LNG (Liquefied Natural Gas) cold energy gradient utilization system coupled with seawater desalination and liquefied air energy storage

Abstract

The invention discloses an LNG (Liquefied Natural Gas) cold energy gradient utilization system coupled with seawater desalination and liquefied air energy storage. A seawater desalination module of the system carries out seawater desalination by using cold energy of liquefied natural gas, and a liquefied air energy storage module carries out air compression and liquefaction in a power off-peak period and releases energy to generate power in a power peak period; the system can switch a seawater desalination priority mode, an energy storage peak regulation mode and a composite energy supply mode. According to the system, a double-loop structure is adopted, liquefied natural gas cold energy, solar heat energy, electric energy and environmental resources are fully coupled, multi-energy complementation, gradient utilization and combined cooling heating and power are achieved, flexible switching of three cooperative operation modes is achieved, the operation state of the system can be adjusted according to the external load requirement, the resource utilization efficiency and the operation economy are improved, and the energy consumption is reduced. The modular design has good expandability and engineering adaptability, has the characteristics of being green, energy-saving, environment-friendly, high in safety and stable in operation, and is suitable for guaranteeing regional water resources and balancing power generation fluctuation of unstable green energy.

Description

Technical Field

[0001] The present invention relates to a cold energy cascade utilization system, and relates to the technical field of liquefied natural gas (LNG) cold energy recovery, and in particular to an LNG cold energy cascade utilization system coupled with seawater desalination and liquefied air energy storage. Background Art

[0002] With the adjustment of the global energy structure and the increasing requirements for ecological and environmental protection, low-carbon and efficient energy utilization and water resource acquisition have become major issues that need to be addressed urgently. Among them, liquefied natural gas (LNG), as an important clean energy, releases a large amount of cold energy during the gasification process. If it is not fully recovered, it will lead to energy waste. On the other hand, global freshwater resources are becoming increasingly scarce, and seawater desalination technology has gradually become an important way to solve water shortages. In addition, the increasing proportion of renewable energy power generation also places higher demands on the peak-shaving capacity of the power grid. Liquid air energy storage (LAES), as an emerging physical energy storage method, has the advantages of fast response and environmental friendliness, and has broad application prospects.

[0003] In existing technologies, liquefied natural gas (LNG) cold energy is mostly used in cold storage refrigeration, air separation and purification, and has not been fully combined with seawater desalination or energy storage technology for cascade utilization. Seawater desalination systems often use multi-stage flash evaporation (MSF) and reverse osmosis (RO), which have the problems of high energy consumption and limited desalination efficiency. As a low-temperature desalination technology, the freezing point crystallization method has the advantages of low energy consumption and good desalination effect, but its cold source supply is still the key to restricting its promotion and application. In addition, although the current liquefied air energy storage system can realize the time-shift conversion of electrical energy, the cooling load at the liquefaction end is large and the energy utilization rate is low.

[0004] Therefore, how to effectively introduce liquefied natural gas (LNG) cold energy into the desalination and air liquefaction processes, and build a coordinated, multifunctional, integrated utilization system, has become a key technical issue for improving resource utilization efficiency and achieving coordinated energy and water resource security. To address this issue, there is no mature integrated system solution. There is an urgent need to propose a modular coupling structure to achieve efficient recovery of LNG cold energy and distributed energy utilization. Summary of the Invention

[0005] To address the problems presented in the background art, the present invention provides a cascaded LNG cold energy utilization system that couples seawater desalination with liquefied air energy storage. Based on modular synergy for liquefied natural gas (LNG) cold energy recovery, the system integrates seawater desalination and liquefied air energy storage modules to achieve efficient cascaded utilization of LNG cold energy, balancing freshwater production, electricity peak regulation, and natural gas output. This improves the system's overall energy efficiency, alleviates freshwater resource shortages, and reduces energy losses. The system is suitable for comprehensive cold energy utilization at LNG receiving stations or gasification terminals.

[0006] The technical solution adopted in the present invention is:

[0007] The LNG cold energy cascade utilization system coupled with seawater desalination and liquefied air energy storage of the present invention comprises:

[0008] Liquefied natural gas (LNG) storage tanks are used to store liquefied natural gas (LNG).

[0009] The liquefied natural gas (LNG) pump is connected to the liquefied natural gas (LNG) storage tank and is used to pump out the stored liquefied natural gas (LNG).

[0010] The seawater desalination module is connected to the liquefied natural gas (LNG) pump and is used to desalinate seawater using the cold energy of the pumped liquefied natural gas (LNG).

[0011] The liquefied air energy storage module is connected to the liquefied natural gas (LNG) pump and is used to compress and liquefy air during periods of low electricity consumption, while releasing energy to generate electricity during periods of peak electricity consumption.

[0012] By operating the seawater desalination module alone, a seawater desalination priority mode is implemented; by operating the liquefied air energy storage module alone, an energy storage peak-shaving mode is implemented; and by operating the seawater desalination module and the liquefied air energy storage module at the same time, a composite energy supply mode is implemented.

[0013] The desalination module includes a first liquefied natural gas (LNG) cold energy recovery unit, an organic Rankine cycle (ORC) power generation unit, a crystallization desalination unit, a water storage and reverse osmosis desalination unit, a seawater input and concentrated seawater discharge unit, and a fourth heat exchanger. The first liquefied natural gas (LNG) cold energy recovery unit is connected to the organic Rankine cycle (ORC) power generation unit and the seawater input and discharge unit. The first liquefied natural gas (LNG) cold energy recovery unit exchanges heat with the liquefied natural gas (LNG) pressurized by the liquefied natural gas (LNG) pump and the organic Rankine cycle (ORC) power generation unit, and gasifies the liquefied natural gas (LNG) into natural gas (NG) and outputs it to the external pipeline network. The organic Rankine cycle (ORC) power generation unit also The fourth heat exchanger is connected and electrically connected to the crystallization desalination unit. The fourth heat exchanger is connected to the crystallization desalination unit. The organic Rankine cycle ORC power generation unit evaporates the organic Rankine cycle working fluid therein into a high-pressure gas higher than the preset pressure through the fourth heat exchanger, and then expands to generate electrical energy to provide a heat source for the crystallization desalination unit. At the same time, the low-pressure gas after expansion and pressure reduction is returned to the first liquefied natural gas LNG cold energy recovery unit to absorb the cold energy of the liquefied natural gas LNG for condensation and liquefaction, completing a cycle; the crystallization desalination unit is also connected to the water storage and reverse osmosis desalination unit and the seawater input and discharge unit. The cold energy absorbed by the crystal desalination unit through the fourth heat exchanger provides a cold source for the crystallization of seawater, thereby separating the original seawater of the ocean into ice crystals and concentrated seawater with a higher salt content than the original seawater, and washing the ice crystals to produce brine, which is then mixed with concentrated seawater to obtain mixed concentrated seawater, which is then transmitted to the seawater input and discharge unit. The washed ice crystals are melted again to generate pre-desalinated water with a lower salt content than the original seawater, which is then transmitted to the water storage and reverse osmosis desalination unit, and then returned to itself through the water storage and reverse osmosis desalination unit to complete the cycle; the water storage and reverse osmosis desalination unit is also connected to the seawater input and discharge unit, and the water storage and reverse osmosis desalination unit are connected to the seawater input and discharge unit. The salt unit processes the pre-desalinated water delivered by the crystallization desalination unit and outputs fresh water with a salt content lower than that of the pre-desalinated water, and at the same time delivers the precipitated concentrated seawater to the seawater input and discharge unit; the seawater input and discharge unit delivers pre-cooled seawater to the crystallization desalination unit, and recovers the residual cold of the delivered mixed concentrated seawater and discharges it into the sea; when the demand for fresh water is higher than the preset first demand threshold, the liquefied natural gas (LNG) cold energy cascade utilization system operates in a seawater desalination priority mode, and when the demand for natural gas (NG) is higher than the preset second demand threshold, the liquefied natural gas (LNG) cold energy cascade utilization system operates in a composite energy supply mode.

[0014] The first liquefied natural gas (LNG) cold energy recovery unit includes a first throttle valve, a first heat exchanger, a second heat exchanger, a third heat exchanger and a first turbine expander. The outlet of the liquefied natural gas (LNG) pump is connected to the evaporation side inlet of the first heat exchanger through the first throttle valve. The condensation side outlet and the condensation side inlet of the first heat exchanger are both connected to the organic Rankine cycle (ORC) power generation unit. The evaporation side outlet of the first heat exchanger is connected to the evaporation side inlet of the second heat exchanger. The evaporation side outlet of the second heat exchanger is connected to the evaporation side inlet of the third heat exchanger through the first turbine expander. The first turbine expander is also electrically connected to the first generator G. The evaporation side outlet of the third heat exchanger is connected to the external pipeline network. The condensation side inlet of the third heat exchanger and the condensation side outlet of the second heat exchanger are both connected to the seawater input and discharge unit. The condensation side outlet of the third heat exchanger is connected to the condensation side inlet of the second heat exchanger.

[0015] The organic Rankine cycle ORC power generation unit includes a first working fluid pump, a second turbine expander and an electric heat accumulator. The inlet of the first working fluid pump is connected to the condensing side outlet of the first heat exchanger, the outlet of the first working fluid pump is connected to the evaporating side inlet of the fourth heat exchanger, the evaporating side outlet of the fourth heat exchanger is connected to the inlet of the second turbine expander, and the outlet of the second turbine expander is connected to the condensing side inlet of the first heat exchanger. A second generator G is also electrically connected between the second turbine expander and the electric heat accumulator, and the electric heat accumulator is electrically connected to the crystallization desalination unit.

