Offshore electrolysis system and methods for operating an offshore electrolysis system

Abstract

The invention relates to an offshore electrolysis system (100) comprising a wind turbine (1) with a platform (3) and with an electrolysis plant (5) arranged on the platform (3), which is connected to the wind turbine (1) for supplying electrolysis current, and further comprising a heat supply device (7) coupled to the electrolysis plant (5), which is designed in such a way that heat can be transferred to the electrolysis plant by means of the heat supply device (7) during standstill operation, so that a temperature above a minimum temperature is maintained. The invention further relates to a method for operating a corresponding offshore electrolysis system. In this method, heat is transferred to the electrolysis plant (5) by means of the heat supply device (7) during standstill operation, so that a temperature above a minimum temperature is maintained and freezing of water-carrying components of the electrolysis plant (5) is prevented.

Description

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

[0002] An electrolysis plant is a device that uses electric current to bring about a chemical transformation (electrolysis). Corresponding to the variety of different electrochemical electrolysis processes, there are also numerous electrolysis plants, such as those for water electrolysis. Electrolysis plants are connected to power generation plants to supply the electrolysis current, thus forming an electrolysis system. Typically, an electrolysis plant has several electrolyzers, enabling high electrolysis capacities for the electrochemical transformation with appropriate scaling.

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

[0004] Current considerations focus on using surplus energy from renewable energy sources during periods of high sunshine and wind power generation—that is, during periods of above-average solar or wind power production—to produce valuable materials. One such valuable material could be hydrogen, produced through water electrolysis. This hydrogen can then be used, for example, to manufacture so-called renewable energy gas (RE-gas). RE-gas is a combustible gas produced using electricity generated from renewable sources.

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

[0006] Wind power is a source of renewable energy. Particularly with offshore wind turbines located near the coast, large amounts of electricity can be generated. However, a challenge lies in overcoming the considerable distance to consumers. Therefore, the energy should be transported to the consumer with as little loss as possible. Hydrogen is very well suited as a transport medium. It can be transported in gaseous form, for example, via pipelines. A positive side effect of this is that a hydrogen pipeline can simultaneously function as an energy storage device, since the internal pressure can be varied within certain limits. For this reason, it is particularly interesting to produce hydrogen directly at the point of energy generation, i.e., to place offshore electrolysis plants directly at or in the immediate vicinity of offshore wind turbines.For example, offshore electrolysis systems are currently being discussed in which an electrolysis plant is installed directly on the platform of an offshore wind turbine. The wind turbine and the electrolysis plant can then be combined to form a largely self-sufficient, i.e., almost grid-independent, electrolysis system and be specially equipped for offshore island operation.

[0007] Ideally, these electrolysis systems, comprising a combination of a wind turbine and an electrolysis plant, can be built entirely without any grid connection and designed exclusively for island operation. This applies particularly to electrolysis systems located far offshore to avoid long connection distances to the public grid in coastal regions. The electrolysis plant, with its multiple electrolyzers, is ideally positioned in close proximity to the renewable energy source, i.e., the wind turbine, to minimize or eliminate both transformation and transmission losses. Therefore, offshore electrolysis systems with electrolysis units installed directly on a platform housing an offshore wind turbine are currently being developed with great intensity.With such a connection, whether onshore or offshore, the system can operate even without being connected to the power grid. Without a grid connection, however, during periods of calm winds, lulls, or planned maintenance, for example at the turbine of the wind turbine, no electricity is available, neither from the generator nor from the power grid.

