Electrolyser device, electrolyser, and method for operating the electrolyser device

Abstract

The invention relates to an electrolyser device (32a-f) comprising: at least one first electrolysis cell (10a-f), at least one second electrolysis cell (12a-f), and at least one main power supply (14a-f) which is at least provided to supply electrical energy, in particular electrolysis energy, jointly to the first electrolysis cell (10a-f) and the second electrolysis cell (12a-f). According to the invention, the electrolyser device (32a-f) comprises at least one first auxiliary power supply (16a-f) which is assigned to the first electrolysis cell (10a-f), and at least one second auxiliary power supply (18a-f) which is assigned to the second electrolysis cell (12a-f), wherein the auxiliary power supplies (16a-f, 18a-f) are provided in order to balance out the electrolysis cells (10a-f, 12a-f) by electrically discharging and / or electrically feeding the relevant electrolysis cells (10a-f, 12a-f).

Description

[0001] Electrolyzer device, electrolyzer and method for operating the electrolyzer device

[0002] State of the art

[0003] The invention relates to an electrolyzer device according to the preamble of claim 1, an electrolyzer according to claim 15 and a method according to the preamble of claim 16.

[0004] An electrolyzer device comprising at least one first electrolysis cell, at least one second electrolysis cell, and at least one main power supply, which is intended at least to jointly supply the first electrolysis cell and the second electrolysis cell with electrical energy, has already been proposed. Since electrolysis cells of electrolysis cell stacks are never absolutely identical to one another, e.g., due to manufacturing tolerances, they can exhibit different cell voltages during operation at the same current level.On the one hand, this can result in negative effects with regard to the overall ageing of all electrolysis cells in the interconnected operation of the electrolysis cell stack, in particular because a "poorer" electrolysis cell, which has a higher voltage at the same current level compared to a "better" electrolysis cell, consumes more power than the "better" electrolysis cell and thus, at the same current level, the "poorer" electrolysis cell ages faster than the "better" electrolysis cell.On the other hand, negative effects can also result in the overall performance of all electrolysis cells in the interconnected operation of the electrolysis cell stack, in particular since the operation of the “better” electrolysis cells must be restricted if the “worse” cell would reach too high a voltage due to the same high current and thus the maximum possible performance in a series connection of electrolysis cells would be limited by the weakest link, i.e. the “worst” electrolysis cell of the electrolysis cell stack.

[0005] The object of the invention is, in particular, to provide a generic device with advantageous properties regarding the operation of electrolyzers, in particular by eliminating the disadvantages of the prior art. This object is achieved according to the invention by the features of patent claims 1, 15, and 16, while advantageous embodiments and further developments of the invention can be found in the subclaims.

[0006] Advantages of the invention

[0007] The invention is based on an electrolyzer device, for example a proton exchange membrane electrolyzer device, an electrolyzer device with cells for alkaline electrolysis or another electrolyzer device having other electrochemical cells, with at least one first electrolysis cell, for example a proton exchange membrane electrolysis cell, an electrolysis cell for alkaline electrolysis or an electrolysis cell based on a different functional principle, with at least one second electrolysis cell, for example a proton exchange membrane electrolysis cell, an electrolysis cell for alkaline electrolysis or an electrolysis cell based on a different functional principle, and with at least one main power supply which is provided at least to supply the first electrolysis cell and the second electrolysis cell jointly with electrical energy, in particular electrolysis energy.

[0008] It is proposed that the electrolyzer device comprise at least a first auxiliary power supply, which is assigned at least to the first electrolysis cell, and at least a second auxiliary power supply, which is assigned at least to the second electrolysis cell, wherein the auxiliary power supplies are provided to balance the electrolysis cells with respect to one another by, in particular independently of one another, electrically unloading and / or electrically feeding the respective electrolysis cell. This can advantageously improve the service life of electrolyzers. Advantageously, aging of different electrolysis cells of the electrolyzer or at least one cell cluster (stack) in the electrolyzer can be equalized. Advantageously, the overall efficiency of all electrolysis cells in an electrolysis cell stack or in an electrolyzer can be improved.Advantageously, an operation of the electrolyzer can be enabled in which at least one electrolysis cell can reach the end of its life at a desired time, e.g. together with at least one neighboring electrolysis cell of a cell cluster (stack) of an electrolyzer or together with all other electrolysis cells of an electrolyzer or at least one cell cluster (stack) in the electrolyzer.

[0009] In addition, the auxiliary power supplies can advantageously enable highly precise minimum production (in the watt range). Furthermore, it is advantageous to influence the aging of specific electrolysis cells or specific electrolysis cell stacks (keyword: timely stack replacement). Furthermore, a system can advantageously be kept running despite a malfunction, e.g., due to a partially defective electrolysis cell. Furthermore, the auxiliary power supplies could advantageously enable the supply of peripherals to an electrolyzer system, so that the electrolyzer system could advantageously be operated solely via the DC power supply of the electrolysis cell stacks or the electrolyzer (keyword: power-to-home).

[0010] An "electrolyzer device" is to be understood in particular as at least a part of a device and / or a machine, in particular an electrolyzer, which is intended to carry out at least one electrolysis step, in particular on water. In particular, the electrolyzer device can also comprise the entire device and / or the entire machine, in particular the entire electrolyzer. An "electrolysis cell" is to be understood in particular as a functional unit by means of which at least one electrochemical electrolysis reaction can be carried out. In particular, the electrolysis cell can form a cell stack-compatible electrolysis cell, in particular an electrolysis cell stack. The electrolysis cell advantageously comprises at least one anode, at which oxygen is preferably formed in the normal operating state.The electrolysis cell preferably comprises at least one cathode, at which hydrogen is preferably formed in the normal operating state. The electrolysis cell advantageously comprises at least one membrane, in particular an advantageously selectively proton-conducting membrane, preferably a polymer electrolyte membrane. Particularly preferably, the anode and the cathode are separated from one another at least by the membrane. In particular, the anode and / or the cathode are flat and / or layered and / or a layer and / or coating. Preferably, the membrane is formed at least partially and particularly preferably at least largely from naniline. The electrolysis cell preferably comprises at least one functional element, in particular a bipolar element, preferably a bipolar plate.In particular, a first side of the bipolar element forms an anode side of the electrolysis cell, and in particular, a second side of the bipolar element forms a cathode side of an immediately adjacent electrolysis cell. In particular, the first electrolysis cell and / or the second electrolysis cell can be designed as described in this context. In particular, at least some, advantageously at least a majority, and particularly advantageously all electrolysis cells of the electrolyzer device are at least substantially identical and / or of the same and / or an analogous design.In this context, “at least substantially identical” objects are to be understood as meaning, in particular, objects which are constructed in such a way that they can each fulfil a common function and, apart from manufacturing tolerances, differ in their construction at most by individual elements which are immaterial to the common function, and, advantageously, objects which, apart from manufacturing tolerances and / or within the scope of manufacturing technology possibilities, are identically designed, whereby identical objects are to be understood as meaning, in particular, objects which are symmetrical to one another.

