Method for producing electrolysis modules and protection unit therefor

Abstract

The invention relates to a method for producing an electrolysis module (20) for an electrolysis system (10) having a plurality of electrolysis modules (20), wherein a plurality of electrolysis cells (12), which are designed to be subjected to an electrical electrolysis current (48) during routine operation in order to carry out electrolysis of a substance arranged in a reaction space of the electrolysis cells (12), are mechanically combined to form the electrolysis module (20), wherein electrode connections of the electrolysis cells (12) are electrically connected to one another and to module connections (28) of the electrolysis module (20) in a predetermined electrical circuit. According to the invention, the electrolysis cells (12) are classified with respect to at least one electrical parameter before being combined to form the electrolysis module (20), by the at least one parameter of each electrolysis cell (12) being detected by means of a measuring apparatus. Each electrolysis cell (12) is assigned to one of a plurality of cell classes depending on a detected value of the at least one parameter. Only electrolysis cells (12) assigned to a single cell class are used to produce the electrolysis module (20).

Description

[0001] Description

[0002] Method for producing electrolysis modules and protective unit therefor

[0003] The invention relates to a method for producing an electrolysis module for an electrolysis system having a plurality of electrolysis modules, wherein a plurality of electrolysis cells, which are designed to be subjected to an electrical electrolysis current during intended operation in order to carry out electrolysis of a substance arranged in a reaction chamber of the electrolysis cells, are mechanically combined to form the electrolysis module, wherein electrode terminals of the electrolysis cells are electrically connected to one another and to module terminals of the electrolysis module in a predetermined electrical circuit. Furthermore, the invention relates to a protection unit for an electrolysis module of an electrolysis system having a plurality of electrolysis modules.Furthermore, the invention relates to a protective device for an electrolysis system having a plurality of electrolysis modules electrically connected in series, with a plurality of protective units, wherein each of the electrolysis modules is electrically coupled to a respective protective unit, at least one electrical energy source for supplying the protective units with electrical energy, and a control unit for individually controlling the protective units. Finally, the invention relates to an electrolysis system having a plurality of electrolysis modules electrically connected in series, and a protective device electrically coupled to the electrolysis modules.

[0004] Electrolysis systems, protective devices, protective units for protective devices and methods for manufacturing electrolysis modules are extensively known in the state of the art, so that in principle there is no need for separate printed evidence for this.

[0005] Generic electrolysis cells and electrolysis systems, in particular for the electrolysis of water to hydrogen and oxygen, are extensively known in the prior art, for example from DE 197 29 529 CI. The basic function of electrolysis, in particular water electrolysis, is known to the person skilled in the art, which is why detailed explanations thereof are omitted here.

[0006] Electrolysis systems which have a single electrolysis module, but in particular a large number of electrolysis modules which are generally at least partially electrically connected in series, serve, among other things, to produce substances which can preferably be used on an industrial scale, for example hydrogen in the case of water electrolysis, carbon monoxide in the case of carbon dioxide electrolysis or the like. For this purpose, at least two module connections of a respective electrolysis module are supplied with a suitable small electrical direct voltage which can be in the range of a few volts. Depending on the amount of material to be provided by the electrolysis, a corresponding electrical direct current is provided by an electrolysis energy source as the electrolysis current. In the case of electrolysis modules connected in series, this direct current flows through all of the electrolysis modules connected in series.The series circuit is electrically coupled to the electrolysis energy source. However, it is also possible to connect electrolysis modules not only in series, but also, at least partially, in parallel.

[0007] Particularly in aqueous electrolysis, such as chlorine / alkali electrolysis, PEM electrolysis or the like, a membrane is often provided for the respective electrolysis cells contained in the electrolysis modules, which membrane separates respective reaction chambers or respective reaction areas of a respective electrolysis cell, in which respective electrodes are arranged. A catalyst is often arranged on such a membrane in order to enable or accelerate the electrolysis process. The electrolysis is usually brought about by the electrodes of a respective electrolysis cell being subjected to the electrolysis current or a suitable electrical direct voltage, also called cell voltage, during normal operation.

[0008] One of the things that proves to be at least partially critical for a particular electrolysis cell is a transition from or to an operating state that differs from the intended operating state for carrying out electrolysis. This applies in particular to starting up the electrolysis cell or the electrolysis module of the electrolysis system, as well as shutting down the electrolysis cell or the electrolysis module of the electrolysis system. Particularly during shutting down after intended operation, residual substances, in particular residual gases, may still be present in the electrolysis cell, which may under certain circumstances lead to fuel cell functionality occurring in the electrolysis cell. However, this can cause irreversible damage to the electrolysis cell, which is why fuel cell functionality should be avoided at all costs.For this purpose, it is known to apply a protective voltage, also called polarization voltage, to the electrolysis cell outside of its intended operation. This voltage is selected so that the fuel cell functionality can be largely avoided. For a single electrolysis cell for electrolyzing water, the protective voltage can be approximately 1.25 V, for example. Once the electrolysis cell has cooled down sufficiently and residual gases have been removed, the protective voltage can be deactivated.

[0009] It has been shown that electrolysis cells age differently from one another and / or can have differing characteristics. This can be particularly problematic when electrolysis cells are connected in series and the protective voltage is to be provided by a voltage applied to the series circuit. Due to the different aging or characteristics of the individual electrolysis cells connected in series, it can happen that the voltage applied to the series circuit is not distributed evenly between all of the cells connected in series. It is therefore necessary to choose a high enough electrical voltage for the series circuit that the protective voltage can still be reliably achieved for the most unfavorable electrolysis cell.However, this results in the other cells being subjected to a correspondingly high voltage, which can be significantly higher than their required protective voltage, so they continue to operate in electrolysis mode. Therefore, it is common practice to purge with nitrogen, particularly to prevent an explosive mixture in these electrolysis cells.

