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

Abstract

The invention discloses an offshore multi-energy combined supply system based on constant-pressure compressed carbon dioxide energy storage and an operation method of the offshore multi-energy combined supply system. 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. By improving the energy release process structure of the compressed carbon dioxide energy storage system, the pressure of high-pressure carbon dioxide is reduced to normal pressure after primary expansion, so that low-temperature cold energy is generated while power is generated, consumption of stored heat is saved, residual stored heat is used for heat supply, the comprehensive utilization rate of energy is increased, and combined supply of cooling, heating and power is achieved; the system further comprises an integrated thermally-driven combined cooling and power supply subsystem capable of switching power generation / refrigeration modes, organic Rankine cycle and jet refrigeration cycle are highly integrated, investment cost and space occupation are reduced, redundant 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] The present application belongs to the technical field of new energy storage and multi-energy cogeneration, and particularly relates to an offshore multi-energy cogeneration system based on constant-pressure compressed carbon dioxide energy storage and an operation method thereof. BACKGROUND

[0002] In recent years, the installed capacity of offshore wind power in China has been rising continuously, and its large-scale development is of great significance to green power supply and low-carbon energy transformation in coastal and deep-sea areas. Although offshore wind power is more abundant than onshore wind power, its volatility can still weaken the resilience of the power grid when it is connected to the grid on a large scale. Therefore, it is necessary to configure "suitable" energy storage technology to ensure the consumption of offshore wind power and improve the economy of the system. On the other hand, the development of offshore energy islands, marine ranching and deep-sea aquaculture requires strategic synergy with low-temperature cold-chain logistics. The use of offshore new energy for centralized refrigeration and cooling can save costs and release cabin space by eliminating the need for refrigeration machines on fishing vessels. The construction of South China Sea islands and reefs and offshore integrated energy islands also requires heat and fresh water. Multi-stage flash distillation and multi-effect distillation technologies can use low-grade heat to produce fresh water. Therefore, if offshore renewable energy can be effectively utilized and converted into stable electricity, cold energy and heat energy, it will provide the necessary energy support for marine ranching, ocean islands and offshore energy islands. Chinese Patent No. CN116816649B proposes a multi-generation system for underwater compressed air energy storage, which can meet the multiple energy needs of cold, heat, electricity and fresh water. However, the system stores high-pressure compressed air underwater, which has a large buoyancy, making it difficult to achieve reliable ballast underwater. On the other hand, the system uses the compression heat of the energy storage process directly for other energy supply, and relies entirely on solar heat collection during the energy release process, making the scheme unsuitable for deep-sea platforms.

[0003] The compressed carbon dioxide energy storage system uses carbon dioxide as the working medium, has the advantages of long service life, high efficiency and low cost. It has become a research hotspot for new long-term energy storage technology and is expected to become a reliable offshore energy storage solution after improvement. Chinese Patent Application No. CN120062847A proposes an offshore constant-pressure compressed carbon dioxide energy storage system and method coupled with ocean temperature difference, which uses seawater static pressure to achieve constant-pressure storage of high-pressure carbon dioxide, and couples with ocean temperature difference to realize the gas-liquid phase change of carbon dioxide, thereby increasing the density of underwater high-pressure carbon dioxide and reducing the buoyancy effect. However, the system can only store and release electrical energy, which is not conducive to multi-energy cogeneration such as cold, heat and electricity, and other electrical equipment needs to be configured to meet the demand for multiple energy sources in deep-sea development and offshore energy islands. SUMMARY

[0004] In order to overcome the shortcomings of the existing technology that the energy release process can only output a single electrical energy and cannot achieve the combined supply of heat, cooling and electricity, the purpose of the present invention is to provide an offshore combined supply system and its operation method based on constant-pressure compressed carbon dioxide energy storage, which is aimed at deep-sea wind power consumption. By improving the energy release process structure of the compressed carbon dioxide energy storage system, the pressure of the high-pressure carbon dioxide is reduced to atmospheric pressure after a single expansion, so that it can generate low-temperature cold energy while generating electricity, and save the consumption of heat storage. The remaining stored heat is used for medium and low-temperature cascade heating, thereby achieving the combined supply of heat, cooling and electricity. The liquid storage bag is moored to the seabed and multiple liquid storage bags are arranged in parallel to reduce longitudinal pressure changes and improve reliability. At the same time, a two-way carbon dioxide transportation pipeline is used to transport high-pressure carbon dioxide between the offshore platform and the seabed, reducing pipeline investment. The present invention also provides an integrated heat-driven combined supply subsystem with switchable power generation / cooling mode, which highly integrates the organic Rankine cycle and the ejector refrigeration cycle to reduce investment cost and space occupancy. By flexibly and efficiently converting excess heat energy into electricity or cold energy, the flexibility of the system's combined supply is improved.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] An offshore multi-energy cogeneration system based on constant-pressure compressed carbon dioxide energy storage, including: 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;

