Liquid piston type isothermal compressed air energy storage system coupled with thermal power generating unit and operation method

Abstract

The invention provides a liquid piston type isothermal compressed air energy storage system coupled with a thermal power generating unit and an operation method, the liquid piston type isothermal compressed air energy storage system adopts a liquid piston isothermal compression technology, and a compressed air energy storage device is thermally coupled with a boiler water supply system, a condensed water system and a smoke exhaust system of the thermal power generating unit; in the compression stage, air is subjected to near-isothermal compression in the water-gas direct heat exchange environment through the liquid piston device, and heat generated in the compression process is recycled by a low-temperature heat source of the thermal power generating unit and used for preheating boiler feed water and heating condensed water. And in the energy releasing stage, high-pressure air released from the air storage tank is heated through flue gas at the tail of the boiler before expansion, the air expansion temperature is increased, then the expansion machine is driven to generate electricity, and deep cooperation with a thermal power generating unit thermodynamic system is achieved. The coupling system is provided with an intelligent control device, a compression energy storage mode or an expansion power generation mode is automatically switched according to unit loads and power grid dispatching instructions, and the operation flexibility and the thermoelectric conversion efficiency of the thermal power unit are improved while peak load shifting is conducted.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage technology and flexible regulation technology for thermal power generation, and particularly relates to a liquid piston-type isothermal compressed air energy storage system coupled with a thermal power unit and an operation method thereof, for improving the peak regulation capability and energy utilization efficiency of the thermal power unit. Background Art

[0002] With the continuous expansion of renewable energy generation integrated into the grid, power systems are placing higher demands on the peak-shaving and frequency-regulating capabilities of thermal power generators. However, due to their high inertia and operational constraints, traditional thermal power units face problems such as frequent starts and stops, reduced efficiency, and reduced equipment lifespan during deep peak-shaving operations. To meet the fluctuating and balancing needs of the grid load, there is an urgent need for an energy storage technology that can operate in conjunction with thermal power units to achieve peak-shaving and valley-filling and enhance unit operational flexibility. Compressed air energy storage is a physical energy storage method with the potential for large-scale, long-term energy storage.

[0003] Isothermal compressed air energy storage technology has been a hot topic of research in recent years. Its characteristic is to maintain the gas temperature as constant as possible during the compression and expansion process, thereby minimizing heat energy loss and improving the efficiency of the energy storage circuit.

[0004] However, there is currently a lack of a solution that deeply couples efficient compressed air energy storage with thermal power units, fully utilizing the electricity-to-heat conversion characteristics of compressed air energy storage while leveraging the thermal power unit's waste heat system to improve the efficiency of the energy storage cycle and the overall economic efficiency of the unit. In summary, existing technologies have the following shortcomings: traditional CAES is inefficient or requires fossil fuel combustion, and advanced AA-CAES systems are complex and expensive; simple thermal storage peak-shaving methods utilize waste heat but cannot provide additional power output; and thermal power units lack flexible adjustment methods that can be directly integrated with large-scale energy storage.

[0005] In response to the above problems, it is necessary to provide a new technical solution to organically combine the liquid piston isothermal compressed air energy storage system with the thermal power unit, so as to improve the efficiency of the energy storage system and the peak-shaving performance of the thermal power unit. Summary of the Invention

[0006] In response to the technical problems of insufficient peak-shaving capacity of existing thermal power units and the need to improve the efficiency of compressed air energy storage, the purpose of the present invention is to propose a liquid piston-type isothermal compressed air energy storage system and operation method coupled with a thermal power unit. The system aims to integrate the compressed air energy storage process with the water supply, condensate and steam extraction systems of the thermal power unit, while achieving near-isothermal compression / expansion of air and realizing bidirectional heat transfer between the thermal power unit and the liquid piston-type compressed air energy storage device, thereby significantly improving the energy storage cycle efficiency and the comprehensive thermoelectric performance of the thermal power unit.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A liquid piston type isothermal compressed air energy storage system coupled to a thermal power unit includes a liquid piston type compressed air energy storage device and a thermal power unit thermal system, the two being coupled via pipelines and a heat exchange device; the liquid piston type compressed air energy storage device includes a liquid piston device 1, an air pump 2, a hydraulic pump 3, a high-pressure air storage tank 4, a flow valve 5, a flue gas heat exchanger 6, an expander 7, a generator 8, a water storage tank 9, and a controller 10;

