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) with a tower (19) anchored on the seabed and with an electrolysis system (5), wherein the electrolysis system (5) is connected to the wind turbine (1) by a supply line (11), and wherein the electrolysis system (5) has an electrolyzer (13) arranged in a container (9), wherein the container (9) is arranged below sea level (25). The invention further relates to a method for operating a corresponding offshore electrolysis system. In this method, an electrolyzer (13) of the electrolysis plant (5) arranged below sea level (25) decomposes water into hydrogen (H2) and oxygen, with the hydrogen (H2) produced being transported away via a product gas line (7).

Description

The invention relates to an offshore electrolysis system and to a method for operating an offshore electrolysis system.An electrolysis plant is a device which brings about a material conversion (electrolysis) with the aid of electric current. According to the variety of different electrochemical electrolysis processes, there are also a plurality of electrolysis systems, such as an electrolysis system for water electrolysis. For the direct current power supply with electrolysis current, electrolysis systems are connected to energy generation systems, so that an electrolysis system is formed in the combination. An electrolysis plant typically has a number of electrolysers, so that, with corresponding scaling, large electrolysis powers for the electrochemical conversion can be achieved.Hydrogen is nowadays produced from water, for example, by means of proton exchange membrane (PEM) electrolysis or alkaline electrolysis. The electrolysis systems produce hydrogen and oxygen from the supplied water with the aid of electrical energy. This process takes place in an electrolysis stack composed of a plurality of electrolysis cells. Water is introduced as reactant into the electrolysis stack under DC voltage, two fluid streams consisting of water and gas bubbles (O 2 or. H 2) are discharged.Current considerations are directed to producing valuable materials with excess energy from renewable energy sources in times with a large sun and a large wind, i.e. with above-average solar power or wind power generation. A valuable substance can in particular be hydrogen which is produced by water electrolysis systems. By means of hydrogen, it is possible, for example, to produce so-called EA gas. An EE gas is a combustible gas that is obtained from renewable sources with the aid of electrical energy.Hydrogen represents a particularly environmentally friendly and lasting energy carrier. It has the unique potential to realize energy systems, traffic and large parts of chemistry without CO 2- emissions. In order for this to be possible, however, the hydrogen must not be derived from fossil sources, but must be produced with the aid of renewable energy.One source of renewable energies is wind power. In particular, with shore-based, so-called offshore wind turbines, large electrical powers can be realized. However, it is a challenge that a large distance from the consumers must be overcome. The energy should therefore be transported as free of losses as possible to the load. Hydrogen is very suitable as transport medium. This can be transported, for example, by pipelines in gaseous form. A positive secondary aspect here is that a hydrogen-carrying pipeline can simultaneously fulfil the function of an energy store, since the internal pressure can be varied within certain limits. From this consideration, it is of particular interest to produce the hydrogen directly at the site of energy generation, i.e. to place offshore electrolysis plants directly on offshore wind turbines or in the immediate vicinity thereof. Thus, currently, for example, offshore electrolysis systems are discussed in which an electrolysis plant is set up directly on a platform of an offshore wind power plant. In this case, the wind power plant can be connected to the electrolysis plant to form a substantially autonomous, i.e. virtually grid-independent electrolysis system and can be equipped specifically for offshore island operation.In the best case, these electrolysis systems comprising a combination of a wind power plant and an electrolysis plant can also be constructed completely without auxiliary coupling to a power grid for supply and can be enabled exclusively for island operation. This concerns electrolysis systems which are constructed above all far outside the coast in order to avoid long connection paths to the public network of the coastal region. The electrolysis plant with a number of electrolysers is ideally placed directly in the vicinity of the renewable energy sources, i.e. the wind turbine, in order to reduce or avoid both transformation and conduction losses. Therefore, offshore electrolysis systems with electrolysis systems are currently being developed with great intensity, which are set up directly on a large supply platform with an offshore wind turbine. In the case of such a coupling, regardless of whether "onshore" or "offshore", this installation can also be operated without connection to the power grid. Without a grid coupling, however, during a wind stall, flause or planned revision, e.g. at the