Compressed air energy storage system and operation method thereof

Abstract

The invention discloses a compressed air energy storage system and an operation method thereof, and relates to the technical field of compressed air energy storage. Wherein the energy storage unit comprises at least two storage tanks; the storage tank is vertically arranged, a piston dividing an inner cavity of the storage tank into an upper cavity and a lower cavity is arranged in the storage tank, an elastic air bag used for storing hydrogen or oxygen is arranged in the lower cavity, and a liquid medium is stored in the upper cavity. The energy release unit comprises at least two expansion units, the air inlet ends of the expansion units are correspondingly communicated with the corresponding storage tanks of the energy storage unit, the air outlet ends of the expansion units are communicated with a premixing tank, and the premixing tank is communicated with a hydrogen energy internal combustion engine unit; according to the invention, through a multi-stage compression and cooling technology, hydrogen and oxygen are respectively compressed to a high-pressure state of 35 MPa in an energy storage stage, and are stored in an elastic air bag. The multi-stage compression can effectively reduce the energy loss in the compression process and improve the compression efficiency. And meanwhile, the tube shell type cooler is used, so that the gas temperature can be rapidly reduced, excessive expansion of the gas due to too high temperature is prevented, and stable storage of the gas in a high-pressure state is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of compressed air energy storage, and in particular to a compressed air energy storage system and an operating method thereof. Background Art

[0002] With the acceleration of global energy transformation, renewable energy such as wind power and solar energy account for an increasing proportion of the energy structure. However, these renewable energy sources are intermittent and volatile, and their power generation is restricted by natural conditions. For example, wind power generation depends on wind speed, and unstable wind speed leads to large fluctuations in power generation; solar power generation is affected by day and night and weather, and cannot achieve all-weather continuous power supply. This has brought huge challenges to the stable operation of the power system. How to effectively balance the load of the power grid and improve the absorption capacity of renewable energy has become an urgent problem to be solved.

[0003] As a core means to solve the problem of renewable energy consumption, energy storage technology can store energy when there is an oversupply of electricity and release energy when there is a power shortage, effectively smoothing the fluctuations in renewable energy generation and improving the stability and reliability of the power system. Compressed air energy storage technology has become one of the large-scale energy storage technologies with great development potential due to its outstanding advantages such as large energy storage capacity, long energy storage cycle, relatively low cost, and environmental friendliness. Traditional compressed air energy storage technology has the problem of large system pressure fluctuations, which not only affects the stability of energy but also increases operating costs. The above defects are problems that need to be solved urgently by those skilled in the art. Summary of the invention

[0004] In order to overcome the deficiencies in the background technology, the present invention discloses a compressed air energy storage system and an operation method thereof, aiming to achieve effective storage and release of electric energy through reasonable structural design and operation process, so as to regulate the grid load and improve energy utilization efficiency.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] A compressed air energy storage system and an operation method thereof, comprising an energy storage unit and an energy release unit; wherein the energy storage unit comprises at least two storage tanks; the storage tanks are arranged vertically, and are provided with pistons which divide their inner cavities into upper and lower cavities, the lower cavity is provided with elastic air bags for storing hydrogen or oxygen, and the upper cavity stores liquid medium; the energy release unit comprises at least two expansion units, the air inlet ends of the expansion units are correspondingly connected to the corresponding storage tanks of the energy storage unit, the air outlet ends of the expansion units are connected to premixing tanks, and the premixing tanks are connected to hydrogen internal combustion units.

[0007] Preferably, it further comprises a compression unit, which comprises at least two compressor groups, and the gas outlet ends of the compressor groups are correspondingly connected to the corresponding storage tanks of the energy storage unit.

[0008] The operating method of the compressed air energy storage system comprises the following steps:

[0009] S1. When electricity consumption is low, the compressor unit of the compression unit compresses hydrogen and oxygen into the elastic air bags in the corresponding storage tanks respectively. The elastic air bags expand and push the piston and liquid medium upward, so that the pressure in the elastic air bags is not less than 30 MPa.

[0010] S2. During peak electricity consumption, the energy storage unit is connected to the energy release unit, and hydrogen and oxygen enter the corresponding expansion units through the one-way valves respectively. The expansion units drive the generator sets to generate electricity. The hydrogen and oxygen output from the expansion units enter the premixing tank for mixing, and the mixed gas is input into the hydrogen internal combustion engine set, which drives the generator set to generate electricity.

