Energy-saving liquid gas energy storage system coupled with LNG (Liquefied Natural Gas) cold energy and power generation method

Abstract

The invention discloses an energy-saving liquid gas energy storage system coupled with LNG cold energy and a power generation method. The energy-saving liquid gas energy storage system comprises a compression system, a heat storage system, an LNG condensation system, a cold storage system and an expansion power generation system. The heat storage system comprises a cooler, a high-temperature heat storage tank, a heater and a low-temperature heat storage tank; the LNG condensation system comprises a condenser and an LNG storage tank, the cold accumulation system comprises a cold accumulator, the expansion power generation system comprises a liquid gas storage tank, a heat regenerator and a multi-stage turbine power generation device, through the structural design of the LNG condensation system, cold energy of an LNG gasification part is utilized, the cost of the gasification part is greatly reduced, and the energy consumption is reduced; the energy storage working medium pretreated by the cooler enters a first input end of the condenser, and just absorbs cold energy released by LNG gasification to realize condensation and liquefaction, so that the LNG gasification and the energy storage working medium are condensed and coupled by the condenser; cold energy released by LNG gasification is directly used for cooling and condensing the energy storage working medium to provide liquefaction cold energy, and the cold energy is the energy storage working medium pretreated by the cooler.

Description

Technical Field

[0001] This invention relates to technologies in the field of LNG energy conservation and energy storage, and in particular to an energy-saving liquid gas energy storage system and power generation method coupled with LNG cold energy. Background Technology

[0002] Liquid gas energy storage technology has become one of the key technologies for solving the problem of new energy consumption due to its advantages such as large energy storage capacity, flexible dispatch, and environmental protection without pollution. Its core principle is to use electric power to drive a compressor to pressurize and liquefy the energy storage medium (such as air or nitrogen) and store it. When releasing energy, the liquid medium is vaporized and expanded to drive a turbine to generate electricity.

[0003] Existing liquid gas energy storage systems suffer from two major pain points: First, the energy storage medium generates a large amount of compression heat during multi-stage compression. Directly releasing this heat would result in serious energy waste, while additional energy is required to heat the medium before it expands during the energy release phase, leading to low system energy efficiency. Second, the liquefaction process of the energy storage medium consumes a huge amount of cold energy. Traditional technologies often use electrically driven refrigeration units to provide the cooling capacity, which not only increases the system's operating costs but also further reduces the overall energy utilization efficiency. At the same time, LNG (liquefied natural gas) releases a large amount of high-quality cold energy during reception, storage, and gasification. Currently, this cold energy is mostly discharged directly through methods such as seawater heat exchange, which not only wastes energy but may also cause low-temperature shocks to the environment.

[0004] Therefore, a new technical solution needs to be researched to address the above problems. Summary of the Invention

[0005] In view of this, the present invention addresses the deficiencies of existing technologies, and its main objective is to provide an energy-saving liquid gas energy storage system and power generation method coupled with LNG cold energy. Through the structural design of the LNG condensation system, it utilizes the cold energy of the LNG vaporization section, significantly reducing the cost of the vaporization process. Furthermore, the second output port of the cooler is connected to the first input port of the condenser, the output port of the LNG storage tank is connected to the second input port of the condenser, and the output port of the condenser is connected to the first input port of the cold storage unit. Thus, the energy storage medium, pretreated by the cooler, enters the first input port of the condenser and precisely absorbs the cold energy released from LNG vaporization, achieving condensation and liquefaction. This couples LNG vaporization with the condensation of the energy storage medium. The cold energy released from LNG vaporization is directly used to cool and condense the energy storage medium, providing liquefaction cooling capacity. Since the energy storage medium is pretreated by the cooler, no additional electrically driven refrigeration unit is required. This fully utilizes the idle cold energy of LNG, reduces the energy consumption cost of energy storage medium liquefaction, minimizes the environmental impact of direct cold energy emissions, and achieves cascaded energy utilization.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An energy-saving liquid gas energy storage system coupled with LNG cold energy includes: A compression system, wherein the compression system is used to perform multi-stage pressurization of an energy storage working fluid at normal temperature and pressure; A heat storage system includes a cooler, a high-temperature heat storage tank, a heater, and a low-temperature heat storage tank. The cooler has a first output port and a second output port. The first input port of the cooler is connected to the output port of a compression system. The first output port of the cooler is connected to the high-temperature heat storage tank. The output port of the high-temperature heat storage tank is connected to the input port of the heater. The output port of the heater is connected to the input port of the low-temperature heat storage tank. The output port of the low-temperature heat storage tank is connected to the second input port of the cooler. An LNG condensation system includes a condenser, an LNG storage tank, and a cryogenic booster pump. The second output port of the condenser is connected to the first input port of the condenser, and the output port of the LNG storage tank is connected to the second input port of the condenser. The cryogenic booster pump is located between the output port of the condenser and the first input port of the cryogenic accumulator. A cold storage system, the cold storage system including a cold storage unit, wherein the output port of the condenser is connected to the first input port of the cold storage unit; An expansion power generation system includes a liquid gas storage tank, a regenerator, and a multi-stage turbine power generation device. The first output port of the cold accumulator is connected to the input port of the liquid gas storage tank, and the output port of the liquid gas storage tank is connected to the second input port of the cold accumulator. The second output port of the cold accumulator is connected to the first input port of the regenerator, the first output port of the regenerator is connected to the second input port of the heater, and the second output port of the heater is connected to the multi-stage turbine power generation device.

