Electrolysis system

Abstract

The invention relates to an electrolysis system (10) comprising an electrolysis device (1, 1A, 1B), a current supply source (3) having a DC voltage output (7), and a central supply line (5), the central supply line (5) being connected to the DC voltage output (7) of the current supply source (3) such that a DC current can be fed into the central supply line (5), according to the invention, a central direct-current high-power cable designed for the direct-current voltage is provided, the electrolysis device (1) is connected to the direct-current high-power cable via a central power supply line (5), at least the current supply source (3) and the direct-current high-power cable being a network (17) insulated from the earth. The invention also relates to a use of an insulated DC network (17) in an electrolysis system (1).

Description

Technical Field

[0001] The invention relates to an electrolysis system comprising at least one electrolysis device, a current supply source having a DC voltage output and a central power supply line. The invention also relates to a use. Background Art

[0002] In the electrolysis process, the redox reaction associated with the material conversion can be forced to occur by applying an electric current to flow through a suitable electrolyzer unit. The device for this purpose is called an electrolyzer and can be used to produce important raw materials for the chemical industry. In many cases, the anode half space and the cathode half space are separated by a diaphragm (or membrane) that allows conduction (ion exchange and / or proton exchange) but prevents material exchange. If a liquid electrolyte that changes or consumes due to material conversion is used in an electrolyzer, the liquid electrolyte can be continuously updated during the process by corresponding input and output pipelines. Due to the limitation of current density, for a given electrolyzer unit, there are usually strict restrictions on material conversion rate. Therefore, in order to use on a large scale, it is necessary to increase the active electrolyzer unit area to improve the material conversion rate. This can be achieved by making the electrolyzer unit larger or by running multiple smaller electrolyzer units simultaneously. A technically meaningful and frequently used method is to arrange multiple (identical) electrolyzer units into an electrolytic stack. In this case, the electrical connection of the electrolysis cells of the electrolysis stack is a series connection, i.e. the anode of electrolysis cell N is electrically conductively connected to the cathode of electrolysis cell N+1, and the cathode of electrolysis cell N is electrically conductively connected to the anode of electrolysis cell N-1. The series connection also multiplies the low electrolysis cell voltage of a few volts to, for example, several hundred volts.

[0003] In contrast, the hydraulic interconnections of the electrolyzer units of the electrolysis stack for supplying fresh electrolyte are connected in parallel. Due to the hydraulic interconnection of the electrolyzer units to form the electrolysis stack, additional and undesirable conductive connections are generated between all the electrolyzer units. During the operation of the electrolysis stack of the electrolyzer units, i.e. during the application of the voltage or current from the first electrolyzer unit to the last electrolyzer unit, the operating current flows through all the electrolyzer units. However, undesirable so-called stray currents additionally flow on the various parallel current paths. This stray current leads to excessive increase in local current density near the input and output pipelines of the electrolyte, especially at the first electrolyzer unit and the last electrolyzer unit of the electrolysis stack. This may lead to premature aging and destruction of the membrane and cause failure of the entire electrolysis stack.

[0004] Document DE 10 2020 206 341 A1 describes a method for protecting an electrolysis stack comprising a plurality of electrolysis cell stacks or modules from corrosion and a corresponding electrolysis stack. The method is used in particular to reliably protect CO during shutdown of the electrolysis stack or for the purpose of transporting the electrolysis stack.2 Electrolysis to prevent corrosion.

[0005] The electrochemical decomposition of water as a starting material on an industrial scale to produce hydrogen as a product is of great economic interest and is being developed vigorously. Nowadays, hydrogen is produced from water, for example, by means of proton exchange membrane (PEM) electrolysis or anion exchange membrane electrolysis or alkaline electrolysis. Electrolysis equipment uses electrical energy to produce hydrogen and oxygen from supplied water. However, electrolysis equipment based on alkaline electrolysis also has a wide range of applications.

[0006] Currently, it is considered to use the excess energy generated by renewable energy sources during periods of abundant sunlight and wind, i.e., above-average solar or wind power generation, to produce valuable substances. One valuable substance can be hydrogen produced by corresponding devices for the electrolysis of water. Based on hydrogen, for example, so-called renewable energy gas (Erneuerbare Energy Gas), also called EE gas, can be produced. EE gas is a combustible gas obtained with the aid of electrical energy generated by renewable energy sources.

[0007] One source of renewable energy is the increasing use of wind power. In particular, large electrical powers can be achieved using so-called offshore wind power plants close to the shore. However, the long distances to the consumer must be overcome, which is challenging. The energy should therefore be transmitted to the consumer as loss-free as possible. Hydrogen is very suitable as a transmission medium and energy carrier. For example, hydrogen can be transported in gaseous form via pipelines. A positive secondary aspect here is that the pipeline that conducts the hydrogen can also serve as an energy storage device, since the pressure inside can be varied within a certain range.

[0008] Based on this consideration, it is of particular economic interest to produce hydrogen directly at the energy source, i.e. self-sufficiently and independently of the public grid. For this purpose, it is proposed to install the electrolysis system on an offshore platform in the sea area in the immediate vicinity of the offshore wind power plant or in the vicinity of the offshore wind power plant, to use the generated wind current to directly supply electricity via the wind power plant, and to operate the electrolysis system in a so-called independent network that is independent of the public grid.