[0011] The electrolyzer device preferably comprises a plurality, preferably a multiplicity, of electrochemical cells, in particular of at least substantially identical design. In particular, the first electrolysis cell and / or the second electrolysis cell can each be any electrochemical cell, in particular arranged at the edge or in the center, of an electrolysis cell stack, wherein in particular the terms "first" and "second" are not necessarily but merely possibly to be understood as descriptive of a sequence and / or arrangement. In particular, it is conceivable that the first electrolysis cell and / or the second electrolysis cell are arranged, in particular directly, adjacent or non-adjacent.Furthermore, it is conceivable that features described with respect to the first electrolysis cell and the second electrolysis cell apply to at least a majority and / or all electrolysis cells of the electrolysis cell stack or the electrolyzer. Advantageously, the electrolysis device comprises at least one electrolysis cell stack, in particular an electrolysis stack comprising a plurality, preferably a multiplicity, of electrolysis cells arranged in a stack. The electrolysis cell stack preferably comprises at least the first electrolysis cell and / or the second electrolysis cell.The electrolysis cell stack preferably has repeating units which comprise a plurality of different functional elements, advantageously different functional electrolysis cell stack elements, for example, in particular in the specified order, at least one bipolar plate and / or at least one sieve plate and / or perforated plate or the like and / or at least one gas diffusion layer, in particular an oxygen diffusion layer, advantageously a titanium felt and / or a membrane, advantageously a polymer electrolyte membrane, and / or a further gas diffusion layer, in particular a hydrogen diffusion layer, advantageously a carbon felt, and / or a compression buffer, in particular a compression pad, advantageously an expanded metal, comprising in particular a further sieve plate and / or perforated plate. In particular, an electrolysis cell extends from one bipolar plate to the next bipolar plate.The electrolysis cell stack can comprise any number of electrochemical cells, for example ten or 20 or 30 or 50 or 100 or 150 or 200 or more or less or any number in between. Advantageously, the electrolysis device has exactly one electrolysis cell stack. However, it is also conceivable for the electrolysis device to comprise a plurality of electrolysis cell stacks, in particular at least substantially identically designed or differently designed, at least some of which can be electrically and / or hydraulically connected in series and / or in series. Advantageously, the first electrolysis cell and the second electrolysis cell are arranged in a common electrolysis cell stack. However, it is also conceivable for the first electrolysis cell and the second electrolysis cell to be arranged in different cell stacks.

[0012] In particular, the main power supply is intended to supply at least the electrolysis cells of the electrolysis cell stack, preferably electrolysis cells of several electrolysis cell stacks, with current and / or voltage simultaneously and / or jointly. The electrolysis energy is intended in particular for use in the electrolysis process, in particular in the splitting of water. "Intended" should be understood in particular to mean specially programmed, designed and / or equipped. The fact that an object is intended for a specific function should be understood in particular to mean that the object fulfills and / or executes this specific function in at least one application and / or operating state.

[0013] The electrolysis cell stack, in particular a PEM cell stack, consists in particular of many individual electrolysis cells, which are preferably electrically connected in series. Several electrolysis cell stacks, in particular PEM cell stacks, can be electrically connected in series to form electrolysis cell stack rows in the electrolyzer. Several electrolysis cell stack rows can be electrically connected in parallel in the electrolyzer. Preferably, a measuring system is used for each electrolysis cell stack, which monitors, for example, the voltage of the individual electrolysis cells. A defect in a single electrolysis cell leads to the failure of the entire electrolysis cell stack. An electrolysis cell stack is therefore only as good as its worst individual electrolysis cell (PEM cell).Failures of electrolysis cell stacks can occur, for example, due to mechanical damage, leaks, excessively high electrolysis cell voltages, excessively low or excessively high electrolysis cell operating temperatures, or excessively rapid load changes of electrolysis cells. However, the most significant negative influence is that production tolerances and aging of the electrolysis cells can cause their voltage levels to vary at the same current. To achieve a beneficially long service life and / or to enable use in an electrolysis cell stack cascade even after replacing an "old" electrolysis cell stack with a new one, the voltage levels of all electrolysis cells must be kept as constant as possible. By balancing the electrolysis cells as required, maintaining the same voltage levels of the electrolysis cells in an electrolysis cell stack can be advantageously achieved.The advantage of balancing is that "bad" cells are subjected to less stress and "good" cells are subjected to more stress. This increases the overall efficiency and brings the end-of-life of all electrolysis cells in the electrolysis cell stack closer together. Consequently, the described measurement system not only ensures the safety of the electrolysis cell stacks but can also ensure that the cell voltages of the electrolysis cells in the electrolysis cell stacks are equalized.

[0014] It is conceivable that, to test algorithms for balancing the electrolysis cells, a simulation could be created in which every possible state is captured, thereby advantageously creating a basis for automatic operation of the electrolysis cell stack with the measuring system. This simulation could also consider all other sensors of the electrolysis cell stack for safety functions. The electrolysis cells in the simulation should be freely parameterizable so that the resulting software functionality can be used for various types of electrolysis cells, both in any number per electrolysis cell stack and in any arrangement of electrolysis cell stacks, as well as for defining and detecting various fault scenarios.If, for example, a fault occurs in or originates from one of the auxiliary power supplies, an effective safety measure can be implemented, especially if the auxiliary power supplies are bidirectional chargers, e.g., for electric cars, which are preferably connected together on the AC side. The bidirectional chargers can be conveniently switched off as soon as their input sides are disconnected from a supply voltage. Thus, the bidirectional chargers could be equipped with contactors on the input side, which are switched by the electrolyzer's system control system. This advantageously allows for a safety shutdown, e.g., in the event of an emergency stop.

[0015] The auxiliary power supplies are in particular designed differently and / or separately from the main power supply. In particular, the electrolyzer device can have more than two auxiliary power supplies. Of course, the electrolyzer device can comprise more than two electrolysis cells, each with its own associated auxiliary power supply. Preferably, the number of auxiliary power supplies per electrolysis cell stack corresponds to at least an even fraction of all electrolysis cells in the cell stack or even to the number of electrolysis cells in the cell stack. It is conceivable that individual auxiliary power supplies are assigned to a sub-stack of electrolysis cells in the electrolysis cell stack with more than one electrolysis cell and / or balance the sub-stack compared to further sub-stacks of electrolysis cells in the electrolysis cell stack, also with more than one electrolysis cell and preferably with an identical number of electrolysis cells as the sub-stack."Electrical unloading" is understood to mean, in particular, the withdrawal of electrical power, particularly from the respective associated electrolysis cell. "Electrical feeding" is understood to mean, in particular, the addition of electrical power, particularly to the respective associated electrolysis cell.