turbine of the wind turbine, neither current is available through the generator nor through the power grid.If, on the other hand, no renewable current is simultaneously available in the case of very cold weathering, for example because no wind is blowing or, for example, when the wind turbine is at a required plant shutdown for possibly unpredictable maintenance purposes, the thermal energy must be provided in another and reliable manner for a necessary temperature maintenance of the electrolysis plant. Otherwise, irreversible damage to the electrolysis cells is imminent as a result of frost damage and even a total loss of the electrolyzers installed in the electrolysis plant. The water-conducting lines between the containers or enclosures must likewise be correspondingly kept at a minimum temperature so that they do not risk freezing. This also requires energy which must be made available from other sources in the case of air vents.It is therefore the object of the present invention to specify an offshore electrolysis system which, compared to the known concepts, enables reliable operation at reduced cost of production, wherein said system is at the same time designed for operation which is as autonomous as possible and low-maintenance. A further object is to specify a method for operating an offshore electrolysis system.The object directed at an offshore electrolysis system is achieved according to the invention by an offshore electrolysis system comprising a wind turbine having a tower anchored on the seabed and having an electrolysis plant, wherein the electrolysis plant is connected to the wind turbine by a supply line, and wherein the electrolysis plant has an electrolyser arranged in a container, wherein the container is arranged below sea level.The invention is already based on the finding that energy sources that are primarily renewable in the future, such as wind and solar energy, are to be used in order to reduce the CO 2- output. In addition to being used as an electrical energy source, the renewable energy is likewise intended to serve as a raw material for the production of chemical basic materials or fuels such as, for example, hydrogen. The electrolysis systems with the electrolysers are ideally placed in the vicinity of the renewable energy sources in order to be able to reduce or avoid transformation and conduction losses. In offshore electrolysis systems, sufficient space and installation space must basically be created or found for this purpose in conventional concepts, which may cause considerable additional costs due to the design of the platform of the wind turbine.In the course of first planning of the decentralized, direct couplings of electrolysis plants to offshore wind power installations, designs have been proposed up to now which have been mounted directly on a platform as a supporting structure on the tower of the offshore wind power installation. The invention has now recognized that this type of platform-based construction and installation of an offshore electrolysis system causes additional static costs for the wind turbine during operation and considerable costs for the installation and installation of this necessary platform.The invention proposes, in an offshore electrolysis system for the electrolysis plant, underwater installation of the electrolyser. This makes it possible to dispense with a complex construction of a large operating and supply platform on the tower of the wind turbine with the numerous system components erected thereon. If at all, only a small supply platform is required for selected auxiliary systems, for example for controlling the installation and supplying power to the electrolysis installation or a device for treating seawater for supplying educt water for underwater electrolysis. However, even these auxiliary systems can be installed below sea level in one or more containers, so that a nearly autonomous "sub-sea" installation of the electrolysis plant is possible, which is connected to the wind turbine via a supply line. The electrolyser is accommodated and protected in a container.The invention thus provides an alternative solution to a platform which has previously been customary in the prior art for the installation of electrolysis installations on an offshore wind turbine, wherein the electrolysers in the container are preferably arranged underwater in the vicinity of the wind turbine. This advantageously additionally results in a secure cryoprotective effect on account of the arrangement of the electrolyser at a frost-free depth below the sea level. The risk of freezing of water-conducting components of the electrolysis plant, in particular of the sensitive electrolysis cells of the electrolyser, is thereby counteracted intrinsically. In particular, no active temperature maintenance systems should be provided in the event of a risk of frost. It is conceivable to install the electrolysis units both directly on the seabed and at any desired but fixed water depth. This design has the advantage that the tower of the wind turbine is not subjected to any additional static load and the costs for the platform are omitted. In addition, starting from a certain water depth, there is no longer the risk of icing of the water-based