Electrolysis device and device network comprising electrolysis device and renewable energy device

Abstract

The invention relates to an electrolysis device (1) comprising an electrolyser (3) and a circuit arrangement (5) having an input (7) connected to an external DC power source and an output (9) connected to the electrolyser (3). The circuit arrangement (5) has a transformer (11), which is connected to the inverter (13) on the primary side and to the rectifier (15) on the secondary side, such that direct current can be supplied to the electrolyzer (3). The invention also relates to a device network (100) comprising an electrolysis device (1) and a renewable energy device (50) directly coupled to the electrolysis device (1).

Description

Technical Field

[0001] The present invention relates to an electrolysis device comprising an electrolyzer and a circuit device. The present invention also relates to a device network comprising an electrolysis device and a renewable energy device connected to the electrolysis device. Background Art

[0002] Electrolysis equipment is a device that uses electric current to convert substances (electrolysis). There are also many types of electrolysis equipment according to different electrochemical electrolysis processes, such as electrolysis equipment for electrolyzing water.

[0003] Nowadays, hydrogen is produced from water, for example, by means of proton exchange membrane (PEM) electrolysis or alkaline electrolysis. Electrolysis plants use electrical energy to produce hydrogen and oxygen from supplied water. The process takes place in an electrolysis stack consisting of a plurality of electrolysis cells. Water is introduced as a reactant into the electrolysis stack under the action of a direct current voltage (DC voltage), and after flowing through the electrolysis cells, two fluid flows consisting of water and gas bubbles (O2 or H2) emerge.

[0004] 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 may be hydrogen produced by a water electrolysis plant in particular. 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.

[0005] Hydrogen is a particularly environmentally friendly and sustainable energy carrier. Hydrogen has the unique potential to enable energy systems, transport and large parts of chemistry without CO2 emissions. In order to succeed in this, hydrogen cannot come from fossil energy sources, but must be produced with the help of renewable energy. At least today, more and more electricity generated from renewable energy sources is fed into the public grid. Therefore, if the electrolysis plant is operated with electricity from the public grid, a corresponding proportion of green hydrogen can be produced depending on the electricity mix.

[0006] In electrolysis designed on an industrial scale, direct current is mainly provided by line-commutated (grid-guided) rectifiers. In this process of rectifying the alternating voltage in the grid, resonances can occur due to the way the rectifiers work, which can put stress on the AC grid and / or the DC grid.

[0007] Patent document EP 3 723 254 A1 discloses such an electrolysis device, which is connected to a public power grid and is supplied with power grid current accordingly. For this purpose, the electrolysis device has a circuit device including four coil devices and four rectifiers. The first coil of the coil device is connected to the DC voltage side of one of the rectifiers. The circuit device also includes two transformers, which have a primary winding and two secondary windings respectively. The primary winding of the transformer is connected to a power grid, such as a medium-voltage power grid or a high-voltage power grid. In this way, although the iron content in the first coil is reduced, the required smoothing of the DC power or the attenuation of the resonance can still be achieved.

[0008] 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 coast. However, the challenge is that large distances to the consumer must be overcome. 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 fulfill the function of an energy storage device, because the pressure inside can be varied within a certain range.

[0009] 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 plant 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 and to supply the electrolysis plant with the generated electricity.

[0010] The following concept has also been proposed for the mainland, that is, the electricity generated by the onshore wind power plant or photovoltaic device is at least partially used directly to produce hydrogen by directly connecting to the electrolysis device and feeding into the electrolysis device. In all these applications, the electrolysis device is part of an independent power grid. The electrolysis power is not obtained from the public power grid, but is directly provided by the wind power device or photovoltaic device and fed into the electrolyzer of the electrolysis device. Here, the electrical energy generated by the wind power device or photovoltaic device can also be temporarily stored in a battery, for example. Compared with the line commutation (grid guidance) operation described above, this solution brings special challenges and problems in the electrical connection and interconnection of the electrolysis device and the corresponding renewable power generation device (whether it is a wind power device or a photovoltaic device), especially when it comes to ensuring the safety and first of all trouble-free operation of the electrolysis device that directly forms a device network with the renewable power generation device. Summary of the invention

[0011] It is therefore an object of the present invention to provide an electrolysis plant with the aid of which electric current generated by renewable energy sources can be fed directly and without interference into the electrolysis plant.