[0016] An organic Rankine cycle working medium is provided at the inlet of the first working medium pump. The liquefied natural gas (LNG) pump transmits the pressurized liquefied natural gas (LNG) to the first heat exchanger through the first throttle valve for heat exchange with the organic Rankine cycle working medium and then partially gasifies it into natural gas NG. At the same time, the organic Rankine cycle working medium that has absorbed the cold energy of the liquefied natural gas (LNG) enters the fourth heat exchanger under the push of the first working medium pump, evaporates into high-pressure gas higher than the preset pressure through the fourth heat exchanger, and then enters the second turbine expander for expansion and work, obtaining low-pressure gas after expansion and decompression, thereby driving the second generator G to generate electricity, and then driving the electric heat accumulator to provide a heat source for the crystallization desalination unit, and at the same time returns the low-pressure gas after expansion and decompression to the first turbine expander. A heat exchanger absorbs the cold energy of liquefied natural gas (LNG) to condense and liquefy it, completing a cycle and then providing cold energy for the crystallization desalination unit; the seawater input and discharge unit pumps the original seawater into the third heat exchanger, and the first heat exchanger sequentially transmits the vaporized natural gas NG to the second heat exchanger and the first turbine expander for expansion and work, thereby driving the first generator G to generate electricity, and then transmits the remaining cold energy to the third heat exchanger to cool the original seawater, so as to perform dual recovery of cold energy and pressure energy, and finally completely vaporizes the liquefied natural gas LNG into natural gas NG and outputs it to the external pipeline network; the third heat exchanger transmits the pre-cooled seawater to the crystallization desalination unit through the second heat exchanger and the seawater input and discharge unit in sequence.

[0017] The crystallization desalination unit includes an ice melting tank, a second working fluid pump, a crystallizer and a scrubber. The fourth heat exchanger is provided with a crystallization circulating working fluid. The condensation side outlet of the fourth heat exchanger is connected to the inlet of the second working fluid pump, the outlet of the second working fluid pump is connected to the first inlet of the crystallizer, the second inlet and the second outlet of the crystallizer are connected to the seawater input and discharge unit, the first outlet of the crystallizer is connected to the condensation side inlet of the fourth heat exchanger, the third outlet of the crystallizer is connected to the first inlet of the scrubber, the second inlet of the scrubber is connected to the water storage and reverse osmosis desalination unit, the first outlet of the scrubber is connected to the seawater input and discharge unit, the second outlet of the scrubber is connected to the inlet of the ice melting tank, and the outlet of the ice melting tank is connected to the water storage and the reverse osmosis desalination unit. The input end and the output end of the electric heat accumulator are respectively electrically connected to the output end and the input end of the ice melting tank to provide a heat source for the ice melting tank.

[0018] The seawater input and discharge unit transmits the pre-cooled seawater to the crystallizer. The fourth heat exchanger transmits the cold energy to the crystallizer through the second working fluid pump to provide a cold source, and then separates the original seawater into ice crystals and concentrated seawater with a higher salt content than the original seawater. The ice crystals are transmitted to the scrubber for fresh water washing to remove the salt attached to the surface and produce brine. The brine and the concentrated seawater output from the crystallizer are mixed to obtain mixed concentrated seawater, which is then transmitted to the seawater input and discharge unit. The washed ice crystals are then transmitted to the ice melting pool to melt and generate pre-desalinated water with a lower salt content than the original seawater, which is then transmitted to the water storage and reverse osmosis desalination unit. The water storage and reverse osmosis desalination unit then returns the pre-desalinated water to the scrubber to wash the ice crystals.

[0019] The water storage and reverse osmosis desalination unit includes a pre-fresh water storage tank, a fresh water pump and a reverse osmosis device. The pre-fresh water storage tank, the fresh water pump and the reverse osmosis device are connected in sequence. The inlet of the pre-fresh water storage tank is connected to the ice melting tank. The first outlet and the second outlet of the pre-fresh water storage tank are respectively connected to the scrubber and the fresh water pump. The pre-fresh water storage tank stores and transmits the pre-fresh water transmitted from the ice melting tank, and transmits the pre-fresh water to the scrubber and the fresh water pump. The fresh water pump pressurizes the pre-fresh water and transmits it to the reverse osmosis device. The reverse osmosis device performs secondary desalination treatment on the pressurized pre-fresh water and outputs high-purity fresh water through the first outlet, and transmits the precipitated concentrated seawater containing salt and other impurities to the seawater through the second outlet.

[0020] The seawater input and discharge unit includes a fifth heat exchanger and a first seawater pump. The fifth heat exchanger transmits the pre-cooled seawater to the crystallizer, receives the mixed concentrated seawater, recovers the excess cold, and then discharges it into the seawater; the first seawater pump pumps the original seawater to the third heat exchanger.

[0021] The liquefied air energy storage module includes a second liquefied natural gas (LNG) cold energy recovery unit, an air compression and liquefaction unit, a liquid air energy storage and gasification power generation unit, a solar thermal collection unit, a sixth heat exchanger and a seventh heat exchanger. The liquefied air energy storage module compresses and liquefies air during power off-peak periods and releases energy to generate electricity during power peak periods; the second liquefied natural gas (LNG) cold energy recovery unit is connected to the sixth heat exchanger, the seventh heat exchanger and the solar thermal collection unit; the liquid air energy storage and gasification power generation unit outputs re-gasified air and mixes it with external clean air to obtain mixed air that is input into the seventh heat exchanger; the second liquefied natural gas (LNG) cold energy recovery unit transfers the liquefied natural gas (LNG) pressurized by the liquefied natural gas (LNG) pump through the sixth heat exchanger for heat exchange and then transfers it to the seventh heat exchanger for pre-cooling the mixed air, and then transfers it to the second liquefied natural gas (LNG) cold energy recovery unit to be completely gasified into natural gas NG and then output to the external pipeline network; the air compression and liquefaction unit is connected to the sixth heat exchanger and the seventh heat exchanger and the liquid air energy storage and gasification power generation unit. The seventh heat exchanger pre-cools the mixed air and then transmits it to the sixth heat exchanger for heat exchange through the air compression and liquefaction unit. The mixed air is then transmitted to the air compression and liquefaction unit for supercooling and expansion and pressure reduction to separate the gasified air and liquefied air. The gasified air is transmitted to the external air, and the liquefied air is transmitted to the liquid air energy storage and gasification power generation unit. The liquid air energy storage and gasification power generation unit is also connected to the solar thermal collection unit. The liquid air energy storage and gasification power generation unit stores the liquefied air and expands it after pressure reduction and heating. After complete gasification, it is mixed with the external clean air to obtain mixed air. The solar thermal collection unit collects the heat energy to heat the circulating seawater in the closed loop, and transmits the heated circulating seawater to the liquid air energy storage and gasification power generation unit and the second liquefied natural gas (LNG) cold energy recovery unit to provide a heat source. When the fresh water demand is lower than or equal to the preset baseline value and the stored fresh water is higher than the preset third demand threshold, the liquefied natural gas (LNG) cold energy cascade utilization system enters the energy storage peak regulation mode.

[0022] The second liquefied natural gas (LNG) cold energy recovery unit includes a second throttle valve and an eighth heat exchanger. The outlet of the liquefied natural gas (LNG) pump is connected to the evaporation side inlet of the sixth heat exchanger through the second throttle valve. The evaporation side outlet of the sixth heat exchanger is connected to the evaporation side inlet of the seventh heat exchanger. The condensation side outlet and condensation side inlet of the sixth heat exchanger are both connected to the air compression and liquefaction unit. The condensation side outlet of the seventh heat exchanger is connected to the air compression and liquefaction unit. The condensation side inlet of the seventh heat exchanger is connected to the liquid air energy storage and gasification power generation unit. The evaporation side outlet of the seventh heat exchanger is connected to the evaporation side inlet of the eighth heat exchanger. The evaporation side outlet of the eighth heat exchanger is connected to the external pipeline network, and the condensation side outlet and condensation side inlet of the eighth heat exchanger are both connected to the solar thermal collection unit; the pressurized liquefied natural gas LNG is subjected to heat exchange through the sixth heat exchanger, releasing the cold energy of the low temperature section to liquefy the pressurized air in the sixth heat exchanger, which can improve the liquefaction rate of the air, and then transmitted to the seventh heat exchanger for pre-cooling of the mixed air, and finally transmitted to the eighth heat exchanger to output the fully vaporized natural gas NG; the eighth heat exchanger receives the heated circulating seawater transmitted by the solar thermal collection unit as a heat source and returns it to the solar thermal collection unit to complete the cycle.

[0023] The air compression liquefaction unit includes a compressor, a ninth heat exchanger, a third turbine expander and a gas-liquid separator. The outlet and inlet of the compressor are respectively connected to the condensing side inlet of the sixth heat exchanger and the condensing side outlet of the seventh heat exchanger. The condensing side outlet of the sixth heat exchanger is connected to the condensing side inlet of the ninth heat exchanger. The condensing side outlet of the ninth heat exchanger is connected to the inlet of the gas-liquid separator through the third turbine expander. The evaporation side outlet of the ninth heat exchanger is connected to the air. The third turbine expander is also electrically connected to the third generator G. The evaporation side inlet of the ninth heat exchanger is connected to the first outlet of the gas-liquid separator. The second outlet of the gas-liquid separator is connected to the liquid air energy storage and gasification power generation unit. The seventh heat exchanger The mixed air is pre-cooled by the heat exchanger and then compressed and liquefied by the compressor. The mixed air then enters the sixth heat exchanger for heat exchange with the pressurized liquefied natural gas LNG to obtain low-temperature and high-pressure liquefied air. The air is then transmitted to the ninth heat exchanger where the partially unliquefied low-temperature air is cooled to further increase the liquefaction rate of the air. The air is then transmitted to the third turbine expander to reduce the pressure to a pressure range that the liquefied air storage tank can withstand, and then transmitted to the gas-liquid separator to separate the gasified air and the liquefied air. The gasified air is supercooled in the ninth heat exchanger and then transmitted to the outside air. The liquefied air is transmitted to the liquid air energy storage and gasification power generation unit.