[0007] As a preferred embodiment, the thermal storage system further includes a high-temperature working fluid pump and a low-temperature working fluid pump. The high-temperature working fluid pump is connected to a high-temperature thermal storage tank and a heater at both ends, respectively. The low-temperature working fluid pump is connected to a low-temperature thermal storage tank and a cooler at both ends, respectively. The low-temperature working fluid pump can actively pump the low-temperature thermal storage working fluid in the low-temperature thermal storage tank into the cooler, ensuring sufficient heat exchange between it and the high-temperature energy storage working fluid, thereby improving the recovery efficiency of compression heat. Secondly, the high-temperature working fluid pump can stably pump the high-temperature thermal storage working fluid in the high-temperature thermal storage tank into the heater, ensuring the heating intensity and continuity of the energy storage working fluid during the energy release stage, avoiding uneven heating or insufficient heat supply caused by natural flow, thus improving the efficiency and stability of heat recovery and release.

[0008] As a preferred embodiment, the LNG condensation system also includes an LNG working fluid pump, which is located between the output end of the LNG storage tank and the second input end of the condenser. This pump actively and stably delivers the cryogenic LNG from the LNG storage tank to the condenser, avoiding flow fluctuations caused by gravity transport or insufficient pressure. This ensures a continuous and stable supply of cooling capacity within the condenser and improves the condensation efficiency of the energy storage medium. Secondly, a cryogenic booster pump is located between the condenser and the accumulator, pressurizing the liquid energy storage medium at the condenser outlet. This prevents transport stagnation due to insufficient pressure after condensation. Furthermore, the pressurized liquid medium is more easily subcooled within the accumulator, laying the foundation for pressure control during subsequent throttling storage and energy release stages.

[0009] As a preferred embodiment, a throttling valve is also provided between the first output port of the cold accumulator and the input port of the liquid gas storage tank. Through the precise throttling action of the throttling valve, the high-pressure liquid energy storage working fluid output by the cold accumulator can be stably depressurized and cooled to atmospheric pressure, ensuring that it is safely stored in the liquid gas storage tank in atmospheric pressure liquid form, avoiding overpressure of the storage tank or loss of working fluid vaporization due to pressure fluctuations; the cooling effect accompanying the throttling process can also further enhance the liquid stability of the working fluid, reduce the loss of cold energy during storage, and increase the energy storage density.

[0010] As a preferred embodiment, the expansion power generation system further includes an energy storage working fluid pump and a heat flow pump. The outlet of the liquid gas storage tank is connected to the inlet of the energy storage working fluid pump, and the outlet of the working fluid pump is connected to the second inlet of the cold accumulator. The outlet of the heat flow pump is connected to the second inlet of the regenerator. By connecting the liquid gas storage tank and the cold accumulator through the energy storage working fluid pump, the atmospheric pressure liquid energy storage working fluid in the liquid gas storage tank can be actively pressurized and sent to the cold accumulator, providing a higher pressure to the energy storage working fluid. At the same time, the pressurized working fluid can more fully recover the cooling energy within the cold accumulator (improving efficiency). The first step is to improve the efficiency of cooling energy utilization, which provides favorable conditions for subsequent gasification preheating. Secondly, the heat pump delivers a low-temperature heat source to the second inlet of the regenerator, ensuring that the regenerator can stably provide the heat required for gasification preheating of the liquid energy storage working fluid. This avoids problems such as incomplete gasification or low temperature of the working fluid due to insufficient heat source, laying the foundation for the heating of the subsequent heater and the efficient operation of the multi-stage turbine power generation device. The two work together to improve the power of working fluid transportation and the stability of heat source supply during the energy release stage, optimize the conversion efficiency of the working fluid from liquid to gas, and indirectly improve the power generation efficiency.

[0011] As a preferred embodiment, the energy storage medium is air, and the liquid gas storage tank is used to store atmospheric pressure liquid air.