[0016] The electrolyzer device, in particular the electrolyzer and / or at least one electrolysis cell stack of the electrolyzer, has a control and / or regulating unit, e.g., an IC / microcontroller, which controls the balancing of the electrolysis cells, preferably in an automated manner, e.g., the current directions and current levels of the electrical supply and / or the electrical discharge. A "control and / or regulating unit" is to be understood, in particular, as a unit with at least one control electronics unit. "Control electronics" is to be understood, in particular, as a unit with a processor and a data memory. In particular, each electrolysis cell stack can have its own control and / or regulating unit, or a common control and / or regulating unit can be provided for a plurality of electrolysis cell stacks of the electrolyzer, preferably for all electrolysis cell stacks of the electrolyzer.In particular, the electrolysis cells each have voltage measuring points at which the cell voltage is measured and monitored. These voltage measuring points can be designed as individual voltage contact elements, as described in the German patent application with the publication number DE 10 2017 108439 A1, the disclosure of which is hereby incorporated in its entirety into this patent application. In particular, the control and / or regulating units can form at least part of a stack management system for electrolyzers, which is particularly similar in structure to a battery management system for accumulators. Alternatively, however, it is also conceivable that the control and / or regulating units (which are at least similar to battery management systems) are provided for a control system that is independent and / or autonomous, in particular from a control system of the electrolyzer. In particular, the auxiliary power supplies each form balancer modules.The balancer modules are provided, preferably in an automated manner, at least to balance the electrolysis cells with respect to one another by electrically supplying and / or unloading them, in particular by applying current. Preferably, all balancer modules of an electrolysis cell stack, preferably of an electrolysis cell stack row, are provided to jointly balance all electrolysis cells of the electrolysis cell stack, preferably of the electrolysis cell stack row, with respect to one another, in particular with the involvement of the associated control and / or regulating units, so that they preferably have at least substantially identical cell voltages during operation. The term “balancing electrolysis cells with respect to one another” should be understood in particular to mean that the electrolysis cells balanced with respect to one another have at least substantially identical cell voltages.In order to design the electrical relief and / or the electrical supply by the various auxiliary power supplies independently of one another and / or to avoid a short circuit on a BUS side, the auxiliary power supplies are preferably designed to be at least electrically separated from one another.

[0017] If the first electrolysis cell and the second electrolysis cell are electrically connected in series and / or if the auxiliary power supplies are provided to adapt the cell voltages of the individual electrolysis cells to one another, in particular to align them, by electrically relieving and / or electrically supplying the respective electrolysis cells, the service life and / or the overall efficiency of electrolyzers can advantageously be improved, in particular through the effects already described above. Alternatively, however, the first electrolysis cell and the second electrolysis cell could also be electrically connected in parallel. In particular, the cell voltages of the individual electrolysis cells are adapted to one another in such a way that their time factors, preferably their remaining service lives, are aligned.For this purpose, the cell voltages could also be deliberately kept at different values ​​in order to adjust the remaining lifetimes of “good” and “bad” cells to each other.

[0018] It is further proposed that the auxiliary power supplies are provided to draw power from an electrolysis cell with a cell voltage that is increased relative to a predetermined value by electrically unloading it. In this way, a cell voltage of a "poorer" electrolysis cell can advantageously be reduced, so that in particular the "poorer" electrolysis cell can be operated below the maximum voltage and the highest possible overall power of all electrolysis cells, e.g. those connected in series or parallel, can be achieved. In particular, the electrical unloading of the primary energy direction corresponds to the balancing function of the electrolyzer device according to the invention. The predetermined value can, for example, be an average value of all cell voltages of the electrolysis cells electrically connected in series, e.g. of the electrolysis cell stack, or an optimal value (e.g. electrolysis cell type-specific) for the cell voltage of the electrolysis cell.For example, a typical value for maximum cell voltages of PEM electrolysis cells could be around 2.5 V. For example, an optimal value for maximum cell voltages of PEM electrolysis cells could be between 1.75 V and 2.2 V, preferably around 2 V. However, other cell voltage values ​​are also conceivable and can depend in particular on individual cell characteristics. Preferably, the operation of the auxiliary power supplies / balancer modules is as independent as possible of the current load of the electrolyzer, the electrolysis cell stack and / or the main power supply. However, the level of influence can also increase or decrease with the current electrolysis power, so that a high power from the main power supply could minimize the benefit of the balancer modules. Preferably, the operation of the auxiliary power supplies / balancer modules is independent of the primary energy source or sink (the main power supply).Operation can occur at full power even if the electrolyzer / electrolysis cell stack is only running at minimum power. However, the electrolyzer / electrolysis cell stack must at least be in operation (with active peripherals) to balance the electrolysis cells. Therefore, hydrogen is always produced when the voltage applied to an electrolysis cell reaches a certain level—regardless of whether this is due to the main power supply or the auxiliary power supplies.

[0019] Additionally, it is proposed that the auxiliary power supplies be designed to supply power to an electrolysis cell with a cell voltage that is low relative to a predetermined value by means of electrical power. This advantageously allows for the electrolysis cells to have as uniform a service life as possible. In particular, the electrical power supply of the secondary energy direction corresponds to the balancing function of the electrolyzer device according to the invention.

[0020] Furthermore, it is proposed that the auxiliary power supplies be provided for actively balancing the electrolysis cells. This advantageously makes it possible to achieve high efficiency. Losses and / or waste heat can advantageously be kept as low as possible. In particular, with active balancing of the electrolysis cells, the energy taken from one or more electrolysis cells of the electrolyzer is fed back to other electrolysis cells of the electrolyzer or even to another electrolyzer or to the power grid. In contrast to the active balancing of electrolysis cells, there is an alternative to passive balancing of electrolysis cells. With passive balancing of electrolysis cells, for example, a load, e.g. a resistive load, could be operated in parallel as a sink on the electrolysis cell / cells whose cell voltage is too high.This could reduce the current flow through the electrolysis cell(s) and thus lower the cell voltage. For example, for passive balancing, in the simplest case, a resistor is connected in parallel with each electrolysis cell using a switch. The switches would then be controlled via digital outputs of a programmable logic controller, e.g., the control and / or regulation unit. In this case, the level of power drawn could be regulated by gradually connecting additional resistors connected in parallel to each electrolysis cell. The drawn energy would then be converted into (waste) heat.