media necessary for electrolysis and the potentially resulting plant damage. This eliminates expensive heating devices, including their energy supply and thus also plant costs. The same also applies to the cooling systems required for electrolysis operation, which can be made much smaller and more cost-effective, since lower temperatures constantly prevail in deeper water layers and the required size of cooling systems generally behaves inversely proportional to the available cooling temperature difference.In a particularly preferred embodiment of the offshore electrolysis system, the container has an underwater-suitable encapsulation which is configured for use of the electrolyser below sea level.The underwater-compatible capsule is advantageously designed as a plunger capsule or as a casing in a watertight and pressure-resistant manner. In this case, in a possible advantageous embodiment, the underwater-suitable encapsulation can be designed as a pressure-compensated housing which is filled with a liquid which has an internal pressure which is compensated for by the pressure of the medium which surrounds the underwater housing, such as, for example, seawater. The electrolyser is arranged within the enclosure. The pressure equalization can be effected by a pressure equalization which can be attached to the underwater envelope or be part thereof. In other embodiments, the underwater housing can also be a pressure-resistant housing which maintains a pressure below typically 3-5 bar in the interior, for example between approximately 1.5 bar or approximately 2.5 bar. The fluid for pressure compensation can be a chemically inert and as incompressible as possible hydraulic fluid. It is also conceivable that the fluid for pressure compensation is seawater or demineralized water, e.g. appropriately prepared educt water for electrolysis.It has proven to be very particularly advantageous for underwater installation that underwater-operated pressure electrolysers can be designed more easily and thus more cost-effectively. The hydrostatic pressure prevailing at the water depth below sea level can be used particularly efficiently as a counterforce to the operating pressure of an electrolysis system with a pressure electrolyser. As a result, the container wall thicknesses and bracing devices usually required for an electrolyser designed as a pressure electrolyser under water can be designed to be significantly thinner, lighter and thus more cost-effective.The novel approach presented herein advantageously integrates renewable energy generation, electrolysis, and storage at an offshore location with the unique aspect of subsea hydrogen generation and storage, thereby avoiding compression losses. The change in ambient water pressure affects the cell voltage of the electrolysis itself, which leads to a future compromise between compression requirements and electrolysis losses. The new concept has a number of advantages over the current approaches. By conducting electrolysis under water, ambient pressure under water is used to generate high pressure hydrogen, thereby greatly reducing the need for energy intensive compression systems. This is directly reflected in reduced operating costs because of the energy savings. Subsea production allows for example direct storage of hydrogen in high pressure tanks, thereby reducing the need for additional compaction and further improving energy efficiency. The high pressure hydrogen produced may be transported directly to the land using specially adapted ships or fed into an underwater pipeline, which offers flexibility and potential cost savings compared to the conventional method of compressing and transporting hydrogen.In a preferred embodiment of the offshore electrolysis system, the wind power plant has a generator which is accommodated within the nacelle of the wind power plant, wherein the supply line leads down within the tower and leads out of the tower under sea level and is connected to the electrolysis plant.In this way, an electrical supply of the electrolyser with electrical current is possible, wherein the supply line is laid within the tower in a protected manner and is well protected. Rectification of the alternating current initially generated in the generator can be achieved by a corresponding rectifier arrangement which is preferably arranged within the nacelle and is connected downstream of the generator. Furthermore, control and regulating devices for the electrolysis plant can also be accommodated in the nacelle. The supply line itself can be set up for a plurality of purposes and can also assume further supply tasks in addition to the electrical supply of the electrolysis system with current. Thus, the supply line can integrate, for example, lines for the state measurement and / or the control or regulation of the electrolyser, that is to say for example sensor lines and control lines. It is also conceivable for the supply line to comprise a fluid line, wherein the fluid is a hydraulic fluid, e.g. water or seawater, for pressure compensation of the encapsulation or else prepared educt water, demineralized water, for the operation of the electrolyser.In a further preferred embodiment of the offshore electrolysis system, the container is