[0009] The thermal power unit thermal system includes conventional equipment boiler 11, feed water heater 12 and condensate heater 13; the control system 14 is used to coordinate the heat exchange and output of the liquid piston type compressed air energy storage device and the modified thermal power unit thermal system;

[0010] When storing gas, one end of the air pump 2 is connected to the atmospheric environment, and the other end is connected to the liquid piston device 1 through a gas pipeline, so as to pressurize the ambient air into the liquid piston device 1; one end of the hydraulic pump 3 is connected to purified water, and the other end is connected to the bottom of the liquid piston device 1, so as to pressurize the air filled in the liquid piston device 1; the pressurized air enters the high-pressure gas storage tank 4 for storage through the gas pipeline at the top of the liquid piston device 1, and the high-temperature purified water in the liquid piston device 1 enters the water storage tank 9 for thermal insulation storage through the liquid pipeline at the bottom of the liquid piston device 1; the air pump 2, the hydraulic pump 3, the flow valve 5, the flue gas heat exchanger 6, and the water storage tank 9 are all connected to the controller 10 through a control bus, so as to control the air intake of the air pump 2, the water intake of the hydraulic pump 3, the opening of the flow valve 5, the flue gas volume of the flue gas heat exchanger 6, and the water supply of the water storage tank 9;

[0011] When releasing energy, the flow valve 5 at the outlet of the high-pressure gas storage tank 4 opens, and the high-pressure air enters the flue gas heat exchanger 6 through the air pipeline to be heated, and then enters the expander 7 to perform work, and the generator 8 driven by the expander 7 generates electricity;

[0012] The outlet of the water storage tank 9 is connected to the feed water heater 12 and condensate heater 13 of the thermal system of the thermal power unit through a liquid pipeline, which is used to preheat the feed water and condensate;

[0013] The tail flue gas of the boiler 11 of the thermal system of the thermal power unit is connected to the flue gas heat exchanger 6 through the flue gas pipeline, which is used to improve the parameters of the compressed air at the inlet of the expander 7;

[0014] The control system 14 is connected to the DCS and controller 10 of the thermal system of the thermal power unit through a data bus, and is used to coordinate the operating status, load switching and thermal feedback operation of the liquid piston compressed air energy storage device and the thermal system of the thermal power unit.

[0015] During the energy storage stage, the air pump 2 inhales atmospheric compressed air, and through direct pressurization of the purified water in the liquid piston device 1, near-isothermal compression is achieved, and the compression heat enters the water storage tank 9 along with the liquid; during the energy release stage, the high-pressure air absorbs the heat of the flue gas at the tail of the boiler 11 through the flue gas heat exchanger 6 and then drives the expander 7 to generate electricity. At the same time, the hot water in the water storage tank 9 is supplied to the water heater 12 and the condensate heater 13, thereby realizing the deep coordinated operation of the heat-gas dual channels.

[0016] The liquid piston device 1 is a vertical cylindrical container with upper and lower passages. An air inlet pipe connected to the air pump 2 is provided at the top, and a purified water circulation pipeline connected to the hydraulic pump 3 and the water storage tank 9 at the bottom. After the air is fed into the liquid piston device 1 by the air pump 2, it is pushed up and compressed by the purified water from bottom to top, realizing direct water-air heat exchange. The compression process keeps the air temperature close to room temperature or a preset control temperature, significantly reducing the energy loss caused by adiabatic heating. The liquid piston device 1 is equipped with a temperature sensor and a pressure sensor, which provide real-time feedback of compression process parameters to the controller 10 for dynamically adjusting the water supply flow rate of the hydraulic pump 3 to achieve precise control of the compression pressure and compression temperature.

[0017] The control system 14 automatically adjusts the compression process based on external load scheduling requirements to achieve fast response and energy storage regulation with maximum efficiency.