[0024] The liquid air energy storage and gasification power generation unit includes a liquefied air storage tank, a third throttle valve, a third working fluid pump, a tenth heat exchanger, an eleventh heat exchanger and a fourth turbine expander. The second outlet of the gas-liquid separator is connected to the inlet of the liquefied air storage tank, and the outlet of the liquefied air storage tank is connected to the evaporation side inlet of the tenth heat exchanger through the third throttle valve and the third working fluid pump in turn. The evaporation side outlet of the tenth heat exchanger is connected to the evaporation side inlet of the eleventh heat exchanger through the fourth turbine expander. The fourth turbine expander is also electrically connected to the fourth generator G. The condensation side outlet and condensation side inlet of the tenth heat exchanger are both connected to the solar thermal collection unit, and the evaporation side outlet of the eleventh heat exchanger is connected to the condensation side inlet of the seventh heat exchanger. The condensing side outlet and the condensing side inlet of the eleventh heat exchanger are both connected to the solar thermal collection unit; the liquefied air is transported to the liquefied air storage tank for storage, and then the pressure is reduced by the third throttle valve in the discharge stage, and then the air is transported to the tenth heat exchanger through the third working fluid pump for heating, and then the air is transported to the fourth turbine expander for expansion and power generation, and then the air is transported to the eleventh heat exchanger for further heating to normal pressure and temperature, and then mixed with the external clean air to obtain mixed air; the solar thermal collection unit transports the heated circulating seawater to the tenth heat exchanger and the eleventh heat exchanger as a heat source. After the circulating seawater releases heat energy in the tenth heat exchanger and the eleventh heat exchanger, it returns to the solar thermal collection unit for reheating to complete the cycle.

[0025] The solar thermal collection unit includes a second seawater pump, a third seawater pump, a phase change heat accumulator, a thermal oil circulation pump and a solar thermal collector. The first inlet of the phase change heat accumulator is connected to the condensing side outlet of the eighth heat exchanger, the first outlet of the phase change heat accumulator is connected to the condensing side inlet of the eighth heat exchanger through the second seawater pump, the second inlet of the phase change heat accumulator is connected to the condensing side outlet of the tenth heat exchanger and the eleventh heat exchanger, the second outlet of the phase change heat accumulator is connected to the condensing side inlet of the tenth heat exchanger and the eleventh heat exchanger through the third seawater pump, the third inlet of the phase change heat accumulator is connected to the outlet of the solar thermal collector, and the phase change heat accumulator The third outlet is connected to the inlet of the solar thermal collector through a thermal oil circulation pump; the phase change heat accumulator is provided with thermal oil, and under the drive of the thermal oil circulation pump, the thermal oil transfers the heat energy collected by the solar thermal collector to the phase change heat accumulator through the solar thermal collector to heat the circulating seawater in the closed loop. The phase change heat accumulator, driven by the second seawater pump and the third seawater pump, transfers the heated circulating seawater as a heat source to the eighth heat exchanger, the tenth heat exchanger and the eleventh heat exchanger to heat the energy-releasing circulating medium, increase the work and power generation capacity, and then returns to the phase change heat accumulator to be reheated after releasing the heat energy to complete the cycle.

[0026] The beneficial effects of the present invention are:

[0027] 1. The system of the present invention adopts a dual-circuit structure constructed by the collaborative use of seawater desalination modules and liquefied air energy storage modules, fully coupling liquefied natural gas (LNG) cooling energy, solar thermal energy, electricity, and environmental resources to achieve multi-energy complementarity, cascade utilization, and combined cooling, heating, and power. By flexibly switching between three collaborative operating modes, the system operating state can be adjusted according to external load requirements (such as natural gas supply, power peak regulation, and freshwater production), improving resource utilization efficiency and operational economy. At the same time, the overall modular structure of the system is highly integrated, suitable for deployment in different scales and functional scenarios, and has good scalability and engineering adaptability.

[0028] 2. The desalination module of this system fully recovers the low-temperature cold energy released during the vaporization of liquefied natural gas (LNG), achieving a highly efficient and energy-efficient ice crystal desalination process. Combining power generation with cold energy utilization through the Organic Rankine Cycle (ORC), the module efficiently precipitates ice crystals at low temperatures, producing high-purity fresh water through subsequent washing, melting, and reverse osmosis steps. This module effectively reduces the energy consumption of traditional thermal desalination methods, avoiding high-temperature corrosion and chemical contamination. Its green, energy-saving, and environmentally friendly characteristics make it particularly suitable for securing water resources in coastal areas with unique energy resource constraints.

[0029] 3. The liquefied air energy storage module of the present system utilizes nighttime off-peak electricity to compress and liquefy air, releasing it to generate electricity during peak load periods, thus achieving large-scale power time shifting and grid peak shaving. By introducing cold energy from liquefied natural gas (LNG) into the air liquefaction process, this module significantly reduces system energy consumption. Combined with solar thermal collection and phase-change thermal storage, this module provides a stable heat source during the energy release phase, improving module responsiveness and power generation efficiency. Furthermore, the module uses air as its energy storage medium, offering high safety, pollution-free operation, and stable operation, making it particularly suitable for balancing power generation fluctuations from volatile green energy sources such as wind and solar power. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the system of the present invention;

[0031] In the figure: 1. Liquefied natural gas (LNG) storage tank, 2. Liquefied natural gas (LNG) pump, 3-1. First throttle valve, 3-2. Second throttle valve, 4-1. First heat exchanger, 4-2. Second heat exchanger, 4-3. Third heat exchanger, 5. First turboexpander, 6. First working fluid pump, 7. Fourth heat exchanger, 8. Second turboexpander, 9. Electric heat accumulator, 10. Ice melting tank, 11. Pre-fresh water storage tank, 12. Fresh water pump, 13. Reverse osmosis device, 14. Second working fluid pump, 15. Crystallizer, 16. Scrubber, 17. Fifth heat exchanger, 18. First seawater pump, 19-1. Sixth heat exchanger, 19-2. Seventh heat exchanger, 19-3. Eighth heat exchanger, 20. Compressor, 21. Ninth heat exchanger, 22. Third turbine expander, 23. Gas-liquid separator, 24. Liquefied air storage tank, 25. Third throttle valve, 26. Third working fluid pump, 27-1. Tenth heat exchanger, 27-2. Eleventh heat exchanger, 28. Fourth turbine expander, 29. Second seawater pump, 30. Third seawater pump, 31. Phase change heat accumulator, 32. Thermal oil circulation pump, 33. Solar collector. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but will not limit the present invention in any form.

[0033] like Figure 1 As shown,

[0034] The LNG cold energy cascade utilization system for coupling seawater desalination and liquefied air energy storage of the present invention includes a liquefied natural gas (LNG) storage tank 1, a liquefied natural gas (LNG) pump 2, a seawater desalination module and a liquefied air energy storage module. The liquefied natural gas (LNG) storage tank 1 stores liquefied natural gas (LNG). The liquefied natural gas (LNG) pump 2 is connected to the liquefied natural gas (LNG) storage tank 1 and pumps the stored liquefied natural gas (LNG) to the seawater desalination module. The seawater desalination module is connected to the liquefied natural gas (LNG) pump 2 and utilizes the cold energy of the pumped liquefied natural gas (LNG) to desalinate seawater. The liquefied air energy storage module is connected to the liquefied natural gas (LNG) pump 2 and compresses and liquefies air during power off-peak periods, while releasing energy to generate electricity during power peak periods. The system operates the seawater desalination module alone to perform a seawater desalination priority mode, the liquefied air energy storage module alone to perform an energy storage peak-shaving mode, and the seawater desalination module and the liquefied air energy storage module are simultaneously operated to perform a composite energy supply mode. The system adopts a modular integrated structure with a dual-circuit structure. The three operating modes of the system can adjust the system operating state according to external load requirements.

