection device is unlocked, the energy storage sleeve is vertically extracted from the energy storage shell, lifted to the sea surface, and transferred to the deck; S3, the core equipment inside the sleeve is inspected or replaced entirely under the normal pressure environment on the deck; S4, after the inspection is completed, the energy storage sleeve is lowered back down, aligned, inserted into the energy storage shell, and the flange is locked, the electrical connection is restored, and the system can resume operation.

[0015] The present invention has the following beneficial technical effects: The system of this invention is directly deployed at the bottom of wind power or wave energy fields. The system relies only on water depth and hydrostatic pressure, does not require canyon terrain, shares sea area with floating wind power, marine ranches, oil and gas platforms, saves land storage resources, has minimal impact on marine ecology, and utilizes the gravitational potential energy difference between deep-sea hydrostatic pressure and low-pressure cavity inside the shell to achieve "on-site storage and stable transmission". It can smooth the intermittency and fluctuation of wind power and wave energy, significantly reduce wind curtailment rate, and reduce investment in long-distance submarine cables.

[0016] This invention integrates all core components such as electric motors / generators, water pumps / turbines, and deep-water ball valves into a single removable energy storage sleeve. When maintenance is required, the entire energy storage sleeve can be vertically pulled to the deck by a surface work vessel, and inspection, repair, or complete replacement can be carried out under normal pressure and temperature conditions, completely eliminating the need for traditional saturation diving or large deep-sea submersible operations and reducing operation and maintenance costs. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the integrated structure of the energy storage sleeve of the present invention; Figure 2 This is a schematic diagram of the overall structure of the subsea pumped storage system of the present invention; Figure 3 This is a schematic diagram of the connection structure between the energy storage shell and the energy storage sleeve of the present invention.

[0018] The attached figures are labeled as follows: 1. Energy storage shell; 11. Sealed hatch neck; 2. Energy storage sleeve; 21. Connecting flange; 22. Electric motor / generator; 23. Water pump / turbine; 24. Drive shaft and coupling; 25. Sensing device; 3. Vent pipe; 4. Water supply pipeline; 5. Deepwater ball valve; 6. Watertight compartment. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 This invention discloses a subsea pumped-storage energy system, comprising: an energy storage shell 1, fixed to the seabed, with a low-pressure chamber formed inside by pumping out water, utilizing the pressure difference between the external deep-sea high pressure and the internal low pressure to store potential energy. In this embodiment, the shell size can be designed according to the water depth and energy storage scale to adapt to different scenarios. The energy storage shell 1 is made of high-strength corrosion-resistant alloy or prestressed concrete and is fixed to the seabed by a foundation; an energy storage sleeve 2 is detachably and sealed to the energy storage shell 1, and a vent pipe 3 and a water supply pipe 4 are installed inside the energy storage sleeve 2; the vent pipe 3 is a steel wire braided flexible hose, with its lower end connected to the interior of the energy storage shell 1 and its upper end extending above the sea surface to communicate with the atmosphere, used to maintain the pressure balance inside the energy storage shell 1; the water supply pipe 4 is a corrosion-resistant and high-pressure-resistant composite material pipe. The system consists of a water pipeline 4, with its lower end connected to the interior of the energy storage shell 1 and its upper end connected to the deep sea. The pipeline serves as a transmission channel, enabling bidirectional seawater flow. A deep-water ball valve 5, a water pump / turbine 23, and a motor / generator 22 are arranged axially from top to bottom along the water pipeline 4. The deep-water ball valve 5 is located at the top of the energy storage shell 1, does not occupy energy storage space, and can be remotely adjusted according to power demand to control real-time power generation. It can also cut off high-pressure water flow during maintenance or emergencies to ensure system safety. The water pump / turbine 23 acts as a pump to extract seawater from the shell during energy storage and as a turbine driven by high-pressure seawater during energy release. The motor / generator 22 is coaxially connected to the water pump / turbine, acting as a motor to drive the pump during energy storage and as a generator to output electrical energy during energy release.

[0021] In this embodiment, the energy storage housing 1 has a sealed hatch with a sealing seat at its top. The energy storage sleeve 2 is made of high-strength corrosion-resistant alloy and is connected to the energy storage housing 1 via a connecting flange 21 for easy installation and disassembly. Specifically, the energy storage sleeve 2 is connected to the upper flange of the sealing hatch neck 11 at the top of the energy storage housing 1 via the connecting flange 21 at its top. The integrated removable energy storage sleeve 2 has a cylindrical structure with a diameter smaller than the inspection hole, allowing it to be inserted into or removed from the energy storage housing 1 as a whole through this hole.

[0022] The system also includes a sensing device 25 for monitoring parameters such as internal and external pressure, internal water level, equipment temperature, and vibration of the energy storage shell 1. In this embodiment, a flow meter installed on the water supply pipe 4 is included to measure the flow rate of seawater entering and exiting the shell in real time, providing crucial data for system control, efficiency calculation, and condition assessment. The system also includes a watertight chamber 6, fixed to the upper part of the energy storage sleeve, for housing and protecting related instruments and equipment of the control system, providing a normal-pressure, dry working environment for the equipment, and its interior is filled with dry air or inert gas.

[0023] In this embodiment, the deep-water ball valve 5 is welded to the water supply pipeline 4, and the watertight chamber 6 is threaded or welded to the energy storage sleeve 2.

[0024] This invention integrates all core components through the energy storage sleeve 2, enabling rapid installation and disassembly of the system.