[0007] Working medium storage device: including an air storage bag 1 and a plurality of liquid storage bags 14 connected in parallel;

[0008] Thermal energy storage device: including a low-temperature storage tank 7 and a 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 shafts of the first compressor 3 and the second compressor 5; the outlet of the air 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 inlet of the high-temperature side of the second cooler 6; the outlet of the low-temperature storage tank 7 is respectively connected to the low-temperature side inlet of the second cooler 6 and the low-temperature side inlet of the first cooler 4, 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;

[0010] Gas-liquid conversion loop: used for transporting high-pressure gaseous carbon dioxide on the offshore platform to the seabed and liquefying, and gasifying high-pressure liquid carbon dioxide on the seabed and transporting to the offshore platform; comprising a first condenser 12, a first seawater pump 13, a first working medium pump 15, a first evaporator 16, a second seawater pump 17, and a carbon dioxide bidirectional transportation pipeline; the high-temperature side outlet of the second cooler 6 is connected with the high-temperature side inlet of the first condenser 12 through the carbon dioxide bidirectional transportation pipeline, and the high-temperature side outlet of the first condenser 12 is connected with the inlet of the liquid storage bag 14; the low-temperature side inlet of the first condenser 12 is connected with the seabed pipeline through the first seawater pump 13; the outlet of the liquid storage bag 14 is connected with the low-temperature side inlet of the first evaporator 16 through the first working medium pump 15, and the low-temperature side outlet of the first evaporator 16 is connected with the inlet of the discharge process module through the carbon dioxide bidirectional transportation pipeline; the high-temperature side inlet of the first evaporator 16 is connected with the shallow sea pipeline through the second seawater pump 17;

[0011] Discharge process module: used for re-converting the stored pressure energy and heat energy into electric energy; comprising 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 with the low-temperature side inlet of the preheater 18 through the carbon dioxide bidirectional transportation pipeline, the low-temperature side outlet of the preheater 18 is connected with the low-temperature side inlet of the heater 19, the low-temperature side outlet of the heater 19 is connected with the inlet of the first turbine 20, and the power output shaft of the first turbine 20 is connected with the power input shaft of the generator 21; the first outlet of the high-temperature storage tank 8 is connected with the high-temperature side of the heater 19 and the high-temperature side of the preheater 18 in sequence, and the high-temperature side outlet of the preheater 18 is connected with the inlet of the low-temperature storage tank 7;

[0012] Cold energy supply module: used for supplying cold energy generated by the expansion of carbon dioxide; comprising a cold supply heat exchanger 22, the outlet of the first turbine 20 is connected with the low-temperature side inlet of the cold supply heat exchanger 22, and the low-temperature side outlet of the cold supply heat exchanger 22 is connected with the inlet of the gas storage bag 1;

[0013] Heat energy supply module: used for supplying the residual heat storage after heating carbon dioxide; comprising a first heat supply heat exchanger 23 and a second heat supply heat exchanger 24, the second outlet of the high-temperature storage tank 8 is connected with the high-temperature side of the first heat supply heat exchanger 23 and the high-temperature side of the second heat supply heat exchanger 24 in sequence, and the high-temperature side outlet of the second heat supply heat exchanger 24 is connected with the high-temperature side inlet of the preheater 18.

[0014] The system further comprises an integrated heat-driven combined cooling and power supply subsystem taking the residual heat storage from the first heat supply heat exchanger 23 or the second heat supply heat exchanger 24 as a heat source and low-temperature seawater as a cold source, which comprises an organic Rankine cycle for converting the heat storage heat energy into electric energy and an ejector refrigeration cycle for converting the heat storage heat energy into cold energy.

[0015] The organic Rankine cycle comprises a second turbine 25, a second generator 26, a second condenser 27, a third seawater pump 28, and a second working medium pump 29; in the heat power generation mode, the first outlet of the low-temperature side of the first or second heat supply heat exchanger 23 or 24 is connected with the inlet of the second turbine 25, the outlet of the second turbine 25 is connected with the inlet of the high-temperature side of the second condenser 27, and the outlet of the high-temperature side of the second condenser 27 is connected with the inlet of the low-temperature side of the first or second heat supply heat exchanger 23 or 24 through the second working medium pump 29, thereby forming the organic Rankine cycle; and the power output shaft of the second turbine 25 is connected with the power input shaft of the second generator 26.