[0035] The seawater desalination module includes a first liquefied natural gas (LNG) cold energy recovery unit, an organic Rankine cycle (ORC) power generation unit, a crystallization desalination unit, a water storage and reverse osmosis desalination unit, a seawater input and concentrated seawater discharge unit, and a fourth heat exchanger 7. The first liquefied natural gas (LNG) cold energy recovery unit is connected to the organic Rankine cycle (ORC) power generation unit and the seawater input and discharge unit. The first liquefied natural gas (LNG) cold energy recovery unit exchanges heat with the liquefied natural gas (LNG) pressurized by the liquefied natural gas (LNG) pump 2 and the organic Rankine cycle (ORC) power generation unit, and gasifies the liquefied natural gas (LNG) into natural gas (NG) before outputting it. To the external pipeline network; the organic Rankine cycle ORC power generation unit is also connected to the fourth heat exchanger 7 and electrically connected to the crystallization desalination unit. The fourth heat exchanger 7 is connected to the crystallization desalination unit. The organic Rankine cycle ORC power generation unit evaporates the organic Rankine cycle working fluid therein into a high-pressure gas higher than the preset pressure through the fourth heat exchanger 7, and then expands to generate electricity to provide a heat source for the crystallization desalination unit. At the same time, the low-pressure gas after expansion and pressure reduction is returned to the first liquefied natural gas LNG cold energy recovery unit to absorb the cold energy of the liquefied natural gas LNG for condensation and liquefaction, completing a cycle; the crystallization desalination unit is also connected to the water storage and reverse osmosis desalination The cold energy absorbed by the crystallization desalination unit through the fourth heat exchanger 7 provides a cold source for the crystallization of seawater, thereby separating the original seawater of the ocean into ice crystals and concentrated seawater with a higher salt content than the original seawater, and washing the ice crystals to produce brine, which is then mixed with concentrated seawater to obtain mixed concentrated seawater, which is then transmitted to the seawater input and discharge unit. The washed ice crystals are melted again to generate pre-salted water with a lower salt content than the original seawater, which is then transmitted to the water storage and reverse osmosis desalination unit, and then returned to itself through the water storage and reverse osmosis desalination unit to complete the cycle; the water storage and reverse osmosis desalination unit is also connected to the seawater input and discharge unit, The water storage and reverse osmosis desalination unit processes the pre-desalinated water delivered by the crystallization desalination unit and outputs fresh water with a salt content lower than that of the pre-desalinated water, and at the same time delivers the precipitated concentrated seawater to the seawater input and discharge unit; the seawater input and discharge unit delivers pre-cooled seawater to the crystallization desalination unit, and recovers the residual cold of the delivered mixed concentrated seawater and discharges it into the sea; when the demand for fresh water is higher than the preset first demand threshold, the liquefied natural gas (LNG) cold energy cascade utilization system operates in a seawater desalination priority mode, and when the demand for natural gas (NG) is higher than the preset second demand threshold, the liquefied natural gas (LNG) cold energy cascade utilization system operates in a composite energy supply mode.

[0036] The seawater desalination module of the present invention achieves efficient and coordinated processing of energy and water resources through a coupled process involving multi-stage cold energy utilization, heat energy conversion power generation, ice crystal desalination, and reverse osmosis desalination. The cold energy released by liquefied natural gas (LNG) during the vaporization process is used sequentially for condensing the organic Rankine cycle (ORC) working fluid and pre-cooling seawater. The cold energy of the LNG drives the ORC power generation unit through the first heat exchanger 4-1 to generate electricity. Furthermore, the vaporized natural gas further expands through the turbine expander 5 to generate secondary power, thereby effectively improving the overall energy efficiency of the system. The electricity generated by the ORC power generation unit is used to drive the electric heat accumulator 9, providing a heat source for the ice melting tank 10 and ensuring the effective melting of ice crystals. The entire module, driven by the cold energy of LNG, has a high energy cascade utilization efficiency, enabling energy self-sufficiency and the ability to integrate the generated electricity into the grid for output as needed.

[0037] The first liquefied natural gas (LNG) cold energy recovery unit includes a first throttle valve 3-1, a first heat exchanger 4-1, a second heat exchanger 4-2, a third heat exchanger 4-3 and a first turbo expander 5. The outlet of the liquefied natural gas (LNG) pump 2 is connected to the evaporation side inlet of the first heat exchanger 4-1 through the first throttle valve 3-1. The condensation side outlet and the condensation side inlet of the first heat exchanger 4-1 are both connected to the organic Rankine cycle (ORC) power generation unit. The evaporation side outlet of the first heat exchanger 4-1 is connected to the second heat exchanger 4-2. -2, the evaporation side inlet of the second heat exchanger 4-2, the evaporation side outlet of the second heat exchanger 4-2 is connected to the evaporation side inlet of the third heat exchanger 4-3 through the first turbine expander 5, the first turbine expander 5 is also electrically connected to the first generator G, the evaporation side outlet of the third heat exchanger 4-3 is connected to the external pipeline network, the condensation side inlet of the third heat exchanger 4-3 and the condensation side outlet of the second heat exchanger 4-2 are both connected to the seawater input and discharge unit, and the condensation side outlet of the third heat exchanger 4-3 is connected to the condensation side inlet of the second heat exchanger 4-2.

[0038] The organic Rankine cycle ORC power generation unit includes a first working fluid pump 6, a second turbine expander 8 and an electric heat accumulator 9. The inlet of the first working fluid pump 6 is connected to the condensing side outlet of the first heat exchanger 4-1, and the outlet of the first working fluid pump 6 is connected to the evaporating side inlet of the fourth heat exchanger 7. The evaporating side outlet of the fourth heat exchanger 7 is connected to the inlet of the second turbine expander 8. The outlet of the second turbine expander 8 is connected to the condensing side inlet of the first heat exchanger 4-1. A second generator G is also electrically connected between the second turbine expander 8 and the electric heat accumulator 9. The electric heat accumulator 9 is electrically connected to the crystallization desalination unit.

[0039] An organic Rankine cycle working medium is provided at the inlet of the first working medium pump 6. The liquefied natural gas (LNG) pump 2 transmits the pressurized liquefied natural gas (LNG) to the first heat exchanger 4-1 through the first throttle valve 3-1 to exchange heat with the organic Rankine cycle working medium and then partially gasify it into natural gas NG. At the same time, the organic Rankine cycle working medium that has absorbed the cold energy of the liquefied natural gas (LNG) enters the fourth heat exchanger 7 under the push of the first working medium pump 6, evaporates into a high-pressure gas higher than a preset pressure through the fourth heat exchanger 7, and then enters the second turbine expander 8 to expand and perform work, obtaining a low-pressure gas after expansion and decompression, thereby driving the second generator G to generate electricity, and then driving the electric heat accumulator 9 to provide a heat source for the crystallization desalination unit, and at the same time returns the low-pressure gas after expansion and decompression to the first heat exchanger. 4-1 absorbs the cold energy of liquefied natural gas (LNG) to condense and liquefy it, completing a cycle and then providing cold energy for the crystallization desalination unit; the seawater input and discharge unit pumps the original seawater into the third heat exchanger 4-3, and the first heat exchanger 4-1 transmits the vaporized natural gas NG to the second heat exchanger 4-2 and the first turbine expander 5 in sequence for expansion and work, thereby driving the first generator G to generate electricity, and then transmits the remaining cold energy to the third heat exchanger 4-3 to cool the original seawater, so as to perform dual recovery of cold energy and pressure energy, and finally completely vaporizes the liquefied natural gas LNG into natural gas NG and outputs it to the external pipeline network; the third heat exchanger 4-3 transmits the pre-cooled seawater to the crystallization desalination unit through the second heat exchanger 4-2 and the seawater input and discharge unit in sequence.

[0040] The crystallization desalination unit includes an ice melting tank 10, a second working fluid pump 14, a crystallizer 15 and a scrubber 16. The fourth heat exchanger 7 is provided with a crystallization circulating working fluid. The condensation side outlet of the fourth heat exchanger 7 is connected to the inlet of the second working fluid pump 14, the outlet of the second working fluid pump 14 is connected to the first inlet of the crystallizer 15, the second inlet and the second outlet of the crystallizer 15 are connected to the seawater input and discharge unit, the first outlet of the crystallizer 15 is connected to the condensation side inlet of the fourth heat exchanger 7, the third outlet of the crystallizer 15 is connected to the first inlet of the scrubber 16, the second inlet of the scrubber 16 is connected to the water storage and reverse osmosis desalination unit, the first outlet of the scrubber 16 is connected to the seawater input and discharge unit, the second outlet of the scrubber 16 is connected to the inlet of the ice melting tank 10, and the outlet of the ice melting tank 10 is connected to the water storage and the reverse osmosis desalination unit. The input end and the output end of the electric heat accumulator 9 are electrically connected to the output end and the input end of the ice melting tank 10 respectively, thereby providing a heat source for the ice melting tank 10.

[0041] The seawater input and discharge unit transmits the pre-cooled seawater to the crystallizer 15, and the fourth heat exchanger 7 transmits the cold energy to the crystallizer 15 through the second working fluid pump 14 to provide a cold source, thereby separating the original seawater into ice crystals and concentrated seawater with a higher salinity than the original seawater. The ice crystals are transmitted to the scrubber 16 for washing with fresh water to remove the salt attached to the surface and thus produce brine. The brine and the concentrated seawater output from the crystallizer 15 are mixed to obtain mixed concentrated seawater, which is then transmitted to the seawater input and discharge unit. The washed ice crystals are then transmitted to the ice melting tank 10 to melt and generate pre-salinity water with a lower salinity than the original seawater, which is then transmitted to the water storage and reverse osmosis desalination unit. The water storage and reverse osmosis desalination unit then returns the pre-salinity water to the scrubber 16 to wash the ice crystals.

[0042] The water storage and reverse osmosis desalination unit includes a pre-desalinated water storage tank 11, a fresh water pump 12 and a reverse osmosis device 13. The pre-desalinated water storage tank 11, the fresh water pump 12 and the reverse osmosis device 13 are connected in sequence. The inlet of the pre-desalinated water storage tank 11 is connected to the ice melting tank 10. The first outlet and the second outlet of the pre-desalinated water storage tank 11 are connected to the scrubber 16 and the fresh water pump 12 respectively. The pre-desalinated water storage tank 11 stores and transports the pre-desalinated water transmitted from the ice melting tank 10, and transmits the pre-desalinated water to the scrubber 16 and the fresh water pump 12. The fresh water pump 12 pressurizes the pre-desalinated water and transmits it to the reverse osmosis device 13. The reverse osmosis device 13 performs secondary desalination treatment on the pressurized pre-desalinated water and outputs high-purity fresh water through the first outlet, and transmits the precipitated concentrated seawater containing salt and other impurities to the seawater through the second outlet.

[0043] The seawater input and discharge unit includes a fifth heat exchanger 17 and a first seawater pump 18. The fifth heat exchanger 17 transmits the pre-cooled seawater to the crystallizer 15. The fifth heat exchanger 17 receives the mixed concentrated seawater and recovers the residual cold before discharging it into the seawater; the first seawater pump 18 pumps the original seawater to the third heat exchanger 4-3.

