Offshore multi-energy supply system based on constant pressure compressed carbon dioxide energy storage and operation method thereof

Abstract

The application discloses an offshore multi-energy combined supply system based on constant-pressure compressed carbon dioxide energy storage and an operation method thereof, and the system comprises a working medium storage device, a heat energy storage device, a charging process module, a gas-liquid conversion loop, a discharging process module, a cold energy supply module and a heat energy supply module; the application improves the energy release process structure of the compressed carbon dioxide energy storage system, and the pressure of high-pressure carbon dioxide is reduced to normal pressure after one-time expansion, so that low-temperature cold energy is generated at the same time of power generation, the consumption of heat storage is saved, the remaining heat storage is used for heat supply, the comprehensive utilization rate of energy is improved, and cold, heat and electricity multi-energy combined supply is realized; the system of the application further comprises an integrated heat-driven combined cooling and power supply subsystem capable of switching power generation / cooling mode, organic Rankine cycle and ejector refrigeration cycle are highly integrated, investment cost and space occupation are reduced, excess heat energy is flexibly and efficiently converted into electric energy or cold energy, and the flexibility of multi-energy combined supply of the system is improved.

Description

Technical Field

[0001] This invention belongs to the field of novel energy storage and multi-energy supply technology, and in particular relates to an offshore multi-energy supply system based on constant pressure compressed carbon dioxide energy storage and its operation method. Background Technology

[0002] In recent years, my country's installed capacity of offshore wind power has continued to climb, and its large-scale development is of great significance for the green power supply and low-carbon energy transition in coastal and deep-sea areas. Although more abundant than onshore wind power, the volatility of offshore wind power when connected to the grid on a large scale can still weaken the grid's resilience. Therefore, it is necessary to configure "site-specific" energy storage technologies to ensure the absorption of offshore wind power and improve system economics. Utilizing offshore renewable energy for centralized cooling and refrigeration can eliminate the need for refrigeration units on fishing vessels, saving costs and freeing up cabin space. The construction of integrated offshore energy islands has also generated demand for thermal energy and freshwater. Thermal seawater desalination technologies such as multi-stage flash evaporation and multi-effect distillation can produce freshwater using low-grade thermal energy. Therefore, if offshore renewable energy can be effectively utilized and converted into stable electricity, cooling, and thermal energy, it will provide necessary energy security for marine ranches, distant islands, and offshore energy islands. Chinese patent CN116816649B proposes a multi-generation system for underwater compressed air energy storage, capable of meeting diverse energy needs including cooling, heating, electricity, and freshwater supply. However, this system places high-pressure compressed air underwater, and the significant buoyancy makes reliable ballast installation difficult at sea. Furthermore, the system directly uses the heat of compression from the energy storage process for other energy supplies, while relying entirely on solar thermal collection during energy release, rendering this approach unsuitable for deep-sea platforms.

[0003] Compressed carbon dioxide (CCCO) energy storage systems utilize carbon dioxide as the working fluid and offer advantages such as long lifespan, high efficiency, and low cost. Currently, it has become a research hotspot for novel long-term energy storage technologies and, with improvements, is expected to become a reliable offshore energy storage solution. Chinese patent application CN120062847A proposes an offshore constant-pressure compressed carbon dioxide energy storage system and method coupled with ocean temperature differences. This system utilizes seawater hydrostatic pressure to achieve constant-pressure storage of high-pressure carbon dioxide and achieves a gas-liquid phase change of carbon dioxide by coupling with ocean temperature differences, increasing the density of high-pressure carbon dioxide underwater and reducing buoyancy. However, this system currently only enables the storage and release of electrical energy and is not suitable for combined cooling, heating, and power generation. It requires additional electrical equipment to meet the diverse energy demands of deep-sea development and offshore energy islands. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies where the energy release process can only output a single type of electrical energy and cannot achieve combined cooling, heating, and power (CCHP), this invention aims to provide a marine CCHP system and its operation method based on constant-pressure compressed carbon dioxide energy storage, targeting the integration of deep-sea wind power. By improving the energy release process structure of the compressed carbon dioxide energy storage system, the high-pressure carbon dioxide is reduced to atmospheric pressure after one expansion, generating low-temperature cold energy while simultaneously generating electricity, and saving on heat storage consumption. The remaining heat storage is used for medium- and low-temperature cascade heating, thereby achieving CCHP. The liquid storage tank is moored on the seabed, and multiple liquid storage tanks are arranged in parallel to reduce longitudinal pressure changes and improve reliability. At the same time, a bidirectional carbon dioxide transport pipeline is used to transport high-pressure carbon dioxide between the offshore platform and the seabed, reducing pipeline investment. This invention also provides an integrated heat-driven CCHP subsystem with switchable power generation / cooling modes, which highly integrates the organic Rankine cycle and jet refrigeration cycle, reducing investment costs and space occupation. By flexibly and efficiently converting excess heat energy into electrical or cold energy, the flexibility of the system's CCHP is improved.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The offshore multi-energy supply system based on constant pressure compressed carbon dioxide energy storage includes: working fluid storage device, thermal energy storage device, charging process module, gas-liquid conversion circuit, discharge process module, cold energy supply module and thermal energy supply module.