[0016] The ejector refrigeration cycle comprises the second condenser 27, the third seawater pump 28, the second working medium pump 29, the ejector 30, the throttling valve 31, and the second evaporator 32; in the heat refrigeration mode, the second outlet of the low-temperature side of the first or second heat supply heat exchanger 23 or 24 is connected with the high-pressure inlet of the ejector 30, the outlet of the low-temperature side of the second evaporator 32 is connected with the low-pressure inlet of the ejector 30, the outlet of the ejector 30 is connected with the inlet of the high-temperature side of the second condenser 27, the outlet of the high-temperature side of the second condenser 27 is branched, one part is connected with the inlet of the low-temperature side of the second evaporator 32 through the throttling valve 31, and the other part is connected with the inlet of the low-temperature side of the first or second heat supply heat exchanger 23 or 24 through the second working medium pump 29, thereby forming the ejector refrigeration cycle; and the high-temperature side of the second evaporator 32 is the coolant for transporting the cold energy generated by the ejector refrigeration cycle.

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

[0018] The carbon dioxide bidirectional transportation pipeline comprises the first switching valve 9, the carbon dioxide pipeline 10, and the second switching valve 11; the carbon dioxide pipeline 10 is used for bidirectional transportation of high-pressure carbon dioxide, and the first switching valve 9 and the second switching valve 11 are used for changing the flow direction of the carbon dioxide.

[0019] The gas storage bag 1 and the liquid storage bag 14 are both made of multiple layers of flexible materials.

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

[0021] The high-temperature side of the cold supply heat exchanger 22 is the coolant for transporting the cold energy generated by the outlet of the first turbine 20.

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

[0023] The application also provides an operation method of the offshore multi-energy combined supply system based on constant-pressure compressed carbon dioxide energy storage.

[0024] In the energy storage process, the offshore new energy power generation device supplies power to the motor 2 to drive the compressor, and the low-pressure gaseous carbon dioxide in the gas bag 1 is compressed in two stages to a high-pressure state.

[0025] In the energy release process, the high-pressure liquid carbon dioxide stored in the liquid storage bag 14 is pressurized by the first working fluid pump 15 and delivered to the first evaporator 16, evaporates into a gaseous state after absorbing the heat of the shallow sea warm seawater, and then is delivered to the offshore platform through the carbon dioxide bidirectional transportation pipeline, and then enters the preheater 18 and the heater 19, is heated to a high-temperature state by the heat storage medium stored in the high-temperature storage tank 8, and then enters the first turbine 20 to expand and do work, driving the generator 21 to generate electricity; the carbon dioxide at the outlet of the first turbine 20 expands to a low pressure, and the temperature thereof decreases to below zero, and the carbon dioxide releases cold energy to the cold carrier in the cold heat exchanger 22, and then the temperature thereof increases and enters the gas bag 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 the carbon dioxide, and the other part enters the first heat supply heat exchanger 23 and the second heat supply heat exchanger 24 in sequence, and releases medium-temperature heat energy and low-temperature heat energy in sequence, so that the heat energy is utilized in stages; and the heat storage medium mixed after flowing through the heater 19 and the second heat supply heat exchanger 24 enters the preheater 18, and is stored in the low-temperature storage tank 7 after the temperature thereof is further reduced.

[0026] Compared with the prior art, the application has the following beneficial effects:

[0027] 1. The offshore multi-energy combined supply system based on constant-pressure compressed carbon dioxide energy storage provided by the application improves the structure of the energy release process of the compressed carbon dioxide energy storage system, 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, and the comprehensive utilization rate of energy is improved; the medium-temperature heat storage that is not used releases heat energy in two stages, so that the heat storage is utilized in stages, the medium-temperature heat energy can be used to drive a thermal power generation system, and the low-temperature heat energy can be used to drive a thermal method seawater desalination device or an absorption refrigeration device; the combination of the two realizes stable supply of cold, heat, electricity and other multiple energies based on offshore compressed carbon dioxide energy storage.

[0028] 2. The offshore multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage provided by the application uses a carbon dioxide two-way transportation pipeline to transport carbon dioxide between the offshore platform and the seabed, thereby reducing the cost of high-pressure pipelines; the liquid storage bag is moored to the seabed, and the density of carbon dioxide is increased through liquefaction, thereby realizing reliable ballast; the liquid storage bag is arranged in parallel by multiple small-volume liquid storage bags, which, compared with a single liquid storage bag, reduces the change in longitudinal pressure and prevents the entire system from failing due to damage to a certain liquid storage bag, thereby improving robustness; the liquid storage bag is made of multiple layers of flexible material, which improves reliability in complex underwater environments, and the bottom one-side carbon dioxide inlet and outlet design improves sealing.

[0029] 3. The offshore multi-energy supply system based on constant-pressure compressed carbon dioxide energy storage provided by the application provides an integrated heat-driven combined cooling and power supply subsystem capable of switching between power generation and refrigeration modes, which highly integrates an organic Rankine cycle and an ejector refrigeration cycle and shares equipment, thereby reducing investment costs and reducing the occupation of space on the offshore platform; by adjusting the flow rate of the organic working medium to the second turbine and the ejector, the system can switch between power supply and refrigeration, thereby improving the flexibility of multi-energy supply.

