A liquefied air energy storage system coupled with LNG cold energy, ORC technology and natural heat source and its working method

Abstract

This invention belongs to the field of energy storage and utilization, specifically relating to a liquefied air energy storage system and its operating method that couples LNG cold energy, ORC technology, and natural heat sources. It includes an LNG vaporization subsystem, an air liquefaction subsystem, a liquefied air vaporization subsystem, and a solar heating subsystem. The LNG vaporization subsystem includes a connected propane cold storage cycle and a regenerative Rankine cycle. The air liquefaction subsystem includes a connected compression liquefaction unit and a liquefied air storage tank, with the compression liquefaction unit coupled to the propane cold storage cycle. The liquefied air vaporization subsystem includes a connected reheat Rankine cycle and an expansion work unit, with the reheat Rankine cycle connected to the liquefied air storage tank. The solar heating subsystem is connected to the regenerative Rankine cycle and the reheat Rankine cycle, providing a heat source for the heat exchangers in both cycles. Compared with existing technologies, this invention overcomes the shortcomings of large energy losses and low efficiency.

Description

Technical Field

[0001] This invention belongs to the field of energy storage and utilization, specifically relating to a liquefied air energy storage system and its working method that couples LNG cold energy, ORC technology and natural heat source. Background Technology

[0002] With the continuous improvement of socio-economic levels, the demand for electricity continues to increase, and renewable energy has gradually developed into a crucial part of the energy supply system. Due to the intermittency and volatility of renewable energy generation, as well as the fluctuations in electricity demand at the user end, energy storage technology is needed to store surplus electricity for energy supply and demand management. Liquefied air has advantages such as high energy density, long operating life, a solid industry foundation, no strict geographical limitations, and low investment costs, attracting increasing attention from scholars in this field.

[0003] The utilization of LNG's cold energy is a topic of extensive discussion and research in academia and industry. In long-distance transportation, liquefied natural gas (LNG) has a volume 600 times smaller than gaseous natural gas; liquefaction is crucial for more efficient storage and transportation. At coastal LNG receiving terminals, LNG is typically heated and vaporized before being transported to user networks in its ambient-temperature gaseous state for utilization. Vaporizing pure liquid methane at its standard boiling point (-162°C) into standard-state methane gas releases approximately 830 kJ / kg of cooling energy. Fully utilizing this cooling energy can further enhance energy conservation and emission reduction across the entire natural gas industry chain, while also bringing significant environmental and economic benefits.

[0004] However, conventional liquefied air energy storage systems currently consume a large amount of energy to compress air into a liquid state for storage, resulting in high compression power consumption, low practical efficiency, and a cycle efficiency of only 40-70%. Even though some studies have used LNG cold sources to improve system performance, LNG utilization efficiency remains low, failing to effectively address the problem of power supply and demand fluctuations, and the overall system's economy and flexibility are poor.

[0005] Chinese invention patent CN105863752A discloses a compressed air energy storage system utilizing the cold energy of liquefied natural gas (LNG). Air first exchanges heat with LNG in a heat exchanger unit, and the cooled air enters a compressor unit for compression. The compressed air is then stored in a gas storage device. When energy is released, the gas storage device outputs compressed air, which enters an expander unit to generate electricity. Interstage reheat is used to improve the overall system efficiency. However, the air in this system is still stored in a gaseous state, requiring high pressure resistance from the storage container, resulting in low energy density at low storage pressures.

[0006] Chinese invention patent CN113932564A discloses a liquefied air energy storage system using liquefied natural gas (LNG) for cold storage. In the energy storage stage, air passes through an air treatment unit and then enters a compression and refrigeration assembly where it is first pressurized and then expanded and cooled. The heat of compression is absorbed by the LNG. The expanded air then enters a gas-liquid separation assembly, where the cold energy of the gaseous air is reused, and the liquid air is stored in a tank. In the energy release stage, excess cold energy from the liquefied air is recovered using natural gas, and the cooled liquefied natural gas is used to lower the temperature of the compressed working fluid in the energy storage stage. The heated released air then passes through an expander unit to generate electricity. This system directly utilizes LNG for heat exchange with the compressed working fluid and natural gas for heat exchange with the liquefied air, which can lead to significant [potential issues]. The process suffers from losses, low liquefaction rate, excessive complexity, and its stability and reliability need further improvement.

[0007] Chinese invention patent CN112254561A discloses a liquid air energy storage system utilizing LNG cold energy and waste heat from gas peak-shaving power generation. This system couples a liquid air energy storage subsystem, a gas peak-shaving power generation system, and a steam cycle power generation system. In the liquid air energy storage subsystem, air is pre-cooled using the cooling capacity of liquefied natural gas. In the gas peak-shaving power generation system, the vaporized natural gas is directly combusted to generate electricity, and the waste heat from the combustion is used as a heat source for the Rankine cycle and the energy release phase of the liquid air energy storage subsystem. However, in the pre-cooler of this system, ambient temperature air directly exchanges heat with liquefied natural gas, which can cause significant heat loss. In addition to the low efficiency of waste heat utilization after combustion and the difficulty of operation and control, the low-grade cold energy of the working fluid in the liquefied air energy storage system will also result in a significant loss.

[0008] Chinese invention patent CN114810253A discloses a liquefied air energy storage system and its working method that utilizes the cold energy of LNG. Liquefied natural gas is heated and vaporized into natural gas by passing through an air liquefaction subsystem and a dual-pressure organic Rankine cycle subsystem. At the same time, ambient temperature and pressure air is cooled and liquefied into cryogenic liquid air by passing through the dual-pressure organic Rankine cycle subsystem and the air liquefaction subsystem and stored. When releasing energy, the liquid air is pressurized and enters the liquefied air vaporization subsystem, absorbs the stored heat, heats up, and then enters the expander to generate electricity. The heat exchange medium passes through the air liquefaction subsystem, the dual-pressure organic Rankine cycle subsystem, and the liquefied air vaporization subsystem in sequence to make full use of the surplus energy in the system. However, the overall heat exchange loss of the system is relatively large, the process is relatively complex, it lacks operational flexibility, and it is difficult to apply in practice.