[0008] Offshore electrolysis systems require special attention to prevent corrosion of the electrolysis unit, as the presence of saltwater can lead to significantly higher corrosion rates, jeopardizing the long-term, uninterrupted operation of the electrolysis plant. In principle, offshore electrolysis plants can be equipped with electrolyzers housed within enclosed containers. This provides a degree of protection for the electrolyzer from external environmental influences. However, during normal operation, the electrolyzer must be cooled to continuously dissipate the waste heat generated by the electrolysis process.In general, thermal management is particularly challenging for offshore electrolysis plants compared to onshore plants, both in terms of the necessary cooling during normal operation and maintaining a minimum temperature during extended periods of inactivity. In the latter case, ensuring adequate protection against freezing of the water-soaked electrolysis cells is crucial, especially during periods of low wind and when the wind turbine is idle in the winter months. Therefore, to meet the cooling requirements for offshore electrolysis plants during normal operation, a closed container design—i.e., an enclosure to protect the electrolyzer—is standard practice. This design must simultaneously prevent overheating and failure of the electrolyzers, as well as damaging corrosion from marine salt exposure.Therefore, in an offshore electrolysis plant, an interface and exchange between the electrolyzer and the environment is ultimately unavoidable in order to adequately dissipate the heat flow of the process heat during normal operation and to enable safe operation.

[0009] To protect the electrolyzers from environmental influences, they require an enclosure, such as a container, as described above. PEM water electrolyzers must also be operated with demineralized, and especially high-purity, water. The internal temperature of the container must therefore not fall below approximately 5°C. Otherwise, the water-carrying components containing water could freeze and disable the entire system. This would defeat the purpose of operating offshore electrolysis systems with off-grid wind turbines with minimal maintenance and maximum self-sufficiency.

[0010] When the outside temperature outside the enclosure is below 5°C, heat is transported from the interior of the container to the outside via conduction, convection, and radiation. At the minimum design temperature of -20°C, approximately 1 to 2 kW of thermal energy per hour dissipates from each container of the electrolysis plant. The heat loss, however, depends, among other things, on the insulation of the container itself. This heat must be supplied back to the container to maintain a relatively constant temperature of 5°C and reliably prevent freezing damage. Maintaining this temperature within 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, because sufficient waste heat from the electrolysis process is available.

[0011] However, if no renewable electricity is available during very cold weather, for example due to lack of wind or a necessary shutdown of the wind turbine for potentially unforeseen maintenance, the thermal energy required to maintain the necessary temperature of the electrolysis plant must be supplied by other means and reliably. Otherwise, irreversible damage to the electrolysis cells from frost damage and even total loss of the electrolyzers installed in the electrolysis plant are imminent. The water-carrying pipes between the containers or enclosures must also be kept at a minimum temperature to prevent them from freezing. This also requires energy, which must be supplied from other sources when there is no wind.

[0012] Some proposed solutions already include the use of, and reliance on, appropriately designed battery storage systems for the electrolysis system. The battery storage provides electrical power to maintain electric heating and temperature. However, this solution has significant drawbacks. The capacity of battery packs, on the one hand, and the available space on an offshore platform, on the other, are considerably limited. For the present application on an offshore wind farm platform, for example, relatively high battery capacities of at least approximately 100 to 150 kWh would be realistically required to ensure temperature maintenance even during extended periods of inactivity. This appears uneconomical with currently available battery technologies. Especially in cold ambient temperatures, the cold impairs the performance of the batteries.Because the electrolyte becomes more viscous and difficult to penetrate in the cold, fewer ions reach the positive terminal, causing a sharp drop in battery performance. The cold also significantly slows down processes within the battery, leading to faster than usual battery wear. Furthermore, so-called battery energy storage systems (BESS) are quite expensive, large, and heavy. Therefore, there is an urgent need for alternative, improved solutions for maintaining the temperature during the standstill operation of an offshore electrolysis system.

[0013] Another, arguably simpler, technical 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 needs to be refilled regularly, and therefore the fundamental idea and objective of developing reliable, CO2-free offshore electrolysis systems cannot be realized with this approach.

[0014] The object of the present invention is therefore to provide an offshore electrolysis system that enables safe and environmentally friendly operation, and at the same time to design it for the most self-sufficient and low-maintenance operation possible. A further object is to provide a method for operating an offshore electrolysis system.