[0010] From EP 3 982 501 A1, it is also known to apply a protective voltage to each electrolysis cell individually. However, providing the respective protective voltages for the electrolysis cells and the associated essentially constant direct currents prove to be comparatively complex.

[0011] Depending on the manufacturer, the production batch and / or the like, electrolysis cells can have quite different properties, particularly with regard to the protective function against fuel cell operation.

[0012] The invention is based on the object of reducing the effort required for a reliable protective function to prevent fuel cell operation of a respective electrolysis cell. Furthermore, the invention is based on the object of specifying a corresponding method, a protective unit, a corresponding protective device, and a corresponding electrolysis system.

[0013] With regard to a generic method, the invention proposes in particular that the electrolysis cells are classified with regard to at least one, preferably electrical, parameter before being combined to form the electrolysis module, by detecting the at least one parameter of a respective electrolysis cell by means of a measuring device, the respective electrolysis cell is assigned to one of several cell classes depending on a detected value of the at least one parameter, and only electrolysis cells which are assigned to a single cell class are used to produce the electrolysis module.

[0014] With regard to a generic protective unit, the invention proposes in particular that the electrolysis module is produced according to the invention, wherein the electrolysis module has at least two connection contacts for electrical connection to respective module connections of the electrolysis module, at least two connection connections for electrical connection to an electrical energy source, and a controllable electrical energy converter which is electrically coupled to the at least two connection connections and the connection contacts and which is designed to supply the electrolysis module with a direct current as a module protection current in an operating state which is different from the intended electrolysis operation.

[0015] With regard to a generic protective device, the invention proposes in particular that the protective units are designed according to the invention.

[0016] With regard to a generic electrolysis system, the invention particularly proposes that the protective device is designed according to the invention. The invention is based, inter alia, on the idea that by forming modules with essentially very similar properties with regard to undesired fuel cell operation, a protective function before fuel cell operation for the electrolysis cells detected by the electrolysis module can be achieved jointly with a single protective unit. It is therefore no longer necessary to implement a cell-specific protective function for all electrolysis cells. This can reduce the effort required for the protective function. This can be particularly effective in electrolysis systems which have a large number of electrolysis modules, each of which likewise has a large number of electrolysis cells. The electrolysis module preferably has the properties of its electrolysis cells as a whole.This makes it possible to achieve a reliable protective function for the electrolysis cells of a respective electrolysis module with an appropriately adjusted protective unit. Preferably, the electrolysis cells are only in a state for carrying out the intended electrolysis operation after the electrolysis module has been manufactured.

[0017] The design of electrolysis modules according to the invention also makes it possible to reduce the effort required to control the intended electrolysis operation and / or the maintenance of the electrolysis system. The electrolysis modules according to the invention can be used to create individually manageable units, which can simplify the design of the electrolysis system. It is particularly advantageous if fluidic connections for the electrolysis cells can also be provided within the electrolysis module, so that the corresponding connection effort can be reduced. Preferably, only the electrolysis module needs to be connected fluidically. Furthermore, it is possible to test or monitor the function of an individual electrolysis module.Standardized parts can thus be created that simplify the construction and / or maintenance or monitoring of the electrolysis system. The manufacturing method can preferably comprise at least one examination of the electrolysis cells by means of the measuring device with respect to the at least one parameter, the classification of the electrolysis cells based on the at least one parameter in order to assign the electrolysis cells to the respective, in particular parameter-specific, cell class, and, for example, also combining, in particular connecting, a predetermined number of electrolysis cells of a single cell class to form the electrolysis module.

[0018] The cell classes can be determined based on the at least one electrical parameter. To record the at least one electrical parameter, an adapted measuring device is provided which can record the desired parameter of the electrolysis cells. For this purpose, the respective electrolysis cell can be detachably connected to the measuring device. If necessary, the measuring device can apply an electrical voltage and / or an electrical current to the respective electrolysis cell in order to record or determine the desired parameter. Depending on the recorded value of the at least one parameter, the respective electrolysis cell is assigned to a respective one of the cell classes. The assignment can be achieved, for example, by determining a respective value range for a respective parameter for the respective cell class.Furthermore, the electrolysis cell can be marked accordingly so that it can be recognized as belonging to the respective cell class on the basis of the marking. Of course, the division into cell classes is not restricted to the recording or determination of a single electrical parameter. A cell class can also be determined by more than one single parameter. In this respect, it is possible for two cell classes to have a first, identical value range for a first parameter, whereas these two cell classes can differ by a second value range for a second parameter. The cell classes preferably have different value ranges from one another. The at least one parameter can be a type of membrane of the cell, a catalyst used, a construction of a gas diffusion layer of the cell and / or the like.In particular, the at least one parameter can be at least one electrical parameter, for example an electrolysis voltage, an electrolysis current, which occurs during normal operation, an electrical capacitance and / or the like.

[0019] Only electrolysis cells belonging to a single cell class are used to manufacture the electrolysis module. This ensures a high degree of equivalence among the electrolysis cells of each electrolysis module, so that their protection against harmful fuel cell operation can be reliably achieved by a single protection unit for the electrolysis module.