[0009] For the mainland, the following solution has also been proposed, that is, the current generated by the onshore wind power plant or photovoltaic plant is at least partially used directly for the production of hydrogen by direct connection to the electrolysis plant and feeding into the electrolysis plant. In all these self-sufficient applications, the electrolysis plant is part of a so-called independent network. Therefore, in this electrolysis system, the electrolysis current is usually not obtained from the public power grid, but is directly provided in the network by the wind power plant or photovoltaic plant and fed into the electrolyzer of the electrolysis plant via the power supply line. In this case, the electrical energy generated by the wind power plant or photovoltaic plant can also be temporarily stored in a battery, for example.

[0010] Compared to the network-guided operation mentioned above, independent network operation presents special challenges and problems for the electrolysis system with regard to the electrical connection and interconnection of the electrolysis equipment with the corresponding renewable power generation equipment (whether a wind power equipment or a photovoltaic equipment), in particular to ensure the safe and, above all, trouble-free operation of the electrolysis equipment in the equipment network formed directly with the renewable power generation equipment.

[0011] In this case, it is particularly important to consider that, for electrolysis systems that form an integrated and self-sufficient independent network, the hydrogen electrolysis cells in the electrolysis equipment connected therein generate corresponding stray currents from the module to the earth. These stray currents flow through the process water pipelines and cause undesirable corrosion damage at the process water pipelines, even with sufficient insulation distances. In this case, metal ions are released into the process water, which leads to irreversible damage or accelerated aging, especially at the (PEM) membrane. In the application of PEM electrolysis and alkaline electrolysis systems, these stray currents also reduce the efficiency. Therefore, the corrosive effects of stray currents should be reduced as much as possible.

[0012] For example, the stray current can be reduced by increasing the resistance of the electrolyte input and output lines. Previous solutions proposed to extend the input and output lines, thereby increasing the resistance while keeping the cross-sectional area constant. However, extending the lines disadvantageously leads to an increase in the flow resistance and an increase in the material demand for manufacturing and corresponding additional construction costs. This is particularly problematic in remote installation areas of electrolytic devices that require or wish to operate an independent network, i.e., where it is technically or economically impossible or only with considerable effort to connect the electrolytic device to the public grid.

[0013] Therefore, there is an increasing need to identify inexpensive methods to address the corrosion problem in order to improve the service life of electrolysis systems in the context of stand-alone networks. Summary of the invention

[0014] The object of the present invention is therefore to provide an electrolysis system which is designed for off-grid operation, in particular in combination with a wind power plant or with a solar power plant, and which is less susceptible to corrosion caused by stray currents.

[0015] According to the invention, the object of the invention is achieved by an electrolysis system, which includes an electrolysis device, a current supply source with a DC voltage output and a central power supply line, wherein the central power supply line is connected to the DC voltage output of the current supply source so that DC current can be fed into the central power supply line, wherein a central DC high-power cable designed for DC voltage is provided, and the electrolysis device is connected to the DC high-power cable via the central power supply line, wherein the current supply source and the DC high-power cable are components of a network insulated from the ground.

[0016] The invention is based on the knowledge that in electrolysis systems connected to and supplied by a common alternating current network, electrical isolation is achieved using a transformer and that the high-current electrolysis current circuit can therefore already be operated as an isolated network or can be grounded at a point on the module. The process technology of the electrolysis plant does not provide a well-conducting return conductor for stray currents, or rather does not form a ground loop, and this current can be reduced.

[0017] However, if the electrolysis is to be operated in an independent network (e.g., including electrolysis systems of offshore wind power plants), or onshore in remote areas or as a solar power plant, there is no alternating voltage network available or nearby for electrical decoupling by a transformer. In these settings of electrolysis plants, it is not economical to provide an alternating voltage intermediate circuit specifically for the transformer. This would lead to high additional production and operating costs. Therefore, this design and the dependence on the public power grid are not conducive to the operation of the electrolysis system in an independent network.

[0018] In order to reduce connection and transmission problems and corrosion problems as effectively and first of all safely and reliably as possible for an independent network of the electrolysis system, that is, for an operation that is not dependent on the network, and in addition, the invention proposes to connect or integrate the electrolysis device with a non-grounded central DC network specially provided for this purpose. In this case, the central DC high-power cable and all operating components connected thereto form a so-called IT network (IT: isoléterre (insulator)). The operating components of the IT network that form the electrolysis system, such as the generator of the current generator or current supply source, the central power supply line and the electrolysis device, are not grounded here. Therefore, the current supply source that provides the operating voltage is insulated from the earth, that is, it is usually open-circuited or designed by a symmetrical and high-resistance grounding part of the electrolysis system. Therefore, in normal operation, there is no low-resistance connection between the active part of the IT network and the earth or the protective conductor. In this case, the central DC high-power cable is part of the entire IT network, wherein the IT network also includes the operating components of the electrolysis system connected thereto, such as the current supply source with a DC voltage output and the electrolysis device.

[0019] The solution of the invention is therefore to design and operate the entire supply cable including the provided DC high-power cable and the electrolysis plant as an IT network, starting from the generator, in order to avoid corrosive stray currents in the electrolysis. Compared to network-guided operation, an AC intermediate circuit for electrical decoupling can be advantageously omitted. Thus, with the proposed electrolysis system, an insulated DC high-power cable is realized in the electrolysis system, so that independent network operation can be achieved when the electrolysis plant with renewable energy devices (EE devices), such as wind energy devices or photovoltaic devices, is connected to a central DC power supply line. Since the electrical decoupling in the central high-power cable is omitted, the solution is significantly more compact, simpler and cheaper. In this case, all conductors of the high-power cable are at an uncertain potential with respect to the earth.