[0018] The high-pressure air storage tank 4 is arranged upstream of the outlet air pipe of the liquid piston device 1 and has a pressure storage capacity of 10 MPa or above; the outlet of the air storage tank 4 is connected to a flow valve 5 for controlling the high-pressure air outlet rate and energy supply rhythm;

[0019] During the energy release process, high-pressure air is fed into the flue gas heat exchanger 6 through the flow valve 5, absorbing the low- and medium-grade heat carried by the exhaust gas drawn from the tail of the boiler 11, thereby heating the compressed air to a suitable expansion temperature and improving the intake parameters of the expander 7;

[0020] The internal structure of the flue gas heat exchanger 6 adopts corrugated tube bundles and fin-type enhanced heat exchange technology, has high-temperature corrosion resistance, can adapt to the flue gas temperature fluctuations of thermal power plants and ensure stable air outlet temperature; its inlet is equipped with a flue gas throttle valve and a temperature control device, and the amount of heat source introduced is adjusted through the controller 10.

[0021] The water storage tank 9 not only serves as a temporary storage unit for compression heat, but also serves as a source of heat supply medium to form a closed-loop heat exchange circuit with the thermal system of the thermal power unit; its outlet is connected to the feed water heater 12 and the condensate heater 13 through two liquid pipelines, respectively, to achieve temperature rise treatment of the boiler feed water and turbine condensate of the thermal power unit; the control system 14 can intelligently allocate the storage water heat supply according to the operating conditions of the thermal power unit (such as low load, start-stop switching, etc.) to ensure the stable thermal balance of the thermal power unit.

[0022] The operating method of the system, the control system 14 communicates and interacts with the DCS and controller 10 of the thermal system of the thermal power unit through the data bus, and has the functions of data collection, state judgment, strategy switching and fault protection;

[0023] In the compression energy storage mode, the control system 14 controls the air pump 2 and the hydraulic pump 3 to adjust the speed according to the optimal thermal efficiency, and coordinates the purified water circulation system to deliver the compression heat to the water storage tank 9 in a timely manner;

[0024] In the energy release mode, the control system automatically adjusts the opening of the flow valve 5 and the heat input of the flue gas heat exchanger 6 to achieve air heating to the optimal expansion efficiency point;

[0025] At the same time, the system can access AGC or frequency modulation signals to achieve rapid output adjustment capabilities under frequency fluctuations, meeting the primary and secondary frequency regulation requirements of the power grid.

[0026] The operating method is as follows:

[0027] During the low-load period at night, the system switches to energy storage mode; the air pump 2 draws in air at normal temperature and pressure from the external environment of the factory area, and enters the top of the liquid piston device 1 through the gas pipeline; while the air pump 2 delivers air, the hydraulic pump 3 simultaneously injects purified water into the piston chamber of the liquid piston device 1, forming a stable water-air interface; as the volume of the liquid increases, the compressed air is pressed against the top, and the pressure gradually increases; in this process, due to the direct contact between water and air, the heat released in the air is quickly absorbed by the purified water, achieving near-isothermal compression; the controller 10 receives data feedback from the pressure sensor and temperature sensor configured for the liquid piston device 1 in real time, and dynamically adjusts the air intake of the air pump 2 and the water output flow of the hydraulic pump 3, so that the compression process operates at a constant temperature, reducing energy consumption and minimizing adiabatic losses;

[0028] After compression is completed, the gas enters the high-pressure gas storage tank 4 through the gas outlet at the top of the liquid piston device 1 for storage; at the same time, the purified water heated in the liquid piston device 1 flows into the water storage tank 9 through the bottom pipe to collect and store the heat generated during the compression process. This heat is allocated to the water supply or condensate system of the thermal power unit during the system energy release or heat load peak period and used as a medium- and low-grade heat source;

[0029] During peak grid load periods, the system automatically switches to energy release mode. Control system 14 activates flow valve 5, slowly releasing air from high-pressure gas storage tank 4 at a set flow rate into downstream flue gas heat exchanger 6 and expander 7. Flue gas heat exchanger 6 uses exhaust gas from thermal power plant boiler 11 to heat high-pressure air, using heat from exhaust gas temperatures between 180°C and 250°C to heat the compressed air. After being heated by flue gas heat exchanger 6, the air is heated to a temperature of 170°C to 240°C and then fed into expander 7 via an insulated pipeline, driving generator 8 to generate electricity that is then fed into the plant grid or exported externally. Exhaust gas from expander 7 is further coupled to the plant heating system via a cooler or exhaust gas heat exchanger, improving the system's surplus energy utilization.