[0020] With regard to the electrolysis system, it is not only necessary to use electrolysis modules whose electrolysis cells are assigned to a single cell class. Rather, it is possible to operate electrolysis modules with electrolysis cells of different cell classes in combination within the electrolysis system. The protective device can be adjusted to suit the electrolysis modules with different electrolysis cells, so that the desired protective function can be achieved even with such a combination. For this purpose, one protective unit of the protective device can be electrically connected to one of the electrolysis modules of the electrolysis system, so that a module-specific protective function can be achieved.The invention can therefore prove to be advantageous not only for the design and manufacture of the electrolysis plant, but it can also have an advantageous effect on the operation of the electrolysis plant, as will be shown below.

[0021] In an electrolysis module, the electrolysis cells are preferably mechanically connected to one another. For this purpose, the electrolysis module can have a frame or housing to which the electrolysis cells are connected. The frame or housing can also provide the module connections and, if necessary, fluid connections, so that only appropriate connections to the electrolysis module need to be provided in the electrolysis system to connect the electrolysis cells.

[0022] The protection unit is preferably an electronic circuit or hardware circuit which is supplied with electrical energy by the electrical energy source. The electrical energy source can, for example, have a direct voltage source or the like. The electrical energy source can be designed to supply energy to more than one single protection unit. However, the electrical energy source can also be individually designed to supply exactly one single protection unit. For this purpose, it can, for example, be at least partially integrated into the protection unit. The electrical energy source can, for example, use electrical energy from a public energy supply network or an electrical energy storage device.

[0023] It is further proposed that an electrical cell resistance between two electrode terminals of a respective electrolysis cell serves as a parameter. The measuring device can be electrically coupled to the electrode terminals to determine the cell resistance. Preferably, the measuring device can also provide a corresponding fluid connection which is detachably connected to the respective electrolysis cell. To determine the electrical cell resistance, it can be provided that the measuring device applies an electrical current or an electrical voltage to the respective electrolysis cell and that the respective other electrical variable is recorded and evaluated to determine the electrical cell resistance.

[0024] Furthermore, it is proposed that the electrolysis cell's electric current, which is established at its electrode terminals when the electrolysis cell is subjected to a protective voltage outside of its intended electrolysis operation to prevent fuel cell operation, serve as a parameter. This makes it possible to classify the electrolysis cells specifically according to the desired protective function.

[0025] Furthermore, it is proposed that for the at least one parameter an individual value range is specified for a respective cell class, which is different from the value ranges of other cell classes. This makes it possible to avoid multiple assignment of a respective electrolysis cell to more than one single cell class. The value ranges determining the cell classes do not have to be directly adjacent to one another. It can be provided that electrolysis cells whose electrical parameters do not fall into any of the value ranges are sorted out. This makes it possible to further improve the quality of the electrolysis system because, for example, electrolysis cells with very different properties are not used to manufacture the module.

[0026] According to a further development, it is proposed that, in order to produce the electrolysis module, a predetermined number of electrolysis cells of the respective cell class are arranged adjacent to one another and mechanically connected to one another to form the electrolysis module. The electrolysis cells can be connected, for example, by arranging the electrolysis cells adjacent to one another and connecting them to one another by means of mechanical connecting means. Such connecting means can be, for example, clamps, screws, rivets, but also connecting straps, latches, combinations thereof or the like. In addition, gluing, welding or the like can also be provided. By arranging or mechanically connecting the electrolysis cells, an electrical connection of the electrolysis cells can also be realized.The electrolysis cells can preferably be electrically connected in series, at least within the electrolysis module. In principle, however, a parallel connection or a matrix connection would also be conceivable. Particularly preferably, the arrangement or mechanical connection of the electrolysis cells can also create a fluidic coupling, via which the electrolysis cells can be supplied with the required fluids during normal electrolysis operation. For this purpose, the electrolysis cells can be connected, for example, to a module-side pipe network for supplying water and for removing hydrogen and oxygen.

[0027] The electrolysis module allows for the creation of a single, individually handled assembly that can be tested separately. The electrolysis module can have at least two electrolysis cells. However, the electrolysis module preferably has a plurality of electrolysis cells, for example, 10 electrolysis cells, 20 electrolysis cells, or more.

[0028] It is further proposed that the predetermined number of electrolysis cells of the respective cell class for producing the electrolysis module be installed in a module housing of the electrolysis module. The module housing can, for example, have a frame and / or housing walls by means of which the electrolysis cells of the electrolysis module can be at least partially separated from an external environment. In addition, the module housing can preferably provide the electrical and / or fluid-technical connections required for connecting the electrolysis cells. The module housing can furthermore have module connections by means of which the module housing can be connected to an electrical energy supply of the electrolysis system and / or a fluid supply of the electrolysis system.

[0029] It is further proposed that the electrolysis cells assigned to a respective cell class are marked according to the respective cell class when assigned to the respective cell class and / or are stored in a storage area individually assigned to the cell class. In this way, the electrolysis cells assigned to the respective cell class can be selectively made available for further processing to produce the electrolysis module. The marking can be achieved with an identification element, for example in the manner of a sticker affixed to the electrolysis cells, a color code on the electrolysis cells and / or the like. Alternatively or additionally, it can also be provided that the electrolysis cells are stored in a storage area individually assigned to the respective cell class.

[0030] Furthermore, it is proposed that, for the manufacture of the electrolysis module, only electrolysis cells labeled according to the respective cell class and / or only electrolysis cells from the storage area individually assigned to the respective cell class be used. In this way, a simple manufacture of the electrolysis modules with electrolysis cells of a respective cell class can be achieved.

