Offshore electrolysis system, and method for operating an offshore electrolysis system

Abstract

The invention relates to an offshore electrolysis system (100) comprising: a wind turbine (1) having a platform (3) and an electrolysis plant (5) which is arranged on the platform (3) and is connected to the wind turbine (1) in order to supply electrolysis current; and a water supply device (7) which is connected to the electrolysis plant (5) and has a water collector (13) which is designed such that it is possible, without relying on seawater, to obtain water with little or no salt content which can be used as feed water for operating the electrolysis plant (5). The invention also relates to a method for operating a corresponding offshore electrolysis system (100), wherein, without relying on seawater, water is obtained in a water collector (13), the obtained water being of a quality with little or no salt content.

Description

[0001] Description

[0002] Offshore electrolysis system and method for operating an offshore electrolysis system

[0003] The invention relates to an offshore electrolysis system and a method for operating an offshore electrolysis system.

[0004] An electrolysis plant is a device that uses electrical current to transform materials (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 has several electrolyzers, so that with appropriate scaling, high electrolysis capacities for electrochemical material conversion can be achieved.

[0005] Hydrogen is now produced from water using methods such as proton exchange membrane (PEM) electrolysis or alkaline electrolysis. The electrolysis plants 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).

[0006] Current considerations are to use surplus energy from renewable energy sources during periods of abundant sun and wind, i.e., with above-average solar or wind power generation, 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 energy gas. A renewable energy gas is a combustible gas that is obtained from renewable sources using electrical energy.

[0007] 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.

[0008] One source of renewable energy is wind power. Large electrical outputs can be achieved, particularly with offshore wind turbines located close to the coast. The challenge, however, is that the distance to the consumers is great. The energy should therefore be transported to the consumer with as little loss as possible. Hydrogen is an ideal 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 of particular interest to produce the hydrogen directly at the site of energy generation, i.e. to position offshore electrolysis plants directly at offshore wind turbines or in their immediate vicinity.For example, offshore electrolysis systems are currently being discussed, in which the electrolysis takes place directly on an offshore platform.

[0009] An electrolysis plant is installed next to a wind turbine. The wind turbine can be connected to the electrolysis plant to form a largely self-sufficient, i.e. almost grid-independent, electrolysis system and can be specially equipped for offshore island operation. In the best case, these electrolysis systems, comprising a combination of a wind turbine and an electrolysis plant, can also be installed entirely without any auxiliary connection to a power grid and can be equipped exclusively for island operation. This particularly applies to electrolysis systems installed far off the coast in order to avoid long connection routes to the public grid in the coastal region. The electrolysis plant with a number of electrolyzers is ideally placed in the immediate vicinity of the renewable energy sources, i.e. the wind turbine, in order to reduce or avoid both transformation and line losses.Offshore electrolysis systems are therefore currently being intensively developed, with electrolysis units installed directly on a platform with an offshore wind turbine. 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 planned maintenance, for example, at the wind turbine's turbine, no power is available from the generator or the power grid.

[0010] In offshore electrolysis systems, special attention must also be paid to preventing corrosion of the electrolysis plant, as the presence of salt water can lead to significantly higher corrosion rates, jeopardizing the long-term uninterrupted operation of an electrolysis plant. In principle, offshore electrolysis plants can be equipped with electrolyzers and housed within closed enclosures, called 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 in order 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 with maintaining a minimum temperature during extended periods of downtime. In the latter operating mode, sufficient freeze protection for the water-soaked electrolyzer cells must be ensured, particularly during periods of calm weather and when the wind turbine is shut down in the winter months. With regard to the 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, to avoid overheating and failure of the electrolyzer and, on the other hand, damaging corrosion caused by exposure to maritime 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.

[0011] To protect the electrolyzers from environmental influences, they require, as explained above, an enclosure such as a container. Water management is particularly challenging in an offshore electrolysis system based on the electrolysis of water. The temperature inside the container must therefore not fall below approximately 5°C. Otherwise, the water-bearing components, which contain water, can freeze and bring the entire system to a standstill. This would defeat the purpose of low-maintenance and self-sufficient operation of offshore electrolysis systems with wind turbines without grid connection.

[0012] 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 solution 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 in order to ensure continuous operation and a supply of reactant water of high quality and purity.

[0013] The object of the present invention is to provide an offshore electrolysis system designed for improved provision of reactant water, wherein the production efficiency in hydrogen generation is increased compared to known approaches. A further object is to provide a method for operating an offshore electrolysis system.

[0014] 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.