[0030] During the energy release process, the hot water in the water storage tank 9 is used as a low-temperature heat source and is transported to the feed water heater 12 and condensate heater 13 of the thermal system of the thermal power unit through two hot water pipes to increase the turbine return water temperature and improve the heat balance.

[0031] The stored water is used to regulate the flow rate through the variable frequency pump in the thermal system of the thermal power unit, and the heating power is precisely controlled through the original temperature control valve of the thermal system of the thermal power unit. This can not only partially replace the burden of the original extraction steam heating system of the thermal power unit, but also delay the fluctuation of the extraction point under low load of the thermal power unit, thereby improving the operational stability of the boiler system.

[0032] During the operation of the system, the control system 14 performs multiple functions: on the one hand, it is connected to the DCS system of the thermal system of the thermal power unit to realize signal communication and operation status linkage; on the other hand, it quickly switches between compression, energy release and standby modes according to the frequency regulation or load instructions issued by the dispatching center; the control strategy includes dynamic adjustment of air flow, switching of heat source paths, and optimization of water circulation pressure and flow, so that the system not only has primary response capabilities, but can also undertake some secondary frequency regulation tasks.

[0033] Compared with the existing technology, the present invention has significant advantages and technical effects: the isothermal compression and isothermal expansion of air are achieved through the liquid piston, which significantly reduces the power consumption in the compression process and the irreversible loss in the expansion process, and improves the energy storage-release cycle efficiency compared with conventional adiabatic compression; the low-grade waste heat of the thermal power unit is integrated into the energy storage process, the heat is recovered in the compression stage for feed water preheating, and the heat of steam extraction is borrowed in the expansion stage, thereby improving the comprehensive efficiency of the liquid piston type compressed air energy storage device and the thermal system of the thermal power unit and realizing the cascade utilization of energy; the energy storage absorbs the surplus electric energy during the off-peak period and assists the thermal power unit to complete the feed water heating, thereby reducing the minimum stable combustion load of the thermal power unit; the stored energy is released during the peak period to quickly increase the output, It is equivalent to adding a fast-response "virtual machine" to the thermal power unit, effectively smoothing out grid load fluctuations and reducing the number of deep starts and stops of thermal power units; the liquid piston compressed air energy storage device can complete the switch from charging to discharging mode within tens of seconds under the coordination of the control system, and has a certain follow-up frequency regulation capability, which can quickly respond to grid frequency and power instructions, and improve the dynamic support capability of the thermal power unit to the grid; the solution of the present invention has relatively small requirements for the transformation of thermal power units, mainly adding external energy storage devices and several heat exchange interfaces. The liquid piston compressed air energy storage device has a high degree of modularity and can be configured according to the scale of the thermal power unit. It is suitable for the flexible transformation of various types of steam power units such as coal-fired and gas-fired.

[0034] In summary, the present invention achieves the goals of improving energy storage efficiency, reducing coal consumption of thermal power units, and enhancing the regulation capability of the power grid by innovatively combining liquid piston isothermal compressed air energy storage with the thermal system of a thermal power unit, and has good application prospects.

[0035] In summary, the present invention has the following advantages:

[0036] The system has good engineering adaptability and modular expansion capabilities. The liquid piston device 1 and the high-pressure gas storage tank 4 can be expanded and deployed according to the load level of the thermal power plant, and are suitable for the coordinated regulation of 300MW, 600MW and even 1000MW thermal power units; the system has a fast start and stop capability of ≤2min, an equivalent thermal efficiency of ≥70% and a response accuracy of ≥90%, and can realize the integration of multiple functions such as peak shaving and valley filling, black start assistance, AGC frequency regulation and compression heat heating, to build a comprehensive thermal power support platform integrating energy storage, heating and frequency regulation, which has broad promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a structural schematic diagram of a liquid piston type isothermal compressed air energy storage system coupled with a thermal power unit according to the present invention. DETAILED DESCRIPTION

[0038] The present invention provides a liquid piston-type isothermal compressed air energy storage system coupled to a thermal power unit and its operation method, aiming to fully utilize the low-grade heat source during the operation of the thermal power plant and the compression heat generated during the energy storage process, thereby achieving efficient energy recovery and deep synergy of the system.