[0031] According to a further embodiment, it is proposed that the electrolysis module is marked according to the assignment of its electrolysis cells to the respective cell class. The marking is preferably carried out by means of a marking. The marking can be arranged, for example, on the module housing. The marking can be implemented in the same way as for the electrolysis cells. The marking of the electrolysis module can, for example, be detected by the protection unit. Depending on the detected marking, the protection unit can set a module protection current which can be applied to the respective electrolysis module. This makes it possible to achieve automated, module-specific adaptation of the protection unit.

[0032] According to a further development, it is proposed that at least the electrode connections of the electrolysis cells be electrically connected to one another within the electrolysis module. This can reduce connection and / or assembly costs. At the same time, this further development makes it possible to provide at least a partially functional unit, so that testing of the electrolysis module is also possible in a simple manner. Particularly advantageously, fluid connections of the electrolysis cells are also formed at least partially within the electrolysis module.

[0033] It is also advantageous if the number of electrolysis cells in the electrolysis module is selected so that, in an operating state of the electrolysis module which differs from the intended electrolysis operation, fuel cell operation is avoided when module connections of the electrolysis module are supplied with a direct current as a module protection current for all electrolysis cells in the electrolysis module. The number of electrolysis cells can be selected depending on the value ranges of the cell classes and, if applicable, other boundary conditions, so that the protective function can be reliably achieved by the protective unit for all electrolysis cells of a respective electrolysis module. The number of electrolysis cells in a respective electrolysis module can, for example, be selected to be as large as possible in order to be able to keep the effort required for the protective function as low as possible.With regard to the protective unit, it is particularly proposed that the energy converter is designed to supply the electrolysis module with a clocked direct current as the module protective current. The protective unit is preferably supplied with an electrical voltage from the electrical energy source, so that it can consequently provide the respective protective current in the form of a clocked direct current. The protective unit is preferably provided individually for each electrolysis module and is electrically coupled to it. However, it can also be provided that the protective unit supplies the protective current to two or more electrolysis modules, in particular those connected in parallel.

[0034] The pulsed direct current can be selected as a protective current for the electrolysis of water, for example, in a range such that the cell voltage at a respective electrolysis cell is between approximately 1.35 V and approximately 1.45 V. The voltage is preferably greater than 1.25 V. An operating voltage during normal operation of the electrolysis is generally significantly greater than the protective voltage or the voltage achieved with the protective current. During normal electrolysis operation, the operating voltage at a respective electrolysis cell during the electrolysis of water can be approximately 1.9 V. With suitable electrolytes and / or catalysts, this voltage can under certain circumstances also be as low as approximately 1.8 V. However, these values ​​depend on the respective specific applications and the substances to be electrolyzed.During the electrolysis of carbon dioxide or another substance, these values ​​can of course vary considerably.

[0035] The electrical energy converter or energy transformer serves to establish or provide an energy coupling between the electrical energy source and the electrolysis cell connected to the protection unit. The electrical energy converter, occasionally also called energy transformer, can be designed to couple the electrical energy source to the electrolysis module in a galvanically isolated manner. The energy converter serves to convert electrical energy in a first form into electrical energy of at least a second form. The energy converter can be designed to convert energy only unidirectionally. In principle, however, it can also be designed to convert energy at least partially or temporarily bidirectionally.In this context, "galvanically isolated" or "potential-free" means, in particular, that no electrical connection to other electrical potentials is required. The energy converter can be designed, for example, as an inverter or a converter. On the electrolysis module side, it is preferably designed to provide the pulsed direct current with an adjustable amplitude and / or an adjustable duty cycle. A current control system can preferably be implemented.

[0036] The electrical energy converter can also be designed as a hardware circuit, as a DC-DC converter or the like. The electrical energy converter can have switching elements or electronic switching elements, in particular semiconductor switches, which serve the desired conversion function. A switching element in the sense of this disclosure is preferably a controllable electronic switching element, for example a transistor, a thyristor, combination circuits thereof, in particular with freewheeling diodes connected in parallel, for example a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), preferably with integrated freewheeling diodes, or the like. The switching element is operated in switching mode.

[0037] The switching operation of a semiconductor switch in the form of a transistor means that, in the switched-on state, a very low electrical resistance is provided between the terminals of the transistor forming the switching path, so that a high current flow is possible with a very low residual voltage. In the switched-off state, the switching path of the transistor has a high impedance, i.e., it provides a high electrical resistance, so that even with a high electrical voltage applied across the switching path, there is essentially no current flow, or only a very low, in particular negligible, current flow. This is different from linear operation in transistors.

[0038] This further development is based, among other things, on the finding that the electrolysis cells do not need to be supplied with a constant direct current when operating in a different way from their intended purpose. By taking into account the electrical capacity of each electrolysis cell, it is possible to achieve the desired function using a clocked direct current or a pulsed direct current. A clocked direct current means that an amplitude is not constant, but no change in polarity occurs with regard to the direct current. In particular, it can be provided that each of the electrolysis modules is supplied with a current-controlled clocked direct current. This makes it possible to determine whether the protective voltage is reached on the basis of a recorded electrical voltage as the module voltage at the respective electrolysis module.For this purpose, a corresponding sensor unit can be provided which is also electrically coupled to the module connections of the respective electrolysis modules. The further development is based, among other things, on the idea that the electrolysis cell and consequently also the electrolysis module can behave electrically like an electrical capacitor. By setting the clocked direct current, the desired protective function can thus be implemented in a simple manner. It proves to be advantageous that precise regulation of the protective voltage and a corresponding provision of a constant direct current are not required. This is particularly advantageous for the effort required to provide the direct current. In particular, complex smoothing units on the DC side can be reduced or even avoided.