[0012] An energy-saving liquid gas energy storage power generation method based on any one of the above-mentioned methods and coupled with LNG cold energy includes an energy storage stage and an energy release power generation stage, and the specific steps are as follows: Energy storage stage: a. Multi-stage compression: The energy storage medium at normal temperature and pressure is introduced into the compression system to increase the pressure. After pressurization, the temperature of the energy storage medium rises to 170℃. b. Heat storage and cooling: The high-temperature energy storage medium after pressurization in step a is passed into a cooling device to cool down and exchange heat with the low-temperature heat storage medium pumped from the low-temperature heat storage tank by the low-temperature section working medium pump, so that the working medium is cooled down and the heat storage medium is heated and stored in the high-temperature heat storage tank. c. LNG condensation: The cooled energy storage medium from step b is passed into a condenser for condensation. The cooled medium is then passed into the condenser to exchange cold energy with the LNG delivered by the LNG working medium pump, causing the working medium to condense and liquefy. d. Pressurized cold storage: The condensed liquid energy storage medium from step c is pressurized and heated by a cryogenic booster pump, and then subcooled by a cold accumulator. e. Throttling storage: The cooled liquid energy storage medium from step d is passed through a throttling valve to reduce its pressure and temperature to atmospheric pressure and stored in a liquid gas storage tank; Release energy generation stage: f. Pumping out for heating: The atmospheric pressure liquid energy storage medium in the liquid gas storage tank is pressurized by the energy storage medium pump and then sent to the cold accumulator to recover the cold energy; g. Regenerative vaporization: The liquid energy storage medium heated in step f is passed into a regenerator and preheated by vaporization using a low-temperature heat source; h. Heat storage and reheating: The energy storage medium after vaporization and preheating in step g is introduced into the heater, and at the same time, the heat storage medium in the high-temperature heat storage tank is sent into the heater through the high-temperature section working medium pump, and the heat of the energy storage medium is used to heat the energy storage medium. i. Turbine power generation: The high-pressure energy storage medium heated in step h is passed into a turbine expansion power generation device to generate electricity through expansion.

[0013] As a preferred option, the LNG in step c comes from an LNG storage tank.

[0014] Compared with the prior art, the present invention has significant advantages and beneficial effects. Specifically, as can be seen from the above technical solution, The main feature is the structural design of the LNG condensation system. Low-temperature LNG from the LNG storage tank enters the second input of the condenser, where it undergoes a vaporization reaction (LNG vaporization requires heat absorption, i.e., releasing cold energy). Utilizing the cold energy from the LNG vaporization process significantly reduces the cost of the vaporization phase. Furthermore, the second output of the cooler is connected to the first input of the condenser, the output of the LNG storage tank is connected to the second input of the condenser, and the output of the condenser is connected to the first input of the cold storage unit. Thus, the energy storage medium, pre-treated by the cooler (after compression and heating), enters the first input of the condenser, precisely absorbing the cold energy released from LNG vaporization to achieve condensation and liquefaction. This couples LNG vaporization with the condensation of the energy storage medium. The cold energy released from LNG vaporization is directly used to cool and condense the energy storage medium, providing liquefaction cooling capacity. Since the energy storage medium is pre-treated by the cooler, no additional electrically driven refrigeration unit is needed. This fully utilizes the idle cold energy of LNG, reduces the energy consumption cost of energy storage medium liquefaction, minimizes the environmental impact of direct cold energy emissions, and achieves cascaded energy utilization. Next, the first output port of the cold storage unit is connected to the input port of the liquid gas storage tank, and the output port of the liquid gas storage tank is connected to the second input port of the cold storage unit. The cryogenic booster pump is set between the output port of the condenser and the first input port of the cold storage unit, so that a cryogenic booster pump is added at the rear end of the condenser to increase the pressure and temperature of the stored gas. The pressure increased by the cryogenic booster pump replaces the pressurization of the compression system, which greatly reduces energy consumption. This allows the cold energy of the LNG vaporization part to be utilized, and the cryogenic booster pump can take on part of the pressurization task that was originally undertaken by the compression system, thereby greatly reducing the power consumption of the compression system. In addition, the cold storage unit stores the cold energy of the LNG condensation system, which can provide a stable cold source for the liquefaction of the energy storage medium when the LNG supply fluctuates; the heat storage system realizes the storage and release of compression heat through high and low temperature heat storage tanks, ensuring the continuity of the heating of the medium during the energy release stage. The dual-cycle design ensures the stability and efficiency of the energy storage and release process. Furthermore, the multi-stage heat exchange process, involving pre-cooling by the accumulator, heat exchange by the regenerator, and heating by the heater, optimizes the temperature gradient of the energy storage medium during the energy release stage, providing stable intake parameters for the multi-stage turbine power generation device. The multi-stage turbine power generation device can adapt to the energy gradient during the expansion process of the working medium, maximizing the conversion of expansion work into electrical energy, and further improving the system's power generation efficiency and overall energy efficiency.

[0015] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the connection structure and process flow according to an embodiment of the present invention.