[0020] The DC network formed by the insulated high-power cables of the electrolysis system provides a predetermined high voltage and DC power on the central power supply line and serves as a transmission and distribution network for DC current. The required transmission power is transmitted from the current supply source to the electrolysis equipment via the central and ungrounded DC network, thereby providing a DC electrolysis current. In this case, the high voltage of the DC network can be flexibly selected and set to the required DC voltage connection value. At the same time, due to the avoidance, or rather reduction, of stray currents, in particular due to the process technology of the electrolysis equipment, the corrosion effects are reduced, and thus the maintenance and repair costs are reduced. The electrolysis system of the invention further promotes an increase in the service life.

[0021] In a particularly preferred embodiment of the electrolysis system, the electrolysis system has an insulation monitor, making it possible to monitor the minimum insulation resistance of the insulated network relative to the earth and to detect insulation faults.

[0022] The insulation resistance preferably has a high resistance value, that is to say the high-resistance ground is designed for a predefined minimum insulation resistance, which must not be fallen below during operation. For this purpose, an insulation monitor is provided as a protective element and can be used to monitor or display the insulation resistance so that an alarm signal can be issued and measures can be taken.

[0023] The use of an isolated DC network makes it very advantageous to use an insulation monitor as a protective element. In the case of a simple grounding, the electrolysis system can continue to operate, since there is no direct danger, in particular to the electrolyzers of the electrolysis system, which increases availability.

[0024] Insulation monitors or insulation monitoring devices monitor the insulation state of IT networks, for example local low-voltage networks without a star point grounded to the operating ground. They issue a signal if a minimum insulation resistance is undershot. In the past, only current or voltage measurements relative to the earth (symmetry deviation) were performed for this purpose, but nowadays symmetrical insulation faults also need to be reliably detected, which additionally requires a test current. In the event of a fault, if the insulation fault current is exceeded, only a warning can be issued or the relevant network feeder can also be disconnected.

[0025] In an advantageous embodiment, the insulation monitor is fault-tolerant, i.e. a simple fault (single-pole grounding) does not lead to a failure of the current supply in the electrolysis system or of the associated feeder. In this way, the current supply source, or more precisely its feeder, in the isolated IT DC voltage network is effectively protected.

[0026] Therefore, the first grounding is harmless (non-hazardous) in IT networks, because the current caused only by the line capacity and insulation resistance of the electrolysis system and its operating facilities is small. If the spatial extent of the electrolysis system, or more precisely the IT network formed by it, is small, the leakage current in the event of a fault is so small that it is also harmless.

[0027] Advantageously, the insulation monitor detects grounding, asymmetry and too low insulation resistance of the IT network. To this end, the insulation monitor measures the symmetry of the voltage of the two network poles relative to the earth. If the leakage current of the two network poles is the same, the symmetry is maintained.

[0028] In operation, a high-voltage direct current is provided at the connection of the central power supply line, which has a predetermined high voltage that is significantly higher than the usual network voltage. Thus, in an IT network, the electrolyzers of an electrolysis plant connected to a central DC bus line can be centrally supplied with electricity via the direct current network.

[0029] Preferably, the power supply source therefore has a step-up converter having a DC voltage output, by means of which a predetermined high voltage can be provided for a central power supply line in an IT network.

[0030] A boost converter, also called a step-up converter or a step-up regulator, is a form of a DC voltage converter in the field of electronics. The value of the output voltage is always greater than the value of the input voltage. This allows the DC voltage level at the DC voltage output to be flexibly adjusted to match a predetermined high voltage on a central DC power supply line. The use of a step-up converter may be advantageous, in particular when combined with a photovoltaic generator as a current supply source, in which the photovoltaic DC voltage is stepped up, thereby providing a predetermined high voltage at the DC voltage output for feeding into a central power supply line.

[0031] The step-up converter is preferably a controllable step-up converter having a DC voltage output, via which a predetermined high voltage can be provided on a central power supply line with an output voltage of more than 1.5 kV, in particular more than 10 kV, in an IT network.

[0032] Particularly preferably, the adjustable step-up converter is designed to be able to provide a DC voltage at a high voltage level of 10 kV to 110 kV, preferably 30 kV to 60 kV.

[0033] In a preferred embodiment of the electrolysis system, the power supply source has a wind power installation as a power generator, to which a rectifier with a DC voltage output is connected, wherein the DC voltage output is designed for the high voltage in a central DC high-power cable.

[0034] In this way, in the electrolysis system, the electrolysis equipment is connected to the wind power equipment or photovoltaic equipment, more precisely, the direct current connection, and the electrolysis equipment is powered by the wind power equipment or photovoltaic equipment through the central direct current power supply line designed as the IT network, wherein a safe and reliable independent network operation is particularly advantageously achieved. If the electrolysis system is operated in an independent network, it is not connected to the public power grid. Therefore, for the design and operation of the electrical components of the IT network in direct current operation, the network frequency of 50Hz to 60Hz of the public power grid is not important. In particular, the cost of components and conversion losses, such as the cost of transformers, or the cost of required inversion, transmission or re-rectification are saved. This can bring lower cost expenses in the future while maintaining the flexibility of operation, or, for example, the flexibility in designing and selecting connecting components in the direct current network. The operation independent of the network frequency is realized by using a central power supply line designed as a direct current bus, which is part of an insulated direct current high-power cable. According to the design of the direct current high-power cable as an IT network, the direct current voltage output of the rectifier may already be able to directly provide high voltage. However, it is also possible to connect a controllable step-up converter downstream of a rectifier, the DC voltage output of which provides a predetermined high voltage at the DC high-power line.

