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 platform (3) and with 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 heat supply device (7) which is coupled to the electrolysis plant (5) and is designed in such a way that heat can be transferred to the electrolysis plant by means of the heat supply device (7) during a standstill mode so as to maintain the temperature above a minimum temperature. The invention also relates to a method for operating a corresponding offshore electrolysis system. During a standstill mode, heat is transferred to the electrolysis plant (5) by means of the heat supply device (7) so as to maintain the temperature above a minimum temperature and prevent freezing of water-carrying components of the electrolysis plant (5).

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 an electrolysis plant is set up directly on the platform of an offshore 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 can comprise a combination of a wind turbine and an electrolysis plant and can be built entirely without any auxiliary connection to a power grid and can be designed exclusively for island operation. This particularly applies to electrolysis systems set up far off the coast in order to avoid long connections to the public grid in the coastal region. The electrolysis plant with a number of electrolyzers is ideally located close to the renewable energy sources, i.e.of 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 set up directly on a platform with an offshore wind turbine are currently being developed with great intensity. With this type of coupling, regardless of whether it is onshore or offshore, the plant can also be operated without a connection to the power grid. Without a grid connection, however, during calm periods, i.e. when there is no wind, no wind at all, or during planned maintenance work on the wind turbine, no power is available from the generator or the power grid.

[0009] In offshore electrolysis systems, special attention must 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 provides 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 maintaining a minimum temperature during extended downtimes. In the latter case, sufficient freeze protection for the water-soaked electrolysis cells of the electrolyzers must be ensured, especially 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 therefore established. This requires, on the one hand, to avoid overheating and failure of the electrolyzers 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.

[0010] To protect the electrolyzers from environmental influences, they require, as explained above, an enclosure such as a container. PEM water electrolyzers must also be operated with demineralized, particularly ultrapure, 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.

[0011] At an external temperature outside the enclosure which is lower than 5 °C, heat is transported from the interior of the container to the outside by conduction, convection and thermal radiation. At the minimum design temperature outside of -20 °C, around 1 to 2 kW of thermal energy per hour is dissipated from each container in the electrolysis plant. The heat loss depends, among other things, on the insulation of the container itself. This heat must be fed back into the container in order to keep the 5 °C reasonably constant and to reliably prevent damage from freezing. This temperature maintenance in the container can be guaranteed during normal operation of the electrolysis plant, i.e. when supplied with electrolysis power from the wind turbine, even at very low ambient temperatures, as sufficient waste heat is available from the electrolysis process.

[0012] If, on the other hand, renewable electricity is not available during very cold weather - for example because there is no wind or if the wind turbine has to be shut down for unforeseen maintenance - the heat energy to maintain the temperature in the electrolysis plant must be provided safely and reliably by another source. Otherwise, there is a risk of irreversible damage to the electrolysis cells due to frost and even total loss of the electrolyzers installed in the electrolysis plant. The water pipes between the containers or enclosures must also be kept at a minimum temperature to prevent them from freezing. This also requires energy, which has to be provided from other sources when there is no wind.

[0013] Solutions that have already been proposed include the use of and recourse to appropriately designed battery storage in the electrolysis system. The battery storage provides electrical power to maintain electrical heating and temperature. However, this solution has considerable disadvantages. For example, the capacity of battery units and the installation space on an offshore platform are significantly limited. Realistically, for the present application on an offshore wind turbine platform, for example, quite high battery capacities of at least 100 to 150 kWh would be required to ensure temperature maintenance even during extended periods of standstill. This does not appear to be economical with the battery technologies currently available. The cold slows down the batteries, especially in cold ambient temperatures.The cold makes the electrolyte more viscous and difficult to penetrate. As a result, fewer ions reach the positive pole, and battery performance drops dramatically. The cold significantly slows down processes in the battery, causing the battery to wear out faster than usual. So-called battery energy storage systems (BESS) also have the disadvantage of being quite expensive, large, and heavy. Therefore, there is an urgent need for other, better solutions for maintaining temperature during standstill of an offshore electrolysis system.

