Offshore electrolysis system and methods for operating an offshore electrolysis system

Abstract

The invention relates to an offshore electrolysis system (100) comprising a wind turbine (1) with a platform (3) and with an electrolysis plant (5) arranged on the platform (3), which is connected to the wind turbine (1) for supplying electrolysis current, and further comprising a water supply device (7) connected to the electrolysis plant (5), which has a water collector (13) which is designed in such a way that water with no or only very small amounts of salts can be obtained independently of seawater, which can be used as feed water for operating the electrolysis plant (5). The invention further relates to a method for operating a corresponding offshore electrolysis system (100), wherein water is obtained in a water collector (13) independently of seawater in a quality in which the obtained water contains no or only very small amounts of salts.

Description

[0001] The invention relates to an offshore electrolysis system and a method for operating an offshore electrolysis system.

[0002] An electrolysis plant is a device that uses electrical current to effect a material transformation (electrolysis). Due to the variety of different electrochemical electrolysis processes, there are also a variety of electrolysis plants, such as an electrolysis plant for water electrolysis. Electrolysis plants are connected to power generation plants to supply direct current with electrolysis current, thus forming an electrolysis system. Typically, an electrolysis plant comprises several electrolyzers, so that with appropriate scaling, high electrolysis capacities for electrochemical material conversion can be achieved.

[0003] Hydrogen is currently produced from water using processes such as proton exchange membrane (PEM) electrolysis or alkaline electrolysis. These electrolysis systems use electrical energy to produce hydrogen and oxygen from the supplied water. This process takes place in an electrolysis stack composed of several electrolysis cells. Water is introduced as the reactant into the electrolysis stack, which is under DC voltage. After passing through the electrolysis cells, two fluid streams emerge, consisting of water and gas bubbles (O2 and H2, respectively).

[0004] Current considerations are to use surplus energy from renewable energy sources during periods of abundant sun and wind, i.e., when solar or wind power generation is above average, to generate valuable materials. One such valuable material could be hydrogen, which is produced by water electrolysis plants. Hydrogen can, for example, be used to produce so-called renewable gas. A renewable gas is a combustible gas obtained from renewable sources using electrical energy.

[0005] Hydrogen represents a particularly environmentally friendly and sustainable energy source. It has the unique potential to realize energy systems, transport, and large parts of the chemical industry without CO2 emissions. For this to succeed, however, the hydrogen cannot come from fossil sources, but must be produced using renewable energy.

[0006] One source of renewable energy is wind power. Large electrical outputs can be achieved, particularly with coastal, so-called offshore wind turbines. However, the challenge is that consumers have to be located far away. The energy must therefore be transported to the consumer with as little loss as possible. Hydrogen is a particularly suitable transport medium. It can be transported in gaseous form, for example, through pipelines. A positive side effect is that a hydrogen-carrying pipeline can also serve as an energy storage device, since the internal pressure can be varied within certain limits. For this reason, it is particularly interesting to produce hydrogen directly at the site of energy generation, i.e., to locate offshore electrolysis plants directly at or in the immediate vicinity of offshore wind turbines.For example, offshore electrolysis systems are currently being discussed, in which an electrolysis plant is installed directly on the platform of an offshore wind turbine. The wind turbine can be interconnected with the electrolysis plant to form a largely self-sufficient, i.e., virtually grid-independent, electrolysis system, and can be specifically equipped for offshore island operation.

[0007] In the best case, these electrolysis systems, comprising a combination of a wind turbine and an electrolysis plant, can be constructed entirely without any auxiliary connection to a power grid for supply and can be upgraded exclusively for island operation. This particularly applies to electrolysis systems constructed far offshore in order to avoid long connection routes to the public grid of the coastal region. The electrolysis plant with a number of electrolyzers is ideally located in the immediate vicinity of the renewable energy source, i.e. the wind turbine, in order to reduce or avoid both transformation and line losses. For this reason, offshore electrolysis systems with electrolysis plants that are installed directly on a platform with an offshore wind turbine are currently being developed with great intensity.With such a coupling, whether onshore or offshore, the system can be operated without a connection to the power grid. Without a grid connection, however, during periods of calm, lulls, or scheduled maintenance, for example, on the wind turbine's turbine, no power is available from the generator or the power grid.

[0008] In offshore electrolysis systems, special attention must also be paid to preventing corrosion of the electrolysis system, as the presence of saltwater can lead to significantly higher corrosion rates, jeopardizing the long-term uninterrupted operation of an electrolysis system. In principle, offshore electrolysis systems can be equipped with electrolyzers and housed within closed enclosures, known as containers. This can provide a certain degree of protection for the electrolyzer from external environmental influences. However, for operational reasons, the electrolyzer must be cooled during normal operation to continuously dissipate the waste heat generated from the electrolysis process to the environment.In general, compared to onshore electrolysis plants, heat management in offshore electrolysis plants is particularly challenging, both with regard to the necessary cooling during normal operation and maintaining a minimum temperature during extended downtimes. In the latter operating mode, sufficient freeze protection for the water-soaked electrolyzer cells of the electrolyzers must be ensured, especially during periods of low wind and shutdown of the wind turbine during the winter months. Therefore, with regard to cooling requirements during normal operation of offshore electrolysis plants, at least a closed container design, i.e., an enclosure to protect the electrolyzer, is established. This requires, on the one hand, preventing overheating and failure of the electrolyzers and, on the other hand, damaging corrosion due to exposure to marine salt.Thus, in an offshore electrolysis plant, an interface and exchange between the electrolyzer and the environment is ultimately unavoidable in order to appropriately dissipate the heat flow of the process heat during normal operation and to enable safe operation.