[0021] Furthermore, it is proposed that the auxiliary power supplies be designed as bidirectional voltage converters. This enables a particularly advantageous balancing of electrolysis cells. Advantageously, the overall efficiency can be increased and / or the service life of individual electrolysis cells can be influenced as desired, e.g., homogenized if desired. If the cell voltage of one or more electrolysis cells needs to be reduced, the auxiliary power supplies designed as bidirectional voltage converters draw power from these electrolysis cells by operating them as a load in parallel with the electrolysis cells. The absorbed power is preferably fed into an AC power grid.Conversely, the auxiliary power supplies supply more power to the electrolysis cells, which have a relatively low voltage, in a controlled manner, in particular by operating them in parallel with the electrolysis cells as a power source, which, for example, draws the necessary power from the AC supply grid or other auxiliary power supplies that are currently providing electrical relief. If each electrolysis cell or several electrolysis cells are connected in series to an auxiliary power supply, they can be operated according to a desired characteristic curve and / or adjusted to the cell voltage of another electrolysis cell or a series of other electrolysis cells. In particular, the input and output of the respective balancer modules / auxiliary power supplies are galvanically isolated. With active balancing using bidirectional voltage converters from and to a common grid, power can be supplied to and taken from a single auxiliary power supply.

[0022] As an alternative to the bidirectional voltage converter to a common grid, active balancing can also be implemented using individual isolated voltage converters, unidirectionally to a common grid, or using isolated voltage converters, twice unidirectionally (quasi-bidirectional) to and from a common grid. In the case of isolated voltage converters connected unidirectionally to a common grid, a contactor or relay would be connected to each electrolysis cell and one (or several in parallel) voltage converters would be connected so that each is fed by the respective electrolysis cell. The voltage converter would have to have a voltage range on the input side corresponding to the electrolysis cell. The output of the voltage converter could be used as a source in any form, fed by the electrolysis cells / cell strings.To do this, it would have to be designed in such a way that the power delivered by the cells can be absorbed by a load. Alternatively, the load could be adapted accordingly. Depending on the application, this could be a stable voltage potential or a dynamically changing voltage potential. For example, this could be achieved by using a buffer made up of capacitors with a nominal voltage of 48 VDC and a downstream (feed-in) inverter through which the power is fed into the supply grid. Overloading of the voltage converters could be prevented, for example, by regulating the power input of the load. The switches and current limiting could possibly be omitted if the isolated voltage converter can be actively controlled. Uncontrolled devices are generally also power-limiting for technical reasons.In the case of isolated voltage transformers that are connected twice unidirectionally (quasi-bidirectionally) to and from the common network, a similar setup to the one described above is used, although in addition to the isolated voltage transformers of this design, isolated voltage transformers with opposite current directions would also be used. Thus, these voltage transformers would be connected together on the input side. The output of the voltage transformer of the previously described design would then also be the input of the opposite voltage transformer. The voltage range of the output of the "incoming" voltage transformer would then have to be within the range of the input of the "outgoing" voltage transformer, which would also be the voltage range of the electrolysis cell.In the case of bidirectional voltage converters to and from a common grid, one bidirectional voltage converter replaces the two isolated unidirectional voltage converters of the previously described design, which are used in opposite directions. Another alternative to all three previously described cases would be active balancing directly from one electrolysis cell to the other. However, this would require n. 2 (once unidirectional) or 2n 2 (quasi-bidirectional or bidirectional) switch is required to interconnect all outputs and / or inputs of the voltage converters, where n describes the number of electrolysis cells of the electrolyzer or the electrolysis cell stack.

[0023] If the bidirectional voltage converter is designed as a conventional bidirectional charger for electric vehicles with galvanically isolated input and output, e.g., as a bidirectional DC charger for electric vehicles with an AC grid connection for AC grid feed-in and AC grid supply, a simple design and / or cost-effective implementation can be advantageously enabled. Systems already developed for other fields can be advantageously used, thereby advantageously increasing overall efficiency. In particular, conventional isolated chargers for electric vehicles, whose DC voltage range is suitable for the application, can be used with little effort for PEM cell series if they are controllable (specifying voltage and current setpoints).Conventional bidirectional DC chargers for electrolysis cell stacks can preferably be used without significant modification if the voltage and / or current of the electrolysis cell stack are in ranges comparable to those used in electromobility. For application at the electrolysis cell level, additional devices are required, e.g., the connection of additional, equally bidirectional voltage converters that operate in the lower voltage range of electrolysis cells, particularly PEM cells (2 V vs. 120 V at currents of 100 A). Such voltage converters are commercially available and are used, for example, in data centers to power CPUs.

[0024] It is further proposed that the bidirectional voltage converter, in particular the bidirectional charger for electric cars, be electrically connected in series with at least one further bidirectional voltage converter. This advantageously enables the balancing of the electrolysis cells. This also advantageously allows for simple adaptation of the electrolyzer device to voltage and / or current ranges in electrolyzers. In particular, the electrolyzer device comprises a series connection of auxiliary power supplies, which are designed in particular as bidirectional voltage converters and thus form sources and sinks for electrical power, wherein each node in the series connection of the auxiliary power supplies is connected to a point, in particular a node, within an electrolysis cell series connection of the electrolysis cell stack / electrolyzer.

[0025] It is further proposed that the auxiliary power supplies be interconnected in such a way that they can at least partially supply power taken from one of the electrolysis cells to another of the electrolysis cells. This advantageously achieves high efficiency. In particular, the resulting relative difference in the load acting on the respective cells can be advantageously amplified. Advantageously, a particularly cost-effective balancing can be achieved. In particular, to implement this proposal, the electrolyzer device has an intermediate storage device, such as an intermediate circuit. The intermediate circuit can be implemented in the form of a DC network or an AC network (preferred). This implementation always results in two steps: e.g., from electrolysis cell stack A to the intermediate circuit network and from the intermediate circuit network to electrolysis cell stack B. If this is not desired, e.g.,Because conversion is only required once, each output of each auxiliary power supply per electrolysis cell stack would have to be electrically connected to every other electrolysis cell stack. While this would theoretically be technically feasible using switches, the number of switches required would increase exponentially with the number of electrolysis cell stacks in the electrolyzer. In particular, an AC supply network connected by the power supplier is preferable as an intermediate circuit, as this is inherently stabilized. This can then advantageously ensure that power is never fed back into the supply network. If a separate local intermediate circuit is to be constructed, it would have to be protected against overload, e.g., with a crowbar circuit.

[0026] Alternatively or additionally, power supplies, especially auxiliary power supplies, are provided for passively balancing the electrolysis cells. This can create a cost-effective alternative that requires little or no electronics.

[0027] In this context, it is also proposed that the power supplies, in particular the auxiliary power supplies, each comprise a switchable load resistor or a plurality of parallel-connected, separately switchable load resistors. This advantageously enables passive balancing. In particular, the term "auxiliary power supply" at first glance seems unsuitable to describe a switchable load resistor, since balancing neither involves dissipating power into nor taking power from the grid. Nevertheless, for the purposes of these documents, an auxiliary power supply should preferably be understood as a switchable load resistor that serves to draw power by heating.