[0012] According to the present invention, this object is achieved by an electrolysis device, which includes an electrolyzer and a circuit device, the circuit device having an input end connected to an external DC power supply and an output end connected to the electrolyzer, wherein the circuit device has a transformer, the transformer is connected to an inverter on the primary side and is connected to a rectifier on the secondary side, so that direct current can be supplied to the electrolyzer.

[0013] The present invention is based on the following recognition, that electrolysis equipment, in particular the PEM water electrolysis cell of the electrolyzer is very sensitive to high-frequency stray currents. These stray currents can be coupled into the electrolysis equipment via a ground connection or a ground connection. Due to the necessary equipment components of the electrolysis equipment such as process technology, gas separators, auxiliary systems, supply pipelines for guiding water, etc., the connection with the ground is insufficient for electrolysis (ground fault or ground loop). Therefore, on the one hand, it is important to avoid that the current path can be closed via the ground, that is to say, to prevent the formation of a ground fault or a ground loop. On the other hand, the electromagnetic interference field itself is avoided as much as possible to couple in or at least reduce interference. This problem is particularly evident when the electrolysis equipment is directly connected to a DC power supply provided by, for example, a photovoltaic device or a wind energy device.

[0014] Therefore, in this complex network of devices consisting of renewable power generation devices and electrolysis devices (which are directly fed with renewable energy for the electrolysis current in order to carry out the electrolysis), the adverse effects of ground loops and the coupling of alternating electromagnetic fields into the power electronics used are correspondingly large. As an example, a wide and preferred application of bipolar transistors with insulated gate electrodes (English: insulated-gate bipolar transistor, abbreviated IGBT) is in rectifiers that supply high currents to the electrolysis. IGBT is a semiconductor device used in power electronics because it combines the advantages of bipolar transistors (such as good conduction characteristics, high blocking voltage, robustness) and the advantages of field effect transistors, which require almost no power for control. For example, in a so-called three-phase B6 bridge circuit with a rectifier based on IGBT, a very precise control of the electrolysis current is achieved with good rectification. The significant advantages of IGBT are the higher voltage limit and current limit, which can reach 6500V, 3600A and 100MW, which predestines the application of IGBT in electrolysis devices.

[0015] With the present invention, an AC intermediate circuit is provided in the electrolysis device by a circuit arrangement, which makes the external DC power supply and the electrolyzer electrically decoupled. In the AC intermediate circuit, an inverter ensures that the DC voltage from the external DC power supply is converted into an AC voltage coupled with a transformer on the primary side. A rectifier is connected to the secondary side of the transformer, which ensures conversion back to a DC voltage, in particular to a voltage level or current level required and predetermined for electrolysis. Therefore, the circuit arrangement is particularly advantageously designed as an AC intermediate circuit and is designed to provide DC power by an external DC power supply so as to supply electrolysis current to the electrolyzer. This is achieved by directly coupling or directly connecting the input end to the external DC power supply. A wind energy device or a photovoltaic device can be advantageously connected to the electrolysis device as an external DC power supply, and the wind energy device or the photovoltaic device can be advantageously configured for offshore and onshore applications in a so-called independent operation in a manner independent of the power grid.

[0016] An external DC power source can be connected directly via the input of the circuit arrangement, so that a direct current supply to the electrolyser is possible. By means of the electrical isolation and decoupling via the AC intermediate circuit, damaging interferences of high-frequency stray currents and thus ground fault currents and undesirable voltage losses in the electrolyser are reliably avoided with the circuit arrangement. At the same time, a convenient and reliable direct connection of the electrolysis plant to a renewable power plant and an operation independent of the power grid are possible. The AC intermediate circuit advantageously makes it possible to achieve particularly good and flexible adaptation to changing voltage or current levels on the power generation side.

[0017] In particular in alkaline electrolysis applications based on alkaline electrolysis operation, the electrical isolation proposed by the invention should also be preferred for further reasons. The electrical isolation advantageously reduces ground currents and stray currents caused by the electrolysis. The reason for this is that the ground loop cannot be closed. By means of the electrical isolation, the current loop through the ground is also advantageously interrupted.