[0007] Working fluid storage device: including a gas storage bag 1 and several parallel connected liquid storage bags 14;

[0008] Thermal energy storage device: including low temperature storage tank 7 and high temperature storage tank 8;

[0009] Charging process module: used to convert offshore new energy power generation into pressure energy and thermal energy of carbon dioxide; including an electric motor 2, a first compressor 3, a first cooler 4, a second compressor 5, and a second cooler 6 electrically connected to the offshore new energy power generation device; the power output shaft of the electric motor 2 is connected to the power input shaft of the first compressor 3 and the second compressor 5; the outlet of the gas storage bladder 1 is connected to the inlet of the first compressor 3, the outlet of the first compressor 3 is connected to the inlet of the second compressor 5 through the high-temperature side of the first cooler 4, and the outlet of the second compressor 5 is connected to the high-temperature side inlet of the second cooler 6; the outlet of the cryogenic storage tank 7 is connected to the cryogenic side inlet of the second cooler 6 and the cryogenic side inlet of the first cooler 4 respectively, and the cryogenic side outlet of the second cooler 6 and the cryogenic side outlet of the first cooler 4 are both connected to the inlet of the high-temperature storage tank 8;

[0010] Gas-liquid conversion circuit: used to transport high-pressure gaseous carbon dioxide from the offshore platform to the seabed and liquefy it, and to vaporize high-pressure liquid carbon dioxide from the seabed and transport it to the offshore platform; including a first condenser 12, a first seawater pump 13, a first working fluid pump 15, a first evaporator 16, a second seawater pump 17, and a bidirectional carbon dioxide transport pipeline; the high-temperature side outlet of the second condenser 16 is connected to the high-temperature side inlet of the first condenser 12 through the bidirectional carbon dioxide transport pipeline, and the high-temperature side outlet of the first condenser 12 is connected to the inlet of the liquid storage tank 14; the low-temperature side inlet of the first condenser 12 is connected to the seabed pipeline through the first seawater pump 13; the outlet of the liquid storage tank 14 is connected to the low-temperature side inlet of the first evaporator 16 through the first working fluid pump 15, and the low-temperature side outlet of the first evaporator 16 is connected to the inlet of the discharge process module through the bidirectional carbon dioxide transport pipeline; the high-temperature side inlet of the first evaporator 16 is connected to the shallow sea pipeline through the second seawater pump 17;

[0011] The discharge process module is used to convert stored pressure energy and thermal energy back into electrical energy; it includes a preheater 18, a heater 19, a first turbine 20, and a generator 21; the low-temperature side outlet of the first evaporator 16 is connected to the low-temperature side inlet of the preheater 18 through a bidirectional carbon dioxide transport pipeline, the low-temperature side outlet of the preheater 18 is connected to the low-temperature side inlet of the heater 19, the low-temperature side outlet of the heater 19 is connected to the inlet of the first turbine 20, and the power output shaft of the first turbine 20 is connected to the power input shaft of the generator 21; the first outlet of the high-temperature storage tank 8 is connected in series with the high-temperature side of the heater 19 and the high-temperature side of the preheater 18, and the high-temperature side outlet of the preheater 18 is connected to the inlet of the low-temperature storage tank 7;

[0012] Cold energy supply module: Uses the low-temperature cold energy generated after carbon dioxide expansion for cooling; includes a cooling heat exchanger 22, the outlet of the first turbine 20 is connected to the low-temperature side inlet of the cooling heat exchanger 22, and the low-temperature side outlet of the cooling heat exchanger 22 is connected to the inlet of the gas storage bladder 1.

[0013] Heat supply module: Uses the remaining heat storage after heating carbon dioxide for heating; includes a first heat exchanger 23 and a second heat exchanger 24, the second outlet of the high temperature storage tank 8 is connected in series to the high temperature side of the first heat exchanger 23 and the high temperature side of the second heat exchanger 24, and the outlet of the high temperature side of the second heat exchanger 24 is connected to the inlet of the high temperature side of the preheater 18.

[0014] The system also includes an integrated thermal-driven combined cooling and power subsystem that uses the residual heat storage from the first heat exchanger 23 or the second heat exchanger 24 as a heat source and low-temperature seawater as a cold source. The subsystem includes an organic Rankine cycle for converting the stored thermal energy into electrical energy and a jet refrigeration cycle for converting the stored thermal energy into cold energy.

[0015] The organic Rankine cycle includes a second turbine 25, a second generator 26, a second condenser 27, a third seawater pump 28, and a second working fluid pump 29. In the thermal power generation mode, the first outlet on the low-temperature side of the first heat exchanger 23 or the second heat exchanger 24 is connected to the inlet of the second turbine 25, the outlet of the second turbine 25 is connected to the high-temperature side inlet of the second condenser 27, and the high-temperature side outlet of the second condenser 27 is connected to the low-temperature side inlet of the first heat exchanger 23 or the second heat exchanger 24 via the second working fluid pump 29, thus forming an organic Rankine cycle. The power output shaft of the second turbine 25 is connected to the power input shaft of the second generator 26.

[0016] The jet refrigeration cycle includes a second condenser 27, a third seawater pump 28, a second working fluid pump 29, an ejector 30, a throttle valve 31, and a second evaporator 32. In the hot-cooling mode, the second outlet on the low-temperature side of the first heating heat exchanger 23 or the second heating heat exchanger 24 is connected to the high-pressure inlet of the ejector 30, the outlet on the low-temperature side of the second evaporator 32 is connected to the low-pressure inlet of the ejector 30, and the outlet of the ejector 30 is connected to the high-temperature inlet of the second condenser 27. The outlet on the high-temperature side of the second condenser 27 is split, with one part connected to the low-temperature inlet of the second evaporator 32 through the throttle valve 31, and the other part connected to the low-temperature inlet of the first heating heat exchanger 23 or the second heating heat exchanger 24 through the second working fluid pump 29, thus forming the jet refrigeration cycle. The high-temperature side of the second evaporator 32 is a refrigerant used to transport the cold energy generated by the jet refrigeration cycle.

[0017] The low-temperature side inlet of the second condenser 27 is connected to a seawater pipeline through the third seawater pump 28, and the second condenser 27 uses low-temperature seawater as a cold source.