[0039] The clocked direct current can have a predetermined or predeterminable frequency or clock rate. In the present case, predetermined or predeterminable frequency or clock rate preferably means that the frequency or clock rate is essentially constant at least for a predetermined plurality of clock periods in accordance with the specification. The frequency or clock rate can be predetermined, among other things, as a function of a minimum or average detected electrical module voltage, a predetermined minimum electrical module current, a predetermined average module current and / or the like. For example, the clocked direct current reaches the value zero in at least one clock pause. The clocked direct current can have a predetermined or predeterminable duty cycle. It can be provided that the duty cycle is set as a function of the cell voltage.Preferably, the clocked direct current has a substantially fixed frequency.

[0040] The module voltage is an electrical voltage between at least two module connections of the electrolysis module. The module voltage can be recorded continuously and / or at discrete times. The recorded module voltage can be averaged. The module voltage can, for example, also be recorded only during a clock pause or during a current pulse of the clocked direct current. Preferably, when the module voltage is recorded, it is also recorded at the same time whether the recording takes place during the clock pause or the current pulse. The electrolysis cells arranged in a respective electrolysis module are preferably PEM electrolysis cells. The PEM electrolysis cell is a cell that has a proton exchange membrane, often also called a proton exchange membrane (PEM) or polymer electrolyte membrane (PEM). The PEM is a semi-permeable membrane generally made of ionomer.PEMs are permeable to protons, while the transport of gases such as oxygen or hydrogen is essentially prevented. PEMs are manufactured, for example, either from pure polymer membranes or from composite membranes in which other materials are embedded in a polymer matrix. One commercially available PEM is Nafion from the chemical company DuPont. PEM electrolysis cells have the advantage, particularly over alkaline electrolysis cells, that bleeder resistances can be considerably lower. This not only enables high efficiency to be achieved compared to alkaline electrolysis cells, but also a large area-specific time constant to be achieved compared to alkaline electrolysis cells. PEM electrolysis cells can therefore achieve large time constants, particularly with regard to electrical parameters such as cell voltage and cell current.This may affect the setting of the switched DC current.

[0041] The advantages and effects stated for the method according to the invention naturally also apply equally to the electrolysis device according to the invention, the protective unit according to the invention, and the protective device according to the invention, and vice versa. In this respect, method features can also be formulated as device features, and vice versa.

[0042] For use cases or application situations that may arise during the method and which are not explicitly described here, it may be provided that, in accordance with the method, an error message and / or a request to enter user feedback is issued and / or a standard setting and / or a predetermined initial state is set.

[0043] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identity are included.

[0044] The exemplary embodiments explained below are preferred embodiments of the invention. The features and combinations of features specified above in the description, as well as the features and combinations of features mentioned in the following description of exemplary embodiments and / or shown alone in the figures, can be used not only in the respective combination specified, but also in other combinations. Thus, embodiments are also encompassed by the invention or are to be regarded as disclosed which are not explicitly shown and explained in the figures, but which arise from and can be produced by separate combinations of features from the explained embodiments.The features, functions, and / or effects illustrated by the exemplary embodiments may, in and of themselves, represent individual features, functions, and / or effects of the invention that can be viewed independently of one another, and which also further develop the invention independently of one another. Therefore, the exemplary embodiments are intended to encompass combinations other than those in the embodiments explained. Furthermore, the described embodiments may also be supplemented by further features, functions, and / or effects of the invention already described.

[0045] In the figures, the same reference symbols denote the same features and functions.

[0046] Shown are: FIG 1 in a schematic circuit diagram of an electrolysis plant with a plurality of electrolysis cells connected in series, which are connected to an electrolysis energy source and an auxiliary energy source connected in parallel thereto,

[0047] FIG 2 shows a schematic diagram of a polarization characteristic curve for an electrolysis cell of the electrolysis system according to FIG 1, in which a cell voltage of the electrolysis cell is shown as a function of an electrolysis current of the electrolysis cell,

[0048] FIG 3 shows a schematic circuit diagram of a section of an electrolysis plant with electrolysis modules,

[0049] FIG 4 is a schematic diagram in which a clocked current as a protective current for an electrolytic cell according to FIG 1 as well as a cell voltage and a control signal for the protective current are shown by means of respective graphs,

[0050] FIG 5 is a schematic block diagram of a protection unit according to FIG 3,

[0051] FIG 6 is a schematic flow diagram for a method for producing the electrolysis modules according to FIG 3, and

[0052] FIG 7 is a schematic representation of the manufacture of an electrolysis module.

[0053] FIG. 1 shows a schematic circuit diagram of an electrolysis system 52 with a plurality of electrolysis cells 12 connected electrically in series. The electrolysis cells 12 serve, in this case, for the electrolysis of water into hydrogen and oxygen in a reaction chamber (not shown in detail), which is formed between the respective electrodes of the respective electrolysis cell 12. In alternative embodiments, a different substance can, of course, also be subjected to electrolysis in order to convert it into corresponding other substances.

[0054] The series-connected electrolysis cells 12 are connected to a main rectifier 14 as the electrolysis energy source. The main rectifier 14 provides an operating voltage 50, which is applied to the series connection of the electrolysis cells 12, so that during intended operation, namely the electrolysis operation, an electrolysis current 48 flows through the electrolysis cells 12.

