Hydrogen production system and method for water electrolysis suitable for offshore floating wind turbines

Abstract

This invention discloses a water electrolysis hydrogen production system and method adapted for offshore floating wind turbines. The system is installed on the foundation of the offshore floating wind turbine and utilizes the electricity generated by the offshore floating wind turbine to indirectly produce hydrogen from seawater. The system comprises an alkaline electrolysis cell unit, a hydrogen separation cooling unit, a hydrogen purification cooling unit, an oxygen separation cooling unit, an alkaline liquid filtration and circulation unit, an alkaline liquid cooling unit, a negative pressure seawater desalination unit, a raw material freshwater storage and supply unit, an expansion tank unit, and a circulating freshwater transport unit. This invention achieves freshwater self-sufficiency by using closed-circulation freshwater as the cooling medium for the cooling unit in alkaline water electrolysis hydrogen production, and using the absorbed heat as the heat source for seawater desalination in the negative pressure seawater desalination unit, thereby forming a closed-circulation system of freshwater and transferring heat. This invention is applicable to decentralized seawater hydrogen production scenarios for offshore floating wind turbines and is advantageous in promoting the development of offshore green hydrogen production technology by forming an integrated wind-electricity-hydrogen-freshwater equipment system.

Description

Technical Field

[0001] The present invention relates to a system and method for indirect hydrogen production using seawater, and particularly to a water electrolysis hydrogen production system and method adapted to an offshore floating wind turbine.

Background Art

[0002] Hydrogen energy is regarded as the most promising clean energy in the 21st century. Currently in China, based on the government's policy guidelines, many regions have already announced hydrogen energy industry plans and are promoting the future construction of hydrogen energy infrastructure. Hydrogen production technology by water electrolysis is considered one of the most expected hydrogen production strategies, and producing green hydrogen by electrolyzing water using electricity from renewable energy has become an important development path in the new energy field.

[0003] Currently, the proton exchange membrane (PEM) water electrolysis technology requires pure water as a raw material, and furthermore, there are problems such as low single-unit hydrogen production and high cost at present. On the other hand, hydrogen production technology by alkaline water electrolysis only needs to use fresh water as a raw material, and as the most mature and widely industrialized hydrogen production technology, it occupies a leading position. However, fresh water resources around the world are extremely limited, and such conventional technologies will exacerbate the problem of fresh water resource shortage.

[0004] Since 2018, offshore wind power in China has developed rapidly, influenced by technological advancements, cost reductions, and policy adjustments. This has accelerated the approval, commencement, and construction of offshore wind power projects in many regions. Furthermore, seawater resources are abundant. In addition, the foundations of offshore floating wind turbines have a large deck area and large variable load capacity, making them suitable for mounting high-power hydrogen production equipment. If hydrogen production equipment using seawater is placed at each of the multiple floating wind turbines within an offshore wind power plant, and the hydrogen is transported via pipeline to an aggregation platform for centralized storage and external transport, a decentralized seawater hydrogen production scenario can be formed. Moreover, hydrogen production using decentralized offshore wind power has the advantages of independent hydrogen production functions for each wind turbine, high scalability, and high reliability.

[0005] In recent years, the technology of directly electrolyzing seawater to produce hydrogen has attracted the research interest of scholars, but at present, it remains in the stage of technological research and development and verification. Therefore, the problem of how to combine seawater desalination technology and alkaline water electrolysis hydrogen production technology to construct an effective indirect hydrogen production technology using seawater, and how to apply it on a large scale to offshore floating wind turbines, is an urgent issue that needs to be resolved. [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention has been made in view of the above technical problems and provides a water electrolysis hydrogen production system and method suitable for offshore floating wind turbines. By using closed-circulation freshwater as the cooling medium for the cooling unit in alkaline water electrolysis hydrogen production, and using the heated freshwater as the heat source for seawater in a negative-pressure seawater desalination unit to form a closed freshwater circulation, the heat required for cooling in alkaline water electrolysis hydrogen production is used to perform negative-pressure seawater desalination, and the raw freshwater is supplied to alkaline water electrolysis hydrogen production. In this way, not only is the waste heat generated in alkaline water electrolysis hydrogen production effectively utilized, but indirect hydrogen production using seawater is also realized, and it can be applied to the distributed seawater hydrogen production scene of offshore floating wind turbines. This provides a feasible technical means for hydrogen production by offshore wind power generation, provides technical support and a basis for research and development for indirect hydrogen production using seawater, and is also advantageous for the on-site use of offshore wind power generation. [Means for solving the problem]

[0007] To achieve the above objectives, the present invention employs the following technical means.

[0008] One aspect of the present invention is a water electrolysis hydrogen production system adapted for a floating offshore wind turbine, comprising an alkaline electrolytic cell unit, an oxygen separation and cooling unit, a hydrogen separation and cooling unit, an alkaline liquid filtration and circulation unit, an alkaline liquid cooling unit, a negative pressure seawater desalination unit, and a circulating freshwater transport unit, wherein the power interface of the alkaline electrolytic cell unit is connected to the floating offshore wind turbine, freshwater in the alkaline electrolytic cell unit is decomposed into hydrogen and oxygen by the action of DC power from the floating offshore wind turbine, hydrogen and alkaline liquid enter the hydrogen separation and cooling unit, oxygen and alkaline liquid enter the oxygen separation and cooling unit, and alkaline liquid filtration and circulation The unit separates the alkaline liquid in the oxygen separation cooling unit and the hydrogen separation cooling unit and circulates it to the alkaline electrolytic cell unit. The alkaline liquid cooling unit is installed between the alkaline liquid filtration and circulation unit and the alkaline electrolytic cell unit to cool the alkaline liquid to the temperature range required by the electrolytic cell. The negative pressure seawater desalination unit performs desalination of seawater under reduced pressure and supplies the raw freshwater for alkaline water electrolysis hydrogen production. The circulating freshwater transport unit constructs a closed-loop freshwater circulation system, which absorbs heat from the medium that needs to be cooled in alkaline water electrolysis hydrogen production, and uses that heat as a heat source for seawater desalination by the negative pressure seawater desalination unit.

[0009] Furthermore, the alkaline solution inlet of the alkaline electrolytic cell unit is connected to the alkaline solution outlet of the alkaline solution cooling unit, the hydrogen outlet of the alkaline electrolytic cell unit is connected to the hydrogen separation cooling unit, the oxygen outlet of the alkaline electrolytic cell unit is connected to the oxygen separation cooling unit, the alkaline solution outlet of the oxygen separation cooling unit and the alkaline solution outlet of the hydrogen separation cooling unit are connected and merge to form a main pipe which is connected to the alkaline solution filtration and circulation unit, and the cooling freshwater outlet of the oxygen separation cooling unit is connected to the cooling freshwater outlet of the hydrogen separation cooling unit and then to the cooling freshwater inlet of the alkaline solution cooling unit.

[0010] Furthermore, the system of the present invention further comprises a hydrogen purification cooling unit, wherein the hydrogen inlet of the hydrogen separation cooling unit is connected to the hydrogen outlet of the alkaline electrolytic cell unit, the hydrogen outlet of the hydrogen separation cooling unit is connected to the hydrogen purification cooling unit, the cooling freshwater inlet of the hydrogen separation cooling unit is connected to the cooling freshwater inlet of the oxygen separation cooling unit and then to the cooling freshwater outlet of the hydrogen purification cooling unit, the cooling freshwater outlet of the hydrogen separation cooling unit is connected to the cooling freshwater outlet of the oxygen separation cooling unit and then to the cooling freshwater inlet of the alkaline liquid cooling unit, and hydrogen separation cooling The raw freshwater inlet of the unit is connected to the freshwater source of the negative-pressure seawater desalination unit, the hydrogen outlet of the hydrogen purification cooling unit is connected to the transport line, the cooled freshwater inlet of the hydrogen purification cooling unit is connected to the cooled freshwater outlet of the negative-pressure seawater desalination unit, and the cooled freshwater outlet of the hydrogen purification cooling unit is connected to the cooled freshwater inlet of the hydrogen separation cooling unit and the cooled freshwater inlet of the oxygen separation cooling unit. The hydrogen purification cooling unit removes water, oxygen, and other impurities by catalytic reaction, cooling, and molecular sieve adsorption, ultimately purifying the hydrogen to a purity of 99.999%.

[0011] Furthermore, the seawater inlet of the negative pressure seawater desalination unit is a seawater inlet passage. The generated freshwater outlet of the negative pressure seawater desalination unit is connected to the raw material freshwater inlet of the raw material freshwater storage and supply unit, the heated freshwater inlet of the negative pressure seawater desalination unit is connected to the outlet of the circulating freshwater transport unit, the heated freshwater outlet of the negative pressure seawater desalination unit is connected to the cooled freshwater inlet of the hydrogen purification and cooling unit, and the raw material freshwater outlet of the raw material freshwater storage and supply unit is connected to the raw material freshwater inlet of the hydrogen separation and cooling unit and the freshwater inlet of the expansion tank unit, respectively, to replenish the hydrogen separation and cooling unit and the expansion tank unit with raw material freshwater.