[0039] The structure and operation process of the present invention are described in detail below with reference to specific embodiments:

[0040] This system retrofit was conducted on a 600MW subcritical coal-fired power unit. The original boiler employed a single-stage reheat configuration, equipped with a five-stage feedwater heater and condensate system. A liquid piston isothermal compressed air energy storage system was deployed within the plant, comprising a liquid piston device 1, an air pump 2, a hydraulic pump 3, a high-pressure air storage tank 4, a flow valve 5, a flue gas heat exchanger 6, an expander 7, a generator 8, a water storage tank 9, and a controller 10. Furthermore, the system was thermally coupled with the boiler 11, feedwater heater 12, and condensate heater 13 in the unit's thermal system, with coordinated regulation by a control system 14.

[0041] During the low load period at night, the system switches to energy storage mode. The air pump 2 draws air of normal temperature and pressure from the external environment of the plant and enters the top of the liquid piston device 1 through the gas pipeline. The device is a vertical cylindrical high-pressure closed container with a design working pressure of 10MPa and a volume of about 20m 3 Its lower part is connected to the hydraulic pump 3 through a liquid pipeline. The hydraulic pump draws purified water at room temperature from the water storage tank 9 and injects it into the liquid piston device 1 from bottom to top.

[0042] While the air pump 2 delivers air, the hydraulic pump 3 synchronously injects purified water into the piston chamber of the liquid piston device 1 to form a stable water-air interface. As the volume of the liquid increases, the compressed air is pressed against the top, and the pressure gradually increases. In this process, due to the direct contact between water and air, the heat released in the air is quickly absorbed by the purified water, achieving near-isothermal compression. The controller 10 receives data feedback from the pressure sensor and temperature sensor configured for the liquid piston device 1 in real time, and dynamically adjusts the air intake of the air pump 2 and the water outlet flow of the hydraulic pump 3, so that the compression process operates at a constant temperature (approximately 40-50°C), thereby effectively reducing energy consumption and reducing adiabatic losses.

[0043] After the compression is completed, the gas enters the high-pressure gas storage tank 4 through the gas outlet at the top of the liquid piston device 1 for storage. The gas storage tank is designed to have a working pressure of 10 MPa and a gas storage volume of 5000 Nm 3 , the inner wall is coated with anti-corrosion coating to extend the service life.

[0044] At the same time, the purified water heated in the liquid piston device 1 flows into the water storage tank 9 through the bottom pipe. The water storage tank is a double-layer insulation structure with a capacity of 300m 3The system is equipped with temperature monitoring and heat metering devices to collect and store the heat generated during the compression process. This heat can be allocated to the feedwater or condensate systems of thermal power units during periods of system energy release or peak heat load, serving as a low- to medium-grade heat source.

[0045] During the peak load period of the power grid, the system automatically switches to the energy release mode, and the control system 14 starts the flow valve 5, so that the air in the high-pressure gas storage tank 4 is slowly released at the set flow rate and enters the downstream flue gas heat exchanger 6 and expander 7.

[0046] High-pressure air enters the flue gas heat exchanger 6 through the air duct. This heat exchanger uses the exhaust flue gas from the thermal power plant boiler 11 to heat the high-pressure air, utilizing the heat from the exhaust gas, which is between 180°C and 250°C, to heat the compressed air. The flue gas heat exchanger 6 utilizes a stainless steel finned tube bundle structure, which enhances heat transfer and corrosion resistance, and provides high gas-to-gas convection heat transfer efficiency.