[0015] The problem directed towards an offshore electrolysis system is solved according to the invention by an offshore electrolysis system comprising a wind turbine with a platform and with an electrolysis plant arranged on the platform, which is connected to the wind turbine for the supply of electrolysis current, and further comprising a heat supply device coupled to the electrolysis plant, which is designed in such a way that heat can be transferred to the electrolysis plant by means of the heat supply device in a standstill operation, so that a temperature above a minimum temperature is maintained.

[0016] The problem directed towards a method for operating an offshore electrolysis system is solved according to the invention by a method for operating a corresponding offshore electrolysis system, wherein heat is transferred to the electrolysis plant by means of a heat supply device during standstill operation, so that a temperature above a minimum temperature is maintained and freezing of water-carrying components of the electrolysis plant is prevented.

[0017] The advantages and preferred configurations listed below with regard to the offshore electrolysis system can be applied analogously to the method for operating the electrolysis system.

[0018] The invention is based on the understanding that the increasing number of installed, more powerful, off-grid offshore wind turbines and their growing electrical generation capacity necessitate correspondingly more powerful electrolysis plants. It is therefore expected that the power class and number of offshore electrolysis systems will increase significantly in the future.

[0019] The associated increasing demands for safe and environmentally sound operation in a maritime environment must be taken into account. With the scaling efforts towards larger offshore electrolysis systems far from the coast, the question of achieving the most self-sufficient, i.e., grid-independent, island operation possible with 100% hydrogen production from renewable wind power, alongside the environmental compatibility of such systems, is moving into the focus of discussion. From an environmental perspective, it is essential to ensure operation with minimal intervention. Therefore, a self-sufficient solution for maintaining the temperature of the electrolysis plant, particularly with regard to the water-bearing components, especially the particularly sensitive water-soaked electrolysis cells of a PEM electrolysis system, is crucial for situations involving downtime, especially in the event of wind turbine failure and a loss of electrolysis power.The invention's concept ensures a reliable heat supply and temperature control, thus eliminating the risk of failure or loss of water-carrying components, even during periods of low ambient temperatures and potential freezing during the winter months. The invention implements a heat retention concept in an offshore electrolysis system that is characterized by high reliability and inherent fail-safe operation under critical weather conditions and operating situations. This results in a virtually maintenance-free offshore electrolysis system that effectively mitigates the risk of frost damage caused by freezing of water-carrying components of the electrolysis plant, particularly the electrolyzer and electrolysis cells. Consequently, the system achieves a long service life and immediate availability and operational readiness for resuming normal operation after downtime.

[0020] The offshore electrolysis system of the invention advantageously recognizes and overcomes, for the first time, the disadvantages of conventional heat supply concepts for off-grid electrolysis systems, which—as described above—rely on very large battery packs or even diesel generators installed on the platform to supply heat to the electrolysis plant. These approaches prove to be very disadvantageous from an environmental perspective and are also expensive and maintenance-intensive. With the heat supply system, however, temperature maintenance is ensured even for several days during periods of low wind and solar power generation, with the heat transfer being adjustable to maintain a required minimum temperature. Thus, the heat supply system is specifically adapted to the needs of the electrolysis plant, minimizing both heat output and heat consumption for temperature maintenance.

[0021] In a particularly preferred embodiment of the offshore electrolysis system, the electrolysis plant comprises an electrolyzer arranged in a container and a heat exchanger which, in normal operation, is designed to dissipate process heat from the electrolysis from the container.

[0022] This advantageously ensures that waste heat generated during the electrolysis process can be used for temperature maintenance during standby operation, rather than simply being released into the environment. Typically, during electrolysis, the process heat from the container surrounding the electrolyzer, which protects it from weather and salt ingress, is dissipated to the environment. In this case, the heat exchanger is advantageously designed to selectively transfer the process heat from the electrolysis to the heating system as needed, particularly to store the heat and make it available for later use in temperature maintenance. Therefore, the process heat is not, or only partially, released into the environment.

