Liquid air energy storage and thermal power generating unit cooperative operation system and method

Abstract

The invention discloses a liquid air energy storage and thermal power generating unit cooperative operation system and method. The system comprises a liquefaction compressor, a liquid air storage tank, a regasifier, a heat exchanger, an expansion machine, a power generator, a cold energy recovery device, a control system and a thermal power generating unit. The liquefying compressor compresses and liquefies air and then stores the air in the liquid air storage tank when a power grid is in a low ebb, and cold energy generated in the liquefying process is recycled by the cold energy recycling device and used for a condensation water system or an independent cold storage system of the thermal power generating unit. When a power grid peak or frequency modulation is needed, liquid air is gasified through steam extraction or smoke heating of a steam turbine of the thermal power generating unit, the liquid air is further heated through the heat exchanger and then fed into the expansion machine to be expanded for power generation, and generated power is output in a grid-connected mode. And the control system is linked with a thermal power plant dispatching system to realize automatic start-stop and AGC frequency modulation response. Through efficient recovery of cold and heat energy and deep thermal-mechanical coupling of the thermal power generating unit, the peak regulation capacity and energy utilization efficiency of the thermal power generating unit are remarkably improved, and the method is suitable for operation optimization of a power system under high-proportion access of new energy.

Description

Technical Field

[0001] This invention belongs to the field of power system energy storage and dispatch technology, and more particularly relates to a system and method for the coordinated operation of a liquid air energy storage system (LAES) that is deeply coupled with a coal-fired power unit. The LAES system utilizes the liquefaction and vaporization processes of air to store and release energy. It uses conventional, industrially proven components and does not rely on specialized sites such as large geological storage tanks or reservoirs. It offers the advantages of large-capacity energy storage and flexible operation. Background Art

[0002] With the large-scale integration of intermittent renewable energy sources such as wind power and photovoltaics, the pressure on grid peak and frequency regulation continues to increase, necessitating enhanced flexibility in traditional coal-fired power plants to maintain stable grid operation. Existing large-scale energy storage technologies primarily include pumped hydro and compressed air storage. However, pumped hydro construction depends on geographical conditions and water resources, limiting site selection. Traditional compressed air storage requires high-tightness underground air storage chambers and suffers from low system efficiency. In contrast, liquefied air energy storage offers several advantageous properties: its working medium is air, which can be safely stored at atmospheric pressure, is not restricted by geographical conditions, and can be deployed in common plant areas. Furthermore, by recovering low-temperature cooling energy during the gasification stage and capturing waste heat during the liquefaction stage for reinjection during discharge, overall system efficiency can be further improved. Existing published technologies have proposed coupling LAES with thermal power plants, for example, by using cold and heat storage devices to form a closed-loop cooling and heating circuit to recycle cooling energy and waste heat. However, these solutions still struggle to achieve deep thermal coupling and automated scheduling between LAES systems and thermal power units.

[0003] In summary, a new system is urgently needed to achieve thermal and electrical coupling and flexible scheduling of LAES and thermal power units, so as to fully utilize the cold and hot energy in the liquefaction / vaporization process and improve power generation efficiency and scheduling flexibility. Summary of the Invention

[0004] In response to the problems in the above-mentioned background technology, the purpose of the present invention is to propose a system and method for the coordinated operation of liquid air energy storage and thermal power units, so as to improve the overall operating efficiency through deep thermal coupling and automated scheduling.

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

[0006] A system for coordinated operation of a liquid air energy storage and a thermal power unit includes: a liquefied air compressor 1, a liquid air storage tank 2, a regasifier 3, a heat exchanger 4, an expander 5, a generator 6, a cold energy recovery device 7, a control system 8, and a thermal power unit 9; wherein the liquefied air compressor 1, the liquid air storage tank 2, the regasifier 3, the heat exchanger 4, the expander 5, the generator 6, the cold energy recovery device 7, and the control system 8 constitute a liquid air energy storage subsystem;