[0014] Another, technically simple solution is the integration of a diesel generator for emergency power supply and operation of a heating system on the offshore platform. However, this solution has the disadvantage that the diesel fuel must be regularly refilled, thus the basic idea and objective of developing reliable, CO2-free offshore electrolysis systems cannot be realized with this approach.

[0015] The object of the present invention is therefore to provide an offshore electrolysis system that enables safe and environmentally friendly operation, while simultaneously designing it for operation that is as self-sufficient and low-maintenance as possible. A further object is to provide a method for operating an offshore electrolysis system.

[0016] 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 heat supply device coupled to the electrolysis system, which is designed in such a way that in standstill operation heat can be transferred to the electrolysis system by means of the heat supply device, so that a temperature is maintained above a minimum temperature.

[0017] The object directed to a method for operating an offshore electrolysis system is achieved according to the invention by a method for operating a corresponding offshore electrolysis system, wherein during standstill operation heat is transferred to the electrolysis system by means of a heat supply device, so that a temperature is maintained above a minimum temperature and freezing of water-carrying components of the electrolysis system is prevented.

[0018] The advantages and preferred embodiments listed below with regard to the offshore electrolysis system can be transferred analogously to the method for operating the electrolysis system.

[0019] The invention is based on the realization that the increasingly installed, more powerful, grid-independent offshore wind turbines and their growing electrical generation capacity require correspondingly more powerful electrolysis systems. It is therefore expected that the power class of offshore electrolysis systems and their number will increase significantly in the future.

[0020] The associated increasing demands on 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 with the least possible intervention must be guaranteed. A self-sufficient solution for safely maintaining the temperature of the electrolysis plant with regard to the water-bearing components, in particular the particularly sensitive water-soaked electrolysis cells of a PEM electrolysis plant, in situations with a standstill, especially in the event of a failure of the wind turbine and no electrolysis power, is therefore of crucial importance.The concept of the invention ensures heat supply and temperature maintenance so that there is no risk of failure or loss of water-bearing components even when there is a risk of frost during a period of darkness with low ambient temperatures in the winter months. The invention therefore implements a heat maintenance concept in an offshore electrolysis system which is characterized by high reliability and intrinsic fail-safe operation in critical weather conditions and operating situations. This creates a practically maintenance-free offshore electrolysis system which reliably counteracts the risk of frost damage caused by freezing of water-bearing components of the electrolysis system, in particular the electrolyzer and the electrolysis cells. This leads to a long service life and immediate availability and operational readiness for resuming normal operation after a shutdown.

[0021] The offshore electrolysis system of the invention advantageously recognizes and overcomes for the first time the disadvantages of conventional heat supply concepts in grid-independent electrolysis systems which - as described above - rely on very large battery units or even diesel generators installed on the platform to supply heat to the electrolysis plant when needed. These approaches also prove to be very disadvantageous from an environmental point of view and, moreover, expensive and maintenance-intensive. With the heat supply system, on the other hand, temperature can be maintained even over several days in the dark during a lull, with the heat transfer being adjustable to a required minimum temperature which is maintained. The heat supply system is thus specifically adapted to the needs of the electrolysis plant for minimal heat output and minimal heat consumption for temperature maintenance.

[0022] In a particularly preferred embodiment of the offshore electrolysis system, the electrolysis plant has an electrolyzer arranged in a container and a heat exchanger which, during normal operation, is designed to dissipate process heat from the electrolysis from the container.

[0023] This advantageously ensures that waste heat generated from the electrolysis process during normal operation can be used to maintain the temperature during standstill operation if required and is not simply released into the environment. Normally, during electrolysis operation, the process heat is dissipated into the environment from the container surrounding the electrolyzer, which protects it from the weather and salt ingress. In this case, the heat exchanger is advantageously designed to transfer the process heat from the electrolysis to the heat supply system when required, in particular to store the heat and keep it available for later use to maintain the temperature. The process heat is therefore not released into the environment, or at most only partially,.

