Offshore electrolysis system, and method for operating an offshore electrolysis system
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- SIEMENS ENERGY GLOBAL GMBH & CO KG
- Filing Date
- 2024-08-19
- Publication Date
- 2026-06-03
Smart Images
Figure EP2024073185_03042025_PF_FP_ABST
Abstract
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 offshore electrolysis system is installed directly on an offshore platform.
[0009] An electrolysis plant is installed next to a wind turbine. The wind turbine can be connected to the electrolysis plant to form a largely self-sufficient, i.e. almost grid-independent, electrolysis system and can be specially equipped for offshore island operation. In the best case, these electrolysis systems, comprising a combination of a wind turbine and an electrolysis plant, can also be installed completely without any auxiliary connection to a power grid for supply and can be equipped exclusively for island operation. This particularly applies to electrolysis systems installed far off the coast in order to avoid long connection routes to the public grid in the coastal region. The electrolysis plant with a number of electrolyzers is ideally placed in the immediate vicinity of the renewable energy sources, i.e. the wind turbine, in order to reduce or avoid both transformation and transmission losses.For this reason, offshore electrolysis systems are currently being intensively developed, with electrolysis plants installed directly on a platform with an offshore wind turbine. With such a coupling, whether onshore or offshore, the plant can be operated without a connection to the power grid. Without a grid connection, however, during periods of calm, lulls, or planned maintenance, for example, at the wind turbine's turbine, no power is available from the generator or the power grid.
[0010] In offshore electrolysis systems, special attention must be paid to preventing corrosion of the electrolysis plant, as the presence of salt water can lead to significantly higher corrosion rates, jeopardizing the long-term uninterrupted operation of an electrolysis plant. In principle, offshore electrolysis plants can be equipped with electrolyzers and housed within closed enclosures, called containers. This can provide a certain degree of protection for the electrolyzer from external environmental influences. However, for operational reasons, the electrolyzer must be cooled during normal operation in order to continuously dissipate the waste heat generated from the electrolysis process to the environment.In general, compared to onshore electrolysis plants, heat management in offshore electrolysis plants is particularly challenging, both with regard to the necessary cooling during normal operation and with maintaining a minimum temperature during extended periods of downtime. In the latter operating mode, sufficient freeze protection for the water-soaked electrolyzer cells must be ensured, particularly during periods of calm weather and when the wind turbine is shut down in the winter months. With regard to the cooling requirements during normal operation of offshore electrolysis plants, at least a closed container design, i.e. an enclosure to protect the electrolyzer, is established. This requires, on the one hand, to avoid overheating and failure of the electrolyzer and, on the other hand, damaging corrosion caused by exposure to maritime salt.Thus, in an offshore electrolysis plant, an interface and exchange between the electrolyzer and the environment is ultimately unavoidable in order to appropriately dissipate the heat flow of the process heat during normal operation and to enable safe operation.
[0011] To protect the electrolyzers from environmental influences, they require an enclosure such as a container, as explained above. PEM water electrolyzers must also be operated with demineralized, particularly high-purity, water. The internal temperature of the container must therefore not fall below approximately 5°C. Otherwise, the water-bearing components, which contain water, can freeze and paralyze the operation of the entire system. This would contradict the purpose of low-maintenance and self-sufficient operation of offshore electrolysis systems with wind turbines without grid connection.
[0012] 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.
[0013] 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.
[0014] Solutions that have already been partially 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.
[0015] This appears uneconomical with currently available battery technologies. Especially in cold ambient temperatures, the cold slows down the battery. This is because the electrolyte becomes more viscous and harder to penetrate. As a result, fewer ions reach the positive pole and the battery performance drops dramatically. The cold significantly slows down processes in the battery and the battery wears 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 the temperature during standstill operation of an offshore electrolysis system.
[0016] 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.
[0017] 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.
[0018] 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 has a combustion device, wherein a fuel reservoir is connected to the heat supply device, so that in standstill operation heat generated by means of the combustion device can be transferred to the electrolysis system, so that a temperature is maintained above a minimum temperature.
[0019] The object directed to a method for operating a corresponding offshore electrolysis system is achieved according to the invention by a method for operating an offshore electrolysis system, wherein during standstill operation heat is generated by means of the heat supply device and transferred to the electrolysis system, so that a temperature is maintained above a minimum temperature and freezing of water-bearing components of the electrolysis system is prevented.