[0023] Simultaneously, the heat exchanger, during normal operation, assists in cooling the container and thus the electrolyzer with its multiple electrolysis cells. 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, enabling targeted heat absorption and release, as well as further utilization in the heat supply system, on the secondary side of the heat exchanger. This advantageously enables the safe and environmentally friendly operation of an offshore electrolysis system in a closed container design with an electrolyzer located within the container, such as a PEM electrolyzer for hydrogen production, and with a coolant pump located within 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 coolant pump, so that, in this sense, the coolant pump is also located within the container. With the closed cooling circuit, heat absorption from the electrolysis process at the plant is achieved via the heat exchanger in the container. It is also possible for several heat exchangers to be provided, with a suitably configured heat exchanger forming part of the heat supply system.

[0024] In a further preferred embodiment of the offshore electrolysis system, the heat supply unit includes a heat pump coupled to a heat reservoir.

[0025] This ensures that stored heat from the heat reservoir is extracted by the heat pump and transferred via the heat exchanger to the frost-prone components of the electrolysis plant. This is particularly important during periods of inactivity when there is an acute risk of frost, as heat from the reservoir is provided to maintain the temperature above the required minimum level.

[0026] In a particularly preferred embodiment of the offshore electrolysis system, the heat supply unit includes a heat pump with a deep probe designed for extracting heat from the seawater.

[0027] This provides a particularly advantageous way to reliably protect off-grid offshore electrolysis systems from frost damage when the ambient temperature above water is below 5°C. The electrolysis plant, especially the frost-prone electrolyzer, can be supplied with heat by means of a deep-sea heat pump that utilizes the deep seawater as a heat reservoir.

[0028] For this purpose, a small battery storage system with a relatively low electrical energy capacity can preferably be used solely for operating the heat pump. Capacities of significantly less than 50 kWh are sufficient, typically in the range of 20 kWh to 30 kWh to supply heat to several electrolyzers, each housed in a corresponding number of containers on an offshore platform. The significant advantage lies in the fact that the required capacity is considerably smaller than the amount of heat needed to maintain the temperature, since the water temperature in deeper layers remains above 0°C even in winter.The operating principle of a heat pump, where the smaller the temperature difference between the energy source and the required usable heat, the less drive power is needed, results in energy savings and thus a cost advantage compared to purely electric heating with large battery packs or diesel generators. For example, a water-to-water heat pump (WWHP) can be used to extract heat from deep seawater as a heat reservoir. Depending on the heat pump's operating principle, it is also possible that a refrigerant, rather than water, is used as the operating medium in the pipes of the deep borehole, circulating in a closed loop. With typical coefficients of performance (COP) of at least 4 to 5, at least four to five times the input power is available as usable heat output; this additional gain 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 together in offshore applications when the electrolysis system is in standstill operation.

[0029] In a particularly preferred embodiment of the offshore electrolysis system, the heat supply unit is arranged on the tower of the wind turbine, with the depth probe being immersed in the seawater.

[0030] Attaching and securing a geothermal heat supply unit with a deep-well probe externally to the wind turbine tower offers the additional advantage that no extra space is required on the platform for the installation. Furthermore, mounting and aligning the unit on the tower is structurally straightforward and poses no static challenges. Operational advantages arise primarily from the ability to vertically and unobstructedly immerse and position the deep-well probe down to the required operating depth. The heat supply unit extends at least partially above sea level to facilitate simple thermal coupling and heat transfer to the electrolysis unit via the heat exchanger, approximately at the level of the electrolysis plant located on the platform.

[0031] In a further advantageously designed offshore electrolysis system, the heat supply device has a heat storage unit which is designed in such a way that in normal operation the heat storage unit can be charged with waste heat from the electrolysis process and in standstill operation heat stored in the heat storage unit can be supplied to the electrolysis plant.

[0032] This provides an additional way to reliably protect a non-grid-connected offshore electrolysis system from frost damage when the ambient temperature above water is below 5°C. The operating principle involves supplying the electrolysis plant with thermal energy via a heat pump, which uses a dedicated thermal storage tank as its heat reservoir. This configuration can be installed as an alternative or an additional component to the heat supply system with a deep borehole and seawater as an unlimited heat reservoir, as described above. In this configuration, the thermal storage tank is advantageously installed as a component of the offshore electrolysis system, for example, on the platform or in a container.