[0024] At the same time, the heat exchanger supports the cooling of the container and thus of the electrolyzer with its large number of electrolysis cells during normal operation. For this purpose, the heat exchanger can, for example, be connected on the primary side to a coolant circuit of the electrolyzer driven by a coolant pump and thermally coupled to it accordingly, so that targeted heat absorption and release as well as further use in the heat supply system on the secondary side of the heat exchanger is achieved. This advantageously enables safe and environmentally friendly operation of an offshore electrolysis system in a closed container design with an electrolyzer arranged in the container, for example a PEM electrolyzer for hydrogen production, and with a coolant pump arranged in the container or a coolant pump tightly flanged to the container.In the latter case, a housing unit is formed between the container and the flanged-on coolant pump, so that, in the sense understood, the coolant pump is also located in the container. With the closed cooling circuit, the heat absorption of process heat from the electrolysis at the plant is achieved via the heat exchanger in the container. It is also possible to provide multiple heat exchangers, with a specially configured heat exchanger forming part of the heat supply system.

[0025] In a further preferred embodiment of the offshore electrolysis system, the heat supply device comprises a heat pump which is coupled to a heat reservoir.

[0026] This ensures that stored heat is extracted from the heat reservoir by the heat pump and transferred via the heat exchanger to the components of the electrolysis system that are at risk of frost. This is particularly true during shutdowns when there is an acute risk of frost, with heat from the heat reservoir being provided to maintain the temperature above a required minimum.

[0027] In a particularly preferred embodiment of the offshore electrolysis system, the heat supply device comprises a heat pump with a deep well which is designed to extract heat from the seawater.

[0028] This provides a particularly advantageous way to reliably protect offshore electrolysis systems not connected to the grid from frost damage when the outside water temperature is below 5°C. Heat can be supplied to the electrolysis system, particularly to the electrolyzer, which is vulnerable to frost, using a heat pump with a deep-well probe that uses deep seawater as a heat reservoir.

[0029] For this purpose, a small battery storage unit with a certain low electrical energy capacity can be used solely to operate the heat pump. Capacities of significantly less than 50 kWh are sufficient here, typically in the range of 20 kWh - 30 kWh to supply heat to a number of electrolyzers, each of which is arranged in a corresponding number of containers on an offshore platform. The significant advantage is that the required capacity is significantly smaller than the amount of heat needed to maintain the temperature, since the water temperature in deeper layers is always above 0 °C, even in winter.The principle of operation of the heat pump, whereby the smaller the temperature difference between the energy source and the required useful heat, the less drive power is required, results in energy savings and therefore a cost advantage compared to a purely electric heating system with large battery units or diesel generators. For example, a water-water heat pump (WWHP) can be used to extract heat from deep sea water as a heat reservoir. However, depending on the principle of operation of the heat pump, it is also possible that the operating medium in the pipes of the deep borehole probe is not water, but a coolant that circulates in a closed circuit. With typical coefficients of performance of at least 4 to 5, at least four to five times the output used is available as usable heat output; the additional power comes from the ambient heat extracted from the heat reservoir.The coefficient of performance depends strongly on the lower and upper temperature levels, which are very close to each other in offshore applications when the electrolysis system is at standstill.

[0030] In a particularly preferred embodiment of the offshore electrolysis system, the heat supply device is arranged on the tower of the wind turbine, with the depth probe being immersed in the seawater.

[0031] Attaching and fastening a heat supply device with a depth probe outside on the tower of the wind turbine has the additional advantage that no additional space is required on the platform for installing the heat supply device. Furthermore, fastening and alignment on the tower is structurally simple and poses no static problems. Operational advantages arise above all from vertical and obstacle-free immersion and positioning of the depth probe down to the sea depth intended for the operating temperature. The heat supply device protrudes at least partially above sea level in order to achieve the simplest possible thermal coupling and heat transfer to the electrolysis system via the heat exchanger, approximately at the level of the electrolysis system arranged on the platform.