[0020] The advantages and preferred embodiments of an offshore electrolysis system listed below can be analogously transferred to the method for operating the electrolysis system.
[0021] 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.
[0022] 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 wind turbine failure and no electrolysis power is available, is therefore of crucial importance.
[0023] 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 implements an integrated combustion-based heat maintenance concept in an offshore electrolysis system which is characterized by particularly high reliability and intrinsic fail-safe operation in critical weather conditions and operating situations. For this purpose, the heat supply system has a combustion device and a fuel reservoir. The fuel reservoir can advantageously interact and be integrated as an element of the heat supply device together with the electrolysis system, for example arranged on the platform.The combustion system is connected to the fuel reservoir via a fuel line and is designed, for example, as a combustion reactor, from which heat can be generated directly or indirectly and transferred to the water-bearing components of the electrolysis system that are susceptible to frost. This creates a virtually maintenance-free offshore electrolysis system that 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.The fuel reservoir provides a particularly simple, maintenance-free fuel supply as a reserve for a virtually unlimited period of time. The energy content of the fuel can be used thermally, directly or indirectly, as needed, by taking fuel from the fuel reservoir and converting it into energy. The combustion device can, for example, be designed such that the conversion can be carried out as a classic combustion process, i.e. based on oxidation of the fuel and reaction with oxygen in a burner with immediate heat development from a flame. However, it is also possible for the combustion device to be set up to carry out an electrochemical conversion reaction.In this sense, the combustion device as an element of the heat supply device is generally to be understood as a reactor or reaction chamber to which fuel is supplied and in which the fuel is converted, so that heat can ultimately be generated in the heat supply device to maintain the temperature and transferred to the electrolysis plant.
[0024] 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 as needed. These approaches also prove to be very disadvantageous from an environmental point of view and, moreover, expensive and maintenance-intensive. With the combustion-based heat supply system, on the other hand, temperature maintenance is ensured even over several days or even weeks during periods of darkness, with the heat transfer being adjustable to a required minimum temperature via the fuel conversion, which is maintained.Thus, the heat supply system is specifically adapted to a minimum heat emission and minimum heat consumption for maintaining the temperature to the requirements of the electrolysis plant in order to bridge long phases without production of electrolysis power by the wind turbine.
[0025] In a particularly preferred embodiment of the offshore electrolysis system, a product gas line branches off from the electrolysis plant, to which the fuel reservoir is connected, so that product gas generated from the electrolysis can be fed to the fuel reservoir during normal operation.
[0026] This results in a particularly advantageous provision of fuel and its introduction into the fuel reservoir for fuel storage. A characteristic feature is that the fuel or fuel precursors can be generated as product gas in the electrolysis process itself and removed from the electrolysis system. The fuel reservoir is filled with product gas as needed or continuously via the product gas line, or refilled after a period of downtime, depending on its design and capacity. This in-situ provision of product gas enables a self-sufficient offshore electrolysis system to be proposed, which ensures temperature maintenance even during downtime. This is of great economic importance, particularly for preferred island operation of the offshore electrolysis system.
[0027] In a particularly preferred embodiment of the offshore electrolysis system, the product gas line is connected to a pipeline, wherein the pipeline forms a fuel reservoir from which product gas can be withdrawn by means of a withdrawal line.
[0028] By connecting and using the pipeline, the pipeline itself can be used not only to transport the product gas to a take-off station on the mainland, but also as a fuel reservoir, thus offering advantageous dual use. The product gas line flows directly or indirectly into the pipeline, with a pressurised product gas being made available in the pipeline at an operating pressure. Via a withdrawal line on the pipeline, pressurised product gas can be withdrawn as required during standstill operation and fed to the combustion plant to generate heat. Due to the set and prevailing operating pressure in the pipeline, the product gas can flow automatically into the combustion plant without the need for additional conveying equipment such as pumps.
[0029] In a particularly preferred embodiment of the offshore electrolysis system, the product gas line is connected to a gas storage facility, the gas storage facility forming a fuel reservoir from which product gas can be withdrawn by means of a withdrawal line.