[0012] Furthermore, the system of the present invention further comprises an expansion tank unit, the freshwater inlet of the expansion tank unit being connected to a raw material freshwater storage and supply unit, and the freshwater outlet of the expansion tank unit being connected to the pipeline at the front end of the inlet of a circulating freshwater transport unit, so that when the closed circulating freshwater is depleted due to long-term operation, an appropriate amount of freshwater is replenished in the closed circulating freshwater pipeline.

[0013] Furthermore, the hydrogen separation and cooling unit includes a hydrogen gravity separation cooler, a hydrogen cooler, and a hydrogen gas-liquid separator, while the oxygen separation and cooling unit includes an oxygen gravity separation cooler, an oxygen cooler, and an oxygen gas-liquid separator.

[0014] Furthermore, the negative pressure seawater desalination unit is equipped with a negative pressure seawater desalination device, a water quality monitor, a salinity meter, a thermometer, a seawater temperature control valve, a brine temperature control valve, a condenser, a vacuum pump, and a seawater suction pump. The negative pressure seawater desalination device performs negative pressure low-temperature seawater desalination. The water quality monitor detects whether the generated freshwater is acceptable or not; if it is deemed acceptable, it is allowed to flow into the raw freshwater tank; if it is deemed unacceptable, it is returned to the negative pressure seawater desalination device for further desalination. The salinity meter detects the salinity of the seawater in the negative pressure seawater desalination device, the thermometer detects the temperature of the seawater in the negative pressure seawater desalination device, the vacuum pump is controlled by a vacuum gauge to maintain the vacuum level in the negative pressure seawater desalination device, the condenser condenses water vapor to protect the vacuum pump, and the seawater suction pump draws up seawater from nearby and supplies it to the negative pressure seawater desalination device.

[0015] Furthermore, the system of the present invention further comprises a seawater supply filtration unit, the export end of which is connected to a negative pressure seawater desalination unit, the seawater supply filtration unit consisting of a seawater suction pump, a multimedia filter, an activated carbon filter, and a microfilter, the seawater suction pump pumps up seawater from nearby and supplies it to the negative pressure seawater desalination unit, the multimedia filter, activated carbon filter, and microfilter remove some impurities from the seawater and reduce scale formation in the negative pressure seawater desalination unit.

[0016] Another aspect of the present invention is a method for producing hydrogen by water electrolysis, applicable to a floating offshore wind turbine. The process involves a step of decomposing the raw material freshwater in an alkaline electrolytic cell unit into hydrogen and oxygen by the action of DC power from a floating wind turbine, The process involves transporting oxygen and alkaline liquid to an oxygen separation and cooling unit via the oxygen outlet of the alkaline electrolytic cell unit for gas-liquid separation and cooling, guiding the oxygen from which the alkaline liquid has been removed to a safe area for discharge, transporting hydrogen and alkaline liquid to a hydrogen separation and cooling unit via the hydrogen outlet of the alkaline electrolytic cell unit for gas-liquid separation and cooling to remove the alkaline liquid, then introducing hydrogen and a small amount of water into a hydrogen purification and cooling unit to further purify the hydrogen to a hydrogen content of 99.999%, and finally supplying the obtained hydrogen to the transport line. The alkaline solution filtration and circulation unit completes the cooling and forced circulation of the alkaline solution by extracting the alkaline solution from the hydrogen separation and cooling unit and the oxygen separation and cooling unit, cooling it in the alkaline solution cooling unit, and finally transporting it to the alkaline electrolytic cell unit. The method includes the step of desalination of seawater by using a negative pressure seawater desalination unit, connecting the outlet of the generated freshwater from the negative pressure seawater desalination unit to the inlet of the raw material freshwater from a raw material freshwater storage and supply unit, and having the closed-loop circulating freshwater sequentially absorb heat from the mediums that need to be cooled in the hydrogen purification cooling unit, hydrogen separation cooling unit, oxygen separation cooling unit, and alkaline liquid cooling unit during the alkaline water electrolysis hydrogen production process, and then entering the negative pressure seawater desalination unit via a circulating freshwater transport unit to heat the seawater, thereby carrying out negative pressure low-temperature seawater desalination.

[0017] Furthermore, if the closed-circulation freshwater system experiences depletion due to long-term operation, an appropriate amount of freshwater is replenished in the closed-circulation freshwater pipeline. If the freshwater in the expansion tank unit becomes insufficient, a valve is opened to replenish the freshwater from the raw material freshwater storage and supply unit. The freshwater produced by the negative-pressure seawater desalination unit is stored in the raw material freshwater storage and supply unit, and the freshwater is used to replenish the hydrogen separation and cooling unit. This freshwater is also supplied as raw material for alkaline water electrolysis hydrogen production, and the expansion tank unit is replenished with freshwater. [Effects of the Invention]

[0018] The present invention has the following advantages.

[0019] 1. The present invention enables the production of hydrogen on-site using wind power generated by a floating offshore wind turbine and nearby seawater.

[0020] 2. The present invention uses closed-circulation freshwater as a cooling medium for the cooling unit in alkaline water electrolysis hydrogen production, and uses the absorbed heat as a heat source for seawater desalination in a negative-pressure seawater desalination unit to form a closed-circulation freshwater system and transfer heat, thereby achieving efficient energy utilization and reducing energy consumption in hydrogen production by water electrolysis.

[0021] 3. The present invention utilizes the heat dissipation from the cooling unit in alkaline water electrolysis hydrogen production to achieve low-temperature seawater desalination in a negative-pressure seawater desalination unit, and the approved freshwater is used as the raw material for electrolysis to replenish the alkaline electrolysis cell unit, thereby achieving freshwater self-sufficiency.

[0022] 4. In the closed freshwater circulation of the present invention, the cooled freshwater enters the hydrogen purification cooling unit from the negative pressure seawater desalination unit, then simultaneously enters the hydrogen purification cooling unit and the oxygen purification cooling unit, then merges in the main pipe and enters the alkaline liquid cooling unit, and finally enters the negative pressure seawater desalination unit via the circulating freshwater transport unit, thereby forming a closed freshwater circulation, and the freshwater has low requirements for the material of the pipes and accessories, making it economical.

[0023] 5. The present invention enables indirect hydrogen production using seawater by coupling a functional unit for alkaline water electrolysis hydrogen production with a functional unit for negative pressure seawater desalination. It is applicable to offshore floating wind turbines and forms an integrated wind-electricity-hydrogen-freshwater equipment system, which is advantageous in promoting the development of offshore green hydrogen production technology. [Brief explanation of the drawing]

[0024] To more clearly explain the technical means in the embodiments of the present invention or the prior art, the drawings related to the embodiments or the prior art will be briefly introduced below. The following drawings are some embodiments of the present invention. It is needless to say that those skilled in the art can obtain other drawings based on these drawings without creative labor.

[0025] [Figure 1] It is a flowchart of the main functions of Embodiment 1 of the present invention. [Figure 2] It is a flowchart of the process system of Embodiment 1 of the present invention. [Figure 3] It is a flowchart of the main functions of Embodiment 2 of the present invention.

Modes for Carrying Out the Invention

[0026] To make the purpose, technical means and advantages of the embodiments according to the present invention clearer, the technical means in the embodiments of the present invention will be clearly and completely described below while referring to the drawings in the embodiments of the present invention. It is needless to say that the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art without creative labor based on the embodiments in the present invention shall all be included in the scope protected by the present invention.

[0027] Embodiment 1 The method and system for producing hydrogen by electrolyzing water adapted to the offshore floating wind turbine according to the embodiment of the present invention comprise the following functional units.

[0028] Alkaline electrolytic cell unit: The power interface of the alkaline electrolytic cell unit is connected to the offshore floating wind turbine, the alkaline liquid inlet of the alkaline electrolytic cell unit is connected to the alkaline liquid outlet of the alkaline liquid cooling unit, the hydrogen outlet of the alkaline electrolytic cell unit is connected to the hydrogen separation cooling unit, and the oxygen outlet of the alkaline electrolytic cell unit is connected to the oxygen separation cooling unit. As a result, the freshwater in the alkaline electrolytic cell unit is decomposed into hydrogen and oxygen by the action of the DC power from the offshore floating wind turbine, the hydrogen and alkaline liquid enter the hydrogen separation cooling unit, and the oxygen and alkaline liquid enter the oxygen separation cooling unit.

