Compressed air energy storage system and operation method

Abstract

The present invention relates to the field of energy storage technology, and provides a compressed air energy storage system and an operating method. The system includes a gas storage device, a compression branch, an expansion branch, and a heat storage circuit. The compression branch is used to compress ambient air and store it in the gas storage device; the expansion branch is used to expand the stored compressed gas by heating to drive the power generation equipment to generate electricity; the heat storage circuit is used to use the heat generated during the air compression process to heat the compressed air in the energy release stage. The heat storage circuit includes a cold storage device, a first circulation pump, a heat storage heat exchanger, a heat storage device, a second circulation pump, and a heat recovery heat exchanger connected end to end in sequence; the gas outlet of the heat storage heat exchanger is connected to the outlet of the gas storage device through a first pipeline, and the gas inlet of the heat storage heat exchanger is connected to the expansion branch through a second pipeline. A heat supply branch is connected to the heat storage heat exchanger. The present invention can improve the response speed of the compressed air energy storage system, so that the compressed air energy storage system can quickly meet the dispatching requirements of the power system.

Description

Technical Field

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

[0002] Energy systems collect energy from various sources and convert it into the different energy forms needed for daily life and production, playing a key role in ensuring social and economic development. Energy sources such as fossil fuels can be supplied dynamically based on user demand. That is, when user demand decreases, they can be easily stored at any link between the supply end and the user end, thus maintaining the dynamic balance of the entire energy system.

[0003] With the trend of green and sustainable development, the penetration rate of renewable energy in the energy supply chain has gradually increased. On the one hand, it promotes the development of traditional energy systems into new energy systems, but it also brings new challenges to the energy system. Renewable energy such as wind energy and solar energy has natural volatility and randomness, and lacks native carriers that are easy to store. The large-scale application of volatile renewable energy may disrupt the original dynamic balance of the energy system. This potential threat is more significant in power systems with transient energy transmission. Fluctuations in electric energy can easily cause fluctuations in the voltage and frequency of the power system, resulting in reduced quality of power supply and may even lead to power system accidents.

[0004] By storing the energy (electricity, heat, etc.) generated by fluctuating renewable energy sources such as wind and solar power through appropriate carriers (i.e., energy storage), the impact of large-scale fluctuating renewable energy grid connection on the stable operation of the power grid can be reduced, and the pressure on auxiliary service demand such as peak and valley load regulation of the power grid can be alleviated, thereby achieving the same effect of storing fossil fuels to maintain the dynamic balance of traditional energy systems. Therefore, energy storage is one of the key supporting technologies to promote large-scale friendly access to the grid for fluctuating renewable energy power and accelerate the construction of a new power system.

[0005] Compressed air energy storage (CAES), a long-duration, high-capacity energy storage technology comparable to pumped hydro, represents a common path for gas energy storage technologies, including liquefied air storage, compressed carbon dioxide storage, and Carnot batteries. It boasts significant advantages, including large storage capacity, extended power generation time, long service life, low explosion risk, and the ability to generate combined cooling, heating, and power. Traditional supplementary combustion CAES technology requires the combustion of a mixture of air and natural gas to generate power, using the resulting high-temperature flue gas for expansion and work. This leads to natural gas dependence and secondary carbon emissions.

[0006] To this end, the traditional supplementary combustion compressed air energy storage system has been optimized and improved. By adopting a large pressure ratio quasi-adiabatic compression process, the air is compressed to a high temperature during the compression process and then the high-temperature (high-grade) compressed heat energy is stored. This is then used to heat the expander intake air, thereby replacing the combustion heating of natural gas and eliminating natural gas dependence and secondary carbon emissions.

[0007] Although the improved compressed air energy storage system can eliminate natural gas dependence and secondary carbon emissions. However, when the power system requires the compressed air energy storage system to increase the output power, the gas storage device gradually increases the output gas volume, and at the same time, the heat exchanger in front of the expander gradually increases the compressed heat energy input, thereby meeting the heating demand of the atmospheric volume and the atmospheric volume intake demand at the rated operating temperature of the expander. In this regulation process, the heat and mass transfer process is affected by the time scale, the pressure increase rate is limited by the inherent conditions of the pipeline network, and the temperature increase rate of the heat exchanger and pipeline system is affected by structural stress factors. As a result, the power increase rate of the expander is limited, and the start-up rate and regulation rate of the expander are both limited. Summary of the Invention

[0008] The present invention provides a compressed air energy storage system and an operating method to address the defects of the prior art in that the system startup rate and regulation rate are limited. The system can improve the response speed of the compressed air energy storage system and enable the compressed air energy storage system to quickly meet the dispatching requirements of the power system.

[0009] A first aspect of the present invention provides a compressed air energy storage system, comprising an air storage device, a compression branch, an expansion branch, and a heat storage circuit.

[0010] The compression branch is used to compress the ambient air and store it in the air storage device;

[0011] The expansion branch is used to expand the compressed gas stored in the gas storage device by heating, so as to drive the power generation equipment to generate electricity;

[0012] The heat storage circuit is used to use the heat generated during the air compression process to heat the compressed air in the energy release stage. The heat storage circuit includes a cold storage device, a first circulation pump, a heat storage heat exchanger, a heat storage device, a second circulation pump and a heat recovery heat exchanger connected end to end in sequence; the gas outlet of the heat storage heat exchanger is connected to the outlet of the gas storage device through a first pipeline, and the gas inlet of the heat storage heat exchanger is connected to the expansion branch through a second pipeline. A heat supply branch is connected to the heat storage heat exchanger.