[0030] This provides a fuel reservoir in the form of a gas storage facility as an alternative or in addition to the pipeline. The gas storage facility can be loaded with pressurised product gas via the product gas line during normal operation and is designed as a compressed gas storage facility. In this way, a very large fuel supply of product gas can be stored at an operating pressure. Alternatively, a gas compressor can be switched on to achieve higher loading pressures and thus energy densities in the gas storage facility. Another advantage is that the gas storage facility can be operated independently of the pipeline and can, for example, be located on the platform and integrated into the electrolysis system. This ensures downtime even in the event of pipeline damage, pressure loss in the pipeline or maintenance work on the pipeline, and creates redundancy with the gas storage facility, in particular the compressed gas storage facility.
[0031] In a preferred embodiment of the offshore electrolysis system, the gas storage facility is provided on the platform and / or installed within the tower of the wind turbine. This proposes complete integration of the gas storage facility into the offshore electrolysis system. The gas storage facility can therefore be set up and operated in close proximity to the heat supply facility as the consumer and to the electrolysis plant as the producer of product gas. Loading the gas storage facility with product gas via the product gas line and withdrawing stored product gas via the withdrawal line and feeding it to the combustion facility can therefore be carried out compactly on the platform. The gas storage facility can be set up on the platform or attached beneath the platform and thus suspended.
[0032] Alternatively or in addition to being attached to the platform, the wind turbine tower can accommodate the gas storage unit.
[0033] In a particularly advantageous further embodiment of the offshore electrolysis system, the heat supply device is connected to and supplied by a gas storage device as a fuel reservoir, which is installed inside the tower of the wind turbine. In this way, the gas storage device can, for example, simply be formed or incorporated as a cavity within the tower of the wind turbine itself. The gas storage device is therefore preferably embedded deep below the water surface within the tower in order to utilize the most constant ambient temperature and thus pressure conditions in the gas container underwater. At the same time, the installation of a gas 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 the compressed gas storage device, since this space would otherwise remain unused.With this design, the gas storage facility requires no space 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. In an advantageous embodiment, the gas storage facility in the offshore electrolysis system comprises a pressure vessel into which product gas can be introduced and stored. The gas storage facility is preferably designed as a tube storage facility. Tube storage facilities are designed for high gas pressures and are easy to install and operate, for example, beneath the platform.
[0034] This provides a compact and easily installed gas storage system. Compressed product gas can be stored in steel or composite containers. Gaseous product gas supplied at high pressure, particularly hydrogen generated during normal operation (CGH2 = Compressed Hydrogen) from the electrolysis plant, can be stored, stored, and transported in cylindrical steel containers. Lighter, carbon-fiber-coated containers made of aluminum or plastic are also possible.
[0035] In a particularly preferred embodiment of the offshore electrolysis system, the combustion device comprises a fuel cell and a heating element, so that during standstill operation, power can be provided from the fuel cell to operate the heating element.
[0036] The fuel cell is connected to the gas storage unit via the extraction line to effect electrochemical conversion. Electrical energy is usually generated from chemical energy sources through combustion and the resulting hot gases are used to operate a heat engine with a downstream generator. The chemical energy is first converted into thermal energy through combustion and then into mechanical work, which is then used to generate electricity in the generator. A fuel cell, on the other hand, is capable of achieving this conversion without converting it into heat and power, making it potentially more efficient. Unlike an internal combustion engine, it converts chemical energy directly into electrical energy and is not subject to the inherently low efficiency of internal combustion engines.The theoretically achievable useful work is limited solely by the free enthalpy of the chemical reaction and can therefore be higher than when coupling a heat engine (Carnot efficiency) with a generator to generate electricity.
[0037] A fuel cell is a technical device that belongs to the electrical energy sources: It converts the chemical reaction energy of a continuously supplied fuel and an oxidizing agent into electrical energy. In the offshore electrolysis system, a fuel cell preferably refers to a hydrogen-oxygen fuel cell. The electrolysis of water produces not only oxygen but also hydrogen as a product gas in the electrolysis plant, which can be fed into the gas storage tank and used in a fuel cell process. The electricity from the fuel cell can be used to operate the heating element, so that during standstill operation, the temperature of the water-carrying systems of the electrolysis plant is maintained through heat transfer. Certain types of fuel cells, however, can use other fuels instead of hydrogen, in particular methanol, butane or natural gas.Along with accumulators and batteries, fuel cells are classified as galvanic cells. In principle, it is therefore also possible to store other fuels in the fuel reservoir. By integrating a hydrogen-oxygen fuel cell into the heat supply system, an electrolysis system based on water electrolysis is very advantageous, since the key reactant for the fuel cell process is generated as a product gas from the electrolysis.