[0018] The bidirectional carbon dioxide transport pipeline includes a first reversing valve 9, a carbon dioxide pipeline 10, and a second reversing valve 11; wherein, the carbon dioxide pipeline 10 is used for bidirectional transport of high-pressure carbon dioxide, and the first reversing valve 9 and the second reversing valve 11 are both used to change the flow direction of carbon dioxide.

[0019] Both the air storage bladder 1 and the liquid storage bag 14 are made of multi-layered flexible materials.

[0020] The heat storage medium in both the cryogenic storage tank 7 and the high-temperature storage tank 8 is pressurized water or heat transfer oil.

[0021] The high-temperature side of the cooling heat exchanger 22 is a refrigerant used to transport the cold energy generated at the outlet of the first turbine 20.

[0022] In the heat energy supply module, the first heat exchanger 23 releases medium-temperature heat energy for the thermal power generation system, and the second heat exchanger 24 releases low-temperature heat energy for heating or for the thermal-driven refrigeration system or thermal seawater desalination device, thereby realizing the cascade utilization of heat energy.

[0023] This invention also provides an operation method for a marine multi-energy system based on constant-pressure compressed carbon dioxide energy storage, including the energy storage process and the energy release process;

[0024] During the energy storage process, the offshore new energy power generation device supplies power to the motor 2 to drive the compressor to compress the low-pressure gaseous carbon dioxide in the gas storage bag 1 in two stages to a high-pressure state. The heat energy generated by the compression of carbon dioxide is absorbed by the heat storage medium in the low-temperature storage tank 7. After the temperature of the heat storage medium rises, it is stored in the high-temperature storage tank 8. The low-temperature high-pressure carbon dioxide after releasing heat is sent to the seabed through the carbon dioxide bidirectional transport pipeline. It is cooled by the deep-sea low-temperature seawater in the first condenser 12. After the high-pressure carbon dioxide is completely condensed into liquid, it is stored in the liquid storage bag 14.

[0025] During the energy release process, the high-pressure liquid carbon dioxide stored in the liquid storage tank 14 is pressurized by the first working fluid pump 15 and transported to the first evaporator 16. After absorbing heat from the high-temperature seawater in the shallow sea, it evaporates into a gaseous state and is then transported to the offshore platform through a bidirectional carbon dioxide transport pipeline. It then enters the preheater 18 and heater 19, where it is heated to a high temperature by the heat storage medium stored in the high-temperature storage tank 8. It then enters the first turbine 20 to expand and do work, driving the generator 21 to generate electricity. After the carbon dioxide at the outlet of the first turbine 20 expands to a low pressure, its own temperature drops. At temperatures as low as zero, the heat storage medium releases cold energy into the refrigerant in the cooling heat exchanger 22, and after its own temperature rises, it enters the gas storage bladder 1 for storage. Part of the heat storage medium at the outlet of the high-temperature storage tank 8 enters the heater 19 to heat carbon dioxide, and the other part successively enters the first heating heat exchanger 23 and the second heating heat exchanger 24, successively releasing medium-temperature heat energy and low-temperature heat energy to achieve cascade utilization of heat energy. After the heat storage medium flows through the heater 19 and the second heating heat exchanger 24, it mixes and enters the preheater 18, where its temperature is further reduced before being stored in the low-temperature storage tank 7.

[0026] Compared with existing technologies, the advantages of this invention are as follows:

[0027] 1. The marine multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage proposed in this invention improves the energy release process structure of the compressed carbon dioxide energy storage system, enabling the generation of low-temperature cold energy while saving the consumption of heat storage. The remaining heat storage is used for heating, improving the comprehensive utilization rate of energy. The unused medium-temperature heat storage releases heat energy through two stages of medium and low temperatures, realizing the cascade utilization of heat storage. The medium-temperature heat energy can be used to drive the thermal power generation system, and the low-temperature heat energy can be used to drive the thermal seawater desalination device or absorption refrigeration, etc. The combination of the two realizes a stable supply of multiple energy sources such as cooling, heating, and power based on marine compressed carbon dioxide energy storage.

[0028] 2. The marine multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage proposed in this invention uses a bidirectional carbon dioxide transport pipeline to transport carbon dioxide between the offshore platform and the seabed, reducing the cost of high-pressure pipelines; the storage tanks are moored on the seabed, and the carbon dioxide density is increased through liquefaction, achieving reliable ballast; the storage tanks are arranged in parallel with multiple small-volume storage tanks, which reduces longitudinal pressure changes compared to a single storage tank, and prevents the entire system from failing due to the failure of a single storage tank, thus improving robustness; the storage tanks use multi-layered flexible materials, which improves reliability in complex underwater environments, and the bottom single-sided carbon dioxide inlet and outlet design improves sealing performance.

[0029] 3. The marine multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage proposed in this invention provides an integrated thermal-driven combined cooling and power supply subsystem with switchable power generation and cooling modes. By highly integrating the organic Rankine cycle and the jet refrigeration cycle and sharing equipment, the investment cost is reduced while the space occupied on the offshore platform is reduced. By adjusting the flow rate of the organic working fluid to the second turbine and the ejector, the switching between power supply and cooling can be realized, improving the flexibility of the system's multi-energy supply. The second condenser uses low-temperature seawater as a cold source, further utilizing ocean thermal energy and improving system efficiency.

[0030] In summary, this invention improves the energy release process structure of the compressed carbon dioxide energy storage system. After one expansion, the pressure of the high-pressure carbon dioxide decreases to atmospheric pressure, enabling it to generate electricity while simultaneously producing low-temperature cold energy. This also saves on heat storage consumption, with the remaining heat stored used for medium- and low-temperature cascade heating, thus achieving combined cooling, heating, and power (CCHP). This invention also provides an integrated heat-driven CCHP subsystem with switchable power generation / cooling modes. It highly integrates the organic Rankine cycle and the jet refrigeration cycle, reducing investment costs and space occupation. By flexibly and efficiently converting excess heat energy into electricity or cold energy, it enhances the flexibility of the system's CCHP capabilities. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the offshore multi-energy supply system based on constant pressure compressed carbon dioxide energy storage in Example 1.