[0013] According to the compressed air energy storage system provided by the present invention, the heat supplement branch includes a third pipeline, a fourth pipeline and a fifth pipeline;

[0014] The third pipeline is connected to the outlet of the heat storage device and the inlet of the first circulation pump; the fourth pipeline is connected to the outlet of the first circulation pump and the heat exchange medium outlet of the heat storage heat exchanger; the fifth pipeline is connected to the heat exchange medium inlet of the heat storage heat exchanger and the outlet of the cold storage device.

[0015] The compressed air energy storage system provided by the present invention further includes a first valve and a second valve;

[0016] The first valve is arranged on the pipeline between the outlet of the air storage device and the air inlet of the heat exchanger; the second valve is arranged on the pipeline between the air outlet of the heat exchanger and the expansion branch, and the first valve and the second valve are both used to control the opening and closing of the corresponding pipelines.

[0017] According to the compressed air energy storage system provided by the present invention, the first valve is provided at a position close to the outlet valve of the gas storage device or close to the regenerative heat exchanger;

[0018] And / or, the second valve is arranged at a position close to the main gas valve of the expansion unit in the expansion branch.

[0019] According to the compressed air energy storage system provided by the present invention, the compression branch includes a plurality of compressor groups, the plurality of compressor groups are arranged in series or in parallel, and the heat storage heat exchanger is correspondingly provided at the air outlet of each compressor group;

[0020] The compressor unit at the first stage is connected to the ambient air, and the compressor unit at the last stage is connected to the air inlet of the corresponding heat storage heat exchanger.

[0021] The compressed air energy storage system provided according to the present invention also includes a gas-liquid separator, which is connected to the pipeline between the air outlet of the heat storage heat exchanger and the inlet of the gas storage device, and is used to separate the gas-liquid mixture entering the gas-liquid separator, and allow the air after the liquid component is separated to enter the gas storage device for storage.

[0022] According to the compressed air energy storage system provided by the present invention, the expansion branch includes a plurality of expansion units, the plurality of expansion units are arranged in series or in parallel, and the regenerative heat exchanger is correspondingly provided at the air outlet of each expansion unit;

[0023] The expansion unit at the first stage is connected to the air outlet of the corresponding heat recovery heat exchanger and the second pipeline, and the expansion unit at the last stage is connected to the power generation equipment.

[0024] The compressed air energy storage system provided by the present invention is connected to a heat storage heat exchanger by connecting a heat supplement branch, connecting a first pipeline between the gas outlet of the heat storage heat exchanger and the outlet of the gas storage device, and connecting a second pipeline between the gas inlet of the heat storage heat exchanger and the inlet of the expansion branch. When it is necessary to quickly increase the output power of the expansion branch, the compressed air released by the gas storage device is controlled to enter the gas outlet of the heat storage heat exchanger through the first pipeline, and after heat exchange with the heat supplement branch, enter the second pipeline from the gas inlet of the heat storage heat exchanger, and replenish air for the expansion branch through the second pipeline. At this time, it is equivalent to the heat storage heat exchanger and the heat recovery heat exchanger in the compressed air energy storage system both working to exchange heat. The two heat exchangers can produce more compressed air below the rated working conditions and supply compressed air to the expansion branch at the same time. The heated compressed air is supplemented to the expansion branch, which can enable the expansion branch to reach the working gas volume faster, that is, the compressed air energy storage system quickly reaches a full load state in a short time, so as to improve the response speed of the compressed air energy storage system and enable the compressed air energy storage system to quickly meet the scheduling requirements of the power system.

[0025] By adding heated compressed air to the expansion branch, the limited working temperature and pressure increase rate can be compensated by quickly increasing the working gas volume, thereby avoiding the thermal stress caused by the rapid temperature rise during the expansion process, ensuring the smooth operation of the expansion unit, and avoiding potential damage to the heat exchanger, expansion unit and expansion branch piping due to excessive changes in temperature and pressure differences.

[0026] A second aspect of the present invention provides a method for operating a compressed air energy storage system according to any one of the preceding claims, comprising the following steps:

[0027] Determining whether the expansion branch in the compressed air energy storage system is being started for the first time or in a cold state, controlling the first valve to open for the first time, controlling the second valve to close, and injecting gas into the energy release pipeline including the expansion branch at a low pressure increase rate using the gas storage device;

[0028] When it is determined that the pressure in the expansion branch and the pressure on the air side of the regenerative heat exchanger have reached the preset working pressure, the first valve is kept open, the second valve is controlled to open, and the main air valve of the expansion unit in the expansion branch is adjusted to start the expansion branch for the first time.

[0029] According to the operating method of the compressed air energy storage system provided by the present invention, the operating method further includes:

[0030] When the expansion unit of the expansion branch needs to be shut down after the first startup, the main gas valve of the expansion unit is closed first, and then the first valve and the second valve are closed to seal the regenerative heat exchanger and part of the pipe system at both ends, so that the regenerative heat exchanger and part of the pipe system at both ends are maintained at a preset pressure, wherein the preset pressure is the intermediate pressure between the ambient pressure and the gas storage device.

[0031] According to the operating method of the compressed air energy storage system provided by the present invention, the operating method further includes:

[0032] If a command is received from the power system requesting a rapid increase in the output power of the expansion branch, the compressed air released by the gas storage device is controlled to enter the gas outlet of the heat storage heat exchanger through the first pipeline, and then enter the heat storage heat exchanger through the heat replenishment branch for heat exchange, and then enter the second pipeline from the gas inlet of the heat storage heat exchanger, and replenish the expansion branch with air through the second pipeline;

[0033] When it is determined that the output power of the expansion branch reaches the rated output power, the flow of the first pipeline is controlled to decrease, the flow of the heat supply branch is controlled to decrease; and the air flow and the flow of the heat exchange medium in the expansion branch are controlled to increase.