[0038] In a further preferred embodiment of the offshore electrolysis system, power can be provided to the fuel cell to maintain a control device of the electrolysis plant.
[0039] Since the fuel cell provides electrical power, it can be used not only as heating power in the heat supply system but also for standby operation, in which the control devices of the electrolysis system and critical system components in particular continue to be supplied.
[0040] Standby mode (also called waiting mode) is the state of the electrolysis system in which the actual functional function is temporarily deactivated, but can be reactivated at any time without any preparation or extended waiting times. Maintaining the standby mode generally requires only a certain minimum power consumption, which is lower than during normal operation.
[0041] In a particularly preferred embodiment of the offshore electrolysis system, the combustion device has a gas burner, so that in standstill operation, product gas can be combusted in the gas burner and heat can be generated.
[0042] Compared to a fuel cell, equipping the combustion system with a gas burner is technically less demanding and just as reliable. This generates combustion heat directly, which can be transferred to a medium such as water. The gas burner extends into a boiler containing the circulating medium, particularly water, and is supplied with the gaseous fuel from the gas storage tank via a withdrawal line. The circulating medium absorbs the heat and is heated. The combustion heat from the gas burner is thus available to maintain the temperature.
[0043] 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 is designed to dissipate process heat from the electrolysis from the container during normal operation and to transfer the heat generated in the combustion device during standstill operation. This equipment enables particularly safe and environmentally friendly operation of an offshore electrolysis plant in container design with an electrolyzer arranged in the container, for example a PEM electrolyzer for hydrogen generation. At the same time, it is advantageously achieved that waste heat generated from the electrolysis process during normal operation can be used, if required, in an optional heat storage unit to additionally maintain the temperature during standstill operation and is then not simply released into the environment.During electrolysis, the process heat is typically dissipated from the container surrounding the electrolyzer, which protects it from weathering and salt ingress, to the environment. An optional heat storage unit would provide an additional heat reservoir.
[0044] In this case, the heat exchanger is advantageously configured to selectively dissipate the process heat from the electrolysis from the container. This allows the heat exchanger to support the cooling of the container during normal operation, and thus of the electrolyzer with its large number of 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 accordingly, so that targeted heat absorption and release, as well as, if necessary, further use in the heat supply system, is achieved on the secondary side of the heat exchanger.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 arranged in the container. With the closed cooling circuit, the heat absorption of process heat from the electrolysis at the system is achieved via the heat exchanger in the container. It is also possible to provide several heat exchangers, with a specially configured heat exchanger forming part of the heat supply system.
[0045] On the other hand, in standstill operation the heat exchanger is also designed to transfer the heat generated in the combustion device, so that if required a bidirectional heat exchange is possible, i.e. a dual use with cooling in normal operation and temperature maintenance in standstill operation with activation of the combustion device and generation of heat.
[0046] In a preferred embodiment of the offshore electrolysis system, the electrolysis plant comprises an electrolyzer for water electrolysis, which is based on a proton exchange membrane (PEM) electrolysis and / or on an alkaline electrolysis with hydrogen as the product gas.
[0047] This means that, if required, combinations of different electrolyzers for water electrolysis in the offshore electrolysis system are possible and can be adapted depending on the utilization concept. While alkaline electrolyzers can ideally be operated in a quasi-stationary mode at rated power, PEM electrolyzers are capable of partial load, especially at lower partial loads below 30% of rated power. Hydrogen and oxygen are produced as product gases in both technologies. In addition to being transported away as intended via a pipeline and further used onshore, some of the hydrogen is stored in the fuel reservoir and can be used in the combustion plant to maintain the temperature if required.
