Pumped hydro compressed gas energy storage system and retrofit method for conventional hydroelectric power stations

Abstract

The application discloses a pumped compressed gas energy storage system and a method for transforming a conventional hydropower station. The system adjusts the flow and lift of the pumping subsystem by dynamic reconfiguration of the series-parallel connection of multiple pump units, improves the equipment utilization rate of the pumping subsystem; the pressure vessel subsystem reduces the internal and external pressure difference of the pressure vessel, reduces the technical requirements of the energy storage system on the pressure vessel through the shared vessel wall, improves the safety and reduces the cost. The pumped compressed gas energy storage system is applied to the transformation of the conventional hydropower station, and the conventional hydropower station is transformed into a pumped storage power station. The pumped compressed gas energy storage system can work independently, and each component unit of the energy storage system can be arranged at a suitable position in and around the conventional hydropower station to transform the conventional hydropower station into a pumped compressed gas energy storage station.

Description

Technical Field

[0001] This invention relates to the field of energy storage in novel power systems, and more particularly to a pumped compressed gas energy storage system and its method for retrofitting conventional hydropower stations. Background Technology

[0002] Renewable energy sources such as solar and wind power are accounting for an increasingly larger proportion of the power system. However, these energy sources are subject to constraints from natural conditions and have low controllability, necessitating the deployment of substantial energy storage capacity within the power system to meet reliability requirements. Common energy storage forms include pumped hydro storage, compressed gas storage (CGS), and electrochemical energy storage. Pumped hydro storage offers advantages such as large capacity and high storage efficiency, but its application is limited by stringent site selection requirements, long construction periods, and its location far from load centers. Compressed gas storage suffers from relatively low efficiency due to significant heat exchange during compression and expansion, requiring improvements such as supplemental combustion. Furthermore, the large storage capacity of CGS also restricts power plant site selection. Electrochemical energy storage offers high storage efficiency and rapid response, but it suffers from lower safety, shorter lifespan, and the environmental pollution risks associated with the post-processing of energy storage batteries.

[0003] During the process of feeding water into the pressure vessel, the increase in water volume compresses air, causing significant pressure variations inside the vessel. A single water pump struggles to adapt to these large pressure fluctuations, and even with variable frequency drives to improve efficiency, equipment utilization remains low. Furthermore, the increased pressure places greater stress on the pressure vessel, increasing the risk to safe operation and raising the overall operating costs of the energy storage system.

[0004] The literature “A High-Pressure Insulated Gas Storage Pumped Compressed Gas Energy Storage System” (ZL201810291346X) reduces energy loss through insulation, but cannot reduce the energy consumed by energy storage.

[0005] The literature "A hydraulic water pump that can be quickly connected in series" (Tang Lijian, Cao Suhua, Ni Xianwenguang. A hydraulic water pump that can be quickly connected in series [P]. Hunan Province: CN213206128U, 2021-05-14.) cannot achieve dynamic adjustment of the connection method.

[0006] The document "A Water Source Heat Pump Series Energy-Saving Water Pump System" (Yang Wei, Zhang Linlin. A Water Source Heat Pump Series Energy-Saving Water Pump System [P]. Henan Province: CN212299550U, 2021-01-05.) cannot achieve dynamic adjustment of the connection method.

[0007] The document "A series composite power water pump and a heat pump system including the series composite power water pump" (Xie Meng, Xu Hongyan, Tong Yilun, Tong Xianwen. A series composite power water pump and a heat pump system including the series composite power water pump [P]. Hunan: CN108443101A, 2018-08-24.) cannot achieve dynamic adjustment of the connection method.

[0008] The document "A Parallel Water Pumping Device" (Chen Jinhui, Dai Zixi, Li Jie. A Parallel Water Pumping Device [P]. Fujian Province: CN210658178U, 2020-06-02.) cannot achieve dynamic adjustment of the connection method. Summary of the Invention

[0009] This invention provides a pumped compressed gas energy storage system and its method for retrofitting conventional hydropower stations. By dynamically reconfiguring multiple pump units in series and parallel, the flow rate and head of the pumping subsystem are adjusted, thereby improving the equipment utilization rate of the pumping subsystem. The pressure vessel subsystem adopts nested, stacked, and combined structures to reduce the internal and external pressure difference of the pressure vessel, and reduces the technical requirements of the energy storage system on the pressure vessel by sharing the vessel wall, thereby improving safety and reducing costs. By applying this system to the retrofitting of conventional hydropower stations, conventional hydropower stations can be transformed into pumped storage power stations.

