OPERATION OF AN ELECTROLYSIS DEVICE HAVING A PLURALITY OF ELECTROLYSIS CELLS

Description

BACKGROUND

The invention relates to a support device for an electrolysis device having a plurality of electrolysis cells, comprising connection contacts for electrically coupling to respective electrodes of the electrolysis cells. Furthermore, the invention relates to an electrolysis device comprising a plurality of electrolysis cells. Further yet, the invention relates to a method for operating an electrolysis device having a plurality of electrolysis cells, wherein, for electrically coupling to a support device for the electrolysis device, respective electrodes of the electrolysis cells are electrically coupled to connection contacts of the support device.

Electrolysis devices, support devices for the same, and methods for operating electrolysis devices are well known in the state of the art, so that there is basically no need for separate printed evidence for this. Generic electrolysis cells and electrolysis devices, in particular for the electrolysis of water to hydrogen and oxygen, are well known in the state of the art, for example from DE 197 29 429 C1. The general function of electrolysis, in particular water electrolysis, is known to the skilled person, which is why detailed explanations are not given here.

Electrolysis devices which have a single, but in particular a plurality of electrolysis cells, 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, such as hydrogen for a water electrolysis, carbon monoxide for a carbon dioxide electrolysis or the like. For this purpose, in normal operation, a suitable small electrical direct voltage is supplied to at least two electrodes of a particular electrolysis cell which can be in the range from a few volts or possibly even smaller than 1 V. A corresponding electrical direct current is provided as electrolysis current by an electrolysis energy source corresponding to the amount of substance to be provided by the electrolysis. In case of electrolysis cells connected in series, this direct current flows through all of the battery cells connected in series. The series connection is electrically coupled to an electrolysis energy source. In principle, however, it is also possible to connect electrolysis cells not only in series, but also at least partially in parallel.

In particular in aqueous electrolysis, such as chlorine/alkali electrolysis, PEM electrolysis or the like, a membrane is often provided which separates particular reaction chambers of particular reaction areas of a particular electrolysis cell in which particular electrodes are arranged. Often, a catalyst is arranged on such a membrane in order to enable or accelerate catalytically the process of electrolysis. Electrolysis is generally caused in that the electrodes of a particular electrolysis cell in normal operation are supplied with the electrolysis current or a suitable electrical direct voltage, also referred to as cell voltage.

What proves to be at least partially critical for a particular electrolysis cell is, among other things, a transition from or to an operating state that is different from the normal operating state. This relates, in particular, to a start up of the electrolysis cell or the electrolysis device and a shut down of the electrolysis cell or the electrolysis device. Particularly when shutting down after normal operation, residual substances, in particular dissolved or gaseous residual gases, can still be present in the electrolysis cell, which can, under certain circumstances, lead to the electrolysis cell being able to show fuel cell functionality. However, this can irreversibly damage the electrolysis cell, which is why the fuel cell functionality should be avoided at all costs. For this purpose, it is known to supply the electrolysis cell with a protective voltage, also called polarization voltage, outside of normal operation, which is chosen so that the fuel cell functionality can be largely avoided. For an electrolysis cell for electrolyzing water, the protective voltage can be about 1.25 V, for example. As soon as the electrolysis cell is correspondingly cooled down and residual gases are removed, providing the protective voltage can be deactivated.

Generic support devices are, among other things, for supporting or allowing for achieving secure operation of the electrolysis cells, in particular of the electrolysis device. For this purpose, the electrolysis cells are electrically connected to the support device, such that the electrolysis cells can be supplied independently from one another with a polarization current. Such a device is disclosed in EP 3 982 501 A1, for example.

Furthermore, it has been shown that electrolysis cells age differently from one another and/or can have characteristics deviating from one another. This can prove to be particularly problematic when electrolysis cells are connected in series if a protective voltage is to be provided as a polarization voltage by a voltage applied to the series connection. Due to the different ageing or characteristics, the case can occur where, particularly if the electrolysis cells are connected in series, the voltage applied to the series connection is not equally distributed to all cells connected in series. Therefore, it is then required to choose the electrical voltage of the series connection to be so large that the protective voltage can still reliably be achieved for the most unfavourable electrolysis cell. However, this also causes that the other cells are supplied with a correspondingly high voltage which can be significantly larger than the protective voltage so that these are further operated in electrolysis operation. Therefore, in order to avoid an explosive mixture in these electrolysis cells, it is common to purge with nitrogen.

It is further known from EP 3 982 501 A1 to individually supply each electrolysis cell with the protective voltage. However, providing the respective protective voltages for the electrolysis cells proves to be comparably complex. In addition, neither the state of health nor any characteristics of the electrolysis cells are taken into account, so that undesired states may continue to occur.

