Hydraulic pressure conversion pumping and gas compression combined energy storage system

Abstract

The application provides a hydraulic pressure variable pressure pumping and air compression combined energy storage system. The system comprises a variable speed pumping energy storage subsystem, a hydraulic pressure variable pressure subsystem and a near isothermal compression and expansion subsystem. The variable speed pumping energy storage subsystem comprises a variable speed pumping energy storage unit, two accumulators and a direction changing valve. The hydraulic pressure variable pressure subsystem comprises four hydraulic cylinders and two piston rods. The near isothermal compression and expansion subsystem comprises a water and air coexistence tank, a compressor, a circulating water pump, a spraying device and a pressure sensor. The system realizes near constant pressure transmission of hydraulic potential energy, near rated working condition operation of the variable speed pumping energy storage unit and near isothermal compression and expansion of air, and has high energy conversion efficiency after being enlarged.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new energy storage technology, and particularly relates to a hydraulic pressure variable pressure pumping and air compression combined energy storage system. BACKGROUND

[0002] With the increasing scale of intermittent wind and light energy grid-connected installation, energy storage technology plays an increasingly key role in the power grid, among which pumped storage and compressed air energy storage are widely used. However, the traditional pumped storage has defects of harsh site selection conditions and low energy storage density; the compressed air energy storage has the shortcomings of site selection limited to caves and low operating efficiency of compressors and turbines. Under the background of increasing capacity of wind and light energy grid-connected installation and increasingly fierce energy technology competition in the world, an efficient, compact, durable and environmentally friendly energy storage and power generation system is urgently needed.

[0003] In recent years, some studies have combined hydraulic machinery with compressed air energy storage technology to solve the problem of low operating efficiency of compressors and turbines, and improve the energy storage efficiency, but in the compression and expansion process, the gas pressure changes greatly. The operating efficiency and stability of hydraulic machinery under large water head amplitude are poor, and extreme conditions such as cavitation easily occur under high gas content, which threatens the operating safety. SUMMARY

[0004] In view of the deficiencies of the existing hydraulic compressed air energy storage technology, the application provides a hydraulic pressure variable pumping and air compression combined energy storage system. Firstly, the hydraulic pressure variable technology is introduced to transfer hydraulic potential energy at near constant pressure; secondly, the variable speed pumped storage technology is introduced to improve the variable head operating capacity of the system and realize efficient, safe and stable operation of the energy storage and power generation process.

[0005] The technical scheme adopted by the application is as follows: a hydraulic pressure variable pumping and air compression combined energy storage system, comprising a variable speed pumped storage subsystem, a hydraulic pressure variable subsystem and a near isothermal compression and expansion subsystem;

[0006] The variable speed pumped storage subsystem comprises a variable speed pumped storage unit, accumulators 1 and 2 and a reversing valve; the upstream and downstream side pipes of the variable speed pumped storage unit are connected with the reversing valve, and the pipes are respectively connected with the accumulators 1 and 2; during energy storage, the variable speed pumped storage unit repeatedly pumps liquid in the hydraulic cylinders 1 / 2, and pushes the piston in the hydraulic cylinder 2 / 1 to go up and do work after being pressurized; during power generation, the piston in the hydraulic cylinder 1 / 2 goes down, and the water in the cylinder is discharged to the variable speed pumped storage unit to do work and generate power;

[0007] The hydraulic pressure conversion subsystem comprises four hydraulic cylinders 1-4 which are identical in pairs and piston rods 1, 2, the hydraulic cylinders 1, 2 are completely identical, the hydraulic cylinders 3, 4 are completely identical, the piston areas in the hydraulic cylinders 1, 2 and the hydraulic cylinders 3, 4 are different, the low hydraulic potential energy in the hydraulic cylinders 1, 2 and the high hydraulic potential energy in the hydraulic cylinders 3, 4 can be converted, the purpose of near constant pressure transmission of hydraulic potential energy is achieved; during energy storage, the large flow and low hydraulic potential energy water flow provided by the variable speed pumped storage unit is pressurized by the hydraulic cylinders and converted into small flow and high hydraulic potential energy water flow which enters the water-air coexistence tank for energy storage; during power generation, the small flow and high hydraulic potential energy water flow provided by the water-air coexistence tank to the hydraulic cylinders 3 / 4 is converted into large flow and low hydraulic potential energy water flow in the hydraulic cylinders 1 / 2.