[0047] After passing through flue gas heat exchanger 6, the air is heated to a temperature of 170-240°C and then fed through an insulated pipeline into expander 7. This expander uses a high-speed radial turbine expansion mechanism, with a designed inlet temperature of 200°C, an atmospheric exhaust pressure, and a rated power of 1.5 MW. It drives generator 8 to generate electricity, which is then fed into the plant's power grid or transmitted externally.

[0048] The exhaust gas discharged by the expander 7 still has a certain temperature (about 80-120°C), which can be further coupled with the plant heating system through a cooler or tail gas heat exchanger to improve the utilization rate of the system's surplus energy.

[0049] During the energy release process, the hot water in the water storage tank 9 is used as a low-temperature heat source and is transported to the feed water heater 12 and condensate heater 13 of the thermal system of the thermal power unit through two hot water pipes to increase the turbine return water temperature and improve the thermal balance.

[0050] The stored water regulates the flow through the variable frequency pump in the thermal system of the thermal power unit, and accurately controls the heating power through the original temperature control valve of the thermal system of the thermal power unit. It can not only partially replace the burden of the original extraction steam heating system of the thermal power unit, but also delay the fluctuation of the extraction point under low load of the thermal power unit, thereby improving the operating stability of the boiler system.

[0051] In this system, control system 14 performs multiple functions: First, it connects to the DCS system of the thermal power unit's thermal system, enabling signal communication and operational status linkage; second, it rapidly switches between compression, energy release, and standby modes based on frequency regulation or load commands issued by the dispatch center. Control strategies include dynamic air flow adjustment, heat source path switching, and water circulation pressure and flow optimization. This ensures that the system not only has primary response capabilities but also can handle some secondary frequency regulation tasks.

[0052] In actual operation, the system can stably provide 1.5MW of rapid regulation capacity to alleviate peak load pressure on thermal power units and reduce the number of deep frequency modulations. The liquid piston isothermal compression process improves energy efficiency while significantly reducing disturbances to the thermal power unit's steam system. The thermal storage water supply path minimizes fluctuations in boiler inlet water temperature, effectively suppressing slagging and flue gas temperature differences during low-load periods.

[0053] This example system can provide a new direction for the future upgrade of auxiliary systems for large-capacity, low-energy thermal power plants. Especially in the context of frequent changes in source-grid-load coordination, this system has a high degree of regulatory flexibility and engineering promotion value.

Claims

1. A liquid piston isothermal compressed air energy storage system coupled with a thermal power unit, characterized in that: The invention comprises a liquid piston type compressed air energy storage device and a thermal power unit thermal system, which are coupled via a pipeline and a heat exchange device; the liquid piston type compressed air energy storage device comprises a liquid piston device (1), an air pump (2), a hydraulic pump (3), a high-pressure air storage tank (4), a flow valve (5), a flue gas heat exchanger (6), an expander (7), a generator (8), a water storage tank (9) and a controller (10); The thermal power unit thermal system includes a conventional equipment boiler (11), a feed water heater (12) and a condensate heater (13); the control system (14) is used to coordinate the heat exchange and output of the liquid piston type compressed air energy storage device and the modified thermal power unit thermal system; When storing gas, one end of the air pump (2) is connected to the atmospheric environment, and the other end is connected to the liquid piston device (1) through a gas pipeline, so as to pressurize the ambient air into the liquid piston device (1); one end of the hydraulic pump (3) is connected to purified water, and the other end is connected to the bottom of the liquid piston device (1), so as to pressurize the air filled in the liquid piston device (1); the pressurized air enters the high-pressure gas storage tank (4) through the gas pipeline at the top of the liquid piston device (1) for storage, and the high-temperature purified water in the liquid piston device (1) enters the water storage tank (9) through the liquid pipeline at the bottom of the liquid piston device (1) for heat preservation and storage; the air pump (2), the hydraulic pump (3), the flow valve (5), the flue gas heat exchanger (6), and the water storage tank (9) are all connected to the controller (10) through a control busbar, so as to control the air intake of the air pump (2), the water intake of the hydraulic pump (3), the opening of the flow valve (5), the flue gas volume of the flue gas heat exchanger (6), and the water supply of the water storage tank (9); When releasing energy, the flow valve (5) at the outlet of the high-pressure gas storage tank (4) is opened, and the high-pressure air enters the flue gas heat exchanger (6) through the air pipeline and is heated. Then, the high-pressure air enters the expander (7) to perform work, and the generator (8) driven by the expander (7) generates electricity; The outlet of the water storage tank (9) is connected to the feed water heater (12) and condensate heater (13) of the thermal system of the thermal power unit through a liquid pipeline, and is used to preheat the feed water and condensate; The tail flue gas of the boiler (11) of the thermal system of the thermal power unit is connected to the flue gas heat exchanger (6) through the flue gas pipeline, so as to improve the parameters of the compressed air at the inlet of the expander (7); The control system (14) is connected to the DCS and the controller (10) of the thermal system of the thermal power unit via a data bus, and is used to coordinate and adjust the operating status, load switching and thermal feedback operation of the liquid piston type compressed air energy storage device and the thermal system of the thermal power unit.