[0029] Oxygen Separation Cooling Unit: The oxygen inlet of the oxygen separation cooling unit is connected to the oxygen outlet of the alkaline electrolytic cell unit, and the oxygen outlet of the oxygen separation cooling unit is guided to a safe area to discharge oxygen into the atmosphere. The alkaline liquid outlet of the oxygen separation cooling unit and the alkaline liquid outlet of the hydrogen separation cooling unit are connected and merge to form a main pipe, which is connected to the alkaline liquid filtration and circulation unit. The cooling freshwater inlet of the oxygen separation cooling unit is connected to the cooling freshwater inlet of the hydrogen separation cooling unit, and then to the cooling freshwater outlet of the hydrogen purification cooling unit. The cooling freshwater outlet of the oxygen separation cooling unit is connected to the cooling freshwater outlet of the hydrogen separation cooling unit, and then to the cooling freshwater inlet of the alkaline liquid cooling unit. This separates the oxygen and alkaline liquid that enters the oxygen separation cooling unit from the alkaline electrolytic cell unit into gas and liquid form and cools them.

[0030] Hydrogen Separation Cooling Unit: The hydrogen inlet of the hydrogen separation cooling unit is connected to the hydrogen outlet of the alkaline electrolytic cell unit, the hydrogen outlet of the hydrogen separation cooling unit is connected to the hydrogen purification cooling unit, the alkaline liquid outlet of the hydrogen separation cooling unit is connected to the alkaline liquid outlet of the oxygen separation cooling unit, and these are joined to form a main pipe which is connected to the alkaline liquid filtration and circulation unit, the cooling freshwater inlet of the hydrogen separation cooling unit is connected to the cooling freshwater inlet of the oxygen separation cooling unit and then to the cooling freshwater outlet of the hydrogen purification cooling unit, the cooling freshwater outlet of the hydrogen separation cooling unit is connected to the cooling freshwater outlet of the oxygen separation cooling unit and then to the cooling freshwater inlet of the alkaline liquid cooling unit, and the raw material freshwater inlet of the hydrogen separation cooling unit is connected to the raw material freshwater storage and supply unit. As a result, the hydrogen and alkaline liquid that enter the hydrogen separation cooling unit from the alkaline electrolytic cell unit are separated into gas and liquid phases, cooled, and supplied as raw material freshwater to the passage of the alkaline electrolytic cell unit, while also assisting functions such as hydrogen washing and cooling.

[0031] Hydrogen Purification Cooling Unit: The hydrogen inlet of the hydrogen purification cooling unit is connected to the hydrogen outlet of the hydrogen separation cooling unit, the hydrogen outlet of the hydrogen purification cooling unit is connected to the transport line, the cooling freshwater inlet of the hydrogen purification cooling unit is connected to the cooling freshwater outlet of the negative pressure seawater desalination unit, and the cooling freshwater outlet of the hydrogen purification cooling unit is connected to the cooling freshwater inlet of the hydrogen separation cooling unit and the cooling freshwater inlet of the oxygen separation cooling unit. Through this process, water, oxygen, and other impurities are removed by catalytic reaction, cooling, and molecular sieve adsorption, ultimately purifying the hydrogen to a purity of 99.999%.

[0032] Alkaline Solution Filtration and Circulation Unit: The alkaline solution inlet of the alkaline solution filtration and circulation unit is connected to the main pipe of the alkaline solution formed by the convergence of the alkaline solution outlets of the hydrogen separation and cooling unit and the oxygen separation and cooling unit. The alkaline solution outlet of the alkaline solution filtration and circulation unit is connected to the alkaline solution cooling unit. This completes the forced circulation of the alkaline solution in the alkaline electrolytic cell unit, hydrogen separation and cooling unit, and oxygen separation and cooling unit, allowing for the filtration of impurities from the alkaline solution.

[0033] Alkaline liquid cooling unit: The alkaline liquid inlet of the alkaline liquid cooling unit is connected to the outlet of the alkaline liquid filtration and circulation unit, the alkaline liquid outlet of the alkaline liquid cooling unit is connected to the alkaline liquid inlet of the alkaline electrolytic cell unit, the cooling freshwater inlet of the alkaline liquid cooling unit is connected to the cooling freshwater general pipe where the cooling freshwater outlets of the hydrogen separation cooling unit and the oxygen separation cooling unit merge, and the cooling freshwater outlet of the alkaline liquid cooling unit is connected to the inlet of the circulating freshwater transport unit. This allows the alkaline liquid to be cooled to the temperature range required by the electrolytic cell.

[0034] Negative Pressure Seawater Desalination Unit: The seawater inlet of the negative pressure seawater desalination unit is a seawater entry passage, the generated freshwater outlet of the negative pressure seawater desalination unit is connected to the raw material freshwater inlet of the raw material freshwater storage and supply unit, the heated freshwater inlet of the negative pressure seawater desalination unit is connected to the outlet of the circulating freshwater transport unit, and the heated freshwater outlet of the negative pressure seawater desalination unit is connected to the cooled freshwater inlet of the hydrogen purification and cooling unit. This allows for the use of closed-loop circulating freshwater to absorb heat from the medium that requires cooling in alkaline water electrolysis hydrogen production, to perform desalination of seawater under reduced pressure, and to provide raw material freshwater for hydrogen production by alkaline water electrolysis.

[0035] Circulating freshwater transport unit: The freshwater inlet of the circulating freshwater transport unit is connected to the cooled freshwater outlet of the alkaline liquid cooling unit, and the freshwater outlet of the circulating freshwater transport unit is connected to the heated freshwater inlet of the negative pressure seawater desalination unit. This provides power for the circulation of closed-loop freshwater.

[0036] Expansion Tank Unit: The freshwater inlet of the expansion tank unit is connected to the raw freshwater storage and supply unit, and the freshwater outlet of the expansion tank unit is connected to the pipeline at the inlet end of the circulating freshwater transport unit. As a result, when the closed circulating freshwater system is depleted due to long-term operation, an appropriate amount of freshwater is replenished in the closed circulating freshwater pipeline. When the freshwater in the expansion tank unit becomes insufficient, the valve is opened to replenish the freshwater from the raw freshwater storage and supply unit. When the freshwater in the expansion tank unit becomes insufficient, the valve is closed to stop the replenishment of freshwater.

[0037] Freshwater storage and supply unit: The raw freshwater inlet of the freshwater storage and supply unit is connected to the generated freshwater outlet of the negative pressure seawater desalination unit, and the raw freshwater outlet of the freshwater storage and supply unit is connected to the raw freshwater inlet of the hydrogen separation and cooling unit and the freshwater inlet of the expansion tank unit, respectively. This allows the raw freshwater generated by the negative pressure seawater desalination unit to be stored and used to replenish the raw freshwater in the hydrogen separation and cooling unit and the expansion tank unit.

[0038] Figure 1 is a flowchart showing the main functions of a water electrolysis hydrogen production method and system adapted for offshore floating wind turbines, with the area within baseline 1 showing the water electrolysis hydrogen production method and system adapted for offshore floating wind turbines. The water electrolysis hydrogen production method and system adapted for offshore floating wind turbines of the present invention comprises, as functional units, an alkaline electrolytic cell unit 2, a hydrogen separation and cooling unit 3, a hydrogen purification and cooling unit 4, an oxygen separation and cooling unit 5, an alkaline liquid filtration and circulation unit 6, an alkaline liquid cooling unit 7, a negative pressure seawater desalination unit 8, a raw material freshwater storage and supply unit 9, an expansion tank unit 10, and a circulating freshwater transport unit 11. The water electrolysis hydrogen production method and system adapted for offshore floating wind turbines includes the following steps as a functional flow: The process involves the following steps: first, decomposing the raw freshwater in the nitrate unit 2 into hydrogen and oxygen using DC power from a floating offshore wind turbine; second, transporting the oxygen and alkaline liquid to the oxygen separation and cooling unit 5 via the oxygen outlet of the alkaline electrolytic cell unit 2 for gas-liquid separation and cooling; third, guiding the oxygen, from which the alkaline liquid has been removed, to a safe area for discharge; and fourth, transporting the hydrogen and alkaline liquid to the hydrogen separation and cooling unit 3 via the hydrogen outlet of the alkaline electrolytic cell unit 2 for gas-liquid separation and cooling to remove the alkaline liquid. Finally, the hydrogen and a small amount of water are introduced into the hydrogen purification and cooling unit 4, resulting in a hydrogen content of 99%.The process involves further purifying the solution to 999%, then supplying the resulting hydrogen to a transport line, and the alkaline liquid filtration and circulation unit 6 extracting the alkaline liquid from the hydrogen separation and cooling unit 3 and the oxygen separation and cooling unit 5, cooling it in the alkaline liquid cooling unit 7, and finally transporting it to the alkaline electrolytic cell unit 2 to complete the cooling and forced circulation of the alkaline liquid. The seawater inlet of the negative pressure seawater desalination unit 8 is a seawater entry passage, and the freshwater outlet of the negative pressure seawater desalination unit 8 is connected to the freshwater inlet of the freshwater storage and supply unit 9, and the closed-circulation freshwater is used in the alkaline water electrolysis hydrogen production process by the hydrogen purification and cooling unit 4, hydrogen separation and cooling unit 3, oxygen separation and cooling unit 5, and alkaline liquid cooling unit 8. The process involves sequentially absorbing heat from the medium requiring cooling in the nit 7, and then heating the seawater by having it enter the negative-pressure seawater desalination unit 8 via the circulating freshwater transport unit 11, thereby performing negative-pressure low-temperature seawater desalination. Furthermore, when wear and tear occurs due to long-term operation of the closed-circulation freshwater system, the expansion tank unit 10 replenishes an appropriate amount of freshwater into the closed-circulation freshwater pipeline. When the freshwater in the expansion tank unit 10 becomes insufficient, the valve is opened to replenish freshwater from the raw material freshwater storage and supply unit 9. The freshwater produced by the negative-pressure seawater desalination unit 8 is stored in the raw material freshwater storage and supply unit 9, and freshwater is then supplied to the hydrogen separation and cooling unit 3, providing raw material freshwater for alkaline water electrolysis hydrogen production, while also replenishing freshwater in the expansion tank unit 10.