[0008] The near isothermal compression and expansion subsystem comprises a water-air coexistence tank, a compressor, a circulating water pump, a spraying device and a pressure sensor; during energy storage, the water in the hydraulic cylinders 3 / 4 is squeezed into the water-air coexistence tank to compress the air to do work under the action of the pistons in the hydraulic cylinders 1 / 2; during power generation, the air in the tank expands, the lower water is discharged into the hydraulic cylinders 3 / 4 to push the pistons to go down, the pistons in the hydraulic cylinders 1 / 2 are driven by the piston rods 1 / 2 to go down to push the water flow to do work to generate electricity.

[0009] As a preferred, the pumped storage and power generation equipment of the system is selected as a variable speed pumped storage unit which is connected with a reversing valve, by changing the connection mode of the pipeline, the continuous and efficient operation of the variable speed pumped storage unit for pumping and power generation can be realized.

[0010] As a preferred, the upstream side and the downstream side of the variable speed pumped storage unit are respectively connected with accumulators 1, 2, so as to suppress the water hammer pressure in the pipeline during the change of water flow direction and improve the operation safety of the variable speed pumped storage unit.

[0011] As a preferred, a pressure sensor is installed in the water-air coexistence tank, the pressure signal is transmitted to the speed regulation system of the variable speed pumped storage unit, the pumping or power generation power of the variable speed pumped storage unit can be adjusted in real time according to the pressure in the water-air coexistence tank.

[0012] As a preferred, the piston rods 1, 2 are of the same length, the maximum strokes of the hydraulic cylinders 1-4 are equal, the pistons in the hydraulic cylinders 1, 3 are synchronously operated and can reach the maximum and minimum strokes at the same time, the pistons in the hydraulic cylinders 2, 4 are synchronously operated and can reach the maximum and minimum strokes at the same time, when the hydraulic cylinders 1, 3 are located at the maximum / minimum strokes, the hydraulic cylinders 2, 4 are located at the minimum / maximum strokes.

[0013] The operation method of the hydraulic pressure conversion pumped and pressurized mixed energy storage system provided by the application comprises the following steps:

[0014] Step 1: Before the first operation of the system, the pressure presetting process of the energy storage system should be carried out, the compressed air with a preset pressure p1 in the water-air coexistence tank is provided by the compressor.

[0015] Step 2: During energy storage, the variable-speed pumped storage unit extracts the water in hydraulic cylinder 1 / 2 to hydraulic cylinder 2 / 1, then lifts the piston in hydraulic cylinder 2 / 1 upward, drives the piston in hydraulic cylinder 4 / 3 to run upward, and discharges the water in hydraulic cylinder 4 / 3 to the water-air coexistence tank to compress the air to do work; when the piston stroke in hydraulic cylinder 2 / 1 reaches the maximum value, the water flow direction is changed through the reversing valve; the cycle is repeated until the gas pressure in the water-air coexistence tank reaches the set value p2.

[0016] Step 3: During power generation, the compressed air expands, the lower water in the water-air coexistence tank is extruded to hydraulic cylinder 3 / 4, the piston in hydraulic cylinder 3 / 4 is driven to move downward, the water in hydraulic cylinder 1 / 2 flows through the variable-speed pumped storage unit to do work and generate electricity, the water after work returns to hydraulic cylinder 2 / 1, the piston in hydraulic cylinder 2 / 1 is lifted upward, and the water in hydraulic cylinder 4 / 3 is discharged to the low-pressure water tank; when the piston stroke in hydraulic cylinder 3 / 4 reaches the minimum value, the water flow direction is changed, and the power generation continues; the cycle is repeated until the air pressure in the water-air coexistence tank decreases to the set value p1.

