Liquid air energy storage power generation system and automatic operation method thereof

Abstract

The liquid air energy storage power generation system comprises a liquid air storage tank, an evaporator, a heater, an expansion turbine and a controller, the evaporator, the heater, the expansion turbine and the controller are sequentially arranged behind the liquid air storage tank, and the expansion turbine is connected with a power generator through a coupler; a cold storage tank and a frequency conversion fan are arranged on a heat exchange pipeline of the evaporator; a variable-frequency low-temperature pump is arranged on a pipeline between the liquid air storage tank and the evaporator; the input ends of the variable-frequency low-temperature pump and the variable-frequency fan are respectively connected with the output end of the controller; a rotating speed transmitter used for monitoring the rotating speed of the generator is arranged on a coupler of the generator, and the output end of the rotating speed transmitter is connected with the input end of the controller. The outlet pressure of the heater is selected as the main gas pressure, fluctuation of the main gas pressure is reduced, the control valve and the temperature, pressure and flow measuring points are reasonably arranged, so that the power generation system has the potential of automatic operation, the reaction speed of the power generation system is increased, feedforward control is added, and automatic operation of the power generation system is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid air energy storage technology, and more specifically to a liquid air energy storage power generation system and an automatic operation method thereof. Background Art

[0002] Against the backdrop of the "dual carbon" initiative, my country's installed capacity of renewable energy, primarily photovoltaic and wind power, has surpassed its installed capacity of thermal power. The intermittent and unstable nature of renewable energy will also increase the pressure on large-scale grid connection and safe and stable operation, significantly limiting the large-scale application of renewable energy. Energy storage technology plays a key role in achieving widespread utilization of renewable energy and addressing its transient and unstable nature, as well as the mismatch between energy supply and demand. Large-scale energy storage technology is a key strategic focus of scientific and technological innovation worldwide and a key direction for achieving technological leadership.

[0003] Among the many energy storage technologies, pumped hydro, large-capacity battery storage, and compressed air storage are the main ones that can be deployed on a large scale. Pumped hydro relies on specific terrain, while compressed air storage requires integration with underground salt caverns or gas storage caverns, limiting their applicability. Large-capacity battery storage is subject to high costs, short cycle life, safety risks, and environmentally friendly recycling challenges. Liquid air storage, a key technology for compressed air storage, is a new large-scale grid energy storage technology. It offers significant advantages, including high energy storage density, geographically flexible site selection, high safety, and long lifespan. It can be widely used in renewable energy consumption, grid peak and frequency regulation, black start, distributed energy, and integrated energy services. Liquid air has a much higher density than compressed air, and its energy storage density (power generation per unit volume) is 15-20 times that of compressed air. It does not require specialized geographical conditions (salt caverns, artificial chambers, abandoned mines), nor does it require the use of numerous high-pressure vessels, resulting in a system with no safety issues. Due to its significant advantages, liquid air storage is expected to become one of the most promising new energy storage technologies.

[0004] Liquid air energy storage consists of a liquefaction system and a power generation system. The liquefaction system operates during the energy storage phase, and the power generation system operates during the energy release phase. The power generation system needs to respond to grid dispatch to adjust output in real time. Liquid air energy storage power generation systems have many devices with strong coupling between them, making the system difficult to operate. Relying on manual response to grid dispatch is labor-intensive and carries the risk of error. Response speed is a critical indicator of the power generation system, making automated operation an urgent need. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a liquid air energy storage power generation system and an automatic operation method thereof to solve the problems in the background technology.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0007] A liquid air energy storage and power generation system comprises a liquid air storage tank for storing liquid air during periods of low electricity consumption, and an evaporator arranged in sequence behind the liquid air storage tank for expanding the liquid air, a heater for heating the expanded air, an expansion turbine for using the high-temperature air to perform work, and a controller for controlling the operation of the system. The expansion turbine is connected to a generator for converting mechanical energy into electrical energy via a coupling. A cold storage tank and a variable frequency fan for sending relatively hot air into the evaporator to absorb cold energy and then store it in the cold storage tank are provided on the heat exchange pipeline of the evaporator. A variable frequency cryogenic pump for pressurizing the liquid air and sending it to the evaporator is provided on the pipeline between the liquid air storage tank and the evaporator. The input ends of the variable frequency cryogenic pump and the variable frequency fan are respectively connected to the output end of the controller. A speed transmitter for monitoring the speed of the generator is provided on the coupling of the generator. The output end of the speed transmitter is connected to the input end of the controller.