[0048] A further aspect of the invention relates to a method for operating a corresponding offshore electrolysis system. In this case, during standstill operation, heat is generated by the heat supply device through the combustion of a fuel in the combustion device, and the generated heat is transferred to the electrolysis system, thus maintaining the temperature above a minimum temperature and preventing freezing of water-bearing components of the electrolysis system.
[0049] The process can be carried out autonomously, i.e., without a grid connection to the offshore electrolysis system. Rather, the electrolysis system is ideally configured for isolated operation, ensuring temperature maintenance even during periods of low light, preventing freezing of water-bearing components.
[0050] In a preferred embodiment of the method, the temperature maintenance is initiated at an outside temperature of less than 5 °C by converting a fuel in the combustion device, whereby heat is generated and transferred to the water-carrying components of the electrolysis system, so that freezing protection is achieved.
[0051] A heat exchanger, or several heat exchangers if necessary, is used to couple or transfer the heat generated in the combustion system to the water-bearing components of the electrolysis plant that are at risk of freezing during standstill operation. A heat exchanger can be used simultaneously during normal operation to cool the electrolysis plant and dissipate the process heat from the electrolysis, i.e., it can also be used bidirectionally for cooling the electrolysis plant by selectively dissipating the process heat.
[0052] In a further preferred embodiment of the method, hydrogen is converted as fuel in a fuel cell and electricity is generated, wherein electricity is used to supply a control device of the electrolysis plant, whereby standby operation is maintained. Hydrogen is generated as product gas in the electrolysis plant and, if required, temporarily stored and made available for standby operation. Advantageously, electricity is generated directly in a combustion device with the fuel cell, which is used on the one hand as heating current for maintaining the temperature but also as system current for standby operation of electrical components of the electrolysis plant, in particular for the continued operation of the control device of the electrolysis plant. This enables rapid restart after the end of standby operation and immediate initiation of the start-up procedure for normal operation of the electrolysis system.
[0053] Embodiments, features, and / or advantages that relate to the offshore electrolysis system 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 shows the thermal coupling of a heat supply device to the electrolysis plant and its functioning in the offshore electrolysis system;
[0056] FIG 3 shows a heat supply device in which the combustion device has a fuel cell;
[0057] FIG 4 shows a heat supply device in which the combustion device has a gas burner;
[0058] FIG 5 shows a schematic side view of an offshore electrolysis system with a fuel reservoir. The same reference numerals have the same meaning in the figures.
[0059] FIG. 1 shows an offshore electrolysis system 100. The offshore electrolysis system 100 comprises an electrolysis plant 5 and a wind turbine 1, which has a tower 19 and a turbine rotor, as shown in the upper right part of FIG. 1. In the lower region of the tower 19, a platform 3 is attached above sea level 25 (see FIG. 5), which is specially designed and configured to accommodate various plant components for the intended operation of the offshore electrolysis system 100. These plant components are shown in an enlarged illustration in the lower part of FIG. 1:
[0060] An electrolysis plant 5 is set up on platform 3 and is systemically connected to the wind turbine 1 to form the offshore electrolysis system 100. For this purpose, containers 9 are set up on platform 3, in which electrolysis elements (not shown in detail) such as individual electrolyzers are accommodated, so that particularly sensitive functional components of the electrolysis plant 5 are protected from the effects of the weather. Some of the containers 9 set up on platform 3 comprise control devices 27 or so-called "balance-of-plant" elements and accommodate them protectively. These are selected containers 9 that are usually reserved for the sole accommodation and operation of these control devices 27 and, if applicable, other auxiliary systems of the electrolysis plant 5. In contrast, the electrolyzers for the electrochemical material conversion are arranged in containers 9 provided specifically for this purpose.Further components or system parts accommodated in the containers 9 can also be storage containers for electrolyte solution for operating the electrolyzers, or in particular demineralized water or potassium hydroxide solution in the case of PEM or optionally alkaline water electrolysis of the electrolyzers, or the like. 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 directly, which is set up to produce preferably green hydrogen from water electrolysis. The offshore electrolysis system 100 is therefore set up for grid-independent island operation and equipped for self-sufficient use in regions further from the coast. The wind turbine 1 is therefore an offshore wind turbine.Deviating from the illustrations in FIGS. 1 and 5, the means presented according to the invention for improved heat supply and temperature maintenance of 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 at the same time 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 1 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, especially during a prolonged period of darkness with the associated acute 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. It is thus possible - as shown by way of example in FIG. 1 - for the heat supply device 7 to be accommodated in a selected container 9 of the offshore electrolysis system 100 or for a container 9 to have certain system components or functional elements of the heat supply device 7. The heat supply device 7 is coupled to the electrolysis system 5 and designed in such a way that, during standstill operation, heat can be transferred to the electrolysis system 5 by means of the heat supply device 7, so that the temperature of the water-carrying systems is maintained above a minimum temperature.