[0017] The present application has the following beneficial effects:

[0018] 1) The system of the present application realizes the nearly constant pressure hydraulic potential energy transmission of pressure increasing during water pumping and pressure decreasing during power generation through four hydraulic cylinders, and improves the energy storage density of the system;

[0019] 2) The system of the present application adopts a variable-speed pumped storage unit, which has high water pumping and power generation efficiency, and can operate efficiently, stably and safely within a large water head variation range, thereby improving the system operation efficiency and stability;

[0020] 3) The system of the present application separates the water participating in compressed air from the water in the lower hydraulic cylinders 1 and 2, so that the gas dissolution amount in the water used for water pumping and power generation by the variable-speed pumped storage unit is very small, and the unit is less affected by cavitation, and is more safe;

[0021] 4) The system of the present application adopts two accumulators, which can effectively reduce the water hammer pressure in the pressure pipeline and ensure the operation safety of the unit;

[0022] 5) The system of the present application can improve the energy performance of the system by increasing the energy storage capacity, the terminal pressure and the capacity of the variable-speed pumped storage unit, and the energy storage efficiency of the system after being upsized can reach more than 70%. BRIEF DESCRIPTION OF DRAWINGS

[0023] The present application can be best understood with reference to the following description taken in conjunction with the accompanying drawings. In the drawings, like parts can be indicated by like reference numbers.

[0024] Figure 1A structural schematic diagram of a hydraulic variable pressure pumped water and compressed gas hybrid energy storage system;

[0025] Figure 2 A flow chart of an energy storage operation process of a hydraulic variable pressure pumped water and compressed gas hybrid energy storage system;

[0026] Figure 3 A flow chart of a power generation operation process of a hydraulic variable pressure pumped water and compressed gas hybrid energy storage system. DETAILED DESCRIPTION

[0027] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions will be further described below in conjunction with the accompanying drawings of the embodiments of the present application. It should be understood that the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The embodiments described below by referring to the accompanying drawings are only used to explain the present application, rather than to limit the applicable scope of the present application. Based on the embodiments of the present application, any skilled person in the art can obtain other transformations or replacements without making any creative efforts, which are within the protection scope of the present application.

[0028] The present application will be further described below in conjunction with the accompanying drawings.

[0029] Figure 1 A structural schematic diagram of a hydraulic variable pressure pumped water and compressed gas hybrid energy storage system according to a first embodiment of the present application. The system comprises a variable speed pumped water storage unit, accumulators 1 and 2, hydraulic cylinders 1-4, a water-gas co-containment tank, a circulating water pump, pressure sensors, a compressor, a low pressure water pool, valves F1-F8 and a reversing valve.

[0030] Specifically, the present application provides a hydraulic variable pressure pumped water and compressed gas hybrid energy storage system, wherein a left large hydraulic cylinder filled with water is referred to as hydraulic cylinder 1, a right large hydraulic cylinder filled with a small amount of water is referred to as hydraulic cylinder 2, a left small hydraulic cylinder filled with a small amount of water is referred to as hydraulic cylinder 3, and a right small hydraulic cylinder filled with water is referred to as hydraulic cylinder 4; the variable speed pumped water storage unit is connected to the reversing valve through a pressure pipeline, and accumulators 1 and 2 are connected to the upstream and downstream pipelines, respectively; the other end of the reversing valve is connected to the hydraulic cylinders 1 and 2 through a pressure pipeline; the low pressure water pool, the hydraulic cylinders 3 and 4 and the water-gas co-containment tank are also connected through a pressure pipeline; the water-gas co-containment tank is connected to the circulating water pump through a pipeline; and the strokes of the hydraulic cylinders 1-4 are in the upward direction as the positive direction.

[0031] The present embodiment provides a new type of hydraulic variable pressure pumped water and compressed gas hybrid energy storage system, which comprises a variable speed pumped water storage subsystem, a hydraulic variable pressure subsystem and a near-isothermal compression and expansion subsystem.