[0007] During periods of low grid load, the liquefaction compressor 1 compresses and liquefies ambient air, which is then transferred to the liquid air storage tank 2 for storage. The liquid air storage tank 2 is connected to the outlet of the liquefaction compressor 1 and is used to store the liquid air. The regasifier 3 is connected to the steam extraction pipeline of the thermal power unit's steam turbine and / or the boiler flue gas heat exchanger to transfer waste heat from the unit's steam or flue gas to the liquid air for vaporization. The heat exchanger 4 connects the regasifier 3 and the expander 5 to perform multi-stage heating of the liquid air. The expander 5 is connected to the heat exchanger 4 to expand the high-pressure gas obtained by regasification to generate work, thereby driving the generator 6 for power generation and grid connection. The cold energy recovery device 7 is connected to the low-temperature side of the regasifier 3 to recover the cold energy generated during the liquefaction process and provide it to the condensate side of the thermal power unit 9 or the cold storage system. The control system 8 is connected to the load control system of the thermal power unit 9 and the grid frequency signal. It automatically controls the start and stop and operating parameters of the liquefaction compressor 1, regasifier 3, and expander 5 according to the grid load and frequency, achieving automatic peak and frequency regulation and coordinated heat and power scheduling of the system.

[0008] Air forms a closed-loop working medium in the system. After the liquefied air releases energy through the expander 5, its exhaust gas is cooled or heat-exchanged and then returns to the inlet of the liquefied compressor 1 to continue circulating.

[0009] The cold energy recovery device 7 includes a cold storage tank, which is connected to the low-temperature side heat exchange unit of the regasifier 3 and is connected to the condensate circuit or independent refrigeration system of the thermal power unit 9 through a heat exchange medium. It is used to transfer the cold recovered in the liquefaction process to the thermal power unit system to reduce the condensate temperature.

[0010] The regasifier 3 includes one or more heat exchange units connected to the steam extraction pipeline of the thermal power unit and / or the boiler flue gas heat exchanger, which is used to heat the liquid air with steam and / or flue gas; the heat exchanger 4 is a multi-stage heater before expansion, which is used to gradually increase the temperature and pressure of the vaporized air to meet the inlet conditions of the expander 5.

[0011] The control system 8 includes an automatic generation control (AGC) adjustment module and a peak-valley electricity price scheduling module, and is interconnected with the power grid and the thermal power plant scheduling system. It is used to automatically optimize the operation of the liquefaction compressor 1 and the expander 5 according to the AGC signal or the peak-valley price difference, implement automatic charging and discharging peak regulation, and perform heat and power coordinated operation together with the thermal power unit 9.

[0012] The system also includes a multi-stage reheater connected between the expander stages, which is used to heat and vaporize the liquid air step by step, thereby further improving the expansion efficiency and power output of the expander 5.

[0013] During periods of low grid load, the LAES system is activated for charging. Liquefaction compressor 1 compresses atmospheric-pressure air into liquefied liquid, which is then transferred to liquid air storage tank 2 for storage. Low-temperature cooling energy is released during the liquefaction process. Cold energy recovery device 7 recovers this cooling energy and injects it into the condensate side of thermal power unit 9 or into the cold storage system, improving the cooling efficiency of the thermal power unit's condenser. During peak grid load or periods requiring frequency modulation, the discharge mode is activated. Liquid air is transferred from liquid air storage tank 2 to regasifier 3, where it is heated and vaporized using steam extraction from the thermal power unit or waste heat from boiler flue gas (the heat further raises the working fluid temperature through heat exchanger 4). The high-temperature, high-pressure air is expanded by expander 5, generating work that drives generator 6 to generate electricity and feed the grid. Simultaneously, the thermal power unit reduces its output, and the energy storage system compensates for the load, achieving peak load substitution. Control system 8, linked to the thermal power plant's DCS and AGC systems, automatically controls the start / stop and output of compressor 1, regasifier 3, and expander 5 based on grid frequency and load signals, achieving automatic peak and frequency modulation and coordinated thermal power dispatch.

[0014] By recovering cold and injecting heat in the LAES cycle, the system significantly improves the condensation efficiency and overall energy utilization of thermal power units, while also enhancing scheduling flexibility. The system enables continuous operation during low-load phases without blindly reducing power, smoothing peak and valley loads through the energy storage system, thereby improving power plant safety and system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a structural diagram of the liquid air energy storage and thermal power unit coordinated operation system of the present invention. DETAILED DESCRIPTION