[0017] Explanation of reference numerals in the attached diagram: 1. Compression system; 2.1. Cooler; 2.2. High-temperature heat storage tank; 2.3. High-temperature working fluid pump; 2.4. Heater; 2.5. Low-temperature heat storage tank; 2.6. Low-temperature working fluid pump; 3. Condenser; 4. LNG working fluid pump; 5. Low-temperature booster pump; 6. Cold accumulator; 7. Throttling valve; 8. Liquid gas storage tank; 9. Energy storage working fluid pump; 10. Regenerator; 11. Heat flow pump; 12. Expansion power generation system; 13. LNG storage tank. Detailed Implementation

[0018] Please refer to Figure 1 As shown, it illustrates the specific structure of an embodiment of the present invention.

[0019] In the description of this invention, it should be noted that the terms "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0020] An energy-saving liquid gas energy storage system coupled with LNG cold energy includes a compression system 1, a thermal storage system, an LNG condensation system, a cold storage system, and an expansion power generation system 12.

[0021] The compression system 1 is used to perform multi-stage pressurization of the energy storage medium at normal temperature and pressure; preferably, the energy storage medium is air, and the liquid gas storage tank 8 is used to store liquid air at normal pressure. The compression system 1 can adopt a four-stage compression device, which can be divided into four stages, for example: initial state: normal temperature and pressure air (temperature about 25°C) is used as the energy storage medium, and enters the compression system 1 during the off-peak electricity price period at night, first entering the first stage compressor; first stage compression and cooling; compression process: the first stage compressor performs initial pressurization on the air, raising the pressure to a preset value. Since the gas compression process is approximately adiabatic, the air temperature rises with the increase of pressure; Intercooling: The high-temperature compressed air immediately enters the first-stage intercooler (usually using heat transfer oil or molten salt as a heat storage medium) to exchange heat with the cooling medium, and the temperature drops to close to the initial ambient temperature, but the pressure remains basically unchanged; Second-stage compression and cooling: Compression process: Air cooled in the first stage enters the second-stage compressor, where the pressure is further increased and the temperature rises again; Intercooling: High-temperature air enters the second-stage intercooler and is cooled again to near room temperature, with the pressure maintained near the second-stage outlet pressure; Third-stage compression and cooling: Compression process: Air cooled in the second stage enters the third-stage compressor, where the pressure is increased to an even higher level; Intercooling: Air enters the third-stage intercooler and is cooled to prepare for the final stage compression. Through the gradual pressurization of the first three stages, the air pressure is brought close to the pre-treatment pressure required for the final stage, avoiding a surge in exhaust temperature (potentially exceeding the equipment's tolerance limit) and a sharp drop in volumetric efficiency (high gas density under high pressure reduces the compressor's intake volume) caused by excessively high compression ratios (excessive pressure ratios) in single-stage compression.

[0022] Fourth stage compression: Compression process: The air cooled by the third stage enters the fourth stage compressor to complete the final pressurization, so that the pressure reaches the target value of the system design, and the temperature rises to about 170°C. The high temperature and high pressure air after the fourth stage compression is output directly into the subsequent cooler 2.1 to exchange heat with the heat storage medium. The heat storage system includes a cooler 2.1, a high-temperature heat storage tank 2.2, a heater 2.4, and a low-temperature heat storage tank 2.5. The cooler 2.1 has a first output port and a second output port. The first input port of the cooler 2.1 is connected to the output port of the compression system 1. The first output port of the cooler 2.1 is connected to the high-temperature heat storage tank 2.2. The output port of the high-temperature heat storage tank 2.2 is connected to the input port of the heater 2.4. The output port of the heater 2.4 is connected to the input port of the low-temperature heat storage tank 2.5. The output port of the low-temperature heat storage tank 2.5 is connected to the second input port of the cooler 2.1. Preferably, the heat storage system further includes a high-temperature working fluid pump 2.3 and a low-temperature working fluid pump 2.6. The high-temperature working fluid pump 2.3 is connected at both ends to a high-temperature heat storage tank 2.2 and a heater 2.4, respectively. The low-temperature working fluid pump 2.6 is connected at both ends to a low-temperature heat storage tank 2.5 and a cooler 2.1, respectively. The low-temperature working fluid pump 2.6 can actively pump the low-temperature heat storage working fluid in the low-temperature heat storage tank 2.5 into the cooler 2.1, ensuring sufficient heat exchange between it and the high-temperature energy storage working fluid and improving the recovery efficiency of compression heat. Secondly, the high-temperature working fluid pump 2.3 can stably pump the high-temperature heat storage working fluid in the high-temperature heat storage tank 2.2 into the heater 2.4, ensuring the heating intensity and continuity of the energy storage working fluid during the energy release stage, avoiding uneven heating or insufficient heat supply caused by natural flow, thus improving the efficiency and stability of heat recovery and release.