[0032] Figure 2 This is a schematic diagram of the offshore multi-energy supply system based on constant pressure compressed carbon dioxide energy storage in Example 2.

[0033] Explanation of reference numerals in the attached drawings: 1 - Gas reservoir, 2 - Electric motor, 3 - First compressor, 4 - First cooler, 5 - Second compressor, 6 - Second cooler, 7 - Low-temperature storage tank, 8 - High-temperature storage tank, 9 - First reversing valve, 10 - Carbon dioxide pipeline, 11 - Second reversing valve, 12 - First condenser, 13 - First seawater pump, 14 - Liquid storage tank, 15 - First working fluid pump, 16 - First evaporator, 17 - Second seawater pump, 18 - Preheater, 19 - Heater, 20 - First turbine, 21 - First generator, 22 - Cooling heat exchanger, 23 - First heating heat exchanger, 24 - Second heating heat exchanger, 25 - Second turbine, 26 - Second generator, 27 - Second condenser, 28 - Third seawater pump, 29 - Second working fluid pump, 30 - Ejector, 31 - Throttling valve, 32 - Second evaporator. Detailed Implementation

[0034] To provide a better understanding of the structural features and effects of the present invention, the present invention will be clearly and completely described below in conjunction with the embodiments and accompanying drawings.

[0035] Example 1

[0036] See Figure 1 A marine multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage includes: a working fluid storage device, a thermal energy storage device, a charging process module, a gas-liquid conversion circuit, a discharge process module, a cold energy supply module, and a thermal energy supply module.

[0037] Working fluid storage device: used for constant pressure storage of carbon dioxide; including a gas storage bladder 1 and several parallel connected liquid storage bags 14; wherein, the gas storage bladder 1 is used to store low-pressure gaseous carbon dioxide, and the liquid storage bags 14 are used to store high-pressure liquid carbon dioxide.

[0038] Thermal energy storage device: used to store the heat of compression generated by carbon dioxide after compression; including a low-temperature storage tank 7 and a high-temperature storage tank 8; wherein, the low-temperature storage tank 7 is used to store low-temperature heat storage medium, and the high-temperature storage tank 8 is used to store high-temperature heat storage medium.

[0039] Charging process module: used to convert offshore wind power and other new energy power generation into pressure energy and thermal energy of carbon dioxide; including an electric motor 2, a first compressor 3, a first cooler 4, a second compressor 5, and a second cooler 6, all installed on the offshore platform; the power outlet of the offshore wind power and other new energy power generation device is connected to the power inlet of the electric motor 2, and the power output shaft of the electric motor 2 is connected to the power input shaft of the first compressor 3 and the second compressor 5. The offshore wind power and other new energy power generation device supplies power to the electric motor 2, and the electric motor 2 converts electrical energy into mechanical energy, driving the first compressor 3 and the second compressor 5 to rotate; the outlet of the air storage bladder 1 is connected to the inlet of the first compressor 3, and the outlet of the first compressor 3 is connected to the first cooler 4. The high-temperature side inlet is connected, the high-temperature side outlet of the first cooler 4 is connected to the inlet of the second compressor 5, and the outlet of the second compressor 5 is connected to the high-temperature side inlet of the second cooler 6; the outlet of the low-temperature storage tank 7 is connected to the low-temperature side inlet of the second cooler 6 and the low-temperature side inlet of the first cooler 4 respectively, and the low-temperature side outlet of the second cooler 6 and the low-temperature side outlet of the first cooler 4 are both connected to the inlet of the high-temperature storage tank 8; the low-pressure gaseous carbon dioxide from the gas storage bladder 1 is compressed in two stages by the first compressor 3 and the second compressor 5 to a high-temperature and high-pressure state, and the high-temperature carbon dioxide exchanges heat with the heat storage medium from the low-temperature storage tank 7 in the first cooler 4 and the second cooler 6 respectively, and the heat storage medium is stored in the high-temperature storage tank 8 after being heated.

[0040] Gas-liquid conversion circuit: used to transport high-pressure gaseous carbon dioxide from the offshore platform to the seabed and liquefy it, and to vaporize high-pressure liquid carbon dioxide from the seabed and transport it to the offshore platform; including a first condenser 12, a first seawater pump 13, a first working fluid pump 15, a first evaporator 16, a second seawater pump 17, and a bidirectional carbon dioxide transport pipeline; the bidirectional carbon dioxide transport pipeline includes a first reversing valve 9, a carbon dioxide pipeline 10, and a second reversing valve 11; wherein, the carbon dioxide pipeline 10 is used for bidirectional transport of high-pressure carbon dioxide, and both the first reversing valve 9 and the second reversing valve 11 are used to change the flow direction of carbon dioxide.

[0041] When gaseous carbon dioxide from the offshore platform is sent to underwater storage, the high-temperature side outlet of the second cooler 6 is connected to one end of the carbon dioxide pipeline 10 through the first reversing valve 9, and the other end of the carbon dioxide pipeline 10 is connected to the high-temperature side inlet of the first condenser 12 through the second reversing valve 11. The high-temperature side outlet of the first condenser 12 is connected to the inlet of the liquid storage tank 14. The first seawater pump 13 draws deep-sea low-temperature seawater, and the subsea pipeline is connected to the low-temperature side inlet of the first condenser 12 through the first seawater pump 13. The gaseous carbon dioxide from the offshore platform enters the carbon dioxide pipeline 10 through the first reversing valve 9, flows to the seabed, enters the high-temperature side of the first condenser 12 through the second reversing valve 11, is cooled by the deep-sea low-temperature seawater, condenses into liquid, and then enters and is stored through the single inlet and outlet of the liquid storage tank 14.