[0044] The liquefied air energy storage module includes a second liquefied natural gas (LNG) cold energy recovery unit, an air compression and liquefaction unit, a liquefied air energy storage and gasification power generation unit, a solar thermal collection unit, a sixth heat exchanger 19-1, and a seventh heat exchanger 19-2. The liquefied air energy storage module compresses and liquefies air during power off-peak hours and releases energy to generate electricity during power peak hours. The second liquefied natural gas (LNG) cold energy recovery unit is connected to the sixth heat exchanger 19-1, the seventh heat exchanger 19-2, and the solar thermal collection unit. The liquefied air energy storage and gasification power generation unit outputs power. The newly vaporized air is mixed with the clean air outside to obtain the mixed air which is input into the seventh heat exchanger 19-2. The second liquefied natural gas (LNG) cold energy recovery unit transfers the liquefied natural gas (LNG) pressurized by the liquefied natural gas (LNG) pump 2 through the sixth heat exchanger 19-1 for heat exchange and then transfers it to the seventh heat exchanger 19-2 for pre-cooling the mixed air. The mixed air is then transferred to the second liquefied natural gas (LNG) cold energy recovery unit to be completely vaporized into natural gas (NG) and then output to the external pipeline network. The air compression liquefaction unit is connected to the sixth heat exchanger 1 9-1, the seventh heat exchanger 19-2 and the liquid air energy storage and gasification power generation unit. The seventh heat exchanger 19-2 pre-cools the mixed air and transmits it to the sixth heat exchanger 19-1 through the air compression and liquefaction unit for heat exchange. The mixed air is then transmitted to the air compression and liquefaction unit for supercooling and expansion and pressure reduction to separate the gasified air and the liquefied air. The gasified air is transmitted to the outside air and the liquefied air is transmitted to the liquid air energy storage and gasification power generation unit. The liquid air energy storage and gasification power generation unit is also connected to the solar thermal collection unit. The liquid air energy storage and gasification power generation unit is connected to the solar thermal collection unit. The electric unit stores liquefied air, reduces its pressure, heats it, and then expands it. After it is completely vaporized, it is mixed with clean air from the outside to obtain mixed air. The solar thermal collection unit collects heat energy to heat the circulating seawater in a closed loop, and transmits the heated circulating seawater to the liquid air energy storage and gasification power generation unit and the second liquefied natural gas (LNG) cold energy recovery unit to provide a heat source. When the demand for fresh water is lower than or equal to the preset baseline value and the stored fresh water is higher than the preset third demand threshold, the liquefied natural gas (LNG) cold energy cascade utilization system enters the energy storage peak regulation mode.

[0045] The liquefied air energy storage module of the present invention utilizes off-peak periods to drive air compression and liquefaction, achieving cross-period storage and release of electrical energy, effectively alleviating grid load fluctuations, and possessing large-scale energy storage capabilities and good operational safety. By introducing liquefied natural gas (LNG) cold energy as a liquefaction cooling source, the energy consumption of the air liquefaction process is significantly reduced, improving the energy efficiency of the system. At the same time, the solar collector 33 is combined with the phase-change heat accumulator 31 to provide a stable heat source for the vaporization of liquid air, thereby improving the power generation capacity and peak-shaving response speed during the energy release phase. Especially during periods of insufficient solar radiation or nighttime operation, the phase-change heat accumulator 31 can continue to release heat, providing a stable heat source for the liquid air energy storage and vaporization power generation units in the liquefied air energy storage module, thereby significantly improving the module's overall performance and operational flexibility. The module adopts a modular structural design, which is easy to expand and flexibly deploy. It is suitable for a variety of application scenarios such as grid peak regulation and renewable energy supporting energy storage, significantly improving the overall flexibility and comprehensive utilization efficiency of the energy system.

[0046] The second liquefied natural gas (LNG) cold energy recovery unit includes a second throttle valve 3-2 and an eighth heat exchanger 19-3. The outlet of the liquefied natural gas (LNG) pump 2 is connected to the evaporation side inlet of the sixth heat exchanger 19-1 through the second throttle valve 3-2. The evaporation side outlet of the sixth heat exchanger 19-1 is connected to the evaporation side inlet of the seventh heat exchanger 19-2. The condensation side outlet and condensation side inlet of the sixth heat exchanger 19-1 are both connected to the air compression and liquefaction unit. The condensation side outlet of the seventh heat exchanger 19-2 is connected to the air compression and liquefaction unit. The condensation side inlet of the seventh heat exchanger 19-2 is connected to the liquid air energy storage and gasification power generation unit. The evaporation side outlet of the seventh heat exchanger 19-2 is connected to the evaporation side inlet of the eighth heat exchanger 19-3. The evaporation side inlet and the evaporation side outlet of the eighth heat exchanger 19-3 are connected to the external pipeline network, and the condensation side outlet and condensation side inlet of the eighth heat exchanger 19-3 are both connected to the solar thermal collection unit; the pressurized liquefied natural gas LNG is heat exchanged through the sixth heat exchanger 19-1, releasing the cold energy of the low-temperature section to liquefy the pressurized air in the sixth heat exchanger 19-1, which can improve the liquefaction rate of the air, and then transmitted to the seventh heat exchanger 19-2 for pre-cooling of the mixed air, and finally transmitted to the eighth heat exchanger 19-3 to output the fully vaporized natural gas NG; the eighth heat exchanger 19-3 receives the heated circulating seawater transmitted by the solar thermal collection unit as a heat source and returns to the solar thermal collection unit to complete the cycle.

[0047] The air compression liquefaction unit includes a compressor 20, a ninth heat exchanger 21, a third turbine expander 22 and a gas-liquid separator 23. The outlet and inlet of the compressor 20 are respectively connected to the condensing side inlet of the sixth heat exchanger 19-1 and the condensing side outlet of the seventh heat exchanger 19-2. The condensing side outlet of the sixth heat exchanger 19-1 is connected to the condensing side inlet of the ninth heat exchanger 21. The condensing side outlet of the ninth heat exchanger 21 is connected to the inlet of the gas-liquid separator 23 through the third turbine expander 22. The evaporation side outlet of the ninth heat exchanger 21 is connected to the air. The third turbine expander 22 is also electrically connected to the third generator G. The evaporation side inlet of the ninth heat exchanger 21 is connected to the first outlet of the gas-liquid separator 23. The second outlet of the gas-liquid separator 23 is connected to the liquid air energy storage and gas The seventh heat exchanger 19-2 pre-cools the mixed air, and then the pre-cooled mixed air is compressed and liquefied by the compressor 20 and enters the sixth heat exchanger 19-1 for heat exchange with the pressurized liquefied natural gas LNG to obtain low-temperature and high-pressure liquefied air. The air is then transmitted to the ninth heat exchanger 21 where the partially unliquefied low-temperature air is cooled to further increase the liquefaction rate of the air. The air is then transmitted to the third turbine expander 22 for pressure reduction to a pressure range that the liquefied air storage tank 24 can withstand, and then transmitted to the gas-liquid separator 23 to separate the gasified air and the liquefied air. The gasified air is supercooled in the ninth heat exchanger 21 to the low-temperature and high-pressure liquefied air and then transmitted to the external air. The liquefied air is transmitted to the liquid air energy storage and gasification power generation unit.

[0048] The liquid air energy storage and gasification power generation unit includes a liquefied air storage tank 24, a third throttle valve 25, a third working fluid pump 26, a tenth heat exchanger 27-1, an eleventh heat exchanger 27-2 and a fourth turbine expander 28. The second outlet of the gas-liquid separator 23 is connected to the inlet of the liquefied air storage tank 24. The outlet of the liquefied air storage tank 24 is connected to the evaporation side inlet of the tenth heat exchanger 27-1 through the third throttle valve 25 and the third working fluid pump 26 in sequence. The evaporation side outlet of the tenth heat exchanger 27-1 is connected to the evaporation side inlet of the eleventh heat exchanger 27-2 through the fourth turbine expander 28. The fourth turbine expander 28 is also electrically connected to the fourth generator G. The condensation side outlet and condensation side inlet of the tenth heat exchanger 27-1 are both connected to the solar thermal collection unit. The evaporation side outlet of the eleventh heat exchanger 27-2 is connected to the seventh heat exchanger 19. -2, and the condensing side outlet and condensing side inlet of the eleventh heat exchanger 27-2 are both connected to the solar thermal collection unit; the liquefied air is transported to the liquefied air storage tank 24 for storage, and then reduced in pressure by the third throttle valve 25 during the discharge stage, and then transported to the tenth heat exchanger 27-1 through the third working fluid pump 26 for heating, and then transported to the fourth turbine expander 28 for expansion and power generation, and then transported to the eleventh heat exchanger 27-2 for further heating to normal pressure and temperature, and then mixed with external clean air to obtain mixed air; the solar thermal collection unit transports the heated circulating seawater to the tenth heat exchanger 27-1 and the eleventh heat exchanger 27-2 as a heat source. The circulating seawater releases heat energy in the tenth heat exchanger 27-1 and the eleventh heat exchanger 27-2 and then returns to the solar thermal collection unit for reheating, completing the cycle.