[0033] In a particularly advantageous integration and design of the offshore electrolysis system, the heat supply unit features a heat reservoir which is formed within the tower of the wind turbine.

[0034] In this way, the heat reservoir can, for example, be formed or integrated as a suitable thermal storage unit within the tower of the wind turbine itself. The heat reservoir is preferably located deep below the water's surface within the tower to take advantage of the most constant possible ambient temperature underwater. This design, involving an enclosure within the tower, also advantageously provides thermal insulation for the thermal storage unit. At the same time, integrating a thermal storage unit deep inside the tower hardly affects the mechanical stability of the tower structure and the nacelle housing the wind turbine. Furthermore, it creates or utilizes space for a thermal storage unit that would otherwise remain unused. The thermal storage unit requires no additional space or installation area on the platform itself.The latter can be used without restriction by the heat supply system for the electrolysis plant and its components.

[0035] In an advantageous embodiment, the offshore electrolysis system has a heat reservoir in which a heat storage medium is introduced.

[0036] The heat reservoir, containing the container with the heat storage medium, can be located, for example, geodetically below the electrolysis plant in its foundation area or within the tower's foundation. The heat reservoir can be, for instance, an insulated water basin or a cavern-like container with a salt as the heat storage medium. The respective heat storage medium is introduced into the container and fills it at least partially or completely.

[0037] This heat storage medium is advantageously charged with heat using the waste heat from the electrolyzer of the electrolysis plant during its normal operation. When the entire system is idle, the stored heat energy can then be fed back from the electrolysis plant's heat reservoir via a line as needed to prevent frost damage. Here, too, a certain amount of stored electrical energy is provided for the operation of a heat pump to circulate and maintain heat exchange. Due to the temperature levels, a high coefficient of performance (COP) is expected, meaning that significantly less electrical energy than the heat energy required for temperature maintenance needs to be stored. This again results in energy savings and thus a cost advantage through a considerably smaller auxiliary battery for standby operation.

[0038] In a particularly preferred embodiment of the offshore electrolysis system, water and / or a latent heat storage material with a low melting point between about 30°C and 70°C is provided as the heat storage medium, in particular a salt, a salt mixture or a paraffin.

[0039] Water is already available in the offshore electrolysis system, and in general, water is an excellent heat storage medium due to its high specific heat capacity. Furthermore, it is easy to handle and particularly environmentally friendly. Therefore, a heat storage system using water as the heat storage medium is advantageous and very easy to operate. However, latent heat storage materials also offer significant advantages as heat storage media, especially regarding energy density and the achievable temperature levels during heat release. Moreover, latent heat can be stored for very long periods. Therefore, designing the heat storage system as a latent heat storage system is particularly advantageous for use in the offshore electrolysis system.

[0040] A latent heat storage system, also known as a phase change material (PCM) storage system, is a special type of heat storage device that stores a large portion of the supplied thermal energy in the form of conversion enthalpy, formerly called latent heat, for example, during a phase change from solid to liquid. The stored energy is hidden because, as long as the phase change is not completely complete, the temperature of a substance does not rise further despite the addition of heat. Latent heat storage systems can therefore store very large amounts of heat within a small temperature range around the phase change point, surpassing heat storage systems that only utilize the thermal energy of a single substance, such as hot water storage systems. Since many substances with widely varying melting points are suitable as phase change materials (PCMs), this technology can, in principle, cover many storage applications, from cold storage to high-temperature heat storage.

[0041] In an advantageous design and configuration of the offshore electrolysis system, sodium acetate trihydrate, disodium hydrogen phosphate or mixtures thereof are introduced into the container in supersaturated solution as a latent heat-storing material.