[0035] Thus, with an insulated DC network, it is advantageously possible to overcome, if necessary, large distances and line lengths between the current generator and the electrolysis plant in an inexpensive manner, without having to carry out a further AC conversion for step-up and step-down conversions, which can only be achieved with the aid of multiple and expensive transformers. However, for IT networks, smaller distances and compact electrolysis systems are more advantageous in terms of ensuring better symmetry of the network poles and lower voltages due to the smaller spatial distances of the protective earthing of the housings of the operating facilities (e.g. the tower of a wind power plant and the process technology units of an electrolysis plant). In particular, all components that can conduct electricity but do not belong to the operating circuit are grounded individually or jointly, or these components can be connected jointly to the protective earthing of the system if necessary. If the network has a small spatial extent, the leakage current in the event of a fault is so small that it is harmless, so that generally a small spatial extent and a compact design of the DC high-power cables are preferred.

[0036] Preferably, in the electrolysis system, the electrolysis device is arranged at the bottom of the tower of the wind power plant and is connected directly to the central power supply line for direct current as an operating facility in the IT network. In particular for onshore wind power plants that may be very remote, it is advantageous to connect the electrolysis device in the electrolysis system in the vicinity of the wind power plant to a central, insulated DC bus line of an insulated DC high-power cable. If a DC / DC converter is then preferably used, a high DC voltage is applied to the power supply line, so that the amount of material, in particular copper and aluminum, is reduced, and the manufacturing costs are correspondingly reduced.

[0037] Preferably, in the electrolysis system, the electrolysis apparatus has a plurality of electrolysis modules connected in series to form a module series.

[0038] Here, in an advantageous embodiment, each electrolysis module can be physically and functionally a structural unit in which a plurality of electrolysis cells are stacked. By means of the modular concept of the electrolysis device, a module series can be easily expanded to an electrolysis stack comprising a plurality of modules, for example a module series of 5 to 10 modules.

[0039] Preferably, a connectable, electrically conductive ground connection is provided in the module series, which ground connection has a predetermined ground resistance and by means of which the stray currents can be controlled.

[0040] A protective ground is thus provided on the housing, which is arranged on the housing of the module, for example on the last module of the module series, facing away from the central insulated DC power supply line as viewed from the electrical connection. The protective ground can additionally be a grounded structure on the housing of the power supply source, for example on the tower of a wind power plant. Thus, a two-point protective ground is optionally also achieved in the electrolysis system, which is advantageous in combination with an insulation monitor. Furthermore, discharge can be carried out in a simple manner via the accessible, electrically conductive ground connection, for example for maintenance purposes on insulated networks, in particular DC high-power cables.

[0041] Residual stray currents and ground loops are thus avoided. Preferably, the protective ground connection is provided on the last module of the module series, wherein the resistance defined for the ground connection is adjustable. This facilitates the adjustment and minimization of harmful stray currents occurring on the process technology unit. However, the corresponding tapping of the protective ground connection on the modules of the module series can be flexibly adjusted to the DC voltage and its polarity at the DC voltage output depending on the DC voltage.

[0042] If, for example, DC voltages of +250 V and −250 V are output at two poles as the DC voltage output of the rectifier used, grounding is advantageously achieved via a protective ground line in the middle of the electrolyser series, where the voltage is almost 0 V anyway.

[0043] However, if a DC voltage of +500 V and 0 V is output at two poles as the DC voltage output of the rectifier used, grounding is preferably achieved at the last module via a protective ground line, since the voltage to the earth is nearly 0 V there.

[0044] In conjunction with the IT network design of all operating facilities, the problem of stray currents that still exist due to the hydraulic interconnection of the electrolyzer units of the electrolysis stack for supplying fresh electrolyte is additionally dealt with. Since the electrolyzer units are hydraulically interconnected to form the electrolysis stack, additional and undesirable conductive connections and stray currents are created between all electrolyzer units, which can lead to corrosive effects.

[0045] In a particularly preferred embodiment of the electrolysis system, the electrolysis system comprises at least two electrolysis devices which are connected in parallel with one another with respect to a central power supply line, wherein the electrolysis devices are connected to the central power supply line via corresponding connecting lines.

[0046] Thus, the insulated DC network is easy to expand, wherein further electrolysis devices can be connected to the central DC power supply line and powered. Optionally, it is also possible to have two or more central power supply lines in the electrolysis system, depending on the required transmission power of the DC high-power cable, to which the corresponding electrolysis devices with the corresponding module series are connected. All module series are then optionally grounded, in particular to a common protective ground. The electrolysis device has at least one module series, for example, two module series can be connected in parallel in the electrolysis device. However, the electrolysis device can also have only one module series, which has a plurality of electrolysis modules electrically connected in succession.