[0018] In this case, the secondary side of the transformer in the AC intermediate circuit is preferably designed to be ungrounded. This not only provides effective protection from high-frequency signal components on the connection line from the power supply, but also significantly reduces and suppresses DC stray currents, because a closed ground loop exists again.

[0019] In this case, the voltage on the input side of the AC intermediate circuit is preferably higher than the voltage required for electrolysis operation. This reduces losses or reduces the cross-sectional area required for copper or aluminum wires, thus saving costs and also overcoming greater line distances, for example from the tower of a wind turbine with a height of about 100 m down to the electrolysis plant.

[0020] In a preferred embodiment, the rectifier can be controlled and / or designed as a three-phase rectifier, in particular a B6 bridge rectifier.

[0021] The controllability of one or more rectifiers, which are advantageously designed as three-phase rectifiers or B6 bridge rectifiers, allows the total current generated via the one or more rectifiers to be adjusted and thus, for example, the operation of an electrolyser connected to the circuit arrangement to be controlled.

[0022] Preferably, it is provided that the frequency of the alternating current can be set to a predetermined value in the circuit arrangement. Since the circuit arrangement is designed as an AC intermediate circuit, it does not need to be connected to the public grid, so that the frequency of the alternating current in the transformer can be selected freely to a large extent. It is advantageous to provide a high-frequency transformer here so that it can differ from the normal frequency in the public grid.

[0023] In a preferred embodiment of the electrolysis plant, the circuit arrangement is designed for an alternating current frequency that is higher than the usual grid frequency of 50 Hz to 60 Hz of the public grid. It is appropriate to use a higher frequency here because it is possible to reduce the structural size and weight of the transformer and the amount of material used. This is particularly advantageous when the electrolysis plant is directly connected to a wind power plant. Due to the more compact structural design and the lower weight at high operating frequencies, the transformer can be placed, for example, in the nacelle of the wind power plant or at the bottom of the tower of the wind power plant. The circuit arrangement as a whole can also be arranged there. Therefore, the electrolysis plant can be close to the wind power plant, for example, so that the line length for the connection can be very short.

[0024] In a particularly preferred embodiment, the circuit arrangement is designed for an alternating current frequency of 500 Hz to 50 kHz, in particular 10 kHz to 30 kHz. This frequency is related to the frequency of the inverter and rectifier connected to the transformer. In order to utilize the advantages of installation space and cost, a high-frequency intermediate circuit transformer is provided as the transformer.

[0025] Furthermore, it is preferred to provide a transformation ratio or a voltage swing of less than 10, in particular between 1.5 and 7.5, for the transformer. This allows flexible adaptation to the requirements of the electrolyser or the voltage level required for the electrolysis process.

[0026] The ratio of the number of turns or the ratio of the voltage between the primary side and the secondary side is also called the transformation ratio. By appropriately selecting the transformation ratio, i.e. the number of turns, the transformer can be used to step up or step down the AC voltage. This makes it possible to adapt to electrolysis.

[0027] However, depending on the application and design of the electrolysis device, in particular depending on the transformer used, voltage swings greater than 10 are also possible. Known electrolysis devices usually operate with a maximum DC voltage of 1500V, but this still corresponds to the low voltage range. However, for the case of connection with a power generation device, a DC voltage greater than 15kV can certainly be set and provided. Therefore, the upper limit of the voltage swing can preferably be selected to reach 70. As an example, if the electrolysis device is operated at a DC voltage of only 1000V, the available connection voltage can reach about 70kV. For currently available wind energy devices, for example, an output voltage of 66kV AC voltage can be delivered.

[0028] The voltage on the power plant side is preferably greater than the voltage on the electrolysis plant side.

[0029] Another aspect of the invention is the design of the electrolysis device for the preferred electrical connection of the electrolysis device to an external DC power source, wherein the renewable energy device is directly electrically connected to the electrolysis device, thereby providing an integrated device network.

[0030] In a particularly preferred embodiment, the plant network comprises an electrolysis plant and a renewable energy plant having an output for providing direct current, so that a direct current power supply is formed by the renewable energy plant, wherein the output is electrically connected to an input of the electrolysis plant.

[0031] This makes it possible to operate the system in an independent grid operation independent of the public grid and to use electricity generated exclusively from renewable energy sources directly for electrolysis to form green hydrogen.