[0009] US Patent No. US2019063685A1 discloses a system operation method based on a floating storage regasification power generation device that couples liquefied air energy storage and LNG gasification. The LNG gasification process is continuous and includes three parts: preheating, gasification, and superheating. During periods of low power demand, gaseous air is first pressurized by a compressor while recovering the heat of compression. Then, it exchanges heat with liquid LNG and is cooled to the -60°C to -80°C range before proceeding with the liquefaction process. During periods of high power demand, a semi-closed CO2 vapor bottom circulation is used to fully utilize the cold energy of the liquid air to improve system efficiency. Subsequently, the energy-releasing working fluid is heated and enters the expander to generate power. However, this system mainly uses the cold energy of LNG for the liquefaction stage, resulting in a still high exhaust temperature during compression, high compression power consumption, and a low liquefaction rate, leading to low overall system performance.

[0010] This shows that although scholars both domestically and internationally have attempted to improve liquefied air energy storage systems, most still face challenges. Given the significant losses and heat exchange losses in existing systems, resulting in low efficiency and consequently low overall performance, this invention addresses these shortcomings by providing a liquefied air energy storage system with high cycle efficiency and low energy loss. Summary of the Invention

[0011] The purpose of this invention is to provide a liquefied air energy storage system and its operating method that couples LNG cold energy, ORC technology and natural heat source to solve at least one of the above problems, so as to overcome the defects of large energy loss and low efficiency in the prior art, and achieve low energy loss, high cycle efficiency and operating efficiency.

[0012] The objective of this invention is achieved through the following technical solution:

[0013] The first aspect of this invention discloses a liquefied air energy storage system that couples LNG cold energy, ORC technology and natural heat source, including an LNG vaporization subsystem, an air liquefaction subsystem, a liquefied air vaporization subsystem and a solar heating subsystem;

[0014] The LNG vaporization subsystem includes a propane cold storage cycle and a regenerative Rankine cycle connected in sequence;

[0015] The air liquefaction subsystem includes a compressed liquefaction equipment group and a liquefied air storage tank connected in sequence, wherein the compressed liquefaction equipment group is coupled with a propane cold storage cycle;

[0016] The liquefied air vaporization subsystem includes a reheat Rankine cycle and an expansion work unit connected in sequence, wherein the reheat Rankine cycle is connected to the liquefied air storage tank.

[0017] The solar heating subsystem is connected to the regenerative Rankine cycle and the reheat Rankine cycle respectively. The heating medium of the solar heating subsystem is seawater, which provides a heat source for the heat exchangers in the regenerative Rankine cycle and the reheat Rankine cycle.

[0018] LNG is converted into NG after successive heat exchange through propane cold storage cycle or compression liquefaction equipment group and regenerative Rankine cycle; air is compressed and liquefied by compression liquefaction equipment group and stored in liquefied air storage tank; liquefied air is expanded and vaporized into air through reheat Rankine cycle and expansion work unit group.

[0019] Preferably, the propane cold storage cycle includes a propane storage tank #1, a propane storage tank #2, a centrifugal pump #2, a centrifugal pump #3, and a heat exchanger #1.

[0020] The No. 1 propane storage tank, the No. 2 centrifugal pump, the No. 1 heat exchanger, the No. 2 propane storage tank, the No. 3 centrifugal pump, and the compression liquefaction equipment group are connected in sequence, and the compression liquefaction equipment group is connected to the No. 1 propane storage tank to form a cycle;

[0021] The cold source of the No. 1 heat exchanger is LNG, and the heat source is the circulating medium of the propane cold storage cycle.

[0022] Preferably, the compression liquefaction equipment group includes several stages of multi-stream heat exchangers connected in series, and a compressor is connected between the heat outlet of the previous stage multi-stream heat exchanger and the heat inlet of the next stage multi-stream heat exchanger.

[0023] The heat source for the compressed air liquefaction unit is air, and the cold source is LNG and / or the circulating medium of the propane cold storage cycle. The high-grade refrigeration capacity of LNG and the cold energy of LNG recovered from propane are used to reduce the temperature of the air at the compressor outlet during the compressed air liquefaction process, which can significantly reduce the power consumption of the compressor and thus improve the operating efficiency of the system. The compressed air liquefaction unit brings the air at normal temperature and pressure to the critical point of air liquefaction before it enters the liquefied air storage tank for storage.

[0024] Preferably, the regenerative Rankine cycle includes a heat exchanger #2, a heat exchanger #3, a seawater heat exchanger, an expander, and a centrifugal pump #4.

[0025] The hot flow outlet of heat exchanger #2 is connected to the inlet of centrifugal pump #4, the outlet of centrifugal pump #4 is connected to the cold flow inlet of heat exchanger #3, the cold flow outlet of heat exchanger #3 is connected to the cold flow inlet of seawater heat exchanger, the cold flow outlet of seawater heat exchanger is connected to the inlet of expander, the outlet of expander is connected to the hot flow inlet of heat exchanger #3, and the hot flow outlet of heat exchanger #3 is connected to the hot flow inlet of heat exchanger #2, forming a cycle;

[0026] The heat source of the No. 2 heat exchanger is the circulating medium of the regenerative Rankine cycle, and the cold source is LNG; the heat source of the seawater heat exchanger comes from the solar heating subsystem, and the cold source is the circulating medium of the regenerative Rankine cycle.

[0027] In the regenerative Rankine cycle, the seawater heat exchanger has at least one stage, and each stage of seawater heat exchanger is connected to an expander, which outputs power.