[0055] A series circuit comprising a polarization rectifier 54 and a protective inductance 58 as an auxiliary energy source is connected in parallel to the main rectifier 14 to the series circuit of the electrolysis cells 12. The polarization rectifier 54 and the protective inductance 58 serve to apply a rectifier voltage 68 to the electrolysis cells 12 outside of the intended electrolysis operation, said rectifier voltage being selected such that a protective current 56 is established, which in turn is selected such that all of the electrolysis cells 12 are supplied with at least a polarization voltage Uo (FIG. 2) as a protective voltage. This is intended to prevent undesired processes in the electrolysis cells 12 outside of the intended electrolysis operation.

[0056] FIG. 2 shows a schematic diagram 60 in which an ordinate 62 is assigned to a cell voltage at the respective cell terminals of an individual electrolysis cell 12. An abscissa 64 is assigned to the corresponding cell current of this electrolysis cell 12. A graph 66 shows the dependence of the cell voltage on the cell current. U N denotes an electrolysis voltage that occurs at the electrolysis cell 12 during normal electrolysis operation when the electrolysis cell 12 is subjected to the electrolysis current 48. The intersection point of the graph 66 with the ordinate 62 defines the polarization voltage Uo, below which a change in polarization of the cell current can result.

[0057] In the present design of the electrolysis cell for the electrolysis of water, the electrolysis voltage U Nabout 1.8 to 1.9 V. In alternative embodiments, however, it can also be about 2.0 V to about 2.5 V. The polarization voltage Uo can be about 1.48 V in the present embodiment. Depending on the design of the electrolysis cells 12, the polarization voltage Uo can also be in a range from about 1.1 V to about 1.45 V. At a cell voltage that is greater than about 1.48 V, the electrolysis functionality is generally present in the electrolysis cell 12 in that hydrogen and oxygen are generated. However, the electrolysis functionality usually begins as early as about 1.1 V, with the electrolysis functionality increasing with increasing voltage.

[0058] The electrolysis system 52 shown in FIG. 1 proves to be disadvantageous in that gas production can continue outside of the actual electrolysis process or the intended electrolysis operation. This can lead to undefined conditions in the electrolysis system 52, which, in the worst case, can even result in the formation of an ignitable gas mixture. To ensure safety in this case, additional comprehensive protective measures are required.

[0059] Furthermore, particularly when starting up the electrolysis system 52 or shutting down the electrolysis system 52, the situation may arise that, due to an uneven distribution of the protective voltage across the series-connected electrolysis cells 12, the polarization voltage Uo may fall below the limit in one or more of the electrolysis cells 12. This problem may occur, among other things, because the electrolysis cells 12 are not all identical and / or are at different ages. This may result in undesirable fuel cell operation, which may damage the respective electrolysis cells 12.

[0060] FIG. 3 shows a section of an electrolysis system 10 with electrolysis modules 20, in which the aforementioned problems can be reduced, if not completely avoided. The electrolysis system 10 is based on the electrolysis system 52 according to FIG. 1, for which reason reference is made to the relevant explanations. Here, too, a series circuit comprising a plurality of electrolysis cells 12 is provided, which are connected in parallel to the main rectifier 14 in order to be supplied with electrical energy during normal electrolysis operation. In this respect, the electrolysis system 10 corresponds to the electrolysis system 52, for which reason reference is made to the corresponding explanations for FIGS. 1 and 2.

[0061] In contrast to the embodiment according to FIG 1, in the electrolysis system 10 according to FIG 3, four electrolysis cells 12 are combined to form an electrolysis module 20. The electrolysis modules 20 formed in this way are connected in series to the main rectifier 14. The electrolysis modules 20 are essentially identical in design in the present case. Within a respective electrolysis module 20, the four electrolysis cells 12 are also connected in series. The electrolysis modules 20 each have two module connections 28 to which the series connection of the electrolysis cells 12 is connected.

[0062] The electrolysis system 10 further comprises a protective device 16, which has a protective unit 30 for each electrolysis module 20. Each protective unit 30 has two connection contacts 26, which are electrically connected to the respective module terminals 28. The protective units 30 serve to provide an individual protective current 74 (FIG. 4) for each of the series-connected electrolysis modules 20.

[0063] The protective device 16 is connected to the electrolysis modules 20, specifically to their module terminals 28. The protective device 16 has an auxiliary electrical voltage source 22 as an electrical energy source, which serves to provide an auxiliary DC voltage 24. In the present embodiment, it is therefore provided that all module terminals 28 are electrically coupled to the protective device 16.

[0064] Furthermore, the protection units 30 each have two connection terminals 34, by means of which they can be electrically coupled to the auxiliary voltage source 22. This makes it possible to individually apply a protective current 74 to each of the electrolysis modules 20 in order to reliably achieve a cell voltage greater than the polarization voltage Uo for all electrolysis cells 12 of a respective electrolysis module 20 outside of the intended electrolysis operation.

[0065] The auxiliary electrical voltage source 22 can, for example, be electrically coupled to a public power grid or the like. Each protection unit 30 provides the individual protection current 74 for the respective electrolysis modules 20, so that an individual protection voltage U s can be achieved.