[0042] When the liquid carbon dioxide stored on the seabed is returned to the offshore platform, the outlet of the storage tank 14 is connected to the low-temperature inlet of the first evaporator 16 via the first working fluid pump 15. The low-temperature outlet of the first evaporator 16 is connected to one end of the carbon dioxide pipeline 10 via the second reversing valve 11. The other end of the carbon dioxide pipeline 10 is connected to the inlet of the discharge process module via the inlet of the first reversing valve 9. The second seawater pump 17 draws in high-temperature shallow seawater, and the shallow sea pipeline is connected to the high-temperature inlet of the first evaporator 16 via the second seawater pump 17. The liquid carbon dioxide flows out from the single inlet and outlet of the storage tank 14, is pressurized by the first working fluid pump 15, enters the first evaporator 16, is heated by the high-temperature shallow seawater, evaporates into a gaseous state, enters the carbon dioxide pipeline 10 via the second reversing valve 11, flows to the offshore platform, and enters the discharge process module via the first reversing valve 9.

[0043] Discharge process module: used to convert stored pressure energy and thermal energy back into electrical energy; includes a preheater 18, a heater 19, a first turbine 20, and a generator 21; the low-temperature side outlet of the first evaporator 16 is connected to one end of the carbon dioxide pipeline 10 through a second reversing valve 11, the other end of the carbon dioxide pipeline 10 is connected to the low-temperature side inlet of the preheater 18 through a first reversing valve 9, the low-temperature side outlet of the preheater 18 is connected to the low-temperature side inlet of the heater 19, the low-temperature side outlet of the heater 19 is connected to the inlet of the first turbine 20, and the power output shaft of the first turbine 20 is connected to the power input shaft of the generator 21; the first outlet of the high-temperature storage tank 8 is connected to the... The high-temperature side inlet of heater 19 is connected to the high-temperature side outlet of heater 19, which is connected to the high-temperature side inlet of preheater 18. The high-temperature side outlet of preheater 18 is connected to the inlet of cryogenic storage tank 7. The high-pressure liquid carbon dioxide stored in the liquid storage bag 14 is converted into gaseous state through the gas-liquid conversion circuit and then transported to the offshore platform. The high-pressure gaseous carbon dioxide enters preheater 18 and heater 19 in sequence and is heated to a high temperature by a part of the heat storage medium from high-temperature storage tank 8. Then it enters the first turbine 20, where it expands and does work, driving generator 21 to rotate and generate electricity for power supply. After releasing all the heat, the heat storage medium enters cryogenic storage tank 7 for storage.

[0044] Cold energy supply module: The low-temperature cold energy generated by the expansion of carbon dioxide in the discharge process module is used for cooling; including a cooling heat exchanger 22; the outlet of the first turbine 20 is connected to the low-temperature side inlet of the cooling heat exchanger 22, and the low-temperature side outlet of the cooling heat exchanger 22 is connected to the inlet of the gas storage bladder 1; after the high-pressure carbon dioxide expands to atmospheric pressure in the first turbine 20, the temperature of the carbon dioxide at its outlet is as low as zero, generating low-temperature cold energy. The refrigerant flows through the high-temperature side of the cooling heat exchanger 22 to exchange heat with the low-temperature carbon dioxide for cooling.

[0045] The heat supply module utilizes the remaining heat stored after heating carbon dioxide in the discharge process module for heating. It includes a first heat exchanger 23 and a second heat exchanger 24. The second outlet of the high-temperature storage tank 8 is connected to the high-temperature side inlet of the first heat exchanger 23, the high-temperature side outlet of the first heat exchanger 23 is connected to the high-temperature side inlet of the second heat exchanger 24, and the high-temperature side outlet of the second heat exchanger 24 is connected to the high-temperature side inlet of the preheater 18. Since the discharge process module does not fully utilize the heat stored in the high-temperature storage tank 8, the remaining heat energy can be used for heating. Heat is released in the first heat exchanger 23 and the second heat exchanger 24. Medium-temperature heat energy can be used in a thermal power generation system, while low-temperature heat energy can be directly used for heating or for a thermally driven refrigeration system or a thermal seawater desalination device, thereby achieving cascaded utilization of heat energy.

[0046] The offshore multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage improves the energy release process structure of the compressed carbon dioxide energy storage system, so that the pressure of high-pressure carbon dioxide is reduced to atmospheric pressure after one expansion, so that it generates low-temperature cold energy while generating electricity, and saves the stored heat energy. It can be used for medium-temperature and low-temperature cascade heating, so as to achieve the purpose of multi-energy supply of cooling, heating and power.

[0047] In the described working fluid storage device, both the gas storage bladder 1 and the liquid storage bag 14 are made of multi-layered flexible materials, allowing their volume to vary and thus maintaining a constant internal pressure using external environmental pressure. The gas storage bladder 1 floats on the sea surface using buoyancy, without occupying space on the offshore platform. Its bottom is in contact with seawater and can be cooled to ambient temperature by the seawater. The liquid storage device uses a parallel structure of multiple liquid storage bags 14, moored on the seabed (below 450 meters from sea level), with carbon dioxide entering and exiting from its bottom. Mooring the high-pressure liquid storage device on the seabed increases the density of carbon dioxide through liquefaction, achieving reliable ballast. Constant pressure storage of liquid carbon dioxide is achieved using seawater hydrostatic pressure and flexible materials, with its internal pressure remaining constant at above 4.5 MPa. The parallel arrangement of multiple small-volume liquid storage bags 14 reduces longitudinal pressure variations compared to a single liquid storage bag 14, while preventing the entire system from failing due to the rupture of a single liquid storage bag 14, thus improving robustness. The multi-layered structure of the liquid storage bags 14 improves reliability in complex underwater environments, and the bottom-side single-sided carbon dioxide entry and exit design improves sealing.