[0028] Preferably, the circulating medium of the regenerative Rankine cycle is a hydrocarbon mixture, preferably a hydrocarbon mixture with a molar composition of 42.12 mol% ethane, 35.54 mol% propane, 13.32 mol% n-butane and 9.02 mol% isobutane.

[0029] Preferably, the reheat Rankine cycle includes a heat exchanger #4, a centrifugal pump #6, a seawater heat exchanger, and an expander;

[0030] The hot flow outlet of heat exchanger #4 is connected to the inlet of centrifugal pump #6, the outlet of centrifugal pump #6 is connected to the cold flow inlet of seawater heat exchanger, the cold flow outlet of seawater heat exchanger is connected to the inlet of expander, and the outlet of expander is connected to the hot flow inlet of heat exchanger #4, forming a cycle.

[0031] The heat source of the No. 4 heat exchanger is the circulating medium of the reheat Rankine cycle, and the cold source is liquefied air; the heat source of the seawater heat exchanger comes from the solar heating subsystem, and the cold source is the circulating medium of the reheat Rankine cycle.

[0032] In the reheat Rankine cycle, the seawater heat exchanger has at least one stage, and each stage of seawater heat exchanger is connected to an expander, which outputs power.

[0033] Preferably, the circulating medium of the reheat Rankine cycle is a hydrocarbon mixture, preferably a hydrocarbon mixture with a molar composition of 44.11 mol% ethane, 42.73 mol% propane, 6.52 mol% n-butane and 6.64 mol% isobutane.

[0034] Preferably, the expansion working device group includes several stages of seawater heat exchangers arranged in series, and an expander is connected after each stage of seawater heat exchanger.

[0035] The heat source for the expansion unit is a solar heating subsystem, and the cold source is liquefied air. Seawater heaters are used between the multi-stage expanders to achieve interstage reheat.

[0036] Preferably, the liquefied air energy storage system further includes a #1 centrifugal pump connected before the propane cold storage cycle, a #1 seawater heat exchanger connected after the regenerative Rankine cycle, a #5 centrifugal pump connected between the liquefied air storage tank and the regenerative Rankine cycle, and a #10 seawater heat exchanger connected after the expansion work unit.

[0037] The second aspect of this invention discloses a working mode of a liquefied air energy storage system that couples LNG cold energy, ORC technology, and natural heat sources as described above.

[0038] During off-peak electricity demand

[0039] LNG and / or propane cold storage cycles release heat to the compression liquefaction unit, compressing and liquefying ambient air into liquefied air and storing it in a liquefied air storage tank. Subsequently, LNG releases heat to the regenerative Rankine cycle and is converted into NG. At the same time, the expander in the regenerative Rankine cycle outputs power.

[0040] During peak electricity consumption periods

[0041] LNG releases heat into the propane cold storage cycle, storing cold energy within the cycle. Subsequently, the LNG releases heat into the regenerative Rankine cycle and converts it into NG. Simultaneously, the expander in the regenerative Rankine cycle outputs work.

[0042] The liquefied air stored in the liquefied air tank releases heat to the reheat Rankine cycle, causing the expander in the reheat Rankine cycle to output work. At the same time, the liquefied air is converted into low-temperature, high-pressure gaseous air. The low-temperature, high-pressure gaseous air then enters the expansion work unit to output work and is converted into air at normal temperature and pressure.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] This invention relates to a liquefied air energy storage system and its operating method that couples LNG cold energy, ORC technology and natural heat source. It combines the LNG vaporization process (LNG vaporization subsystem) and the liquefied air energy storage system (air liquefaction subsystem + liquefied air vaporization subsystem). The LNG vaporization process operates 24 hours a day to continuously output electricity, ensuring a continuous supply of natural gas to the user network. At the same time, it uses a cold storage device (propane cold storage cycle) to store LNG cold energy during peak electricity demand periods, ensuring system flexibility.

[0045] During off-peak hours, the air liquefaction subsystem uses the cold energy of LNG and the cold energy recovered from propane to obtain liquefied air. During peak hours, the surplus cold energy of liquefied air is used to generate electricity through ORC technology. Subsequently, the liquefied air vaporization subsystem uses the abundant solar energy resources in the coastal area to heat seawater (solar heating subsystem), which in turn generates electricity, playing a role in grid peak shaving management.

[0046] 1) Combining the cold energy released by the continuous vaporization of LNG around the clock with the energy storage system, the two different working modes achieved through the propane cold storage cycle at different time periods can ensure the flexibility of system operation and effectively cope with the problem of urban power grid load fluctuations. The high-grade cold energy of LNG is used to reduce the working temperature during the compression process, which significantly reduces the power consumption of the compressor and improves the operating efficiency of the system. The medium and low-grade cold energy of LNG is used for the regenerative Rankine cycle to realize the cascade utilization of LNG cold energy and reduce the energy loss during the vaporization and heating process.

[0047] 2) The reheat Rankine cycle is adopted to utilize the surplus cold energy of liquefied air, thereby improving the energy utilization rate of the system and increasing the power generation during the energy release stage. The abundant solar energy resources in the coastal area are used to heat the seawater, and the heated seawater is used as a heat source to heat the working fluid entering the expander to do work, thereby increasing the working capacity of the energy release working fluid and effectively improving the cycle efficiency of the energy storage system. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the liquefied air energy storage system of the present invention;

[0049] Figure 2 The temperature-entropy diagrams are for the air compression liquefaction process and the liquid air expansion vaporization process in Example 1.