In addition, US 2018/0291516 A1 discloses an electrolysis system, an electrolysis control apparatus, and a method for controlling an electrolysis system. Furthermore, US 2022/0186390 A1 discloses an electrolysis device comprising bypassable bipolar plates.

SUMMARY

It is an object of the invention to allow for an improved operation of the electrolysis cells and the electrolysis device and provide a corresponding method.

With respect to a generic support device, the invention proposes that the support device has at least one voltage detection unit for detecting a cell voltage of each of the electrolysis cells, and an evaluation unit coupled in terms of signal technology to the at least one voltage detection unit for detecting at least one cell characteristic or at least a state of health for each of the electrolysis cells, wherein a number of controllable electronic current source circuits corresponding to the plurality of electrolysis cells is provided, wherein each of the current source circuits is electrically coupled to electrodes of each of the electrolysis cells and is designed to supply the respective electrolysis cell individually with a direct current that can be adjusted depending on a current source control signal.

With respect to a generic electrolysis device, the invention in particular proposes that the electrolysis device has a support device according to the invention.

With respect to a generic method, the invention in particular proposes that cell voltages of the electrolysis cells are detected using at least one voltage detection unit of the support device electrically coupled to the connection contacts, wherein the voltage detection unit provides a respective voltage signal depending on the respective detected electrical voltage, wherein the voltage signals are evaluated using an evaluation unit to determine at least one cell characteristic or at least a state of health for a respective electrolysis cell.

The invention is based, among other things, on the idea of detecting the cell voltages of the individual electrolysis cells, in particular, if the electrolysis cells are connected in series, and evaluating them using the evaluation unit. The evaluation unit may then determine at least one cell characteristic or at least a state of health based on this data. For this purpose, for example, it may be taken into account which respective cell current is or was supplied to each of the electrolysis cells. Of course, both the cell characteristic and the state of health of the respective electrolysis cell may be determined. This data may be used to improve individually the operation of the electrolysis cells, for example, by individually adjusting a cell current, in order to potentially operate the electrolysis cells individually in their optimal operating state. This may be particularly provided for the normal electrolysis operation, start of the electrolysis device and/or shut down of the electrolysis device. In addition, it may be achieved that, for a higher level electrolysis controller of the electrolysis device, for example, data is provided that allows for identifying the load capacity of the respective electrolysis cell. This load capacity, which may also comprise the state of health, may be used to allow for adjusting a power of the electrolysis cell within a preset range of operation. This may be used, for example, to vary, adjust an electrolysis line of the electrolysis device, or the like.

For example, if a low electrolysis power is to be activated, it is advantageous to potentially operate the electrolysis cells having a unfavourable state of health, whereas, if a high electrolysis power is desired, it is preferred to activate electrolysis cells having a low state of health, that is preferably substantially new electrolysis cells. Of course, it may also be provided that by operating normally the electrolysis cells and respectively activating or deactivating the electrolysis cells it may be achieved that the different states of health of the electrolysis cells may converge. Among other things, the knowledge of a cell voltage adjusting with a preset cell current depending on the state of health is used. With a preset cell current, the cell voltage typically increases with increased ageing. Therefore, the state of health of the electrolysis cell may determined, for example, from operating parameters of the electrolysis cell. Operating parameters may be, for example, the cell voltage, a cell current, a temperature of the electrolysis cell, measurements of fluid flows such as liquids and/or gases, or the like.

In addition, it may be taken into account that the cell voltage may depend on the activation of the catalysts and the like used in the respective electrolysis cells, among other things. Thus, assisted by the support device, an improved operation of the electrolysis cells and thus also of the electrolysis device in general may be achieved.

At the same time, the support device of the invention allows for starting or shutting down the electrolysis device to be realised generally more securely and reliably. This may be achieved by, among other things, detecting the respective cell voltages of the electrolysis cells during the normal operation and/or when starting or shutting down and taking them into account for adjusting a respective cell current. In exemplary embodiments, the respective cell current may also be taken into account. This is done preferably depending on the determined cell characteristic or the determined state of health. The cell characteristic may comprise, for example, a characteristic curve, other cell parameters, if needed, and/or the like of each of the electrolysis cells.

The support device has respective connection contacts for connecting to the electrolysis device, in particular for connecting to the electrolysis cells in form of electrically coupling, so that the desired electrical connection to the electrodes of the electrolysis cells may be established. The support device further has the voltage detection unit that is for detecting the cell voltages of the electrolysis cells. For this purpose, preferably, the voltage detection unit is electrically connected to the connection contacts of the support device. The voltage detection unit may detect the respective cell voltages individually or using time-division multiplexing, for example. The voltage detection unit provides corresponding voltage signals that are transmitted to the evaluation unit coupled in terms of signal technology. Thus, the corresponding voltage signals are available in the evaluation unit, so that the latter may determine at least the cell characteristic or at least the state of health of the respective electrolysis cell. The support device, in particular the voltage detection unit as well as the evaluation unit, if needed, may be designed as an electronic hardware circuit. They may also be formed at least partially by a program-controlled computing unit. Of course, combinations thereof may also be provided.