[0015] 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 has no or only very small amounts of salts.

[0016] The advantages and preferred embodiments of an offshore electrolysis system listed below can be analogously transferred to the method for operating the electrolysis system.

[0017] The offshore electrolysis system and its operating method significantly improve the energy consumption for water supply and water treatment using reactant water to operate 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, which is also low-maintenance. The water supply system is both low-maintenance and requires little intervention, as it is independent of seawater and requires virtually no recourse to seawater.

[0018] The invention is based on the fact that, in addition to electricity, water is also needed to split water in electrolysis. To produce around one kilogram of hydrogen, at least nine liters of water are needed. And consumption can increase considerably if the water has to be treated, i.e. desalinated or deionized. In all large-scale electrolysis processes such as REM or alkaline electrolysis, the water must meet certain purity requirements, as impurities or foreign ions which are continuously fed into the process water circuit 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 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 have been essential for large-scale commercial electrolysis plants and require high energy consumption. This energy requirement for providing 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.

[0019] The increasingly installed and planned, more powerful, grid-independent offshore wind turbines and their growing electrical generation capacity require correspondingly more powerful electrolysis systems and a correspondingly higher water consumption. It is expected that the performance class of offshore electrolysis systems and their number will increase significantly in the future.

[0020] The associated increasing demands for safe and environmentally friendly operation in a maritime environment must be taken into account. Due to the scaling efforts towards larger offshore electrolysis systems far off the coast, the question of the most self-sufficient, i.e. grid-independent, island operation with 100% hydrogen production from renewable wind power, as well as the environmental compatibility of such systems, is becoming the focus of discussion. On the one hand, from an environmental point of view, operation must be ensured with the least possible impact on the maritime ecosystem. A self-sufficient and at the same time low-intervention solution for a secure water supply for the electrolysis plant is therefore of crucial importance for the energy and ecological balance.

[0021] The concept of the invention ensures a water supply and replenishment, minimizing the need for recourse to seawater, as a water collector is provided independently, allowing salt-free water to be collected and extracted from natural sources independently of seawater. The treatment effort required is significantly reduced compared to seawater. Depending on the maritime location of the offshore electrolysis system, quantities of water are utilized and fed into the electrolysis process. The water collector of the water supply facility is designed to suit the required or harvestable quantity of water in terms of the collection quantity and effective collection area.

[0022] The offshore electrolysis system of the invention advantageously recognizes and overcomes for the first time the disadvantages of conventional water supply concepts in off-grid electrolysis systems, which - as described above - require very large amounts of energy and plant engineering for seawater desalination and seawater treatment. Seawater desalination is the production 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 by-products such as table salt are produced. The energy consumption for the multi-stage flash evaporation of seawater is 23-27 kWh / m 3 , approx. 90 MJ / m 3. With 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 considerably reduced. At most, the water supply facility can also have additional recourse to seawater 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. In a particularly preferred embodiment of the offshore electrolysis system, the water supply system has an intermediate storage tank, which is provided on the platform and / or installed within the tower of the wind turbine, with the intermediate storage tank being connected to the water collector.

[0023] If necessary, pumps can be provided here which convey the water collected in the water collector from the water collector into an intermediate storage tank and thus regularly empty 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. The intermediate storage tank can therefore be formed or incorporated quite simply as a cavity within the tower of the wind turbine itself. The intermediate storage tank is therefore preferably let 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.

[0024] Appropriate storage volumes for an intermediate storage facility can also be achieved using water tanks installed beneath the platform. These water tanks are thermally insulated, depending on the geographical location of the electrolysis system, 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 at the same time maintaining a sufficient quantity of water to cover at least several days' electrolysis demand. This means that even phases with a low yield of collected water in the water collector can be safely bridged.

[0025] 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.

[0026] This creates the possibility of preparing and purifying the water collected in the water collector and stored in the intermediate storage tank for use in the electrolysis system. Although the water originally collected in the water collector already has a 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 + , 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 CI", nitrate ions NO3" or sulfate ions SO4" may also be introduced or dissolved. Due to the already good purity of the collected water, contamination with these substances is low. Therefore, the cleaning facility can be designed and dimensioned much smaller than a comparable seawater treatment plant. The wind turbine also requires significantly less energy because the collected water already has a good degree of purification. Consequently, 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.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 connected 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 reactant water to be fed into and refilled 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 circuit with prepared reactant water. 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 from either 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 precipitation water collector configured for rainwater collection. In this way, precipitation water can be obtained, for example, from rainwater, which is collected via an appropriately dimensioned rainwater collector with a large collection area.