[0028] It is additionally proposed that at least one of the auxiliary power supplies is assigned to at least one further, e.g. a third, electrolysis cell, which is electrically connected in series with the other electrolysis cell assigned to this auxiliary power supply. This advantageously creates a cost-effective balancing option, particularly for large systems. In particular, the auxiliary power supply, or preferably all auxiliary power supplies, are assigned to a sub-stack of electrolysis cells. Although this no longer allows individual cell balancing to be achieved, subgroups (sub-stacks) of electrolysis cells can still advantageously be balanced relative to one another. For example, one auxiliary power supply can be used per electrolysis cell stack of the electrolyzer. In particular, a package of electrolysis cells can be selected such that widespread DC voltages, such as approximately 12 V, approximately 48 V, approximately 96 V, approximately 144 V, etc., are dropped across the auxiliary power supplies.In particular, in the electrolysis device, a minimum number of auxiliary power supplies per entire series connection of electrolysis cells is two.

[0029] It is further proposed that the first electrolysis cell be part of a first electrolysis cell stack and that the second electrolysis cell be part of a second electrolysis cell stack, wherein the auxiliary power supplies are provided to balance the electrolysis cell stacks with respect to one another by, in particular independently of one another, electrically relieving and / or electrically feeding the respective electrolysis cell stacks. This can advantageously improve the service life of electrolyzers. Advantageously, aging of different electrolysis cell stacks of the electrolyzer can be equalized. Advantageously, the overall efficiency of all electrolysis cell stacks in an electrolyzer can be improved. Advantageously, operation of the electrolyzer can be enabled in which all electrolysis cell stacks of the electrolyzer reach the end of their service life at the same time.

[0030] Furthermore, an electrolyzer, in particular an electrolysis system, comprising the electrolyzer device and a method for operating the electrolyzer device are proposed, wherein the electrolysis cells are balanced with respect to one another by, in particular independently of one another, electrically unloading and / or electrically feeding the respective electrolysis cell by means of at least one first auxiliary power supply, which is assigned to at least the first electrolysis cell, and by means of at least one second auxiliary power supply, which is assigned to at least the second electrolysis cell. This can advantageously improve the service life and / or overall efficiency of electrolyzers.

[0031] The electrolyzer device according to the invention, the electrolyzer according to the invention, and the method according to the invention are not intended to be limited to the application and embodiment described above. In particular, the electrolyzer device according to the invention, the electrolyzer according to the invention, and the method according to the invention may have a number of individual method steps, elements, components, and units that differs from the number stated herein to fulfill a function described herein.

[0032] Drawings

[0033] Further advantages will become apparent from the following description of the drawings. The drawings illustrate six exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into further meaningful combinations.

[0034] They show:

[0035] Fig. 1 schematically shows an electrolyzer with an electrolyzer device,

[0036] Fig. 2 is a schematic representation of one of the electrolysis cell stacks of the electrolyzer,

[0037] Fig. 3 is a schematic diagram of a part of the electrolyzer with the electrolyzer device,

[0038] Fig. 4 is a schematic flow diagram of a method for operating the electrolyzer device,

[0039] Fig. 5 is a schematic diagram of a part of the electrolyzer with an alternative electrolyzer device, Fig. 6 is a schematic diagram of a part of the electrolyzer with a further alternative electrolyzer device,

[0040] Fig. 7 is a schematic diagram of a part of the electrolyzer with a second further alternative electrolyzer device,

[0041] Fig. 8 is a schematic circuit diagram of a part of the electrolyzer with a third further alternative electrolyzer device and Fig. 9 is a schematic circuit diagram of a part of the electrolyzer with a fourth alternative electrolyzer device.

[0042] Description of the embodiments

[0043] Fig. 1 schematically shows an electrolyzer 30a. The electrolyzer 30a forms an electrolysis system. The electrolyzer 30a is embodied, for example, as a proton exchange membrane electrolyzer. However, the invention described here is also applicable to other electrolyzer types. The electrolyzer 30a comprises electrolysis cell stacks 26a, 28a (see also Fig. 2). The electrolysis cell stacks 26a, 28a are electrically interconnected in electrolysis cell stack rows 34a, 36a. The electrolysis cell stack rows 34a, 36a are also referred to as cascades. For example, each of the electrolysis cell stack rows 34a, 36a of the electrolyzer 30a comprises five electrolysis cell stacks 26a, 28a. By way of example, the electrolyzer 30a, in particular the electrolysis system, comprises eighteen electrolysis cell stack rows 34a, 36a.

[0044] For example, a 10-megawatt electrolysis system is implemented using the proposed numbers of electrolysis cell stacks 26a, 28a. Numbers of electrolysis cell stacks 26a, 28a or electrolysis cell stack rows 34a, 36a that deviate from the exemplary numbers, either upwards or downwards, are of course also conceivable. The electrolysis cell stacks 26a, 28a of an electrolysis cell stack row 34a are electrically connected in series. The electrolysis cell stack rows 34a, 36a are electrically connected in parallel. The individual electrolysis cell stacks 26a, 28a of the electrolysis system can be designed to be interchangeable or replaceable.

[0045] The electrolyzer 30a has an electrolyzer device 32a. Fig. 2 shows a schematic representation of one of the electrolysis cell stacks 26a of the electrolyzer 30a with the electrolyzer device 32a in a side view. Components such as a fluid supply, a housing, and the like of the electrolyzer 30a are not shown in Fig. 2. However, the electrolyzer 30a can of course include the like. The electrolyzer device 32a has a first electrolysis cell 10a. The electrolyzer device 32a has a second electrolysis cell 12a. In the present case, the electrolysis cell stack 26a has a plurality of electrolysis cells 10a, 12a, of which only twelve are shown schematically for reasons of clarity and not all of which are provided with reference numerals. Furthermore, the electrolysis cells 10a, 12a of the electrolysis cell stack 26a are not shown to scale in Fig. 2.In particular, the electrolysis cells 10a, 12a of the electrolysis cell stack 26a can be significantly flatter than in the schematic representation of Fig. 2. For example, the electrolysis cell stack 26a can comprise 20 or 30 or 50 or 100 or 150 or 200 electrolysis cells 10a, 12a. The first electrolysis cell 10a and the second electrolysis cell 12a are electrically connected in series. All electrolysis cells 10a, 12a of the electrolysis cell stack 26a are electrically connected in series. All electrolysis cells 10a, 12a belonging to a common electrolysis cell stack row 34a, 36a are electrically connected in series.