[0034] The operating method of the compressed air energy storage system provided by the present invention can compensate for the response hysteresis characteristics of the system under the limitations of the boost rate and the heating rate by adjusting the operating measures, and can significantly shorten the system's startup response and power regulation response time. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 This is a system block diagram of a compressed air energy storage system provided by an embodiment of the present invention.

[0037] Figure 2 This is a partial system block diagram of the compressed air energy storage system provided by an embodiment of the present invention.

[0038] Figure 3 This is a schematic diagram of the usage status of the compressed air energy storage system provided by an embodiment of the present invention during the energy storage stage.

[0039] Figure 4 It is a schematic diagram of the state of the compressed air energy storage system provided by an embodiment of the present invention during the air replenishment process.

[0040] Figure 5 It is a schematic diagram of the usage status of the compressed air energy storage system provided by an embodiment of the present invention during the energy release stage.

[0041] Reference numerals:

[0042] 10. Gas storage device; 20. Compression branch; 21. Compressor unit; 22. Gas-liquid separator; 30. Expansion branch; 31. Expansion unit; 40. Heat storage circuit; 41. Cold storage device; 42. First circulation pump; 43. Heat storage heat exchanger; 44. Heat storage device; 45. Second circulation pump; 46. Regenerative heat exchanger; 47. First pipeline; 48. Second pipeline; 50. Heat supply branch; 51. Third pipeline; 52. Fourth pipeline; 53. Fifth pipeline; 60. First valve; 70. Second valve. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0044] In the description of the embodiments of this application, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on the specific circumstances.

[0045] In the embodiments of the present application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0046] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0047] The compressed air energy storage system operates as follows when responding to power system dispatch: the air storage device releases low-temperature compressed air, which enters the expansion branch at a specific pressure increase ratio under the control of the pipeline valve system to prevent damage to equipment and pipelines caused by rapid pressure increase in the pipeline system. Upon entering the pipeline system, the compressed air first enters the heat exchanger before the expander. Heated by the system's stored compression heat, the air gradually reaches operating temperature at a specific rate to prevent damage to equipment and pipelines caused by rapid temperature increase. The heated compressed air then enters the expansion branch, where it is decompressed and performs work, driving the expander and generator to output electrical energy.

[0048] The pressure increase rate when the expansion branch is started will be affected by a series of inherent conditions of the pipeline network. For example, the diameter, length and material of the pipeline determine the resistance to gas flow, which directly affects the pressure increase rate. Thinner or longer pipelines will lead to greater friction losses and reduce the gas flow rate; the opening of the valve directly affects the gas flow area. Too small an opening will increase the flow resistance, thereby slowing down the pressure increase rate; the type, power and efficiency of the compressor also determine the pressure increase rate. The volume of the storage tank or other storage facilities and the design of the connecting pipelines also affect the speed of gas supply and pressure recovery. Therefore, the limited pressure increase rate may cause the system to be unable to respond quickly to load changes, affecting service quality and production efficiency. Unnecessary resistance and inefficient compression process will cause energy waste and increase operating costs. To this end, the present invention provides an improved compressed air energy storage system, the purpose of which is to achieve rapid response and regulation.

[0049] Figure 1 This is a system block diagram of a compressed air energy storage system provided by an embodiment of the present invention.

[0050] See Figure 1 An embodiment of the present invention provides a compressed air energy storage system, which includes an air storage device 10, a compression branch 20, an expansion branch 30 and a heat storage circuit 40.

[0051] The gas storage device 10 is used to store compressed air. The gas storage device 10 may be a gas storage reservoir or a gas storage tank. When the gas storage device 10 is a gas storage tank, it may be a tank body in the form of a mother-and-child tank, a cryogenic spherical tank, or the like.

[0052] The compression branch 20 is used to compress ambient air and store it in the air storage device 10. The compression branch 20 includes multiple compressor units 21, which are arranged in series or in parallel. A thermal storage heat exchanger 43 is provided at the air outlet of each compressor unit 21. The first-stage compressor unit 21 is connected to the ambient air, while the last-stage compressor unit 21 is connected to the air inlet of the corresponding thermal storage heat exchanger 43.

[0053] Additionally, compression branch 20 may include an air filter and a molecular sieve purifier. The air filter removes dust and other impurities from the ambient air, while the molecular sieve purifier removes moisture, CO2, and other hydrocarbons from the air. During the air compression process, the molecular sieve purifier removes moisture, CO2, and other hydrocarbons from the air passing through the cold storage circuit, preventing them from solidifying and clogging the heat exchange channels in the cold storage circuit's low-temperature environment.

[0054] The compression branch 20 also includes a gas-liquid separator 22, which is connected to the pipeline between the air outlet of the heat storage heat exchanger 43 and the inlet of the gas storage device 10, and is used to separate the gas-liquid mixture entering the gas-liquid separator 22, and allow the air after the liquid component is separated to enter the gas storage device 10 for storage. The liquid component separated by the gas-liquid separator 22 can be discharged to a designated location, which can be a sewage system, etc.

[0055] The expansion branch 30 is used to heat and expand the compressed gas stored in the gas storage device 10 to drive the power generation equipment. The expansion branch 30 includes multiple expansion units 31, which are arranged in series or parallel. A regenerative heat exchanger 46 is provided at the air outlet of each expansion unit 31. The first-stage expansion unit 31 is connected to the air outlet of the corresponding regenerative heat exchanger 46 and a second pipeline 48. The final-stage expansion unit 31 is connected to the power generation equipment.