[0032] In a further advantageously designed offshore electrolysis system, the heat supply device has a heat storage device which is designed in such a way that in normal operation the heat storage device can be loaded with waste heat from the electrolysis process and in standstill operation the heat stored in the heat storage device can be supplied to the electrolysis system.

[0033] This creates a further option for reliably protecting a non-grid-connected offshore electrolysis system from frost damage when the outside temperature above water is below 5°C. The operating principle here is that thermal energy is supplied to the electrolysis system by means of a heat pump, which uses a specially designed heat storage unit as a heat reservoir. This design can be installed as an alternative or additional supplement to the design of the heat supply system with a deep well using seawater as an unlimited heat reservoir, as described above. In this design, the heat storage unit is then advantageously installed as a component of the offshore electrolysis system, for example, on the platform or in a container.

[0034] In a particularly advantageous further connection and equipment of the offshore electrolysis system, the heat supply device has a heat reservoir which is formed within the tower of the wind turbine.

[0035] In this way, the heat reservoir can, for example, be formed or incorporated as a corresponding heat storage device by means of a cavity within the tower of the wind turbine itself. The heat reservoir is therefore preferably embedded deep below the water surface within the tower in order to take advantage of the most constant ambient temperature underwater. This construction by inclusion in the tower also advantageously results in the heat storage device having a thermal insulation effect. At the same time, the installation of a heat storage device in a cavity deep inside the tower hardly affects the mechanical stability of the tower structure and the nacelle with the wind turbine. Furthermore, installation space is created or utilized for a heat storage device that would otherwise remain unused. The heat storage device does not require any area or installation space on the platform itself.The latter can be used without restriction by the heat supply system for the electrolysis plant and its components.

[0036] In an advantageous embodiment, in the offshore electrolysis system, the heat reservoir comprises a container into which a heat storage medium is introduced.

[0037] The heat reservoir with the container containing the heat storage medium can, for example, be formed or housed geodetically beneath the electrolysis plant in its foundation area or within the foundation of the tower. The heat reservoir can, for example, be designed as a container, an insulated water basin, or as a cavern-like container with salt as the heat storage medium.

[0038] The respective heat storage medium is introduced into the container and fills it at least partially or completely.

[0039] This heat storage medium is advantageously charged with heat using the waste heat from the electrolyzer in the electrolysis plant during normal operation. When the entire plant is at a standstill, the stored heat energy can then be fed back in via a pipe from the electrolysis plant’s heat reservoir if required to prevent frost damage. Here, too, a certain amount of stored electrical energy is required to operate a heat pump to circulate and maintain heat exchange via the heat pump. Due to the temperature levels, a high coefficient of performance is to be expected, meaning that significantly less electrical energy needs to be kept in reserve than the heat energy required to maintain the temperature. This again results in energy savings and therefore a cost advantage due to a significantly smaller auxiliary battery for standstill operation.

[0040] In a particularly preferred embodiment of the offshore electrolysis system, water and / or a latent heat storing material with a low melting point between approximately 30 °C and 70 °C is provided as the heat storage medium, in particular a salt, a salt mixture or a paraffin.

[0041] Water is already available in the offshore electrolysis system and water in general is a very good heat storage medium due to its high specific heat capacity, which is also easy to handle and particularly environmentally friendly. Therefore, a heat storage system with water as the heat storage medium is advantageous and very simple to operate. In particular, materials that store latent heat also have very great advantages as a heat storage medium, especially with regard to energy density and the achievable temperature levels during heat release. Furthermore, latent heat can be stored for a very long time. Therefore, the design of the heat storage system as a latent heat storage system is particularly advantageous for use in the offshore electrolysis system.