[0049] The solar thermal collection unit includes a second seawater pump 29, a third seawater pump 30, a phase change heat accumulator 31, a thermal oil circulation pump 32 and a solar thermal collector 33. The first inlet of the phase change heat accumulator 31 is connected to the condensing side outlet of the eighth heat exchanger 19-3, and the first outlet of the phase change heat accumulator 31 is connected to the condensing side inlet of the eighth heat exchanger 19-3 through the second seawater pump 29. The second inlet of the phase change heat accumulator 31 is connected to the condensing side outlets of the tenth heat exchanger 27-1 and the eleventh heat exchanger 27-2. The second outlet of the phase change heat accumulator 31 is connected to the condensing side inlets of the tenth heat exchanger 27-1 and the eleventh heat exchanger 27-2 through the third seawater pump 30. The third inlet of the phase change heat accumulator 31 is connected to the outlet of the solar thermal collector 33. The third outlet of the phase-change heat accumulator 31 is connected to the inlet of the solar thermal collector 33 via a thermal oil circulation pump 32. Phase-change heat accumulator 31 is filled with thermal oil. Driven by the thermal oil circulation pump 32, the thermal oil transfers the heat energy collected by the solar thermal collector 33 to the phase-change heat accumulator 31, heating the circulating seawater within the closed loop. Driven by the second and third seawater pumps 29 and 30, the phase-change heat accumulator 31 then transfers the heated circulating seawater as a heat source to the eighth heat exchanger 19-3, the tenth heat exchanger 27-1, and the eleventh heat exchanger 27-2, where it heats the energy-releasing circulating medium, increasing its power generation capacity. The heat then returns to the phase-change heat accumulator 31 after releasing it for reheating, completing the cycle. Phase-change heat accumulator 31 is used to store heat during periods of sunshine and release stable heat energy during the power generation phase, thereby improving the stability of the thermal energy input during the liquefied air expansion power generation process.

[0050] The workflow of the system of the present invention is as follows:

[0051] 1) After being pressurized by LNG pump 2, liquefied natural gas (LNG) enters multi-stage heat exchangers 4-1, 4-2, and 4-3 for cold energy transfer. In the first stage of heat exchanger 4-1, the cold energy is transferred to the organic Rankine cycle (ORC) power generation unit to drive the condensation of the ORC working fluid. In the second stage of heat exchanger 4-2 and the third stage of heat exchanger 4-3, the cold energy of LNG is transferred step by step to pre-cool and crystallize seawater, thereby achieving ice crystal precipitation and desalination of seawater.

[0052] 2) During the seawater crystallization process, the electricity generated by the Organic Rankine Cycle (ORC) power generation unit drives the ice melting pool 10 to melt the cleaned ice crystals to generate pre-desalinated water. The pre-desalinated water is stored in the pre-desalinated water storage tank 11 and sent to the reverse osmosis device 13 through the fresh water pump 12 for further desalination to obtain high-purity fresh water.

[0053] 3) During power off-peak hours, the liquefied air energy storage module is activated, and clean air is compressed by compressor 20 and sent to multiple heat exchangers 19-1, 19-2, and 21 for heat exchange with the cold energy of liquefied natural gas (LNG) to liquefy the air. The liquefied air is then stored in a liquefied air storage tank 24. When the power grid enters its peak load phase, the liquid air expands and produces work through throttling and heat exchange, driving a turbine expander 28 to output electricity.

[0054] 4) During the expansion of liquefied air, the solar collector 33 and the phase change heat accumulator 31 are used to provide a stable heat source to improve the expansion power generation efficiency.

[0055] 5) Through real-time monitoring of fresh water demand, grid load, and natural gas transmission pressure, the system intelligently switches to seawater desalination priority mode, energy storage peak-shaving mode, or combined energy supply mode.

[0056] In a combined energy supply mode, the desalination module and the liquefied air energy storage module operate simultaneously. While ensuring that the desalination module's production capacity meets demand, excess cold energy is channeled into the liquefied air energy storage module, increasing the liquefied natural gas (LNG) vaporization rate and achieving coordinated and optimized multi-energy utilization. The system of the present invention provides combined cooling, heating, and power generation. Organic Rankine cycle (ORC) power generation, liquefied natural gas (LNG) vaporization, and liquid air expansion together form the power output path. The desalination module outputs high-purity fresh water, and the solar thermal collection unit provides stable heat support.

[0057] The system of the present invention is equipped with three collaborative operation modes, and the specific technical solutions are as follows:

[0058] Mode 1, Desalination Priority Mode: When the system detects that freshwater demand exceeds the preset first demand threshold and the natural gas pipeline pressure is in the steady-state range, the desalination module is activated. This mode uses a cold energy transfer chain constructed by a multi-stage heat exchanger to gradiently transfer the -162°C low-temperature cold energy released during the phase change of liquefied natural gas (LNG) to the desalination system. This allows the seawater to complete the ice crystal precipitation and melting desalination process in a low-temperature environment of -5°C to 2°C, achieving efficient desalination.

[0059] Mode 2, Energy Storage Peak Shaving Mode: When the system detects that the grid is entering off-peak hours, fresh water demand is below or equal to a preset baseline, and stored fresh water is sufficient to meet demand, the liquefied air energy storage module is activated. This mode utilizes the synergistic effect of compressor 20 and heat exchangers 19-1, 19-2, 19-3, 21, 27-1, and 27-2. During nighttime, off-peak electricity is used to drive compressor 20. Simultaneously, the heat exchanger uses the cold energy of liquefied natural gas (LNG) to cool compressed air, bringing the air's liquefaction temperature below -150°C. During peak grid load periods, the stored liquid air is heated to a supercritical state by a solar thermal collector, driving turbine expanders 22 and 28 and the generator set to output electricity. The heating medium is a circulating seawater system preheated to 60-80°C by solar energy.

[0060] Mode 3, Hybrid Energy Supply: When a surge in natural gas demand triggers the second preset demand threshold, the system will simultaneously operate the desalination module and the liquefied air energy storage module. This mode ensures that the desalination module's production capacity meets demand while also channeling excess cold energy into the liquefied air energy storage module, increasing the amount of liquefied natural gas (LNG) vaporized to meet user needs.

[0061] The system of the present invention realizes the comprehensive utilization of liquefied natural gas (LNG) cold energy. By combining the LNG gasification process with seawater desalination and liquefied air energy storage modules, it provides an efficient and feasible LNG cold energy utilization solution. The LNG gasification is configured to operate continuously for 24 hours. The generated cold energy is coordinated and utilized by the seawater desalination module and the liquefied air energy storage module. This not only meets the demand for fresh water, but also uses the surplus power of the power grid to drive the air compressor to generate high-pressure air during low-power consumption periods, which is then cooled into liquid air for storage through multiple stages. During peak power consumption periods, the seawater is heated by solar collectors 33 installed along the coast. The heated seawater is then input into the liquefied air energy storage module as a heat source, causing the liquid air to vaporize and expand to produce work, driving the generator set to output peak-shaving electricity, effectively improving the efficiency of comprehensive energy utilization.

[0062] It should be noted that the embodiments described herein are intended only to illustrate the technical solutions of the present invention and do not constitute limitations. Although the present invention has been described in detail with respect to specific embodiments, those skilled in the art should understand that, without departing from the inventive concept of the present invention, the technical solutions described in the embodiments may be adaptively adjusted, or some or all of the technical features may be equivalently replaced. Such modifications or replacements fall within the scope of protection of the claims of the present invention and do not affect the substantive content of the present invention.

Claims

1. A LNG cold energy cascade utilization system coupling seawater desalination and liquefied air energy storage, characterized in that: include: A liquefied natural gas (LNG) storage tank (1) is used to store liquefied natural gas (LNG); a liquefied natural gas (LNG) pump (2), connected to the liquefied natural gas (LNG) storage tank (1) and used to pump out the stored liquefied natural gas (LNG); a seawater desalination module connected to a liquefied natural gas (LNG) pump (2) and used to desalinate seawater using cold energy of the pumped liquefied natural gas (LNG); A liquefied air energy storage module is connected to a liquefied natural gas (LNG) pump (2) and is used to compress and liquefy air during power off-peak hours and release energy to generate electricity during power peak hours; By operating the seawater desalination module alone, a seawater desalination priority mode is implemented; by operating the liquefied air energy storage module alone, an energy storage peak-shaving mode is implemented; and by operating the seawater desalination module and the liquefied air energy storage module at the same time, a composite energy supply mode is implemented.