[0032] As Figure 1As shown, the variable-speed pumped storage subsystem includes a variable-speed pumped storage unit, accumulators 1 and 2, and a reversing valve. The upstream side of the variable-speed pumped storage unit is connected to accumulator 1 via a pressure pipeline, and then to the reversing valve. The downstream side is connected to accumulator 2 via a pressure pipeline, and then to the reversing valve. Accumulators 1 and 2 are filled with pressurized gas at a pressure equal to the rated head of the variable-speed pumped storage unit. During energy storage, the variable-speed pumped storage unit pumps liquid back and forth from hydraulic cylinder 1 / 2, pressurizes it, and pushes the piston in hydraulic cylinder 2 / 1 upward to do work. During power generation, the piston in hydraulic cylinder 1 / 2 moves downward, squeezing the water in the cylinder to the variable-speed pumped storage unit to do work and generate electricity.

[0033] like Figure 1 As shown, the hydraulic transformer subsystem includes four identical hydraulic cylinders 1-4. Hydraulic cylinders 1 and 2 are completely identical, and hydraulic cylinders 3 and 4 are completely identical. The piston areas inside hydraulic cylinders 1 and 2 are different from those inside hydraulic cylinders 3 and 4, and their area ratio is the reciprocal of the transformer ratio. This allows for the back-and-forth conversion between the low hydraulic potential energy in hydraulic cylinders 1 and 2 and the high hydraulic potential energy in hydraulic cylinders 3 and 4, achieving the purpose of transmitting hydraulic potential energy at near constant pressure. During energy storage, the large flow rate and low potential energy water provided by the variable speed pumped storage unit are pressurized by the hydraulic cylinders and converted into a small flow rate and high hydraulic potential energy water flow before entering the water-air co-containment tank for energy storage. During power generation, the small flow rate and high hydraulic potential energy water flow provided by the water-air co-containment tank to hydraulic cylinders 3 and 4 are converted into a large flow rate and low hydraulic potential energy water flow in hydraulic cylinder 1 and 2. This realizes the function of back-and-forth conversion between the large pressure amplitude in the water-air co-containment tank and the small head amplitude at the variable speed pumped storage unit.

[0034] like Figure 1 As shown, the near-isothermal compression-expansion subsystem includes a water-air co-containment tank, a compressor, a circulating water pump, a spray device, and a pressure sensor. The water-air co-containment tank contains the spray device and the pressure sensor. The spray device is used for heat exchange during air compression and expansion, achieving near-isothermal operation during the air compression and expansion process. The pressure sensor is used to transmit the air pressure value inside the tank to the variable-speed pumped-storage unit in real time, enabling real-time and precise control of the unit. During energy storage, under the action of the piston in hydraulic cylinder 1 / 2, water in hydraulic cylinder 3 / 4 is forced into the water-air co-containment tank to compress air and perform work. During power generation, the air inside the tank expands, and the lower water is discharged into hydraulic cylinder 3 / 4, pushing the piston downward. This, through piston rod 1 / 2, drives the piston inside hydraulic cylinder 1 / 2 downward, propelling the water flow to perform work and generate electricity.

[0035] The operation method of the above-mentioned hydraulic variable pressure pumped water and compressed air hybrid energy storage system includes the following steps:

[0036] Step 1: Before the system is put into operation for the first time, this energy storage system should be pressure preset. Open valves F3 and F6 and pressurize the water-air co-containment tank with air through the compressor. Stop when the pressure in the tank reaches p1. During the pressure preset, the circulating water pump will work continuously to draw water from the bottom of the tank to the top for spray cooling.