[0056] The heat storage circuit 40 is used to use the heat generated during the air compression process to heat the air in the energy release stage. The heat storage circuit 40 includes a cold storage device 41, a first circulation pump 42, a heat storage heat exchanger 43, a heat storage device 44, a second circulation pump 45 and a heat recovery heat exchanger 46 connected end to end in sequence; the gas outlet of the heat storage heat exchanger 43 is connected to the outlet of the gas storage device 10 through a first pipeline 47, and the gas inlet of the heat storage heat exchanger 43 is connected to the expansion branch 30 through a second pipeline 48. A heat supply branch 50 is connected to the heat storage heat exchanger 43.

[0057] When the output power of the expansion branch 30 needs to be rapidly increased, the compressed air released by the gas storage device 10 enters the gas outlet of the thermal storage heat exchanger 43 through the first pipeline 47. After exchanging heat with the heat exchange medium in the thermal storage heat exchanger 43 through the heat replenishment branch 50, the compressed air enters the second pipeline 48 from the gas inlet of the thermal storage heat exchanger 43 and replenishes the expansion branch 30 through the second pipeline 48. At this point, the thermal storage heat exchanger 43 and the regenerative heat exchanger 46 in the compressed air energy storage system are operating simultaneously to exchange heat. The two heat exchangers can produce more compressed air below the rated operating conditions and simultaneously supply compressed air to the expansion branch 30.

[0058] Since the power of the expansion unit 31 in the expansion branch 30 is related to the pressure, flow rate and temperature of the compressed air, that is, W=f(m,p,T), and since the compression branch 20 is not working when the expansion branch 30 is working, when it is necessary to quickly increase the output power of the expansion branch 30, part of the compressed air released by the gas storage device 10 enters the gas outlet of the heat storage heat exchanger 43 through the first pipeline 47, and exchanges heat with the heat exchange medium in the heat storage heat exchanger 43 through the heat supplement branch 50, and then is discharged from the heat storage heat exchanger 43. The gas inlet of the heat exchanger 43 enters the second pipeline 48 and supplies air to the expansion branch 30 through the second pipeline 48. The second pipeline 48 and the expansion branch 30 simultaneously supply air to the expansion unit 31 at the original P / T increase rate. The air supply volume is greater than the air volume when only the expansion branch 30 supplies air. Therefore, the air intake volume m of the expansion unit 31 increases faster and the power increases faster, thereby rapidly increasing the output power W of the expansion unit 31, enabling the compressed air energy storage system to quickly meet the dispatching requirements of the power system.

[0059] The heat replenishment branch 50 can be composed of the compressed air energy storage system's own structure connected by piping, utilizing the heat generated during the compression phase. Alternatively, a small amount of fuel (such as natural gas) can be introduced into the heat replenishment branch 50 to burn and heat water vapor or air itself. Heat replenishment branch 50 can also utilize external heat sources such as factory waste heat and solar collectors for energy utilization and heat replenishment.

[0060] It can be understood that the compressed air energy storage system provided in the embodiment of the present invention connects the heat replenishment branch 50 to the heat storage heat exchanger 43, connects the first pipeline 47 between the gas outlet of the heat storage heat exchanger 43 and the outlet of the gas storage device 10, and connects the second pipeline 48 between the gas inlet of the heat storage heat exchanger 43 and the inlet of the expansion branch 30. When the output power of the expansion branch 30 needs to be quickly increased, the compressed air released by the gas storage device 10 is controlled to enter the gas outlet of the heat storage heat exchanger 43 through the first pipeline 47, and after the heat storage heat exchanger 43 in the heat replenishment branch 50 exchanges heat with the heat exchange medium, it enters the second pipeline 48 from the gas inlet of the heat storage heat exchanger 43, and replenishes air for the expansion branch 30 through the second pipeline 48. At this time, it is equivalent to the heat storage heat exchanger 43 and the heat recovery heat exchanger 46 in the compressed air energy storage system working simultaneously to exchange heat. The two heat exchangers can produce more compressed air below the rated operating conditions and supply compressed air to the expansion branch 30 at the same time. The heated compressed air is supplemented to the expansion branch 30, which can enable the expansion branch 30 to reach the working air volume faster, that is, the compressed air energy storage system quickly reaches the full load state in a short time, so as to improve the response speed of the compressed air energy storage system and enable the compressed air energy storage system to quickly meet the scheduling requirements of the power system.

[0061] By adding heated compressed air to the expansion branch 30, the limited working temperature and pressure increase rate can be compensated by quickly increasing the working gas volume, thereby avoiding thermal stress caused by a sharp temperature rise during the expansion process, ensuring the smooth operation of the expansion unit 31, and avoiding potential damage to the heat exchanger 46, the expansion unit 31 and the piping of the expansion branch 30 due to excessive changes in temperature and pressure differences.

[0062] Continue reading Figure 1 In some embodiments of the present invention, the heat supplement branch 50 includes a third pipeline 51 , a fourth pipeline 52 and a fifth pipeline 53 .

[0063] The third pipeline 51 is connected to the outlet of the heat storage device 44 and the inlet of the first circulation pump 42; the fourth pipeline 52 is connected to the outlet of the first circulation pump 42 and the heat exchange medium outlet of the heat storage heat exchanger 43; the fifth pipeline 53 is connected to the heat exchange medium inlet of the heat storage heat exchanger 43 and the outlet of the cold storage device 41.