[0063] The thermal coupling of the heat supply device 7 to the electrolysis plant 5 and its mode of operation in the offshore electrolysis system 100 is shown in more detail in FIG. 2. The heat supply device 7 has a combustion device 13 which is supplied with fuel from a fuel reservoir 15 via a withdrawal line 21. The fuel reservoir 15 is connected to the electrolysis storage area 5 via a product gas line 17. During normal operation of the electrolysis plant 5, hydrogen H2 is produced as product gas 23. The hydrogen H2 is produced from water, for example, by means of proton exchange membrane (PEM) electrolysis or alkaline electrolysis. The electrolysis plant 5 produces hydrogen H2 and oxygen O2 from the supplied water using electrical energy. This process takes place in an electrolysis stack composed of several electrolysis cells.Water is introduced as a reactant into the electrolysis stack which is under DC voltage, and after passing through the electrolysis cells two fluid streams consisting of water and gas bubbles (O2 or H2) emerge, the two product gases being separated and discharged via a respective product gas line 17. During normal operation of the electrolysis plant 5 the fuel reservoir 15 is charged with hydrogen H2 so that hydrogen H2 is made available as fuel and is kept in stock for any necessary downtime. The fuel reservoir can be designed as a gas storage device 39, for example as a tubular storage device which is charged with hydrogen H2 from the electrolysis plant 5, if necessary using recompression under a high storage pressure. The gas storage device 39 can therefore be designed and constructed in a simple manner as an integral component of the offshore electrolysis system 100 and can be used for example as a fuel storage device.attached to its supporting structure or arranged in a container 9 . The combustion device 13 is thermally coupled to the electrolysis system 5 via a heat exchanger 11 . A flow line 47a and a return line 47b are provided here, which effect the thermal coupling and the heat transfer to the electrolysis system to maintain its temperature via the heat exchanger 11 . The heat exchanger 11 is fed on the primary side with heat from the combustion, wherein the heat generated in the combustion device 13 during standstill operation is first transferred to a suitable heat exchange medium, e.g. circulating water, in a boiler. On the secondary side, the circulating process water from the electrolysis can use the heat exchanger 11 to absorb the heat generated in the combustion device 13 to maintain the minimum temperature. This reliably prevents water-carrying components of the electrolysis 5 from freezing.Standstill operation is initiated when electricity production from the wind turbine 1 ceases, e.g. due to a period of darkness, and an outside temperature of less than 5°C, by converting the hydrogen H2 stored in the fuel reservoir in the combustion device 13. The combustion device 13 can be designed, for example, as a fired boiler or as an electrically heated boiler. Thus, electrically operated hot water heaters or fuel gas-operated hot water heaters, which are coupled to the heat exchanger 11 on the primary side, can be used to generate heat.
[0064] These possibilities are outlined and explained below with reference to FIGS. 3 and 4. FIG. 3 shows a heat supply device 7 in which the combustion device 13 has a fuel cell 41 and a heating element 43. The fuel cell 41 converts hydrogen H2 and oxygen O2 as reactants. Hydrogen H2 is withdrawn from the fuel reservoir 15 via a withdrawal line 21 and supplied to the cathode side. Correspondingly, pure oxygen O2 from a provided reservoir or from the ambient air - after gas cleaning - can be supplied to the anode side of the fuel cell 41 via a withdrawal line 21. The fuel cell 41 provides electrical power for heating in the heat supply device 7. During standstill operation, the fuel cell 41 supplies the heating element 43 with electrical current, so that resistance heating is effected.The ohmic heat generated can, as shown in FIG. 2, heat a heat exchanger medium on the primary side and be fed to a heat exchanger 11. However, it is also possible for the heating element 43 to be connected directly into the process water circuit of the electrolysis plant 5 in terms of heat switching technology, for example by arranging the heating element 43 inside the heat exchanger 11 or by protruding into it with the heating coils. In this way, no separate heat exchanger medium is required, since there is no need for a primary circuit. Temperature is maintained equally via the flow line 47a and the return line 47b of the heat exchanger 11. At the same time, the option is created of supplying electrical systems of the electrolysis plant 5, such as a control device 27, with electrical power from the fuel cell 41, so that standby operation is maintained.