[0032] In the network of plants, the renewable energy plant is preferably a wind energy plant. In this case, the wind energy plant further preferably has a rectifier, which is coupled to the input of the circuit arrangement on the output side, i.e. is electrically connected to the input. In this case, the rectifier converts the alternating current from the wind energy plant into direct current and advantageously provides the desired input DC voltage level for coupling to the electrolysis plant at the same time. Furthermore, the rectifier is preferably designed for coordinated operation with a coupled generator or for appropriate control of the coupled generator.

[0033] In an alternative design, the renewable energy device in the device network can also preferably be a photovoltaic device. The photovoltaic device already provides direct current during operation. However, it is preferably provided that the photovoltaic device in the device network has a DC regulator or a DC transformer, which is connected to the input end on the output side. In this case, electrical isolation can also be provided and integrated in such a DC regulator (DC-DC converter) of the photovoltaic device. Then preferably only another downstream DC regulator (DC-DC converter) is required to set the voltage of the electrolysis device and bring it to the DC level required for electrolysis.

[0034] A DC transformer, also known as a DC-DC converter, is a circuit that converts a DC voltage provided at the input terminal into a circuit with a higher, lower or opposite voltage level. The conversion is performed with the help of a periodically working electronic switch and one or more energy storage devices. A DC transformer is a self-commutating current converter. It is also called a DC regulator in the field of electrical energy technology. The inductor (inductive converter) used to temporarily store energy is composed of a coil or a converter transformer. Known converter transformers have advantageously provided electrical isolation, so their application may be preferred under certain connection conditions and technical conditions.

[0035] The advantages and advantageous embodiments of the electrolysis plant according to the invention are to be regarded as the advantages and advantageous embodiments of the plant network, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Further advantages, features and details of the invention are apparent from the following description of preferred exemplary embodiments and with reference to the drawings. The features and feature combinations mentioned above in the description and the features and feature combinations mentioned below in the description of the drawings and / or shown individually in the individual drawings can be used not only in the respectively indicated combination but also in other combinations or alone without departing from the scope of the invention.

[0037] Embodiments of the present invention are explained in more detail with reference to the accompanying drawings. Here, schematically and greatly simplified:

[0038] Figure 1 A plant network with electrolysis plants and wind energy plants;

[0039] Figure 2 A plant network with electrolysis plants and photovoltaic plants.

[0040] The same reference numerals in the figures have the same meaning. DETAILED DESCRIPTION

[0041] Figure 1The device network 100 according to the present invention is shown. The device network 100 includes an electrolysis device 1 and a wind energy device 50A connected to the electrolysis device 1, which serves as a renewable energy device (EE device) and a green power source. The electrolysis device 1 has an electrolyzer 3 and a circuit device 5 electrically connected to the electrolyzer 3. The circuit device 5 is connected to the electrolyzer 3 via an output terminal 9. The circuit device also has an input terminal 7, via which direct current can be supplied to the electrolysis device. Direct current from a direct current power source is supplied via the circuit device 5. For this purpose, the circuit device 5 has an inverter 13, a transformer 11 and a rectifier 15. Therefore, an alternating current intermediate circuit is provided in the electrolysis device using the circuit device 5, through which the input terminal 7 is electrically decoupled from the output terminal 9. On the primary side, the inverter 13 is connected to the transformer 11. On the secondary side, the rectifier 15 is connected to the transformer 11. Direct current, i.e., electrolysis current, is supplied to the electrolyzer 3 via the rectifier 15 of the circuit device 5. The electrolyser 3 can be designed as a PEM electrolyser, an AEM electrolyser (AEM: Anion Exchange Membrane) or an alkaline electrolyser.

[0042] In order to supply direct current for the electrolysis process, the electrolysis device 1 is directly connected to the wind energy device 50A. The connection is made via the input 7 of the circuit arrangement 5, which is designed to receive direct current and transmit it to the inverter 13. The wind energy device 50A first generates alternating current in a generator. In order to be able to transmit direct current to the electrolysis device 1, a rectifier 52 is provided, so that the connection is made via the rectifier 52, wherein the rectifier is advantageously an electrical power component of the wind energy device 50A.