[0030] In summary, the application improves the energy release process structure of the compressed carbon dioxide energy storage system, reduces the pressure of high-pressure carbon dioxide to normal pressure after one-time expansion, generates low-temperature cold energy during power generation, saves the consumption of heat storage, and uses the remaining heat storage for medium and low temperature cascade heat supply, thereby realizing cold, heat and electricity multi-energy supply; the application also provides an integrated heat-driven combined cooling and power supply subsystem capable of switching between power generation and refrigeration modes, which highly integrates an organic Rankine cycle and an ejector refrigeration cycle, thereby reducing investment costs and space occupation; by flexibly and efficiently converting excess heat energy into electric energy or cold energy, the flexibility of multi-energy supply is improved. BRIEF DESCRIPTION OF DRAWINGS

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

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

[0033] Reference numerals: 1 - gas storage bag, 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 bag, 15 - first working medium 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 medium pump, 30 - ejector, 31 - throttling valve, 32 - second evaporator. DETAILED DESCRIPTION

[0034] In order to further understand and appreciate the structural features and effects of the present application, the following will combine examples and drawings to clearly and completely describe the present application.

[0035] Example 1

[0036] Reference Figure 1 , based on constant pressure compression carbon dioxide energy storage offshore multi-energy supply system, comprising: working medium storage device, heat energy storage device, charging process module, gas-liquid conversion circuit, discharging process module, cold energy supply module and heat energy supply module;

[0037] Working medium storage device: for constant pressure storage of carbon dioxide; including gas storage bag 1 and a plurality of parallel communication liquid storage bag 14; wherein, the gas storage bag 1 is used for storing low pressure gaseous carbon dioxide, the liquid storage bag 14 is used for storing high pressure liquid carbon dioxide.

[0038] Heat energy storage device: for storing the compression heat generated after the compression of carbon dioxide; including low-temperature storage tank 7 and high-temperature storage tank 8; wherein, the low-temperature storage tank 7 is used for storing low-temperature heat storage medium, and the high-temperature storage tank 8 is used for storing high-temperature heat storage medium.

[0039] Charging process module: for converting new energy power generation such as offshore wind power into pressure energy and heat energy of carbon dioxide; including electric motor 2, first compressor 3, first cooler 4, second compressor 5, second cooler 6 all arranged on offshore platform; the power outlet of offshore wind power generation device and new energy power generation device is connected with the power inlet of electric motor 2, the power output shaft of electric motor 2 is connected with the power input shaft of first compressor 3 and second compressor 5, the offshore wind power generation device is used to supply power to electric motor 2, electric motor 2 converts electric energy into mechanical energy to drive first compressor 3 and second compressor 5 to rotate; the outlet of gas storage bag 1 is connected with the inlet of first compressor 3, the outlet of first compressor 3 is connected with the high-temperature side inlet of first cooler 4, the high-temperature side outlet of first cooler 4 is connected with the inlet of second compressor 5, and the outlet of second compressor 5 is connected with the high-temperature side inlet of second cooler 6; the outlet of low-temperature storage tank 7 is connected with the low-temperature side inlet of second cooler 6 and the low-temperature side inlet of first cooler 4 respectively, and the low-temperature side outlet of second cooler 6 and the low-temperature side outlet of first cooler 4 are connected with the inlet of high-temperature storage tank 8; the low-pressure gaseous carbon dioxide in gas storage bag 1 is compressed by first compressor 3 and second compressor 5 to high-temperature and high-pressure state, and the high-temperature carbon dioxide exchanges heat with the heat storage medium from low-temperature storage tank 7 in first cooler 4 and second cooler 6 respectively, and the heated heat storage medium is stored in high-temperature storage tank 8.

[0040] Gas-liquid conversion loop: for transporting high-pressure gaseous carbon dioxide on offshore platform to seabed and liquefying, and gasifying high-pressure liquid carbon dioxide on seabed and transporting to offshore platform; including first condenser 12, first seawater pump 13, first working medium pump 15, first evaporator 16, second seawater pump 17, carbon dioxide bidirectional transportation pipeline; the carbon dioxide bidirectional transportation pipeline includes first reversing valve 9, carbon dioxide pipeline 10 and second reversing valve 11; wherein, the carbon dioxide pipeline 10 is used for bidirectional transportation of high-pressure carbon dioxide, and the first reversing valve 9 and the second reversing valve 11 are used for changing the flow direction of carbon dioxide.