[0050] In the diagram: 1101 - Liquefied air storage tank; 1201 - Propane storage tank #1; 1202 - Propane storage tank #2; 2101 - Heat exchanger #1; 2102 - Heat exchanger #2; 2103 - Heat exchanger #3; 2104 - Heat exchanger #4; 2201 - Seawater heat exchanger #1; 2202 - Seawater heat exchanger #2; 2203 - Seawater heat exchanger #3; 2204 - Seawater heat exchanger #4; 2205 - Seawater heat exchanger #5; 2206 - Seawater heat exchanger #6; 2207 - Seawater heat exchanger #7; 2208 - Seawater heat exchanger #8; 2209 - Seawater heat exchanger #9; 2210 - Seawater heat exchanger #10; 2301 - Multi-stream heat exchanger #1; 2302 - Multi-stream heat exchanger #2; 230 3-3# Multi-flow heat exchanger; 2304-4# Multi-flow heat exchanger; 2305-5# Multi-flow heat exchanger; 3001-1# Centrifugal pump; 3002-2# Centrifugal pump; 3003-3# Centrifugal pump; 3004-4# Centrifugal pump; 3005-5# Centrifugal pump; 3006-6# Centrifugal pump; 4001-1# Compressor; 4002-2# Compressor; 4003-3# Compressor; 4004-4# Compressor; 5001-1# Expander; 5002-2# Expander; 5003-3# Expander; 5004-4# Expander; 5005-5# Expander; 5006-6# Expander; 5007-7# Expander; 5008-8# Expander; 6- Solar collector. Detailed Implementation

[0051] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0052] Example 1

[0053] A liquefied air energy storage system that couples LNG cold energy, ORC technology, and natural heat sources, such as Figure 1 As shown, it includes an LNG vaporization subsystem, an air liquefaction subsystem, a liquefied air vaporization subsystem, and a solar heating subsystem;

[0054] The LNG vaporization subsystem includes a propane cold storage cycle and a regenerative Rankine cycle connected in sequence;

[0055] The air liquefaction subsystem includes a compressed liquefaction equipment group and a liquefied air storage tank 1101 connected in sequence, wherein the compressed liquefaction equipment group is coupled to a propane cold storage cycle;

[0056] The liquefied air vaporization subsystem includes a reheat Rankine cycle and an expansion work unit connected in sequence, wherein the reheat Rankine cycle is connected to the liquefied air storage tank 1101.

[0057] The solar heating subsystem is connected to the regenerative Rankine cycle and the reheat Rankine cycle respectively. The heating medium of the solar heating subsystem is seawater, which provides a heat source for the heat exchangers in the regenerative Rankine cycle and the reheat Rankine cycle.

[0058] LNG is converted into NG after sequential heat exchange through propane cold storage cycle or compression liquefaction equipment group and regenerative Rankine cycle; air is compressed and liquefied by compression liquefaction equipment group and stored in liquefied air storage tank 1101; liquefied air is expanded and vaporized into air through reheat Rankine cycle and expansion work equipment group.

[0059] The LNG vaporization system operates 24 / 7, with one end directly connected to the coastal LNG receiving terminal. The propane cold storage cycle and air liquefaction subsystem exchange heat with the LNG in shifts, absorbing energy. The heated LNG then exchanges heat with a regenerative Rankine cycle. The vaporized natural gas is connected to the user network, and the expander in the regenerative Rankine cycle continuously outputs electrical energy. The air liquefaction subsystem operates during off-peak hours (12 hours), with one end connected to ambient temperature and pressure air. After liquefying the air through heat exchange with the LNG and propane cold storage cycle, the liquefied air is stored in liquefied air storage tank 1101. The other end of liquefied air storage tank 1101 is connected to the liquefied air vaporization subsystem. During peak electricity consumption periods (12 hours), the liquefied air stored in the liquefied air storage tank 1101 exchanges heat with the reheat Rankine cycle, using the surplus cold energy to output electrical energy. Then, the solar heating subsystem heats the seawater, and the heated seawater is used as a heat exchange medium to heat the energy release medium in the liquefied air vaporization subsystem, outputting electrical energy while outputting atmospheric pressure air.

[0060] The solar heating subsystem mainly includes a solar collector 6, which collects solar energy to heat seawater, serving as the heat source for each seawater heat exchanger in the system. The solar collector 6 collects abundant solar energy resources from the coastal area, concentrating the dispersed solar energy into thermal energy to heat the seawater. The seawater heater in the liquefied air vaporization subsystem uses the heated seawater as a heat source to heat the energy release circulation medium, increasing the power generation capacity.

[0061] The propane cold storage cycle includes propane storage tank 1201, propane storage tank 1202, centrifugal pump 3002, centrifugal pump 3003, and heat exchanger 2101. These components are sequentially connected to a compression liquefaction unit, which is also connected to propane storage tank 1201, forming a cycle. The cold source for heat exchanger 2101 is LNG, and the heat source is the circulating medium (propane) of the propane cold storage cycle.

[0062] During peak electricity demand periods, centrifugal pump 3002 (#2) transports the high-temperature cold storage medium from high-temperature propane storage tank 1201 (#1) to heat exchanger 2101 (#1). After cooling by exchanging heat with LNG in heat exchanger 2101, the medium enters low-temperature propane storage tank 1202 (#2). During off-peak electricity demand periods, centrifugal pump 3003 (#3) transports the circulating medium from low-temperature propane storage tank 1202 (#2) through the compressed liquefaction equipment group in the air liquefaction subsystem. After providing cooling for compressed air liquefaction, the medium re-enters high-temperature propane storage tank 1201 (#1).