[0009] To protect the electrolyzers from environmental influences, they require an enclosure such as a container, as explained above. Water management is particularly challenging in an offshore electrolysis system based on the electrolysis of water. The internal temperature of the container must therefore not fall below approximately 5°C. Otherwise, the water-bearing components, which contain water, can freeze and paralyze the operation of the entire system. This would contradict the goal of low-maintenance and self-sufficient operation of offshore electrolysis systems with wind turbines without grid connection.

[0010] Electrolysis systems with water electrolyzers, especially PEM water electrolyzers, must be operated with demineralized and ultrapure water as the reactant. Even with alkaline electrolysis, for example, based on aqueous concentrated potassium hydroxide as the reactant, the requirements for the purity and quality of the water or the aqueous alkali solution are very high. Therefore, in addition to heat management, water management in an offshore electrolysis system is particularly demanding to ensure continuous operation and a supply of reactant water of high quality and purity.

[0011] The object of the present invention is to provide an offshore electrolysis system designed for improved supply of reactant water, with increased production efficiency in hydrogen production compared to known approaches. A further object is to provide a method for operating an offshore electrolysis system.

[0012] The object directed to an offshore electrolysis system is achieved according to the invention by an offshore electrolysis system comprising a wind turbine with a platform and with an electrolysis system arranged on the platform, which is connected to the wind turbine for supplying electrolysis current, and further comprising a water supply device connected to the electrolysis system, which has a water collector which is designed in such a way that water with no or only very small amounts of salts can be obtained independently of seawater, which water can be used as reactant water for operating the electrolysis system.

[0013] The object directed to a method for operating a corresponding offshore electrolysis system is achieved according to the invention by a method for operating an offshore electrolysis system, wherein water is obtained in a water collector independently of seawater in a quality in which the water obtained contains no or only very small amounts of salts.

[0014] The advantages and preferred designs of an offshore electrolysis system listed below can be applied analogously to the method for operating the electrolysis system.

[0015] The offshore electrolysis system and its operating procedure significantly improve the energy consumption for water supply and water treatment with reactant water for operating the electrolysis plant. This allows reactant water of high purity and quality to be provided and continuously fed into the electrolysis process as needed. At the same time, safe, environmentally friendly, and self-sufficient operation is possible, as well as low-maintenance. The water supply system is both low-maintenance and low-intervention, as it is independent of seawater and requires virtually no recourse to seawater.

[0016] The invention is based on the fact that, in addition to electricity, water is also required to split water in electrolysis. To produce approximately one kilogram of hydrogen, at least nine liters of water are needed. And consumption can increase significantly if the water has to be treated, i.e., desalinated or deionized. In all large-scale electrolysis processes such as PEM or alkaline electrolysis, the water must meet certain purity requirements, as the impurities or foreign ions that are continuously added to the process water cycle would otherwise accumulate in the water-bearing system. Seawater has an average salt content of 3.5% by mass. The salt content varies depending on the sea. The Baltic Sea, for example, has a salt content of 0.2 to 2%, and the Dead Sea has a salt content of 28%. There are also studies on the use of seawater as an electrolyte in electrolysis.However, the salt concentration and the poorly soluble components have so far only allowed for short operating times under laboratory conditions. Desalination and purification of seawater are currently essential for large-scale commercial electrolysis plants and require high energy consumption. This energy requirement for the provision of fully demineralized, high-purity reactant water has a significant negative impact on the hydrogen production efficiency of an offshore electrolysis system relative to the electrical power used by the wind turbine.

[0017] The increasing number of more powerful off-grid offshore wind turbines being installed or planned, and their growing electrical generation capacity, require correspondingly more powerful electrolysis systems and correspondingly higher water consumption. The power class of offshore electrolysis systems and their number are expected to increase significantly in the future.

[0018] The associated increasing demands for safe and environmentally friendly operation in a maritime environment must be considered. Due to the scaling efforts toward larger offshore electrolysis systems far offshore, the question of the most self-sufficient, i.e., grid-independent, island operation with 100% hydrogen production from renewable wind power, along with the environmental compatibility of such systems, is becoming a focus of discussion. On the one hand, from an environmental perspective, the least-intrusive operation possible must be ensured, also with regard to the maritime ecosystem. A self-sufficient yet minimally intrusive solution for a secure water supply for the electrolysis plant is therefore crucial for the energy and ecological balance.