[0041] When the gaseous carbon dioxide on offshore platform is sent to the storage under the sea, the high-temperature side outlet of second cooler 6 is connected with one end of carbon dioxide pipeline 10 through first reversing valve 9, the other end of carbon dioxide pipeline 10 is connected with the high-temperature side inlet of first condenser 12 through second reversing valve 11, and the high-temperature side outlet of first condenser 12 is connected with the inlet of liquid storage bag 14; the first seawater pump 13 extracts deep-sea low-temperature seawater, and the seabed pipeline is connected with the low-temperature side inlet of first condenser 12 through first seawater pump 13; the gaseous carbon dioxide on offshore platform enters carbon dioxide pipeline 10 through first reversing valve 9, flows to seabed, enters first condenser 12 high-temperature side through second reversing valve 11, is cooled by deep-sea low-temperature seawater, is condensed into liquid state, and then enters and is stored through the single inlet and outlet of liquid storage bag 14;

[0042] When the liquid carbon dioxide stored in the seabed is sent back to the offshore platform, the outlet of the liquid storage bag 14 is connected with the inlet of the low-temperature side of the first evaporator 16 through the first working medium pump 15, the outlet of the low-temperature side of the first evaporator 16 is connected with one end of the carbon dioxide pipeline 10 through the second reversing valve 11, and the other end of the carbon dioxide pipeline 10 is connected with the inlet of the discharge process module through the inlet of the first reversing valve 9; the shallow sea pipeline is connected with the inlet of the high-temperature side of the first evaporator 16 through the second seawater pump 17 which extracts the high-temperature seawater in the shallow sea; the liquid carbon dioxide flows out from the single inlet and outlet of the liquid storage bag 14, is pressurized by the first working medium pump 15, enters the first evaporator 16, is heated by the high-temperature seawater in the shallow sea, is evaporated into a gaseous state, enters the carbon dioxide pipeline 10 through the second reversing valve 11, flows to the offshore platform, and enters the discharge process module through the first reversing valve 9.

[0043] The discharge process module is used for re-converting the stored pressure energy and heat energy into electric energy, and includes a preheater 18, a heater 19, a first turbine 20 and a generator 21; the outlet of the low-temperature side of the first evaporator 16 is connected with one end of the carbon dioxide pipeline 10 through the second reversing valve 11, the other end of the carbon dioxide pipeline 10 is connected with the inlet of the low-temperature side of the preheater 18 through the first reversing valve 9, the outlet of the low-temperature side of the preheater 18 is connected with the inlet of the low-temperature side of the heater 19, the outlet of the low-temperature side of the heater 19 is connected with the inlet of the first turbine 20, and the power output shaft of the first turbine 20 is connected with the power input shaft of the generator 21; the first outlet of the high-temperature storage tank 8 is connected with the inlet of the high-temperature side of the heater 19, the outlet of the high-temperature side of the heater 19 is connected with the inlet of the high-temperature side of the preheater 18, and the outlet of the high-temperature side of the preheater 18 is connected with the inlet of the low-temperature storage tank 7; the high-pressure liquid carbon dioxide stored in the liquid storage bag 14 is converted into a gaseous state through the gas-liquid conversion circuit and is transported to the offshore platform, the high-pressure gaseous carbon dioxide enters the preheater 18 and the heater 19 in sequence and is heated to a high-temperature state by a part of the heat storage medium in the high-temperature storage tank 8 in sequence, then enters the first turbine 20, expands to do work in the first turbine 20, drives the generator 21 to rotate, generates electric energy for power supply, and the heat storage medium is stored in the low-temperature storage tank 7 after releasing the heat.

[0044] The cold energy supply module is used for supplying the low-temperature cold energy generated by the expansion of carbon dioxide in the discharge process module for cooling; includes a cooling heat exchanger 22; the outlet of the first turbine 20 is connected with the inlet of the low-temperature side of the cooling heat exchanger 22, and the outlet of the low-temperature side of the cooling heat exchanger 22 is connected with the inlet of the gas storage bag 1; the high-pressure carbon dioxide is expanded to normal pressure in the first turbine 20, the temperature of the carbon dioxide at the outlet is as low as minus, and low-temperature cold energy is generated, the heat exchanger 22 is flowed through by the heat carrier for heat exchange with the low-temperature carbon dioxide on the high-temperature side, and is used for cooling.

[0045] The thermal energy supply module uses the residual heat stored in the high-temperature storage tank 8 after the discharge process to supply heat. The thermal energy supply module includes a first heat supply heat exchanger 23 and a second heat supply 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 supply heat exchanger 23. The high-temperature side outlet of the first heat supply heat exchanger 23 is connected to the high-temperature side inlet of the second heat supply heat exchanger 24. The high-temperature side outlet of the second heat supply heat exchanger 24 is connected to the high-temperature side inlet of the preheater 18. The discharge process module does not fully utilize the heat energy stored in the high-temperature storage tank 8. The residual heat energy can be used to supply heat. The heat is released in the first heat supply heat exchanger 23 and the second heat supply heat exchanger 24. The medium-temperature heat energy can be used in a thermal power generation system. The low-temperature heat energy can be directly used to supply heat or used in a heat-driven refrigeration system or a thermal seawater desalination device. Thus, the heat energy is used in a cascade manner.