[0023] The LNG condensation system includes a condenser 3 and an LNG storage tank 13. The second output port of the cooler 2.1 is connected to the first input port of the condenser 3, and the output port of the LNG storage tank 13 is connected to the second input port of the condenser 3. Preferably, the LNG condensation system further includes an LNG working fluid pump 4 and a cryogenic booster pump 5. The LNG working fluid pump 4 is located between the output end of the LNG storage tank 13 and the second input end of the condenser 3. The cryogenic booster pump 5 is located between the output port of the condenser 3 and the first input port of the accumulator 6. It can actively and stably transport the cryogenic LNG in the LNG storage tank 13 to the condenser 3, avoiding flow fluctuations caused by gravity transport or insufficient pressure, ensuring a continuous and stable supply of cooling capacity in the condenser 3, and improving the condensation efficiency of the energy storage working fluid. Secondly, the cryogenic booster pump 5 is located between the condenser 3 and the accumulator 6, which can pressurize the liquid energy storage working fluid at the outlet of the condenser 3, avoiding transport stagnation caused by insufficient pressure after condensation. At the same time, the pressurized liquid working fluid is more likely to achieve deep subcooling in the accumulator 6 (improving the liquefaction rate of the energy storage working fluid and improving the energy storage cycle efficiency), laying the foundation for pressure control in the subsequent throttling storage and energy release stages.

[0024] The cold storage system includes a cold storage unit 6, and the output port of the condenser 3 is connected to the first input port of the cold storage unit 6. Preferably, a throttling valve 7 is also provided between the first output port of the cold storage unit 6 and the input port of the liquid gas storage tank 8. Through the precise throttling action of the throttling valve 7, the high-pressure liquid energy storage working fluid output by the cold storage unit 6 can be stably depressurized and cooled to atmospheric pressure, ensuring that it is safely stored in the liquid gas storage tank 8 in atmospheric pressure liquid form, avoiding overpressure of the storage tank or loss of working fluid vaporization due to pressure fluctuations. The cooling effect accompanying the throttling process can further enhance the liquid stability of the working fluid, reduce the loss of cold energy during storage, and increase the energy storage density.

[0025] The expansion power generation system includes a liquid gas storage tank 8, a regenerator 10, and a multi-stage turbine power generation device. The first output port of the cold accumulator 6 is connected to the input port of the liquid gas storage tank 8, and the output port of the liquid gas storage tank 8 is connected to the second input port of the cold accumulator 6. The second output port of the cold accumulator 6 is connected to the first input port of the regenerator 10, the first output port of the regenerator 10 is connected to the second input port of the heater 2.4, and the second output port of the heater 2.4 is connected to the multi-stage turbine power generation device.

[0026] Preferably, the expansion power generation system further includes an energy storage working fluid pump 9 and a heat flow pump 11. The outlet of the liquid gas storage tank 8 is connected to the inlet of the energy storage working fluid pump 9, and the outlet of the working fluid pump is connected to the second inlet of the cold accumulator 6. The outlet of the heat flow pump 11 is connected to the second inlet of the regenerator 10. By connecting the liquid gas storage tank 8 and the cold accumulator 6 through the energy storage working fluid pump 9, the atmospheric pressure liquid energy storage working fluid in the liquid gas storage tank 8 can be actively pressurized and sent to the cold accumulator 6, providing a higher pressure to the energy storage working fluid. At the same time, the pressurized working fluid can more fully recover the cooling energy in the cold accumulator 6. (Improving cold energy utilization) provides favorable conditions for subsequent gasification preheating; secondly, the heat pump 11 delivers a low-temperature heat source to the second inlet of the regenerator 10, ensuring that the regenerator 10 can stably provide the heat required for gasification preheating of the liquid energy storage working fluid, avoiding the problem of incomplete gasification or low temperature of the working fluid due to insufficient heat source, laying the foundation for the heating of the subsequent heater 2.4 and the efficient work of the multi-stage turbine power generation device. The two work together to improve the power of the working fluid transport and the stability of the heat source supply during the energy release stage, optimize the conversion efficiency of the working fluid from liquid to gas, and indirectly improve the power generation efficiency.