[0048] In the thermal energy storage device, the heat storage medium is pressurized water or heat transfer oil; the high-temperature storage tank 8 is insulated by an insulation layer wrapped around its outer perimeter and is placed on an offshore platform; the low-temperature storage tank 7 does not require insulation and can be placed on an offshore platform or float on the sea surface, with additional buoyancy support provided by the air bladder 1.

[0049] In the gas-liquid conversion circuit, the shallow sea high-temperature seawater is drawn from the shallow sea (depth less than 100 meters) through the second seawater pump 17, and its temperature is higher than 20°C; the deep sea low-temperature seawater is drawn from the vicinity of the liquid storage tank 14 or a deeper location (depth greater than 450 meters) through the first seawater pump 13, and its temperature is lower than 10°C.

[0050] In the cold energy supply module, the high-temperature side of the cooling heat exchanger 22 is a refrigerant used to transport the cold energy generated at the outlet of the first turbine 20; the refrigerant can be an aqueous solution of ethylene glycol or a calcium chloride solution.

[0051] In the heat energy supply module, the thermal power generation system is one of the following: organic Rankine cycle, organic flash cycle, carbon dioxide power cycle, etc.; the heat-driven refrigeration system is one of the following: absorption refrigeration, jet refrigeration, etc.; and the thermal seawater desalination device is one of the following: multi-stage flash seawater desalination device, low-temperature multi-effect distillation seawater desalination device, etc.

[0052] This invention also provides an operation method for a marine multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage, including an energy storage (charging) process and an energy release (discharging, cooling, and heating) process:

[0053] During the energy storage process, the electric motor 2 is powered by new energy power generation devices such as offshore wind power to drive the compressor to compress the low-pressure gaseous carbon dioxide in the gas storage bag 1 in two stages to a high-pressure state. The heat energy generated by the compression of carbon dioxide is absorbed by the heat storage medium in the low-temperature storage tank 7. After the temperature of the heat storage medium rises, it is stored in the high-temperature storage tank 8. The low-temperature high-pressure carbon dioxide after releasing heat is sent to the seabed through the carbon dioxide bidirectional transport pipeline. It is cooled by the low-temperature seawater in the first condenser 12. After the high-pressure carbon dioxide is completely condensed into liquid, it is stored in the liquid storage bag 14.

[0054] During the energy release process, the high-pressure liquid carbon dioxide stored in the liquid storage tank 14 is pressurized by the first working fluid pump 15 and transported to the first evaporator 16. After absorbing heat from the high-temperature shallow seawater, it evaporates into a gaseous state and is then transported to the offshore platform through a bidirectional carbon dioxide transport pipeline. It then enters the preheater 18 and heater 19, where it is heated to a high temperature by the heat storage medium stored in the high-temperature storage tank 8. It then enters the first turbine 20 to expand and do work, driving the generator 21 to generate electricity. After the carbon dioxide at the outlet of the first turbine 20 expands to a low pressure, its own temperature drops to below zero and enters the cooling heat exchanger 2. 2. The heat storage medium releases cold energy to the refrigerant and enters the gas storage bladder 1 after its own temperature rises. Part of the heat storage medium at the outlet of the high-temperature storage tank 8 enters the heater 19 to heat carbon dioxide, and the remaining heat storage heat energy is used for heating. That is, another part of the heat storage medium at the outlet of the heat storage tank 8 enters the first heat exchanger 23 and the second heat exchanger 24 successively, releasing medium-temperature heat energy and low-temperature heat energy successively, realizing the cascade utilization of heat energy. After the heat storage medium flows through the heater 19 and the second heat exchanger 24, it mixes and enters the preheater 18. After the temperature is further reduced, it is stored in the low-temperature storage tank 7.

[0055] Example 2

[0056] See Figure 2 In addition to the system structure of Embodiment 1, the marine multi-energy supply system based on constant pressure compressed carbon dioxide energy storage also includes an integrated thermal-driven combined cooling and power subsystem that synergistically utilizes residual thermal storage as a heat source and low-temperature seawater as a cold source.

[0057] The remaining heat storage can be obtained from the first heat exchanger 23 or the second heat exchanger 24. Figure 2 Taking the first heating heat exchanger 23 as an example;

[0058] The integrated heat-driven combined cooling and power subsystem consists of an organic Rankine cycle and a jet refrigeration cycle connected to a heat energy supply module via a first heat exchanger 23 or a second heat exchanger 24. This subsystem further converts the remaining stored thermal energy into electrical or cooling energy. Specifically, the organic Rankine cycle converts the stored thermal energy into electrical energy, while the jet refrigeration cycle converts it into cooling energy. The organic Rankine cycle includes a first heat exchanger 23, a second turbine 25, a second generator 26, and a second refrigeration unit. The system includes a condenser 27, a third seawater pump 28, and a second working fluid pump 29; the jet refrigeration cycle includes a first heating heat exchanger 23, a second condenser 27, a third seawater pump 28, a second working fluid pump 29, an ejector 30, a throttle valve 31, and a second evaporator 32; the two systems share the first heating heat exchanger 23, the second condenser 27, the third seawater pump 28, and the second working fluid pump 29; the operating mode of the first heating heat exchanger 23 is changed by diverting the organic working fluid at the low-temperature side outlet, including a thermal power generation mode and a thermal refrigeration mode.

[0059] In the thermal power generation mode, the low-temperature side outlet of the first heat exchanger 23 is connected to the inlet of the second turbine 25, the outlet of the second turbine 25 is connected to the high-temperature side inlet of the second condenser 27, and the high-temperature side outlet of the second condenser 27 is connected to the low-temperature side inlet of the first heat exchanger 23 through the second working fluid pump 29, forming an organic Rankine cycle; the power output shaft of the second turbine 25 is connected to the power input shaft of the second generator 26, driving the generator 26 to generate electricity.