2. The system according to claim 1, wherein: During the energy storage stage, the air pump (2) inhales atmospheric compressed air, which is directly pressurized by the purified water in the liquid piston device (1) to achieve near-isothermal compression, and the compression heat enters the water storage tank (9) along with the liquid; during the energy release stage, the high-pressure air absorbs the heat of the flue gas at the tail of the boiler (11) through the flue gas heat exchanger (6) and heats up to drive the expander (7) to generate electricity, while the hot water in the water storage tank (9) is supplied to the water heater (12) and the condensate heater (13), thereby achieving deep coordinated operation of the heat-gas dual channel.

3. The system according to claim 1, wherein: The liquid piston device (1) is a vertical cylindrical container with upper and lower passages, with an air inlet pipe connected to an air pump (2) arranged at the top and a purified water circulation pipe connected to a hydraulic pump (3) and a water storage tank (9) at the bottom; after the air is fed into the liquid piston device (1) by the air pump (2), it is pushed up and compressed by the purified water from bottom to top, thereby realizing direct water-air heat exchange, and the air temperature is kept close to room temperature or a preset control temperature during the compression process, significantly reducing the energy loss caused by adiabatic heating; the liquid piston device (1) is equipped with a temperature sensor and a pressure sensor, which feed back compression process parameters to a controller (10) in real time, for dynamically adjusting the water supply flow rate of the hydraulic pump (3) to realize accurate control of the compression pressure and compression temperature; The control system (14) automatically adjusts the compression process based on external load scheduling requirements to achieve rapid response and energy storage regulation with maximum efficiency.

4. The system according to claim 1, wherein: The high-pressure air storage tank (4) is arranged upstream of the outlet air pipe of the liquid piston device (1) and has a pressure storage capacity of 10 MPa or above; the outlet of the air storage tank (4) is connected to a flow valve (5) for controlling the high-pressure air outlet rate and energy supply rhythm; During the energy release process, high-pressure air is fed into the flue gas heat exchanger (6) through the flow valve (5), absorbing the medium and low-grade heat carried by the exhaust gas drawn from the tail of the boiler (11), thereby heating the compressed air to a suitable expansion temperature and improving the intake parameters of the expander (7); The internal structure of the flue gas heat exchanger (6) adopts a corrugated tube bundle and fin-type enhanced heat exchange technology, has high temperature corrosion resistance, can adapt to the flue gas temperature fluctuation of the thermal power plant and ensure the stability of the air outlet temperature; its inlet is equipped with a flue gas throttle valve and a temperature control device, and the heat source introduction amount is adjusted through the controller (10).

5. The system according to claim 1, wherein: The water storage tank (9) not only serves as a temporary storage unit for compression heat, but also serves as a heat supply medium source to form a closed-loop heat exchange circuit with the thermal system of the thermal power unit; its outlet is connected to the feed water heater (12) and the condensate heater (13) respectively through two liquid pipelines, thereby achieving temperature rise treatment of the boiler feed water and turbine condensate of the thermal power unit; the control system (14) can intelligently allocate the storage water heat supply according to the operating conditions of the thermal power unit, thereby ensuring the stable thermal balance of the thermal power unit.