[0010] The objective of this invention is achieved by at least one of the following technical solutions.

[0011] A pumped compressed gas energy storage system includes a pumping subsystem, a pressure vessel subsystem, a water turbine, a motor subsystem, and a water storage tank;

[0012] The pumping subsystem includes multiple series-parallel switching valves and multiple pump units coaxially mounted. The pump units are driven by the motor subsystem. Adjacent pump units are connected through series-parallel switching valves, and the series-parallel, parallel, or mixed series-parallel connections between the pump units are realized through the series-parallel switching valves.

[0013] The pressure vessel subsystem includes multiple nested, stacked, and nested-stacked composite pressure vessel units. Each pressure vessel unit of the pressure vessel subsystem is connected to the main pipeline through its own inlet and outlet water pipes. When pumping water for energy storage, the main pipeline is connected to the pumping water pipes of the pumping subsystem. When generating electricity, the main pipeline is connected to the turbine through the power generation pipes.

[0014] The motor subsystem includes a clutch, a generator motor and its drive controller. When pumping water for energy storage, the generator motor operates in motor mode and is controlled by the drive controller to run at variable speed. When releasing energy for power generation, the generator motor operates in generator mode and together with the drive controller, they form a variable speed constant frequency power generation system.

[0015] The operation of a pumped compressed gas energy storage system includes two processes: pumped compressed gas energy storage and gas expansion energy release for power generation. During energy storage, the generator motor of the motor subsystem drives the pumping subsystem to pump water from the storage tank through the pumping subsystem and the main pipeline into the pressure vessel subsystem. The gas in the pressure vessel subsystem is compressed, its volume decreases, and its pressure increases, completing the energy storage process. During energy release, the water in the pressure vessel subsystem is driven by the high-pressure gas in the pressure vessel subsystem to enter the turbine through the main pipeline and the power generation pipeline. The turbine drives the generator motor of the motor subsystem to generate electricity. After the water flows out of the turbine, it enters the storage tank. The gas in the pressure vessel subsystem expands and does work, completing the energy release process.

[0016] Furthermore, the series-parallel switching valve in the pumping subsystem includes a valve base, a series inlet, a series outlet, a parallel inlet, a parallel outlet, and a rotating body for switching between series and parallel channels, wherein the rotating body is provided with a series channel, a parallel inlet channel, a parallel outlet channel, and a driving mechanism.

[0017] The drive mechanism in the rotating body controls the rotation of the rotating body, thereby switching between series channels, parallel inlet channels, or parallel outlet channels to connect to the water pump unit;

[0018] When the pump units connected at both ends of the series-parallel switching valve are connected in series, the series inlet, series channel, and series outlet form a series path, while the parallel inlet and parallel outlet are closed.

[0019] When the pump units connected at both ends of the series-parallel switching valve are connected in parallel, the series inlet, the parallel outlet channel, and the parallel outlet form a passage, and the parallel inlet, the parallel inlet channel, and the series outlet form a passage, while the series channel is closed.

[0020] Furthermore, multiple pump units in the pumping subsystem are arranged coaxially, and two pump units are connected by a series-parallel switching valve;

[0021] The inlet of the first pump unit is connected to the water storage tank, the outlet of the first pump unit is connected to the series inlet of the first series-parallel switching valve, the series outlet of the first series-parallel switching valve is connected to the inlet of the next pump unit, the parallel inlet of the first series-parallel switching valve is connected to the water storage tank, the parallel outlet of the first series-parallel switching valve is connected to the pump water pipeline, and so on, until the outlet of the last pump unit is connected to the pump water pipeline.

[0022] The pump water pipeline connects the parallel outlets of all series and parallel switching valves and the outlet of the last pump unit into the main pipeline. The pressure vessel subsystem side of the main pipeline has branch pipelines, and each branch pipeline is connected to a pressure vessel unit of the pressure vessel subsystem through a valve.

[0023] The series-parallel switching valve can achieve series or parallel connection between two pump units, or series, parallel, or mixed series-parallel connection between multiple pump units by adjusting the series channel, parallel inlet channel, and parallel outlet channel. The total flow rate is maximized when all pump units are connected in parallel, and the total head is maximized when all are connected in series. When the series-parallel connection is mixed, the total head of the pump units connected in series in each parallel branch must be consistent, and the head and flow rate are adjusted according to the number of pump units connected in series and the number of parallel branches.