[0011] Preferably, in step S1, hydrogen and oxygen are compressed step by step through a primary compressor, a secondary compressor and a tertiary compressor respectively; the primary compressor compresses the gas to 1.2 MPa, and cools it to 40°C through a shell and tube cooler; the secondary compressor compresses the gas to 10.5 MPa, and cools it to 55°C through a shell and tube cooler; the tertiary compressor compresses the gas to 35 MPa, and cools it to 170°C through a shell and tube cooler; the medium after absorbing heat in the shell and tube cooler enters the insulation tank for storage.

[0012] Preferably, in step S2, the 30 MPa gas in the storage tank is heated to 300° C. by an electric heat accumulator before entering the expansion unit.

[0013] Preferably, in step S2, the expansion unit is preheated using the medium in the insulation tank.

[0014] Due to the adoption of the above-mentioned technical solution, the present invention has the following beneficial effects:

[0015] The present invention discloses a compressed air energy storage system and an operating method thereof. Through multi-stage compression and cooling technology, hydrogen and oxygen are respectively compressed to a high-pressure state of 35MPa in the energy storage stage and stored in elastic air bags. Multi-stage compression can effectively reduce energy loss in the compression process and improve compression efficiency. At the same time, the use of shell and tube coolers can quickly reduce the gas temperature, prevent excessive expansion of the gas due to excessive temperature, and ensure stable storage of the gas under high pressure. In the energy release stage, the gas expands step by step through the multi-stage expander to do work, driving the generator to generate electricity. The multi-stage expansion technology can make full use of the pressure energy and thermal energy of the gas to further improve the energy conversion efficiency.

[0016] The present invention further utilizes the medium stored in the heat preservation tank and absorbed heat by the shell and tube cooler in the energy storage stage to preheat the expansion unit during the energy release stage, effectively preventing the expansion unit from frosting due to the processing of low-temperature gas, thereby reducing energy consumption and extending the service life of the equipment. In addition, the elastic air bag and piston structure used in the present invention can automatically adjust the volume according to the change of gas pressure, effectively reducing the system pressure fluctuation, improving the overall efficiency of the energy storage system, and thus reducing the operating cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the system framework of the present invention;

[0018] Figure 2 It is a structural schematic diagram of the storage tank;

[0019] Figure 3 Schematic diagram of the structural frame of the expansion unit.

[0020] In the figure: 1. Energy storage unit; 1-1. Storage tank; 1-2. Piston; 1-3. Elastic air bag; 2. Energy release unit; 2-1. Expansion unit; 2-2. Premixing tank; 2-3. Hydrogen internal combustion engine unit; 3. Compression unit. DETAILED DESCRIPTION

[0021] The present invention can be explained in detail through the following embodiments. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention. In the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "front", "back", "left", "right", etc. indicating directions or positional relationships, they only correspond to the drawings of the present application for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific direction.

[0022] Embodiment 1, in combination with Figures 1 to 3 , a compressed air energy storage system and an operation method thereof, comprising an energy storage unit 1 and an energy release unit 2.

[0023] The energy storage unit 1 is the core part of the system and is used to store compressed gas energy. It includes at least two storage tanks 1-1, which are arranged vertically to make full use of space and ensure structural stability. A piston 1-2 is provided inside each storage tank 1-1 to separate the inner cavity of the storage tank into two independent cavities, upper and lower, to achieve layered storage of different media. An elastic air bag 1-3 is provided in the lower cavity to store hydrogen or oxygen. The elastic air bag 1-3 has good elasticity and pressure resistance, and can automatically adjust the volume according to changes in internal gas pressure to ensure the safety and reliability of gas storage. The upper cavity is used to store liquid media. The selection of liquid media needs to take into account its physical properties such as density and viscosity to ensure good coordination with the elastic air bag 1-3 and the piston 1-2 to achieve effective regulation and stabilization of gas pressure.

[0024] The energy release unit 2 is responsible for releasing the stored energy and converting it into electrical energy, and its main structure includes at least two groups of expansion units 2-1. The air inlet end of the expansion unit 2-1 is connected to the corresponding storage tank 1-1 of the energy storage unit 1 to ensure that the stored gas energy can be smoothly obtained during the energy release stage. The air outlet end of the expansion unit 2-1 is connected to the premixing tank 2-2, which is used to fully mix the gases from different sources to form a mixed gas suitable for combustion. The premixing tank 2-2 is further connected to the hydrogen internal combustion engine unit 2-3, which drives the generator set to generate electricity by burning the mixed gas, thereby realizing the final release and conversion of energy.

[0025] The compression unit 3 plays a key role in the energy storage stage, and its main structure includes at least two sets of compressor units. The gas outlet of the compressor unit is connected to the corresponding storage tank 1-1 of the energy storage unit 1. Through a multi-stage compression process, hydrogen and oxygen are compressed to a set pressure and then pressed into the elastic air bag 1-3 in the storage tank 1-1 to complete energy storage. The compressor unit adopts a multi-stage compression design, which can effectively improve compression efficiency and reduce energy consumption.