[0042] A latent heat storage system, also called a phase change or PCM storage system, is a special type of heat storage system that stores a large portion of the thermal energy supplied to it in the form of transformation enthalpy, formerly known as latent heat, e.g. for a phase change from solid to liquid. The stored energy is hidden because, as long as the phase transformation is not fully complete, the temperature of a material does not rise further despite the addition of heat. Latent heat storage systems can therefore store very large amounts of heat in a small temperature range around the phase change and outperform heat storage systems that only use the thermal energy of a material, such as hot water storage systems. Since many materials with a wide variety of melting points can be used as phase change materials (PCMs), many storage applications, from cold to high-temperature heat storage, can in principle be covered by this technology.

[0043] In an advantageous design and equipment of the offshore electrolysis system, sodium acetate trihydrate, disodium hydrogen phosphate or mixtures thereof are introduced into the container in a supersaturated solution as a latent heat storing material.

[0044] The latent heat storing material is introduced into the container so that a heat reservoir with a high latent heat content is provided. Advantageously, the latent heat storage device can be charged in a particularly simple manner during normal operation using the waste heat from the electrolysis process. However, it is also possible, as an alternative or in addition to charging with waste heat from the electrolysis, to use an electrically operated heating element, for example in the form of a resistance heating element, in which the latent heat storage device is arranged and surrounded by the latent heat storing material. This makes it possible to achieve electrical heating and phase changes with very high heat output as required, with the required heating energy being temporarily extracted directly from the generator side of the wind turbine, for example. The heat reservoir can thus be charged in a short time, which is particularly advantageous in weather conditions where a period of darkness is expected again.Higher temperatures than the waste heat from electrolysis are also possible with the heating element, so that materials with higher transformation temperatures are also available for use in the container if needed. It is also possible for electrical heating energy to be drawn from a rechargeable auxiliary battery or from a renewable energy source, such as a photovoltaic system.

[0045] Advantageously, an activation device is provided in the heat accumulator designed as a latent heat accumulator, by means of which crystallization can be brought about and stored latent heat can be released.

[0046] The activation device is designed in such a way that a pressure pulse or a pressure wave can be introduced into the charged material storing latent heat to trigger the crystallization of the supersaturated solution. For this purpose, a small piezo actuator with a piezo element or a foldable metal plate can be used, for example, so that a pressure wave is locally triggered in the latent heat storing material for the discharge and release of the latent heat. The reason for this is that the pressure pulse releases microscopic crystallization nuclei, which initiate the crystallization and release heat.

[0047] A further aspect of the invention relates to a method for operating a corresponding offshore electrolysis system. During standstill operation, heat is transferred to the electrolysis system by means of the heat supply device, thereby maintaining the temperature above a minimum temperature and preventing freezing of water-bearing components of the electrolysis system.

[0048] The process can be carried out autonomously, i.e., without a grid connection for the electrolysis system. Rather, the electrolysis system is advantageously configured for isolated operation, ensuring temperature maintenance even during periods of low light and preventing freezing.

[0049] Preferably, in the process, temperature maintenance is initiated at an outside temperature of less than 5 ° C, wherein stored heat is taken from the heat reservoir and transferred to the water-carrying components of the electrolysis plant, so that freezing protection is effected.

[0050] Heat exchangers are used to couple or transfer the heat stored in the heat reservoir to the water-bearing components of the electrolysis plant that are at risk of freezing. These can also be used during normal operation to charge the heat reservoir using waste heat from the electrolysis process, i.e., bidirectionally, for cooling the electrolysis plant by selectively dissipating the process heat.

[0051] In a preferred embodiment of the method, the electrolysis plant is therefore supplied with electrolysis current from the wind turbine during normal operation, with process heat being derived from the electrolyzer via a heat exchanger and transferred to the heat reservoir.

[0052] In a further preferred embodiment of the method, process heat is derived from the electrolyzer and transferred to a heat storage medium, whereby the heat storage is charged.