In exemplary embodiments, the electrolysis cells of the electrolysis device are connected at least partially in series. However, the invention is not limited to that. The support device may also be provided to be employed in an electrolysis device that has electrolysis cells connected at least partially in parallel. Of course, combinations of connections of electrolysis cells in series and in parallel may also be provided.

The voltage detection unit has a number of voltage sensors corresponding to the plurality of electrolysis cells, wherein each of the voltage sensors is electrically coupled to electrodes of each of the electrolysis cells and is designed to detect a cell voltage of the respective electrolysis cell and output a respective voltage signal depending on the detected cell voltage. Therefore, the voltage detection unit may simultaneously detect the cell voltages of the plurality of the electrolysis cells and output corresponding voltage signals. This may cause a very fast signal processing to be achieved. In general, this may improve the support device and potentially also improve the functionality.

In addition, it is proposed that the support device has at least one current sensor for detecting a cell current of at least one of the electrolysis cells and outputting a current signal depending on the detected cell voltage. If the electrolysis cells are connected in series, a single current sensor may typically be sufficient. However, it may also be provided that a respective individual current sensor for detecting the cell current is provided preferably for each of the electrolysis cells. Using the current sensors, the cell current may be detected preferably at least during the normal electrolysis operation or outside of the normal electrolysis operation, i.e., for example, also the polarization current upon shutting down the electrolysis device. In exemplary embodiments, the current sensor is also coupled in terms of signal technology to the evaluation unit, so that the current signals may be transmitted to the evaluation unit. Upon evaluation, the evaluation unit may then additionally take the at least one current signal into account.

It is also proposed that the support device has a number of controllable electronic current source circuits corresponding to the plurality of electrolysis cells, wherein each of the current source circuits is electrically coupled to electrodes of each of the electrolysis cells and is designed to supply the respective electrolysis cell individually with a direct current that can be adjusted depending on a current source control signal. This may achieve that each of the plurality of electrolysis cells may be supplied individually with a respective corresponding direct current. In exemplary embodiments, the electrolysis device or the electrolysis are operated outside of the normal electrolysis operation by supplying the electrolysis cells preferably with a protective current or polarization current to suppress or avoid, for example, the undesired fuel cell functionality. This is particularly the case when starting of the electrolysis device or shutting down the electrolysis device, in which otherwise electrolysis cells connected in series may particularly electrically supplied in an unequal manner. Using the individually provided current source circuits, each of the electrolysis cells may be supplied individually with the electric cell current. This cell current may be the protective current, for example, for avoiding the fuel cell functionality. In exemplary embodiments, the protective current depends on the determined cell characteristic and/or the determined state of health.

Each of the current source circuits can be adjusted using the current source control signal. The current source control signal may be provided for one or more current source circuits by the evaluation unit but also the higher level electrolysis controller of the electrolysis device, for example. This allows for the electrolysis cells to be potentially operated in a respective optimal operating state.

The evaluation unit is designed to detect the cell voltage and the cell current for a pre-settable period of time and, depending on the same, determine the cell characteristic and/or the state of health of the electrolysis cell. The cell current may be detected preferably at least during the normal electrolysis operation or at least outside of the normal electrolysis operation. However, it is particularly advantageous to detect the cell current substantially permanently. To this purpose, it may be provided that the evaluation unit has data of a new electrolysis cell as reference or starting values or retrieves it as a record from an external data storage via a communication connection. Using the respective current source circuit, it is also possible to detect and save an individual characteristic line for each of the electrolysis cells. In this way, for example, the cell characteristic may also be determined for an unknown electrolysis cell. This data may be used to determine a change in the respective cell characteristic, particularly in the operation-induced state of health, of the respective electrolysis cell. Among other things, the cell characteristic may also comprise operating states, changes in the operating states, operating parameters and/or changes in the operating parameters, which may be determined for the electrolysis cell. Of course, it may also be provided that data in respect to a state in respect to an end of life of the electrolysis cells is retrievably saved, wherein the evaluation unit may determine if each of the electrolysis cells has reached its end of life. If the end of life is reached, the evaluation unit may output a signal, for example, to have the respective electrolysis cell maintained or replaced. This may further improve the functionality of the electrolysis device in general. At the same time, the determined states of health of the electrolysis cells may be used to provide independently individual current source control signals, so that the electrolysis cells may be supplied with the cell current preferably depending on their respective determined state of health. This also allows for a further improvement of the operation of the electrolysis device in general.