positioned at a depth below sea level and can be flooded with a liquid, so that a predetermined fluid pressure can be set in the container, which acts on the electrolyser.The liquid may be a hydraulic liquid, in particular water or seawater. The underwater-suitable encapsulation can thus also be designed as a plunger capsule and can securely accommodate the electrolyser and optionally further plant components of the electrolysis plant. Thus, a submergible electrolysis system can advantageously be provided which, depending on the selected immersion depth below the sea level, can be operated at a predeterminable hydrostatic pressure level of the water pressure of the environment. A displacement device for the fluid can be provided as required, which can be activated, for example, by an oxygen pressure tank.In a preferred embodiment, depending on the design, an electrolyser, a gas separator, a gas container, the control and process technology of the electrolyser and also devices for desalting and purifying the salt water to reactant water for electrolysis can be arranged optionally within a pressure-compensated housing. In this way, a virtually autonomous underwater installation of an electrolysis system in the offshore electrolysis system is achieved.By the underwater installation of the electrolyser, the offshore electrolysis system is particularly preferably suitable for the integration and operation of a pressure electrolyser in the container.Therefore, the electrolyser is preferably designed as a pressure electrolyser in the offshore electrolysis system and is designed for operation at a working pressure of greater than 5 bar, in particular of greater than 10 bar.Due to the ambient pressure in the container that can be hydrostatically adjusted as a result of the immersion depth below sea level, a counter pressure is provided, so that the material use and the wall thicknesses of a pressure electrolyser can be made significantly smaller than the ambient pressure compared to an use at atmospheric pressure. The same applies to the dimensioning of the bracing devices for the axially stacked cells braced in a pressure- and fluid-tight manner. Thus, the material input and the material stress of the fluid-conducting components of the pressure electrolyser are reduced by the ambient pressure. At the same time, reduced manufacturing costs are to be obtained. The selection of the operating pressure of the pressure electrolyser is adaptable to the depth of use below sea level and vice versa.Thus, in a preferred embodiment, the offshore electrolysis system can be designed in such a way that the container is arranged directly on the seabed. For this purpose, the container with the electrolyser can be set up on the sea bed and, if required, can be additionally anchored.In a particularly preferred embodiment of the offshore electrolysis system, the container is set up on a detachable supporting device at a height above the seabed.This realizes a mounting of the container at a working height. The support device can be firmly connected to the seabed via a foundation in the seabed and can have a detachable fastening device with respect to the container. As a result, the container with the electrolyser at its installation location is accessible for maintenance, inspection and service. On the other hand, the detachable mounting of the container realizes a replacement possibility of the container. For maintenance, revision or repair, the container may be recovered and lifted above the sea surface with a hoist. It is also possible here for the container to be flooded with a gaseous medium, for example oxygen or hydrogen, from a tank, the water being displaced. The container rises to the sea surface, similar to a submarine. In this way, heavy hoists and large cable winch on a service ship can also be dispensed with. The gaseous medium is advantageously product gas obtained from the electrolysis process, i.e. hydrogen or oxygen which is stored in gas reservoirs for flooding.In a preferred embodiment of the offshore electrolysis system, a coupling device is attached to the outer casing of the container, which coupling device is configured for the engagement of a hoist.This ensures that the container with the electrolyser can be fetched to the surface and brought to the deck of a service ship for revision or maintenance of the electrolyser. It is advantageously provided that a plurality of underwater-suitable containers are provided in the offshore electrolysis system, which containers perform different specific tasks. Thus, auxiliary systems, electrical supply devices, preparation device for the educt water, sensor devices and control and regulating devices for the electrolyser can be accommodated in a respective container for functional separation and in order to keep available corresponding container volumes. Certain functional elements can also be accommodated jointly in a container.Preferably, in the offshore electrolysis system, the electrolysis plant has a product gas line which is led out of the container, wherein hydrogen which is produced under a gas pressure can be transported as product gas by means of the product gas line.The gas pressure of the product gas corresponds approximately to the water