[0063] The regenerative Rankine cycle includes heat exchanger #2102, heat exchanger #3103, seawater heat exchanger #2202, seawater heat exchanger #3203, expander #1 5001, expander #2 5002, and centrifugal pump #4 3004. The hot flow outlet of heat exchanger #2102 is connected to the inlet of centrifugal pump #4 3004, the outlet of centrifugal pump #4 3004 is connected to the cold flow inlet of heat exchanger #3103, and the cold flow outlet of heat exchanger #3103 is connected to the inlet of seawater heat exchanger #2202. The cold flow inlet is connected, the cold flow outlet of seawater heat exchanger 2202 is connected to the inlet of expander 1 5001, the outlet of expander 1 5001 is connected to the cold flow inlet of seawater heat exchanger 3 2203, the cold flow outlet of seawater heat exchanger 3 2203 is connected to the inlet of expander 2 5002, the outlet of expander 2 5002 is connected to the hot flow inlet of heat exchanger 3 2103, and the hot flow outlet of heat exchanger 3 2103 is connected to the hot flow inlet of heat exchanger 2 2102, thus forming a loop. In this system, the heat source for heat exchanger #2 (2102) is the circulating medium of a regenerative Rankine cycle, and the cold source is LNG after heat exchange via a propane cold storage cycle. The heat sources for seawater heat exchangers #2 (2202) and #3 (2203) both come from the solar heating subsystem (seawater heated by solar collector 6), and the cold source is the circulating medium of a regenerative Rankine cycle. Power is output through expanders #1 (5001) and #2 (5002). The circulating medium of the regenerative Rankine cycle can be a hydrocarbon mixture, with the optimal molar composition being a mixture of 42.12 mol% ethane, 35.54 mol% propane, 13.32 mol% n-butane, and 9.02 mol% isobutane. The regenerative Rankine cycle utilizes the low-to-medium grade cold energy of LNG to generate electricity.

[0064] Centrifugal pump 3004 (#4) pressurizes the circulating medium of the regenerative Rankine cycle to the initial expansion pressure. Heat exchanger 2103 (#3) facilitates heat exchange between the expanded outlet circulating medium and the outlet circulating medium of centrifugal pump 3004, resulting in a pre-cooled, expanded gaseous circulating medium. Seawater heat exchanger 2202 (#2) further heats and vaporizes the preheated, low-temperature liquid circulating medium using seawater. The gaseous circulating medium then enters high-pressure expander 5001 (#1) to generate electricity. Reheating is achieved between the two expanders using seawater heat exchanger 2203 (#3), improving the working capacity of the circulating medium after the initial expansion, before it enters low-pressure expander 5002 (#2) to generate electricity. After expansion, the circulating medium is pre-cooled in heat exchanger 2103 (#3) before entering heat exchanger 2102 (#2) to exchange heat with LNG, reducing the heat loss in heat exchanger 2102. loss.

[0065] The compressed air liquefaction (CA) unit comprises five stages of multi-stream heat exchangers connected in series. A compressor connects the heat outlet of one stage's CA to the heat inlet of the next stage's CA. This means that air is pressurized and heated by the compressor between the two stages of the CA. The heat source for the CA is air, and the cold source is the circulating medium of the LNG and propane cold storage cycle. Specifically, as... Figure 1 As shown, ambient temperature and pressure air enters the #1 multi-stream heat exchanger 2301 and sequentially passes through the #1 compressor 4001, #2 multi-stream heat exchanger 2302, #2 compressor 4002, #3 multi-stream heat exchanger 2303, #3 compressor 4003, #4 multi-stream heat exchanger 2304, #4 compressor 4004, and #5 multi-stream heat exchanger 2305. After heat exchange and compression, the air reaches the critical point for liquefaction. The liquefied air is then sent to the liquefied air storage tank 1101 for storage. The circulating medium (propane) in the LNG and propane cold storage cycle exchanges heat with the air in a counter-current manner in each stage of the multi-stream heat exchanger. It is evident that the high-grade cooling capacity of LNG and the cold energy of LNG recovered from propane are used in the air compression and liquefaction process to reduce the temperature of the air at the compressor outlet, significantly reducing compressor power consumption and thus improving system operating efficiency.

[0066] The reheat Rankine cycle includes heat exchanger #4 (2104), centrifugal pump #6 (3006), seawater heat exchanger #4 (2204), seawater heat exchanger #5 (2205), expander #3 (5003), and expander #4 (5004). The hot flow outlet of heat exchanger #4 (2104) is connected to the inlet of centrifugal pump #6 (3006), and the outlet of centrifugal pump #6 (3006) is connected to the cold flow inlet of seawater heat exchanger #4 (2204). The cold flow outlet is connected to the inlet of expander #3 5003, the outlet of expander #3 5003 is connected to the cold flow inlet of seawater heat exchanger #5 2205, the cold flow outlet of seawater heat exchanger #5 2205 is connected to the inlet of expander #4 5004, and the outlet of expander #4 5004 is connected to the hot flow inlet of heat exchanger #4 2104, forming a cycle and outputting work through expanders #3 5003 and #4 5004. The heat source of heat exchanger #4 2104 is the circulating medium of the reheat Rankine cycle, and the cold source is liquefied air stored in liquefied air storage tank 1101; the heat source of the seawater heat exchanger comes from the solar heating subsystem (seawater heated by solar collector 6), and the cold source is the circulating medium of the reheat Rankine cycle. The reheat Rankine cycle can use a hydrocarbon mixture as the circulating medium, with the optimal molar composition being a mixture of 44.11 mol% ethane, 42.73 mol% propane, 6.52 mol% n-butane, and 6.64 mol% isobutane. The reheat Rankine cycle utilizes the cold energy of liquefied air to generate electricity.

[0067] Centrifugal pump 3006 (#6) is used to pressurize the circulating medium of the reheat Rankine cycle to the initial expansion pressure; seawater heat exchanger 2204 (#4) uses seawater to heat up and vaporize the pressurized low-temperature liquid circulating medium, and then the gaseous circulating medium enters the high-pressure expander 5003 (#3) to generate electricity; seawater heat exchanger 2205 (#5) is used between the two expanders for reheating to improve the working capacity of the circulating medium after the initial expansion before it enters the low-pressure expander 5004 (#4) to generate electricity; after expansion, the circulating medium enters heat exchanger 2104 (#4) to exchange heat with the air and cool down, absorbing excess cold energy.