[0042] The latent heat storage material is housed within the container, thus providing a heat reservoir with a high latent heat capacity. Advantageously, the latent heat storage unit can be easily charged during normal operation using the waste heat from the electrolysis process. However, it is also possible, either as an alternative or in addition to charging with waste heat from electrolysis, to use an electrically operated heating element, such as a resistance heating element, within which the latent heat storage unit is located and surrounded by the latent heat storage material. This allows for electrical heating and phase changes with very high thermal output when needed, with the required heating energy being temporarily extracted, for example, directly from the generator side of the wind turbine. The heat reservoir can thus be charged quickly, which is particularly advantageous in weather conditions where another period of low wind and solar output is anticipated.Higher temperatures than the temperature level of the waste heat from electrolysis with the heating element are also possible, so that materials with higher conversion temperatures are available for use in the container if required. It is also possible to draw electrical heating energy from a rechargeable auxiliary battery or from a renewable energy source, such as a photovoltaic system.

[0043] Advantageously, the heat storage device, designed as a latent heat storage system, includes an activation device by means of which crystallization can be brought about and stored latent heat can be released.

[0044] The activation device is designed such that a pressure pulse or pressure wave can be selectively introduced into the charged, latent heat-storing material to trigger the crystallization of the supersaturated solution. For this purpose, a small piezoelectric actuator with a piezoelectric element or a hinged metal plate can be used, for example, to locally trigger a pressure wave that discharges and releases the latent heat within the latent heat-storing material. This occurs because the pressure pulse releases microscopically small crystallization nuclei, which initiate crystallization and release heat.

[0045] Another aspect of the invention relates to a method for operating a corresponding offshore electrolysis system. In this method, heat is transferred to the electrolysis plant via the heat supply unit during standstill operation, thus maintaining a temperature above a minimum temperature and preventing the freezing of water-carrying components of the electrolysis plant.

[0046] The process is advantageously self-sufficient, i.e., it can be carried out without a grid connection for the electrolysis system. Furthermore, the electrolysis system is advantageously designed for island operation, ensuring temperature maintenance and preventing freezing even during periods of low wind and solar power generation.

[0047] Preferably, the process involves initiating temperature maintenance at an outside temperature of less than 5°C, whereby stored heat is extracted from the heat reservoir and transferred to the water-bearing components of the electrolysis system, thus providing freeze protection.

[0048] Heat exchangers are used to couple and transfer the heat stored in the heat reservoir to frost-prone water-bearing components of the electrolysis plant. These exchangers can also be used during normal operation to charge the heat reservoir with waste heat from the electrolysis process, i.e., bidirectionally for cooling the electrolysis plant by selectively dissipating process heat.

[0049] In a preferred embodiment of the process, the electrolysis plant is therefore supplied with electrolysis current by the wind turbine during normal operation, whereby process heat from the electrolyzer is extracted via a heat exchanger and transferred to the heat reservoir.

[0050] In a further preferred embodiment of the process, process heat is extracted from the electrolyzer and transferred to a heat storage medium, thereby charging the heat storage medium.

[0051] 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.

[0052] The features, characteristics, and / or advantages described herein for the offshore electrolysis system apply analogously to the operating process, and vice versa. Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. This drawing shows, schematically and in a highly simplified manner: Fig. 1 an offshore electrolysis system comprising an electrolysis plant and a wind turbine; Fig. 2 a schematic side view of the offshore electrolysis system with a heat supply unit with heat pump; Fig. 3 A schematic side view of the offshore electrolysis system with a heat storage unit.

[0053] The same reference symbols have the same meaning in the figures.

[0054] In Fig. Figure 1 shows an offshore electrolysis system 100. The offshore electrolysis system 100 comprises an electrolysis unit 5 and a wind turbine 1, which has a tower 19, as shown in the upper right part of Figure 1. Fig. Figure 1 is shown. In the lower part of tower 19, there is a platform 3 above sea level 25 (see Figure 1). Fig. 2) attached, which is specifically designed and engineered to accommodate various components for the intended operation of the offshore electrolysis system 100. These components are located in the lower part of the Fig. 1 shown as an example in enlarged view: An electrolysis plant 5 is installed on platform 3 and systemically connected to the wind turbine 1 to form the offshore electrolysis system 100. For this purpose, containers 9 are installed on platform 3, housing electrolysis elements (not shown in detail), such as individual electrolyzers, thus protecting particularly sensitive functional components of the electrolysis plant 5 from the elements. Some of the containers 9 on platform 3 contain control units 27 or so-called "balance-of-plant" elements and provide them with protective housing. These are selected containers 9 that are typically reserved solely for housing and operating these control units 27 and, if applicable, other auxiliary systems of the electrolysis plant 5. In contrast, the electrolyzers for the electrochemical conversion are arranged in containers 9 specifically designed for this purpose.Other components or plant parts housed in Container 9 may also include storage tanks for the feed water of the electrolyzers, or similar items.