[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. The high-pressure carbon dioxide is reduced to atmospheric pressure after one-time expansion. The carbon dioxide generates low-temperature cold energy while generating electricity. The stored heat energy is saved and can be used for medium-temperature and low-temperature cascade heat supply. The purpose of cold, heat and electricity multi-energy supply is achieved.

[0047] In the working medium storage device, the gas storage bag 1 and the liquid storage bag 14 are both made of multiple layers of flexible material, so that the volume can change to maintain the internal pressure constant by using the external environmental pressure. The gas storage bag 1 floats on the sea level by using the buoyancy and does not occupy the space of the offshore platform. The bottom of the gas storage bag 1 is in contact with seawater and can be cooled to the environmental temperature by seawater. The liquid storage device adopts a parallel structure of multiple liquid storage bags 14 and is moored to the seabed (below 450 meters of sea level). Carbon dioxide enters and exits from the bottom of the liquid storage device. Mooring the high-pressure liquid storage device to the seabed increases the density of carbon dioxide by liquefaction, thereby achieving reliable ballast. The seawater static pressure and flexible material are used to achieve constant-pressure storage of liquid carbon dioxide. The internal pressure is constant at 4.5 MPa or above. Multiple small-volume liquid storage bags 14 are arranged in parallel. Compared with a single liquid storage bag 14, the longitudinal pressure change is reduced, and the failure of the entire system caused by the damage of a liquid storage bag 14 is prevented, thereby improving the robustness. The liquid storage bag 14 adopts a multi-layer structure to improve the reliability in the complex environment under the sea. The bottom unilateral inlet and outlet design of carbon dioxide improves the sealing performance.

[0048] In the thermal energy storage device, the thermal storage medium is pressurized water or heat-conducting oil. The high-temperature storage tank 8 is insulated by the insulation layer wrapped around the outer periphery of the high-temperature storage tank 8 and is placed on the offshore platform. The low-temperature storage tank 7 does not need to be insulated and can be placed on the offshore platform or floated on the sea surface and supported by the additional buoyancy provided by the gas storage bag 1.

[0049] In the gas-liquid conversion loop, the high-temperature seawater from the shallow sea (depth less than 100 meters) is pumped by the second seawater pump 17, and the temperature is higher than 20℃; the low-temperature seawater from the deep sea (depth greater than 450 meters) is pumped by the first seawater pump 13 near the liquid storage bag 14 or deeper, and the temperature is lower than 10℃.

[0050] In the cold energy supply module, the high-temperature side of the cold supply heat exchanger 22 is the carrier refrigerant, which is used to transport the cold energy generated by the first turbine 20; the carrier refrigerant can be glycol solution or calcium chloride solution.

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

[0052] The application also provides an operation method of the offshore multi-energy combined supply system based on constant-pressure compression carbon dioxide energy storage, including energy storage (charging) process and energy release (discharging, cold supply, heat supply) process:

[0053] In the energy storage process, the new energy power generation device such as offshore wind power supplies power to the motor 2 to drive the compressor to compress the low-pressure gaseous carbon dioxide in the gas bag 1 to a high-pressure state, the heat energy generated by the compressed carbon dioxide is absorbed by the heat storage medium in the low-temperature storage tank 7, the temperature of the heat storage medium is increased and stored in the high-temperature storage tank 8, and the low-temperature high-pressure carbon dioxide after heat release is sent to the seabed through the carbon dioxide two-way transportation pipeline, and the high-pressure carbon dioxide is completely condensed into liquid state in the first condenser 12 and stored in the liquid storage bag 14;

[0054] In the energy release process, the high-pressure liquid carbon dioxide stored in the storage bag 14 is pressurized by the first working fluid pump 15 and delivered to the first evaporator 16, absorbs the heat of the shallow sea high-temperature seawater, and evaporates into a gaseous state, and then is delivered to the offshore platform through the carbon dioxide two-way transportation pipeline, and then enters the preheater 18 and the heater 19, and is heated to a high-temperature state by the heat storage medium stored in the high-temperature storage tank 8, and then enters the first turbine 20 to expand and do work, driving the generator 21 to generate electricity; the carbon dioxide at the outlet of the first turbine 20 expands to a low pressure, and its temperature decreases to below zero, and releases cold energy to the cold carrier in the cold heat exchanger 22, and then enters the gas storage bag 1 after its temperature rises; part of the heat storage medium at the outlet of the high-temperature storage tank 8 enters the heater 19 to heat the carbon dioxide, and the remaining heat storage heat 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 supply heat exchanger 23 and the second heat supply heat exchanger 24 in turn, and releases medium-temperature heat and low-temperature heat in turn, realizing the cascade utilization of heat energy; and the heat storage medium flows through the heater 19 and the second heat supply heat exchanger 24, mixes, enters the preheater 18, and is stored in the low-temperature storage tank 7 after its temperature further decreases.