[0027] A power generation method for energy-saving liquid gas energy storage coupled with LNG cold energy includes an energy storage stage and an energy release and power generation stage, the specific steps of which are as follows: Energy storage stage: a. Multi-stage compression: The energy storage medium at normal temperature and pressure is introduced into the compression system 1 for pressurization. After pressurization, the temperature of the energy storage medium rises to 170℃. b. Heat Storage and Cooling: The high-temperature energy storage medium pressurized in step a is passed into the cooler 2.1 to cool down, generally to about 45°C. It exchanges heat with the low-temperature heat storage medium pumped from the low-temperature heat storage tank 2.5 by the low-temperature section working medium pump 2.6, thus cooling the working medium. At the same time, the heat storage medium is heated and stored in the high-temperature heat storage tank 2.2. In the heat storage system, the heat storage medium, such as molten salt or heat transfer oil, is heated to about 152°C in the cooler 2.1. The high-temperature working medium is drawn from the low-temperature heat storage tank 2.5 by the low-temperature section working medium pump 2.6 and sent to the cooler 2.1. After being heated, it enters the high-temperature heat storage tank 2.2. c. LNG condensation: The cooled energy storage medium from step b is passed into condenser 3 for condensation, cooled to -140°C, and then passed into condenser 3 to exchange cold energy with the LNG delivered by LNG working medium pump 4, so that the working medium is condensed and liquefied; preferably, the LNG in step c comes from LNG storage tank 13; the LNG temperature needs to be below -145°C, and the LNG is drawn from LNG storage tank 13 of LNG receiving station by LNG working medium pump 4 and sent to condenser 3 to condense and liquefy the air.

[0028] d. Pressurized cold storage: The liquid energy storage medium condensed in step c is pressurized and heated by a cryogenic booster pump 5, and then subcooled by a cold accumulator 6. e. Throttling storage: The liquid energy storage medium cooled in step d is passed through throttling valve 7 to reduce its pressure and temperature to atmospheric pressure and stored in liquid gas storage tank 8; the cold energy in the accumulator 6 is used to further cool it to -178°C, and then it enters throttling valve 7 to reduce its pressure and temperature to atmospheric pressure and is stored in liquid gas storage tank 8.

[0029] Release energy generation stage: f. Pumping out for heating: When the electricity price is low during the day, the discharge process begins; the atmospheric pressure liquid energy storage medium in the liquid gas storage tank 8 is pressurized by the energy storage medium pump 9 and then sent to the cold accumulator 6 to recover the cold energy. g. Regenerative Vaporization: The heated liquid energy storage medium from step f is introduced into the regenerator 10 for preheating via vaporization using a low-temperature heat source. The high-temperature cold energy in the cold storage unit 6 heats the atmospheric pressure liquid air to -135°C. This high-temperature liquid air then enters the regenerator 10 for vaporization and heating to 30°C. The heat source in the regenerator 10 is supplied by a heat pump 11, such as low-temperature hot water. Part of this heat source comes from seawater and excess heat in the thermal storage system, thus consuming the waste heat in the thermal storage system without requiring additional cooling to reduce the system's heat output.

[0030] h. Heat Storage and Reheating: The energy storage medium, which has been preheated by vaporization in step g, is introduced into the heater 2.4 and heated to 145°C. At the same time, the heat storage medium in the high-temperature heat storage tank 2.2 is sent to the heater 2.4 through the high-temperature section working medium pump 2.3, and the heat of the energy storage medium is used to heat up the energy storage medium. In the heat storage system, the heat storage medium, such as molten salt or heat transfer oil, is cooled to about 52°C in the heater 2.4. The high-temperature working medium is drawn from the high-temperature heat storage tank 2.2 by the high-temperature section working medium pump 2.3 and sent to the heater 2.4. After cooling, it enters the low-temperature heat storage tank 2.5.

[0031] i. Turbine Power Generation: The high-pressure energy storage medium heated in step h is fed into a turbine expansion power generation device for expansion and power generation. The turbine power generation system 12 can adopt a four-stage turbine expansion power generation device. The electricity generated during the day can be used for self-consumption, and the surplus electricity is supplied to the grid to support the grid's high load during the day. In the energy release stage, the energy storage medium (such as high-pressure air) heated by the heater 2.4 has a high pressure and temperature. After entering the four-stage turbine expansion power generation device, it can perform work step by step in the following steps: First stage turbine: The high-pressure and high-temperature medium expands for the first time; Inlet state: The high-pressure and high-temperature medium (75-80 atm, 150-170℃) from the heater 2.4 first enters the first stage turbine; Expansion process: The medium is accelerated in the first stage stationary blades, the pressure drops to 25-30 atm, the temperature drops to 80-100℃, the high-speed airflow impacts the moving blades, drives the turbine to rotate, and outputs mechanical work to drive the generator to generate electricity; Exhaust: The first stage exhaust still has a certain pressure. The working fluid undergoes secondary expansion in the second-stage turbine, receiving exhaust gas from the first stage (25-30 atm, 80-100℃). During expansion, the working fluid further expands in the second stage, reducing pressure to 8-10 atm and temperature to 30-50℃, again driving the moving blades to perform work. This utilizes the energy not fully released in the first stage, avoiding sudden pressure drops and energy waste caused by single-stage expansion. The working fluid undergoes tertiary expansion in the third-stage turbine, receiving exhaust gas from the second stage (5-8 atm, 30-50℃). During expansion, pressure drops to 2-3 atm and temperature to 0-20℃, continuing to perform work. The working fluid temperature in this stage is close to ambient temperature, and it can absorb residual heat from the environment (such as air and circulating water heat) through an intermediate heat exchanger, slightly increasing the intake temperature and improving the work output. The fourth-stage turbine: the low-pressure working fluid undergoes final expansion; intake state: receives exhaust gas from the third stage (2-3 atm, 0-20℃); expansion process: the working fluid expands to near atmospheric pressure (around 1 atm), performing its final work; exhaust gas utilization: the final exhaust gas can be introduced into the regenerator 10 to provide cooling for the preheating of the liquid working fluid vaporization during the energy release stage (recovering low-temperature waste heat and improving the overall system efficiency). When a single-stage turbine expands, the working fluid drops directly from high pressure to atmospheric pressure, which can lead to a drastic temperature difference due to the excessive expansion ratio, resulting in a large amount of energy being wasted as waste heat. The four-stage turbine, through staged expansion, evenly distributes the total expansion ratio across the four stages, controlling the expansion ratio of each stage within a reasonable range, making each stage's expansion process closer to isentropic expansion. The overall power generation efficiency is higher than that of a single-stage turbine, generating more electricity to support the high load on the power grid during the day. The design of the four-stage turbine expansion, with the first stage handling high pressure and the last stage handling low pressure, maximizes the utilization of stored heat, improving power generation and energy storage cycle efficiency. Stable output characteristics ensure a continuous supply of power for self-use and surplus power to the grid, which is especially suitable for the grid's requirements for power supply stability; the four-stage turbine distributes the total power to four stages, reducing the load on each stage of equipment, reducing wear and thermal stress, extending service life, and reducing system maintenance costs.