[0053] In a particularly preferred embodiment of the method, the heat storage device is charged by transferring heat to a latent heat-storing material, in particular a salt, whereby the material is at least partially liquefied. Embodiments, features, and / or advantages that relate to the offshore electrolysis system in the present case also apply analogously to the operating method, and vice versa. Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. These show, schematically and in a highly simplified manner:

[0054] FIG 1 an offshore electrolysis system with an electrolysis plant and a wind turbine;

[0055] FIG 2 a schematic side view of the offshore electrolysis system with a heat supply device with heat pump;

[0056] FIG 3 a schematic side view of the offshore electrolysis system with a heat storage unit.

[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 having a tower 19, as shown in the upper right part of FIG. 1. In the lower region of the tower 19, a platform 3 is attached to the tower above sea level 25 (see FIG. 2), which platform is specifically designed and configured to accommodate various system components for the intended operation of the offshore electrolysis system 100. These system 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 exclusively for the 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 include storage tanks for the reactant water of the electrolyzers, or the like.

[0060] The wind turbine 1 preferably has no grid connection or grid coupling in the present case, but rather supplies the described electrolysis system 5 with the absorbed wind energy in the self-sufficient offshore electrolysis system 100, which is designed to produce preferably green hydrogen from water electrolysis. The offshore electrolysis system 100 is therefore 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. Deviating from the illustrations in Figures 1 and 3, the means presented according to the invention for improved heat supply to the offshore electrolysis system 100 can also be readily applied to onshore systems.

[0061] 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 simultaneously protects the plant components from climatic and weather influences as well as from corrosion and damaging mechanical influences during operation. The electrolysis system 100 is particularly vulnerable in situations in which the wind turbine does not produce any power for the electrolysis in frost conditions, so that there is an acute risk of water-carrying systems of the electrolysis plant 5 freezing, particularly during a prolonged period of darkness with the associated risk of frost during standstill operation.

[0062] This is counteracted by the invention with a heat supply device 7, as is advantageously integrated into the electrolysis system 100. The heat supply device 7 is coupled to the electrolysis storage 5 and designed such that, in standstill operation, heat can be transferred to the electrolysis storage 5 by means of the heat supply device 7, so that the temperature of the water-conducting systems is maintained above a minimum temperature. FIG. 2 shows, by way of example, a schematic side view of a suitably equipped offshore electrolysis system 100 with a heat supply device 7. The heat supply device 7 is fastened to the tower 19 of the wind turbine 1 at approximately the height of the platform 5 and projects along the tower 19 deep into the underwater region 31 below sea level 25. The tower 19 is firmly anchored in the seabed 35 by means of a foundation 33.The heat supply device 7 has a heat pump 13 with a deep well probe 17, so that sea water serves as a heat reservoir 15. Thus, when the device is not in operation, heat can be extracted from deep areas of the sea water as a heat reservoir 15 by means of the deep well probe, pumped by the heat pump 13 and transferred to the electrolysis system 5 by means of the heat exchanger 11. The deep well probe 17 is arranged at a depth at a favorable temperature level of the sea water, which is above approximately 5 °C for the higher temperature. Due to the advantageous coefficient of performance of the heat pump 13 in the operating environment with only small temperature differences of a few degrees, for example 1-5 °C, at most a small-sized electric rechargeable battery unit, for example in a container 9, with a typically approximately 25 - 30 kWh electric battery charge, needs to be kept on hand to electrically drive the heat pump.This means that even longer phases of several days of darkness in winter can be bridged to maintain the temperature of the electrolysis plant 5. This creates a particularly advantageous option for reliably protecting the non-grid-connected offshore electrolysis system 100 from frost damage when the outside temperature above water is below 5°C. The electrolysis plant 5, in particular the electrolyzer in a container 9 which is prone to frost, can be supplied with heat very efficiently by means of the heat pump 13 with depth probe 17 which uses the deep sea water as a heat reservoir 15. The electrolysis plant 5 has an electrolyzer arranged in a container 9, the waste heat of which can be dissipated as process heat from the container 9 if required during normal operation.Thus, the heat supply device 7 can also be used, if necessary, to cool the electrolysis plant 5 during normal operation. The heat supply device 7 can be structurally integrated into the container 9 in the upper part with the heat exchanger 11.