In exemplary embodiments, the evaluation unit is designed to determine cell characteristics and/or states of health of all of the electrolysis cells connected to the support device and determine control data for an operating state in the electrolysis operation, start and/or shut down of the electrolysis device depending on the determined states of health. This control data may also include data with respect to the current source control signals, among other things, so that, particularly upon starting or shutting down the electrolysis device, a most optimal operation of the electrolysis cells may be achieved, particularly when connected in series.

It is further proposed that the support device has a separately handled housing having a connector to electrically connect the support device to the electrolysis cells. This allows for the support device to be easily connected to the electrolysis cells, particularly the electrolysis device and a reliable electrical contact to be established. The separately handled housing may be a closed housing, so that the support device is reliably protected from external influences. This is particularly advantageous if there are hazardous substances in the surroundings of the support device, for example an explosive gas mixture, an aggressive atmosphere, and/or the like. In exemplary embodiments, the connection contacts are also arranged on the housing such that electrical contact can be made.

According to another embodiment, it is proposed that the evaluation unit is designed to determine operating states of all of the electrolysis cells coupled to the evaluation unit and provide a state signal for a higher level electrolysis controller depending on the determined operating states to control the cell current depending on the state signal. The state signal may be used to adjust the individual current source control signals. However, it may also be used to control the cell current to be provided by the higher level electrolysis controller in the normal operation. This may particularly avoid overloading individual electrolysis cells, particularly significantly aged electrolysis cells. For example, this may achieve that the cell current may be controlled in a suitable manner preferably at least during the normal electrolysis operation or at least outside of the normal electrolysis operation during the protective operation. Furthermore, an operation of the electrolysis cells outside of an allowed normal operation, which may be defined by a cell construction and/or design parameters, may be avoided. In general, the reliability of the operation of the electrolysis device and the operational lifetime may be further improved or increased.

In exemplary embodiments, the support device has a communication interface providing a communication connection to the higher level electrolysis controller of the electrolysis device. The communication interface may be designed for wireless or also wired communications.

The support device may further be designed to detect other operating parameters of the electrolysis cells, preferably cell-to-cell. For this purpose, the support device may have suitable parameter sensors that may be integrally arranged at least partially in the support device or also in the respective electrolysis cells. Such parameter sensors may be, for example, for detecting a temperature in the electrolysis cells or the cell membranes or process fluids and gases thereof, a flow rate of process fluids in the respective electrolysis cell, particularly with respect to the electrolysis cells for electrolysis of water, a water vapour measurement, a gas composition, for example, to determine if a gas composition contains a flammable mixture, a pressure measurement, and/or the like. In exemplary embodiments, these parameter sensors may be coupled in terms of signal technology to the evaluation unit, so that the evaluation unit may perform the evaluation as a supplement depending on these signals. Again, this also allows for a further improvement of the operation of the electrolysis device.

In the method for operating a plurality of electrolysis cells according to the invention, each of the current source circuits of the is advantageously electrically coupled to electrodes of each of the electrolysis cells, wherein the respective electrolysis cell is supplied individually with a direct current that can be adjusted depending on a current source control signal.

Thus, both a protective operation and a normal operation of a plurality of electrolysis cells may be performed cell-to-cell using the support device. At the same time, for example, the determined states of health of the electrolysis cells may be used to provide independently individual current source control signals, so that the electrolysis cells are supplied cell-to-cell with the cell current preferably depending on their respective determined state of health. Depending on the operating mode, a protective current during a protective or an operating current during a normal operation is supplied for the normal electrolysis operation of a respective electrolysis cell.

Of course, the advantages and effects indicated for the support device according to the invention also equally apply for the electrolysis device according to the invention and the method according to the invention and vice versa. In this respect, the device features may also be formulated as method features and vice versa.

The exemplary embodiments explained in the following are preferred embodiments of the invention. The features, feature combinations indicated above in the description as well as the features and feature combinations mentioned in the following description of exemplary embodiments and/or shown alone in the figures can be used not only in the respective indicated combination, but also in other combinations. The invention therefore also comprises embodiments, or these are to be regarded as disclosed, which are not explicitly shown and explained in the figures, but which emerge and can be created from the explained embodiments through separate feature combinations. The features, functions and/or effects represented with the exemplary embodiments can, on their own, each represent individual features, functions and/or effects of the invention to be considered independently of one another which each can also further develop the invention independently of one another. Thus, the exemplary embodiments should also comprise other combinations than the ones in the explained embodiments. Furthermore, the described embodiments can also be complemented by further ones of the already described features, functions and/or effects of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures, the same reference numerals indicate the same features and functions.