[0046] The electrolysis cell stack 26a has a first end plate 38a and a second end plate 40a. The first end plate 38a and the second end plate 40a delimit the electrolysis cells 10a, 12a of the electrolysis cell stack 26a on opposite sides of the electrolysis cell stack 26a. The end plates 38a, 40a are connected to one another, for example, by means of connecting struts (not shown) and apply a compressive force to the electrolysis cells 10a, 12a of the electrolysis cell stack 26a, which in particular counteracts pressure due to the formation of hydrogen gas and / or oxygen gas, or in particular ensures or at least contributes to a tight seal between the pressed-together electrolysis cells 10a, 12a and / or a tight seal between the respective electrolysis cells 10a, 12a. The electrolysis cell stack 26a has connection elements 42a, 44a for connection to a power supply.The power supply is provided by a main power supply 14a of the electrolyzer device 32a (see Fig. 3). In a normal operating state, the electrolysis cell stack 26a is supplied with electrical power via the connection elements 42a, 44a. A total voltage is applied between a frontmost electrolysis cell 10a, which is particularly adjacent to the first end plate 38a, and a rearmost electrolysis cell, which is particularly adjacent to the second end plate 40a. In the normal operating state, a voltage of between approximately 1 V and approximately 2.5 V is applied to individual electrolysis cells 10a, 12a of the electrolysis cell stack 26a.

[0047] The electrolyzer device 32a has contact elements 46a, 48a (see Fig. 2), which are different from a connection element 42a, 44a for the main power supply 14a and of which, in particular, one is at an anode potential and one is at a cathode potential of a respective corresponding electrolysis cell 10a, 12a. Two contact elements 46a, 48a are assigned to each individual electrolysis cell 10a, 12a. In particular, the contact elements 46a, 48a assigned to a specific electrolysis cell 10a, 12a are each a contact element 46a of the corresponding electrolysis cell 10a and a contact element 48a of an immediately adjacent other electrolysis cell 12a.In particular, in this way, a specific contact element 46a, 48a is assigned to two directly adjacent electrolysis cells 10a, 12a, wherein the corresponding contact element 46a, 48a is at an anode potential of one electrolysis cell 10a, which corresponds to a cathode potential of the other electrolysis cell 12a. For example, in the present case, the contact element 46a and the further contact element 48a are assigned to the first electrolysis cell 10a. Furthermore, in the present case, the further contact element 48a is also assigned to the second electrolysis cell 12a. The contact elements 46a, 48a are accessible from an exterior of the electrolysis cell stack 26a. The contact elements 46a, 48a are arranged outside an active interior of the electrolysis cells 10a, 12a and / or outside an active interior of the electrolysis cell stack 26a.The contact elements 46a, 48a allow electrical contact of the electrolysis cells 10a, 12a, in particular their anode and their cathode.

[0048] Figure 3 shows a schematic circuit diagram of a portion of the electrolyzer 30a with the electrolyzer device 32a. The electrolyzer device 32a has the main power supply 14a. The main power supply 14a is intended to jointly supply the first electrolysis cell 10a and the second electrolysis cell 12a with electrical energy. The main power supply 14a is intended to supply all electrolysis cells 10a, 12a of the electrolysis cell stack 26a with electrolysis energy. The main power supply 14a is intended to supply all electrolysis cells 10a, 12a of the electrolyzer 30a with electrolysis energy. The main power supply 14a is connected to a supply network 54a.

[0049] The electrolyzer device 32a has a first auxiliary power supply 16a. The first auxiliary power supply 16a is assigned to the first electrolysis cell 10a. The electrolyzer device 32a has a second auxiliary power supply 18a. The second auxiliary power supply 18a is assigned to the second electrolysis cell 12a. The respective electrolysis cells 10a, 12a each consist of the same electrolysis cell stack 26a. In the exemplary embodiment of Figures 1 to 3, each additional electrolysis cell is assigned precisely one separate auxiliary power supply. The auxiliary power supplies 16a, 18a are provided to balance the electrolysis cells 10a, 12a with respect to one another by independently electrically relieving the respective electrolysis cell 10a, 12a. The auxiliary power supplies 16a, 18a are intended to balance the electrolysis cells 10a, 12a by independently supplying electrical power to the respective electrolysis cells 10a, 12a.

[0050] The auxiliary power supplies 16a, 18a are provided to equalize the cell voltages of the individual electrolysis cells 10a, 12a by electrically relieving and / or electrically supplying the respective electrolysis cells 10a, 12a. The auxiliary power supplies 16a, 18a are each provided to draw power from the respective associated electrolysis cell 10a, 12a by electrically relieving the load if the cell voltage is increased relative to a predetermined value. The auxiliary power supplies 16a, 18a are each provided to supply power to the respective associated electrolysis cell 10a, 12a by electrically supplying the load if the cell voltage is reduced relative to the predetermined value. The value specified for the cell voltage can be adjustable, for example, via a control and / or regulating unit 50a of the electrolyzer device 32a.The auxiliary power supplies 16a, 18a can also be designed as, for example, modularly expandable, multi-channel balancers with galvanically isolated channels for each electrolysis cell 10a, 12a connected to the multi-channel balancer (see Fig. 2).

[0051] The auxiliary power supplies 16a, 18a are provided for actively balancing the electrolysis cells 10a, 12a. The auxiliary power supplies 16a, 18a are each designed as bidirectional voltage converters 20a. The bidirectional voltage converter 20a is electrically connected in series with further bidirectional voltage converters 22a of the electrolyzer device 32a. The auxiliary power supplies 16a, 18a, in particular the bidirectional voltage converters 20a, are interconnected in such a way that they can at least partially supply a power drawn from one of the electrolysis cells 10a to another of the electrolysis cells 12a. The respective currents can be transferred between the electrolysis cells 10a, 12a by active and passive components, such as semiconductor components. Alternatively, a structure using a multiplexer, which leads each electrolysis cell 10a, 12a to a common DC-DC converter, is also conceivable.The auxiliary power supplies 16a, 18a are connected to a common network 52a. The common network 52a can be formed by an intermediate circuit, e.g., an AC supply network, in particular the supply network 54a, to which the main power supply 14a is also connected. Fig. 4 shows a schematic flow diagram of a method for operating the electrolyzer device 32a. In a method step 56a, the electrolysis cells 10a, 12a are jointly supplied with electrolysis energy by the main power supply 14a. In at least one further method step 58a, the electrolysis cells 10a, 12a in electrolysis operation are balanced with one another by an independent electrical unloading by means of the respectively assigned auxiliary power supplies 16a, 18a, in particular such that the cell voltages of the electrolysis cells 10a, 12a are equalized to one another by the electrical unloading.In at least one further or alternative method step 60a, the electrolysis cells 10a, 12a in electrolysis operation are balanced with one another by an independent electrical supply via the respectively assigned auxiliary power supplies 16a, 18a, in particular such that the cell voltages of the electrolysis cells 10a, 12a are equalized to one another by the electrical supply. The power for the electrical supply is taken either directly from the supply network 54a or from all other auxiliary power supplies of the electrolyzer device 32a (the power source is then, for example, a common BUS), which momentarily electrically relieves another electrolysis cell of the electrolyzer device 32a (if necessary via an intermediate circuit). In at least one further method step 62a, the electrolysis cells 10a, 12a of the electrolyzer device 32a are operated with the respective desired cell voltages, for example, essentially identical cell voltages.For example, a so-called "overshoot" of the cell voltage of a "good" electrolysis cell may be necessary to reach a common EOL (end-of-life), or vice versa for a "bad" electrolysis cell.