[0063] A further exemplary embodiment of the invention will be explained below with reference to FIG. 2, which shows a schematic side view of an advantageously equipped offshore electrolysis system 100 with an integrated heat supply device 7. The heat supply device 7 has a heat accumulator 21 as a heat reservoir 15. The heat accumulator 21 is designed as a container or a cavity within the tower 19 of the wind turbine - in this case incorporated deep below sea level within the foundation 33 and has a corresponding storage volume. A heat storage medium is introduced into the container of the heat accumulator 21. The heat storage medium 21 can, for example, be water or a latent heat-storing material with a low melting point between approximately 25°C and 80°C, in particular between 30°C and 70°C.A salt, a supersaturated salt solution or paraffin can be used as the latent heat storing heat storage medium 23. Salt solutions based on sodium acetate trihydrate, disodium hydrogen phosphate or mixtures thereof in supersaturated solution in the container have proven advantageous since they enable high energy densities of stored latent heat in the heat storage device at high temperatures during discharge with heat release as needed. To release the heat, an activation device - not shown in detail in FIG. 2 - is provided from the latent heat storing material, by means of which activation device the crystallization can be brought about and the stored latent heat can be released. The activation device can have, for example, a pressure pulse generator which can be activated piezoelectrically or mechanically so that crystallization nuclei are formed and activated.An upper heat exchanger 11 and a lower heat exchanger 11 are connected to an exchange line 37 so that a heat exchange medium, e.g. water, can be circulated in a circuit via the heat pump 13. The lower heat exchanger 11 is immersed in the heat storage unit 21 and surrounded by the heat storage medium 23. The upper heat exchanger 11 is coupled to the electrolysis system 5. During normal operation of the electrolysis system 100, the heat storage unit 21 can be charged, for example by process heat from the electrolysis system 5 being transferred to the heat exchange medium via the upper heat exchanger 11. The heat exchange medium transfers the heat to the heat storage medium 23 in the container.In addition to the process heat extraction from the electrolysis system 5, a resistance heating element can be provided in order to achieve a higher storage temperature and thus stored energy if required, or to be able to charge materials that store latent heat and have high transformation temperatures in a short time. A resistance heating element can therefore, for example, be introduced or immersed directly into the heat storage medium 23. During normal operation, this resistance heating element is operated with electricity from the wind turbine 1 in order to charge the heat storage device 21. When the electrolysis system 100 is at a standstill and there is a risk of frost or if the wind turbine fails, the heat or latent heat stored in the heat storage device 21 can be used to maintain the temperature for a longer period in order to reliably prevent sensitive water-carrying components of the electrolysis system 5 from freezing.This particularly concerns the protection of components such as the electrolyzer with its multitude of electrolysis cells, but also the water-filled gas separators as well as auxiliary systems and lines of the hydraulic topology of the electrolysis storage facility 5. Thus, in a method for operating the offshore electrolysis system 100 in standstill mode, heat stored is transferred to the electrolysis system 5 by means of the heat supply device 7, so that a temperature is maintained above a minimum temperature and freezing of water-bearing components of the electrolysis system is prevented. Temperature maintenance is initiated at an outside temperature of less than 5°C, with heat being taken from the heat reservoir 15 and transferred to the water-bearing components of the electrolysis system 5, so that freezing protection is achieved.