[0060] In the hot-cooling operation mode, the low-temperature outlet of the first heating heat exchanger 23 is connected to the high-pressure inlet of the ejector 30, the low-temperature outlet of the second evaporator 32 is connected to the low-pressure inlet of the ejector 30, and the outlet of the ejector 30 is connected to the high-temperature inlet of the second condenser 27. The high-temperature outlet of the second condenser 27 is split, with one part connected to the low-temperature inlet of the second evaporator 32 through the throttle valve 31, and the other part connected to the low-temperature inlet of the first heating heat exchanger 23 through the second working fluid pump 29, thus forming a jet refrigeration cycle. The high-temperature side of the second evaporator 32 is a refrigerant used to transport the cold energy generated by the jet refrigeration cycle. The refrigerant can be an aqueous solution of ethylene glycol or a calcium chloride solution.

[0061] The low-temperature side inlet of the second condenser 27 is connected to a seawater pipeline via a third seawater pump 28. The third seawater pump 28 draws low-temperature seawater and delivers it to the low-temperature side of the second condenser 27. The depth of the water intake is greater than 100 meters, which is used to provide low-temperature seawater as a cold source in both thermal power generation and thermal cooling modes. The working fluid in the integrated thermal-driven combined cooling and power generation subsystem is one of organic working fluids such as R245fa and R134a.

[0062] By utilizing thermal energy in stages, the thermal energy can be further converted into electrical or cooling energy, enabling switching between heating, power supply, and cooling, and improving the flexibility of the system's multi-energy supply. By highly integrating the organic Rankine cycle and the jet refrigeration cycle and sharing equipment, investment costs are reduced while minimizing the space required on the offshore platform. The second condenser 27 uses low-temperature seawater as a cold source, further utilizing ocean thermal energy difference and improving the efficiency of the integrated thermal-driven combined cooling and power subsystem.

Claims

1. A marine multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage, characterized in that, include: Working fluid storage device, thermal energy storage device, charging process module, gas-liquid conversion circuit, discharging process module, cold energy supply module and thermal energy supply module; Working fluid storage device: including a gas storage bag (1) and several parallel connected liquid storage bags (14); Thermal energy storage device: including low temperature storage tank (7) and high temperature storage tank (8); Charging process module: used to convert marine new energy power generation into pressure energy and thermal energy of carbon dioxide; including an electric motor (2), a first compressor (3), a first cooler (4), a second compressor (5), and a second cooler (6) electrically connected to the marine new energy power generation device; the power output shaft of the electric motor (2) is connected to the power input shaft of the first compressor (3) and the second compressor (5); the outlet of the gas storage bag (1) is connected to the inlet of the first compressor (3), the outlet of the first compressor (3) is connected to the inlet of the second compressor (5) through the high temperature side of the first cooler (4), and the outlet of the second compressor (5) is connected to the high temperature side inlet of the second cooler (6); the outlet of the low temperature storage tank (7) is connected to the low temperature side inlet of the second cooler (6) and the low temperature side inlet of the first cooler (4) respectively, and the low temperature side outlet of the second cooler (6) and the low temperature side outlet of the first cooler (4) are both connected to the inlet of the high temperature storage tank (8); Gas-liquid conversion circuit: used to transport high-pressure gaseous carbon dioxide from the offshore platform to the seabed and liquefy it, and to gasify high-pressure liquid carbon dioxide from the seabed and transport it to the offshore platform; including a first condenser (12), a first seawater pump (13), a first working fluid pump (15), a first evaporator (16), a second seawater pump (17), and a carbon dioxide bidirectional transport pipeline; the high-temperature side outlet of the second condenser (6) is connected to the high-temperature side inlet of the first condenser (12) through the carbon dioxide bidirectional transport pipeline, and the high-temperature side outlet of the first condenser (12) is connected to the inlet of the liquid storage tank (14); the low-temperature side inlet of the first condenser (12) is connected to the seabed pipeline through the first seawater pump (13); the outlet of the liquid storage tank (14) is connected to the low-temperature side inlet of the first evaporator (16) through the first working fluid pump (15), and the low-temperature side outlet of the first evaporator (16) is connected to the inlet of the discharge process module through the carbon dioxide bidirectional transport pipeline; the high-temperature side inlet of the first evaporator (16) is connected to the shallow sea pipeline through the second seawater pump (17); Discharge process module: used to convert stored pressure energy and thermal energy back into electrical energy; including preheater (18), heater (19), first turbine (20) and generator (21); the low temperature side outlet of the first evaporator (16) is connected to the low temperature side inlet of the preheater (18) through a bidirectional carbon dioxide transport pipeline, the low temperature side outlet of the preheater (18) is connected to the low temperature side inlet of the heater (19), the low temperature side outlet of the heater (19) is connected to the inlet of the first turbine (20), and the power output shaft of the first turbine (20) is connected to the power input shaft of the generator (21); the first outlet of the high temperature tank (8) is connected in series with the high temperature side of the heater (19) and the high temperature side of the preheater (18), and the high temperature side outlet of the preheater (18) is connected to the inlet of the low temperature tank (7); the bidirectional carbon dioxide transport pipeline includes a first reversing valve (9), a carbon dioxide pipeline (10), and a second reversing valve (11); the two ends of the carbon dioxide pipeline (10) are respectively connected to the first reversing valve (9) and the second reversing valve (11); Cold energy supply module: The low-temperature cold energy generated after the expansion of carbon dioxide is used for cooling; including a cooling heat exchanger (22), the outlet of the first turbine (20) is connected to the low-temperature side inlet of the cooling heat exchanger (22), and the low-temperature side outlet of the cooling heat exchanger (22) is connected to the inlet of the gas storage bag (1); Heat supply module: The remaining heat after heating carbon dioxide is used for heating; including a first heat exchanger (23) and a second heat exchanger (24), the second outlet of the high temperature tank (8) is connected in series with the high temperature side of the first heat exchanger (23) and the high temperature side of the second heat exchanger (24), the outlet of the high temperature side of the second heat exchanger (24) is connected to the high temperature side inlet of the preheater (18); the first heat exchanger (23) releases medium temperature heat energy for the thermal power generation system, and the second heat exchanger (24) releases low temperature heat energy for heating or for the thermal drive refrigeration system or thermal seawater desalination device, so as to realize the cascade utilization of heat energy; The system also includes an integrated thermal-driven combined cooling and power subsystem that uses the residual heat storage from the first heat exchanger (23) or the second heat exchanger (24) as a heat source and low-temperature seawater as a cold source. The subsystem includes an organic Rankine cycle for converting the stored thermal energy into electrical energy and a jet refrigeration cycle for converting the stored thermal energy into cold energy.