pressure at the site of installation at the selected depth of the sea. The working pressure of the pressure electrolyser can, however, in particular also be selected to be somewhat higher than the prevailing water pressure. Thus, a pressure electrolysis can be carried out, wherein the product gas, in particular hydrogen and a high pressure which is already significantly increased compared to atmospheric pressure, can be generated. This pressure level of the product gas makes transport via a product gas line and further processing, for example compression, possible with less energy input.In a particularly advantageous embodiment of the offshore electrolysis system, the electrolyser is designed as a PEM electrolyser.The PEM electrolyser uses demineralized water as reactant, which can easily be obtained in the maritime environment. The recovery and provision can be effected by a container-based water treatment unit, which underwater is arranged in the vicinity of the electrolysis container or can be accommodated in the container with the electrolyser. Therefore, the configuration of the electrolyser as a PEM electrolyser is particularly advantageous and expedient. In principle, it is also possible for the water treatment unit to be set up within the tower of the wind turbine or on a small working platform on the tower.The object directed to a method is achieved according to the invention by a method for operating an offshore electrolysis system described above, in which water is supplied to the electrolysis plant at an electrolyser arranged below the sea scale and decomposed into hydrogen and oxygen, wherein the hydrogen (H 2) produced is transported away via a product gas line.Preferably, in the method, pressure electrolysis is carried out at a working pressure in the electrolyser, the working pressure being adapted to the hydrostatic pressure at the site of use below sea level.In this way, small differential pressures can be set between the working pressure in the electrolyser and the water pressure present at the housing, so that the material load on the housing construction is reduced. Consequently, the wall thicknesses of the housing construction can be dimensioned to be smaller than conventional pressure electrolysers-during operation in the atmospheric environment. The differential pressure is typically adapted and adjusted to less than 1 bar, in particular less than 0.5 bar, by the selection of the working pressure of the electrolyser and the adjustment of the water pressure via the immersion depth.Configurations, features and / or advantages which relate in the present case to the offshore electrolysis system relate analogously to the operating method, and vice versa. Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Here, diagrammatically and greatly simplified show: FIG. 1 shows an offshore electrolysis system with an electrolysis plant and with a wind turbine according to the prior art; FIG. 2 shows a schematic side view of an offshore electrolysis system with an electrolyser arranged in a container; FIG. 3 shows a schematic side view of an offshore electrolysis system with a mounting of the container; FIG. 4 shows a schematic side view of the offshore electrolysis system in a maintenance situation.Identical reference numerals have the same meaning in the figures.FIG. 1 shows an offshore electrolysis system 100 as is known from the prior art. Offshore electrolysis system 100 comprises an electrolysis plant 5 and a wind turbine 1 having a tower 19, as depicted in the upper right part of FIG. 1. In the lower region of the tower 19, a large-format platform 3 above the sea level 25 (see FIG. 2 ) is fastened to the tower, which platform is designed and designed specifically to accommodate various plant parts for the intended operation of the offshore electrolysis system 100. These necessary plant parts are shown in an enlarged illustration in the lower part of FIG. 1 by way of example:An electrolysis plant 5 is set up on the platform 3 and connected systemically to the wind turbine 1 to form the offshore electrolysis system 100. For this purpose, containers 9 are placed in particular on the platform 3, in which electrolysis elements, such as individual electrolyzers, are accommodated-not shown in more detail-so that a protection of particularly sensitive functional components of the electrolysis system 5 from weather influences is achieved. Individual ones of the containers 9 set up on the platform 3 comprise control devices 27 or so-called "balance-of-plant" elements and receive these protectively. These are selected containers 9, which are usually reserved solely for the accommodation and operation of these control devices 27 and, if appropriate, further auxiliary systems of the electrolysis plant 5. On the other hand, the electrolysers for electrochemical conversion are arranged in containers 9 provided separately for this purpose. Further components or plant parts accommodated in the containers 9 can also relate to storage containers for the educt water of the electrolysers, or the like.The wind power plant 1 preferably does not have a grid connection or grid coupling in the present case, but instead supplies the described electrolysis plant 5 with the wind energy absorbed