[0019] The concept of the invention ensures a water supply and replenishment, minimizing the need for reliance on seawater. A separate water collector is provided, allowing salt-free water to be collected and extracted from natural sources independently of seawater. This significantly reduces the treatment effort compared to seawater. Depending on the maritime location of the offshore electrolysis system, water volumes are harnessed and fed into the electrolysis process. The water collector of the water supply system is designed according to the required or harvestable water volume in terms of the collection volume and effective collection area.

[0020] The offshore electrolysis system of the invention advantageously recognizes and overcomes for the first time the disadvantages of conventional water supply concepts for off-grid electrolysis systems, which – as described above – require very large amounts of energy and plant engineering for seawater desalination and treatment. Seawater desalination is the extraction of drinking water and process water for industrial or power plants from seawater (salt water) by reducing the salt content. Desalination can be based on various processes that remove dissolved minerals from the water. In some cases, usable byproducts such as table salt are produced. The energy consumption for the multi-stage flash evaporation of seawater is 23-27 kWh / m³. 3 , approx. 90 MJ / m 3With reverse osmosis, approximately 2 kWh to 4 kWh per cubic meter of drinking water must be expected. The physical minimum is 1.9 kWh per cubic meter. However, the membranes of a reverse osmosis system are not maintenance-free. The formation of deposits caused by mineral deposits (scaling), biological substances (biofouling), or colloidal particles reduces the permeation of water molecules through the membranes. The concept of a water collector integrated into the electrolysis system according to the invention overcomes these disadvantages. Possible recourse to seawater and the associated system and energy expenditure is significantly reduced. At most, the water supply facility can additionally have a recourse to seawater as needed for emergency supplies. However, this can then be significantly smaller in terms of system dimensions than conventional water supply systems.In this respect, a hybrid water supply system is also possible with the offshore electrolysis system. However, priority is usually given to water extraction via the water collector, independent of seawater.

[0021] In a particularly preferred embodiment of the offshore electrolysis system, the water supply device comprises an intermediate storage device which is provided on the platform and / or installed within the tower of the wind turbine, wherein the intermediate storage device is connected to the water collector.

[0022] Pumps can be provided here if necessary to transport the water collected in the water collector from the water collector into an intermediate storage tank, thereby regularly emptying the water collector, at least partially, depending on the water yield and fill level in the water collector. In this way, a water supply can be created and kept available for further purposes. By installing it in the tower - similar to a cistern - a cavity is very advantageously provided without taking up additional installation space on the platform. Therefore, the intermediate storage tank can be quite simply formed or incorporated as a cavity within the tower of the wind turbine itself. The intermediate storage tank is therefore preferably embedded deep below the water surface within the tower in order to utilize the most constant and frost-free ambient temperature in the intermediate storage tank below the water level.At the same time, the installation of an intermediate storage unit in a cavity deep inside the tower barely impacts the mechanical stability of the tower structure and the nacelle with the wind turbine. Furthermore, installation space is created or advantageously utilized for the intermediate storage unit, as this space would otherwise remain unused. With this design, the intermediate storage unit requires no surface area or installation space on the platform itself; the latter can be used without restriction by the water supply system for the electrolysis plant and its components.

[0023] Appropriate storage volumes for an intermediate storage facility can also be achieved using water tanks installed beneath the platform. Depending on the geographic location of the electrolysis system, these water tanks are thermally insulated to prevent the risk of frost and freezing of the stored water. The intermediate storage facility ensures that the water collector is regularly emptied or discharged, while simultaneously maintaining a sufficient amount of water to cover at least several days of electrolysis demand. This allows even phases with low yield of collected water in the water collector to be safely bridged.

[0024] In a particularly preferred embodiment of the offshore electrolysis system, a cleaning device is provided which is connected to the intermediate storage via a withdrawal line.

[0025] This creates the opportunity to treat and purify the water collected in the water collector and stored in the intermediate storage tank for use in the electrolysis system. While the water originally collected in the water collector already has very low or no salt content, suspended particles, impurities, and small amounts and residues of water-soluble ions may be present. Depending on the location of the electrolysis system, cations such as sodium ions (Na) may be present. + , potassium ions K + , magnesium ions Mg 2+ , calcium ions Ca 2+ , ammonium ions NH4 + may be present in the collected water. Cations such as chloride ions Cl - , nitrate ions NO3 - or sulfate ions SO4 -be introduced or dissolved. Due to the already high purity of the collected water, contamination with these substances is low. Therefore, the purification system can be designed and dimensioned significantly smaller than a comparable seawater treatment plant. Furthermore, significantly less energy is required from the wind turbine, since the collected water already has a high degree of purification. Therefore, the electrical power generated in the offshore wind turbine can be used predominantly as electrolysis current, thus increasing the production efficiency of hydrogen from the electrolysis of water in relation to the available electrical energy.

[0026] In a preferred embodiment of the offshore electrolysis system, the cleaning device is connected to a storage tank via a storage line, so that treated water can be supplied to the storage tank as reactant water and made available for the operation of the electrolysis plant.

[0027] The water extracted and treated in the purification system is stored in a storage tank. This tank is located downstream of the purification system. The purified reactant water is stored via a storage line. The storage tank keeps treated, fully demineralized reactant water ready, allowing the feed and replenishment of reactant water into the electrolysis plant's process water circuit as needed.