[0039] Figure 2 is a flowchart of a process system according to an embodiment of the present invention. As can be seen from Figure 2, the alkaline electrolytic cell unit 2 is mainly composed of an alkaline electrolytic cell 21, which produces hydrogen and oxygen by electrolyzing fresh water with electricity from offshore wind power generation. The hydrogen separation and cooling unit 3 is composed of a hydrogen gravity separation cooler 31, a hydrogen cooler 32, and a hydrogen gas-liquid separator 33, which separates hydrogen and alkaline liquid into gas-liquid and cools them, and also provides a path for hydrogen to enter the hydrogen purification and cooling unit 4. The hydrogen purification and cooling unit 4 is composed of a gas-liquid separator, a deoxygenation tower, a drying tower, and a cooler, and hydrogen The hydrogen is purified to a content of 99.999% and supplied to the transport line. The oxygen separation and cooling unit 5 consists of an oxygen gravity separation cooler 51, an oxygen cooler 52, and an oxygen gas-liquid separator 53, which separates hydrogen and alkaline liquid into gas-liquid and gas-liquid, cools them, and provides a path for exhausting hydrogen. The alkaline liquid filtration and circulation unit 6 consists of an alkaline liquid filter 61 and an alkaline liquid circulation pump 62, which provides power for forced circulation of the alkaline liquid and filters out impurities. The alkaline liquid cooling unit 7 mainly consists of an alkaline liquid cooler 71, which cools the high-temperature alkaline liquid and removes alkaline electricity. To meet the required temperature of the desalination tank 21, the negative pressure seawater desalination unit 8 consists of a negative pressure desalination tank 81, a water quality monitor 82, a salinity meter 83, a thermometer 84, a seawater temperature control valve 85, a brine temperature control valve 86, a condenser 87, a vacuum pump 88, and a seawater suction pump 89. The negative pressure desalination tank 81 uses the heat of a closed-loop circulating freshwater system to desalinate seawater under negative pressure and low temperature. The water quality monitor 82 detects whether the generated freshwater is acceptable. If it is detected as acceptable, it flows into the raw freshwater tank 91. If it is detected as unacceptable, it is returned to the negative pressure seawater desalination device 81 for continued desalination. The following functions are performed: the salinity meter 83 detects the salinity of the seawater in the negative pressure seawater desalination plant 81 and controls the opening of the saltwater temperature control valve 86; the thermometer 84 detects the temperature of the seawater in the negative pressure seawater desalination plant 81 and controls the opening of the seawater temperature control valve 85; the vacuum pump 88 is controlled by the vacuum gauge 80 to maintain the vacuum level of the negative pressure seawater desalination plant 8; the condenser 87 condenses the small amount of water vapor present to protect the vacuum pump 88 and assist in desalination; the seawater suction pump 89 pumps up seawater from nearby and supplies it to the negative pressure seawater desalination plant 81; and the raw freshwater storage and supply unit 9 is...The system consists of a raw freshwater tank 91 and a raw freshwater supply pump 92, which store the freshwater produced by the negative pressure seawater desalination unit 81 and supply freshwater to the hydrogen gravity separation cooler 31 and the expansion tank 101. The expansion tank unit 10 consists of an expansion tank 101, a remote control valve 102, and a liquid level monitoring transmitter 103, which replenishes freshwater to the closed freshwater circulation system. The liquid level monitoring transmitter 103 controls the opening and closing of the remote control valve 102, which replenishes freshwater to the expansion tank 101 via the raw freshwater supply pump 92. The circulating freshwater transport unit 11 mainly consists of a freshwater circulation pump 111, which provides power to the closed-circulation freshwater system.

[0040] According to the present invention, by utilizing the waste heat generated in alkaline water electrolysis hydrogen production, it is possible not only to desalinate seawater under negative pressure and low temperature conditions, but also to achieve self-sufficiency in fresh water. Therefore, it realizes indirect hydrogen production using seawater while simultaneously achieving rational and efficient use of energy, and reduces energy consumption in water electrolysis hydrogen production. In particular, since the equipment for the indirect seawater hydrogen production system is installed on the foundation of a floating offshore wind turbine, it is possible to indirectly produce hydrogen by electrolyzing seawater using electricity generated by the floating offshore wind turbine and local seawater on-site. This makes it applicable to decentralized seawater hydrogen production scenes using floating offshore wind turbines, forming a one-stop equipment system of wind-electricity-hydrogen-freshwater, which is advantageous in promoting the development of marine green hydrogen production technology.

[0041] Example 2 Unlike Example 1, coastal wind power plants located more than 20 km offshore and with water depths of 25-50 m often employ fixed wind power generation equipment such as fixed single-column wind turbines and jacketed booster platforms. To reduce the overall cost of hydrogen production facilities and improve the efficiency of hydrogen storage and transportation, fixed platforms with sufficient deck area can be installed at coastal wind power plants, allowing for concentrated hydrogen production using offshore wind power. This coastal centralized hydrogen production mode is also suitable when modifying existing booster platforms to add hydrogen production equipment.

[0042] Therefore, in response to this situation, as shown in Figure 3, the baseline represents a method and system applicable to coastal-centered indirect hydrogen production using seawater. The method and system provided by the present invention for coastal-centered indirect hydrogen production using seawater mainly includes, as functional units, an alkaline electrolytic cell unit, an oxygen separation and washing unit, an oxygen cooling and separation unit, a hydrogen separation and washing unit, a hydrogen cooling and separation unit, a hydrogen purification and cooling unit, an alkaline liquid filter and circulation unit, a negative pressure seawater desalination unit, a seawater supply and filtration unit, and a freshwater replenishment unit.

[0043] Alkaline electrolytic cell unit: The power interface of the alkaline electrolytic cell unit is connected to the electrical cables of the offshore wind power plant, the alkaline liquid inlet of the alkaline electrolytic cell unit is connected to the alkaline liquid outlet of the negative pressure seawater desalination unit, the hydrogen outlet of the alkaline electrolytic cell unit is connected to the hydrogen inlet of the hydrogen separation and cleaning unit, and the oxygen outlet of the alkaline electrolytic cell unit is connected to the oxygen inlet of the oxygen separation and cleaning unit. As a result, the freshwater in the alkaline electrolytic cell unit is decomposed into hydrogen and oxygen by the action of the DC power generated by the offshore wind power plant, the hydrogen and alkaline liquid enter the hydrogen separation and cleaning unit, and the oxygen and alkaline liquid enter the oxygen separation and cleaning unit, which receives the cooled alkaline liquid recirculated from the negative pressure seawater desalination unit.

[0044] Oxygen Separation and Washing Unit: The oxygen inlet of the oxygen separation and washing unit is connected to the oxygen outlet of the alkaline electrolytic cell unit, the oxygen outlet of the oxygen separation and washing unit is connected to the oxygen cooling and separation unit, the raw freshwater inlet of the oxygen separation and washing unit is connected to the raw freshwater inlet of the hydrogen separation and washing unit and merges to form a main pipe which is connected to the freshwater supply unit, the alkaline liquid outlet of the oxygen separation and washing unit is connected to the alkaline liquid outlet of the hydrogen separation and washing unit and merges to form a main pipe which is connected to the alkaline liquid filtration and circulation unit. As a result, the oxygen and alkaline liquid that enter the oxygen separation and washing unit from the alkaline electrolytic cell unit are separated into gas and liquid, washed, the necessary freshwater is supplied from the alkaline electrolytic cell unit, and the alkaline liquid is circulated to the negative pressure seawater desalination unit using seawater as a heating source.