directly in the autonomous offshore electrolysis system 100, which electrolysis plant is configured to produce preferably green hydrogen from the water electrolysis. The offshore electrolysis system 100 is therefore configured for grid-independent island operation and is equipped for autonomous use in regions farther away from the shore. The wind turbine 1 is therefore an offshore wind turbine.The strategy of providing the electrolysis system 5 via a number of containers 9, preferably ISO containers, advantageously ensures a simple maintenance and repair process and simultaneously protects the system parts from climate and weather influences and from corrosion and defective mechanical influences during operation. The electrolysis system 100 is particularly endangered in situations in which the wind power installation does not produce any current for the electrolysis under frost conditions, so that there is thereby the acute risk of freezing water-conducting systems of the electrolysis system 5, in particular in the case of a longer-lasting darkflogue with an associated risk of frost in a standstill operation.In addition to the exposure to weather and the risk of freezing, the known offshore electrolysis systems 100 have the disadvantage that the platform construction having a heavy platform 3 of large format and the manifold plant parts arranged thereon is associated with a considerable static load on the wind turbine 1. This involves considerable costs for the construction and operation of the offshore electrolysis system 100 in the known embodiment.These disadvantages are countered by the invention with a novel plant concept for an offshore electrolysis system 100, wherein particularly reliable operation is achieved with reduced production costs. FIG. 2 shows, by way of example, a schematic side view of a correspondingly equipped offshore electrolysis system 100 having a container 9 arranged below sea level 25. The anchoring takes place via a massive foundation 33 which is introduced into the sea floor. The tower 19 carries as a structural element a nacelle 17 with the turbine and extends from an surface area 29 into a surface area 31 into the seabed 21 Furthermore, an electrolysis plant 5 is provided which comprises an electrolyser 13, wherein the electrolysis plant 5 is connected to the wind turbine 1 via a supply line 11.A generator, not shown in detail, is arranged in the nacelle 17, so that current generated in the generator from the wind turbine 1 can be supplied as electrolysis current to the electrolyser 13 via the supply line 11. The supply line 11 is laid in the surface area 29 within the tower 19 and is led out of the tower 19 into the surface area 31 at the foot of the tower 19 and into a container 9. The electrolyser 13 is arranged in the container 9, which has an encapsulation suitable for underwater purposes for accommodating the electrolyser 13. The container 9 is arranged below the sea level 25 at a depth h, in the present case positioned on the sea bed 21 and set up for electrolysis operation in the marine area under water. An arrangement is realized in this case in which the container 9 can be flooded with a liquid, for example with seawater or with a hydraulic liquid from a storage tank, so that a predefined fluid pressure p can be set in the container 9, which is present and acts on the housing parts of the electrolyser 13. As a result, the electrolyser 13 can be designed in a particularly advantageous manner as a pressure electrolyser and can be operated at an operating pressure of, for example, greater than 5 bar. By means of the underwater installation, hydrogen H 2 is obtained in a particularly advantageous manner as product gas by electrochemical separation of water at a correspondingly high working pressure p. The pressurized hydrogen H 2 is led out of the container 9 via a product gas line 7, transported away and supplied for further use. It is possible here for hydrogen H 2 and / or oxygen to be stored partially in a respective tank under water and to be stored on the electrolysis plant 5.FIG. 3 shows a possible variant or further development of the positioning and anchoring of the container 5 to the electrolyser 13. In this case, a schematic side view of an offshore electrolysis system 100 of a mounting of the container 9 is shown. The container 9 is erected by a detachable support device 23, which holds the container 9 in position at a height above the seabed 21. The support device 23 is anchored into the seabed via a foundation 33. By means of the support device 23, the container 9 with the underwater-suitable encapsulation 15 comprising the electrolyser 13 is spaced apart from the seabed 21, so that as required accessibility and all-surrounding flushing of the container is effected. This is advantageous for uniform temperature maintenance of the surrounding walls of the container 9 and thermal management. Freezing at depth h below sea level is not to be feared, so that special temperature maintenance concepts for the water-conducting components of the electrolyser 13 are not necessary in the case of a longer darkfloft of the wind turbine in cold winter months. In a special embodiment, the underwater-suitable encapsulation 15 can be designed as a