[0064] This is equivalent to using the heat energy generated in the air compression stage to supplement the heat for the heat replenishment branch 50 in the embodiment of the present invention, so that the heat storage heat exchanger 43 can be reused and the power regulation response speed of the system can be improved. At the same time, when the system needs to maintain a power higher than the rated power for a long time, the heat replenishment branch 50 and the expansion branch 30 can work simultaneously to supply air to the expansion unit 31, thereby reducing the system's demand for an excessively large heat exchange area for the regenerative heat exchanger 46, and avoiding the deviated operation of the heat exchanger when switching between rated power generation and over-rated power generation under the condition that the regenerative heat exchanger 46 operates alone, thereby improving the energy utilization rate and energy conversion efficiency of the entire compressed air energy storage system.

[0065] Therefore, the compressed air energy storage system provided by the embodiment of the present invention can not only quickly and efficiently convert stored potential energy into kinetic energy when needed, but also use the system's own heat to replenish the compressed gas during the expansion process, thereby improving the overall energy conversion rate of the compressed air energy storage system, increasing equipment utilization, reducing operating costs, and enhancing system reliability.

[0066] Figure 2 This is a partial system block diagram of the compressed air energy storage system provided by an embodiment of the present invention.

[0067] See Figure 2 In some embodiments of the present invention, the compressed air energy storage system further includes a first valve 60 and a second valve 70. The first valve 60 and the second valve 70 can both be valves for controlling the on-off of the pipeline.

[0068] The first valve 60 is arranged on the pipeline between the outlet of the air storage device 10 and the air inlet of the heat exchanger 46; the second valve 70 is arranged on the pipeline between the air outlet of the heat exchanger 46 and the expansion branch 30. The first valve 60 and the second valve 70 are both used to control the opening and closing of the corresponding pipelines.

[0069] In some embodiments of the present invention, the first valve 60 is located near the outlet valve of the gas storage device 10 or near the heat exchanger 46, and the second valve 70 is located near the main gas valve of the expansion unit 31 in the expansion branch 30.

[0070] In other words, a first valve 60 and a second valve 70 are respectively provided on the energy release pipeline at a certain distance from each end of the gas side of the regenerative heat exchanger 46. The first valve 60 and the second valve 70 are used to control the opening and closing of the energy release pipeline. The first valve 60 is located near the outlet valve of the gas storage device 10 or near the regenerative heat exchanger 46, and the second valve 70 is located near the main gas valve of the expansion unit 31.

[0071] In some embodiments of the present invention, the first valve 60 can be located near the outlet valve of the gas storage device 10, and the second valve 70 can be located at any position on the pipeline between the air outlet of the regenerative heat exchanger 46 and the expansion branch 30. Alternatively, the second valve 70 can be located near the main gas valve of the expansion unit 31 in the expansion branch 30, and the first valve 60 can be located at any position on the pipeline between the outlet of the gas storage device 10 and the air inlet of the regenerative heat exchanger 46.

[0072] When the expansion unit 31 of the expansion branch 30 is started for the first time, Figure 2 As shown, first, the first valve 60 is opened, and the gas storage device 10 injects gas into the energy release pipeline at a low pressure increase rate, gradually bringing the piping system and the gas side of the regenerative heat exchanger 46 to the operating pressure. Subsequently, the second valve 70 is opened, and the expansion unit 31, under the regulation of its own main gas valve, autonomously adjusts the intake air flow rate, completing the startup of each expansion unit 31 in the expansion branch 30.

[0073] When the expansion unit 31 of the expansion branch 30 is shut down, the main air valve of the expansion unit 31 itself is closed first, and then the first valve 60 and the second valve 70 are closed to seal the regenerative heat exchanger 46 and part of the pipe system at both ends, so that the regenerative heat exchanger 46 and part of the pipe system at both ends are maintained at a preset pressure, so that before the next start-up of the expansion unit 31, there is no need to slowly increase the pressure of the energy release pipeline, and the regenerative heat exchanger 46 and the pipe system at both ends can reach or approach the rated working pressure in advance, thereby shortening the pressure increase time of the regenerative heat exchanger 46 and the pipe system at both ends, and quickly meeting the startup conditions.

[0074] Among them, the preset pressure can be the working pressure of the heat exchanger 46 and the pipe systems at both ends. The preset pressure can also be half of the working pressure or other suitable pressure lower than the working pressure. The preset pressure can be selected according to actual conditions. The preset pressure is preferably the intermediate pressure between the ambient pressure and the gas storage device 10, and is generally designed according to the expansion branch pipe system and the pressure increase rate allowed by the main equipment.

[0075] An embodiment of the present invention further provides an operating method of a compressed air energy storage system based on any one of the items, comprising the following steps:

[0076] Step S100: Determine whether the expansion branch 30 in the compressed air energy storage system is started for the first time or is in a cold state after a long shutdown, control the first valve 60 to open, the second valve 70 to close, and the gas storage device 10 to inject gas into the expansion branch 30 at a low pressure increase rate.

[0077] It is understandable that determining whether the expansion branch 30 in the compressed air energy storage system is started for the first time mainly depends on the pressure and temperature of the gas storage branch piping system and the main equipment structural components and internal components. If the pressure or temperature is significantly lower than the rated operating temperature or close to the ambient temperature, then within the allowable range of the heating and pressure increase rates of the piping system and equipment, the system startup will take longer for the piping system and main equipment to reach the rated pressure or temperature.