[0045] Oxygen Cooling Separation Unit: The oxygen inlet of the oxygen cooling separation unit is connected to the oxygen outlet of the oxygen separation and washing unit, and the oxygen outlet of the oxygen cooling separation unit is guided to a safe area for exhaust. The cooling seawater inlet of the oxygen cooling separation unit and the cooling seawater inlet of the hydrogen cooling separation unit are connected and merge to form a main pipe, which is connected to the cooling seawater outlet of the hydrogen purification and cooling unit. The cooling seawater outlet of the oxygen cooling separation unit and the cooling seawater outlet of the hydrogen cooling separation unit are connected and merge to form a main pipe, which is connected to the heat source seawater inlet of the negative pressure seawater desalination unit. This separates the oxygen and a small amount of water that enters the oxygen cooling separation unit from the oxygen separation and washing unit into gas and liquid phases, cools them, and heats the cooling seawater.

[0046] Hydrogen Separation and Washing Unit: The hydrogen inlet of the hydrogen separation and washing unit is connected to the hydrogen outlet of the alkaline electrolytic cell unit, the hydrogen outlet of the hydrogen separation and washing unit is connected to the hydrogen cooling and separation unit, the raw freshwater inlet of the hydrogen separation and washing unit is connected to the raw freshwater inlet of the oxygen separation and washing unit and merges to form a main pipe which is connected to the freshwater supply unit, the alkaline liquid outlet of the hydrogen separation and washing unit is connected to the alkaline liquid outlet of the oxygen separation and washing unit and merges to form a main pipe which is connected to the alkaline liquid filtration and circulation unit. As a result, the hydrogen and alkaline liquid that enter the hydrogen separation and washing unit from the alkaline electrolytic cell unit are separated into gas and liquid phases and washed, the necessary freshwater is supplied from the alkaline electrolytic cell unit, and the alkaline liquid is circulated to the negative pressure seawater desalination unit using seawater as a heat source.

[0047] Hydrogen Cooling Separation Unit: The hydrogen inlet of the hydrogen cooling separation unit is connected to the hydrogen outlet of the hydrogen separation and washing unit, the hydrogen outlet of the hydrogen cooling separation unit is connected to the hydrogen purification and cooling unit, the cooling seawater inlet of the hydrogen cooling separation unit and the cooling seawater inlet of the oxygen cooling separation unit are connected and merge to form a main pipe which is connected to the cooling seawater outlet of the hydrogen purification and cooling unit, the cooling seawater outlet of the hydrogen cooling separation unit and the cooling seawater outlet of the oxygen cooling separation unit are connected and merge to form a main pipe which is connected to the heat source seawater inlet of the negative pressure seawater desalination unit. This separates the hydrogen and a small amount of water entering the hydrogen cooling separation unit from the hydrogen separation and washing unit into gas and liquid phases, cools them, and heats the cooling seawater.

[0048] Hydrogen Purification Cooling Unit: The hydrogen inlet of the hydrogen purification cooling unit is connected to the hydrogen outlet of the hydrogen cooling separation unit, the hydrogen outlet of the hydrogen purification cooling unit is connected to the transport line, and the cooling seawater inlet of the hydrogen purification cooling unit is connected to the cooling seawater outlet of the negative pressure seawater desalination unit. This removes water, oxygen, and other impurities by methods such as catalytic reactions, molecular sieve adsorption, and cooling, ultimately purifying the hydrogen to 99.999% purity and heating the cooling seawater.

[0049] Alkaline Solution Filtration and Circulation Unit: The alkaline solution inlet of the alkaline solution filtration and circulation unit is connected to the total alkaline solution pipe formed by the connection and merger of the alkaline solution outlets of the hydrogen separation and washing unit and the oxygen separation and washing unit. The alkaline solution outlet of the alkaline solution filtration and circulation unit is connected to the alkaline solution inlet of the negative pressure seawater desalination unit. This completes the forced circulation of the alkaline solution in the alkaline electrolytic cell unit, hydrogen separation and washing unit, oxygen separation and washing unit, and negative pressure seawater desalination unit, filtering out impurities from the alkaline solution.

[0050] Seawater supply filtration unit: The seawater inlet of the seawater supply filtration unit is guided below the seawater surface, and the seawater outlet of the seawater supply filtration unit is connected to the cooling seawater inlet of the negative pressure seawater desalination unit. This filters out impurities from the seawater in the initial stages, reducing scale formation in the seawater supplied to the negative pressure seawater desalination unit.

[0051] Negative pressure seawater desalination unit: The cooling seawater inlet of the negative pressure seawater desalination unit is connected to the seawater outlet of the seawater supply filtration unit, the cooling seawater outlet of the negative pressure seawater desalination unit is connected to the cooling seawater inlet of the hydrogen purification cooling unit, the heat source seawater inlet of the negative pressure seawater desalination unit is connected to a general pipe formed by the connection and merger of the cooling seawater outlet of the oxygen cooling separation unit and the cooling seawater outlet of the hydrogen cooling separation unit, the alkaline solution inlet of the negative pressure seawater desalination unit is connected to the outlet of the alkaline solution filtration circulation unit, the alkaline solution outlet of the negative pressure seawater desalination unit is connected to the alkaline solution inlet of the alkaline electrolytic cell unit, and the freshwater outlet of the negative pressure seawater desalination unit is connected to the freshwater supply unit. As a result, the waste heat generated in alkaline water electrolysis is absorbed using the cooling seawater to create heat source seawater, the heat released by the cooling of the alkaline solution is used to further heat the heat source seawater, negative pressure low-temperature seawater desalination is performed, and raw material freshwater for hydrogen production by alkaline water electrolysis is provided. By utilizing the waste heat generated from alkaline water electrolysis hydrogen production, it is possible not only to achieve negative-pressure, low-temperature seawater desalination, but also to achieve freshwater self-sufficiency.

[0052] Freshwater supply unit: The freshwater inlet of the freshwater supply unit is connected to the freshwater outlet of the negative pressure seawater desalination unit, and the freshwater outlet of the freshwater supply unit is connected to the oxygen separation and washing unit and the hydrogen separation and washing unit, respectively. This allows the unit to store the freshwater produced by the negative pressure seawater desalination unit, transport the freshwater to the oxygen separation and washing unit and the hydrogen separation and washing unit, and further supply raw freshwater to the alkaline electrolytic cell unit.

[0053] The specific functional flow of the method and system applied to coastal concentrated indirect hydrogen production using seawater is as follows: The steps include: decomposing freshwater in an alkaline electrolytic cell unit into hydrogen and oxygen by the action of DC power from offshore wind power generation; transporting oxygen and alkaline liquid through the oxygen outlet of the alkaline electrolytic cell unit to an oxygen separation and washing unit for initial gas-liquid separation and washing; then entering an oxygen cooling and separation unit for gas-liquid separation and cooling, and guiding the oxygen, from which the alkaline liquid has been removed, to a safe area for discharge; transporting hydrogen and alkaline liquid through the hydrogen outlet of the alkaline electrolytic cell unit to a hydrogen separation and washing unit for initial gas-liquid separation and washing; then entering a hydrogen cooling and separation unit to remove the alkaline liquid; after which hydrogen and a small amount of water enter a hydrogen purification and cooling unit for further purification to a hydrogen content of 99.999%; and finally supplying the hydrogen to the transport line; and the alkaline liquid filtration and circulation unit is connected to the oxygen separation and washing unit. The process includes the steps of: extracting the alkaline solution from the desalination and hydrogen separation washing unit, cooling it in the negative pressure seawater desalination unit, and finally transporting it to the alkaline electrolytic cell unit to complete the cooling and forced circulation of the alkaline solution; the steps of: the cooling seawater sequentially absorbing the necessary medium heat for cooling the condenser at the top of the negative pressure seawater desalination unit, the hydrogen purification cooling unit for alkaline water electrolysis hydrogen production, the oxygen cooling separation unit, and the hydrogen cooling separation unit, and entering the heat source seawater inlet at the bottom of the negative pressure seawater desalination unit, where the heat source seawater is further heated by the alkaline solution, and then carrying out desalination under negative pressure and low temperature conditions; and storing the fresh water produced by the negative pressure seawater desalination unit in a fresh water supply unit to replenish the oxygen separation washing unit and the hydrogen separation washing unit with fresh water, and supplying raw material fresh water to the electrolytic cell for alkaline water electrolysis.