[0037] Step 2: As Figure 2 As shown, during energy storage, valves F1, F3, F4, and F7 are first opened. The variable-speed pumped storage unit draws water from hydraulic cylinder 1 into hydraulic cylinder 2, pushing the piston in hydraulic cylinder 2 upwards, which in turn drives the piston in hydraulic cylinder 4 upwards, discharging the water in hydraulic cylinder 4 into the water-air co-containment tank to compress air and perform work. When the stroke of hydraulic cylinder 2 reaches its maximum value L... max At this time, the pumping direction is changed by the reversing valve; valves F2, F3, F5, and F8 are opened, and other valves are closed. The variable speed pumped storage unit draws water from hydraulic cylinder 2 into hydraulic cylinder 1, which then pushes the piston in hydraulic cylinder 1 upward, driving the piston in hydraulic cylinder 3 upward, discharging the water in hydraulic cylinder 3 into the water-air co-containment tank to compress air for work; when the stroke of hydraulic cylinder 1 reaches its maximum value L... max During this process, the pumping direction is changed via a reversing valve; this cycle repeats until the gas pressure inside the water-gas co-containment tank increases to the set value p2. During energy storage, the circulating water pump operates continuously, drawing water from the bottom of the tank to the top for spray cooling.

[0038] Step 3: As Figure 3 As shown, during power generation, valves F2, F3, F5, and F7 are first opened, compressing air expands, forcing the water in the lower part of the water-air co-containment tank into hydraulic cylinder 3, pushing its internal piston downwards. This causes the water in hydraulic cylinder 1 to flow through the variable-speed pumped storage unit to generate electricity. The water after generating electricity returns to hydraulic cylinder 2, pushing its internal piston upwards; this drives the internal piston of hydraulic cylinder 4 upwards, discharging the water in the cylinder into the low-pressure water tank. When the stroke of hydraulic cylinder 3 reaches its minimum value L... min At this time, the water flow direction is changed by the reversing valve; valves F1, F3, F4, and F8 are opened, and other valves are closed. Compressed air expands, squeezing the water in the lower part of the water-air co-containment tank into hydraulic cylinder 4, pushing its inner piston downward. This causes the water in hydraulic cylinder 2 to flow through the variable speed pumped storage unit to generate electricity. The water after generating electricity returns to hydraulic cylinder 1, pushing its inner piston upward, and discharging the water in hydraulic cylinder 3 into the low-pressure water tank. When the stroke of hydraulic cylinder 4 reaches its minimum value L... min At this time, the water flow direction is changed to continue generating electricity. This cycle is repeated until the air pressure inside the water-air coexistence tank drops to the set value p1. During power generation, the circulating water pump works continuously, drawing water from the bottom of the tank to the top spray for heating.