[0031] Preferably, the rainwater collector has a basin, wherein the basin is mounted on a platform and / or arranged floating on the sea.

[0032] The basin is a collection basin and can be located on a separate offshore platform, which is adjacent to the platform of the offshore electrolysis system and serves 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, 100-500m 3 be installed. The intermediate storage facility allows the rainwater collected in the catchment 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 m 2 to , 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 forecast water demands. 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 that, in a large offshore electrolysis system, several electrolysis plants arranged on a respective platform are supplied by a central water supply facility with a water collector.

[0033] In a particularly preferred embodiment of the offshore electrolysis system, the water collector has a condensation device that is designed for condensing moisture-saturated air. This creates the possibility, as an alternative or in addition to the rainwater collector, of obtaining water from the condensation of moist ambient air. The moisture condenses and can be collected as water. It is possible to obtain moisture and thus water from the ambient air of the offshore electrolysis system by condensation or even within the system components. Again, it is possible to integrate the condensation device on the platform supporting the electrolysis system or on a specially provided

[0034] An offshore platform will be constructed as a supply platform. The supply platform will then be part of the water supply system. In the condenser, moisture-saturated air is cooled, and when the temperature falls below the dew point, the gaseous water vapor is converted into droplets.

[0035] 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.

[0036] The term fog condensation also describes the extraction of water through the assisted condensation of water vapor using fog collectors. Research and experience in the use of fog collectors have significantly increased their effectiveness in water recovery, so that their use as water collectors in the water supply system of the offshore electrolysis plant is practical and advantageous. If, for example, cold ocean currents reach the sea surface off a coast, the air humidity transported by onshore winds condenses there because the temperature falls below the dew point and turns into water mist. The choice of materials used, the mesh sizes and fabric shapes (dimples, pores and honeycomb structures) 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.

[0037] 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 the nacelle of the wind turbine.

[0038] 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 means that the active components of the wind turbine, such as the electrical components in the nacelle or tower, are well protected 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 damage 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 that is often used in industrial and private areas, for example in tumble dryers or traditional construction dryers. For this purpose, moist air is passed over cooling fins / louvers by fans, the temperature of which is below the dew point of the air. 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 in this case is that it is set up locally and integrated into the water supply system. The condensation dryer is easily supplied with energy using electrical energy generated by the wind turbine.

[0039] In a particularly preferred embodiment of the offshore electrolysis system, the electrolysis plant has 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.

[0040] 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 operation of an electrolyzer, with the container being located on the platform. The condensation device within the container is adjusted such 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 in the storage tank for electrolysis purposes.

[0041] In a particularly preferred embodiment of the offshore electrolysis system, an island network is implemented without connection to an electrical supply network.

[0042] This design of the offshore electrolysis system achieves grid-independent operation, which is of particular economic interest. The hydrogen is produced in a water electrolysis process directly at the site of energy generation, meaning that offshore electrolysis systems are located directly next to offshore wind turbines or in their immediate vicinity. This means that the wind turbine is linked to the electrolysis system to form a self-sufficient, i.e., virtually grid-independent, electrolysis system and is specially equipped for offshore island operation. Battery units can be provided to bridge periods of low wind in order to maintain minimal operation of system-relevant functions of the electrolysis system.

[0043] In a further preferred embodiment of the offshore electrolysis system, the electrolysis plant has 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.

[0044] 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. High-purity water is also required for alkaline electrolysis 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.

[0045] This means that, if required, combinations of different electrolyzers for water electrolysis in the offshore electrolysis system are possible and can be adapted depending on the utilization concept. While alkaline electrolyzers can ideally be operated in a quasi-stationary mode at rated power, PEM electrolyzers are capable of partial load, especially at lower partial loads below 30% of the rated power. Hydrogen and oxygen are produced as product gases in both technologies. In addition to being transported away as intended via a pipeline and further used on land, some of the hydrogen is temporarily stored on the platform in local hydrogen storage facilities. A further aspect of the invention relates to a method for operating a corresponding offshore electrolysis system.

[0046] In this process, water is extracted from a water collector independent of seawater in a quality that contains no or only very small amounts of salt.

[0047] The process can advantageously be carried out autonomously, i.e. without substantial recourse to seawater and operation of a large seawater desalination plant, which is usually required to obtain reactant water.

[0048] In an advantageous embodiment of the method, rainwater is collected and / or water is obtained from a condensation of moisture-saturated air.