[0032] The main feature is the structural design of the LNG condensation system. Low-temperature LNG from the LNG storage tank enters the second input of the condenser, where it undergoes a vaporization reaction (LNG vaporization requires heat absorption, i.e., releasing cold energy). Utilizing the cold energy from the LNG vaporization process significantly reduces the cost of the vaporization phase. Furthermore, the second output of the cooler is connected to the first input of the condenser, the output of the LNG storage tank is connected to the second input of the condenser, and the output of the condenser is connected to the first input of the cold storage unit. Thus, the energy storage medium, pre-treated by the cooler (after compression and heating), enters the first input of the condenser, precisely absorbing the cold energy released from LNG vaporization to achieve condensation and liquefaction. This couples LNG vaporization with the condensation of the energy storage medium. The cold energy released from LNG vaporization is directly used to cool and condense the energy storage medium, providing liquefaction cooling capacity. Since the energy storage medium is pre-treated by the cooler, no additional electrically driven refrigeration unit is needed. This fully utilizes the idle cold energy of LNG, reduces the energy consumption cost of energy storage medium liquefaction, minimizes the environmental impact of direct cold energy emissions, and achieves cascaded energy utilization. Next, the first output port of the cold storage unit is connected to the input port of the liquid gas storage tank, and the output port of the liquid gas storage tank is connected to the second input port of the cold storage unit. The cryogenic booster pump is set between the output port of the condenser and the first input port of the cold storage unit, so that a cryogenic booster pump is added at the rear end of the condenser to increase the pressure and temperature of the stored gas. The pressure increased by the cryogenic booster pump replaces the pressurization of the compression system, which greatly reduces energy consumption. This allows the cold energy of the LNG vaporization part to be utilized, and the cryogenic booster pump can take on part of the pressurization task that was originally undertaken by the compression system, thereby greatly reducing the power consumption of the compression system. In addition, the cold storage unit stores the cold energy of the LNG condensation system, which can provide a stable cold source for the liquefaction of the energy storage medium when the LNG supply fluctuates; the heat storage system realizes the storage and release of compression heat through high and low temperature heat storage tanks, ensuring the continuity of the heating of the medium during the energy release stage. The dual-cycle design ensures the stability and efficiency of the energy storage and release process. Furthermore, the multi-stage heat exchange process, involving pre-cooling by the accumulator, heat exchange by the regenerator, and heating by the heater, optimizes the temperature gradient of the energy storage medium during the energy release stage, providing stable intake parameters for the multi-stage turbine power generation device. The multi-stage turbine power generation device can adapt to the energy gradient during the expansion process of the working medium, maximizing the conversion of expansion work into electrical energy, and further improving the system's power generation efficiency and overall energy efficiency.