[0008] To further optimize the technical solution, the liquid air storage tank is provided with a liquid air storage tank outlet control valve for controlling the outflow and cutoff of liquid air, a low-temperature pump outlet control valve is provided on the pipeline at the rear end of the variable frequency low-temperature pump, a cold storage tank inlet control valve and a cold storage tank outlet control valve are respectively provided on the pipelines at the front and rear ends of the cold storage tank, an expansion turbine main valve is provided at the front end of the expansion turbine for controlling whether the working medium enters the expansion turbine, and a regulating valve is provided at the front end of the expansion turbine main valve for adjusting the system pressure, the input ends of the liquid air storage tank outlet control valve, the low-temperature pump outlet control valve, the cold storage tank inlet control valve, the cold storage tank outlet control valve, the expansion turbine main valve and the regulating valve are respectively connected to the output end of the controller.

[0009] To further optimize the technical solution, an expansion turbine regulating valve for regulating the amount of working medium entering the expansion turbine is provided on the pipeline between the expansion turbine main valve and the expansion turbine, and the input end of the expansion turbine regulating valve is connected to the output end of the controller.

[0010] To further optimize the technical solution, a cryogenic pump outlet pressure transmitter, a cryogenic pump outlet temperature transmitter and a cryogenic pump outlet flow transmitter for monitoring the pressure, temperature and flow information of the liquid air are provided on the pipeline between the variable frequency cryogenic pump and the evaporator; an evaporator outlet temperature transmitter and an evaporator outlet pressure transmitter for collecting evaporator outlet information are provided on the pipeline behind the evaporator; a heater outlet temperature transmitter and a heater outlet pressure transmitter for monitoring the heated air information are provided on the pipeline behind the heater; the output ends of the cryogenic pump outlet pressure transmitter, the cryogenic pump outlet temperature transmitter, the cryogenic pump outlet flow transmitter, the evaporator outlet temperature transmitter, the evaporator outlet pressure transmitter, the heater outlet temperature transmitter and the heater outlet pressure transmitter are respectively connected to the input ends of the controller.

[0011] To further optimize the technical solution, the outlet pipeline of the variable frequency fan is provided with a cold storage fan outlet pressure transmitter, a cold storage fan outlet temperature transmitter and a cold storage fan outlet flow transmitter for collecting the heat source information entering the evaporator, and the pipeline between the cold storage tank and the evaporator is provided with a cold storage tank inlet pressure transmitter and a cold storage tank inlet temperature transmitter for collecting the cooling information after heat exchange, and the output ends of the cold storage fan outlet pressure transmitter, the cold storage fan outlet temperature transmitter, the cold storage fan outlet flow transmitter, the cold storage tank inlet pressure transmitter and the cold storage tank inlet temperature transmitter are respectively connected to the input ends of the controller.

[0012] A method for automatically operating a liquid air energy storage power generation system is implemented based on a liquid air energy storage power generation system and includes the following steps: S1. Open the control valve between the variable frequency cryogenic pump and the expansion turbine to form a passage in the system, and set the pressure setpoint to prevent overpressure in the system. S2. After opening the control valve on the cold storage tank connecting pipe and the low-frequency start-up fan, open the outlet control valve of the liquid air storage tank to pre-cool the downstream; S3. Start the variable frequency cryogenic pump at a low frequency. After the cryogenic pump starts, adjust the expansion turbine regulating valve to enter the speed control mode, so that the expansion turbine starts to run until it is connected to the grid; S4. After grid connection, the variable frequency cryogenic pump, cold storage fan and expansion turbine regulating valve are put into automatic operation. According to the set power command, the power generation system enters the automatic operation state.