[0066] The protective voltage U s(FIG 2) is selected such that no fuel cell effect occurs at any of the electrolysis cells 12 of the respective electrolysis module 20, i.e., gas residues in a respective electrolysis cell 12 react to form water according to the fuel cell principle and thus release energy. This can lead to significant aging of a respective electrolysis cell 12. The protective device 16 further comprises a switching unit (not shown) which is connected to the connecting terminals 34 of the protective units 30 and to the connecting contacts 26. The switching unit is not absolutely necessary for the invention and can - as required - also be omitted or modified. In the present embodiment, the switching unit is designed to electrically couple the protective units 30 to the connecting contacts 26 in order to provide the protective current 74 at the connecting terminals 34, depending on a switching state of the switching unit.This creates the possibility that the protection units 30 only need to be electrically connected to the electrolysis modules 20 when this is necessary or desired due to the operating situation of the electrolysis system 10. Thus, the protection units 30 can be deactivated relative to the electrolysis modules 20 by means of the switching unit when the electrolysis modules 20 are operated as intended in electrolysis mode. Furthermore, it can be provided, for example, that the voltage sensors 44 of the protection units 30 are connected directly to the connection contacts 26 for detecting the module voltages if it is desired that the module voltages can be detected independently of the switching state of the switching unit.

[0067] The operation of the protective device 16, in particular the protective units 30, is controlled by a control unit 18 of the electrolysis system 10. The control unit 18 may comprise a control circuit for this purpose.

[0068] To control the protective units 30, the present embodiment provides for a module current of the electrolysis module 20 to be detected by means of a current sensor. The current sensor delivers a corresponding sensor signal to the control unit 18, which evaluates this signal. As soon as the sensor signal is smaller than a predetermined comparison value, the switching unit is switched from the switched-off switching state to the switched-on switching state. This means that each electrolysis module 20 is supplied with the corresponding individual protective current 74 by the protective device 16, which is now activated as a result.

[0069] The protection units 30 are designed identically in the present case. However, this can also be different if required. One of the protection units 30 is explained by way of example using a schematic block diagram according to FIG 5. To provide the protection current 74, the protection unit 30 has an electronic voltage converter 42 which is coupled to the electrical auxiliary voltage source 22 and is designed here as a galvanically isolating DC / DC converter. At the same time, the voltage converter 42 is designed to output the predeterminable protection current 74 depending on a control signal. For this purpose, the voltage converter 42 is connected to the control unit 18 via an interface connection 70. The control unit 18 provides, among other things, the corresponding control signal so that the electrolysis module 20 coupled to the protection unit 30 can be supplied with the individual protection current 74.

[0070] In addition, the protection unit 30 has a voltage sensor 44 connected to the terminals 26, with which the module voltage of the electrolysis module 20 can be detected. A corresponding sensor signal is transmitted from the voltage sensor 44 via the interface connection 70 to the control unit 18. The control unit 18 evaluates, among other things, the sensor signal and, depending on this, determines a protective current 74 to be set. The control signal is transmitted to the voltage converter 42 depending on the determined protective current 74.

[0071] In the present case, it is provided that the protection units 30 of the protection device 16 are all designed identically and can be controlled by means of the control unit 32. FIG. 4 shows, in a schematic diagram representation for one of the electrolysis cells 12 according to FIG. 3, an example of a protection current 74 for the protection unit 30 coupled to the respective electrolysis cell 12. In the diagram 80 shown in FIG. 4, a left ordinate is assigned to the electrical voltage and a right ordinate to the electrical current. An abscissa is assigned to a time axis in ms. A graph 76 shows an internal converter control signal of the voltage converter 42, which controls the output of the protection current. In the present case, the converter control signal is a square wave signal, so that the voltage converter 42 can provide a clocked direct current. The clocked direct current, which represents the protection current, is shown by means of a graph 76.It can be seen that the protective current 74 is switched on or off synchronously with the converter control signal 76.

[0072] During this operation, the module voltage of the electrolysis module 20 is detected by means of the voltage sensor. In the present case, no separate lines need to be provided for this. It can be seen that the electrolysis module 20 displays a direct voltage 78 as module voltage which fluctuates by a slight amount due to the clocked direct current as protective current 74. The voltage fluctuation in this case is in a range from approximately 1.25 V to approximately 1.35 V. The voltage curve according to the graph 78 results from the capacitive effect of the electrolysis cells 12. This also explains why, according to the graph 76, the amplitude is not constant during a respective duration of a respective direct current pulse, but drops slightly. This is also a reaction due to the capacitive property of the electrolysis cells 12.

[0073] The control signal from control unit 18 can be used to adjust the amplitude of the pulsed direct current as well as the duty cycle of the pulsed direct current as required. For this purpose, control unit 18 can perform a corresponding evaluation of the sensor signal from the voltage sensor. In any case, the amplitude and duty cycle of the pulsed direct current are determined such that the detected electrical module voltage of electrolysis module 20 is sufficient for the cell voltages of electrolysis cells 12 of electrolysis module 20 to be greater than the corresponding protective voltage.

[0074] The frequency of the pulsed direct current can be selected within a range of approximately 10 Hz to approximately 100 Hz. It is preferably within a range of approximately 30 Hz.

[0075] FIG 6 shows a schematic flow diagram for a method for producing the electrolysis modules 20.

[0076] Method for producing an electrolysis module 20 for the electrolysis system 10 according to FIG 3 .