6. The method for operating the system according to any one of claims 1 to 5, characterized in that: The control system (14) communicates and interacts with the DCS and controller (10) of the thermal system of the thermal power unit via a data bus, and has functions of data collection, state identification, strategy switching and fault protection; In the compression energy storage mode, the control system (14) controls the air pump (2) and the hydraulic pump (3) to adjust the speed according to the optimal thermal efficiency, and coordinates the purified water circulation system to send the compression heat to the water storage tank (9) in time; In the energy release mode, the control system automatically adjusts the opening of the flow valve (5) and the heat input of the flue gas heat exchanger (6) to achieve air heating to the optimal expansion efficiency point; At the same time, the system can access AGC or frequency modulation signals to achieve rapid output adjustment capabilities under frequency fluctuations, meeting the primary and secondary frequency regulation requirements of the power grid.

7. The operating method according to claim 6, characterized in that: The details are as follows: During the nighttime low load period, the system switches to the energy storage mode; the air pump (2) draws in air at normal temperature and pressure from the external environment of the factory area, and enters the top of the liquid piston device (1) through the gas pipeline; while the air pump (2) delivers air, the hydraulic pump (3) simultaneously injects purified water into the piston chamber of the liquid piston device (1), forming a stable water-air interface; As the volume of the liquid increases, the compressed air is pushed up, and the pressure gradually increases. During this process, due to the direct contact between water and air, the heat released in the air is quickly absorbed by the purified water, achieving near-isothermal compression. The controller (10) receives data fed back by the pressure sensor and temperature sensor configured for the liquid piston device (1) in real time, and dynamically adjusts the air intake of the air pump (2) and the water output flow of the hydraulic pump (3), so that the compression process operates at a constant temperature, reducing energy consumption and reducing adiabatic loss. After the compression is completed, the gas enters the high-pressure gas storage tank (4) through the gas outlet at the top of the liquid piston device (1) for storage; at the same time, the purified water heated in the liquid piston device (1) flows into the water storage tank (9) through the bottom pipe to collect and store the heat generated during the compression process. This heat is allocated to the water supply or condensate system of the thermal power unit during the system energy release or heat load peak period and used as a medium- and low-grade heat source; During the peak load period of the power grid, the system automatically switches to the energy release mode, and the control system (14) starts the flow valve (5), so that the air in the high-pressure gas storage tank (4) is slowly released at the set flow rate and enters the downstream flue gas heat exchanger (6) and the expander (7); the flue gas heat exchanger (6) uses the tail flue gas of the thermal power plant boiler (11) to heat the high-pressure air, and uses the heat of the exhaust gas temperature in the range of 180 to 250°C to heat the compressed air; after the air is heated by the flue gas heat exchanger 6, the temperature rises to 170 to 240°C, and then is sent to the expander (7) through the insulated pipe, driving the generator (8) to generate electricity and be incorporated into the plant power grid or sent to the outside; the exhaust gas discharged by the expander (7) is further coupled with the plant heating system through the cooler or the tail gas heat exchanger, thereby improving the utilization rate of the system's surplus energy; During the energy release process, the hot water in the water storage tank (9) is used as a low-temperature heat source and is transported to the feed water heater (12) and condensate heater (13) of the thermal system of the thermal power unit through two hot water pipes, respectively, to increase the turbine return water temperature and improve the heat balance; The stored water is used to regulate the flow rate through the variable frequency pump in the thermal system of the thermal power unit, and the heating power is precisely controlled through the original temperature control valve of the thermal system of the thermal power unit. This can not only partially replace the burden of the original extraction steam heating system of the thermal power unit, but also delay the fluctuation of the extraction point under low load of the thermal power unit, thereby improving the operational stability of the boiler system. During the operation of the system, the control system (14) assumes multiple functions: on the one hand, it is connected to the DCS system of the thermal system of the thermal power unit to realize signal communication and operation status linkage; on the other hand, it quickly switches between compression, energy release and standby modes according to the frequency regulation or load instructions issued by the dispatching center; the control strategy includes dynamic adjustment of air flow, switching of heat source paths, and optimization of water circulation pressure and flow, so that the system not only has primary response capabilities, but also can undertake some secondary frequency regulation tasks.

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