[0028] For this purpose, in a preferred embodiment of the offshore electrolysis system, the storage tank is connected to the electrolysis plant via a feed line.

[0029] A feed pump is provided in the feed line for feeding, refilling, or supplementing the process water with prepared reactant water into the process water circuit. Additionally, a controllable dosing valve can be connected to the feed line to ensure precise dosing and balancing of reactant water according to the conversion and water consumption in the electrolysis process. Depending on the system design, reactant water can be fed in either on the anode or cathode side of an electrolyzer for water electrolysis.

[0030] In a particularly preferred embodiment of the offshore electrolysis system, the water collector comprises a rainwater collector which is designed for rainwater collection.

[0031] In this way, rainwater, for example, can be obtained as precipitation water, which is collected via an appropriately dimensioned rainwater collector with a large collection area.

[0032] Preferably, the rainwater collector comprises a basin, wherein the basin is mounted on a platform and / or arranged floating on the sea.

[0033] The basin is a catchment basin and can be located on a separate offshore platform adjacent to the offshore electrolysis system platform and serving as a supply platform. In addition to the basin, this supply platform can also accommodate an intermediate storage facility for the rainwater and, if necessary, other elements of the water supply system. The intermediate storage facility can preferably be suspended below the platform with an intermediate storage volume of, for example, 100–500 m³. 3The intermediate storage tank allows the rainwater collected in the catch basin to be temporarily stored and kept ready for a subsequent treatment step. The basin has a large collection area of ​​at least several hundred meters. 2 for example 500m 2 -1000m 2 . Multiple collection basins can also be provided to increase the yield. The rainwater collector is flexibly scalable to meet projected water demand. Assuming an average annual rainfall of 500 l / m 2 can thus 50m 3 Water per 100m 2 The water is collected in the basin's collection area. It is also possible for a large offshore electrolysis system to supply several electrolysis plants located on a platform from a central water supply facility with a water collector.

[0034] In a particularly preferred embodiment of the offshore electrolysis system, the water collector has a condensation device which is designed for condensing moisture-saturated air.

[0035] This creates an alternative, or additional, option to harvest water from the condensation of humid ambient air. The moisture condenses and can be collected as water. It is possible to harvest moisture, and thus water, from the ambient air of the offshore electrolysis system through condensation or even within the system components. It is also possible to integrate the condensation system on the platform supporting the electrolysis system or to construct it as a supply platform on a dedicated offshore platform. The supply platform then forms part of the water supply system. In the condenser, moisture-saturated air is cooled, and as the temperature falls below the dew point, the gaseous water vapor is converted into droplets.

[0036] Preferably, the offshore electrolysis system comprises a condensation device having a mist collector, which has a fine-meshed, large-area net as a collector, in particular nylon or polypropylene nets.

[0037] The term fog condensation also refers to water extraction through the assisted condensation of water vapor using fog collectors. Research and experience with the use of fog collectors have significantly increased their effectiveness in water recovery, making their use as water collectors in the water supply system of an offshore electrolysis plant both practical and advantageous. For example, if a cold ocean current reaches the sea surface off a coast, the humidity carried by onshore winds condenses there due to the temperature falling below the dew point and transforms into water mist. The choice of materials, mesh sizes, and fabric shapes (dimpled, porous, and honeycomb structures) used to collect water droplets from the fog are important for the effectiveness of the fog collectors used to collect the water droplets from the fog.This is flexibly scalable and its dimensions can be adapted to the water requirements of the electrolysis plant via the effective area and yield.

[0038] In an alternative or additional embodiment of the offshore electrolysis system, the condensation device comprises a condensation dryer, wherein a condensation dryer is arranged within the tower or nacelle of the wind turbine.

[0039] Compared to the mist collector as a surface collector, the local extraction and separation of moisture from the immediate operating environment of functional elements of the offshore electrolysis system can be very practical and advantageous. On the one hand, this protects the active components of the wind turbine, such as the electrical components in the nacelle or tower, from moisture damage or short circuits. Likewise, moisture must be avoided for the electrolyzer, the electrolysis cells, and the electrical supply systems of the electrolysis plant in order to avoid and, if possible, prevent corrosion or damage to the electrical components. Therefore, a dry operating environment, i.e., dry ambient air in an operating room or housing, is particularly important for long-term functional stability. On the other hand, condensation dryers can extract water that is practically salt-free.Condensation drying is a dehumidification process commonly used in both industrial and residential applications, for example, in tumble dryers or conventional construction dryers. Fans circulate moist air over cooling fins / louvers whose temperature is below the air's dew point. The water condenses and collects as condensate on the cold surface, which is then collected in a separate container. The cooled and dehumidified air is then heated and released as dry air. The advantage of the condensation dryer is that it is installed locally and integrated into the water supply system. The condensation dryer is easily powered by electrical energy generated by the wind turbine.

[0040] In a particularly preferred embodiment of the offshore electrolysis system, the electrolysis plant comprises an electrolyzer arranged in a container and a condensation device, so that condensation of moisture can be brought about in the container and dry operating conditions are achieved.