[0013] To further optimize the technical solution, in step S4, when the power generation system is automatically running, the variable frequency cryogenic pump, variable frequency fan and expansion turbine regulating valve work in coordination, and the system power setting is set manually or by specifying the grid AGC. The power setting will only take effect when the variable frequency cryogenic pump and the variable frequency fan are both put into automatic operation, otherwise the power command Pr tracks the actual power Pe of the generator; the variable frequency cryogenic pump frequency-controlledly adjusts the pressure of the power generation system according to different power setting values, and the variable frequency fan adjusts the frequency of the variable frequency fan according to the intermediate temperature of the evaporator cold flow; the expansion turbine regulating valve adjusts the valve opening according to the power setting value; the frequency of the variable frequency cryogenic pump and the frequency of the variable frequency fan are feedforward compensated by the power setting value to speed up the system response speed; the power setting value can be superimposed with frequency modulation correction to enable the power generation system to have a primary frequency modulation function.

[0014] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is as follows.

[0015] The present invention provides an automatic operation method for a liquid air energy storage power generation system. The method selects the outlet pressure of the heater as the main gas pressure, reducing main gas pressure fluctuations. By rationally setting control valves and temperature, pressure, and flow measurement points, the power generation system is endowed with the potential for automatic operation. To speed up the response of the power generation system, a variable-frequency cryogenic pump, a variable-frequency fan, and an expansion turbine regulating valve are added, with feedforward control targeting a power setpoint, thereby achieving automatic operation of the power generation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 This is a control principle diagram of the present invention.

[0017] Including: 1. Liquid air storage tank, 2. Liquid air storage tank outlet control valve, 3. Frequency conversion cryogenic pump, 4. Evaporator, 5. Cold storage tank, 6. Frequency conversion fan, 7. Cryogenic pump outlet control valve, 8. Cryogenic pump outlet pressure transmitter, 9. Cryogenic pump outlet temperature transmitter, 10. Cryogenic pump outlet flow transmitter, 11. Evaporator outlet temperature transmitter, 12. Evaporator outlet pressure transmitter, 13. Cold storage tank outlet control valve, 14. Cold storage tank inlet control valve, 15. Cold storage 16. Fan outlet pressure transmitter, 17. Cold storage fan outlet flow transmitter, 18. Cold storage tank inlet pressure transmitter, 19. Cold storage tank inlet temperature transmitter, 20. Heater, 21. Heater outlet temperature transmitter, 22. Heater outlet pressure transmitter, 23. Expansion turbine, 24. Expansion turbine main valve, 25. Expansion turbine regulating valve, 26. Control valve, 27. Generator, 28. Generator speed transmitter. DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] A liquid air energy storage power generation system, combined with Figure 1 As shown, it includes a liquid air storage tank 1, a variable frequency cryogenic pump 3, an evaporator 4, a cold storage tank 5, a variable frequency fan 6, a heater 20, an expansion turbine 23, a generator 27 and a controller, and the controller adopts a PID controller.

[0020] The liquid air storage tank 1 is used to store the liquid air stored by the liquid air energy storage liquefaction system during the low electricity consumption period. The liquid air storage tank 1 is provided with a liquid air storage tank liquid outlet control valve 2, which is used to control the outflow and cutoff of the liquid air. The input end of the liquid air storage tank liquid outlet control valve 2 is connected to the output end of the controller.

[0021] The variable frequency cryogenic pump 3 is arranged on the pipeline at the rear end of the liquid air storage tank 1, and a cryogenic pump outlet control valve 7 is provided on the pipeline at the rear end of the frequency converter. The outlet pipeline of the variable frequency cryogenic pump 3 is provided with a cryogenic pump outlet pressure transmitter 8, a cryogenic pump outlet temperature transmitter 9 and a cryogenic pump outlet flow transmitter 10, which are respectively used to monitor the pressure, temperature and flow information of the liquid air. The output ends of the cryogenic pump outlet pressure transmitter, the cryogenic pump outlet temperature transmitter and the cryogenic pump outlet flow transmitter are respectively connected to the input end of the controller, and the output end of the controller is respectively connected to the input end of the variable frequency cryogenic pump and the cryogenic pump outlet control valve.