[0055] The wind turbine 1 preferably has no grid connection or grid coupling, but instead directly supplies the described electrolysis plant 5 in the self-sufficient offshore electrolysis system 100 with the absorbed wind energy. The electrolysis plant 5 is designed to produce preferably green hydrogen from water electrolysis. Thus, the offshore electrolysis system 100 is designed for off-grid operation and equipped for autonomous use in regions further from the coast. The wind turbine 1 is therefore an offshore wind turbine. [The following appears to be a separate, unrelated section:] From the representations of the Fig. 1 and Fig. 3. In contrast, the means presented according to the invention for the improved heat supply of the offshore electrolysis system 100 are also readily applicable to “onshore” plants.

[0056] The strategy of deploying the electrolysis plant 5 via a number of containers 9, preferably ISO containers, advantageously ensures a simple maintenance and repair process, while simultaneously protecting the plant components from climatic and weather influences as well as from corrosion and damaging mechanical impacts during operation. The electrolysis system 100 is particularly vulnerable in situations where the wind turbine does not produce electricity for electrolysis due to freezing conditions, resulting in an acute risk of the water-carrying systems of the electrolysis plant 5 freezing, especially during a prolonged period of low wind and solar output with the associated risk of freezing during a shutdown.

[0057] This is addressed by the invention with a heat supply device 7, which is advantageously integrated into the electrolysis system 100. The heat supply device 7 is coupled to the electrolysis tray 5 and designed such that, during standstill operation, heat can be transferred to the electrolysis tray 5 by means of the heat supply device 7, thus ensuring that the temperature of the water-carrying systems is maintained above a minimum temperature. Fig. Figure 2 shows an exemplary schematic side view of a suitably equipped offshore electrolysis system 100 with a heat supply unit 7. The heat supply unit 7 is attached to the tower 19 of the wind turbine 1 at approximately the level of the platform 5 and extends along the tower 19 deep into the underwater area 31 below sea level 25. The tower 19 is firmly anchored in the seabed 35 by means of a foundation 33. The heat supply unit 7 has a heat pump 13 with a deep borehole probe 17, so that seawater serves as a heat reservoir 15. Thus, during standstill operation, heat can be extracted from deep areas of the seawater as a heat reservoir 15 by means of the deep borehole probe and pumped by the heat pump 13 and transferred to the electrolysis system 5 via the heat exchanger 11.The deep borehole probe 17 is positioned at a depth where the seawater temperature is advantageous, above approximately 5°C. Due to the favorable coefficient of performance (COP) of the heat pump 13 in the operating environment with only small temperature differences of a few degrees, for example, 1-5°C, only a small, rechargeable battery pack, typically housed in a container 9 with a capacity of approximately 25-30 kWh, is required to power the heat pump. This allows even extended periods of several days during periods of low wind and solar activity in winter to maintain the temperature of the electrolysis plant 5. This provides a particularly advantageous way to reliably protect the off-grid offshore electrolysis system 100 from frost damage when the ambient temperature above water is below 5°C.The electrolysis plant 5, in particular the electrolyzer located in a container 9 which is susceptible to freezing, can be supplied with heat very efficiently by means of the heat pump 13 with a deep borehole probe 17, which uses deep seawater as a heat reservoir 15. The electrolysis plant 5 has an electrolyzer located in a container 9, the waste heat from which can be dissipated as process heat from the container 9 as needed via the heat exchanger 11 or a dedicated cooling circuit. Thus, the heat supply unit 7 can also be used to cool the electrolysis plant 5 during normal operation, if required. The heat supply unit 7 can be structurally integrated into the container 9 in its upper section with the heat exchanger 11.