2. The LNG cold energy cascade utilization system coupled with seawater desalination and liquefied air energy storage according to claim 1 is characterized in that: The seawater desalination module includes a first liquefied natural gas (LNG) cold energy recovery unit, an organic Rankine cycle (ORC) power generation unit, a crystallization desalination unit, a water storage and reverse osmosis desalination unit, a seawater input and discharge unit, and a fourth heat exchanger (7). The first liquefied natural gas (LNG) cold energy recovery unit is connected to the organic Rankine cycle (ORC) power generation unit and the seawater input and discharge unit. The first liquefied natural gas (LNG) cold energy recovery unit exchanges heat with the liquefied natural gas (LNG) pressurized by the liquefied natural gas (LNG) pump (2) and the organic Rankine cycle (ORC) power generation unit, and gasifies the liquefied natural gas (LNG) into natural gas (NG) before transmitting the gas to the desalination unit. The organic Rankine cycle ORC power generation unit is also connected to the fourth heat exchanger (7) and electrically connected to the crystallization desalination unit. The fourth heat exchanger (7) is connected to the crystallization desalination unit. The organic Rankine cycle ORC power generation unit evaporates the organic Rankine cycle working fluid therein into a high-pressure gas higher than a preset pressure through the fourth heat exchanger (7), and then expands to generate electrical energy to provide a heat source for the crystallization desalination unit. At the same time, the low-pressure gas after expansion and pressure reduction is returned to the first liquefied natural gas LNG cold energy recovery unit to absorb the cold energy of the liquefied natural gas LNG for condensation and liquefaction, completing a cycle. The crystallization desalination unit is also connected to the water storage and The reverse osmosis desalination unit and the seawater input and discharge unit, the cold energy absorbed by the crystallization desalination unit through the fourth heat exchanger (7) provides a cold source for the crystallization of seawater, thereby separating the original seawater of the ocean into ice crystals and concentrated seawater with a salt content higher than the original seawater, and washing the ice crystals to produce salt water, which is then mixed with the concentrated seawater to obtain mixed concentrated seawater, which is then transmitted to the seawater input and discharge unit, and the washed ice crystals are melted to generate pre-salted water with a salt content lower than the original seawater, which is then transmitted to the water storage and reverse osmosis desalination unit, and then returned to itself through the water storage and reverse osmosis desalination unit to complete the cycle; the water storage and reverse osmosis desalination unit are also connected to the seawater input and discharge Unit, the water storage and reverse osmosis desalination unit processes the pre-desalinated water delivered by the crystallization desalination unit and outputs fresh water with a salt content lower than that of the pre-desalinated water, and at the same time delivers the precipitated concentrated seawater to the seawater input and discharge unit; the seawater input and discharge unit delivers pre-cooled seawater to the crystallization desalination unit, and recovers the residual cold of the delivered mixed concentrated seawater and discharges it into the sea; when the demand for fresh water is higher than the preset first demand threshold, the liquefied natural gas (LNG) cold energy cascade utilization system performs the seawater desalination priority mode, and when the demand for natural gas (NG) is higher than the preset second demand threshold, the liquefied natural gas (LNG) cold energy cascade utilization system performs the composite energy supply mode.

3. The LNG cold energy cascade utilization system coupled with seawater desalination and liquefied air energy storage according to claim 2 is characterized in that: The first liquefied natural gas (LNG) cold energy recovery unit comprises a first throttle valve (3-1), a first heat exchanger (4-1), a second heat exchanger (4-2), a third heat exchanger (4-3) and a first turbine expander (5); the outlet of the liquefied natural gas (LNG) pump (2) is connected to the evaporation side inlet of the first heat exchanger (4-1) through the first throttle valve (3-1); the condensation side outlet and the condensation side inlet of the first heat exchanger (4-1) are both connected to the organic Rankine cycle (ORC) power generation unit; the evaporation side outlet of the first heat exchanger (4-1) is connected to the second heat exchanger (4-2); (4-2), the evaporation side inlet of the second heat exchanger (4-2), the evaporation side outlet of the second heat exchanger (4-2) is connected to the evaporation side inlet of the third heat exchanger (4-3) through the first turbine expander (5), the first turbine expander (5) is also electrically connected to the first generator G, the evaporation side outlet of the third heat exchanger (4-3) is connected to the external pipe network, the condensation side inlet of the third heat exchanger (4-3) and the condensation side outlet of the second heat exchanger (4-2) are both connected to the seawater input and discharge unit, and the condensation side outlet of the third heat exchanger (4-3) is connected to the condensation side inlet of the second heat exchanger (4-2); The organic Rankine cycle (ORC) power generation unit comprises a first working fluid pump (6), a second turbine expander (8) and an electric heat accumulator (9), wherein the inlet of the first working fluid pump (6) is connected to the condensation side outlet of the first heat exchanger (4-1), the outlet of the first working fluid pump (6) is connected to the evaporation side inlet of the fourth heat exchanger (7), the evaporation side outlet of the fourth heat exchanger (7) is connected to the inlet of the second turbine expander (8), the outlet of the second turbine expander (8) is connected to the condensation side inlet of the first heat exchanger (4-1), a second generator G is electrically connected between the second turbine expander (8) and the electric heat accumulator (9), and the electric heat accumulator (9) is electrically connected to the crystallization desalination unit; An organic Rankine cycle working medium is provided at the inlet of the first working medium pump (6). The liquefied natural gas (LNG) pump (2) transmits the pressurized liquefied natural gas (LNG) to the first heat exchanger (4-1) through the first throttle valve (3-1) to exchange heat with the organic Rankine cycle working medium and then partially gasify it into natural gas NG. At the same time, the organic Rankine cycle working medium that has absorbed the cold energy of the liquefied natural gas (LNG) enters the fourth heat exchanger (7) under the push of the first working medium pump (6), evaporates into a high-pressure gas higher than a preset pressure through the fourth heat exchanger (7), and then enters the second turbine expander (8) to expand and perform work, thereby obtaining a low-pressure gas after expansion and decompression, thereby driving the second generator G to generate electricity, and then driving the electric heat accumulator (9) to provide a heat source for the crystallization desalination unit, and at the same time returns the low-pressure gas after expansion and decompression to the first turbine expander (8). The heat exchanger (4-1) absorbs the cold energy of liquefied natural gas (LNG) to condense and liquefy it, completing a cycle, and then provides cold energy for the crystallization desalination unit; the seawater input and discharge unit pumps the original seawater into the third heat exchanger (4-3), and the first heat exchanger (4-1) transmits the gasified natural gas NG to the second heat exchanger (4-2) and the first turbine expander (5) in sequence for expansion and work, thereby driving the first generator G to generate electricity, and then transmits the cold energy to the third heat exchanger (4-3) to cool the original seawater, so as to perform dual recovery of cold energy and pressure energy, and finally completely gasifies the liquefied natural gas LNG into natural gas NG and outputs it to the external pipeline network; the third heat exchanger (4-3) transmits the pre-cooled seawater to the crystallization desalination unit through the second heat exchanger (4-2) and the seawater input and discharge unit in sequence.

4. The LNG cold energy cascade utilization system coupled with seawater desalination and liquefied air energy storage according to claim 3 is characterized by: The crystallization desalination unit comprises an ice melting tank (10), a second working fluid pump (14), a crystallizer (15) and a scrubber (16); a crystallization circulating working fluid is provided in the fourth heat exchanger (7); the condensation side outlet of the fourth heat exchanger (7) is connected to the inlet of the second working fluid pump (14); the outlet of the second working fluid pump (14) is connected to the first inlet of the crystallizer (15); the second inlet and the second outlet of the crystallizer (15) are connected to the seawater input and discharge unit; the first outlet of the crystallizer (15) is connected to the condensation side inlet of the fourth heat exchanger (7) The third outlet of the crystallizer (15) is connected to the first inlet of the scrubber (16), the second inlet of the scrubber (16) is connected to the water storage and reverse osmosis desalination unit, the first outlet of the scrubber (16) is connected to the seawater input and discharge unit, the second outlet of the scrubber (16) is connected to the inlet of the ice melting tank (10), the outlet of the ice melting tank (10) is connected to the water storage and reverse osmosis desalination unit, and the input end and the output end of the electric heat accumulator (9) are respectively electrically connected to the output end and the input end of the ice melting tank (10) to provide a heat source for the ice melting tank (10); The seawater input and discharge unit transmits the pre-cooled seawater to the crystallizer (15), and the fourth heat exchanger (7) transmits the cold energy to the crystallizer (15) through the second working fluid pump (14) to provide a cold source, thereby separating the original seawater into ice crystals and concentrated seawater with a higher salinity than the original seawater. The ice crystals are transmitted to the scrubber (16) for washing with fresh water to remove the salt attached to the surface and thus produce brine. The brine and the concentrated seawater output from the crystallizer (15) are mixed to obtain mixed concentrated seawater, which is then transmitted to the seawater input and discharge unit. The washed ice crystals are then transmitted to the ice melting tank (10) to melt and generate pre-salted water with a lower salinity than the original seawater, which is then transmitted to the water storage and reverse osmosis desalination unit. The water storage and reverse osmosis desalination unit then returns the pre-salted water to the scrubber (16) to wash the ice crystals.

5. The LNG cold energy cascade utilization system coupled with seawater desalination and liquefied air energy storage according to claim 4 is characterized in that: The water storage and reverse osmosis desalination unit comprises a pre-fresh water storage tank (11), a fresh water pump (12) and a reverse osmosis device (13). The pre-fresh water storage tank (11), the fresh water pump (12) and the reverse osmosis device (13) are connected in sequence. The inlet of the pre-fresh water storage tank (11) is connected to the ice melting tank (10). The first outlet and the second outlet of the pre-fresh water storage tank (11) are connected to the scrubber (16) and the fresh water pump (12) respectively. The pre-fresh water storage tank (11) stores and transports the pre-fresh water transmitted from the ice melting tank (10), and transmits the pre-fresh water to the scrubber (16) and the fresh water pump (12). The fresh water pump (12) pressurizes the pre-fresh water and transmits it to the reverse osmosis device (13). The reverse osmosis device (13) performs secondary desalination treatment on the pressurized pre-fresh water and outputs fresh water through the first outlet, and transmits the precipitated concentrated seawater to the seawater through the second outlet. The seawater input and discharge unit includes a fifth heat exchanger (17) and a first seawater pump (18). The fifth heat exchanger (17) transmits the pre-cooled seawater to the crystallizer (15). The fifth heat exchanger (17) receives the mixed concentrated seawater and recovers the residual cooling before discharging it into the seawater. The first seawater pump (18) pumps the original seawater to the third heat exchanger (4-3).