[0043] In order to change the voltage or current intensity for electrolysis, the rectifier 15 can be adjusted and is constructed as a three-phase rectifier, such as a B6 bridge rectifier. It has an IGBT, i.e. an insulated gate bipolar transistor, as a semiconductor device, which is not shown in detail. This is a commonly used component in power electronics because it combines the advantages of bipolar transistors (such as good conduction characteristics, high blocking voltage, robustness) and the advantages of field effect transistors, and almost no power is required for control. The significant advantages of IGBTs are higher voltage limits and current limits, the operating voltage can reach 6500V, the current can reach 3600A, and the power can reach 100MW. This makes the IGBT in the rectifier 15 ideal for the working range of the electrolyzer 3. Depending on the application, it is also conceivable to use so-called IGCTs, i.e. integrated gate commutated thyristors. This integrated gate commutated thyristor has reduced wiring work, increased maximum pulse frequency for control, and better switching time when connected in series, which is advantageous. The application field of IGCT is high-power current converters. At a typical blocking voltage of 4500V, a single module typically switches or disconnects thousands of amperes of current.

[0044] In the circuit arrangement 5, the AC frequency of the transformer 11 can be flexibly adjusted to a predetermined value. In this example, the circuit arrangement 5 is designed for an AC frequency that is higher than the usual grid frequency of 50-60 Hz of the public grid, which is advantageous. An AC frequency of 500 Hz to 50 kHz, in particular 10 kHz to 30 kHz, can be set, so that the transformer 11 acts as a high-frequency intermediate circuit transformer. In this frequency range, the transformer 15 has a considerable construction space advantage, so that a significantly more compact construction using less material can be achieved compared to a grid transformer.

[0045] In this case, a transformation ratio of less than 10 is provided in the transformer 11 for the voltage level on the secondary side relative to the primary side, in particular a transformation ratio of between 1.5 and 7.5. However, the transformation ratio can be greater than 10 and can reach 70. By means of the circuit arrangement 5, electrical decoupling is achieved via the DC intermediate circuit. In this case, the transformer 11 is preferably not grounded at the star point on the primary side. Further preferably, the transformer 11 is also not grounded at the star point on the secondary side. This prevents high-frequency stray currents during operation, which can couple in via ground loops and adversely affect the electrolyser 3 with very sensitive electrolytic cells, since the ohmic losses caused by the ground loops can lead to very unfavorable voltage drops across the electrolytic cells.

[0046] All other ground stray currents in the area of ​​the electrolysis itself, in particular direct current stray currents of 0 Hz, are also avoided. This reduces corrosion in particular in the so-called process technology and in sensitive auxiliary systems of the electrolysis plant 1 and increases the service life of the electrolysis modules and electrolysis cells.

[0047] The lower the resistance of the ground connection between the components involved, the lower the potential difference and interference currents. This is usually achieved by cable connections and plug connections with lower resistance (more precisely, larger shield cross-sections and lower contact transition resistance) or by the advantageous electrical decoupling described herein.

[0048] During the operation of the device network 100, green power is generated in the wind energy device 50A. The alternating current generated in the generator is converted into direct current in the rectifier 52. Thus, a DC power supply is provided by the renewable energy device 50, which is exemplified by the wind energy device 50A, so that the direct current is directly fed into the input terminal 7 of the electrolysis device 1 via the output terminal of the rectifier 52 and first transmitted to the circuit device 5. In the circuit device 5, the circuit loop is electrically isolated by the transformer 11, thereby suppressing or avoiding stray currents. First, it is converted into an alternating voltage on the primary side of the transformer 11. The transformer 11 converts the alternating voltage into a desired voltage level on the secondary side according to the set transformation ratio. On the output side, a direct current electrolysis voltage without interference or humming is provided at the output terminal 7 by the rectifier 15, and the electrolyzer 3 in which water is decomposed into hydrogen and oxygen is stably operated with this direct current electrolysis voltage. Ground loops are avoided. The advantageous direct DC connection of the electrolysis plant 1 to the wind energy plant 52A allows independent operation independent of the grid and the generation of green electricity in a decentralized manner, onshore or offshore, depending on the application. The proportion of green hydrogen is 100%.