[0024] Furthermore, in the pressure vessel subsystem, when multiple pressure vessel units are nested sequentially from the inside out, the pressure of the innermost vessel is the highest, and the pressure of the pressure vessel units decreases sequentially from the inside out.

[0025] When multiple pressure vessel units are stacked, adjacent pressure vessels become a single unit by sharing a vessel wall;

[0026] When multiple pressure vessels are both stacked and nested, the characteristics are the same as described above;

[0027] Each pressure vessel unit in the pressure vessel subsystem is connected to the main pipeline via its own inlet and outlet water pipes. When pumping water for energy storage, the main pipeline connects to the pumping subsystem. When generating electricity, the main pipeline connects to the turbine via the power generation pipeline.

[0028] Furthermore, the generator motor is a permanent magnet synchronous generator motor or a doubly-fed asynchronous generator motor.

[0029] Furthermore, the drive controller is a four-quadrant converter, enabling bidirectional power transmission.

[0030] Furthermore, the pump unit is a single-stage or multi-stage pump.

[0031] Furthermore, in the pumping subsystem, multiple pump units and multiple series-parallel switching valves are configured independently, or multiple pump units and multiple series-parallel switching valves are integrated into one unit.

[0032] The method for retrofitting conventional hydropower stations with pumped compressed gas energy storage systems includes the following steps:

[0033] C1: The existing basic facilities of a conventional hydropower station include a top reservoir, water conveyance pipeline, turbine generator set, and tailrace reservoir; an additional pipeline is added to the water conveyance pipeline between the top reservoir and the turbine generator set, connecting to the pump unit and the inlet of the series-parallel switching valve of the pumping subsystem.

[0034] C2: The pumping subsystem is installed between the upper reservoir and the tailrace reservoir;

[0035] C3: The pressure vessel subsystem is located at a position higher than the surrounding area of ​​a conventional hydropower station to make full use of the water head;

[0036] C4: The turbine is located around the turbine generator set;

[0037] C5: The main pipeline connects the pumping subsystem's pumping pipeline to the pressure vessel subsystem, and connects to the turbine via the power generation pipeline;

[0038] C6: The water generated by the turbine flows into the tailrace pool.

[0039] Furthermore, during energy storage, the generator motor of the motor subsystem drives the pumping subsystem to pump water from the upper water tank through the water delivery pipeline, the pumping subsystem, and the main pipeline into the pressure vessel subsystem. The gas in the pressure vessel subsystem is compressed, the volume decreases and the pressure increases, thus completing the energy storage process.

[0040] During energy release, the water in the pressure vessel subsystem is driven by the high-pressure gas in the pressure vessel subsystem, and enters the turbine through the main pipeline and the power generation pipeline. The turbine drives the generator motor of the motor subsystem to generate electricity. After the water flows out of the turbine, it enters the tailrace pool. The gas in the pressure vessel subsystem expands and does work, completing the energy release process.

[0041] Compared to existing technologies, it has the following advantages and effects:

[0042] This invention is simple to operate, highly efficient, easy to implement and maintain. Conventional hydropower stations can be easily modified to achieve energy storage functions, making full use of existing equipment and reducing costs.

[0043] This invention can dynamically adjust the series and parallel structure of water pumps according to the pressure inside the pressure vessel, which can improve the utilization rate of water pumps, reduce the pressure difference between the inside and outside of the pressure vessel, improve the safety of the energy storage system, and reduce construction costs.

[0044] This invention makes full use of the existing facilities of conventional hydropower stations to realize the energy storage transformation of conventional hydropower stations.

[0045] As described above, the technical means of the present invention are simple and easy to implement, meet the requirements of peak shaving and valley filling in the power system, and improve the stability of the power system. Attached Figure Description

[0046] Figure 1 This is a structural diagram of a pumped compressed gas energy storage system according to Embodiment 1 of the present invention.

[0047] Figure 2 This is a structural diagram of a pumped compressed gas energy storage system according to Embodiment 2 of the present invention.

[0048] Figure 3 This is a structural diagram of a pumped compressed gas energy storage system according to Embodiment 3 of the present invention.

[0049] Figure 4This is a structural diagram of a pumped compressed gas energy storage system according to Embodiment 4 of the present invention.