6. The LNG cold energy cascade utilization system coupled with seawater desalination and liquefied air energy storage according to claim 1 is characterized in that: The liquefied air energy storage module includes a second liquefied natural gas (LNG) cold energy recovery unit, an air compression and liquefaction unit, a liquid air energy storage and gasification power generation unit, a solar heat collection unit, a sixth heat exchanger (19-1) and a seventh heat exchanger (19-2). The liquefied air energy storage module compresses and liquefies air during power off-peak hours and releases energy to generate electricity during power peak hours. The second liquefied natural gas (LNG) cold energy recovery unit is connected to the sixth heat exchanger (19-1), the seventh heat exchanger (19-2) and the solar heat collection unit. The liquid air energy storage and gasification power generation unit The unit outputs the re-gasified air and mixes it with the external air to obtain the mixed air which is input into the seventh heat exchanger (19-2). The second liquefied natural gas (LNG) cold energy recovery unit transfers the liquefied natural gas (LNG) pressurized by the liquefied natural gas (LNG) pump (2) through the sixth heat exchanger (19-1) for heat exchange and then transfers it to the seventh heat exchanger (19-2) to pre-cool the mixed air. The mixed air is then transferred to the second liquefied natural gas (LNG) cold energy recovery unit to be completely gasified into natural gas NG and then output to the external pipeline network. The air compression liquefaction unit is connected to the first The sixth heat exchanger (19-1), the seventh heat exchanger (19-2) and the liquid air energy storage and gasification power generation unit, the seventh heat exchanger (19-2) pre-cools the mixed air and transmits it to the sixth heat exchanger (19-1) through the air compression and liquefaction unit for heat exchange, and then transmits it to the air compression and liquefaction unit for supercooling and expansion and pressure reduction to separate the gasified air and the liquefied air, the gasified air is transmitted to the outside air, and the liquefied air is transmitted to the liquid air energy storage and gasification power generation unit; the liquid air energy storage and gasification power generation unit is also connected to the solar thermal collection unit, and the liquid air The gas energy storage and gasification power generation unit stores liquefied air, reduces its pressure, heats it, and then expands it. After it is completely gasified, it is mixed with external air to obtain mixed air. The solar thermal collection unit collects heat energy to heat the circulating seawater in a closed loop, and transmits the heated circulating seawater to the liquid air energy storage and gasification power generation unit and the second liquefied natural gas (LNG) cold energy recovery unit to provide a heat source. When the fresh water demand is lower than or equal to the preset baseline value and the stored fresh water is higher than the preset third demand threshold, the liquefied natural gas (LNG) cold energy cascade utilization system enters the energy storage peak regulation mode.

7. The LNG cold energy cascade utilization system coupled with seawater desalination and liquefied air energy storage according to claim 6 is characterized by: The second liquefied natural gas (LNG) cold energy recovery unit includes a second throttle valve (3-2) and an eighth heat exchanger (19-3). The outlet of the liquefied natural gas (LNG) pump (2) is connected to the evaporation side inlet of the sixth heat exchanger (19-1) through the second throttle valve (3-2). The evaporation side outlet of the sixth heat exchanger (19-1) is connected to the evaporation side inlet of the seventh heat exchanger (19-2). The condensation side outlet and the condensation side inlet of the sixth heat exchanger (19-1) are both connected to the air compression and liquefaction unit. The condensation side outlet of the seventh heat exchanger (19-2) is connected to the air compression and liquefaction unit. The condensation side inlet of the seventh heat exchanger (19-2) is connected to the liquid air energy storage and gasification power generation unit. The evaporation side outlet of the seventh heat exchanger (19-2) is connected to the evaporation side inlet of the seventh heat exchanger (19-2). To the evaporation side inlet of the eighth heat exchanger (19-3), the evaporation side outlet of the eighth heat exchanger (19-3) is connected to the external pipeline network, and the condensation side outlet and condensation side inlet of the eighth heat exchanger (19-3) are both connected to the solar thermal collection unit; the pressurized liquefied natural gas LNG is heat exchanged through the sixth heat exchanger (19-1), releasing cold energy to liquefy the pressurized air in the sixth heat exchanger (19-1), and then transmitted to the seventh heat exchanger (19-2) for pre-cooling of the mixed air, and finally transmitted to the eighth heat exchanger (19-3) to output completely vaporized natural gas NG; the eighth heat exchanger (19-3) receives the heated circulating seawater transmitted by the solar thermal collection unit as a heat source and returns to the solar thermal collection unit to complete the cycle.

8. The LNG cold energy cascade utilization system coupled with seawater desalination and liquefied air energy storage according to claim 7 is characterized in that: The air compression liquefaction unit includes a compressor (20), a ninth heat exchanger (21), a third turbine expander (22) and a gas-liquid separator (23). The outlet and inlet of the compressor (20) are respectively connected to the condensation side inlet of the sixth heat exchanger (19-1) and the condensation side outlet of the seventh heat exchanger (19-2). The condensation side outlet of the sixth heat exchanger (19-1) is connected to the condensation side inlet of the ninth heat exchanger (21). The condensation side outlet of the ninth heat exchanger (21) is connected to the inlet of the gas-liquid separator (23) through the third turbine expander (22). The evaporation side outlet of the ninth heat exchanger (21) is connected to the air. The third turbine expander (22) is also electrically connected to the third generator G. The evaporation side inlet of the ninth heat exchanger (21) is connected to the gas-liquid separator (23). ) is connected to the first outlet of the gas-liquid separator (23), and the second outlet of the gas-liquid separator (23) is connected to the liquid air energy storage and gasification power generation unit; the seventh heat exchanger (19-2) pre-cools the mixed air, and the pre-cooled mixed air is compressed and liquefied by the compressor (20), and then enters the sixth heat exchanger (19-1) to exchange heat with the pressurized liquefied natural gas LNG to obtain low-temperature and high-pressure liquefied air, and then transmitted to the ninth heat exchanger (21) for cooling, and then transmitted to the third turbine expander (22) for pressure reduction, and then transmitted to the gas-liquid separator (23) to separate gasified air and liquefied air, the gasified air is supercooled by the ninth heat exchanger (21) to the low-temperature and high-pressure liquefied air and then transmitted to the external air, and the liquefied air is transmitted to the liquid air energy storage and gasification power generation unit.

9. The LNG cold energy cascade utilization system coupled with seawater desalination and liquefied air energy storage according to claim 8 is characterized in that: The liquid air energy storage and gasification power generation unit includes a liquefied air storage tank (24), a third throttle valve (25), a third working fluid pump (26), a tenth heat exchanger (27-1), an eleventh heat exchanger (27-2) and a fourth turbine expander (28). The second outlet of the gas-liquid separator (23) is connected to the inlet of the liquefied air storage tank (24). The outlet of the liquefied air storage tank (24) is connected to the evaporation side inlet of the tenth heat exchanger (27-1) through the third throttle valve (25) and the third working fluid pump (26) in sequence. The evaporation side outlet of the tenth heat exchanger (27-1) is connected to the evaporation side inlet of the eleventh heat exchanger (27-2) through the fourth turbine expander (28). The fourth turbine expander (28) is also electrically connected to the fourth generator G. The condensation side outlet and condensation side inlet of the tenth heat exchanger (27-1) are both connected to the solar thermal collection unit. The evaporation side outlet of the eleventh heat exchanger (27-2) is connected to the evaporation side inlet of the eleventh heat exchanger (27-2). The generating side outlet is connected to the condensing side inlet of the seventh heat exchanger (19-2), and the condensing side outlet and the condensing side inlet of the eleventh heat exchanger (27-2) are both connected to the solar heat collection unit; the liquefied air is transported to the liquefied air storage tank (24) for storage, then reduced in pressure by the third throttle valve (25), and then transported to the tenth heat exchanger (27-1) through the third working fluid pump (26) for heating, then transported to the fourth turbine expander (28) for expansion and power generation, and then transported to the eleventh heat exchanger (27-2) for further heating and mixing with external air to obtain mixed air; the solar heat collection unit transports the heated circulating seawater to the tenth heat exchanger (27-1) and the eleventh heat exchanger (27-2) as a heat source, and the circulating seawater releases heat energy in the tenth heat exchanger (27-1) and the eleventh heat exchanger (27-2) and returns to the solar heat collection unit for reheating, completing the cycle.

10. The LNG cold energy cascade utilization system coupled with seawater desalination and liquefied air energy storage according to claim 9 is characterized in that: The solar heat collection unit comprises a second seawater pump (29), a third seawater pump (30), a phase change heat accumulator (31), a heat transfer oil circulation pump (32) and a solar heat collector (33); the first inlet of the phase change heat accumulator (31) is connected to the condensation side outlet of the eighth heat exchanger (19-3); the first outlet of the phase change heat accumulator (31) is connected to the condensation side inlet of the eighth heat exchanger (19-3) through the second seawater pump (29); the second inlet of the phase change heat accumulator (31) is connected to the condensation side outlet of the tenth heat exchanger (27-1) and the eleventh heat exchanger (27-2); the second outlet of the phase change heat accumulator (31) is connected to the condensation side inlet of the tenth heat exchanger (27-1) and the eleventh heat exchanger (27-2) through the third seawater pump (30); the third inlet of the phase change heat accumulator (31) is connected to the condensation side outlet of the tenth heat exchanger (27-1) and the eleventh heat exchanger (27-2) The outlet of the solar heat collector (33) is connected to the third outlet of the phase change heat accumulator (31) through the heat transfer oil circulation pump (32) and the inlet of the solar heat collector (33); the phase change heat accumulator (31) is provided with heat transfer oil, and the heat transfer oil, driven by the heat transfer oil circulation pump (32), transfers the heat energy collected by the solar heat collector (33) to the phase change heat accumulator (31) through the solar heat collector (33) to heat the circulating seawater in the closed loop; the phase change heat accumulator (31) transfers the heated circulating seawater as a heat source to the eighth heat exchanger (19-3), the tenth heat exchanger (27-1) and the eleventh heat exchanger (27-2) under the drive of the second seawater pump (29) and the third seawater pump (30), and then returns to the phase change heat accumulator (31) to be reheated after releasing the heat energy, thereby completing the cycle.

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