[0016] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. Figure 1The present invention provides a system for coordinated operation of liquid air energy storage and thermal power units, which consists of a liquid air energy storage subsystem and a thermal power unit subsystem. The liquid air energy storage subsystem is a closed cycle, including a liquefaction compressor 1, a liquid air storage tank 2, a regasifier 3, a heat exchanger 4, an expander 5, a generator 6, a cold energy recovery device 7 and a control system 8; wherein, the liquefaction compressor 1 is used to compress and liquefy air at room temperature, and the liquid air storage tank 2 is used to store liquid air; the regasifier 3 is connected to the steam extraction pipeline of the thermal power unit turbine and / or the boiler flue gas heat exchanger to transfer the waste heat of the unit steam and / or flue gas to the liquid air to vaporize it; the heat exchanger 4 is a multi-stage reheat heat exchanger. The expander 5 is connected to the generator 6 for expansion and power generation; the cold energy recovery device 7 is connected to the low-temperature side of the regasifier 3 for capturing the cold energy generated during the air liquefaction process and outputting it to the condensate circuit or cold storage system of the thermal power unit 9; the control system 8 is connected to the load control system of the thermal power unit 9 and the grid frequency signal, and automatically controls the start and stop and operating parameters of the liquefaction compressor 1, the regasifier 3 and the expander 5 according to the grid load and frequency, thereby realizing automatic peak and frequency regulation of the system and coordinated scheduling of heat and power.

[0017] Off-peak charging process: When the grid load is at a low point, control system 8 activates liquefaction compressor 1. Air is compressed in stages and cooled through intercoolers and expansion valves before being liquefied into liquid air, which is then transferred to liquid air storage tank 2 for storage. The low-temperature air generated during the liquefaction process is captured by cold energy recovery device 7 and fed through a heat exchanger to the condensate side of thermal power unit 9 or to a cold storage system, lowering the condensate temperature and improving the thermal efficiency of the thermal power unit. Excess cold air can be injected into liquid air storage tank 2 for backup.

[0018] Discharge during peak or frequency modulation periods: When the grid load reaches a peak or requires rapid regulation, control system 8 initiates discharge. Liquid air in liquid air storage tank 2 is pumped to regasifier 3, where it is heated and vaporized by heat exchange with the extraction steam or waste heat from the thermal power unit. The high-temperature, high-pressure air undergoes multi-stage heating in heat exchanger 4 before entering expander 5, where it drives generator 6 to generate power and be integrated into the grid. During this process, some heat carrier also enters the condenser of thermal power unit 9, absorbing waste heat. Simultaneously, the thermal power unit reduces its output according to control system 8, with the unloaded power being compensated by the liquid air energy storage subsystem, achieving a smooth transition from peak load.

[0019] Control and Coordination: Control system 8 is networked with the thermal power plant's Automatic Generation Control (AGC) system and dispatch system to collect real-time signals on grid frequency, load, and the operating status of the thermal power units. In charging mode, the control system operates liquefaction compressor 1; in discharging mode, control system 8 adjusts the operating parameters of regasifier 3 and expander 5. Using a preset strategy, control system 8 automatically implements charging and discharging peak shaving based on grid demand and coordinates the steam extraction and condensing circuits of thermal power unit 9 to achieve combined heat and power regulation. This control strategy ensures rapid response from the energy storage system and can be used for AGC frequency regulation and peak-valley-filling scheduling guided by peak-valley electricity prices.

[0020] In summary, the system and method for the coordinated operation of liquid air energy storage and thermal power units in this invention achieves the recycling of cooling and waste heat by deeply coupling the thermal cycle of the LAES with the thermal power units, and regulates peak and valley loads in the power grid through automated control. Compared with existing technologies, this system significantly improves the condensation efficiency of the thermal power units and the energy utilization rate of the energy storage system, enhancing the power plant's peak and frequency regulation capabilities, and providing a highly efficient and reliable technical means for the operation of a new generation of clean power grids.

Claims

1. A liquid air energy storage and thermal power unit coordinated operation system, characterized in that: include: A liquefied air compressor (1), a liquid air storage tank (2), a regasifier (3), a heat exchanger (4), an expander (5), a generator (6), a cold energy recovery device (7), a control system (8) and a thermal power unit (9); wherein the liquefied air compressor (1), the liquid air storage tank (2), the regasifier (3), the heat exchanger (4), the expander (5), the generator (6), the cold energy recovery device (7) and the control system (8) constitute a liquid air energy storage subsystem; The liquefaction compressor (1) compresses and liquefies ambient air during a period of low load on the power grid and then sends the compressed air to a liquid air storage tank (2) for storage; the liquid air storage tank (2) is connected to the outlet of the liquefaction compressor (1) and is used to store liquid air; the regasifier (3) is connected to the steam extraction pipeline of the thermal power unit steam turbine and / or the boiler flue gas heat exchanger to transfer the residual heat of the unit steam or flue gas to the liquid air for vaporization; the heat exchanger (4) is connected to the regasifier (3) and the expander (5) and is used to perform multi-stage heating on the liquid air; the expander (5) is connected to the heat exchanger (4) and is used to expand the high-pressure gas obtained by regasification to perform work to drive the generator (6) to generate electricity and connect to the grid; The cold energy recovery device (7) is connected to the low-temperature side of the regasifier (3) to recover the cold energy generated during the liquefaction process and provide it to the condensate side of the thermal power unit (9) or the cold storage system; the control system (8) is connected to the load control system of the thermal power unit (9) and the grid frequency signal, and automatically controls the start and stop and operating parameters of the liquefaction compressor (1), the regasifier (3) and the expander (5) according to the grid load and frequency, thereby realizing automatic peak and frequency regulation of the system and coordinated scheduling of heat and power.