[0047] In the electrolysis system, the electrolysis apparatuses are preferably connected in parallel with one another relative to a central power supply line, wherein the electrolysis apparatuses are connected to the central power supply line via corresponding connecting lines.

[0048] This makes use of the advantages of a DC bus concept with a central and isolated DC current supply line, which allows and provides corresponding, independent connection lines for the electrolysis devices. In an electrolysis system, the central DC supply network can be expanded flexibly as required and can be expanded by further electrolysis devices, and it is possible to adjust the feed-in power of the power supply source fed into the isolated DC network relative to the power draw provided for the operation of the electrolysis cells.

[0049] In a preferred embodiment of the electrolysis system, the power supply source has a photovoltaic system as power generator, the DC voltage output of which is designed for high voltage, wherein the DC voltage output is connected to a central power supply line.

[0050] As a result, the DC voltage level at the DC voltage output can be flexibly adapted to the high voltage specified on the central DC supply line. If necessary, a step-up converter, a so-called boost converter, is connected downstream of the photovoltaic generator to adjust the DC voltage level predetermined at the DC voltage output. This would be necessary if the DC output of the photovoltaic system itself does not provide a sufficiently high DC voltage level to be fed into the central supply line.

[0051] With this design, it is possible to advantageously connect or couple the electrolysis device in the electrolysis system via a central and insulated DC network on the power supply line and supply it with power obtained from the photovoltaic device. In this case, photovoltaic-based independent network operation is possible, wherein the corrosion effects caused by stray currents in the IT system are avoided or reduced. Similarly and corresponding to the advantages of connecting the electrolysis device to the wind power device as described above, operation in an independent network independent of the frequency of the public power grid is achieved, which in particular enables full design flexibility and can be used autonomously without relying on the public power grid. Therefore, the network frequency of 50 Hz to 60 Hz of the public power grid is not important for the design and operation of the electrical components in the DC network. Here, at most, in order to increase the voltage of the photovoltaic generator as required, a step-up converter (DC / DC converter) is provided so that the DC current is accurately fed into the central power supply line at a predetermined high voltage. If necessary, in the case of using a wind power device as a current supply source, a step-up converter can also be used downstream of the rectifier so that a higher voltage level can be set on the central power supply line when necessary than the voltage level delivered by the rectifier at the DC voltage output.

[0052] Preferably, in the electrolysis system, the current supply source has a hydraulic system as a current generator, the hydraulic system having a generator, wherein a rectifier having a DC voltage output is connected to the generator. In this embodiment, all operating components from the generator of the hydraulic system to the electrolysis system are also ungrounded, i.e., are designed as ungrounded components of the IT network. In particular, the generator of the hydraulic system is ungrounded.

[0053] Therefore, in the case of a hydropower plant, a generator that has already output a frequency higher than the network frequency at the generator output can be used, and this is advantageous. Therefore, the generator of the hydropower plant can be advantageously designed for the frequency of the alternating voltage input of the rectifier. Conversely, the rectifier can also be flexibly adjusted and selected according to the corresponding output frequency of the generator of the hydropower plant. Due to this lower complexity and number of components, additional cost advantages can be brought when connected to the hydropower plant, wherein the independent network operation of the electrolysis system can also be realized here. The output speed and thus the alternating current frequency of the generator can be obtained by the number of poles and the rotation speed. Therefore, the generator used for the hydropower plant can be used for the output of the alternating current of the higher frequency, so that the corresponding rectifier with the input designed for the higher frequency can be used in the electrolysis system. Thus, the operation independent of the network, that is, the network frequency of the public power grid does not need to be considered, is particularly advantageous. Due to expensive and large transformers, the coupling-in of the adaptation frequency for adjustment is not required or omitted in the case of the central DC network. In order to save line length, the electrolysis plant is arranged in the immediate vicinity of the DC current output of the rectifier of the generator and the hydropower plant and is integrated into the IT network via a DC high-power cable, ie the operating facility is set up for ungrounded and insulated operation.

[0054] Another particularly preferred aspect of the invention relates to the use of an insulated DC network in the electrolysis system, wherein the electrolysis device is connected to a central power supply line for DC current, thereby providing a central DC high-power cable designed for DC voltage and insulated from the ground, wherein the DC electrolysis current is fed into the electrolysis device.

[0055] The application thus enables the entire direct current high-power cable, starting from the generator of the current supply source up to the electrolysis plant with the electrolyser including module and process technology, to be operated in one and the same IT network.

[0056] In this application, an output voltage of more than 1.5 kV, in particular more than 10 kV, is preferably provided on the central supply line at the DC voltage output.

[0057] Particularly preferably, in this application, a high voltage of 10 kV to 110 kV, in particular 30 kV to 60 kV, is provided on a central supply line at the DC voltage output.

[0058] The advantages and advantageous embodiments of the electrolysis system according to the invention are to be regarded as the advantages and advantageous embodiments of the corresponding application, and vice versa.

[0059] Further advantages, features and details of the invention are apparent from the following description of preferred exemplary embodiments and from the drawings. The features and feature combinations mentioned in the above description and the features and feature combinations mentioned below in the description of the drawings and / or shown only in the individual drawings can be used not only in the respectively given combination but also in other combinations or alone without departing from the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Embodiments of the invention are explained in more detail with reference to the accompanying drawings. In the drawings, schematically and greatly simplified:

[0061] Figure 1 An electrolysis system designed for independent grid operation is shown, the electrolysis system having an electrolysis device and a wind energy device;

[0062] Figure 2 An electrolysis system designed for stand-alone network operation is shown, the electrolysis system having multiple module series.