[0068] The expansion power generation unit comprises four stages of seawater heat exchangers connected in series. Each stage is followed by an expander, employing interstage heating to enhance the expansion power generation capacity. The heat source for the expansion power generation unit is the solar heating subsystem (seawater heated by solar collector 6), and the cold source is liquefied air after reheating via a Rankine cycle. Specifically, as... Figure 1 As shown, the liquefied air that has completed heat exchange with heat exchanger 2104 (#4) enters seawater heat exchanger 2206 (#6), and then undergoes expansion and heat exchange in sequence through expander 5005 (#5), seawater heat exchanger 2207 (#7), expander 6 (#6), seawater heat exchanger 2208 (#8), expander 7 (#7), seawater heat exchanger 2209 (#9), and expander 8 (#8) to obtain atmospheric pressure low-temperature air. Expander 5005 (#5), expander 6 (#6), expander 7 (#7), and expander 8 (#8) output power to the outside.

[0069] In addition to the subsystems mentioned above, the liquefied air energy storage system also includes a #1 centrifugal pump 3001 connected before the propane cold storage cycle, a #1 seawater heat exchanger 2201 connected after the regenerative Rankine cycle, a #5 centrifugal pump 3005 connected between the liquefied air storage tank 1101 and the reheat Rankine cycle, and a #10 seawater heat exchanger 2210 connected after the expansion power unit. The #1 cryogenic centrifugal pump 3001 is used to raise the LNG from the LNG receiving terminal to a reasonable pipeline transport pressure, outputting high-pressure LNG; the #1 seawater heat exchanger 2201 heats the cryogenic natural gas to ambient temperature before inputting it into the user network; the #5 cryogenic centrifugal pump 3005 is used to increase the pressure of the liquefied air output from the liquefied air storage tank 1101 to a high-pressure state, thereby enhancing the power generation capacity of the circulating medium during the expansion and vaporization stage; the ambient-pressure cryogenic air is heated to ambient temperature by the #10 seawater heat exchanger 2210 and output as ambient-temperature, ambient-pressure air.

[0070] This embodiment further illustrates the method of the liquefied air energy storage system utilizing LNG cold energy, using a liquefied natural gas receiving station in a coastal area. The molar composition of the LNG used is 91.15% methane, 5.55% ethane, 2.16% propane, 0.51% n-butane, 0.51% isobutane, and 0.12% nitrogen. The temperature-entropy changes during the air compression liquefaction process and the liquid air (liquefied air) expansion vaporization process are as follows: Figure 2 As shown.

[0071] The above-described method for operating a liquefied air energy storage system that couples LNG cold energy, ORC, and natural heat sources includes the following steps:

[0072] 1) The LNG output from the coastal LNG receiving terminal is liquefied natural gas at a temperature of -162℃ and a pressure of 130kPa, with a flow rate of 3600kg / h. It is pressurized to 7MPa by the cryogenic centrifugal pump 3001 (which consumes 16.62kW of power), and then sequentially enters heat exchanger 2101, heat exchanger 2102, and seawater heat exchanger 2201 to be heated to 15℃ and 7MPa as gaseous natural gas, and then transported to the end user pipeline. During peak electricity consumption periods (12h), the temperature in the high-temperature propane storage tank 1201 is -54.74℃ and the pressure is 101. Propane at 3 kPa, the working fluid for cold storage, is cooled to -156℃ by centrifugal pump #2 (3002) and heat exchanger #1 (2101) before entering the low-temperature propane storage tank #2 (1202). During off-peak electricity hours (12 hours), propane at -156℃ and 101.3 kPa in the low-temperature propane storage tank #2 (1202) at a flow rate of 5000 kg / h passes sequentially through liquefaction heat exchangers #5 (2305), #4 (2304), #3 (2303), #2 (2302), and #1 (2301) to absorb heat and reach a temperature of -54.74℃ before entering the high-temperature propane storage tank #1 (1202). The alkyl storage tank 1201 stores the medium; the circulating medium of the regenerative Rankine cycle has a flow rate of 3169.1 kg / h. After passing through heat exchanger #2 2102, it absorbs the cold energy of LNG and cools down to -82.39℃ and 200 kPa. Then it enters centrifugal pump #4 3004 to pressurize to -82.24℃ and 600 kPa. Centrifugal pump #4 3004 consumes 0.64 kW. Then it passes through heat exchanger #3 2103 to pre-cool the circulating medium after expansion, raising the temperature to -20.26℃. Subsequently, it passes through seawater heat exchanger #2 2202, high-pressure expander #1 5001, and seawater heat exchanger #3 2202. Water heat exchanger 2203 and low-pressure expander 5002 expand and generate electricity, reducing the temperature to -3.50℃ and pressure to 200kPa. The total output power of the two-stage expander is 46.45kW. The circulating medium exits at 15℃ after passing through the seawater heater before entering the expander for expansion and work. Preheating before expansion improves the work-generating capacity. After expansion, the circulating medium enters heat exchanger 2103 to absorb the cold energy of the unused circulating medium and cool it to -27.24℃ before entering heat exchanger 2102. This reduces the direct heat exchange between the circulating medium and LNG in the regenerative Rankine cycle. loss.

[0073] 2) During off-peak electricity hours (12 hours), air from the external environment, pre-treated to a temperature of 25°C and a pressure of 101.3 kPa, with a flow rate of 3886 kg / h, is sequentially compressed, cooled, and liquefied to a temperature of -142.9°C and a pressure of 3.7 MPa by passing through heat exchangers 2301, 2302, 2303, 2304, 2304, and 2305. The air then enters the liquefied air storage tank 1101 for storage. The multi-stage compressor unit consumes 204.62 kW of power. The multi-stream heat exchangers use LNG cold energy and the cold energy recovered from propane as the cold storage medium to cool the stored air.