[0025] Example 2 This invention also discloses a method for operating a subsea pumped storage system according to Embodiment 1, including an energy storage mode and an energy release mode. In the energy storage mode, when there is excess electrical energy from offshore wind or wave power, the electric motor / generator operates as an electric motor, thereby driving the water pump / turbine to operate as a water pump. The deep-water ball valve opens, and the water pump extracts seawater from the energy storage shell. When all the seawater is extracted, the energy storage reaches its maximum value. During this process, the flow meter monitors the pumping flow rate in real time, and the control system adjusts the pump power accordingly. In the energy release mode, when the power consumer requires additional power, the deep-water ball valve opens, and under the enormous hydrostatic pressure of the deep sea, seawater enters the water delivery pipeline, driving the turbine to rotate, thereby driving the generator to operate and supplying electrical energy to the power consumer. During this process, the flow meter monitors the seawater flow rate in real time, and the control system adjusts the power generation power.

[0026] This invention designs a novel subsea energy storage system, forming a large-scale energy storage solution suitable for marine new energy sources.

[0027] Example 3 This invention also discloses a maintenance method for a subsea pumped storage system according to Embodiment 1, comprising the following steps: S1, a surface workboat is positioned above the system, and an ROV (Remotely Operated Vehicle) is used for assisted inspection. The workboat is connected to the top of the energy storage sleeve 2 using its hoisting system. Specifically, the connection can be made via a steel cable to the lifting lugs on the top of the energy storage sleeve 2; S2, after disconnecting the electrical connection, the flange connection device is unlocked, and the energy storage sleeve is vertically pulled out of the energy storage shell, lifted to the sea surface, and transferred to the deck. Specifically, a guide rail can be set to ensure that the extraction process is free from jamming; S3, the core equipment inside the sleeve is inspected or replaced entirely under normal pressure on the deck, or a good spare energy storage sleeve is used for replacement; S4, after the inspection is completed, the energy storage sleeve 2 is lowered back down, aligned, inserted into the energy storage shell, and the flange is locked. The electrical connection is restored, and the system can resume operation.

[0028] This invention integrates the core equipment, the energy storage sleeve 2, which is extracted entirely from the seabed energy storage shell 1 for comfortable and efficient maintenance on the sea surface or shore. After maintenance or replacement with a spare sleeve, it is reinserted and locked. This method can also employ a "component replacement maintenance" strategy, directly replacing the faulty sleeve with a spare sleeve to minimize system downtime.

[0029] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A subsea pumped storage system, characterized in that, include: The energy storage shell is fixed to the seabed. Inside, a low-pressure chamber is formed by pumping out water, and potential energy is stored by utilizing the pressure difference between the high pressure of the external deep sea and the low pressure inside. An energy storage sleeve is detachably and sealed to the energy storage shell. A vent pipe and a water supply pipe are installed inside the energy storage sleeve. The lower end of the vent pipe is connected to the interior of the energy storage shell, and the upper end extends above the sea surface to communicate with the atmosphere. The lower end of the water supply pipe is connected to the interior of the energy storage shell, and the upper end is connected to the deep sea. The deep-water ball valve, water pump / turbine, and motor / generator are arranged sequentially from top to bottom along the axial direction of the water pipeline; wherein, the deep-water ball valve is located at the top of the energy storage shell; The pump / turbine functions as a pump to extract seawater from the shell under energy storage conditions, and as a turbine driven to rotate by high-pressure seawater under energy release conditions. The electric motor / generator is coaxially connected to the water pump / turbine. In the energy storage mode, it drives the water pump as an electric motor, and in the energy release mode, it outputs electrical energy as a generator.

2. The subsea pumped storage system according to claim 1, characterized in that, The energy storage sleeve is connected to the energy storage shell via a connecting flange.

3. The subsea pumped storage system according to claim 2, characterized in that, The energy storage sleeve is connected to the upper flange of the sealing hatch neck on the top of the energy storage shell via the connecting flange at its top.

4. A subsea pumped storage system according to claim 1, characterized in that, The system also includes a flow meter installed on the water supply pipeline for measuring the flow rate of seawater entering and exiting the shell in real time.

5. A subsea pumped storage system according to claim 1, characterized in that, The system also includes a watertight chamber, fixed to the upper part of the energy storage sleeve, which is filled with dry air or inert gas.

6. A subsea pumped storage system according to claim 5, characterized in that, The watertight compartment is equipped with a control system.

7. A method for operating a subsea pumped storage system according to claim 1, characterized in that, Including energy storage and energy release operating conditions; In the energy storage mode, when there is excess electrical energy from offshore wind power or wave energy, the motor / generator operates as a motor, which in turn drives the water pump / turbine to work as a water pump. The deep-water ball valve opens, and the water pump draws seawater out of the energy storage shell. When all the seawater is drawn out, the energy storage reaches its maximum value. Under the energy release condition, when the power-consuming end needs additional power, the deep-water ball valve opens, and under the huge hydrostatic pressure of the deep sea, seawater enters the water pipeline, drives the water turbine to rotate, and then drives the generator to run, transmitting electrical energy to the power-consuming end.

8. The working method according to claim 7, characterized in that, The control system adjusts the power of the water pump or the power generation based on the data monitored in real time by the flow meter.

9. A maintenance method for a subsea pumped storage system according to claim 1, characterized in that, Includes the following steps: S1, the surface workboat is positioned above the system, and an inspection is assisted by a remotely operated vehicle (ROV). The workboat is then connected to the top of the energy storage sleeve using the onboard hoisting system. S2, after disconnecting the power connection, unlock the flange connection device, vertically pull the energy storage sleeve out of the energy storage shell, lift it to the sea surface and transfer it to the deck; S3, to inspect or replace the core equipment inside the sleeve under normal pressure on the deck; S4. After completing the maintenance, lower the energy storage sleeve back down, align it, insert it into the energy storage housing, and lock the flange. Restore the electrical connection, and the system can resume operation.

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