[0077] A plurality of electrolysis cells 12, which are designed to be supplied with the electrical electrolysis current 48 during normal operation in order to carry out electrolysis of water arranged in a reaction chamber of the electrolysis cells 12, are mechanically combined to form the electrolysis module 20. Before being combined to form the electrolysis module 20, the electrolysis cells 12 are classified in a step 90 with regard to at least one electrical cell resistance as an electrical parameter by detecting the cell resistance of a respective electrolysis cell 12 using a measuring device (not shown). In a step 92, the respective electrolysis cell 12 is assigned to one of a plurality of cell classes depending on a detected value of the cell resistance. To produce the electrolysis module 20, only electrolysis cells 12 that are assigned to a single cell class are selected in a step 94.In a step 96, four electrolysis cells 12 of a single cell class are selected and arranged in a module housing 88 of the electrolysis module 20 (FIG. 7). In a step 98, the electrode terminals of the electrolysis cells 12 are electrically connected in series with one another and with the module terminals 28 of the electrolysis module 20. The electrolysis module 20 is thus at least partially completed.

[0078] The embodiments serve solely to explain the invention and are not intended to limit it.

Claims

Patent claims 1. A method for producing an electrolysis module (20) for an electrolysis system (10) comprising a plurality of electrolysis modules (20), wherein a plurality of electrolysis cells (12), which are designed to be supplied with an electrical electrolysis current (48) during normal operation in order to carry out electrolysis of a substance arranged in a reaction chamber of the electrolysis cells (12), are mechanically combined to form the electrolysis module (20), wherein electrode terminals of the electrolysis cells (12) are electrically connected to one another and to module terminals (28) of the electrolysis module (20) in a predetermined electrical circuit, characterized in that the electrolysis cells (12) are classified with regard to at least one, preferably electrical, parameter before being combined to form the electrolysis module (20),by detecting the at least one parameter of a respective electrolysis cell (12) by means of a measuring device, the respective electrolysis cell (12) is assigned to one of several cell classes depending on a detected value of the at least one parameter, and only electrolysis cells (12) assigned to a single cell class are used to produce the electrolysis module (20).

2. Method according to claim 1, characterized in that an electrical cell resistance between two electrode terminals of a respective electrolysis cell (12) serves as a parameter.

3. Method according to one of the preceding claims, characterized in that the parameter used is an electric current of the electrolysis cell (12), which is established at its electrode terminals when the electrolysis cell (12) is operated outside of the intended electrolysis operation with a protective voltage to avoid fuel cell operation.

4. Method according to one of the preceding claims, characterized in that for the at least one parameter an individual value range is specified for a respective cell class, which is different from the value ranges of other cell classes.

5. Method according to one of the preceding claims, characterized in that for the production of the electrolysis module (20) a predetermined number of electrolysis cells (12) of the respective cell class are arranged adjacent to one another and are mechanically connected to one another to form the electrolysis module (20).

6. Method according to one of the preceding claims, characterized in that the predetermined number of electrolysis cells (12) of the respective cell class for producing the electrolysis module (20) are installed in a module housing (88) of the electrolysis module (20).

7. Method according to one of the preceding claims, characterized in that the electrolysis cells (12) assigned to a respective cell class are marked according to the respective cell class when assigned to the respective cell class and / or are stored in a storage area individually assigned to the cell class.

8. Method according to claim 7, characterized in that for the production of the electrolysis module (20) exclusively electrolysis cells (12) marked according to the respective cell class and / or exclusively electrolysis cells (12) from the storage area individually assigned to the respective cell class are used.

9. Method according to one of the preceding claims, characterized in that the electrolysis module (20) is marked according to the assignment of its electrolysis cells (12) to the respective cell class.

10. Method according to one of the preceding claims, characterized in that at least the electrode terminals of the electrolysis cells (12) within the electrolysis module (20) are electrically connected to one another.

11. Method according to one of the preceding claims, characterized in that the number of electrolysis cells (12) of the electrolysis module (20) is selected depending on the fact that in an operating state of the electrolysis module (20) different from the intended electrolysis operation when module connections (28) of the electrolysis module are applied (20) with a direct current as module protection current (74) for all electrolysis cells (12) of the electrolysis module (20) fuel cell operation is avoided.

12. Protection unit (30) for an electrolysis module (20) of an electrolysis system comprising several electrolysis modules (20) (10), wherein the electrolysis module (20) is manufactured according to one of the preceding claims, comprising: - at least two connection contacts (26) for electrical connection to respective module connections (28) of the electrolysis module (20), - at least two connection terminals (34) for electrical connection to an electrical energy source (22), and - a controllable electrical energy converter (42) which is electrically coupled to the at least two connecting terminals (34) and the connecting contacts (26) and which is designed to apply a direct current as a module protection current (74) to the electrolysis module (20) in an operating state different from the intended electrolysis operation.

13. Protection unit according to claim 12, characterized in that the energy converter (42) is designed to supply the electrolysis module (20) with a clocked direct current as the module protection current (74).

14. Protection device (16) for an electrolysis system (10) comprising a plurality of electrolysis modules (20) electrically connected in series, comprising: - a plurality of protection units (30), wherein each of the electrolysis modules (20) is electrically coupled to a respective protection unit (30), - at least one electrical energy source (22) for supplying the protection units (30) with electrical energy, and - a control unit (18) for individually controlling the protection units (30), characterized in that the protection units (30) are designed according to claim 8.

15. Electrolysis system (10) with a plurality of electrolysis modules (20) electrically connected in series and a protective device (16) electrically coupled to the electrolysis modules (20), characterized in that the electrolysis modules (20) are manufactured according to a method according to one of claims 1 to 6 and the protective device (16) is designed according to claim 9.

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