[0074] 3) During peak electricity consumption (12 hours), the liquefied air stored in liquefied air storage tank 1101 at a temperature of -142.9℃ and a pressure of 3.7MPa, with a flow rate of 3886kg / h, is pressurized by cryogenic centrifugal pump 3005 to become high-pressure air at a temperature of -111.3℃ and a pressure of 19.62MPa. The cryogenic centrifugal pump 3005 consumes 38.78kW of power. Subsequently, it passes through heat exchanger 2104 (4th heat exchanger), seawater heat exchanger 2206 (6th heat exchanger), expander 5005 (5th expansioner), and seawater heat exchanger 7th expansioner. Water heat exchanger 2207, #6 expander 5006, #8 seawater heat exchanger 2208, #7 expander 5007, #9 seawater heat exchanger 2209, #8 expander 5008, and #10 seawater heat exchanger 2210 heat and expand to air at 15℃ and 101.3kPa, which is then discharged into the external environment. The total output power of the multi-stage expanders is 380.4kW. The circulating medium flow rate of the reheat Rankine cycle is 1239kg / h. After passing through heat exchanger #4 2104, the cooling capacity of the liquid air is reduced. The water is initially at -73.99℃ and 200kPa, then pressurized by centrifugal pump #6 (3006) to -73.53℃ and 1300kPa. Centrifugal pump #6 (3006) consumes 0.71kW of power. The water then sequentially passes through seawater heat exchanger #4 (2204), high-pressure expander #3 (5003), seawater heat exchanger #5 (2205), and low-pressure expander #4 (5004), expanding and generating electricity until it reaches a temperature of 4.38℃ and a pressure of 200kPa. The total output from the two expanders... The output power is 33.23 kW. A seawater heater is used before the expander to increase the work capacity of the circulating medium and improve system operating efficiency. Solar collector 6 collects abundant solar energy resources from the coastal area to heat seawater. The heated seawater is used to heat the medium entering the expander in the liquefied air vaporization subsystem and the reheat Rankine cycle to do work. The temperature of the medium after passing through the seawater heater reaches 40°C before entering the expander for expansion and work. Preheating before expansion can improve the work capacity. The total heat flux reaches 2.43 × 10⁻⁶ kW. 6 kJ / h.

[0075] The LNG vaporization process is combined with the liquefied air energy storage system. The LNG vaporization process operates 24 hours a day to continuously output electricity, ensuring a continuous supply of natural gas to the user network. At the same time, the cold energy of LNG during peak electricity demand periods is stored using a cold storage device (propane cold storage cycle) to ensure system flexibility. During off-peak electricity demand periods, the air liquefaction subsystem uses the cold energy of LNG and the cold energy recovered from propane to obtain liquefied air. During this period, the electricity generated by LNG vaporization can be used for the air compression process. During peak electricity demand periods, the ORC uses the surplus cold energy of liquefied air to generate electricity. Subsequently, the liquefied air vaporization subsystem uses the abundant solar energy resources in the coastal area to heat seawater, thereby generating electricity and playing a role in grid peak shaving management.

[0076] At this liquefied natural gas receiving terminal, the regenerative Rankine cycle generates 46.45 kW of power, the liquefied air vaporization subsystem generates 413.63 kW of power, and the system's cycle efficiency is 229.91%. The efficiency is 84.65%.

[0077] In other embodiments, seawater heaters 2201 (No. 1), 2202 (No. 2), 2203 (No. 3), and 2210 (No. 10) can directly use seawater at room temperature as a heat source. This is because: for seawater heater 2201 (No. 1), only the NG products that have undergone regenerative Rankine cycle heat exchange and gasification need to be heated to near room temperature before entering the user's pipeline network; for seawater heaters 2202 (No. 2) and 2203 (No. 3), which belong to the LNG gasification process, considering their process independence and the small impact of temperature (15-40℃) on the work output, the seawater does not need to be heated before use; for seawater heater 2210 (No. 10), only the air after multi-stage expansion needs to be heated to near room temperature before being discharged into the ambient atmosphere; therefore, this part of the seawater heaters can use room temperature seawater as a heat source without needing to be heated by the solar heating subsystem.

[0078] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A liquefied air energy storage system coupling LNG cold energy, ORC technology, and natural heat source, characterized in that, It includes an LNG vaporization subsystem, an air liquefaction subsystem, a liquefied air vaporization subsystem, and a solar heating subsystem; The LNG vaporization subsystem includes a propane cold storage cycle and a regenerative Rankine cycle connected in sequence; The air liquefaction subsystem includes a compressed liquefaction equipment group and a liquefied air storage tank (1101) connected in sequence, wherein the compressed liquefaction equipment group is coupled to a propane cold storage cycle; The liquefied air vaporization subsystem includes a reheat Rankine cycle and an expansion work unit connected in sequence, wherein the reheat Rankine cycle is connected to the liquefied air storage tank (1101). The solar heating subsystem is connected to the regenerative Rankine cycle and the reheat Rankine cycle respectively. The heating medium of the solar heating subsystem is seawater, which provides a heat source for the heat exchangers in the regenerative Rankine cycle and the reheat Rankine cycle. The regenerative Rankine cycle includes heat exchanger #2 (2102), heat exchanger #3 (2103), seawater heat exchanger, expander and centrifugal pump #4 (3004). The hot flow outlet of heat exchanger #2 (2102) is connected to the inlet of centrifugal pump #4 (3004), the outlet of centrifugal pump #4 (3004) is connected to the cold flow inlet of heat exchanger #3 (2103), the cold flow outlet of heat exchanger #3 (2103) is connected to the cold flow inlet of seawater heat exchanger, the cold flow outlet of seawater heat exchanger is connected to the inlet of expander, the outlet of expander is connected to the hot flow inlet of heat exchanger #3 (2103), and the hot flow outlet of heat exchanger #3 (2103) is connected to the hot flow inlet of heat exchanger #2 (2102), thus forming a cycle; The heat source of the No. 2 heat exchanger (2102) is the circulating medium of the regenerative Rankine cycle, and the cold source is LNG; the heat source of the seawater heat exchanger comes from the solar heating subsystem, and the cold source is the circulating medium of the regenerative Rankine cycle. In the aforementioned regenerative Rankine cycle, the seawater heat exchanger has at least one stage, and each stage of seawater heat exchanger is connected to an expander, through which power is output. LNG is converted into NG after sequential heat exchange through propane cold storage cycle or compression liquefaction equipment group and regenerative Rankine cycle; air is compressed and liquefied by compression liquefaction equipment group and stored in liquefied air storage tank (1101); liquefied air is expanded and vaporized into air through reheat Rankine cycle and expansion work equipment group.