[0026] The working process of the compressed air energy storage system of this embodiment is divided into an energy storage stage and an energy release stage. The working principles of the two stages are as follows:

[0027] Energy storage stage:

[0028] During the off-peak period, the grid load is small, which is an ideal time to perform energy storage operations. The specific process is as follows:

[0029] The compressor unit of compression unit 3 starts working, and hydrogen and oxygen are introduced into the compressor unit respectively. The gas is first compressed by the first-stage compressor to increase the gas pressure to 1.2MPa. At this time, the gas temperature will increase due to the compression process, and then the gas enters the shell and tube cooler. Through the efficient heat exchange structure inside the shell and tube cooler, the gas temperature is quickly reduced to 40°C to ensure the stability of the subsequent compression process. The shell and tube cooler can achieve a large amount of heat exchange in a short time, effectively reduce the gas temperature, and improve the compression efficiency.

[0030] After the initial compression and cooling, the gas enters the secondary compressor, and is further compressed to a pressure of 10.5 MPa. Due to the temperature rise during the compression process, the gas then enters the shell and tube cooler for cooling. After this cooling, the gas temperature stabilizes at 55°C, ready for the third stage of compression. The use of the secondary compressor and the shell and tube cooler can further increase the gas pressure, while ensuring that the gas temperature is within a reasonable range, ensuring the efficient compression process.

[0031] The gas enters the three-stage compressor, which eventually compresses the gas pressure to 35MPa. The high-pressure gas enters the shell and tube cooler again, and after cooling, the gas temperature drops to 170°C. At this time, after the heat-absorbing medium in the shell and tube cooler completes its heat-absorbing task, it is introduced into the insulation tank for storage, so as to preheat the expansion unit 2-1 in the subsequent energy release stage and reduce energy consumption. The combination of the three-stage compressor and the shell and tube cooler can increase the gas pressure to a higher level to meet the energy storage needs. At the same time, the heat-absorbing medium is stored in the insulation tank, realizing the effective recovery and utilization of energy.

[0032] After multi-stage compression and cooling, the high-pressure hydrogen and oxygen are respectively pressed into the elastic air bags 1-3 in the corresponding storage tanks 1-1 in the energy storage unit 1. As the gas is continuously injected, the elastic air bags 1-3 gradually expand, thereby pushing the piston 1-2 and the liquid medium in the upper cavity upward. During this process, the pressure in the elastic air bags 1-3 is always maintained at a level not less than 30MPa, ensuring that the gas can be effectively stored, while laying the foundation for the smooth progress of the subsequent energy release stage.

[0033] Energy release stage:

[0034] When the peak load of the power grid comes and the power demand increases sharply, it quickly switches to the energy release mode to release the stored energy and convert it into electrical energy to relieve the power supply pressure of the power grid. The specific working process is as follows:

[0035] The energy storage unit 1 is connected to the energy release unit 2. The hydrogen and oxygen in the storage tank 1-1, which were originally in a high-pressure state of 30MPa, enter the corresponding expansion unit 2-1 through a one-way valve. Before entering the expansion unit 2-1, the gas is first heated by the electric heat accumulator to 300°C to improve the efficiency of gas expansion work. The electric heat accumulator can raise the gas temperature to the required level in a short time to ensure the efficient expansion process of the gas. The expansion unit 2-1 contains a high-pressure expander, a medium-pressure expander and a low-pressure expander connected in sequence. The high-temperature and high-pressure gas at 300°C first enters the high-pressure expander, expands and works inside the expander, drives the high-pressure expander to rotate, and then drives the generator connected to it to generate electricity. The gas pressure after expansion by the high-pressure expander drops to 15MPa, and then enters the medium-pressure expander to continue to expand and work, driving the medium-pressure expander to rotate and drive the generator to generate electricity. At this time, the gas pressure further drops to 5MPa. Finally, the 5MPa gas enters the low-pressure expander, expands again to do work, drives the low-pressure expander to rotate, drives the generator to generate electricity, and the gas pressure finally drops to 0.5MPa. The design of the expander unit 2-1 adopts multi-stage expansion technology, which can make full use of the pressure energy and thermal energy of the gas to achieve efficient energy conversion and power generation process.