In the drawings:

FIG. 1 shows a schematic diagram representation of an electrolysis device 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;

FIG. 2 shows a schematic diagram representation of a polarization characteristic curve for an electrolysis cell of the electrolysis device according to FIG. 1 where a cell voltage of the electrolysis cell is represented depending on an electrolysis current of the electrolysis cell;

FIG. 3 shows in a schematic diagram representation like FIG. 1 an electrolysis device where a respective protective unit is connected in parallel for every single electrolysis cell;

FIG. 4 shows a schematic diagram representation which represents a clocked current as the protective current for an electrolysis cell according to FIG. 1 and a cell voltage and a control signal for the protective current by means of particular graphs;

FIG. 5 shows a schematic diagram representation of an oscillogram of another protective current;

FIG. 6 shows a schematic diagram representation of an ageing of the electrolysis cell supplied with the protective current according to FIG. 5, determined based on polarization characteristic curves;

FIG. 7 shows a schematic block diagram representation of a protective unit according to FIG. 3;

FIG. 8 shows in a schematic block diagram a layout of the electrolysis device comprising the support device;

FIG. 9 shows a schematic perspective view of a first embodiment of an arrangement of the support device on an electrolysis device designed as a module; and

FIG. 10 shows in a schematic representation like FIG. 9 a second embodiment of an arrangement of the support device on an electrolysis device designed as a module.

DETAILED DESCRIPTION

FIG. 1 shows in a schematic diagram representation an electrolysis device 52 comprising a plurality of electrolysis cells 12 electrically connected in series. Here, the electrolysis cells 12 are for the electrolysis of water to hydrogen and oxygen in a reaction chamber, not further represented, which is formed between respective electrodes of the respective electrolysis cell 12. Of course, in alternative embodiments, another substance may also be subjected to electrolysis as an educt in order to convert it to corresponding other substances as products.

The electrolysis cells 12 connected in series are connected to a main rectifier 14 as the electrolysis energy source. The main rectifier 14 provides an operating voltage 50 with which the series connection of the electrolysis cells 12 is supplied so that in normal operation, i.e. electrolysis operation, an electrolysis current 48 flows through the electrolysis cells 12.

In parallel to the main rectifier 14, a series connection of a polarization rectifier 54 and a protective inductance 58 as an auxiliary energy source is connected to the series connection of the electrolysis cells 12. The polarization rectifier 54 and the protective inductance 58 are for supplying the electrolysis cells 12 outside the normal electrolysis operation with a rectifier voltage 68 which is chosen so that a protective current 56 is set, which, in turn, is chosen to be that high so that all of the electrolysis cells 12 are supplied at least with a sufficiently high polarization voltage U₀ (FIG. 2) that is set to be greater than or equal to a required protective voltage U_s. This is to avoid unwanted processes in the electrolysis cells 12 outside of the normal electrolysis operation.

FIG. 2 shows in a schematic diagram representation a diagram 60 where an ordinate 62 of a cell voltage at respective cell terminals 28 is associated with a single one of the electrolysis cells 12. An abscissa 64 is associated with the corresponding cell current of this electrolysis cell 12. A graph 66 shows as a polarization characteristic curve the dependency of the cell voltage from the cell current. U_N indicates an electrolysis voltage which adjusts to the electrolysis cell 12 in normal electrolysis operation when the electrolysis cell 12 is supplied with the electrolysis current 48 of an electrolysis current I_n. An intersection of the graph 66 with the ordinate 62 defines the polarization voltage U₀. the shortfall of which may result in a polarization change of the cell current.

In the present embodiment of the electrolysis cell 12 for the electrolysis of water, the electrolysis voltage U_N is about 1.8 to 1.9 V. The polarization voltage U₀ may be about 1.48 V in the present embodiment. Depending on a construction of the electrolysis cells 12, the polarization voltage U₀ may also be in a range from about 1.25 V to about 1.45 V. In the case of a cell voltage larger than about 1.48 V, the electrolysis cell 12 starts the electrolysis functionality by creating both hydrogen and oxygen.

Thus, the electrolysis device 52 according to FIG. 1 proves to be disadvantageous in that gas may still be produced outside of the actual electrolysis process or the normal electrolysis operation. This may result in undefined conditions in the electrolysis device 52 which, in the most disadvantageous case, may even result in generating an inflammable gas mixture. In order to guarantee safety here, additional extensive protective measures are required.

Furthermore, particularly when starting the electrolysis device 52 or when shutting down the electrolysis device 52, it may be that one or more of the electrolysis cells 12 fall below the polarization voltage U₀ due to an uneven distribution of the protective voltage U_s across the electrolysis cells 12 connected in series. This problem may occur, among other things, because the electrolysis cells 12 are not entirely identical and/or have a different state of health, that is a cell characteristic different from one another and/or a state of health different from one another. This may result in an undesired fuel cell operation which may damage the respective electrolysis cells 12.