[0055] Embodiment 2

[0056] Referring to Figure 2 , in addition to including the system structure of embodiment 1, the offshore multi-energy cogeneration system based on constant-pressure compressed carbon dioxide energy storage also includes an integrated heat-driven combined cooling and power supply subsystem that cooperatively utilizes residual heat storage as a heat source and low-temperature seawater as a cold source;

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

[0058] The integrated heat-driven combined cooling and power supply subsystem is composed of an organic Rankine cycle and an ejector refrigeration cycle through common equipment, is connected with the heat energy supply module through the first heat supply heat exchanger 23 or the second heat supply heat exchanger 24, and is used for further converting the heat energy of the residual heat storage into electric energy or cold energy; wherein the organic Rankine cycle converts the heat energy of the heat storage into electric energy when working, and the ejector refrigeration cycle converts the heat energy of the heat storage into cold energy when working; the organic Rankine cycle includes the first heat supply heat exchanger 23, a second turbine 25, a second generator 26, a second condenser 27, a third seawater pump 28, and a second working fluid pump 29; the ejector refrigeration cycle includes the first heat supply heat exchanger 23, the second condenser 27, the third seawater pump 28, the second working fluid pump 29, an ejector 30, a throttling valve 31, and a second evaporator 32; both cycles share the first heat supply heat exchanger 23, the second condenser 27, the third seawater pump 28, and the second working fluid pump 29; the working mode of the organic working fluid at the low-temperature side outlet of the first heat supply heat exchanger 23 is changed by being divided into two streams, including a heat power generation working mode and a heat refrigeration working mode.

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

[0060] In the heat refrigeration mode, the low-temperature side outlet of the first heat supply heat exchanger 23 is connected with the high-pressure inlet of the ejector 30, the low-temperature side outlet of the second evaporator 32 is connected with the low-pressure inlet of the ejector 30, the outlet of the ejector 30 is connected with the high-temperature side inlet of the second condenser 27, the high-temperature side outlet of the second condenser 27 is branched, one part is connected with the low-temperature side inlet of the second evaporator 32 through the throttling valve 31, and the other part is connected with the low-temperature side inlet of the first heat supply heat exchanger 23 through the second working medium pump 29, and a jet refrigeration cycle is formed; the high-temperature side of the second evaporator 32 is a heat carrier, which is used for transporting the cold energy generated by the jet refrigeration cycle, and the heat carrier can be a glycol water solution or a calcium chloride solution.

[0061] The low-temperature side inlet of the second condenser 27 is connected with the seawater pipeline through the third seawater pump 28, low-temperature seawater is transported to the low-temperature side of the second condenser 27 by the third seawater pump 28, the depth of the water taking place is greater than 100 meters, and the low-temperature seawater is used as a cold source in the heat power generation mode and the heat refrigeration mode; the working medium in the integrated heat-driven cold and power cogeneration subsystem is one of R245fa, R134a and the like;

[0062] Through the step-by-step utilization of the stored heat energy, the heat energy can be further converted into electric energy or cold energy, the switching among heat supply, power supply and cold supply is realized, and the flexibility of the multi-energy cogeneration system is improved; the organic Rankine cycle and the jet refrigeration cycle are highly integrated and share equipment, the investment cost is reduced, and the space of the offshore platform is reduced; the second condenser 27 uses low-temperature seawater as a cold source, further utilizes the ocean temperature difference energy, and improves the efficiency of the integrated heat-driven cold and power cogeneration subsystem.

Claims

1. An offshore multi-energy cogeneration system based on constant pressure compressed carbon dioxide energy storage, characterized by: include: 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; The working medium storage device comprises an air storage bag (1) and a plurality of liquid storage bags (14) connected in parallel; Thermal energy storage device: comprising a low-temperature storage tank (7) and a high-temperature storage tank (8); The charging process module is used to convert offshore renewable energy power generation into pressure energy and thermal energy of carbon dioxide; it comprises 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 renewable energy power generation device; the power output shaft of the electric motor (2) is connected to the power input shafts of the first compressor (3) and the second compressor (5); the outlet of the air 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 inlet of the high-temperature side of the second cooler (6); the outlet of the low-temperature storage tank (7) is respectively connected to the inlet of the low-temperature side of the second cooler (6) and the inlet of the low-temperature side of the first cooler (4), and the outlet of the low-temperature side of the second cooler (6) and the outlet of the low-temperature side of the first cooler (4) are both connected to the inlet of the high-temperature storage tank (8); A gas-liquid conversion circuit is used to transport high-pressure gaseous carbon dioxide from an 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; it comprises 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 cooler (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 bag (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 bag (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); The discharge process module is used to convert the stored pressure energy and thermal energy 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 carbon dioxide bidirectional 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); A cold energy supply module uses the low-temperature cold energy generated by the expansion of carbon dioxide for cooling; it includes a cooling heat exchanger (22), wherein 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 air storage bag (1); A heat energy supply module uses the remaining stored heat after heating carbon dioxide for heat supply; it comprises a first heat supply heat exchanger (23) and a second heat supply heat exchanger (24); the second outlet of the high-temperature storage tank (8) is connected in series with the high-temperature side of the first heat supply heat exchanger (23) and the high-temperature side of the second heat supply heat exchanger (24); the high-temperature side outlet of the second heat supply heat exchanger (24) is connected to the high-temperature side inlet of the preheater (18).