[0063] In the drawings, the same reference numerals have the same meaning. DETAILED DESCRIPTION

[0064] Figure 1 An electrolysis system 10 according to the invention is shown. The electrolysis system 10 comprises an electrolysis device 1 and a current supply source 3. The current supply source 3 has a wind energy device 9 as a current generator, which serves as a renewable energy device (EE device) and a green current source. In the electrolysis system 10, the current supply source 3 is connected to the electrolysis device 1 via a central power supply line 5. In simple terms, the electrolysis device 1 functionally comprises an electrolysis unit 21 and a process technology unit 23, wherein the electrolysis unit has Figure 1 A plurality of electrolytic cells which are not shown in detail in the figure are stacked in the axial direction and electrically connected in series. In the electrolytic unit 21, the actual conversion reaction, i.e. the electrochemical decomposition of water as a reactant into hydrogen and oxygen as products, takes place in the electrolytic cell. The process technology unit 23 is used for the hydraulic interconnection of the electrolytic cell units of the electrolytic stack in order to supply fresh electrolyte, here the reactant water. Unlike the electrical interconnection, the hydraulic interconnection is a parallel connection. Therefore, due to the hydraulic interconnection of the electrolytic cell units to form an electrolytic stack, an additional and undesirable conductive connection is generated between all the electrolytic cell units. During the operation of the electrolytic stack composed of the electrolytic cell units, i.e. during the application of a voltage or current from the first electrolytic cell unit to the last electrolytic cell unit, the operating current flows through all the electrolytic cell units.

[0065] The electrolysis system 10 is supplied directly with direct electrolysis current via a central supply line 5 to which a high direct voltage is applied, so that the central supply line 5 forms a central direct current bus line, by means of which direct current for the electrolysis process can be directly supplied in the electrolysis system 10 of the electrolysis device 1 .

[0066] With respect to the power supply source 3, a rectifier 11 with a DC voltage output 7 is connected downstream of the wind energy installation 9 at the output of the generator. The alternating current generated by the generator of the wind energy installation 9 can thus be fed into the central power supply line 5 in the form of a DC current, wherein the voltage of the DC current is a high voltage predetermined at the DC voltage output 7. This realizes a central DC network designed for high voltage. When connecting the wind energy installation 9 to the central power supply line 5 in order to couple in the power generated by the wind energy installation 9 and fed into the rectifier 11, no additional active components, such as a transformer, are required, thereby realizing a particularly simple power supply topology for electrolysis.

[0067] pass Figure 1 The connection topology shown provides a central DC high-power cable in the electrolysis system 10, which is part of a network 17 insulated from the earth, i.e., a so-called IT network ("isoléterre (insulator)"). Here, the entire DC high-power cable is not grounded. All operating facilities, i.e., the power supply source 3, the generator of the wind power plant 9, the rectifier 11, the central DC power supply line 5, and even the electrolysis plant 1 including the electrolysis unit 21 and the process technology unit 23, are insulated from the earth by a high insulation resistance and are part of the IT network 17. During the operation of the electrolysis system 10, it operates electrically isolated from the earth. The protective grounding part 19 is installed on a conductive housing part that does not belong to the operating facility. The tower of the wind power plant 9 can be implemented as a grounded structure with a protective grounding part 19. Similarly, a protective grounding part 19 is also provided in the electrolysis plant 1, which is placed on the housing of the process technology unit 23 and connected to the earth as a ground wire.

[0068] Thus, there is no conductive ground connection at any point in the electrolysis system 10, although if necessary there is still a conductive ground connection locally in the electrolysis device itself in order to control residual stray currents that are still present. This ground connection can be connected or controlled as required. The ungrounded power supply topology avoids ground loops and significantly reduces stray currents to the earth in the entire device.

[0069] In order to monitor the high insulation resistance of the electrolysis system 10 to the earth, an insulation monitor 25A arranged near the wind energy device 9 is provided in the insulation network 17. Another insulation monitor 25B is placed near the electrolysis device 1. This arrangement of the insulation monitors 25A and 25B realizes two spatially separated network poles used as measuring points. As a result, the insulation monitors 25A and 25B identify possible grounding, asymmetry and too small insulation resistance of the insulation network 17. For this purpose, the insulation monitors 25A and 25B measure the symmetry of the voltage to the ground of the two network poles. If the leakage current of the two network poles is the same, the symmetry is maintained. In order to also be able to identify symmetrical insulation faults, the test signal can be fed into the network asymmetrically through the insulation monitors 25A and 25B and the reaction of the network 17 is measured. In a simple case, the test signal is a DC voltage. Therefore, the minimum insulation resistance of the insulation network 17 is monitored, the insulation fault can be detected, and the grounding can be located. At the same time, symmetrical and high-resistance grounding can be achieved through the two network poles of a pair of insulation monitors 25A, 25B.