2. The marine multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage according to claim 1, characterized in that: The organic Rankine cycle includes a second turbine (25), a second generator (26), a second condenser (27), a third seawater pump (28), and a second working fluid pump (29). In the thermal power generation mode, the first outlet on the low-temperature side of the first heat exchanger (23) or the second heat exchanger (24) is connected to the inlet of the second turbine (25), the outlet of the second turbine (25) is connected to the inlet on the high-temperature side of the second condenser (27), and the outlet on the high-temperature side of the second condenser (27) is connected to the inlet on the low-temperature side of the first heat exchanger (23) or the second heat exchanger (24) through the second working fluid pump (29), thus forming an organic Rankine cycle. The power output shaft of the second turbine (25) is connected to the power input shaft of the second generator (26). The jet refrigeration cycle includes a second condenser (27), a third seawater pump (28), a second working fluid pump (29), an ejector (30), a throttle valve (31), and a second evaporator (32). In the hot refrigeration mode, the second outlet on the low-temperature side of the first heating heat exchanger (23) or the second heating heat exchanger (24) is connected to the high-pressure inlet of the ejector (30), the outlet on the low-temperature side of the second evaporator (32) is connected to the low-pressure inlet of the ejector (30), the outlet of the ejector (30) is connected to the high-temperature side inlet of the second condenser (27), and the outlet on the high-temperature side of the second condenser (27) is split, with one part connected to the low-temperature side inlet of the second evaporator (32) through the throttle valve (31), and the other part connected to the low-temperature side inlet of the first heating heat exchanger (23) or the second heating heat exchanger (24) through the second working fluid pump (29), thus forming a jet refrigeration cycle. The high-temperature side of the second evaporator (32) is a refrigerant used to transport the cold energy generated by the jet refrigeration cycle.

3. The offshore multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage according to claim 2, characterized in that: The low-temperature side inlet of the second condenser (27) is connected to a seawater pipeline through a third seawater pump (28), and the second condenser (27) uses low-temperature seawater as a cold source.

4. The marine multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage according to claim 1, characterized in that: Both the air storage bag (1) and the liquid storage bag (14) are made of multi-layered flexible materials.

5. The marine multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage according to claim 1, characterized in that: The heat storage medium in both the low-temperature storage tank (7) and the high-temperature storage tank (8) is pressurized water or heat transfer oil.

6. The marine multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage according to claim 1, characterized in that: The high-temperature side of the cooling heat exchanger (22) is a refrigerant used to transport the cold energy generated at the outlet of the first turbine (20).

7. The operation method of the offshore multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage according to claim 1, characterized in that: Includes energy storage and energy release processes; During the energy storage process, the offshore new energy power generation device is used to power the motor (2) to drive the compressor to compress the low-pressure gaseous carbon dioxide in the gas storage bag (1) in two stages to a high-pressure state. The heat energy generated by the compression of carbon dioxide is absorbed by the heat storage medium in the low-temperature storage tank (7). After the temperature of the heat storage medium rises, it is stored in the high-temperature storage tank (8). The low-temperature high-pressure carbon dioxide after heat release is sent to the seabed through the carbon dioxide bidirectional transport pipeline. It is cooled by the deep-sea low-temperature seawater in the first condenser (12). After the high-pressure carbon dioxide is completely condensed into liquid, it is stored in the liquid storage bag (14). During the energy release process, the high-pressure liquid carbon dioxide stored in the storage tank (14) is pressurized by the first working fluid pump (15) and transported to the first evaporator (16). After absorbing the heat of the high-temperature seawater in the shallow sea, it evaporates into a gaseous state and is then transported to the offshore platform through the carbon dioxide bidirectional transport pipeline. It then enters the preheater (18) and heater (19) in succession, and is heated to a high temperature by the heat storage medium stored in the high-temperature storage tank (8). Then it enters the first turbine (20) to expand and do work, driving the generator (21) to generate electricity. After the carbon dioxide at the outlet of the first turbine (20) expands to a low pressure, its own temperature decreases. When the temperature drops below zero, the cold energy is released to the refrigerant in the cooling heat exchanger (22), and after its own temperature rises, it enters the gas storage bladder (1) for storage. Part of the heat storage medium at the outlet of the high-temperature storage tank (8) enters the heater (19) to be used to heat carbon dioxide, and the other part enters the first heat exchanger (23) and the second heat exchanger (24) in succession, releasing medium-temperature heat energy and low-temperature heat energy in succession, realizing the cascade utilization of heat energy. After the heat storage medium flows through the heater (19) and the second heat exchanger (24) and mixes, it enters the preheater (18), and after the temperature is further reduced, it is stored in the low-temperature storage tank (7).

Images