[0064] During normal operation, the electrolysis plant 5 is supplied with electrolysis current from the wind turbine 1. Process heat is diverted from the electrolyzer via the upper heat exchanger 11 and transferred to the heat reservoir 15. Process heat is thus transferred to a heat storage medium 23, and the heat storage device 21 is thereby charged. In a special and advantageous embodiment of the heat storage device 21 according to FIG 2, the heat storage device 21 is charged by transferring heat to a latent heat storing material, in particular a salt, wherein the material is at least partially liquefied. The heat of crystallization can be stored for a long time and released as needed.The released latent heat can be used particularly efficiently in the heat supply device 7 for maintaining the temperature of the electrolysis plant 5 via a heat exchanger process by means of the exchange line 37 and the upper heat exchanger and the lower heat exchanger 11.

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 heat supply device (7) coupled to the electrolysis system (5), which is designed such that in standstill operation heat can be transferred to the electrolysis system by means of the heat supply device (7), so that a temperature maintenance above a minimum temperature is effected.

2. Offshore electrolysis system (100) according to claim 1, wherein the electrolysis plant (5) has an electrolyzer arranged in a container (9) and a heat exchanger (11) which, in normal operation, is designed to dissipate process heat from the electrolysis from the container (9).

3. Offshore electrolysis system (100) according to claim 1 or 2, wherein the heat supply device (7) comprises a heat pump (13) coupled to a heat reservoir (15).

4. Offshore electrolysis system (100) according to one of the preceding claims, wherein the heat supply device (7) comprises a heat pump (13) with a deep probe (17) designed to extract heat from the seawater.

5. Offshore electrolysis system (100) according to claim 4, wherein the heat supply device (7) is arranged on the tower (19) of the wind turbine (1), wherein the depth probe (17) is immersed in the seawater.

6. Offshore electrolysis system (100) according to one of the preceding claims, wherein the heat supply device (7) comprises a heat accumulator (21) which is designed such that that in normal operation the heat accumulator (21) can be loaded with waste heat from the electrolysis process and in standstill operation the heat stored in the heat accumulator (21) can be supplied to the electrolysis plant (5).

7. Offshore electrolysis system (100) according to one of the preceding claims, wherein the heat supply device (7) has a heat reservoir (15) which is formed within the tower (19) of the wind turbine (5).

8. Offshore electrolysis system (100) according to claim 7, wherein the heat reservoir (15) comprises a container into which a heat storage medium (23) is introduced.

9. Offshore electrolysis system (100) according to claim 8, wherein the heat storage medium (23) is water and / or a latent heat storing material having a low melting point between approximately 30°C and 70°C, in particular a salt, a salt mixture or a paraffin.

10. Offshore electrolysis system (100) according to claim 9, wherein sodium acetate trihydrate, disodium hydrogen phosphate or mixtures thereof in supersaturated solution is introduced into the container as latent heat storing material.

11. Offshore electrolysis system (100) according to claim 10, wherein an activation device is provided by means of which crystallization can be brought about and stored latent heat can be released.

12. A method for operating an offshore electrolysis system (100) according to one of the preceding claims, wherein in a standstill operation by means of the heat supply device (7) heat is transferred to the electrolysis system (5) so that the temperature is maintained above a minimum temperature and freezing of water-carrying components of the electrolysis system (5) is prevented.

13. The method according to claim 12, wherein the temperature maintenance is initiated at an outside temperature of less than 5°C, wherein heat is taken from the heat reservoir (15) and transferred to the water-carrying components of the electrolysis system (5), so that freezing protection is effected.

14. The method according to claim 12 or 13, wherein in normal operation the electrolysis plant (5) is separated from the wind turbine (1) is supplied with electrolysis current, wherein process heat is derived from the electrolyzer via a heat exchanger (11) and transferred to the heat reservoir (15).

15. The method according to claim 14, wherein process heat is derived from the electrolyzer and transferred to a heat storage medium (23), wherein the heat storage medium (21) is charged.

16. The method according to claim 15, wherein the heat accumulator (21) is charged by transferring heat to a latent heat storing material, in particular a salt, wherein the material is at least partially liquefied.

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