[0022] The evaporator 4 is connected to the variable frequency cryogenic pump 3 to expand the liquid air. An evaporator outlet temperature transmitter 11 and an evaporator outlet pressure transmitter 12 are provided on the pipeline behind the evaporator 4 to collect the evaporator outlet temperature and pressure information. The output ends of the evaporator outlet temperature transmitter and the evaporator outlet pressure transmitter are respectively connected to the input ends of the controller.

[0023] The heater 20 is connected to the evaporator 4 and is used to heat the expanded air. A heater outlet temperature transmitter 21 and a heater outlet pressure transmitter 22 are provided on the pipeline behind the heater 20 to monitor the information of the heated air. The output ends of the heater outlet temperature transmitter and the heater outlet pressure transmitter are respectively connected to the input ends of the controller.

[0024] The expansion turbine 23 is arranged at the rear end of the heater 20 and uses the heated high-temperature air to perform work. The front end of the expansion turbine 23 is provided with an expansion turbine main valve 24 and an expansion turbine regulating valve 25. The expansion turbine main valve 24 is used to control whether the working medium enters the expansion turbine. The expansion turbine main valve performs a fast closing action in dangerous situations. The expansion turbine regulating valve 25 is used to adjust the amount of working medium entering the expansion turbine. The front end of the expansion turbine main valve 24 is provided with a regulating valve 26 for adjusting the system pressure to prevent the system from overpressure. The input ends of the expansion turbine main valve, the expansion turbine regulating valve and the regulating valve are respectively connected to the output end of the controller.

[0025] The generator 27 is arranged on the coupling of the expansion turbine 23 for converting mechanical energy into electrical energy. A speed transmitter 28 is arranged on the coupling for monitoring the speed of the generator. The output end of the speed transmitter is connected to the output end of the controller.

[0026] The cold storage tank 5 and the variable frequency fan 6 are arranged on the heat exchange pipeline of the evaporator 4 to provide a heat source for the evaporator and heat the low-temperature liquid air transported in the evaporator. The pipelines at the front and rear ends of the cold storage tank 5 are respectively provided with a cold storage tank inlet control valve 14 and a cold storage tank outlet control valve 13. The input ends of the cold storage tank inlet control valve and the cold storage tank outlet control valve are respectively connected to the output ends of the controller.

[0027] The outlet pipe of variable frequency fan 6 is equipped with a cold storage fan outlet pressure transmitter 15, a cold storage fan outlet temperature transmitter 16, and a cold storage fan outlet flow transmitter 17 to collect information about the heat source entering the evaporator. The pipe between cold storage tank 5 and evaporator 4 is equipped with a cold storage tank inlet pressure transmitter 18 and a cold storage tank inlet temperature transmitter 19 to collect information about the cooling capacity after heat exchange. The outputs of these cold storage fan outlet pressure transmitter, cold storage fan outlet temperature transmitter, cold storage fan outlet flow transmitter, cold storage tank inlet pressure transmitter, and cold storage tank inlet temperature transmitter are connected to the inputs of the controller. The variable frequency fan delivers relatively hot air into the evaporator, where it absorbs cooling energy, which is then stored in the cold storage tank. This cooling energy is then removed when the liquefaction system is operating.

[0028] A method for automatically operating a liquid air energy storage power generation system is implemented according to a liquid air energy storage method and includes the following steps: S1. Open the control valve between the variable frequency cryogenic pump and the expansion turbine to form a passage in the system, and set the pressure setpoint to prevent overpressure in the system. S2. After opening the control valve on the cold storage tank connecting pipe and the low-frequency start-up fan, open the outlet control valve of the liquid air storage tank to pre-cool the downstream; S3. Start the variable frequency cryogenic pump at a low frequency. After the cryogenic pump starts, adjust the expansion turbine regulating valve to enter the speed control mode, so that the expansion turbine starts to run until it is connected to the grid; S4. After grid connection, the variable frequency cryogenic pump, cold storage fan and expansion turbine regulating valve are put into automatic operation. According to the set power command, the power generation system enters the automatic operation state.