[0070] Due to the omission of electrical decoupling in the insulating network 17, a more compact, easier to implement and very cheap power supply topology is provided, in particular for supplying direct current to the central power supply line 5, while providing good protection against stray currents and the adverse corrosion effects caused thereby. In this case, the DC high-power cables in the insulating network 17 and all conductors of the operating facility are at an undefined potential relative to the earth. For a reliable design of the insulating network 17, it is provided to use insulation monitors 25A, 25B as protection elements. In the case of a simple grounding, the electrolysis system 10 can continue to operate, since there is no direct danger to the electrolysis device 1, which increases availability. The IT network 17 is single-fault tolerant.

[0071] The DC voltage level at the DC voltage output 7 of the rectifier 11 can be flexibly adapted to the respective requirements in the electrolysis system 10, wherein the high output voltage is selected as a predetermined high voltage, which is preferably greater than 1.5 kV. Here, when configuring and designing the central and insulated DC network 17, the nominal voltages of the network level commonly used in energy transmission can also be used via the central supply line 5, for example, or these values ​​can be used as reference points for the DC voltage level. Here, on high-voltage lines at different network levels of medium voltage and high voltage (high voltage), electrical energy is transmitted with the following common nominal voltages: medium voltage: 3 kV, 6 kV, 10 kV, 15 kV, 20 kV, 30 kV, high voltage: 60 kV, 110 kV. In this case, the central supply line 5 is very advantageously used as a central DC bus line, via which a direct current supply based on high voltage can be directly realized for the electrolysis system 1.

[0072] In the case of a particularly compact design, i.e. spatially restricted and correspondingly small line spacings in the insulation network 17, the electrolysis device 1 in the electrolysis system 10 can be arranged at the bottom of the tower of the wind power plant 9 and connected directly to the central power supply line 5 for direct current as an operating facility in the IT network 17.

[0073] In another greatly simplified embodiment of the electrolysis system 10 according to the invention, Figure 2 An alternative interconnection of a DC high-power cable with a central power supply line 5 is shown. A wind power plant 9 is shown again as a power supply source 3 for providing direct current for electrolysis, which has a generator with an alternating current output. The alternating current is converted into direct current in a rectifier 11.

[0074] In the electrolysis system 10, a substantially similar Figure 1 The device scheme in the embodiment is provided with corresponding device components, wherein all operating facilities are set up and electrically connected in an insulated network 17 that can be operated with direct current, which includes direct current high-power cables. Here, the electrolysis devices 1A and 1B are electrically connected and powered by respective connecting lines 15A and 15B. The connecting lines 15A and 15B form a central direct current bus line or direct current high-power cable of the central power supply line 5 as a line pair. For this purpose, the electrolysis device 1A is connected to the direct current voltage output 7, and the other electrolysis device 1B is connected to the other direct current voltage output 7 of the rectifier 11 via the connecting line 15B connected in parallel with the connecting line 15A. The electrolysis devices 1A and 1B each have a module series 13, which includes a plurality of electrolysis modules electrically connected in series. Each module in the module series 13 has a plurality of electrolytic cells electrically connected in series.

[0075] A ground connection 19 that can be connected is locally arranged at the housing part of the operating facility of the electrolysis device 1A, 1B as a protective grounding part. The operating facility itself has a certain potential relative to the earth. The local ground connection of the housing part is placed on the last module of each module series 13 as a conductive connection. The conductive ground connection 19 has a predetermined low grounding resistance, which can be used to perform and optimize the control and discharge of stray currents. For this purpose, the conductive ground connection 19 can have an adjustable resistance. Through this additional measure, corrosion caused by stray currents that may still exist can be avoided or further reduced via an advantageous independent network operation.

[0076] Alternatively, it is also possible to provide an electrically conductive ground connection 19 at one module within the module series 13, depending on the voltage value and polarity at the two DC voltage outputs 7 of the rectifier 11. This can be flexibly adjusted to the respective DC voltage level at the DC voltage output 7 and the electrical design of the device concept of the electrolysis system 10. Thus, depending on the topology, grounding can also be accomplished at the middle of the module series 13. This arrangement is made accordingly and is advantageous for the case where the rectifier 11 outputs a symmetrical voltage at the DC voltage output 7, i.e., for example, outputs a value of + / -250 V at the DC voltage output 7. The ground connection 19 can also be a fixed connection, i.e., it does not necessarily have to be accessible, but can also simply be a fixed ground connection 19.

[0077] If necessary, it is also possible to connect the connecting lines 15A and 15B. Figure 1 and Figure 2 A step-down converter (not shown) is used to adjust the voltage level, the input voltage of which is comparable to the high DC voltage in the central DC network, and the output voltage of which is designed for the respective operating voltage of the electrolysis apparatus 1A, 1B. This enables an adapted operating mode of the electrolysis system 10 and establishes a separate DC voltage supply for each electrolysis apparatus 1A, 1B. The use of a plurality of high-current DC / DC converters, which may be connected in parallel in the connecting lines 15A, 15B and are of modular design, is particularly advantageous here.

[0078] This enables industrial applications and integration into electrolysis systems 10. A step-down converter converts an input voltage into a lower output voltage. It is also called a step-down converter.

[0079] Thus, it is advantageously possible to connect any number and size of electrolysis devices 1A, 1B having independently adaptable module series 13 to an insulated DC network 17, more precisely to one or more such central DC branch cables in the connecting lines 15A, 15B, with the aid of an adjustable DC / DC converter, in particular a so-called adjustable step-down converter or buck converter, and to operate them in an independent network designed as an insulated DC network 17.