FIG. 3 now shows an electrolysis device 10 where the problems mentioned above may be reduced or even avoided completely. The electrolysis device 10 is based on the electrolysis device 52 according to FIG. 1; thus, additional reference is made to the respective explanations. Here as well, a series connection of a plurality of electrolysis cells 12 is provided, which is connected to the main rectifier 14 in parallel in order to be supplied with electrical energy in normal electrolysis operation. Insofar, the electrolysis device 10 corresponds to the electrolysis device 52, thus, reference is made to the respective explanations for FIGS. 1 and 2.

In contrast to the embodiment according to FIG. 1, it is provided for the electrolysis device 10 according to FIG. 3 to have a support device 90 comprising a protective apparatus 16 and a control unit 18, which are for providing an individual protective current 76 (FIG. 4) for each of the electrolysis cells 12 connected in series. The protective apparatus 16 is connected to the electrolysis cells 12, namely to their cell terminals 28. The protective apparatus 16 has an electrical auxiliary voltage source 22 as an electrical energy source which is for providing an electrical auxiliary direct current voltage 24. The protective apparatus 16 further has contact terminals 26 for electrically connecting to the cell terminals 28 of the electrolysis cells 12 of the series connection. Thus, in the present embodiment, it is provided for all of the cell terminals 28 to be electrically coupled to the protective apparatus 16.

The protective apparatus 16 further has respective protective units 40 comprising connection contacts 72 which are each electrically coupled to each of the electrolysis cells 12, i.e. their electrodes, via the contact terminals 26 and the cell terminals 28. Furthermore, the protective units 40 each have two connection terminals 34 by means of which they may be electrically coupled to the auxiliary voltage source 22. This allows for each of the electrolysis cells 12 to be supplied individually with a protective current 76 in order to be able to also reliably achieve a larger cell voltage than the polarization voltage U₀ independently of normal operation.

For example, the electrical auxiliary voltage source 22 may be electrically coupled to a public energy supply network or the like. Each protective unit 40 provides an individual protective current 76 for each of the electrolysis cells 12 so that an individual protective voltage U_s may be achieved.

The protective voltage U_s (FIG. 2) is chosen so that no fuel cell effect is developed on any of the electrolysis cells 12, i.e., it is avoided that gas residues react to form water in a respective electrolysis cell 12 according to the fuel cell principle and thus release energy. This may result in a significant ageing and damage of a respective electrolysis cell 12.

In the present case, further provided is a switching unit 36 connected to the connection contacts 72 of the protective units 40 of the support device 90 and to the contact terminals 26 of the electrolysis device 10 or the electrolysis cells 12. The switching unit 36 is not necessarily required for the invention and may—as required—also be omitted or be designed in a modified manner. In the present embodiment, the switching unit 36 is designed to electrically couple the protective units 40 to the contact terminals 26 for providing the protective current 76 to the terminal contacts 72 depending on a switching state of the switching unit 36. Thus, the possibility is created that the protective units 40 only need to be electrically connected to the electrolysis cells 12 if this is required or desired due to the operating situation of the electrolysis device 10. Thus, the protective units 40 may be deactivated by means of the switching unit 36 relative to the electrolysis cells 12 if the electrolysis cells 12 are operated in the normal electrolysis operation. Furthermore, for example, the voltage sensors 44 (see FIG. 7) of the protective units 40 are provided to be directly connected to the contact terminals 26 for detecting the cell voltages if it is desired that the cell voltages should be able to be detected independently of the switching state of the switching unit 36.

The switching unit 36 has a respective individual switching element 38 for each of the contact terminals 26, which is formed by a reed relay or reed contact in the present case. Of course, in alternative embodiments, a corresponding relay or a contactor or also an electronic switching element may also be provided in the present case.

The switching elements 38 are commonly controlled by the control unit 18 of the support device 90 with regard to their respective switching state so that all of the switching elements 38 substantially assume the same switching state. For this purpose, the control unit 18 may comprise a control circuit which, among other things, is also for controlling the protective apparatus 16. The control unit 18 in the present case—as will be explained below in detail—provides an evaluation functionality so that it also functions as an evaluation unit.

In order to control the switching unit 36, it is provided in the present embodiment that a cell current of the series connection of the electrolysis cells 12 is detected as a sensor unit by means of a current sensor not shown in detail. The current sensor provides a corresponding sensor signal to the control unit 18 which evaluates this signal. As soon as the sensor signal is smaller than a specified comparison value, the switching unit 36 is switched from the switched-off switching state to the switched-on switching state. This means that through the protective apparatus 16, which is hereby now activated, every electrolysis cell 12 is supplied with the corresponding individual protective current 76.