[0029] When the power generation system is running automatically, the variable frequency cryogenic pump, variable frequency fan and expansion turbine regulating valve work in coordination. The system power setpoint is set manually or by specifying the grid AGC. The power setpoint only works when the variable frequency cryogenic pump and variable frequency fan are both put into automatic operation. Otherwise, the power command Pr tracks the actual power Pe of the generator. The variable frequency cryogenic pump adjusts the pressure of the power generation system according to different power setpoints, and the variable frequency fan adjusts the frequency of the variable frequency fan according to the intermediate temperature of the evaporator cold flow. The expansion turbine regulating valve adjusts the valve opening according to the power setpoint. The frequency of the variable frequency cryogenic pump and the frequency of the variable frequency fan are feedforward compensated by the power setpoint to speed up the system response. The power setpoint can be superimposed with frequency modulation correction to give the power generation system a primary frequency modulation function.

[0030] The control principle diagram of the present invention is as follows: Figure 2As shown, the feedforward value of cryopump PU1 comes from the cryopump frequency function, which converts the power command Pr into the cryopump frequency and directly acts on cryopump PU1. The frequency feedforward value of fan FAN1 is generated by the fan frequency function, which converts the command Pr into the fan frequency and directly acts on fan FAN1. The set value of the cryopump PID control loop is generated by the main gas pressure function, which converts the command Pr into a main gas pressure set value and is automatically adjusted by the PID controller. The set value of the fan FAN1 control loop is generated by the temperature function, which converts the command Pr into a set value for the evaporator cold stream temperature and automatically adjusts the fan frequency by the controller. The fan frequency is not always in the automatic state and enters the automatic operation state when the temperature T2 is lower than a certain limit or the temperature change rate of temperature T2 is greater than a certain value. This control method connects the cryopump PU1, fan FAN1, and expansion turbine control valve V4 of the liquid air energy storage power generation system into an organic whole, uniformly serving the power command Pr, realizing the automatic operation of the liquid air energy storage power generation system and quickly tracking the power command.

Claims

1. A liquid air energy storage power generation system, characterized by: The system comprises a liquid air storage tank (1) for storing liquid air during a low electricity consumption period, an evaporator (4) arranged in sequence behind the liquid air storage tank (1) for expanding the liquid air, a heater (20) for heating the expanded air, an expansion turbine (23) for performing work on the high-temperature air, and a controller for controlling the operation of the system, wherein the expansion turbine (23) is connected to a generator (27) for converting mechanical energy into electrical energy via a coupling; a cold storage tank ( 5) and a variable frequency fan (6) for sending relatively hot air into the evaporator to absorb cold energy and then store it in the cold storage tank; a variable frequency cryogenic pump (3) for pressurizing and sending liquid air into the evaporator (4) is provided on the pipeline between the liquid air storage tank (1) and the evaporator (4), and the input ends of the variable frequency cryogenic pump and the variable frequency fan are respectively connected to the output end of the controller; a speed transmitter (28) for monitoring the speed of the generator is provided on the coupling of the generator (27), and the output end of the speed transmitter is connected to the input end of the controller.

2. A liquid air energy storage power generation system according to claim 1, characterized in that: The liquid air storage tank (1) is provided with a liquid air storage tank outlet control valve (2) for controlling the outflow and cutoff of liquid air, a low temperature pump outlet control valve (7) is provided on the pipeline at the rear end of the variable frequency low temperature pump (3), a cold storage tank inlet control valve (14) and a cold storage tank outlet control valve (13) are respectively provided on the pipelines at the front and rear ends of the cold storage tank (5), an expansion turbine main valve (24) is provided at the front end of the expansion turbine (23) for controlling whether the working medium enters the expansion turbine, and a regulating valve (26) is provided at the front end of the expansion turbine main valve (24) for adjusting the system pressure, and the input ends of the liquid air storage tank outlet control valve, the low temperature pump outlet control valve, the cold storage tank inlet control valve, the cold storage tank outlet control valve, the expansion turbine main valve and the regulating valve are respectively connected to the output end of the controller.