[0041] This advantageously creates a defined, dry operating environment, and the container provides an operating space for the electrolyzer. The container design protects the electrolyzer from harmful environmental influences, particularly salt ingress. This is a preferred setup for offshore electrolyzer operation, with the container located on the platform. The condensation system within the container is adjusted so that the relative humidity is always less than 40%, preferably even less than 30%, typically between 15-25%. The permissible operating humidity is thus observed and reduced to a minimum value.The condensate water from the condensation device is used in an analogous manner, as described above, via intermediate storage in the intermediate storage, cleaning in the cleaning device and storage in the storage tank, so that treated reactant water of good quality is available for electrolysis purposes in the storage tank.

[0042] In a particularly preferred embodiment of the offshore electrolysis system, an island network is implemented without connection to an electrical supply network.

[0043] This design of the offshore electrolysis system achieves off-grid operation, which is of particular economic interest. The hydrogen is produced in a water electrolysis process directly at the energy generation site, meaning that offshore electrolysis systems are located directly next to or in close proximity to offshore wind turbines. This interconnects the wind turbine and electrolysis system to form a self-sufficient, i.e., virtually off-grid, electrolysis system, specifically equipped for offshore island operation. Battery units can be provided to bridge periods of low wind and maintain minimal operation of system-relevant functions of the electrolysis system.

[0044] In a further preferred embodiment of the offshore electrolysis system, the electrolysis plant comprises an electrolyzer for water electrolysis, which is based on a proton exchange membrane (PEM) electrolysis or on an alkaline electrolysis and with hydrogen (H2) as product gas.

[0045] In the case of PEM electrolysis, demineralized water can be obtained as a reactant independent of seawater by integrating the water supply system into the offshore electrolysis system. Alkaline electrolysis also requires ultrapure water as a solvent for the hydroxide in the lye preparation. In alkaline electrolysis, potassium hydroxide (KOH) in aqueous solution, formed as potassium hydroxide solution, is usually used as the reactant liquid.

[0046] This allows for combinations of different electrolyzers for water electrolysis in the offshore electrolysis system, if required, and can be adapted depending on the utilization concept. While alkaline electrolyzers can ideally be operated quasi-stationarily at rated power, PEM electrolyzers are capable of operating at part-load, especially at lower partial loads below 30% of rated power. Hydrogen and oxygen are produced as product gases in both technologies. In addition to its intended transport via a pipeline and further use onshore, some of the hydrogen is temporarily stored on the platform in local hydrogen storage facilities.

[0047] A further aspect of the invention relates to a method for operating a corresponding offshore electrolysis system.

[0048] In this process, water is extracted from a water collector independently of seawater in a quality that means the extracted water contains no or only very small amounts of salt.

[0049] The process can be carried out advantageously in a self-sufficient manner, i.e. without substantial recourse to seawater and operation of a large seawater desalination plant, which is usually required to obtain reactant water.

[0050] In an advantageous embodiment of the process, rainwater is collected and / or water is obtained from condensation of moisture-saturated air.

[0051] This provides a particularly efficient method for obtaining reactant water of sufficient quantity and quality. Rainwater is generated regularly during offshore installations, with several hundred liters per meter being generated depending on the forecast. 2and year. This amount of precipitation can be utilized advantageously. In addition to or as an alternative to rainwater harvesting, the process utilizes the condensation of moisture from the ambient air outside and inside the electrolysis system. The resulting and recovered condensate is of good quality and can be used.

[0052] For this purpose, the process preferably provides for the water obtained to be treated and the treated water to be fed to the electrolysis plant as reactant water.

[0053] This allows for the on-demand and demand-based replenishment of treated reactant water. Current replenishment can be controlled so that, depending on the electrolysis output and the associated water consumption, a certain level is maintained in the electrolyzer, ensuring that the electrolysis cells are supplied with reactant water.

[0054] For this purpose, a control and regulation device is provided as well as corresponding feed pumps and control valves. Fig. 1 an offshore electrolysis system with an electrolysis plant and a wind turbine; Fig. 2 schematic representation of elements of the process of seawater-independent water extraction based on functional elements of the water supply facility; Fig. 3 a schematic side view of an offshore electrolysis system with water supply device; Fig. 4 an offshore electrolysis system with rainwater collector; Fig. 5 a condensation device equipped as a mist collector.

[0055] The same reference symbols have the same meaning in the figures.

[0056] In Fig. 1, an offshore electrolysis system 100 is shown. The offshore electrolysis system 100 comprises an electrolysis plant 5 and a wind turbine 1 having a tower 19 and a turbine rotor, as shown in the upper right part of Fig. 1. In the lower part of the tower 19 there is a platform 3 above the sea level 25 (see Fig. 4 and Fig. 5) which is specifically designed and constructed to accommodate various equipment components for the intended operation of the offshore electrolysis system 100. These equipment components are located in the lower part of the Fig. 1 shown in an enlarged view as an example: An electrolysis plant 5 is installed on platform 3 and is systemically connected to the wind turbine 1 to form the offshore electrolysis system 100. For this purpose, containers 9 are installed on platform 3, in which electrolysis elements (not shown in detail) such as individual electrolyzers are housed, thus protecting particularly sensitive functional components of the electrolysis plant 5 from the effects of the weather. Some of the containers 9 installed on platform 3 contain control devices 27 or so-called "balance-of-plant" elements and protectively house them. These are selected containers 9 that are usually reserved for the sole accommodation and operation of these control devices 27 and, if applicable, other auxiliary systems of the electrolysis plant 5. In contrast, the electrolyzers for the electrochemical material conversion are arranged in containers 9 specifically provided for this purpose.Other components or parts of the system accommodated in the containers 9 may also include storage containers for electrolyte solution for operating the electrolyzers, or in particular demineralized water or potassium hydroxide solution in the case of a PEM or optionally alkaline water electrolysis of the electrolyzers, or the like.