Here, the protective units 40 are designed identically. However, if required, this may also be different. One of the protective units 40 is explained as an example with a schematic block diagram representation according to FIG. 7. In order to provide the protective current 76, the protective unit 40 has an electronic converter 42 coupled to the electrical auxiliary voltage source 22 which, in the present case, is designed as a current-controllable galvanically separating DC/DC converter of a current source circuit type. At the same time, the converter 42 is designed to deliver the pre-settable protective current 76 depending on a current source control signal. The current source circuit is characterized in general specifically, among other things, in that the current source circuit outputs an electric current for an operating range preset by measurement, for example a voltage range or the like, the value of which substantially depends on the current source control signal only. For this purpose, the converter 42 is connected to the control unit 18 of the support device 90 via an interface terminal 70. Among other things, the control unit 18 provides the corresponding current source control signal so that the electrolysis cell 12 coupled to the protective unit 40 may be supplied with the individual protective current 76.

Furthermore, the protective unit 40 has a voltage sensor 44 connected to the connection contacts 72 that may detect the cell voltage of the electrolysis cell 12. A corresponding voltage signal is transmitted from the voltage sensor 44 to the control unit 18 via the interface terminal 70. The control unit 18 evaluates the voltage signal, among other things and, depending on the same, determines the protective current 76 to be adjusted for the respective electrolysis cell 12. Depending on the respective determined protective current 76, the current source control signal is transmitted to the converter 42. Even if the protective current 76 may be a constant direct current, the protective current 76 provided does not need—as will be apparent below—to be a constant direct current.

In the present case, all of the protective units 40 of the protective apparatus 16 are provided to be designed identically and may be controlled by means of the control unit 18.

FIG. 4 exemplarily shows, in a schematic diagram representation for one of the electrolysis cells 12 according to FIG. 3, a protective current 76 for the protective unit 40 coupled to the respective electrolysis cell 12. In the diagram 80 shown in FIG. 4, a left ordinate is associated with the electrical voltage in V and a right ordinate is associated with the electrical current in A. An abscissa is associated with a time axis in ms. Graph 80 illustrates a converter-internal converter control signal 74 of the converter 42 which controls the output of the protective current 76. In the present case, the converter control signal 74 is a rectangular signal so that the converter 42 is able to provide a clocked direct current. The clocked direct current, which represents the protective current 76, is represented also shown in diagram 80. It can be seen that the protective current 76 is switched on or off synchronously to the converter control signal 74 according to the diagram 80.

During this operation, the cell voltage of the electrolysis cell 12 is detected by means of the voltage sensor 44 (see FIG. 7). For this, no separate lines need to be provided, as already explained with FIG. 7. It can be seen that the electrolysis cell 12 shows a direct current voltage 78 varying by a small amount as a cell voltage due to the clocked direct current as the protective current 76. In the present case, the voltage variation is in a range from about 1.25 V to about 1.35 V. The voltage curve 78, shown in diagram 80, results from the capacitive effect of the electrolysis cell 12. This also explains why, according to the diagram 80 during a respective duration of a respective direct current impulse, the amplitude is not constant, but drops slightly. This is also a reaction due to the capacitive characteristic of the electrolysis cell 12.

An amplitude of the clocked direct current and a duty cycle of the clocked direct current may be adjusted with the control signal of the control unit 18 as required. For this purpose, the control unit 18 may perform a corresponding evaluation of the sensor signal of the voltage sensor 44 (cf. FIG. 7 and FIG. 8). In any case, the amplitude and the duty cycle of the clocked direct current are determined so that the detected electric cell voltage of the electrolysis cell 12 is larger than the corresponding associated protective voltage U_s. In addition, by taking into account the cell voltage and the cell current of the electrolysis cell 12 caused by the clocked direct current as the protective current 76, a state of health of the electrolysis cell 12 may be determined depending on an evaluation by the control unit 18. The duty cycle and/or the amplitude of the clocked direct current may then be adjusted additionally depending on the determined state of health of the electrolysis cell 12.

In an alternative embodiment, a regulation may be provided to be realized using the sensor signal of the voltage sensor 44. For this purpose, for adjusting the duty cycle of the clocked direct current, the cell voltage may be provided to be compared to an individual protective voltage U_s of the electrolysis cell 12 and a respective current impulse of the clocked direct current is triggered depending on this comparison. The cell voltage may then be compared with a preset voltage comparison value which is larger than the individual protective voltage U_s, and the current impulse of the clocked direct current may be terminated depending on this comparison. Thus, by choosing the preset voltage comparison value, a duty cycle and/or also a frequency of the clocked direct current can be adjusted.