[0050] Figure 5 This is a structural diagram of a pumped compressed gas energy storage system according to Embodiment 5 of the present invention.

[0051] Figure 6 This is a structural diagram of a pumped compressed gas energy storage system according to Embodiment 6 of the present invention.

[0052] Figure 7 This is a schematic diagram of the series-parallel switching valve switching to the series state in Embodiment 1 of the present invention.

[0053] Figure 8 This is a schematic diagram of the series-parallel switching valve switching to the parallel state in Embodiment 1 of the present invention.

[0054] Figure 9 This is a structural diagram of the modified pumped compressed gas energy storage system for a conventional hydropower station in Embodiment 7 of the present invention.

[0055] Figure 10 For the purposes of embodiment 8 of the present invention Figure 9 The diagram shows the structural adjustments made to the structure shown.

[0056] Figure 11 In Embodiment 9 of the present invention Figure 10 A schematic diagram showing further adjustments to the structure shown. Detailed Implementation

[0057] The inventive objective of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described in detail here, but the implementation of the present invention is not limited to the following embodiments.

[0058] Example 1:

[0059] A pumped compressed gas energy storage system, such as Figure 1 As shown, it includes a pumping subsystem 1, a pressure vessel subsystem 3, a water turbine 7, and an electric motor subsystem 15;

[0060] In this embodiment, the pumping subsystem 1 includes a first pump unit 11, a second pump unit 12, a third pump unit 13, a fourth pump unit 14, and multiple pump units, a first series-parallel switching valve 21, a second series-parallel switching valve 22, a third series-parallel switching valve 23, and multiple series-parallel switching valves. The pump units are driven by the motor subsystem 6. Adjacent pump units are connected through the series-parallel switching valves, and the series-parallel, parallel, or mixed series-parallel connections between multiple pump units are realized through the series-parallel switching valves 21, 22, and 23.

[0061] like Figure 1As shown, the first water pump unit 11, the second water pump unit 12, the third water pump unit 13, and the fourth water pump unit 14 are water pumps with the same parameters.

[0062] The pressure vessel subsystem 3 includes multiple pressure vessel units; each pressure vessel unit of the pressure vessel subsystem 3 is connected to the main pipeline 4 through its own inlet and outlet water pipes. When pumping water for energy storage, the main pipeline 4 connects to the pumping subsystem 3, and when generating electricity, the main pipeline 4 connects to the turbine 7 through the power generation pipeline 42.

[0063] like Figure 7 , Figure 8 As shown, the first series parallel switching valve 21 includes a valve base 215, a series inlet 211, a series outlet 212, a parallel inlet 213, a parallel outlet 214 fixed on the valve base 215, and a rotating body 2121 for switching the series and parallel channels; the rotating body 2121 is provided with a series channel 2124, a parallel inlet channel 2123, a parallel outlet channel 2122, and a drive mechanism 2125;

[0064] The drive mechanism 2125 in the rotating body 2121 controls the rotation of the rotating body 2121, thereby switching the series channel 2124, the parallel water inlet channel 2123 or the parallel water outlet channel 2122 to connect the first water pump unit 11 and the second water pump unit 12. Figure 7 The first series of parallel switching valves 21 are in a series state. Figure 8 The first series of parallel switching valves 21 are in a parallel state;

[0065] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown, when the first pump unit 11 and the second pump unit 12 connected at both ends of the first parallel switching valve 21 are connected in series, the series inlet 211, the series channel 2124 and the series outlet 212 form a series path, while the parallel inlet 213 and the parallel outlet 214 are closed.

[0066] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown, when the first pump unit 11 and the second pump unit 12 connected at both ends of the first series parallel switching valve 21 are connected in parallel, the series inlet 211, the parallel outlet channel 2122 and the parallel outlet 214 form a passage, the parallel inlet 213, the parallel inlet channel 2123 and the series outlet 212 form a passage, and the series channel 2124 is closed.

[0067] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown, four pump units 11, 12, 13, and 14 are arranged coaxially, and two pump units are connected by a series-parallel switching valve.