[0057] In this case, the wind turbine 1 preferably has no grid connection or grid coupling, but rather, in the self-sufficient offshore electrolysis system 100, supplies the captured wind energy directly to the described electrolysis system 5, which is designed to produce preferably green hydrogen from water electrolysis. Thus, the offshore electrolysis system 100 is designed for off-grid island operation and equipped for self-sufficient use in regions farther from the coast. The wind turbine 1 is therefore an offshore wind turbine.

[0058] The strategy of providing the electrolysis plant 5 via a number of containers 9, preferably ISO containers, advantageously ensures a simple maintenance and repair process, and at the same time protects the plant components from climatic and weather influences as well as from corrosion and damaging mechanical influences during operation.

[0059] To operate the offshore electrolysis system 100 with water electrolysis, a sufficient amount of demineralized water, so-called deionized water, of high purity is required. Due to consumption, this water must be continuously replenished into the process water circuit of the electrolysis plant 5. Typically, only saline seawater is available on such an offshore electrolysis plant 100. However, in order to use the water taken from the sea, the seawater must be desalinated. A variety of desalination processes are available for this purpose, such as reverse osmosis or vacuum distillation, all of which, however, require considerable amounts of electrical energy. The use of electrical energy for desalination significantly reduces the efficiency of the overall plant and should therefore be kept to a minimum.

[0060] This disadvantage is counteracted by the invention with a water supply device 7, which is advantageously integrated into the electrolysis system 100 or connected thereto. Thus, it is possible - as in Fig. 1 merely schematically indicates that the water supply device 7 is at least partially housed in a selected container 9 of the offshore electrolysis system 100, or that a container 9 contains certain system components or functional elements of the water supply device 7. The water supply device 7 is coupled to the electrolysis system 5 and configured such that, by means of the water supply device 7, high-quality water can be supplied to the electrolysis system 5 independently of seawater use, so that continuous electrolysis operation is nevertheless achieved. Precipitation water, in particular rainwater, and alternatively or additionally condensation water extraction are used. This water is collected or extracted and treated at the installation site of the offshore electrolysis system 100 or in its immediate vicinity.

[0061] The process of seawater-independent water extraction and the functional elements of the water supply facility 7 are described below using the example of Fig. 2 in a flow diagram. The water supply device 7 has a water collector 13, which is appropriately configured for the collection of rainwater or condensation water from the air L. The water collector 13 is designed as a rainwater collector 41 or as a condensation device 43, although combinations of these designs are also possible. A sufficiently dimensioned intermediate storage tank 15 is connected downstream of the water collector 13, into which collected water H2O can be introduced and stored. This creates a water supply and the water collector 13 can be emptied continuously or on a regular basis. For this purpose, the water collector 13 is connected to the intermediate storage tank 15 and, if necessary, conveying devices such as pumps or valves are provided so that the collected water H2O can be conveyed into the intermediate storage tank 15.If the installation of the water collector 13 allows it due to a set height difference, an independent discharge of water (H2O) from the water collector 13 into the intermediate storage tank 15 can also be effected. A purification device 11 is arranged downstream of the intermediate storage tank 15 via a withdrawal line 17. The purification device 11 comprises elements and structures for water purification and water treatment, such as filters and desalination devices. In this way, impurities in the collected water (H2O) can be removed, as well as residual salts. Due to the already good quality and purity of the water (H2O) collected through precipitation or condensation, the desalination devices are significantly smaller than those used for seawater desalination.The desalination effort is considerably lower than with seawater desalination, and the system expenditure for installation as well as the energy requirement for operating the purification device 11 are correspondingly reduced. These savings are immediately available as electrical power for electrolysis purposes. The purification device 39 is connected to a storage tank 39 via a storage line 21. Fully demineralized water H2O, so-called deionized water or demineralized water, can be stored and kept in the storage tank 39. This water H2O has the required high quality and purity to be made available as reactant water 23 for water electrolysis in the storage tank 39. During operation of the electrolysis system 5, the reactant water 23 obtained from rainwater or condensation water is fed to the electrolysis system 5 via a feed line 37 and introduced into an electrolyzer.A membrane 45 or diaphragm separates the anode compartment 47 from the cathode compartment 49. This allows the reactant water 23 to be electrochemically split, forming oxygen O2 on the anode side and hydrogen H2 on the cathode side. Hydrogen H2 is the product gas of interest from the electrolysis. It is compressed, temporarily stored if necessary, and transported ashore via pipelines or transport ships.