2. The offshore multi-energy cogeneration system based on constant pressure compressed carbon dioxide energy storage according to claim 1 is characterized in that: The system also includes an integrated heat-driven combined cooling and power subsystem that uses the remaining heat storage from the first heat supply heat exchanger (23) or the second heat supply 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 heat energy into electrical energy and an ejector refrigeration cycle for converting the stored heat energy into cold energy.

3. The offshore multi-energy cogeneration system based on constant pressure compressed carbon dioxide energy storage according to claim 2 is 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 a thermal power generation mode, the first outlet of the low-temperature side of the first heat supply heat exchanger (23) or the second heat supply 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 of the high-temperature side of the second condenser (27), and the outlet of the high-temperature side of the second condenser (27) is connected to the inlet of the low-temperature side of the first heat supply heat exchanger (23) or the second heat supply heat exchanger (24) through the second working fluid pump (29), thereby 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 comprises 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 heat-cooling working mode, the second outlet on the low-temperature side of the first heat supply heat exchanger (23) or the second heat supply heat exchanger (24) is connected to the high-pressure inlet of the ejector (30), the low-temperature side outlet 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 high-temperature side outlet of the second condenser (27) is split, one part of which is connected to the low-temperature side inlet of the second evaporator (32) through the throttle valve (31), and the other part is connected to the low-temperature side inlet of the first heat supply heat exchanger (23) or the second heat supply heat exchanger (24) through the second working fluid pump (29), thereby forming a jet refrigeration cycle; the high-temperature side of the second evaporator (32) is a coolant for transporting cold energy generated by the jet refrigeration cycle.

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

5. The offshore multi-energy cogeneration system based on constant pressure compressed carbon dioxide energy storage according to claim 1 is characterized in that: The carbon dioxide bidirectional transport pipeline comprises 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).

6. The offshore multi-energy cogeneration system based on constant pressure compressed carbon dioxide energy storage according to claim 1 is characterized in that: The air storage bag (1) and the liquid storage bag (14) are both made of multi-layer flexible materials.

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

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

9. The offshore multi-energy cogeneration system based on constant pressure compressed carbon dioxide energy storage according to claim 1, characterized in that: In the heat energy supply module, the first heat supply heat exchanger (23) releases medium-temperature heat energy for a thermal power generation system, and the second heat supply heat exchanger (24) releases low-temperature heat energy for heating or for a heat-driven refrigeration system or a thermal seawater desalination device, thereby realizing cascade utilization of heat energy.

10. The method for operating an offshore multi-energy cogeneration system based on constant pressure compressed carbon dioxide energy storage according to claim 1, characterized in that: Including energy storage process and energy release process; During the energy storage process, the offshore new energy power generation device is used to supply power to the electric motor (2) to drive the compressor to perform two-stage compression on the low-pressure gaseous carbon dioxide in the gas storage bag (1) until it reaches a high-pressure state. The heat energy generated by the compressed carbon dioxide is absorbed by the heat storage medium in the low-temperature storage tank (7). The heat storage medium is stored in the high-temperature storage tank (8) after the temperature is increased. The low-temperature and high-pressure carbon dioxide after heat release is sent to the seabed through the carbon dioxide bidirectional transport pipeline, cooled by the deep-sea low-temperature seawater in the first condenser (12), and the high-pressure carbon dioxide is completely condensed into a liquid state and then stored in the liquid storage bag (14). During the energy release process, the high-pressure liquid carbon dioxide stored in the liquid storage bag (14) is pressurized by the first working fluid pump (15) and then transported to the first evaporator (16). After absorbing the heat of the shallow sea water, it evaporates into a gaseous state. It is then transported to the offshore platform through the carbon dioxide bidirectional transport pipeline, enters the preheater (18) and the heater (19) in succession, and 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 perform 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. To below zero, it releases cold energy to the refrigerant in the cold supply heat exchanger (22), and after its own temperature rises, it enters the air storage bag (1) for storage; a part of the heat storage medium at the outlet of the high-temperature storage tank (8) enters the heater (19) and is used to heat carbon dioxide, and the other part enters the first heat supply heat exchanger (23) and the second heat supply heat exchanger (24) successively, successively releasing medium-temperature heat energy and low-temperature heat energy, realizing the cascade utilization of heat energy; and the heat storage medium flows through the heater (19) and the second heat supply heat exchanger (24) and is mixed, and enters the preheater (18), and is further stored in the low-temperature storage tank (7) after the temperature is further reduced.

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