Claims

1. An operation method for a hydraulic variable pressure pumped water / compressed air hybrid energy storage system, characterized in that, The energy storage system includes a variable speed pumped hydro storage subsystem, a hydraulic transformer subsystem, and a near-isothermal compression-expansion subsystem; The variable-speed pumped storage subsystem includes a variable-speed pumped storage unit, accumulator one and accumulator two, and a reversing valve. The upstream and downstream pipelines of the variable-speed pumped storage unit are connected to the reversing valve, and accumulator one and accumulator two are connected to the pipelines respectively. During energy storage, the variable-speed pumped storage unit pumps liquid back and forth from hydraulic cylinder one or hydraulic cylinder two, pressurizes it, and pushes the piston in hydraulic cylinder two or / or hydraulic cylinder one upward to do work. During power generation, the piston in hydraulic cylinder one or hydraulic cylinder two moves downward, pushing the water in the cylinder to flow through the variable-speed pumped storage unit to generate power. The hydraulic transformer subsystem includes four identical hydraulic cylinders (cylinder 1, cylinder 2, cylinder 3, and cylinder 4) and piston rods (cylinder 1 and piston rod 2). Cylinders 1 and 2 are identical, as are cylinders 3 and 4. The piston areas in cylinders 1 and 2 differ from those in cylinders 3 and 4, allowing for the mutual conversion between the low hydraulic potential energy in cylinders 1 and 2 and the high hydraulic potential energy in cylinders 3 and 4, achieving near-constant pressure transmission of hydraulic potential energy. During energy storage, the high-flow, low-hydraulic-potential-energy water provided by the variable-speed pumped storage unit is pressurized by the hydraulic cylinders and converted into a low-flow, high-hydraulic-potential-energy water flow, which then enters the water-air co-containment tank for energy storage. During power generation, the low-flow, high-hydraulic-potential-energy water flow provided by the water-air co-containment tank to cylinders 3 or 4 is converted into a high-flow, low-hydraulic-potential-energy water flow in cylinder 1 or 2. The near-isothermal compression-expansion subsystem includes a water-air co-containment tank, a compressor, a circulating water pump, a spray device, and a pressure sensor. During energy storage, under the action of the piston in hydraulic cylinder one or hydraulic cylinder two, the water in hydraulic cylinder three or hydraulic cylinder four is squeezed into the water-air co-containment tank to compress air and do work. During power generation, the air in the tank expands, and the water in the lower part is discharged into hydraulic cylinder three or hydraulic cylinder four, pushing the piston downward. Through piston rod one or piston rod two, the piston in hydraulic cylinder one or hydraulic cylinder two is driven downward, driving the water flow to do work and generate electricity. The operation method of the energy storage system includes the following steps: Step 1: Before the system's initial operation, this energy storage system should undergo a pressure pre-setting process. The pressure in the water-gas co-containment tank should be pre-set by the compressor. p 1 unit of compressed air; Step 2: During energy storage, the variable-speed pumped storage unit draws water from hydraulic cylinder one or hydraulic cylinder two into hydraulic cylinder two or hydraulic cylinder one. Then, the piston in hydraulic cylinder two or hydraulic cylinder one is pushed upwards, causing the piston in hydraulic cylinder four or hydraulic cylinder three to move upwards, discharging the water in hydraulic cylinder four or hydraulic cylinder three into the water-air co-containment tank where compressed air performs work. When the piston stroke in hydraulic cylinder two or hydraulic cylinder one reaches its maximum value, the pumping direction is changed through a reversing valve. This cycle is repeated until the gas pressure in the water-air co-containment tank reaches the set value. p 2; Step 3: During power generation, compressed air expands, forcing the water in the lower part of the water-air coexisting tank into hydraulic cylinder three or four, pushing the piston inside downwards. This causes the water in hydraulic cylinder one or two to flow through the variable-speed pumped-storage unit to generate electricity. After generating electricity, the water returns to hydraulic cylinder two or one, pushing its piston upwards and discharging the water in hydraulic cylinder four or three into the low-pressure water tank. When the piston stroke in hydraulic cylinder three or four reaches its minimum value, the water flow direction is changed, and power generation continues. This cycle repeats until the air pressure in the water-air coexisting tank drops to the set value. p 1.

2. The operating method according to claim 1, characterized in that: The pumping and power generation equipment is a variable speed pumped storage unit, which is connected to a reversing valve to achieve continuous and efficient pumping and power generation.

3. The operating method according to claim 1, characterized in that: The upstream and downstream pipelines of the variable speed pumped storage unit are respectively connected to accumulator one and accumulator two to suppress the water hammer pressure in the pipeline when the water flow changes direction.

4. The operating method according to claim 1, characterized in that: A pressure sensor is installed inside the water-air co-containment tank, which transmits the pressure signal to the speed control system of the variable speed pumped storage unit, and adjusts the unit's output or power generation capacity accordingly.

5. The operating method according to claim 1, characterized in that: Piston rod one and piston rod two are of the same length. The maximum and minimum strokes of hydraulic cylinder one, hydraulic cylinder two, hydraulic cylinder three, and hydraulic cylinder four are equal. The pistons in hydraulic cylinder one and hydraulic cylinder three move synchronously and can reach the maximum / minimum stroke at the same time. The pistons in hydraulic cylinder two and hydraulic cylinder four move synchronously and can reach the maximum / minimum stroke at the same time. When hydraulic cylinder one and hydraulic cylinder three are at the maximum / minimum stroke, hydraulic cylinder two and hydraulic cylinder four are at the minimum / maximum stroke.

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