[0062] Fig. Figure 3 shows a schematic side view of the offshore electrolysis system 100 with a wind turbine 1 and with a platform 3 and with an electrolysis plant 5 arranged on the platform 3. The platform 3 is attached to the tower 19 above sea level 25 in an above-water area 29. The electrolysis plant 5 has a number of containers 9, each with at least one electrolyzer arranged therein. The offshore electrolysis system 100 shown here is very advantageously equipped with an integrated water supply device 7, which is only shown in part here. For details of the functional elements, see Fig. 2. Here, the water supply device 7 has an intermediate storage 15, so that from the water collector 13 (see Fig. 2) Water H2O obtained from precipitation or condensation can initially be stored in an intermediate storage tank 15 and, if required, can be fed as water H2O after treatment for electrolysis purposes to the electrolysis plant 5 and can be electrochemically converted there. A condensation device 43 is arranged in the nacelle of the wind turbine 1 and at least in one container 9. The condensation device 43 is designed as a condensation dryer. It is also possible for a condensation device 43 to be arranged in the tower 19 of the wind turbine 1. After cleaning and water treatment, the demineralized water H2O is transferred to specially designed and provided storage tanks 39 and kept there as high-quality reactant water 23 for the electrolysis process.The water supply system 7 is arranged as individual elements on the platform 3 or in the tower 19 and can also be housed in one of the containers 9 together with equipment of the electrolysis system 5, such as an electrolyzer. The tower 19 extends from the above-water area 29 into an underwater area 31 and is firmly anchored in the seabed 35 by means of a foundation 33.

[0063] The intermediate storage 15 and the storage tank 39 are container-shaped, for example in the form of tubes made of lined metal or low-diffusion plastic material. The intermediate storage 15 and a storage tank 39 containing reactant water 23 are suspended below the platform 3, so that no installation space is required on the platform 3 itself. Furthermore, a cavity is formed within the tower 19 of the wind turbine 1 – in this case, incorporated deep below sea level 25 within the foundation 33 – and has a corresponding storage volume for the high-quality reactant water 23. A pressure-resistant, water- and diffusion-tight storage tank 39 is inserted into this cavity. Thus, during ongoing operation of the offshore electrolysis system 100, high-purity reactant water 23 can be stored in the storage tank 39, and the storage tank can be loaded with reactant water 23.The storage in the storage tank 39 takes place via the storage line 21 or a corresponding branch line (not shown in detail) on the output side of the cleaning device 11 (see also . Fig. 2). At the same time, a connection unit to a pipeline 51 for transporting hydrogen H2 as product gas from the electrolysis is attached to platform 3. This pipeline is connected to or supplied via a product gas line. The pipeline 51 leads from platform 3, submerges into the underwater area 31, and extends over the seabed 35 to the mainland. On the mainland, the product gas hydrogen H2 can be taken over and further processed. During normal operation of the electrolysis system 100, product gas—in this case hydrogen H2—can be fed into the pipeline 51 under pipeline pressure and transported to the mainland. The withdrawal of reactant water 23 from the storage tank 39 takes place via a withdrawal line 37, which is connected to the electrolysis system 5 and supplies the electrolyzer with the demineralized water H2O, which was obtained independently of seawater from rainwater or condensate.

[0064] In Fig. 4 shows a simplified representation of an offshore electrolysis system 100, the water collector 13 of which is designed as a rainwater collector 41 and is connected to the platform 3 via a water line 55. A rainwater collector 41 is - in the Fig. 4, shown to the left of platform 3, is designed as a floating basin 53 with a large circular collecting surface. Basin 53 is arranged floating on the water surface at sea level 25 and is anchored to the seabed 35 by cables, with a foundation 33 embedded in the seabed 35 for each cable. The rainwater collected in basin 53 can be pumped via a water pipe 55 into an intermediate storage tank 15 on platform 3 or into an intermediate storage tank 15 located elsewhere.

[0065] Furthermore, it is possible to arrange and permanently install a rainwater collector 41 on a specially designed supply platform 57 offshore. An intermediate storage tank 15 can then be mounted on the supply platform 57 or suspended below the supply platform, and possibly other functional elements or auxiliary systems for the water supply facility 7. This is exemplified in the Fig. 4 to the right of platform 3. Again, a water pipe 55 is connected to platform 3 so that the rainwater collected in the water collector 13 can be directed to a connection on platform 3, in particular for further treatment in a water treatment plant.

[0066] In another embodiment, Fig. 5 shows a simplified representation of the condensation device 43 designed as a fog collector. In contrast to the Fig. In the embodiment of a condensation device 43 with an electrically operated condensation dryer, which can be positioned locally in an operating room, discussed in Figure 3, the fog collector is spanned over a large area and permanently exposed to the maritime ambient air L outside. Due to the larger space requirement of the collector area compared to a condensation dryer, an installation of a plurality of fog collectors on a specially provided supply platform 57 is preferable, as in Fig. 5. In addition, in the Fig. 5 not shown in detail - a mist collector can also be mounted on a platform 3 carrying the container 9 with the electrolysis plant 5, in order to utilize the still available installation space for a condensation device 43 designed as a secondary collector to the greatest extent possible for obtaining condensate water from the ambient air L.