[0065] In contrast, FIG 4 shows a heat supply device 7 in which the combustion device 13 has a gas burner 45 which is suitable for the combustion of hydrogen H2. In this way, too, the product gas 23 from the water electrolysis from the gas storage 39 can be advantageously used. The product gas 23 is generated during normal operation of the electrolysis plant 5 and stored in the gas storage 39, where it is made available. The gas burner 45 is supplied with hydrogen H2 as product gas 23 via the extraction line 21, and the hydrogen H2 is burned with oxygen O2 or combustion air L stored from the electrolysis. The released heat of combustion is transferred to the heat exchange medium in the hydrogen-fired boiler via water-carrying pipes and is fed to the heat exchanger 11 on the primary side and is exchanged with the process water from the electrolysis to be heated.Heat transfer is achieved by circulating or recirculating the process water via the flow line 47a and the return line 47b. For this purpose, circulation pumps are provided, which are powered by a small-sized battery storage unit that can be recharged during normal operation.
[0066] In both embodiments of the heat supply device 7 shown in FIGS. 3 and 4, the heat exchanger 11 can additionally be equipped for bidirectional operation, i.e. in normal operation also for discharging the process heat from the electrolysis process out of the container 9 and in standstill operation for maintaining the temperature by transferring heat generated in the combustion device 13 to water-carrying components and systems of the electrolysis plant 5. The process heat can then be dissipated, for example, via a separate coolant circuit (not shown in more detail), into which the heat exchanger 11 is additionally connected. This coolant circuit is activated for cooling purposes in normal operation. In standstill operation it is deactivated, wherein in standstill operation the heat generated in the combustion device 13 is transferred, as described.In this way, the offshore electrolysis system 100 with the heat supply device 13 is equipped for switching from a cooling mode to a heating mode.
[0067] FIG 5 shows a schematic side view of the offshore electrolysis system 100 with a wind turbine 1 and with a platform 3 and with an electrolysis plant 5 arranged on the platform 3. The platform is attached to the tower 19 above sea level 25 in an above-water area 29. The electrolysis plant 5 has a number of containers 9, each with at least one electrolyzer arranged therein. The offshore electrolysis system 100 shown here is very advantageously equipped with an integrated combustion-based heat supply device 7. The heat supply device 7 has a fuel reservoir 15 connected to the heat supply device 7, so that hydrogen H2 obtained from the electrolysis can be stored in the fuel reservoir 15 and used as fuel for heat generation as needed.The heat supply system 7 is arranged on the platform 3 and can also be housed in one of the containers 9 together with equipment of the electrolysis plant 5, such as an electrolyzer. The tower 19 extends from the above-water area 29 into an underwater area 31 and is firmly anchored in the seabed 35 by means of a foundation 33.
[0068] The fuel reservoir 15 is designed as a gas storage device 39, so that the product gas 23 - in this case hydrogen H2 - can be stored in the gas storage device 39 under a storage pressure. A gas storage device 39 is advantageously designed with pressure-resistant containers, for example formed as a number of hydrogen tube storage devices. The gas storage device 39 is suspended below the platform 3, so that no installation space is required on the platform. Furthermore, a cavity is formed within the tower 19 of the wind turbine 1 - in this case incorporated deep below sea level 25 within the foundation 33 - and has a corresponding storage volume for the hydrogen H2. A pressure-resistant and hydrogen-tight gas storage device 39 is introduced into this cavity.Thus, during normal operation of the offshore electrolysis system 100, hydrogen H2 can be stored under pressure as product gas 23 from the electrolysis in the gas storage 39 and the gas storage 39 can be loaded. The storage in the gas storage 39 takes place via the product gas line 17 or a corresponding branch line of the product gas line 17. At the same time, a connection unit to a pipeline 37 for transporting product gas 23 is attached to the platform 3, which is connected to the product gas line 17 or supplied via it. The pipeline 37 leads away from the platform 3, immerses in the underwater area 31 and is led over the seabed 35 to the mainland. On the mainland, the product gas 23 can be taken over and further processed. During normal operation of the electrolysis system 100, the product gas 23 is therefore 23 - in this case hydrogen H2.