[0078] When it is determined that the expansion branch 30 in the compressed air energy storage system is being started for the first time or in a cold state, the first valve 60 is controlled to open and the second valve 70 is controlled to close, and the gas storage device 10 injects gas into the expansion branch 30 at a low pressure increase rate. When it is determined that the expansion branch 30 in the compressed air energy storage system is not being started for the first time, the first valve 60 and the second valve 70 can be opened simultaneously.

[0079] Step S200: When it is determined that the pressure in the expansion branch 30 and the pressure on the air side of the heat exchanger 46 have reached the preset working pressure, the first valve 60 is kept open, the second valve 70 is controlled to be open, and the main air valve of the expansion unit 31 is autonomously adjusted to start the expansion branch 30 for the first time.

[0080] It is understandable that pressure sensors are used to monitor the pressure levels of various parts of the system. For example, precise pressure sensors are installed at the inlet and outlet of the expansion branch 30 and the regenerative heat exchanger 46 to ensure that all key measurement points are covered. When the compressed air energy storage system is started, the monitoring screen will display the real-time pressure reading. The real-time pressure reading is compared with the preset working pressure to determine whether the pressure in the expansion branch 30 and the pressure on the air side of the regenerative heat exchanger 46 have reached the preset working pressure. In addition, early warning limits are set in the control system of the compressed air energy storage system. When the pressure is lower than or higher than the predetermined value, the control system automatically triggers an alarm or takes corrective measures.

[0081] When it is determined that the pressure in the expansion branch 30 and the pressure on the air side of the heat exchanger 46 have reached the preset working pressure, the first valve 60 is kept open, the second valve 70 is controlled to be open, and the main air valve of the expansion unit 31 is adjusted autonomously to start the expansion branch 30 for the first time.

[0082] In some embodiments of the present invention, the operating method of the compressed air energy storage system also includes: when the expansion unit 31 of the expansion branch 30 needs to be shut down after the first startup, first close the main air valve of the expansion unit 31 itself, and then close the first valve 60 and the second valve 70 to seal the heat exchanger 46 and part of the pipe system at both ends, so that the heat exchanger 46 and part of the pipe system at both ends are maintained at a preset pressure, so that before the expansion unit 31 is started next time, there is no need to slowly increase the pressure of the expansion branch 30, and the heat exchanger 46 and the pipe system at both ends can be made to reach or approach the rated working pressure in advance, thereby shortening the pressure increase time of the heat exchanger 46 and the pipe system at both ends, and quickly meeting the startup conditions.

[0083] In some embodiments of the present invention, the method for operating the compressed air energy storage system further includes:

[0084] If an instruction is received from the power system to quickly increase the output power of the expansion branch 30, the compressed air released by the gas storage device 10 is controlled to enter the gas outlet of the heat storage heat exchanger 43 through the first pipeline 47, and after heat exchange with the heat exchange medium in the heat storage heat exchanger 43 through the heat supply branch 50, enter the second pipeline 48 from the gas inlet of the heat storage heat exchanger 43, and supply air to the expansion branch 30 through the second pipeline 48.

[0085] When it is determined that the output power of the expansion branch 30 reaches the rated output power, the flow of the first pipeline 47 is controlled to decrease until all pipelines are closed, and the flow of the heat supply branch 50 is controlled to decrease until all pipelines are closed; the air flow and the flow of the heat exchange medium in the expansion branch 30 are controlled to increase, and the output power of the expansion branch 30 is tracked and maintained stable.

[0086] Figure 3 This is a schematic diagram of the usage status of the compressed air energy storage system provided by an embodiment of the present invention during the energy storage stage. Figure 4 It is a schematic diagram of the state of the compressed air energy storage system provided by an embodiment of the present invention during the air replenishment process. Figure 5 It is a schematic diagram of the usage status of the compressed air energy storage system provided by an embodiment of the present invention during the energy release stage.

[0087] The compressed air energy storage system's response to the power system includes both an energy storage mode and an energy release or power generation mode. The compressed air energy storage system provided by this embodiment primarily optimizes the startup response and power regulation characteristics of this mode. This mode can be divided into three dynamic processes: the expansion unit 31's startup preparation phase, startup phase, and operational regulation phase.

[0088] like Figure 3As shown, in the energy storage working mode (energy storage stage), the compressed air energy storage system operates in the compression branch 20 composed of the compressor unit 21, the gas side of the thermal storage heat exchanger 43, the gas-liquid separator 22 and the gas storage device 10 connected in sequence, while the heat storage branch composed of the cold storage device 41, the first circulation pump 42, the liquid side of the thermal storage heat exchanger 43 and the heat storage device 44 connected in sequence operates.

[0089] The ambient air is heated and pressurized under the action of the compressor unit 21. The compressed air first flows through the gas side of the heat storage heat exchanger 43 and exchanges heat with the low-temperature heat storage medium pumped from the cold storage device 41 to the liquid side of the heat storage heat exchanger 43 via the first circulation pump 42. The heat storage medium absorbs heat and heats up before entering the heat storage device 44 for storage. The compressed air releases heat and cools down before entering the gas-liquid separator 22 to separate the condensate (liquid components such as water). The air after the condensate (liquid components) is separated finally enters the gas storage device 10 for storage.

[0090] like Figure 2 As shown, during the start-up preparation process of the expansion unit 31 , it is necessary to determine whether the expansion unit 31 is started for the first time (cold state) or not for the first time (cold state).