[0068] The inlet 113 of the first pump unit 11 is connected to the water storage tank 15. The outlet 114 of the first pump unit 11 is connected to the series inlet of the first series of parallel switching valves 21. The series outlet of the first series of parallel switching valves is connected to the inlet of the next pump unit. The inlet 123 of the second pump unit 12 is connected to the series outlet of the first series of parallel switching valves 21. The outlet 124 of the second pump unit 12 is connected to the series inlet of the second series of parallel switching valves 22. The inlet 133 of the third pump unit 13 is connected to the series outlet of the second series of parallel switching valves 22. The outlet 134 of the third pump unit 13 is connected to the series inlet of the third series of parallel switching valves 23. The inlet 143 of the fourth pump unit 14 is connected to the series outlet of the third series of parallel switching valves 23,... The outlet of the last pump unit is connected to the pump water pipe 41; the parallel inlet of the first series of parallel switching valves 21 is connected to the water storage tank 15, and the parallel outlet 214 of the first series of parallel switching valves 21 is connected to the pump water pipe 41; the parallel inlet of the second series of parallel switching valves 22 is connected to the water storage tank 15, and the parallel outlet of the second series of parallel switching valves 22 is connected to the pump water pipe 41; the parallel inlet of the third series of parallel switching valves 23 is connected to the water storage tank 15, and the parallel outlet of the third series of parallel switching valves 23 is connected to the pump water pipe 41; the parallel inlet of the last series of parallel switching valves is connected to the water storage tank 15, and the parallel outlet of the last series of parallel switching valves is connected to the pump water pipe 41; the parallel outlets of all series of parallel switching valves 21, 22, and 23, and the outlet of the last pump unit are all connected to the pump water pipe 41;

[0069] The pump water pipeline 41 connects the parallel outlets of all series and parallel switching valves 21, 22, and 23, as well as the outlet of the last pump unit, and then connects to the main pipeline 4. The main pipeline 4 is connected to each pressure vessel unit through valves to deliver water into different pressure vessels.

[0070] The series-parallel switching valve achieves series or parallel connection between two adjacent pump units, as well as series, parallel, or mixed series-parallel connection between multiple pump units by adjusting the position of the rotating body. The total flow rate is maximized when all pump units are connected in parallel, and the total head is maximized when all are connected in series. When the series-parallel connection is mixed, the total head of the pump units connected in series in each parallel branch must be consistent, and the head and flow rate are adjusted according to the number of pump units connected in series and the number of parallel branches.

[0071] This embodiment uses four water pump units as an example, such as Figure 1 The diagram shows that the first water pump unit 11, the second water pump unit 12, the third water pump unit 13, and the fourth water pump unit 14 are all connected in series, and the series-parallel structure can be dynamically adjusted.

[0072] like Figure 1 As shown, in this embodiment, the pressure vessel subsystem 3 consists of a first pressure vessel 3111, a second pressure vessel 3112, a third pressure vessel 3121, a fourth pressure vessel 3122, a fifth pressure vessel 3123, a sixth pressure vessel 3131, and a seventh pressure vessel 3132 stacked in a regular hexagonal structure and nested inside the outermost pressure vessel 33.

[0073] Each pressure vessel unit in the pressure vessel subsystem 3 is connected to the main pipeline 4 through its respective inlet and outlet water pipes. When pumping water for energy storage, the main pipeline 4 is connected to the pumping subsystem 1. When generating electricity, the main pipeline 4 is connected to the turbine 7 via the power generation pipeline 42.

[0074] The motor subsystem 6 includes two clutches 91 and 92, a generator motor 61, and a drive controller 62. During pumping and energy storage, the generator motor 61 is connected to the clutch 91 between the generator motor 61 and the pump subsystem shaft 10, and the clutch 92 between the generator motor 61 and the turbine 7 is disengaged. The generator motor operates in motor mode, and the drive controller 62 controls the motor to run at variable speed. During energy release and power generation, the clutch 91 between the generator motor 61 and the pump subsystem shaft 10 is disengaged, and the clutch 92 between the generator motor 61 and the turbine 7 is connected. The generator motor 61 operates in generator mode and forms a variable speed constant frequency power generation system with the drive controller 62.

[0075] The generator motor is a permanent magnet synchronous generator motor or a doubly-fed asynchronous generator motor.

[0076] The drive controller 62 is a four-quadrant bidirectional converter.