[0080] The DC / DC converter reduces the DC voltage to the desired value individually, without significant conversion loss. Therefore, in the electrolysis system 10, the electrolysis equipment 1A, 1B is adjustable in terms of electrolysis power, and can be powered on or off as required. Partial load capacity or partial load control is realized by regulating the electrolysis current. By adjusting the power regulator, the independent network capacity in the insulated DC network is ensured and expanded, which brings significant cost advantages for remote onshore equipment or even offshore equipment. In order to provide higher electrolysis current, multiple DC / DC converters can be connected in parallel and placed in the connecting line 15A, 15B if necessary. For example, an adjustable reduction converter can be used as a buck converter, and the reduction converter regulates the output voltage by the method of pulse width modulation during uninterrupted operation. In this way, the continuous operation of the buck converter is realized, and the electrolysis current supplied to the electrolysis equipment 1A, 1B can be adjusted.

[0081] In the electrolysis system 10, the current supply source 3 can also have a photovoltaic system with a plurality of photovoltaic modules, not shown in detail. The photovoltaic system can be, for example, a large-scale and high-performance open-air system, preferably in a sunny area, so that photovoltaic power of 10 MW or more of electrical power can be used for electrolysis. Other types of power generation from renewable energy sources can also be used.

[0082] Compared to power supplies based on alternating current, the central DC high-power cable of the insulated network 17 largely eliminates the need for transformers. Due to the design and provision of the central high-voltage DC current supply network, the material and installation space usage caused by the weight and size of the transformer required in the case of an AC network connection can be significantly reduced. This reduces the material usage, especially for iron and copper, which in turn reduces the installation space requirement.

[0083] With the electrolysis system 10 according to the invention, it is possible in a particularly advantageous and cost-effective manner to electrically connect a preferably onshore wind energy installation to an electrolysis installation in an insulated DC network 17, which is usually set up in a spatially restricted manner. As a result, the voltage differences that may exist across the network poles are a priori smaller. The insulation monitors 25A, 25B also provide precautions for safe IT network operation, in particular for faults of the second order, i.e. symmetrical insulation faults of both network poles can also be detected. Thus, a first grounding that may exist is harmless in the IT network 17, since the currents caused only by the line capacity and insulation resistance of the operating facilities of the electrolysis system 10 are very small. If the spatial extent of the network 17 is small, the leakage current in the event of a fault is so small that it is also harmless.

Claims

1. An electrolysis system (10), comprising an electrolysis device (1, 1A, 1B) and a current supply source (3) with a DC voltage output (7) and a central power supply line (5), wherein: The central power supply line (5) is connected to the DC voltage output (7) of the current supply source (3), so that a DC current can be fed into the central power supply line (5), wherein a central DC high-power cable designed for DC voltage is provided, and the electrolysis device (1) is connected to the DC high-power cable via the central power supply line (5), wherein the current supply source (3) and the DC high-power cable are components of a network (17) insulated from the ground.

2. The electrolysis system (10) according to claim 1, wherein: An insulation monitor (25A, 25B) is provided to enable monitoring of the minimum insulation resistance of the insulated network (17) relative to earth and detection of insulation faults.

3. The electrolysis system (10) according to claim 1 or 2, wherein: The power supply source (3) has a wind power installation (9) as a current generator, to which a rectifier (11) having a DC voltage output (7) is connected, wherein the DC voltage output (7) is designed for the high voltage in a central DC high-power cable.

4. The electrolysis system (1) according to claim 3, wherein: The electrolysis system comprises an electrolysis device (1) which is arranged at the base of a tower of the wind power installation (9) and is directly connected there to the central power supply line (5).

5. The electrolysis system (10) according to any one of the preceding claims, wherein: The electrolysis device (1, 1A, 1B) has a plurality of electrolysis modules connected in series, thereby forming a module series (13).

6. The electrolysis system (10) according to claim 5, wherein: A connectable, electrically conductive ground connection (19) having a predetermined ground resistance is provided in the module series (13), by means of which stray currents can be controlled.

7. The electrolysis system (10) according to claim 5, wherein: A permanently installed, electrically conductive ground connection (19) with a predetermined ground resistance is provided in the module series (13), by means of which stray currents can be controlled.

8. The electrolysis system (10) according to any one of the preceding claims, wherein: The electrolysis system comprises at least two electrolysis devices (1A, 1B) connected in parallel with each other with respect to the central power supply line (5), wherein the electrolysis devices (1A, 1B) are connected to the central power supply line (5) via corresponding connecting lines (15A, 15B).

9. The electrolysis system (10) according to any one of the preceding claims, wherein: The power supply source (3) has a photovoltaic system as a power generator, the photovoltaic system having a DC voltage output (7), wherein the DC voltage output (7) is designed for high voltage and wherein the DC voltage output (7) is connected to the central power supply line (5).

10. The electrolysis system (10) according to any one of the preceding claims, wherein: The power supply source (3) has a hydraulic system as a power generator, which has a generator, wherein a rectifier (11) having a DC voltage output (7) is connected to the generator.

11. Use of an insulated direct current network (17) in an electrolysis system (1) according to any one of the preceding claims, wherein: The electrolysis device (1, 1A, 1B) is connected to a central power supply line (5) for direct current, so that a central direct current high-power cable designed for direct voltage and insulated is provided, wherein the direct current electrolysis current is fed into the electrolysis device (1, 1A, 1B).

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