pressure-compensated housing which is filled with a liquid having an internal pressure which is compensated for by the pressure of the medium, such as seawater, surrounding the underwater housing. The electrolyser 13 is arranged within the enclosure 15.FIG. 4 shows a schematic side view of the offshore electrolysis system 100 in a maintenance situation or in the case of a necessary revision or inspection of the electrolyser 13. On the outer shell of the container 9 is attached a coupling device 35 which is designed for an intimate engagement of a hoist 39. The revision uses a corresponding service ship 37 which has a hoist 23 and lifts the container 9 with the electrolyser 13 out of the sea water. The hoist 23 is configured to engage the clutch device 25. In this way, in a maintenance situation, a container 9 with an electrolyser 13 to be maintained can be removed and easily exchanged for a fully functional electrolyser 13 in a further container 9. Due to the quick exchangeability and the modular concept, a maintenance-related production loss of hydrogen H 2 is reduced.The great advantage of the solution presented here is that the complicated and expensive installation of a platform 3 for placing a decentral electrolysis system 5 can be dispensed with. Furthermore, the underwater installation results in a considerable saving potential with regard to the plant construction costs or the necessary, pressure-stable design of individual components up to the thermal management system of the electrolysis plant. The constant underwater temperature eliminates the need for additional adiabatic air cooling, which would otherwise be required for electrolysis systems 5. This results in further energy savings and simplifies the system by reducing it to a cold water heat exchanger circuit. Moreover, this approach suggests the use of existing offshore structures, whereby capital investment for offshore electrolysis and storage facilities construction could be substantially reduced. The elimination of the compression stage in a pressure electrolysis will significantly reduce the maintenance effort of the system.

Claims

Offshore electrolysis system (100) comprising a wind turbine (1) with a tower (19) anchored on the seabed (21) and with an electrolysis plant (5), wherein the electrolysis plant (5) is connected to the wind turbine (1) by a supply line (11), and wherein the electrolysis plant (5) has an electrolyser (13) arranged in a container (9), wherein the container (9) is arranged below the sea level (25).Offshore electrolysis system (100) according to claim 1, wherein the container (9) has an underwater-suitable encapsulation (15), which is configured for use of the electrolyser (13) below the sea level (25).Offshore electrolysis system (100) according to claim 1 or 2, wherein the wind turbine (1) comprises a generator accommodated within the nacelle (1) of the wind turbine (1), wherein the supply line (11) is led down within the tower (19) and led out of the tower under the sea level (25) and connected to the electrolysis plant (5).Offshore electrolysis system (100) according to claim 1, 2 or 3, wherein the container (9) is positioned at a depth (h) below the sea level (25) and is floodable with a liquid, such that a predetermined fluid pressure (p) can be set in the container (9), which acts on the electrolyser (13).Offshore electrolysis system (100) according to one of the preceding claims, in which the electrolyser (13) is designed as a pressure electrolyser and is designed to a working pressure of greater than 5 bar, in particular can be operated at a working pressure of greater than 10 bar.Offshore electrolysis system (100) according to one of the preceding claims, in which the container (9) is arranged on the sea bed (21).Offshore electrolysis system (100) according to one of the preceding claims, in which the container (9) is set up on a detachable supporting device (23) at a height above the sea bed (21).Offshore electrolysis system (100) according to one of the preceding claims, wherein a coupling device (35) is attached to the outer shell of the container (9), which coupling device is configured for the engagement of a hoist (37).Offshore electrolysis system (100) according to one of the preceding claims, in which the electrolysis plant (5) has a product gas line (37) which is led out of the container (9) and by means of which hydrogen (H 2) generated under a gas pressure (p) can be transported as product gas.Offshore electrolysis system (100) according to one of the preceding claims, in which the electrolyser (13) is designed as a PEM electrolyser.Method for operating an offshore electrolysis system (100) according to one of the preceding claims, in which water is broken down into hydrogen (H 2) and oxygen by an electrolyser (13) of the electrolysis plant (5) arranged below the sea level (25), wherein the hydrogen (H 2) produced is transported away via a product gas line (7).Method according to claim 11, wherein in the electrolyser (13) a pressure electrolysis is carried out at a working pressure (p), the working pressure (p) being adapted to the hydrostatic pressure at the site of use at a depth (h) below the sea level (25).

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