[0077] Example 2:

[0078] In this embodiment, as Figure 2 As shown, the eighth pressure vessel 3411, the ninth pressure vessel 3412, the tenth pressure vessel 3421, the eleventh pressure vessel 3422, the twelfth pressure vessel 3423, the thirteenth pressure vessel 3431, and the fourteenth pressure vessel 3432 are respectively nested within the first pressure vessel 3111, the second pressure vessel 3112, the third pressure vessel 3121, the fourth pressure vessel 3122, the fifth pressure vessel 3123, the sixth pressure vessel 3131, and the seventh pressure vessel 3132, which are stacked as a single unit, and then nested within the outermost pressure vessel 33;

[0079] The first pump unit 11, the second pump unit 12, the third pump unit 13, and the fourth pump unit 14 are all connected in series, and the series-parallel structure can be dynamically adjusted.

[0080] Example 3:

[0081] In this embodiment, as Figure 3 As shown, the eighth pressure vessel 3411, the ninth pressure vessel 3412, the tenth pressure vessel 3421, the eleventh pressure vessel 3422, the twelfth pressure vessel 3423, the thirteenth pressure vessel 3431, and the fourteenth pressure vessel 3432 are respectively nested within the first pressure vessel 3111, the second pressure vessel 3112, the third pressure vessel 3121, the fourth pressure vessel 3122, the fifth pressure vessel 3123, the sixth pressure vessel 3131, and the seventh pressure vessel 3132, which are stacked as a single unit.

[0082] In this embodiment, the four pump units in the pumping subsystem 1 are connected in series and then in parallel. In this state, there are two parallel branches. In one parallel branch, the first pump unit 11 and the second pump unit 12 are connected in series, and in the other parallel branch, the third pump unit 13 and the fourth pump unit 14 are connected in series. The series-parallel structure can be dynamically adjusted.

[0083] Example 4:

[0084] In this embodiment, as Figure 4 As shown, the first pressure vessel 3111, the second pressure vessel 3112, the third pressure vessel 3121, the fourth pressure vessel 3122, the fifth pressure vessel 3123, the sixth pressure vessel 3131, and the seventh pressure vessel 3132 are stacked together in a regular hexagonal structure.

[0085] In this embodiment, as Figure 4 As shown, half of the pump units 13 and 14 are installed in reverse order, so that the water flow direction in half of the pump units 11 and 12 is opposite to the water flow direction in the other half of the pump units 13 and 14. This is to reduce the axial stress of the pump units, but does not affect the series, parallel, or series-parallel connection adjustment between the pump units 11, 12, 13, and 14. Figure 4 The diagram shows the first pump unit 11 and the second pump unit 12 connected in series, the third pump unit 13 and the fourth pump unit 14 connected in series, and the two sets connected in series and then in parallel. The series-parallel structure can be dynamically adjusted.

[0086] Example 5:

[0087] In this embodiment, as Figure 5As shown, the pressure vessel subsystem 3 consists of a first pressure vessel 3111, a second pressure vessel 3112, a third pressure vessel 3113, a fourth pressure vessel 3121, a fifth pressure vessel 3122, a sixth pressure vessel 3123, a seventh pressure vessel 3131, an eighth pressure vessel 3132, a ninth pressure vessel 3133, ... stacked together in a quadrilateral structure and nested within the outermost pressure vessel 33.

[0088] In the pumping subsystem 1, the four pump units are connected in series and then in parallel. In this state, there are two parallel branches. In one parallel branch, the first pump unit 11 and the second pump unit 12 are connected in series, and in the other parallel branch, the third pump unit 13 and the fourth pump unit 14 are connected in series. The series-parallel structure can be dynamically adjusted.

[0089] Example 6:

[0090] In this embodiment, as Figure 6 As shown, the pressure vessel subsystem 3 consists of a first pressure vessel 351, a second pressure vessel 352, a third pressure vessel 353, a fourth pressure vessel 354, ... nested together in a circular cross-section.

[0091] In pumping subsystem 1, all four pump units are connected in parallel, and the series-parallel structure can be dynamically adjusted.