[0049] This provides a particularly efficient method for obtaining reactant water of sufficient quantity and quality. Rainwater accumulates regularly when installed in an offshore environment, depending on the forecast, at several hundred 1 / m 2and year. This amount of precipitation can be used advantageously. In addition to or as an alternative to rainwater use, 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.

[0050] For this purpose, the process is preferably carried out in which the water obtained is treated and the treated water is fed to the electrolysis plant as reactant water.

[0051] This allows for an on-demand and demand-based replenishment of treated reactant water. The current replenishment can be controlled so that, depending on the electrolysis output and the associated water consumption, a certain fill level is maintained in the electrolyzer, ensuring that the electrolysis cells are supplied with reactant water. A control and regulation system is provided for this purpose, along with appropriate feed pumps and control valves.

[0052] FIG 1 an offshore electrolysis system with an electrolysis plant and a wind turbine;

[0053] FIG 2 shows a schematic representation of elements of the process of seawater-independent water extraction based on functional elements of the water supply facility;

[0054] FIG 3 is a schematic side view of an offshore electrolysis system with water supply device;

[0055] FIG 4 an offshore electrolysis system with rainwater collector;

[0056] FIG 5 a condensation device equipped as a mist collector.

[0057] The same reference symbols have the same meaning in the figures.

[0058] FIG. 1 shows an offshore electrolysis system 100. The offshore electrolysis system 100 comprises an electrolysis plant 5 and a wind turbine 1, which has a tower 19 and a turbine rotor, as shown in the upper right part of FIG. 1. In the lower area of ​​the tower 19, a platform 3 is attached above sea level 25 (see FIG. 4 and FIG. 5), which is specially designed and configured to accommodate various plant components for the intended operation of the offshore electrolysis system 100. These plant components are shown in an enlarged illustration in the lower part of FIG. 1:

[0059] An electrolysis plant 5 is set up 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 set up on platform 3, in which electrolysis elements (not shown in detail) such as individual electrolyzers are accommodated, so that particularly sensitive functional components of the electrolysis plant 5 are protected from the effects of the weather. Some of the containers 9 set up on platform 3 comprise control devices 27 or so-called "balance-of-plant" elements and accommodate them protectively. 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 provided specifically for this purpose.Other components or parts of the system accommodated in the containers 9 may also be 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.

[0060] 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 absorbed 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 grid-independent island operation and equipped for self-sufficient use in regions farther from the coast. The wind turbine 1 is therefore an offshore wind turbine.

[0061] The strategy of providing the electrolysis plant 5 using 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. For the operation of the offshore electrolysis system 100 with water electrolysis, fully demineralized water, so-called deionized water, is required in sufficient quantities and with a high degree of purity, which must be permanently replenished into the process water circuit of the electrolysis plant 5 due to consumption. In such an offshore electrolysis plant 100, only salty seawater is usually available. In order to be able to use the water taken from the sea, the seawater must, however, be desalinated. A selection of desalination processes is available for this purpose, such as, for example,Reverse osmosis or vacuum distillation are available, but all of these require significant amounts of electrical energy. The use of electrical energy for desalination significantly reduces the efficiency of the overall system and should therefore be kept to a minimum.

[0062] This disadvantage is counteracted by the invention with a water supply device 7, which is advantageously integrated into the electrolysis system 100 or connected to it. It is thus possible - as only schematically indicated in FIG. 1 - for the water supply device 7 to be accommodated at least partially in a selected container 9 of the offshore electrolysis system 100 or for a container 9 to have 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 designed in such a way that high-quality water can be supplied to the electrolysis system 5 by means of the water supply device 7, independently of seawater use, so that continuous electrolysis operation is nevertheless achieved.In this case, use is made of precipitation water, in particular rainwater, and alternatively or additionally of condensation water extraction. This water is collected or extracted and treated at the installation site of the offshore electrolysis system 100 or in its immediate vicinity. The process of seawater-independent water extraction and the functional elements of the water supply device 7 are explained below by way of example in a flow diagram with reference to FIG 2. The water supply device 7 has a water collector 13 which is appropriately equipped for the collection of precipitation water or condensation water from the air L. The water collector 13 is designed as a precipitation water collector 41 or as a condensation device 43, although combinations of these designs are also possible.The water collector 13 is followed by an adequately dimensioned intermediate storage tank 15 into which collected water H20 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 H20 can be conveyed into the intermediate storage tank 15. If the installation of the water collector 13 permits this due to a set height difference, water H20 can also be automatically introduced from the water collector 13 into the intermediate storage tank 15. A cleaning device 11 is arranged downstream of the intermediate storage tank 15 via an extraction line 17.The cleaning device 11 has 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 and residual salts can be removed. Due to the already good quality and purity of the water H2O collected as a result of precipitation or condensation, the desalination devices are significantly smaller than with seawater desalination. The desalination effort is considerably lower than with seawater desalination and the system effort for installation as well as the energy requirement for operating the cleaning device 11 is correspondingly reduced. This saving is immediately available as electrical power for electrolysis purposes. The cleaning device 39 is connected to a storage tank 39 via a storage line 21.Fully demineralized water (H2O), also known as 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 a diaphragm separates the anode chamber 47 from the cathode chamber 49. The reactant water 23 can thus be split electrochemically, so that oxygen O2 is formed on the anode side and hydrogen H2 is formed on the cathode side. The hydrogen H2 is the interesting product gas from the electrolysis. It is compressed, temporarily stored if necessary and brought ashore via pipelines or transport ships.