[0054] Figure 3 is a flowchart of the process system of an embodiment of the present invention. As can be seen from Figure 3, the alkaline electrolytic cell unit mainly consists of an alkaline electrolytic cell, which electrolyzes the fresh water obtained after desalination of seawater using electricity from offshore wind power generation to produce hydrogen and oxygen. The oxygen separation and washing unit consists of an oxygen gravity separator and an oxygen washing machine, which separates and washes the oxygen and alkaline liquid in a gas-liquid manner. The oxygen purification and cooling unit consists of an oxygen cooler and a gas-liquid separator, which removes the alkaline liquid from the oxygen by gas-liquid separation and cooling, and finally leads it to a safe area for discharge. The hydrogen separation and washing unit consists of a hydrogen gravity separator and a hydrogen washing machine, which initially separates and washes the hydrogen in a gas-liquid manner. The hydrogen cooling and separation unit consists of a hydrogen cooler and a gas-liquid separator, which removes the alkaline liquid from the hydrogen, after which the hydrogen and a small amount of water enter the hydrogen purification and cooling unit, where the hydrogen content is 99%.The solution is further purified to 999% and finally supplied to the transport line as hydrogen. The alkaline solution filtration and circulation unit consists of an alkaline solution filter and an alkaline solution circulation pump, which powers the forced circulation of the alkaline solution and filters out impurities. The negative pressure seawater desalination unit consists of a negative pressure seawater desalination device, a vacuum gauge, a vacuum pump, a water quality monitor, a salinity meter, a saltwater temperature control valve, a thermometer, and a seawater temperature control valve. The negative pressure seawater desalination device uses the waste heat generated by the cooling unit during alkaline water electrolysis hydrogen production and the heat released during the cooling of the alkaline solution to perform low-temperature seawater desalination. The vacuum gauge detects the vacuum level of the negative pressure seawater desalination device and controls the vacuum pump to maintain the vacuum level. The water quality monitor detects whether the generated freshwater is acceptable. If it is deemed acceptable, it is allowed to flow into the freshwater tank; if it is deemed unacceptable, it is detected as unacceptable. Once discharged, the seawater is returned to the negative-pressure seawater desalination plant for continued desalination. A salinity meter detects the salinity of the seawater in the negative-pressure seawater desalination plant and controls the opening of the saltwater temperature control valve. A thermometer detects the temperature of the cooled alkaline solution and controls the opening of the seawater temperature control valve. The seawater supply filtration unit consists of a seawater pump, a multi-media filter, an activated carbon filter, and a micro-filter. The seawater pump draws seawater from nearby and supplies it to the negative-pressure seawater desalination plant. The multi-media filter, activated carbon filter, and micro-filter remove some impurities from the seawater, reducing scale formation in the negative-pressure seawater desalination plant. The freshwater replenishment unit consists of a freshwater tank and a freshwater replenishment pump. It stores the freshwater produced by the negative-pressure seawater desalination plant and supplies it to the oxygen and hydrogen washers, replenishing the raw freshwater in the alkaline electrolytic cell.

[0055] This invention enables negative-pressure, low-temperature seawater desalination by using cooling seawater to absorb waste heat generated in the alkaline electrolysis process, thereby creating heat source seawater, and simultaneously further heating the heat source seawater with the heat released during the cooling of the alkaline solution. This optimizes energy efficiency and reduces the cost of the alkaline solution cooler and associated cooling water. Furthermore, by supplying the alkaline electrolysis cell unit with the approved freshwater as the raw material for electrolysis, freshwater self-sufficiency is achieved, reducing the energy consumption of hydrogen production by water electrolysis. Moreover, this system is modular and can be installed on various coastal platforms. This enables hydrogen production using electricity from nearby offshore wind power plants and nearby seawater, realizing indirect hydrogen production through coastal-centralized alkaline seawater electrolysis.

[0056] This invention utilizes waste heat generated in the cooling unit of an alkaline water electrolysis hydrogen production system to achieve low-temperature seawater desalination in a negative-pressure seawater desalination unit, thereby reducing the cost of alkaline liquid coolers and associated cooling water. Furthermore, by supplying the approved freshwater as a raw material for water electrolysis to the alkaline electrolysis cell unit, it achieves freshwater self-sufficiency.

[0057] The system of the present invention is modular and can be installed on various coastal platforms.

[0058] This invention enables hydrogen production using electricity from a nearby offshore wind power plant and nearby seawater.

[0059] Finally, the following should be explained: The above embodiments are merely for illustrating, and not limiting, the technical means of the present invention. Although the present invention has been described in detail with reference to the embodiments described above, it is possible to modify the technical means described in the embodiments above, or to make equivalent substitutions to some or all of their technical features, and it will be understood by those skilled in the art that such modifications or substitutions do not cause the essence of the corresponding technical means to deviate from the scope of the technical means of the embodiments of the present invention.

[0060] (Note) (Note 1) A water electrolysis hydrogen production system suitable for a floating offshore wind turbine, comprising an alkaline electrolytic cell unit, an oxygen separation and cooling unit, a hydrogen separation and cooling unit, an alkaline liquid filtration and circulation unit, an alkaline liquid cooling unit, a negative pressure seawater desalination unit, and a circulating freshwater transport unit, The power interface of the alkaline electrolytic cell unit is connected to a floating offshore wind turbine, and the freshwater in the alkaline electrolytic cell unit is decomposed into hydrogen and oxygen by the action of DC power from the floating offshore wind turbine. The hydrogen and alkaline liquid enter the hydrogen separation cooling unit, and the oxygen and alkaline liquid enter the oxygen separation cooling unit. The alkaline liquid filtration and circulation unit separates the alkaline liquid from the oxygen separation and cooling unit and the hydrogen separation and cooling unit and circulates it to the alkaline electrolytic cell unit. The alkaline liquid cooling unit is installed between the alkaline liquid filtration and circulation unit and the alkaline electrolytic cell unit, and cools the alkaline liquid to the temperature range required by the electrolytic cell. The aforementioned negative pressure seawater desalination unit performs desalination of seawater under reduced pressure and supplies freshwater raw material for alkaline water electrolysis hydrogen production. The aforementioned circulating freshwater transport unit is a water electrolysis hydrogen production system suitable for offshore floating wind turbines, characterized in that it constructs a closed-loop freshwater circulation system, absorbs heat from a medium that requires cooling in alkaline water electrolysis hydrogen production using closed-loop freshwater, and utilizes that heat as a heat source for seawater desalination in a negative-pressure seawater desalination unit.

[0061] (Note 2) A water electrolysis hydrogen production system suitable for a floating offshore wind turbine as described in Appendix 1, characterized in that the alkaline liquid inlet of the alkaline electrolysis cell unit is connected to the alkaline liquid outlet of the alkaline liquid cooling unit, the hydrogen outlet of the alkaline electrolysis cell unit is connected to the hydrogen separation cooling unit, the oxygen outlet of the alkaline electrolysis cell unit is connected to the oxygen separation cooling unit, the alkaline liquid outlet of the oxygen separation cooling unit and the alkaline liquid outlet of the hydrogen separation cooling unit are connected and merge to form a main pipe which is connected to the alkaline liquid filtration and circulation unit, and the cooling freshwater outlet of the oxygen separation cooling unit is connected to the cooling freshwater outlet of the hydrogen separation cooling unit and then to the cooling freshwater inlet of the alkaline liquid cooling unit.

[0062] (Note 3) It is further equipped with a hydrogen purification cooling unit, The hydrogen inlet of the hydrogen separation cooling unit is connected to the hydrogen outlet of the alkaline electrolytic cell unit, the hydrogen outlet of the hydrogen separation cooling unit is connected to the hydrogen purification cooling unit, the cooling freshwater inlet of the hydrogen separation cooling unit is connected to the cooling freshwater inlet of the oxygen separation cooling unit, and then to the cooling freshwater outlet of the hydrogen purification cooling unit, the cooling freshwater outlet of the hydrogen separation cooling unit is connected to the cooling freshwater outlet of the oxygen separation cooling unit, and then to the cooling freshwater inlet of the alkaline liquid cooling unit, and the raw material freshwater inlet of the hydrogen separation cooling unit is connected to the freshwater source of the negative pressure seawater desalination unit, and water A water electrolysis hydrogen production system suitable for a floating offshore wind turbine as described in Appendix 1, characterized in that the hydrogen outlet of the hydrogen purification cooling unit is connected to a transport line, the cooling freshwater inlet of the hydrogen purification cooling unit is connected to the cooling freshwater outlet of a negative-pressure seawater desalination unit, the cooling freshwater outlet of the hydrogen purification cooling unit is connected to the cooling freshwater inlet of a hydrogen separation cooling unit and the cooling freshwater inlet of an oxygen separation cooling unit, and the hydrogen purification cooling unit removes water, oxygen and other impurities by the principles of catalytic reaction, cooling and molecular sieve adsorption, ultimately purifying the hydrogen to a purity of 99.999%.