2. The liquefied air energy storage system according to claim 1, which couples LNG cold energy, ORC technology, and natural heat source, is characterized in that, The propane cold storage cycle includes a propane storage tank (1201), a propane storage tank (1202), a centrifugal pump (3002), a centrifugal pump (3003), and a heat exchanger (2101). The No. 1 propane storage tank (1201), the No. 2 centrifugal pump (3002), the No. 1 heat exchanger (2101), the No. 2 propane storage tank (1202), the No. 3 centrifugal pump (3003), and the compression liquefaction equipment group are connected in sequence, and the compression liquefaction equipment group is connected to the No. 1 propane storage tank (1201) to form a cycle; The cold source of the No. 1 heat exchanger (2101) is LNG, and the heat source is the circulating medium of the propane cold storage cycle.

3. A liquefied air energy storage system coupled with LNG cold energy, ORC technology, and a natural heat source according to claim 1 or 2, characterized in that, The aforementioned compression liquefaction equipment group includes several stages of multi-stream heat exchangers connected in series, with a compressor connected between the heat outlet of the previous stage multi-stream heat exchanger and the heat inlet of the next stage multi-stream heat exchanger. The heat source for the compressed liquefaction equipment group is air, and the cold source is the circulating medium of LNG and / or propane cold storage cycle.

4. A liquefied air energy storage system coupled with LNG cold energy, ORC technology, and natural heat source according to claim 1, characterized in that, The circulating medium of the regenerative Rankine cycle is a mixture of hydrocarbons.

5. A liquefied air energy storage system coupled with LNG cold energy, ORC technology, and natural heat source according to claim 1, characterized in that, The reheat Rankine cycle includes a heat exchanger (2104) #4, a centrifugal pump (3006) #6, a seawater heat exchanger, and an expander. The hot flow outlet of heat exchanger #4 (2104) is connected to the inlet of centrifugal pump #6 (3006), the outlet of centrifugal pump #6 (3006) is connected to the cold flow inlet of seawater heat exchanger, the cold flow outlet of seawater heat exchanger is connected to the inlet of expander, and the outlet of expander is connected to the hot flow inlet of heat exchanger #4 (2104), forming a cycle. The heat source of the No. 4 heat exchanger (2104) is the circulating medium of the reheat Rankine cycle, and the cold source is liquefied air; the heat source of the seawater heat exchanger comes from the solar heating subsystem, and the cold source is the circulating medium of the reheat Rankine cycle. In the reheat Rankine cycle, the seawater heat exchanger has at least one stage, and each stage of seawater heat exchanger is connected to an expander, which outputs power.

6. A liquefied air energy storage system coupled with LNG cold energy, ORC technology, and natural heat source according to claim 5, characterized in that, The circulating medium of the reheat Rankine cycle is a mixture of hydrocarbons.

7. A liquefied air energy storage system coupled with LNG cold energy, ORC technology, and natural heat source according to claim 1, characterized in that, The expansion working equipment group includes several stages of seawater heat exchangers arranged in series, and an expander is connected after each stage of seawater heat exchanger. The heat source for the expansion work unit comes from the solar heating subsystem, and the cold source is liquefied air.

8. A liquefied air energy storage system coupled with LNG cold energy, ORC technology, and natural heat source according to claim 1, characterized in that, The liquefied air energy storage system also includes a centrifugal pump (3001) connected before the propane cold storage cycle, a seawater heat exchanger (2201) connected after the regenerative Rankine cycle, a centrifugal pump (3005) connected between the liquefied air storage tank (1101) and the reheat Rankine cycle, and a seawater heat exchanger (2210) connected after the expansion work unit.

9. A mode of operation for a liquefied air energy storage system coupled with LNG cold energy, ORC technology, and natural heat source as described in any one of claims 1-8, characterized in that, During off-peak electricity demand The LNG and / or propane cold storage cycle releases heat to the compression liquefaction unit, compressing and liquefying ambient air into liquefied air and storing it in the liquefied air storage tank (1101). Subsequently, the LNG releases heat to the regenerative Rankine cycle and is converted into NG. At the same time, the expander in the regenerative Rankine cycle outputs power. During peak electricity consumption periods LNG releases heat into the propane cold storage cycle, storing cold energy within the cycle. Subsequently, the LNG releases heat into the regenerative Rankine cycle and converts it into NG. Simultaneously, the expander in the regenerative Rankine cycle outputs work. The liquefied air stored in the liquefied air storage tank (1101) releases heat to the reheat Rankine cycle, causing the expander in the reheat Rankine cycle to output work. At the same time, the liquefied air is converted into low-temperature and high-pressure gaseous air. The low-temperature and high-pressure gaseous air then enters the expansion work unit to output work and is converted into normal temperature and pressure air.

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