[0091] When the expansion unit 31 is initially started (from a cold state), the first valve 60 on the energy release line is controlled to open, while the second valve 70 is closed. The gas storage device 10 injects gas into the expansion branch 30 at a low pressure increase rate, gradually bringing the piping system and the gas side of the regenerative heat exchanger 46 to the operating pressure. Subsequently, the second valve 70 is opened, and the expansion branch 30, under the control of its own main gas valve, autonomously regulates the intake air flow, completing the startup of each expansion unit 31 in the expansion branch 30.

[0092] When the expansion unit 31 of the expansion branch 30 is shut down, the main gas valve of the expansion branch 30 itself is closed first, and then the first valve 60 and the second valve 70 are closed to seal the regenerative heat exchanger 46 and part of the pipe system at both ends, so that the regenerative heat exchanger 46 and part of the pipe system at both ends are maintained at a preset pressure. Therefore, before the expansion unit 31 is started next time, there is no need to slowly increase the pressure of the expansion branch 30. The regenerative heat exchanger 46 and the pipe system at both ends can reach or approach the rated working pressure in advance, thereby shortening the pressure increase time of the regenerative heat exchanger 46 and the pipe system at both ends, and quickly meeting the startup conditions.

[0093] like Figure 4As shown, during the startup of the expansion unit 31, the energy release pipeline formed by the gas storage device 10, the gas side of the heat storage heat exchanger 46, and the expansion unit 31 connected in sequence operates; the heat recovery branch formed by the heat storage device 44, the second circulation pump 45, the liquid side of the heat storage heat exchanger 46, and the cold storage device 41 connected in sequence operates; the gas supply branch formed by the gas storage device 10, the gas side of the heat storage heat exchanger 43, and the expansion unit 31 connected in sequence operates; and the heat supply branch 50 formed by the heat storage device 44, the first circulation pump 42, the liquid side of the heat storage heat exchanger 43, and the cold storage device 41 connected in sequence operates.

[0094] The compressed air released from the air storage device 10 passes through the regenerative heat exchanger 46 in the energy release pipeline and the gas side of the heat storage heat exchanger 43 in the heat replenishment branch 50, respectively, where it is reheated and regenerated with the heat storage medium from the heat storage device 44. At this point, the regenerative heat exchanger 46 and the corresponding piping are still limited by the inherent temperature rise rate of the structure. However, the simultaneous operation of the regenerative heat exchanger 43 and the regenerative heat exchanger 46 in the compressed air energy storage system can produce more compressed air below the rated operating temperature and simultaneously supply compressed air to the expansion branch 30. Since the power of the expander 31 in the expansion branch 30 is related to the pressure, flow rate, and temperature of the compressed air, namely, W = f(m, p, T), while maintaining the original increase rate of the expander 31's inlet pressure p and T, the compressed air flow rate m can be rapidly increased, thereby rapidly increasing the output power W of the expander 31, allowing the compressed air energy storage system to quickly meet the dispatch requirements of the power system.

[0095] As the temperature of the compressed air output by the heat storage heat exchanger 43 and the heat recovery heat exchanger 46 gradually increases, the amount of compressed air is gradually increased, maintained, or decreased according to the output power requirement of the expansion unit 31 until the expansion unit 31 reaches the rated output power. At this time, the compressed air flow rate of the air supply branch and the heat storage medium flow rate of the heat supply branch 50 gradually decrease, while the compressed air flow rate of the expansion branch 30 and the heat storage medium flow rate of the heat recovery branch gradually increase. Under the condition of maintaining the rated output power of the expansion unit 31 unchanged, the workload is completely transferred from the air supply branch and the heat supply branch 50 to the expansion branch 30 and the heat recovery branch. At this time, the working process of the compressed air energy storage system is as follows: Figure 5 During the entire operation process, the heat storage medium after releasing heat through the heat storage heat exchanger 43 and the heat recovery heat exchanger 46 is returned to the cold storage device 41 for storage.

[0096] like Figure 4 and Figure 5 , the operation adjustment process of the expansion unit 31 of the expansion branch 30: If the expansion unit 31 is in normal operation, such as Figure 5 As shown in FIG, the power system issues a command to quickly reduce the output power, which can be achieved by simultaneously reducing the flow in the energy release pipeline and the heat recovery branch.

[0097] If the power system issues a command to quickly increase the output power, the air supply branch and the heat supply branch 50 are restarted, that is, the compressed air energy storage system is restarted. Figure 5 The usage status shown is entered Figure 4 The usage status shown. By the simultaneous operation of the two groups of heat exchangers, the heat storage heat exchanger 43 and the heat recovery heat exchanger 46, the intake flow rate of the expansion unit 31 can be quickly increased to compensate for the power increase hysteresis effect caused by the time scale in the heat exchange process, and to achieve a rapid increase in the output power of the expansion unit 31. Similarly, as the exhaust temperature of each heat exchanger increases, the flow rate of the air supply branch and the heat supply branch 50 is gradually adjusted, and finally the workload is completely transferred to the expansion branch 30 and the heat recovery branch. During the entire operation process, the heat storage working fluid after releasing heat through the heat storage heat exchanger 43 and the heat recovery heat exchanger 46 is returned to the cold storage device 41 for storage.

[0098] The compressed air energy storage system provided by the embodiments of the present invention, through innovative system technology and corresponding operational measures, can compensate for the system's response hysteresis characteristics due to the limitations of the boost rate and heating rate, and can significantly shorten the system's startup response and power regulation response time. The specific beneficial effects are as follows:

[0099] First, by setting the first valve 60 and the second valve 70 on the energy release pipeline, the heat exchanger 46 in the expansion branch 30 and the corresponding pipe systems at both ends can form a closed pipe section. When the system is restarted, the heat exchanger 46 and the corresponding pipe systems at both ends can reach or approach the rated working pressure in advance, thereby shortening the pipe system pressure rise time and quickly meeting the startup conditions.