[0063] (Note 4) The seawater inlet of the negative pressure seawater desalination unit is a seawater entry passage. A water electrolysis hydrogen production system suitable for a floating offshore wind turbine as described in Appendix 1, characterized in that the generated freshwater outlet of a negative pressure seawater desalination unit is connected to the raw material freshwater inlet of a raw material freshwater storage and supply unit, the heated freshwater inlet of the negative pressure seawater desalination unit is connected to the outlet of a circulating freshwater transport unit, the heated freshwater outlet of the negative pressure seawater desalination unit is connected to the cooled freshwater inlet of a hydrogen purification and cooling unit, and the raw material freshwater outlet of the raw material freshwater storage and supply unit is connected to the raw material freshwater inlet of a hydrogen separation and cooling unit and the freshwater inlet of an expansion tank unit, respectively, to replenish the hydrogen separation and cooling unit and the expansion tank unit with raw material freshwater.

[0064] (Note 5) Further equipped with an expansion tank unit, A water electrolysis hydrogen production system suitable for a floating offshore wind turbine as described in Appendix 1, characterized in that the freshwater inlet of the expansion tank unit is connected to a raw material freshwater storage and supply unit, the freshwater outlet of the expansion tank unit is connected to the pipeline at the front end of the inlet of a circulating freshwater transport unit, and the expansion tank unit replenishes an appropriate amount of freshwater to the closed circulating freshwater pipeline when the closed circulating freshwater is depleted due to long-term operation.

[0065] (Note 6) The water electrolysis hydrogen production system for offshore floating wind turbines as described in Appendix 1, characterized in that the hydrogen separation cooling unit has a hydrogen gravity separation cooler, a hydrogen cooler, and a hydrogen gas-liquid separator, and the oxygen separation cooling unit has an oxygen gravity separation cooler, an oxygen cooler, and an oxygen gas-liquid separator.

[0066] (Note 7) The negative pressure seawater desalination unit comprises a negative pressure seawater desalination device, a water quality monitor, a salinity meter, a thermometer, a seawater temperature control valve, a saltwater temperature control valve, a condenser, a vacuum pump, and a seawater suction pump. The water electrolysis hydrogen production system for a floating offshore wind turbine as described in Appendix 1, is characterized in that the negative pressure seawater desalination apparatus performs negative pressure low-temperature seawater desalination, a water quality monitor detects whether the produced freshwater is acceptable or not, and if it is detected as acceptable, it flows into the raw freshwater tank, and if it is detected as unacceptable, it is returned to the negative pressure seawater desalination apparatus for further desalination, a salinity meter detects the salinity of the seawater in the negative pressure seawater desalination apparatus, a thermometer detects the temperature of the seawater in the negative pressure seawater desalination apparatus, a vacuum pump is controlled by a vacuum gauge to maintain the vacuum level in the negative pressure seawater desalination apparatus, a condenser condenses water vapor to protect the vacuum pump, and a seawater suction pump pumps up seawater from nearby and supplies seawater to the negative pressure seawater desalination apparatus.

[0067] (Note 8) It is further equipped with a seawater supply filtration unit, The export end of the seawater supply filtration unit is connected to a negative pressure seawater desalination unit, the seawater supply filtration unit consists of a seawater suction pump, a multimedia filter, an activated carbon filter, and a microfilter, the seawater suction pump pumps up seawater from nearby and supplies it to the negative pressure seawater desalination unit, and the multimedia filter, activated carbon filter, and microfilter remove some impurities from the seawater to reduce scale formation in the negative pressure seawater desalination unit, characterized in that this is a water electrolysis hydrogen production system suitable for a floating offshore wind turbine as described in Appendix 1 or 7.

[0068] (Note 9) A method for using a water electrolysis hydrogen production system suitable for a floating offshore wind turbine described in any one of the appendices 1 to 7, The process involves a step of decomposing the raw material freshwater in an alkaline electrolytic cell unit into hydrogen and oxygen by the action of DC power from a floating wind turbine, The process involves transporting oxygen and alkaline liquid to an oxygen separation and cooling unit via the oxygen outlet of the alkaline electrolytic cell unit for gas-liquid separation and cooling, guiding the oxygen from which the alkaline liquid has been removed to a safe area for discharge, transporting hydrogen and alkaline liquid to a hydrogen separation and cooling unit via the hydrogen outlet of the alkaline electrolytic cell unit for gas-liquid separation and cooling to remove the alkaline liquid, then introducing hydrogen and a small amount of water into a hydrogen purification and cooling unit to further purify the hydrogen to a hydrogen content of 99.999%, and finally supplying the obtained hydrogen to the transport line. The alkaline solution filtration and circulation unit completes the cooling and forced circulation of the alkaline solution by extracting the alkaline solution from the hydrogen separation and cooling unit and the oxygen separation and cooling unit, cooling it in the alkaline solution cooling unit, and finally transporting it to the alkaline electrolytic cell unit. A method for using a water electrolysis hydrogen production system suitable for offshore floating wind turbines, comprising the steps of: desalination of seawater using a negative pressure seawater desalination unit; connection of the generated freshwater outlet of the negative pressure seawater desalination unit to the raw material freshwater inlet of a raw material freshwater storage and supply unit; and the closed-loop circulating freshwater sequentially absorbing heat from the mediums requiring cooling in a hydrogen purification cooling unit, a hydrogen separation cooling unit, an oxygen separation cooling unit, and an alkaline liquid cooling unit during the alkaline water electrolysis hydrogen production process; and then entering the negative pressure seawater desalination unit via a circulating freshwater transport unit to heat the seawater, thereby carrying out negative pressure low-temperature seawater desalination.

[0069] (Note 10) The method of use described in Appendix 9, characterized in that when the closed-circulation freshwater system is depleted due to long-term operation, an appropriate amount of freshwater is replenished in the closed-circulation freshwater pipeline; when the freshwater in the expansion tank unit becomes insufficient, a valve is opened to replenish freshwater from the raw material freshwater storage and supply unit; freshwater produced by the negative-pressure seawater desalination unit is stored in the raw material freshwater storage and supply unit; freshwater is replenished in the hydrogen separation and cooling unit; raw material freshwater is supplied to the production of alkaline water electrolysis hydrogen; and freshwater is replenished in the expansion tank unit. [Explanation of symbols]

[0070] 1 Baseline, 2 Alkaline electrolytic cell unit, 3 Hydrogen separation cooling unit, 4 Hydrogen purification cooling unit, 5 Oxygen separation cooling unit, 6 Alkaline liquid filtration and circulation unit, 7 Alkaline liquid cooling unit, 8 Negative pressure seawater desalination unit, 9 Raw material freshwater storage and supply unit, 10 Expansion tank unit, 11 Circulating freshwater transport unit, 21 Alkaline electrolytic cell, 31 Hydrogen gravity separation cooler, 32 Hydrogen cooler, 33 Hydrogen gas-liquid separator, 51 Oxygen gravity separation cooler, 52 Oxygen cooler, 53 Oxygen vapor-liquid separator, 61 Alkaline liquid filter, 62 Alkaline liquid circulation pump, 71 Alkaline liquid cooler, 80 Vacuum gauge, 81 Negative pressure seawater desalination unit, 82 Water quality monitor, 83 Salinity meter, 84 Thermometer, 85 Seawater temperature control valve, 86 Saltwater temperature control valve, 87 Condenser, 88 Vacuum pump, 89 Seawater suction pump, 91 Raw material freshwater tank, 92 Raw material freshwater supply pump, 101 Expansion tank, 102 Remote control valve, 103 Liquid level monitoring transmitter, 111 Freshwater circulation pump.

Claims

1. A water electrolysis hydrogen production system suitable for a floating offshore wind turbine, comprising an alkaline electrolytic cell unit, an oxygen separation and cooling unit, a hydrogen separation and cooling unit, an alkaline liquid filtration and circulation unit, an alkaline liquid cooling unit, a negative pressure seawater desalination unit, and a circulating freshwater transport unit, The power interface of the alkaline electrolytic cell unit is connected to a floating offshore wind turbine, and the freshwater in the alkaline electrolytic cell unit is decomposed into hydrogen and oxygen by the action of DC power from the floating offshore wind turbine. The hydrogen and alkaline liquid enter the hydrogen separation cooling unit, and the oxygen and alkaline liquid enter the oxygen separation cooling unit. The alkaline liquid filtration and circulation unit separates the alkaline liquid from the oxygen separation and cooling unit and the hydrogen separation and cooling unit and circulates it to the alkaline electrolytic cell unit. The alkaline liquid cooling unit is installed between the alkaline liquid filtration and circulation unit and the alkaline electrolytic cell unit, and cools the alkaline liquid to the temperature range required by the electrolytic cell. The aforementioned negative pressure seawater desalination unit performs desalination of seawater under reduced pressure and supplies freshwater raw material for alkaline water electrolysis hydrogen production. The aforementioned circulating freshwater transport unit is a water electrolysis hydrogen production system suitable for offshore floating wind turbines, characterized in that it constructs a closed-loop freshwater circulation system, absorbs heat from a medium that requires cooling in alkaline water electrolysis hydrogen production using closed-loop freshwater, and utilizes that heat as a heat source for seawater desalination in a negative-pressure seawater desalination unit.