[0058] Another embodiment of the invention will be described below using the following examples. Fig. Figure 2, which shows a schematic side view of an advantageously equipped offshore electrolysis system 100 with an integrated heat supply unit 7, will be explained. The heat supply unit 7 includes a heat storage unit 21 as a heat reservoir 15. The heat storage unit 21 is designed as a container or cavity within the tower 19 of the wind turbine – in this case, 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 storage unit 21. The heat storage medium 21 can be, for example, water or a latent heat-storing material with a low melting point between approximately 25°C and 80°C, particularly 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 have proven advantageous in the container, as they enable high energy densities of stored latent heat in the heat storage unit at high temperatures during on-demand discharge with heat release. To release the heat from the latent heat-storing material, a [missing information] is required. Fig. Two activation devices (not shown in detail) are provided, by means of which crystallization can be induced and the stored latent heat released. The activation device can, for example, include a pressure pulse generator that 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 tank 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 tank 21 can be charged, for example, by transferring process heat from the electrolysis system 5 to the heat exchange medium via the upper heat exchanger 11.The heat exchanger medium transfers heat to the heat storage medium 23 in the container. In addition to the process heat extracted from the electrolysis plant 5, a resistance heating element can be provided to achieve a higher storage temperature and thus higher storage energy as needed, or to quickly charge materials with high conversion temperatures that store latent heat. A resistance heating element can therefore, for example, be directly inserted into or immersed in the heat storage medium 23. Under normal operating conditions, this resistance heating element is powered by electricity from the wind turbine 1 to charge the heat storage medium 21.

[0059] During a shutdown of the electrolysis system 100, in the event of frost or wind turbine failure, the heat or latent heat stored in the thermal storage unit 21 can be used for long-term temperature maintenance to reliably prevent sensitive water-bearing components of the electrolysis unit 5 from freezing. This applies in particular to the protection of components such as the electrolyzer with its numerous electrolysis cells, as well as the water-filled gas separators and auxiliary systems and lines of the hydraulic topology of the electrolysis unit 5. Thus, in a method for operating the offshore electrolysis system 100 during a shutdown, heat stored in the thermal supply unit 7 is transferred to the electrolysis unit 5, thereby maintaining a temperature above a minimum and preventing the freezing of water-bearing components of the electrolysis unit.The temperature maintenance is initiated when the outside temperature is less than 5°C, whereby heat is extracted from the heat reservoir 15 and transferred to the water-bearing components of the electrolysis system 5, thus providing freeze protection.

[0060] In normal operation, the electrolysis plant 5 is supplied with electrolysis current by the wind turbine 1. Process heat from the electrolyzer is dissipated via the upper heat exchanger 11 and transferred to the heat reservoir 15. Thus, process heat is transferred to a heat storage medium 23, thereby charging the heat storage unit 21. In a special and advantageous configuration of the heat storage unit 21 according to Fig.2. The heat storage unit 21 is charged by transferring heat to a latent heat-storing material, in particular a salt, whereby 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 unit 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

[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) comprises 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 depth 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, in which the heat supply device (7) has a heat accumulator (21) which is designed such 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) comprises 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] Method for operating an offshore electrolysis system (100) according to one of the preceding claims, wherein, in a standstill operation, heat is transferred to the electrolysis plant (5) by means of the heat supply device (7), so that a temperature is maintained above a minimum temperature and freezing of water-carrying components of the electrolysis plant (5) is prevented. [13] 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 plant (5), so that freezing protection is effected. [14] Method according to claim 12 or 13, wherein in normal operation the electrolysis plant (5) is supplied with electrolysis current from the wind turbine (1), wherein process heat is derived from the electrolyzer via a heat exchanger (11) and transferred to the heat reservoir (15). [15] 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 (21) is charged. [16] Method according to claim 15, wherein 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.

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