[0092] Example 7:

[0093] In this embodiment, as Figure 9 As shown, a conventional hydropower station is retrofitted with pumped compressed gas energy storage. The retrofit utilizes the existing basic facilities, including the upper reservoir 101, water conveyance pipeline 102, turbine generator set 103, and tailrace reservoir 104. After the retrofit, the upper reservoir 101, water conveyance pipeline 102, pumping subsystem 1, main pipeline 4, pressure vessel subsystem 3, power generation pipeline 42, turbine 7, generator subsystem 6, tailrace reservoir 104, and water storage tank 15 constitute a pumped compressed gas energy storage system. During energy storage, the generator motor of the motor subsystem 6 drives the pumping subsystem 1 to pump water from the upper reservoir 101 through the water supply pipeline 102, the pumping subsystem 1, and the main pipeline 4 into the pressure vessel subsystem 3. The gas inside the pressure vessel subsystem 3 is compressed, its volume decreases, and its pressure increases, completing the energy storage process. During energy release, the water inside the pressure vessel subsystem 3 is driven by the high-pressure gas inside the pressure vessel subsystem 3, passing through the main pipeline 4 and the generator pipeline 42 into the turbine 7. The turbine 7 drives the generator motor of the motor subsystem 6 to generate electricity. After flowing out of the turbine 7, the water enters the tailrace pool 104. The gas inside the pressure vessel subsystem 3 expands and performs work, completing the energy release process. The water storage pool 15 can serve as backup water, replacing the upper reservoir 101 or the tailrace pool 104.

[0094] Example 8:

[0095] In this embodiment, as Figure 10 As shown, the structure of Embodiment 7 is adjusted by changing the generator motor 61 of the motor subsystem 6 to a generator 612 and a motor 611, and removing the clutches 91, 92 and the water storage tank 15.

[0096] Example 9:

[0097] In this embodiment, as Figure 11 As shown, the structure of Embodiment 8 is further adjusted by changing the drive controller 81 of the motor subsystem 6 to a motor driver 811 and a generator controller 812.

[0098] As described above, the present invention can be implemented well.

[0099] The implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A pumped compressed gas energy storage system, characterized in that, It includes a pumping subsystem, a pressure vessel subsystem, a turbine, an electric motor subsystem, and a water storage tank; The pumping subsystem includes multiple series-parallel switching valves and multiple pump units coaxially mounted. The pump units are driven by the motor subsystem. Adjacent pump units are connected through series-parallel switching valves, and the series-parallel, parallel, or mixed series-parallel connections between the pump units are realized through the series-parallel switching valves. The pressure vessel subsystem includes multiple nested, stacked, and nested-stacked composite pressure vessel units. Each pressure vessel unit of the pressure vessel subsystem is connected to the main pipeline through its own inlet and outlet water pipes. When pumping water for energy storage, the main pipeline is connected to the pumping water pipes of the pumping subsystem. When generating electricity, the main pipeline is connected to the turbine through the power generation pipes. The motor subsystem includes a clutch, a generator motor and its drive controller. When pumping water for energy storage, the generator motor operates in motor mode and is controlled by the drive controller to run at variable speed. When releasing energy for power generation, the generator motor operates in generator mode and together with the drive controller, they form a variable speed constant frequency power generation system. The operation of a pumped compressed gas energy storage system includes two processes: pumped compressed gas energy storage and gas expansion energy release for power generation. During energy storage, the generator motor of the motor subsystem drives the pumping subsystem to pump water from the storage tank through the pumping subsystem and the main pipeline into the pressure vessel subsystem. The gas in the pressure vessel subsystem is compressed, its volume decreases, and its pressure increases, completing the energy storage process. During energy release, the water in the pressure vessel subsystem is driven by the high-pressure gas in the pressure vessel subsystem to enter the turbine through the main pipeline and the power generation pipeline. The turbine drives the generator motor of the motor subsystem to generate electricity. After the water flows out of the turbine, it enters the storage tank. The gas in the pressure vessel subsystem expands and does work, completing the energy release process. The series-parallel switching valve in the pumping subsystem includes a valve base, a series inlet, a series outlet, a parallel inlet, a parallel outlet, and a rotating body for switching between series and parallel channels, wherein the rotating body is provided with a series channel, a parallel inlet channel, a parallel outlet channel, and a driving mechanism. The drive mechanism in the rotating body controls the rotation of the rotating body, thereby switching between series channels, parallel inlet channels, or parallel outlet channels to connect to the water pump unit; When the pump units connected at both ends of the series-parallel switching valve are connected in series, the series inlet, series channel, and series outlet form a series path, while the parallel inlet and parallel outlet are closed. When the pump units connected at both ends of the series-parallel switching valve are connected in parallel, the series inlet, the parallel outlet channel and the parallel outlet form a passage, the parallel inlet, the parallel inlet channel and the series outlet form a passage, and the series channel is closed. Multiple pump units in the pumping subsystem are arranged coaxially, and two pump units are connected by a series-parallel switching valve. The inlet of the first pump unit is connected to the water storage tank, the outlet of the first pump unit is connected to the series inlet of the first series-parallel switching valve, the series outlet of the first series-parallel switching valve is connected to the inlet of the next pump unit, the parallel inlet of the first series-parallel switching valve is connected to the water storage tank, the parallel outlet of the first series-parallel switching valve is connected to the pump water pipeline, and so on, until the outlet of the last pump unit is connected to the pump water pipeline. The pump water pipeline connects the parallel outlets of all series and parallel switching valves and the outlet of the last pump unit into the main pipeline. The pressure vessel subsystem side of the main pipeline has branch pipelines, and each branch pipeline is connected to a pressure vessel unit of the pressure vessel subsystem through a valve. The series-parallel switching valve can achieve series or parallel connection between two pump units, or series, parallel connection or mixed series-parallel connection between multiple pump units by adjusting the series channel, parallel inlet channel and parallel outlet channel. The total flow rate is maximized when all pump units are connected in parallel, and the total head is maximized when all are connected in series. When the series-parallel connection is mixed, the total head of the pump units connected in series in each parallel branch must be consistent, and the head and flow rate are adjusted according to the number of pump units connected in series and the number of parallel branches. In a pressure vessel subsystem, when multiple pressure vessel units are nested sequentially from the inside out, the pressure of the innermost vessel is the highest, and the pressure of the pressure vessel units decreases sequentially from the inside out. When multiple pressure vessel units are stacked, adjacent pressure vessels become a single unit by sharing a vessel wall; When multiple pressure vessels are both stacked and nested, the characteristics are the same as described above; Each pressure vessel unit in the pressure vessel subsystem is connected to the main pipeline via its own inlet and outlet water pipes. When pumping water for energy storage, the main pipeline connects to the pumping subsystem. When generating electricity, the main pipeline connects to the turbine via the power generation pipeline.