In addition, in an alternative embodiment, a constant direct current may be provided to be laid additionally over the clocked direct current. Thus, it can be achieved, for example, that the protective current 76 does not reach the value zero. This may improve reliability and safety.

FIG. 5 shows an oscillogram 88 of another protective current 76 in another schematic diagram representation. Again, the protective current. An abscissa is associated with time in ms, whereas an ordinate is associated with a current in A. It can be seen that the clocked direct current in this embodiment has current impulses in a range between 0.5 and 1.5 A. In the present case, the current impulses are spaced apart over a respective period of time which is about 145 ms.

FIG. 6 shows in another schematic diagram representation a diagram 86 from which it can be seen how the clocked protective current 76 affects an ageing of the electrolysis cell 12. An abscissa is associated with the electrical current in A, whereas an ordinate is associated with the electrical voltage in V. A graph 84 represents a polarization curve of an electrolysis cell 12 at the beginning of the supply of a protective current 76 according to FIG. 5. A graph 82 represents a further polarization curve at the end of an inspection period. The inspection was performed on an electrolysis cell 12 having an electrode surface of about 10 cm² with a current feed over a period of time of 166 hours as the inspection period of time with a maximum protective current 76 of about 1.3 A. From the graphs 84 and 82 it may be seen that there were no significant differences with respect to the polarization curve. It may be inferred therefrom that no measurable ageing of the electrolysis cell 12 has occurred.

The frequency of the clocked direct current may be chosen in a range from about 10 Hz to about 100 Hz. In exemplary embodiments, it is in a range of about 30 Hz.

FIG. 8 shows in a schematic block diagram a layout of the electrolysis device 10 comprising the support device 90. From FIG. 8, it may be seen that the electrolysis cells 12 in the present case are grouped as a module to realise a module-like or modular construction of the electrolysis device 10. Connected to the module are fluid terminals 98 not shown in detail via which educt water to be electrolytically split may be supplied, as well as hydrogen and oxygen, generated during normal electrolysis, may be dissipated as products. Each of the electrolysis cells 12 is electrically connected to a respective current source circuit 42 in order to be supplied individually with a cell current. Furthermore, each of the electrolysis cells 12 are electrically connected with a respective voltage sensor 44. Both the voltage sensors 44 and the current source circuits 42 in the present case are connected to the control unit 18 in terms of signal technology. The evaluation unit functioning as the control unit 18 is designed to determine states of health of all of the electrolysis cells 12 coupled to the support device 90 and to determine, depending on the determined states of health, control data for starting or shutting down the electrolysis device 10. This data is transmitted from the control unit 18 to the higher level electrolysis controller 32 via a communication connection not shown in detail. The electrolysis controller 32 is for higher level control of the electrolysis device 10. The electrolysis controller 32 may be connected to more than one single electrolysis device 10 and may control, for example, all of the electrolysis devices 10 together being in communication with it. In addition, the control unit 18 is provided to be communicatively coupled to further control units 18 of further support devices 90 serving for operating further electrolysis devices 10.

FIG. 9 shows a schematic perspective view of a first embodiment of an arrangement of the support device 90 on an electrolysis device 10 designed as a module comprising a module housing 96. It may be seen that the support device 90 has a separate handled housing 94 that has a substantially approximate planar cuboid structure. The support device 90 further has a connector 92 for electrically connecting the support device 90 to the electrolysis cells 12 that is connected to the housing 94 via an electric connecting line 100 in the present case. In this way, the support device 90 may easily be connected to the electrolysis device 10. The connector 92 is connected to the module at a front and is attached in this way to the module housing 96.

FIG. 10 shows in a schematic representation like FIG. 9 a second embodiment of an arrangement of the support device 90 on an electrolysis device 10 designed as a module comprising a module housing 96. This embodiment is based on the embodiment according to FIG. 9; thus, additional reference is made to the explanations of FIG. 9. This embodiment differs from the first embodiment in that the connector 92 is integrally formed with the housing 94. This allows for the connecting line 100 to be omitted. The connector 92 is formed at one end of the housing 94 and projects from a plane defined by the housing 94. This allows for the connector 92 to be connected to the module substantially as in the first embodiment according to FIG. 9, in particular, it may be plugged into the module housing 96.

Although the principle of the invention has been explained above using the application of individual electrolysis cells of the electrolysis device, the principle of the invention, however, is similarly also applicable to the electrolysis device having one or more cell blocks, wherein a respective cell block may comprise two or more electrolysis cells. Therefore, the cell specific aspects may substantially be adapted and also applied to a respective cell block, as will be readily appreciated by those skilled in the art. Therefore, this easy and simple adaption may also achieve the treatment of cell blocks. Of course, combinations of cell blocks and individual electrolysis cells may be provided.

The exemplary embodiments exclusively serve to explain the invention and are not intended to limit it.