[0033] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. An energy-saving liquid gas energy storage system coupled with LNG cold energy, characterized in that, Including: A compression system, wherein the compression system is used to perform multi-stage pressurization of an energy storage working fluid at normal temperature and pressure; A heat storage system includes a cooler, a high-temperature heat storage tank, a heater, and a low-temperature heat storage tank. The cooler has a first output port and a second output port. The first input port of the cooler is connected to the output port of a compression system. The first output port of the cooler is connected to the high-temperature heat storage tank. The output port of the high-temperature heat storage tank is connected to the input port of the heater. The output port of the heater is connected to the input port of the low-temperature heat storage tank. The output port of the low-temperature heat storage tank is connected to the second input port of the cooler. An LNG condensation system includes a condenser, an LNG storage tank, and a cryogenic booster pump. The second output port of the condenser is connected to the first input port of the condenser, and the output port of the LNG storage tank is connected to the second input port of the condenser. The cryogenic booster pump is located between the output port of the condenser and the first input port of the cryogenic accumulator. A cold storage system, the cold storage system including a cold storage unit, wherein the output port of the condenser is connected to the first input port of the cold storage unit; An expansion power generation system includes a liquid gas storage tank, a regenerator, and a multi-stage turbine power generation device. The first output port of the cold accumulator is connected to the input port of the liquid gas storage tank, and the output port of the liquid gas storage tank is connected to the second input port of the cold accumulator. The second output port of the cold accumulator is connected to the first input port of the regenerator, the first output port of the regenerator is connected to the second input port of the heater, and the second output port of the heater is connected to the multi-stage turbine power generation device.

2. The energy-saving liquid gas energy storage system coupled with LNG cold energy according to claim 1, characterized in that: The heat storage system also includes a high-temperature section working fluid pump and a low-temperature section working fluid pump; the two ends of the high-temperature section working fluid pump are respectively connected to a high-temperature heat storage tank and a heater; the two ends of the low-temperature section working fluid pump are respectively connected to a low-temperature heat storage tank and a cooler.

3. The energy-saving liquid gas energy storage system coupled with LNG cold energy according to claim 1, characterized in that: The LNG condensation system also includes an LNG working fluid pump, which is located between the output end of the LNG storage tank and the second input end of the condenser.

4. The energy-saving liquid gas energy storage system coupled with LNG cold energy according to claim 1, characterized in that: A throttling valve is also provided between the first output port of the cold accumulator and the input port of the liquid gas storage tank.

5. The energy-saving liquid gas energy storage system coupled with LNG cold energy according to claim 1, characterized in that: The expansion power generation system also includes an energy storage working fluid pump and a heat flow pump. The outlet of the liquid gas storage tank is connected to the inlet of the energy storage working fluid pump, and the outlet of the working fluid pump is connected to the second inlet of the cold storage device. The outlet of the heat pump is connected to the second inlet of the regenerator.

6. The energy-saving liquid gas energy storage system coupled with LNG cold energy according to claim 1, characterized in that: The energy storage medium is air, and the liquid gas storage tank is used to store atmospheric pressure liquid air.

7. A power generation method based on energy-saving liquid gas energy storage coupled with LNG cold energy according to any one of claims 1 to 6, characterized in that, It includes the energy storage stage and the energy release and power generation stage, and the specific steps are as follows: Energy storage stage: a. Multi-stage compression: The energy storage medium at normal temperature and pressure is introduced into the compression system to increase the pressure. After pressurization, the temperature of the energy storage medium rises to 170℃. b. Heat storage and cooling: The high-temperature energy storage medium after pressurization in step a is passed into a cooling device to cool down and exchange heat with the low-temperature heat storage medium pumped from the low-temperature heat storage tank by the low-temperature section working medium pump, so that the working medium is cooled down and the heat storage medium is heated and stored in the high-temperature heat storage tank. c. LNG condensation: The cooled energy storage medium from step b is passed into a condenser for condensation. The cooled medium is then passed into the condenser to exchange cold energy with the LNG delivered by the LNG working medium pump, causing the working medium to condense and liquefy. d. Pressurized cold storage: The condensed liquid energy storage medium from step c is pressurized and heated by a cryogenic booster pump, and then subcooled by a cold accumulator. e. Throttling storage: The cooled liquid energy storage medium from step d is passed through a throttling valve to reduce its pressure and temperature to atmospheric pressure and stored in a liquid gas storage tank; Release energy generation stage: f. Pumping out for heating: The atmospheric pressure liquid energy storage medium in the liquid gas storage tank is pressurized by the energy storage medium pump and then sent to the cold accumulator to recover the cold energy; g. Regenerative vaporization: The liquid energy storage medium heated in step f is passed into a regenerator and preheated by vaporization using a low-temperature heat source; h. Heat storage and reheating: The energy storage medium after vaporization and preheating in step g is introduced into the heater, and at the same time, the heat storage medium in the high-temperature heat storage tank is sent into the heater through the high-temperature section working medium pump, and the heat of the energy storage medium is used to heat the energy storage medium. i. Turbine power generation: The high-pressure energy storage medium heated in step h is passed into a turbine expansion power generation device to generate electricity through expansion.

8. The power generation method according to claim 7, characterized in that: In step c, the LNG comes from the LNG storage tank.

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