[0049] In another embodiment of the device network 100 according to the present invention, Figure 2 An alternative DC power source for supplying DC power to the electrolysis device 1 is shown. In this case, the renewable energy device 50 has a photovoltaic device 50B having a plurality of photovoltaic modules, not shown in detail. The photovoltaic device 50B can be designed, for example, as a large-scale and high-performance open-air device, preferably in a sunny area, so as to provide a photovoltaic power of 10 MW of electrical power for the electrolysis. For the electrolysis device 1, a photovoltaic power source with a DC power of 10 MW is used. Figure 1 A completely similar system concept and corresponding system components, namely with the circuit arrangement 5 and the electrolyser 3 .

[0050] In order to achieve the desired and advantageous voltage level for connection to the electrolysis device 1, Figure 2 In this example, a DC regulator 54 is connected to the photovoltaic device 50B. The DC regulator 54 is also called a DC-DC converter, so that the DC voltage provided from the photovoltaic device 50B at its input is converted into a DC voltage with a higher, lower or opposite voltage level. The conversion is performed with the help of a periodically working electronic switch and one or more energy storage devices. The DC regulator 54, also called a DC transformer, is an autonomous current converter that plays an important role in the field of electrical energy technology. The inductor (inductive converter) for temporarily storing energy is composed of a coil or a converter transformer. By designing it as a converter transformer, electrical isolation has been achieved.

[0051] The DC regulator 54 connected to the photovoltaic system 50B is connected to the input 7 of the circuit arrangement 5 on the output side, thereby achieving direct connection to the electrolysis system 1 and supplying photovoltaic DC power, wherein stray currents are effectively suppressed by electrical decoupling.

[0052] The invention provides an electrolysis plant 1, by means of which direct current generated from a renewable source can be fed directly and without interference into the electrolysis plant 1, so that 100% green hydrogen can be produced in the electrolysis. This is particularly advantageous in the described plant network 100, which comprises an electrolysis plant 1 and a renewable energy plant 50 which are directly electrically connected to one another.

Claims

1. An electrolysis device (1), comprising an electrolyzer (3) and a circuit device (5), wherein the circuit device has an input terminal (7) connected to an external DC power supply and an output terminal (9) connected to the electrolyzer (3), wherein: The circuit arrangement (5) has a transformer (11) which is connected on the primary side to an inverter (13) and on the secondary side to a rectifier (15) so that the electrolyser (3) can be supplied with direct current.

2. The electrolysis device (1) according to claim 1, wherein: The rectifier (15) can be controlled and / or designed as a three-phase rectifier, in particular a B6 bridge rectifier.

3. The electrolysis device (1) according to claim 1 or 2, wherein: In the circuit device (5), the frequency of the alternating current can be set to a predetermined value.

4. The electrolysis device (1) according to any one of the preceding claims, wherein: The circuit device (5) is designed to have an alternating current frequency which is higher than the usual grid frequency of 50-60 Hz of the public grid.

5. The electrolysis apparatus (1) according to any one of the preceding claims, wherein: The circuit arrangement (5) is designed to provide an alternating current frequency of 500 Hz to 50 kHz, in particular 10 kHz to 30 kHz.

6. The electrolysis apparatus (1) according to any one of the preceding claims, wherein: The transformer (11) has a transformation ratio of less than 10, in particular between 1.5 and 7.

5.

7. The electrolysis apparatus (1) according to any one of the preceding claims, wherein: The transformer (11) is not grounded at its primary-side star point.

8. The electrolysis apparatus (1) according to any one of the preceding claims, wherein: The transformer (11) is not grounded at the star point on its secondary side.

9. A plant network (100) comprising an electrolysis plant (1) according to any one of the preceding claims and a renewable energy plant (50), the renewable energy plant having an output for providing direct current, so that a direct current power supply is formed by the renewable energy plant (50), wherein: The output end is connected to the input end (7) of the electrolysis device (1).

10. The device network (100) according to claim 9, wherein: The renewable energy plant (50) has a wind energy plant (50A).

11. The device network (100) according to claim 10, wherein: The wind energy installation has a rectifier (52) which is connected to the input (7) on the output side.

12. The device network (100) according to claim 9, wherein: The renewable energy device (50) has a photovoltaic device (50B).

13. The device network (100) according to claim 12, wherein: The photovoltaic system (50B) has a DC regulator (54) which is connected to the input (7) on the output side.

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