[0100] Secondly, by setting up the air supply branch and the heat supply branch 50, the air intake flow of the air expansion unit 31 can be quickly increased without exceeding the inherent heating rate of the pipe system and the equipment structure, so that it has the ability to start quickly or increase load.

[0101] Furthermore, by setting up the air supply branch and the heat supply branch 50, the compression side heat exchanger equipment can be effectively utilized, while keeping the rated working load of the expansion branch 30 and the heat recovery branch unchanged, so as to avoid deviation from the design working conditions under normal working conditions and causing a decrease in working efficiency.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A compressed air energy storage system, characterized in that: include: Gas storage device; A compression branch, used for compressing ambient air and storing it in the air storage device; an expansion branch, used for expanding the compressed gas stored in the gas storage device by heating, so as to drive the power generation equipment to generate electricity; The heat storage circuit is used to use the heat generated during the air compression process to heat the compressed air in the energy release stage. The heat storage circuit includes a cold storage device, a first circulation pump, a heat storage heat exchanger, a heat storage device, a second circulation pump and a heat recovery heat exchanger connected end to end in sequence; the gas outlet of the heat storage heat exchanger is connected to the outlet of the gas storage device through a first pipeline, and the gas inlet of the heat storage heat exchanger is connected to the expansion branch through a second pipeline. A heat supply branch is connected to the heat storage heat exchanger.

2. The compressed air energy storage system according to claim 1, characterized in that: The heat supplement branch includes a third pipeline, a fourth pipeline and a fifth pipeline; The third pipeline is connected to the outlet of the heat storage device and the inlet of the first circulation pump; the fourth pipeline is connected to the outlet of the first circulation pump and the heat exchange medium outlet of the heat storage heat exchanger; the fifth pipeline is connected to the heat exchange medium inlet of the heat storage heat exchanger and the outlet of the cold storage device.

3. The compressed air energy storage system according to claim 1, characterized in that: Also included is a first valve and a second valve; The first valve is arranged on the pipeline between the outlet of the air storage device and the air inlet of the heat exchanger; the second valve is arranged on the pipeline between the air outlet of the heat exchanger and the expansion branch, and the first valve and the second valve are both used to control the opening and closing of the corresponding pipelines.

4. The compressed air energy storage system according to claim 3, characterized in that: The first valve is arranged near the outlet valve of the gas storage device or near the regenerative heat exchanger; And / or, the second valve is arranged at a position close to the main gas valve of the expansion unit in the expansion branch.

5. The compressed air energy storage system according to any one of claims 1 to 4, characterized in that: The compression branch includes a plurality of compressor groups, which are arranged in series or in parallel, and the heat storage heat exchanger is correspondingly provided at the air outlet of each compressor group; The compressor unit at the first stage is connected to the ambient air, and the compressor unit at the last stage is connected to the air inlet of the corresponding heat storage heat exchanger.

6. The compressed air energy storage system according to claim 5, characterized in that: It also includes a gas-liquid separator, which is connected to the pipeline between the air outlet of the heat storage heat exchanger and the inlet of the gas storage device, and is used to separate the gas-liquid mixture entering the gas-liquid separator and allow the air after the liquid component is separated to enter the gas storage device for storage.

7. The compressed air energy storage system according to any one of claims 1 to 4, characterized in that: The expansion branch includes a plurality of expansion units, which are arranged in series or in parallel, and the heat regenerator is correspondingly provided at the air outlet of each expansion unit; The expansion unit at the first stage is connected to the air outlet of the corresponding heat recovery heat exchanger and the second pipeline, and the expansion unit at the last stage is connected to the power generation equipment.

8. An operating method of a compressed air energy storage system according to any one of claims 1 to 7, characterized in that: The steps include: Determining whether the expansion branch in the compressed air energy storage system is being started for the first time or in a cold state, controlling the first valve to open for the first time, controlling the second valve to close, and injecting gas into the energy release pipeline including the expansion branch at a low pressure increase rate using the gas storage device; When it is determined that the pressure in the expansion branch and the pressure on the air side of the regenerative heat exchanger have reached the preset working pressure, the first valve is kept open, the second valve is controlled to open, and the main air valve of the expansion unit in the expansion branch is adjusted to start the expansion branch for the first time.

9. The method for operating a compressed air energy storage system according to claim 8, characterized in that: The operation method further comprises: When the expansion unit of the expansion branch needs to be shut down after the first startup, the main gas valve of the expansion unit is closed first, and then the first valve and the second valve are closed to seal the regenerative heat exchanger and part of the pipe system at both ends, so that the regenerative heat exchanger and part of the pipe system at both ends are maintained at a preset pressure, wherein the preset pressure is the intermediate pressure between the ambient pressure and the gas storage device.

10. The method for operating a compressed air energy storage system according to claim 8, characterized in that: The operation method further comprises: If a command is received from the power system requesting a rapid increase in the output power of the expansion branch, the compressed air released by the gas storage device is controlled to enter the gas outlet of the heat storage heat exchanger through the first pipeline, and then enter the heat storage heat exchanger through the heat replenishment branch for heat exchange, and then enter the second pipeline from the gas inlet of the heat storage heat exchanger, and replenish the expansion branch with air through the second pipeline; When it is determined that the output power of the expansion branch reaches the rated output power, the flow of the first pipeline is controlled to decrease, the flow of the heat supply branch is controlled to decrease; and the air flow and the flow of the heat exchange medium in the expansion branch are controlled to increase.

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