3. A liquid air energy storage power generation system according to claim 2, characterized in that: An expansion turbine regulating valve (25) for regulating the amount of working medium entering the expansion turbine is provided on the pipeline between the expansion turbine main valve (24) and the expansion turbine (23), and the input end of the expansion turbine regulating valve is connected to the output end of the controller.

4. The liquid air energy storage power generation system according to claim 1, characterized in that: A cryogenic pump outlet pressure transmitter (8), a cryogenic pump outlet temperature transmitter (9) and a cryogenic pump outlet flow transmitter (10) for monitoring the pressure, temperature and flow information of liquid air are provided on the pipeline between the variable frequency cryogenic pump (3) and the evaporator (4); an evaporator outlet temperature transmitter (11) and an evaporator outlet pressure transmitter (12) for collecting evaporator outlet information are provided on the pipeline behind the evaporator (4); a heater outlet temperature transmitter (21) and a heater outlet pressure transmitter (22) for monitoring heated air information are provided on the pipeline behind the heater (20); the output ends of the cryogenic pump outlet pressure transmitter, the cryogenic pump outlet temperature transmitter, the cryogenic pump outlet flow transmitter, the evaporator outlet temperature transmitter, the evaporator outlet pressure transmitter, the heater outlet temperature transmitter and the heater outlet pressure transmitter are respectively connected to the input end of the controller.

5. The liquid air energy storage power generation system according to claim 1, characterized in that: The outlet pipeline of the variable frequency fan (6) is provided with a cold storage fan outlet pressure transmitter (15), a cold storage fan outlet temperature transmitter (16), and a cold storage fan outlet flow transmitter (17) for collecting information on the heat source entering the evaporator. The pipeline between the cold storage tank (5) and the evaporator (4) is provided with a cold storage tank inlet pressure transmitter (18) and a cold storage tank inlet temperature transmitter (19) for collecting information on the cooling capacity after heat exchange. The output ends of the cold storage fan outlet pressure transmitter, the cold storage fan outlet temperature transmitter, the cold storage fan outlet flow transmitter, the cold storage tank inlet pressure transmitter, and the cold storage tank inlet temperature transmitter are respectively connected to the input end of the controller.

6. A method for automatically operating a liquid air energy storage power generation system, implemented based on a liquid air energy storage power generation system according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Open the control valve between the variable frequency cryogenic pump and the expansion turbine to form a passage in the system, and set the pressure setpoint to prevent overpressure in the system. S2. After opening the control valve on the cold storage tank connecting pipe and the low-frequency start-up fan, open the outlet control valve of the liquid air storage tank to pre-cool the downstream; S3. Start the variable frequency cryogenic pump at a low frequency. After the cryogenic pump starts, adjust the expansion turbine regulating valve to enter the speed control mode, so that the expansion turbine starts to run until it is connected to the grid; S4. After grid connection, the variable frequency cryogenic pump, cold storage fan and expansion turbine regulating valve are put into automatic operation. According to the set power command, the power generation system enters the automatic operation state.

7. The automatic operation method of the liquid air energy storage power generation system according to claim 6, characterized in that: In step S4, when the power generation system is automatically operating, the variable frequency cryogenic pump, the variable frequency fan, and the expansion turbine regulating valve work in coordination. The system power setting is set manually or by the grid AGC. The power setting takes effect only when the variable frequency cryogenic pump and the variable frequency fan are both in automatic operation. Otherwise, the power command Pr tracks the actual power Pe of the generator. The variable frequency cryogenic pump adjusts the pressure of the power generation system according to different power setting values, and the variable frequency fan adjusts its frequency according to the intermediate temperature of the evaporator cold stream. The expansion turbine regulating valve adjusts the valve opening according to the power set value; the frequency of the variable frequency cryogenic pump and the frequency of the variable frequency fan are feedforward compensated by the power set value to speed up the system response speed; the power set value can be superimposed with frequency regulation correction to enable the power generation system to have a primary frequency regulation function.

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