[0052] Figures 5 to 9 show five further embodiments of the invention. The following descriptions and the drawings are essentially limited to the differences between the embodiments, whereby with regard to components with the same designation, in particular with regard to components with the same reference numerals, reference can in principle also be made to the drawings and / or the description of the other embodiments, in particular Figures 1 to 4. To distinguish the embodiments, the letter a is placed after the reference numerals of the embodiment in Figures 1 to 4. In the embodiments in Figures 5 to 9, the letter a is replaced by the letters b to f.

[0053] Figure 5 shows an alternative electrolyzer device 32b with at least one electrolysis cell stack 26b comprising electrolysis cells 10b, 12b. The alternative electrolyzer device 32b has a first auxiliary power supply 16b. The first auxiliary power supply 16b is assigned to the first electrolysis cell 10b. The alternative electrolyzer device 32b has a second auxiliary power supply 18b. The second auxiliary power supply 18b is assigned to the second electrolysis cell 12b. The alternative electrolyzer device 32b has a further electrolysis cell 76b. The first auxiliary power supply 16b is assigned to the further electrolysis cell 76b. The respective electrolysis cells 10b, 12b, 76b each consist of the same electrolysis cell stack 26b. The first auxiliary power supply 16b, which is assigned to the further electrolysis cell 76b, is electrically connected in series with the second auxiliary power supply 18b, which is assigned to the second electrolysis cell 12b.In the embodiment of Figure 5, additional electrolysis cells can each be assigned to one of the auxiliary power supplies 16b, 18b. Preferably, the same number of electrolysis cells 10b, 12b, 76b are each assigned to an auxiliary power supply 16b, 18b. The electrolysis cells 10b, 12b, 76b assigned to one of the auxiliary power supplies 16b, 18b each form an electrolysis cell balance pack 64b, 66b. The auxiliary power supplies 16b, 18b are provided to balance the electrolysis cells 10b, 12b, 76b of the respective electrolysis cell balance packs 64b, 66b by independently electrically relieving the respective electrolysis cell balance packs 64b, 66b. The auxiliary power supplies 16b, 18b are provided to balance the electrolysis cells 10b, 12b, 76b of the respective electrolysis cell balance packs 64b, 66b by independently supplying electrical power to the respective electrolysis cell balance packs 64b, 66b.Figure 6 shows a further alternative electrolyzer device 32c with a plurality of electrolysis cell stacks 26c, 28c, each having a plurality of electrolysis cells 10c, 12c. The first electrolysis cell 10c is part of the first electrolysis cell stack 26c. The second electrolysis cell 12c is part of the second electrolysis cell stack 28c. The further alternative electrolyzer device 32c has a first auxiliary power supply 16c. The first auxiliary power supply 16c is assigned to the first electrolysis cell stack 26c. The further alternative electrolyzer device 32c has a second auxiliary power supply 18c. The second auxiliary power supply 18c is assigned to the second electrolysis cell stack 28c. In the embodiment of Figure 6, further electrolysis cell stacks 68c can be assigned to further auxiliary power supplies 70c. Preferably, exactly one electrolysis cell stack 26c, 28c, 68c is assigned to exactly one auxiliary power supply 16c, 18c, 70c.However, it is also conceivable for multiple electrolysis cell stacks 26c, 28c, 68c to be assigned to a common auxiliary power supply 16c, 18c, 70c. However, the number of electrolysis cell stacks 26c, 28c, 68c assigned to an auxiliary power supply 16c, 18c, 70c in the further alternative electrolyzer device 32c should then always be the same. The auxiliary power supplies 16c, 18c, 70c are provided to balance the electrolysis cell stacks 26c, 28c, 68c by independently electrically relieving the respective electrolysis cell stacks 26c, 28c, 68c. The auxiliary power supplies 16c, 18c, 70c are provided to balance the electrolysis cell stacks 26c, 28c, 68c by independently supplying electrical power to the respective electrolysis cell stacks 26c, 28c, 68c.

[0054] Figure 7 shows a second further alternative electrolyzer device 32d with a plurality of electrolysis cell stacks 26d, each having a plurality of electrolysis cells 10d, 12d. The second further alternative electrolyzer device 32d has a first auxiliary power supply 16d. The first auxiliary power supply 16d is assigned to the first electrolysis cell 10d. The second further alternative electrolyzer device 32d has a second auxiliary power supply 18d. The second auxiliary power supply 18d is assigned to the second electrolysis cell 12d. The exemplary embodiment shown in Figure 7 essentially corresponds to the exemplary embodiment of Figures 1 to 4 with the exception of the design of the auxiliary power supplies 16d, 18d. The auxiliary power supplies 16d, 18d are designed as a combination of two unidirectional voltage converters 72d arranged opposite one another and galvanically isolated from one another, which are connected to a common network 52d.This advantageously allows a quasi-bidirectionality of the voltage converter to be achieved.

[0055] Figure 8 shows a third further alternative electrolyzer device 32e with a plurality of electrolysis cell stacks 26e, each having a plurality of electrolysis cells 10e, 12e. The third further alternative electrolyzer device 32e has a first auxiliary power supply 16e. The first auxiliary power supply 16e is assigned to the first electrolysis cell 10e. The third further alternative electrolyzer device 32e has a second auxiliary power supply 18e. The second auxiliary power supply 18e is assigned to the second electrolysis cell 12e. The electrolysis cell stack 26e shown in Figure

[0056] The embodiment shown in Figure 8 essentially corresponds to the embodiment shown in Figures 1 to 4, with the exception of the configuration of the auxiliary power supplies 16e, 18e. The auxiliary power supplies 16e, 18e are each designed as a unidirectional voltage converter 74e, which is connected to a common network 52e. As a result, balancing of the cell voltages of the electrolysis cells 10e, 12e can only be achieved by electrically unloading (or merely by electrically supplying the voltage when reversing the unidirectional voltage converter 74e). The opposite direction is not available in this embodiment.

[0057] Figure 9 shows a fourth further alternative electrolyzer device 32f with a plurality of electrolysis cell stacks 26f, each having a plurality of electrolysis cells 10f, 12f. The fourth further alternative electrolyzer device 32f has a first auxiliary power supply 16f. The first auxiliary power supply 16f is assigned to the first electrolysis cell 10f. The fourth further alternative electrolyzer device 32f has a second auxiliary power supply 18f. The second auxiliary power supply 18f is assigned to the second electrolysis cell 12f. The auxiliary power supplies 16f, 18f are each provided for passively balancing the electrolysis cells 10f, 12f. The auxiliary power supplies 16f, 18f are not provided for relieving load by dissipating power into a grid. The auxiliary power supplies 16f, 18f are not provided for feeding power from a grid. The auxiliary power supplies 16f, 18f are formed solely by electrical resistors.The auxiliary power supplies 16f, 18f each comprise a switchable load resistor 24f or a plurality of parallel-connected, separately switchable load resistors 24f, 24'f, 24“f.