2. The pumped compressed gas energy storage system according to claim 1, characterized in that, The generator motor is a permanent magnet synchronous generator motor or a doubly-fed asynchronous generator motor.

3. The pumped compressed gas energy storage system according to claim 1, characterized in that, The drive controller is a four-quadrant converter, enabling bidirectional power transmission.

4. The pumped compressed gas energy storage system according to claim 1, characterized in that, The pump unit can be a single-stage or multi-stage pump.

5. The pumped compressed gas energy storage system according to claim 1, characterized in that, In the pumping subsystem, multiple pump units and multiple series-parallel switching valves are configured independently, or multiple pump units and multiple series-parallel switching valves are integrated into one unit.

6. A method for retrofitting a conventional hydropower station using any one of the pumped compressed gas energy storage systems described in claims 1-5, characterized in that, Includes the following steps: C1: The existing basic facilities of a conventional hydropower station include a top reservoir, water conveyance pipeline, turbine generator set, and tailrace reservoir; an additional pipeline is added to the water conveyance pipeline between the top reservoir and the turbine generator set, connecting to the pump unit and the inlet of the series-parallel switching valve of the pumping subsystem. C2: The pumping subsystem is installed between the upper reservoir and the tailrace reservoir; C3: The pressure vessel subsystem is located at a position higher than the surrounding area of ​​a conventional hydropower station to make full use of the water head; C4: The turbine is located around the turbine generator set; C5: The main pipeline connects the pumping subsystem's pumping pipeline to the pressure vessel subsystem, and connects to the turbine via the power generation pipeline; C6: The water generated by the turbine flows into the tailrace pool.

7. The method for retrofitting a conventional hydropower station according to claim 6, characterized in that, During energy storage, the generator motor of the motor subsystem drives the pumping subsystem to pump water from the upper water tank through the water delivery pipeline, the pumping subsystem, and the main pipeline into the pressure vessel subsystem. The gas in the pressure vessel subsystem is compressed, the volume decreases and the pressure increases, thus completing the energy storage process. During energy release, the water in the pressure vessel subsystem is driven by the high-pressure gas in the pressure vessel subsystem, and enters the turbine through the main pipeline and the power generation pipeline. The turbine drives the generator motor of the motor subsystem to generate electricity. After the water flows out of the turbine, it enters the tailrace pool. The gas in the pressure vessel subsystem expands and does work, completing the energy release process.

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