[0067] Each fog collector has a respective drainage line 59 in its lower region, so that the water droplets condensing from the flowing air L on the fog collector collect automatically in the drainage line 59 due to the gradient in the lower region. The drainage line 59 of each fog collector flows into a central collection line 61 for the collected condensate. The collection line 61 is connected to an intermediate storage tank 15, which is attached to the supply platform 57. A water line 55 leads from the intermediate storage tank 15 and leads to a cleaning device 11 (not shown in detail). The cleaning device 11 for the condensed water H2O can, for example, be housed in one of the containers 9 on the platform 3 supporting the electrolysis plant 5, or in one of the containers 9 that houses the equipment for the balance-of-plant 27 and other control devices (see also Fig. 1).

[0068] For use on supply platform 57, large-area fog collectors made of nylon or polypropylene nets with 0.1 mm fine threads and a mesh size of 1 mm can be used, which achieve average fog yields in maritime regions of 3-9 l / (m 2·d) and beyond. The most productive fog yield occurs in spring and summer. The technology is characterized by its ease of design, use, and maintenance, which keeps installation and maintenance costs to a minimum. Materials suitable for condensation in fog collectors are textiles with different mesh sizes and weave shapes, e.g., nub, pore, and honeycomb structures. With regard to the type of wetting by the fog droplets, a distinction can be made between water-repellent, i.e., hydrophobic with a large contact angle of the water droplet to the fabric (lotus effect), and water-attracting, i.e., hydrophilic with a high level of wetting and a small contact angle to the fabric.The physical process of water absorption and release is explained as follows: Small mist droplets adhere to the fabric and grow larger due to the constantly following mist droplets until they reach a size that causes the water droplets to flow away.

Claims

[1] Offshore electrolysis system (100) comprising a wind turbine (1) with a platform (3) and with an electrolysis plant (5) arranged on the platform (3), which is connected to the wind turbine (1) for supplying electrolysis current, and further comprising a water supply device (7) connected to the electrolysis plant (5), which has a water collector (13) which is designed in such a way that water with no or only very small amounts of salts can be obtained independently of seawater, which water can be used as reactant water for operating the electrolysis plant (5). [2] Offshore electrolysis system (100) according to claim 1, wherein the water supply device comprises an intermediate storage (15) which is provided on the platform (3) and / or is incorporated within the tower (19) of the wind turbine (1), wherein the intermediate storage (15) is connected to the water collector (13). [3] Offshore electrolysis system (100) according to claim 2, wherein a cleaning device (11) is provided which is connected to the intermediate storage (15) via a withdrawal line (17). [4] Offshore electrolysis system (100) according to claim 3, wherein the cleaning device (11) is connected to a storage tank (39) via a storage line (21), so that treated water can be supplied to the storage tank (39) as reactant water (23) and can be made available for the operation of the electrolysis plant (5). [5] Offshore electrolysis system (100) according to claim 4, wherein the storage tank (39) is connected to the electrolysis plant (5) via a feed line (37). [6] Offshore electrolysis system (100) according to one of the preceding claims, wherein the water collector (13) comprises a rainwater collector (41) arranged for rainwater collection. [7] Offshore electrolysis system (100) according to claim 6, wherein the rainwater collector (41) comprises a basin, the basin being mounted on a platform (3) and / or arranged floating on the sea. [8] Offshore electrolysis system (100) according to one of the preceding claims, wherein the water collector (13) comprises a condensation device (43) arranged for condensing moisture-saturated air. [9] Offshore electrolysis system according to claim 8, with a condensation device (43) having a mist collector comprising a fine-meshed, large-area net as a collector, in particular nylon or polypropylene nets. [10] Offshore electrolysis system (100) according to claim 8, wherein the condensation device (43) comprises a condensation dryer, wherein a condensation dryer is arranged within the tower (19) or the nacelle of the wind turbine (1). [11] Offshore electrolysis system (100) according to claim 9 or 10, wherein the electrolysis plant (5) comprises an electrolyzer arranged in a container (9) and a condensation device (43) so that condensation of moisture can be brought about in the container (9) and dry operating conditions are effected. [12] Offshore electrolysis system (100) in which an island network is implemented without connection to an electrical supply grid. [13] Offshore electrolysis system (100) according to one of the preceding claims, wherein the electrolysis plant (5) comprises an electrolyzer for water electrolysis based on a proton exchange membrane (PEM) electrolysis or on an alkaline electrolysis and with hydrogen (H2) as product gas. [14] Method for operating an offshore electrolysis system (100) according to one of the preceding claims, wherein water is extracted in a water collector (13) independently of seawater in a quality in which the extracted water contains no or only very small amounts of salts. [15] A method according to claim 14, wherein rainwater is collected and / or water is obtained from a condensation of moisture-saturated air. [16] Method according to claim 14 or 15, wherein the water obtained is treated and treated water is supplied as reactant water (23) to the electrolysis plant (5).

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