[0058] Reference symbol

[0059] 10 First electrolysis cell

[0060] 12 Second electrolysis cell

[0061] 14 Main power supply

[0062] 16 First auxiliary power supply

[0063] 18 Second auxiliary power supply

[0064] 20 Bidirectional voltage converter

[0065] 22 Additional bidirectional voltage converter

[0066] 24 Load resistance

[0067] 26 First electrolysis cell stack

[0068] 28 Second electrolysis cell stack

[0069] 30 electrolyzer

[0070] 32 Electrolyzer device

[0071] 34 electrolysis cell stack series

[0072] 36 electrolysis cell stack series

[0073] 38 End plate

[0074] 40 End plate

[0075] 42 connecting element

[0076] 44 connecting element

[0077] 46 Contact element

[0078] 48 contact element

[0079] 50 Control and / or regulation unit

[0080] 52 Common Network

[0081] 54 Supply network

[0082] 56 Process step

[0083] 58 Process step

[0084] 60 process steps

[0085] 62 process steps

[0086] 64 electrolysis cell balance package

[0087] 66 Electrolysis cell balance pack Additional electrolysis cell stack Additional auxiliary power supply Combination of two unidirectional voltage converters Unidirectional voltage converter Additional electrolysis cell

Claims

Claims 1 . Electrolyzer device (32a-f) with at least one first electrolysis cell (10a-f), with at least one second electrolysis cell (12a-f), and with at least one main power supply unit (14a-f), which is at least intended to supply the first electrolysis cell (10a-f) and the second electrolysis cell (12a-f) jointly with electrical energy, in particular electrolysis energy, characterized by at least one first auxiliary power supply unit (16a-f), which is assigned to the first electrolysis cell (10a-f), and at least one second auxiliary power supply unit (18a-f), which is assigned to the second electrolysis cell (12a-f), wherein the auxiliary power supplies (16a-f, 18a-f) are intended to balance the electrolysis cells (10a-f, 12a-f) with one another by electrically relieving and / or electrically feeding the respective electrolysis cell (10a-f, 12a-f).

2. Electrolyzer device (32a-f) according to claim 1, characterized in that the first electrolysis cell (10a-f) and the second electrolysis cell (12a-f) are electrically connected in series.

3. Electrolyzer device (32a-f) according to claim 1 or 2, characterized in that the auxiliary power supplies (16a-f, 18a-f) are provided to adapt the cell voltages of the individual electrolysis cells (10a-f, 12a-f) to one another, in particular to equalize them to one another, by electrically relieving and / or electrically feeding the respective electrolysis cells (10a-f, 12a-f).

4. Electrolyzer device (32a-f) according to one of the preceding claims, characterized in that the auxiliary power supplies (16a-f, 18a-f) are provided to draw power from an electrolysis cell (10a-f, 12a-f) with a cell voltage increased relative to a predetermined value by electrical unloading.

5. Electrolyzer device (32a-d) according to one of the preceding claims, characterized in that the auxiliary power supplies (16a-d, 18a-d) are provided to supply power to an electrolysis cell (10a-d, 12a-d) with a cell voltage that is low relative to a predetermined value by means of the electrical supply.

6. Electrolyzer device (32a-f) according to one of the preceding claims, characterized in that the auxiliary power supplies (16a-f, 18a-f) are provided for actively balancing the electrolysis cells (10a-f, 12a-f).

7. Electrolyzer device (32a-c) according to one of the preceding claims, in particular according to claim 6, characterized in that the auxiliary power supplies (16a-c, 18a-c) are each designed as bidirectional voltage converters (20a-c).

8. Electrolyzer device (32a-c) according to claim 7, characterized in that the bidirectional voltage converter (20a-c) is designed as a conventional bidirectional charger for electric cars, the input and output of which are galvanically isolated.

9. Electrolyzer device (32a-c) according to claim 7 or 8, characterized in that the bidirectional voltage converter (20a-c) is electrically connected in series with at least one further bidirectional voltage converter (22a-c).

10. Electrolyzer device (32a-d) according to one of the preceding claims, in particular according to one of claims 6 to 9, characterized in that the auxiliary power supplies (16a-d, 18a-d) are interconnected in such a way that they can at least partially supply a power which is taken from one of the electrolysis cells (10a-d) to another of the electrolysis cells (12a-d).

11. Electrolyzer device (32f) according to one of claims 1 to 4, characterized in that the auxiliary power supplies (16f, 18f) are provided for passive balancing of the electrolysis cells (10f, 12f).

12. Electrolyzer device (32f) according to claim 11, characterized in that the auxiliary power supplies (16f, 18f) each comprise a switchable load resistor (24f) or a plurality of parallel-connected, separately switchable load resistors (24f, 24'f, 24"f).

13. Electrolyzer device (32b; 32c) according to one of the preceding claims, characterized in that at least one of the auxiliary power supply units (16b, 18b; 16c, 18c) is associated with at least one further electrolysis cell (76b; 76c), which is electrically connected in series with the other electrolysis cell (10b, 12b; 10c, 12c) associated with this auxiliary power supply unit (16b, 18b; 16c, 18c).

14. Electrolyzer device (32c) according to one of the preceding claims, characterized in that the first electrolysis cell (10c) is part of a first electrolysis cell stack (stack, 26c) and that the second electrolysis cell (12c) is part of a second electrolysis cell stack (stack, 28c), wherein the auxiliary power supplies (16c, 18c) are provided to balance the electrolysis cell stacks (26c, 28c) by, in particular independent of one another, electrical unloading and / or electrical feeding of the respective electrolysis cell stacks (26c, 28c).

15. Electrolyzer (30a-f), in particular electrolysis plant, with an electrolyzer device (32a-f) according to one of the preceding claims.

16. A method for operating an electrolyzer device (32a-f), in particular according to one of the preceding claims, with at least one first electrolysis cell (10a-f), with at least one second electrolysis cell (12a-f), and with at least one main power supply (14a-f) which supplies the first electrolysis cell (10a-f) and the second electrolysis cell (12a-f) together with electrical energy, in particular electrolysis energy, characterized in that the electrolysis cells (10a-f, 12a-f) are balanced with respect to one another by electrically relieving and / or electrically feeding the respective electrolysis cell (10a-f, 12a-f) by means of at least one first auxiliary power supply (16a-f) which is assigned to the first electrolysis cell (10a-f), and by means of at least one second auxiliary power supply (18a-f) which is assigned to the second electrolysis cell (12a-f).

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