[0069] - can be fed into the pipeline 37 under pipeline pressure and transported to the mainland. The product gas line 17 is connected to the pipeline 37, the pipeline 37 thus fulfilling the function of a gas storage facility 39. Thus, the pipeline 37 also provides a fuel reservoir 15 from which product gas 23 can be withdrawn as required by means of the withdrawal line 21 on the connection unit. The withdrawal of hydrogen H2 from the gas storage facility 39 or from the pipeline 37 takes place via a withdrawal line 21 which supplies the combustion-based heat supply device 7 when the electrolysis system is at a standstill, so that the heat generated can be transferred to the electrolysis plant 5, so that the temperature is maintained above a minimum temperature and freeze protection is effected.
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 has a combustion device (13), wherein a fuel reservoir (15) is connected to the heat supply device (7) so that heat generated by means of the combustion device (13) in standstill operation can be transferred to the electrolysis system (5), so that a temperature maintenance above a minimum temperature is effected.
2. Offshore electrolysis system (100) according to claim 1, wherein a product gas line (17) branches off from the electrolysis plant (5), to which line the fuel reservoir (15) is connected, so that product gas (23) generated from the electrolysis can be fed to the fuel reservoir (15) during normal operation.
3. Offshore electrolysis system (100) according to claim 1 or 2, wherein the product gas line (17) is connected to a pipeline (37), the pipeline (37) forming a fuel reservoir (15) from which product gas (23) can be withdrawn by means of a withdrawal line (21).
4. Offshore electrolysis system (100) according to one of the preceding claims, wherein the product gas line (17) is connected to a gas storage (39), wherein the gas storage (39) forms a fuel reservoir (15) from which product gas can be removed by means of a removal line (21).
5. Offshore electrolysis system (100) according to one of the preceding claims, wherein the gas storage (39) is arranged on the plate- form (3) and / or is incorporated within the tower (19) of the wind turbine (1).
6. Offshore electrolysis system (100) according to claim 5, wherein the gas storage (39) is designed as a tube storage.
7. Offshore electrolysis system (100) according to one of the preceding claims, wherein the combustion device (13) comprises a fuel cell (41) and a heating element (43), so that in standstill operation, current for operating the heating element (43) can be provided by the fuel cell (41).
8. Offshore electrolysis system (100) according to claim 7, wherein power can be provided by the fuel cell (41) to maintain a control device (27) of the electrolysis plant (5).
9. Offshore electrolysis system (100) according to one of the preceding claims, wherein the combustion device (13) has a gas burner (45) so that in standstill operation, product gas (23) can be combusted in the gas burner (45) and heat can be generated.
10. Offshore electrolysis system (100) according to one of the preceding claims, in which the electrolysis plant (5) has an electrolyzer arranged in a container (9) and a heat exchanger (11) which is designed in normal operation for the dissipation of process heat from the electrolysis from the container (9) and in standstill operation for the transfer of the heat generated in the combustion device (13).
11. Offshore electrolysis system (100) according to any one of the preceding claims, wherein the electrolysis plant (5) comprises an electrolyzer for water electrolysis based on a Proton Exchange Membrane (PEM) electrolysis or on a alkaline electrolysis and with hydrogen (H2) as product gas.
12. Procedure for operating an offshore electrolysis system (100) according to one of the preceding claims, wherein, in a standstill operation, heat is generated by means of the heat supply device (7) and transferred to the electrolysis system (5), so that a 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 by converting a fuel in the combustion device (13), whereby heat is generated and transferred to the water-carrying components of the electrolysis system (5), so that freezing protection is effected.
14. The method according to claim 13, wherein hydrogen is converted as fuel in a fuel cell (41) and electricity is generated, wherein electricity is used to supply a control device (27) of the electrolysis plant (5), wherein a standby operation is maintained.