2. The system according to claim 1, wherein: Air forms a closed-loop working medium in the system. After the liquefied air releases energy through the expander (5), its waste gas is cooled or heat-exchanged before returning to the inlet of the liquefied compressor (1) to continue circulating.

3. The system according to claim 1, wherein: The cold energy recovery device (7) includes a cold storage tank, which is connected to the low-temperature side heat exchange unit of the regasifier (3) and is connected to the condensate circuit or independent refrigeration system of the thermal power unit (9) through a heat exchange medium, and is used to transfer the cold recovered in the liquefaction process to the thermal power unit to reduce the condensate temperature.

4. The system according to claim 1, wherein: The regasifier 3 comprises one or more heat exchange units connected to the extraction steam pipeline of the thermal power unit and / or the boiler flue gas heat exchanger, for heating the liquid air with steam and / or flue gas; the heat exchanger (4) is a multi-stage heater before expansion, for gradually increasing the temperature and pressure of the vaporized air to meet the inlet conditions of the expander (5).

5. The system according to claim 1, wherein: The control system (8) includes an automatic power generation control (AGC) adjustment module and a peak-valley electricity price dispatching module, and is interconnected with the power grid and the thermal power plant dispatching system. It is used to automatically optimize the operation of the liquefaction compressor (1) and the expander (5) according to the AGC signal or the peak-valley price difference, implement automatic charging and discharging peak regulation, and perform heat and power coordinated operation together with the thermal power unit (9).

6. The system according to claim 1, wherein: It also includes a multi-stage reheater connected between the expander stages, which is used to heat and vaporize the liquid air step by step, thereby further improving the expansion efficiency and power output of the expander (5).

7. The system working method according to any one of claims 1 to 6, characterized in that: Charging process during off-peak period: When the grid load is at a low point, the control system (8) starts the liquefaction compressor (1), the air is compressed in stages and cooled by the intercooler and expansion valve to liquefy to obtain liquid air, which is then transported to the liquid air storage tank (2) for storage; the low-temperature air generated during the liquefaction process is captured by the cold energy recovery device (7), and is transported to the condensate water side of the thermal power unit (9) or the cold storage system through the heat exchanger to reduce the condensate temperature to improve the thermal efficiency of the thermal power unit; the excess cold energy is injected into the liquid air storage tank (2) for storage and standby; Discharge process during peak or frequency modulation period: When the grid load reaches a peak or needs to be adjusted quickly, the control system (8) starts discharging; the liquid air in the liquid air storage tank (2) is pumped to the regasifier (3), heated and vaporized by heat exchange with the exhaust steam or boiler flue gas waste heat of the thermal power unit, and the high-temperature and high-pressure air is heated in multiple stages by the heat exchanger (4) and then enters the expander (5) to drive the generator (6) to generate electricity and be integrated into the grid; during this process, part of the heat carrier enters the condenser of the thermal power unit (9) to absorb waste heat; at the same time, the thermal power unit reduces its own output according to the command of the control system (8), and the unloaded power is compensated by the liquid air energy storage subsystem to achieve a smooth transition of the peak load; Control and coordination: The control system (8) is connected to the AGC system and dispatching system of the thermal power plant to collect the grid frequency, load and thermal power unit operating status signals in real time; in the charging mode, the control system (8) enables the liquefaction compressor (1) to work; in the discharging mode, the control system (8) adjusts the operating parameters of the regasifier (3) and the expander (5); the control system (8) automatically completes the charging and discharging peak regulation according to the demand of the power grid, and coordinates the operation of the extraction steam and condensing circuits of the thermal power unit (9) to achieve heat and power co-regulation.

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