2. The water electrolysis hydrogen production system for a floating offshore wind turbine according to claim 1, characterized in that the alkaline liquid inlet of the alkaline electrolysis cell unit is connected to the alkaline liquid outlet of the alkaline liquid cooling unit, the hydrogen outlet of the alkaline electrolysis cell unit is connected to the hydrogen separation cooling unit, the oxygen outlet of the alkaline electrolysis cell unit is connected to the oxygen separation cooling unit, the alkaline liquid outlet of the oxygen separation cooling unit and the alkaline liquid outlet of the hydrogen separation cooling unit are connected and merge to form a main pipe which is connected to the alkaline liquid filtration and circulation unit, and the cooling freshwater outlet of the oxygen separation cooling unit is connected to the cooling freshwater outlet of the hydrogen separation cooling unit and then to the cooling freshwater inlet of the alkaline liquid cooling unit.

3. It is further equipped with a hydrogen purification cooling unit, The hydrogen inlet of the hydrogen separation cooling unit is connected to the hydrogen outlet of the alkaline electrolytic cell unit, the hydrogen outlet of the hydrogen separation cooling unit is connected to the hydrogen purification cooling unit, the cooling freshwater inlet of the hydrogen separation cooling unit is connected to the cooling freshwater inlet of the oxygen separation cooling unit, and then to the cooling freshwater outlet of the hydrogen purification cooling unit, the cooling freshwater outlet of the hydrogen separation cooling unit is connected to the cooling freshwater outlet of the oxygen separation cooling unit, and then to the cooling freshwater inlet of the alkaline liquid cooling unit, and the raw material freshwater inlet of the hydrogen separation cooling unit is connected to the freshwater source of the negative pressure seawater desalination unit, and hydrogen A water electrolysis hydrogen production system for offshore floating wind turbines according to claim 1, characterized in that the hydrogen outlet of the purification cooling unit is connected to a transport line, the cooling freshwater inlet of the hydrogen purification cooling unit is connected to the cooling freshwater outlet of a negative pressure seawater desalination unit, the cooling freshwater outlet of the hydrogen purification cooling unit is connected to the cooling freshwater inlet of a hydrogen separation cooling unit and the cooling freshwater inlet of an oxygen separation cooling unit, and the hydrogen purification cooling unit removes water, oxygen and other impurities by the principles of catalytic reaction, cooling and molecular sieve adsorption, ultimately purifying the hydrogen to a purity of 99.999%.

4. The seawater inlet of the negative pressure seawater desalination unit is a seawater entry passage. A water electrolysis hydrogen production system for a floating offshore wind turbine according to claim 1, characterized in that the generated freshwater outlet of a negative pressure seawater desalination unit is connected to the raw material freshwater inlet of a raw material freshwater storage and supply unit, the heated freshwater inlet of the negative pressure seawater desalination unit is connected to the outlet of a circulating freshwater transport unit, the heated freshwater outlet of the negative pressure seawater desalination unit is connected to the cooled freshwater inlet of a hydrogen purification and cooling unit, and the raw material freshwater outlet of the raw material freshwater storage and supply unit is connected to the raw material freshwater inlet of a hydrogen separation and cooling unit and the freshwater inlet of an expansion tank unit, respectively, to replenish the hydrogen separation and cooling unit and the expansion tank unit with raw material freshwater.

5. Further equipped with an expansion tank unit, A water electrolysis hydrogen production system suitable for a floating offshore wind turbine according to claim 1, characterized in that the freshwater inlet of the expansion tank unit is connected to a raw material freshwater storage and supply unit, the freshwater outlet of the expansion tank unit is connected to the pipeline at the front end of the inlet of a circulating freshwater transport unit, and the expansion tank unit replenishes an appropriate amount of freshwater to the closed circulating freshwater pipeline when the closed circulating freshwater is depleted due to long-term operation.

6. The hydrogen separation and cooling unit comprises a hydrogen gravity separation cooler, a hydrogen cooler, and a hydrogen gas-liquid separator, and the oxygen separation and cooling unit comprises an oxygen gravity separation cooler, an oxygen cooler, and an oxygen gas-liquid separator, characterized in that it is a water electrolysis hydrogen production system suitable for a floating offshore wind turbine according to claim 1.

7. The negative pressure seawater desalination unit comprises a negative pressure seawater desalination device, a water quality monitor, a salinity meter, a thermometer, a seawater temperature control valve, a saltwater temperature control valve, a condenser, a vacuum pump, and a seawater suction pump. The negative pressure seawater desalination apparatus performs negative pressure low-temperature seawater desalination; a water quality monitor detects whether the generated freshwater is acceptable or not; if it is acceptable, it is allowed to flow into the raw freshwater tank; if it is unacceptable, it is returned to the negative pressure seawater desalination apparatus for further desalination; a salinity meter detects the salinity of the seawater in the negative pressure seawater desalination apparatus; a thermometer detects the temperature of the seawater in the negative pressure seawater desalination apparatus; a vacuum pump is controlled by a vacuum gauge to maintain the vacuum level in the negative pressure seawater desalination apparatus; a condenser condenses water vapor to protect the vacuum pump; and a seawater suction pump pumps up seawater from nearby and supplies it to the negative pressure seawater desalination apparatus, characterized in that this is a water electrolysis hydrogen production system suitable for a floating offshore wind turbine according to claim 1.

8. It is further equipped with a seawater supply filtration unit, The export end of the seawater supply filtration unit is connected to a negative pressure seawater desalination unit, the seawater supply filtration unit consists of a seawater suction pump, a multimedia filter, an activated carbon filter, and a microfilter, the seawater suction pump pumps up seawater from nearby and supplies it to the negative pressure seawater desalination unit, and the multimedia filter, activated carbon filter, and microfilter remove some impurities from the seawater to reduce scale formation in the negative pressure seawater desalination unit, characterized in that a water electrolysis hydrogen production system suitable for a floating offshore wind turbine according to claim 1 or 7.

9. A method for using a water electrolysis hydrogen production system suitable for a floating offshore wind turbine according to any one of claims 1 to 7, The process involves a step of decomposing the raw material freshwater in an alkaline electrolytic cell unit into hydrogen and oxygen by the action of DC power from a floating wind turbine, The process involves transporting oxygen and alkaline liquid to an oxygen separation and cooling unit via the oxygen outlet of the alkaline electrolytic cell unit for gas-liquid separation and cooling, guiding the oxygen from which the alkaline liquid has been removed to a safe area for discharge, transporting hydrogen and alkaline liquid to a hydrogen separation and cooling unit via the hydrogen outlet of the alkaline electrolytic cell unit for gas-liquid separation and cooling to remove the alkaline liquid, then introducing hydrogen and a small amount of water into a hydrogen purification and cooling unit to further purify the hydrogen to a hydrogen content of 99.999%, and finally supplying the obtained hydrogen to the transport line. The alkaline solution filtration and circulation unit completes the cooling and forced circulation of the alkaline solution by extracting the alkaline solution from the hydrogen separation and cooling unit and the oxygen separation and cooling unit, cooling it in the alkaline solution cooling unit, and finally transporting it to the alkaline electrolytic cell unit. A method for using a water electrolysis hydrogen production system suitable for offshore floating wind turbines, comprising the steps of: desalination of seawater using a negative pressure seawater desalination unit; connection of the generated freshwater outlet of the negative pressure seawater desalination unit to the raw material freshwater inlet of a raw material freshwater storage and supply unit; and the closed-loop circulating freshwater sequentially absorbing heat from the mediums requiring cooling in a hydrogen purification cooling unit, a hydrogen separation cooling unit, an oxygen separation cooling unit, and an alkaline liquid cooling unit during the alkaline water electrolysis hydrogen production process; and then entering the negative pressure seawater desalination unit via a circulating freshwater transport unit to heat the seawater, thereby carrying out negative pressure low-temperature seawater desalination.

10. The method of use according to claim 9, characterized in that when the closed-circulation freshwater system is depleted due to long-term operation, an appropriate amount of freshwater is replenished in the closed-circulation freshwater pipeline, when the amount of freshwater in the expansion tank unit becomes insufficient, a valve is opened to replenish freshwater from the raw material freshwater storage and supply unit, freshwater produced by the negative-pressure seawater desalination unit is stored in the raw material freshwater storage and supply unit, freshwater is replenished in the hydrogen separation and cooling unit, raw material freshwater is supplied to the production of alkaline water electrolysis hydrogen, and freshwater is replenished in the expansion tank unit.

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