[0063] FIG 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 fastened 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, reference is made to FIG 2.The water supply device 7 has an intermediate storage tank 15 so that water H2O obtained from precipitation or condensation in the water collector 13 (see FIG. 2) 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 storage containers 39 specially provided and designed for this purpose 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.

[0064] 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 with 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 introduced 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 outlet 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 the platform 3, which is connected to a product gas line or supplied via it. The pipeline 51 leads away from the platform 3, immerses in the underwater area 31 and is led 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 thus 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 plant 5 and supplies the electrolyzer with the fully demineralized water H2O which was obtained from rainwater or from condensate water independently of seawater.

[0065] 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 pipe 55. A rainwater collector 41 is designed - shown to the left of the platform 3 in FIG 4 - as a floating basin 53 with a large circular collecting surface. Basin 53 is arranged floating on the water surface at the height of sea level 25 and is firmly anchored to the seabed 35 via cables, with a foundation 33 being introduced into the seabed 35 for each cable. The rainwater collected in the basin 53 can be pumped via a water pipe 55 into an intermediate storage tank 15 on the platform 3 or into an intermediate storage tank 15 arranged elsewhere.

[0066] 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 attached to the supply platform 57 or suspended below the supply platform, and if necessary, further functional elements or auxiliary systems for the water supply facility 7. This is shown by way of example in FIG. 4 to the right of platform 3. Again, a water pipe 55 is led 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.

[0067] In a further exemplary embodiment, FIG. 5 shows a simplified representation of a condensation device 43 designed as a fog collector. In contrast to the embodiment of a condensation device 43 discussed in FIG. 3 with an electrically operated condensation dryer that can be positioned locally in an operational space, 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, it is preferable to set up a plurality of fog collectors on a specially provided supply platform 57, as shown in FIG. 5.In addition - not shown in detail in FIG 5 - 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 available 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.

[0068] Each fog collector has a 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 opens 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 out of the intermediate storage tank 15 and opens into a cleaning device 11 (not shown in detail). The cleaning device 11 for the condensed water H20 can, for example, be accommodated in one of the containers 9 on the platform 3 supporting the electrolysis plant 5 or in one of the containers 9 which houses the devices for the balance-of-plant 27 and other control devices (see also FIG 1).

[0069] 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, which achieve average fog yields in maritime regions of 3-9 1 / (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 humidification 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

Patent claims 1. Offshore electrolysis system (100) comprising a wind turbine (1) with a platform (3) and with an electrolysis system (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 system (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 system (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 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 system (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) configured for rainwater collection.

7. Offshore electrolysis system (100) according to claim 6, wherein the rainwater collector (41) comprises a basin, wherein the basin is 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) has a condensation device (43) which is 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 a container (9) arranged electrolyzer and a condensation device (43) so that condensation of moisture can be brought about in the container (9) and dry operating conditions are achieved.

12. Offshore electrolysis system (100) in which an island network is implemented without connection to an electrical supply network.

13. Offshore electrolysis system (100) according to one of the preceding claims, wherein the electrolysis plant (5) comprises a Electrolyzer for water electrolysis based on proton exchange membrane (PEM) electrolysis or alkaline electrolysis using hydrogen (H2) as product gas.

14. Procedure for operating an offshore electrolysis system (100) according to one of the preceding claims, wherein water is obtained in a water collector (13) independently of seawater in a quality in which the water obtained contains no or only very small amounts of salts.

15. The method according to claim 14, wherein rainwater is collected and / or water is obtained from a condensation of moisture-saturated air.

16. The 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).

Images