[0036] The 0.5MPa hydrogen and oxygen output from the low-pressure expander enter the premixing tank 2-2 for mixing. A stirring shaft is provided inside the premixing tank 2-2 to ensure that the hydrogen and oxygen are fully and evenly mixed to form a mixed gas suitable for combustion. The mixed gas is input into the hydrogen internal combustion engine unit 2-3. Inside the hydrogen internal combustion engine unit 2-3, the combustion of the mixed gas releases a large amount of heat energy, which drives the piston movement of the internal combustion engine unit, and then drives the generator set connected to it to generate electricity, further increasing the power output to meet the peak load requirements of the power grid.

[0037] It should be noted that in the energy release stage, hydrogen and oxygen enter different expansion units 2-1 respectively, and are finally mixed in the premixing tank 2-2. This design can ensure that the gas maintains a high purity during the expansion process and improve safety performance. At the same time, in order to further reduce energy consumption and ensure the normal operation of the expansion unit 2-1, during the operation of the expansion unit 2-1, the expansion unit 2-1 is preheated using the medium stored in the insulation tank after absorbing heat in the shell and tube cooler during the energy storage stage. In this way, the expansion unit 2-1 is effectively prevented from frosting and other adverse phenomena due to the processing of low-temperature gas, the service life of the equipment is extended, the stability and efficiency of the entire energy release process are ensured, and the energy consumption of the system is reduced.

[0038] Through the close coordination and efficient operation of the above-mentioned energy storage stage and energy release stage, this compressed air energy storage system can realize the effective storage and release of electric energy, flexibly adjust the grid load, improve the energy utilization efficiency, and has broad application prospects.

[0039] The parts of the present invention that are not described in detail are prior art. It is obvious to those skilled in the art that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention; therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and it is intended that all changes that fall within the meaning and scope of equivalent elements are included in the present invention.

Claims

1. A compressed air energy storage system, characterized in that: The invention comprises an energy storage unit (1) and an energy release unit (2); wherein the energy storage unit (1) comprises at least two storage tanks (1-1); the storage tanks (1-1) are arranged vertically, and a piston (1-2) is provided in the storage tanks (1-1) for dividing the inner cavity thereof into two upper and lower cavities; an elastic air bag (1-3) for storing hydrogen or oxygen is provided in the lower cavity; and a liquid medium is stored in the upper cavity; and the energy release unit (2) comprises at least two expansion units (2-1); the air inlet end of the expansion unit (2-1) is correspondingly connected to the corresponding storage tank (1-1) of the energy storage unit (1); the air outlet end of the expansion unit (2-1) is connected to a premixing tank (2-2); and the premixing tank (2-2) is connected to a hydrogen energy internal combustion engine unit (2-3).

2. The compressed air energy storage system according to claim 1, characterized in that: It also comprises a compression unit (3), the compression unit (3) comprising at least two sets of compressor units, the gas outlet ends of the compressor units being correspondingly connected to the corresponding storage tanks (1-1) of the energy storage unit (1).

3. The operating method of the compressed air energy storage system according to claim 2, characterized in that: The following steps are involved: S1. When the electricity consumption is low, the compressor group of the compression unit (3) compresses hydrogen and oxygen into the elastic air bag (1-3) in the corresponding storage tank (1-1), and the elastic air bag (1-3) expands to push the piston (1-2) and the liquid medium upward, so that the pressure in the elastic air bag (1-3) is not less than 30 MPa; S2. During peak electricity consumption, the energy storage unit (1) is connected to the energy release unit (2), and hydrogen and oxygen enter the corresponding expansion unit (2-1) through the one-way valve respectively. The expansion unit (2-1) drives the generator set to generate electricity. The hydrogen and oxygen output from the expansion unit (2-1) enter the premixing tank (2-2) for mixing. The mixed gas is input into the hydrogen internal combustion engine unit (2-3), and the hydrogen internal combustion engine unit (2-3) drives the generator set to generate electricity.

4. The operating method of the compressed air energy storage system according to claim 3, characterized in that: In step S1, hydrogen and oxygen are compressed step by step through a primary compressor, a secondary compressor and a tertiary compressor respectively; the primary compressor compresses the gas to 1.2MPa, and cools it to 40°C through a shell and tube cooler; the secondary compressor compresses the gas to 10.5MPa, and cools it to 55°C through a shell and tube cooler; the tertiary compressor compresses the gas to 35MPa, and cools it to 170°C through a shell and tube cooler; the medium after absorbing heat in the shell and tube cooler enters the insulation tank for storage.

5. The method for operating a compressed air energy storage system according to claim 4, characterized in that: In step S2, the 30 MPa gas in the storage tank (1-1) is first heated to 300° C. by an electric heat accumulator before entering the expansion unit (2-1).

6. The operating method of the compressed air energy storage system according to claim 5, characterized in that: In step S2, the expansion unit (2-1) is preheated using the medium in the heat preservation tank.

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