Electrolysis device and method for controlling the electrolysis device

Abstract

The present invention relates to a method for controlling an electrolysis device. To control the electrolysis device a change in the input power is detected. Further, the detected change in the input power is directed to an electrolysis cell of a first type of the electrolysis device and / or an electrolysis cell of a second type of the electrolysis device on the basis of a first dynamic performance parameter of the electrolysis cell of the first type and / or a second dynamic performance parameter of the electrolysis cell of the second type.

Description

BACKGROUND

[0001] The present invention relates to an electrolysis device, a system comprising the electrolysis device and a method for controlling the electrolysis device.

[0002] Electrolysis is a widely known electro-chemical method, wherein a direct (electrical) current (DC) is used to drive an otherwise non-spontaneous chemical reaction. It has gotten recent attention as a factor in fighting against climate change, as it may be utilized in so-called “power to X” processes. In said processes, a supply medium (such as water or CO2) is generally converted by means of renewable electrical energy into chemical energy via electrolysis. The electrolysis products containing this energy ranging from e.g. hydrogen H2 (with O2 as by-product) over small hydrocarbons like methane CH4 (also termed “synthetic natural gas” SNG or synthetic LNG in its liquid form), ethylene C2H4 or ethanol C2H5OH to ammonia NH3 or carbon monoxide CO. Said molecules may be used as fuel, e.g. for vehicles or generators, or as feedstock for the chemical industry.

[0003] In general, said electrolysis process needs to be supplied with a predictable power input. Whereas the generation of renewable energy is known to provide a fluctuating power due to various reasons. For example, the amount of generated energy is dependent on weather conditions or on the position of the sun. Further, the amount of generated energy depends on the current season as well as on the course of the day. To protect electrolysis cells from damage caused by fluctuations in the input power, they must be operated in such a way that no energy shortage occurs during operation. To this end, generated power cannot be consumed entirely, but has to be wasted in parts.SUMMARY

[0004] It is an object of the present invention to improve an efficiency of the electrolysis process.

[0005] This object is solved by a method according to the independent method claim.

[0006] Furthermore, this object is solved by an electrolysis device according to the corresponding device claim and a system according to the corresponding system claim.

[0007] Embodiments of the invention are subject of correspondingly dependent claims and the following description.

[0008] According to the method of the invention an electrolysis device is controlled by detecting a change in the input power. Further, the detected change in the input power is directed to an electrolysis cell of a first type of the electrolysis device on the basis of a first dynamic performance parameter of the electrolysis cell of the first type and / or a second dynamic performance parameter of an electrolysis cell of a second type of the electrolysis device. Additionally or alternatively, the detected change in the input power is directed to the electrolysis cell of the second type on the basis of the first dynamic performance parameter of the electrolysis cell of the first type and / or a second dynamic performance parameter of the electrolysis cell of the second type.

[0009] In this context, the dynamic power parameter is a slope of a load profile of a corresponding electrolysis cell, wherein the load profile characterizes a possible change in the load of the electrolysis cell between a first operating state at 10% of a power rating of the electrolysis cell and a second operating state at 100% of the power rating of the electrolysis cell with respect to a time interval. Thus, the electrolysis cell of the first type and the electrolysis cell of the second type differ at least in the corresponding performance parameters. Further, the input power is to be understood as an electrical input power.

[0010] This allows to selectively distribute fluctuations in the input power over the electrolysis cells. In this way, said fluctuations can be buffered in dependence of corresponding dynamic performance parameters. Thus, a corresponding electrolysis device becomes capable to consume generated renewable energy almost entirely despite occurring fluctuations.

[0011] In an embodiment of the method, the input power is partitioned on the basis of a parameter of the electrolysis cell of the first type and / or a parameter of the electrolysis cell of the second type. Depending on the correspondingly partitioned input power, the electrolysis cells are supplied with said predetermined part of the input power in order to be operated. For example, said parameter can be a capacity, a current load, a prospective load, a temperature of the electrolysis cell, a temperature of an environment and / or a dynamic performance parameter of a corresponding electrolysis cell. In this way, the input power can be distributed to the electrolysis cells of different types in such a way that a reliable and safe operation can be realized. Accordingly, buffering of fluctuating parts of the input power can be optimized.

[0012] In a further embodiment of the method, the input power is repartitioned after a change of said input power on the basis of a parameter of the electrolysis cell of a first type and / or a parameter of the electrolysis cell of a second type in order to supply said electrolysis cells with a predetermined part of the input power. Said parameters can be of the same type as those already described before. So, the distribution of the input power over the different types of electrolysis cells can be reliably adapted to a current state of input power. Hence, a reliable and safe operation can be maintained.

[0013] In another embodiment of the method, it is proposed that a part of the input power directed to the electrolysis cell of the first type is adjusted from a currently provided part to a predetermined part based on the corresponding first dynamic power parameter. In particular, said adjustment from a currently provided part to a predetermined part is based on the corresponding first dynamic power parameter and on the second dynamic power parameter of a corresponding electrolysis cell of the second type. In this way, it becomes possible to distribute the change in the input power in an efficient way.

[0014] Furthermore, it is provided that a part of the input power directed to the electrolysis cell of the second type is adjusted from a currently provided part to a predetermined part based on the first dynamic power parameter. In particular, said adjustment from a currently provided part to a predetermined part is based on said first dynamic power parameter and on the second dynamic power parameter of a corresponding electrolysis cell of the second type. This enables reliable distribution of parts of the input power over electrolysis cells having different dynamic power parameters in order to avoid losses.

[0015] In another embodiment, the second dynamic performance parameter is higher than the first dynamic performance parameter. In this way, long-term fluctuations and short-term fluctuations of the input power can be selectively distributed over electrolysis cells having different dynamic power parameters. Exemplarily, said long-term fluctuations, which for example are caused by a changing position of the sun during the course of a day, can be directed to an electrolysis cell having a lower dynamic performance parameter. In contrast, short-term fluctuations, for example due to a fast change of weather conditions, can be directed and consumed instantaneously to an electrolysis cell having the higher dynamic performance parameter. As a result, the waste of generated energy can be avoided.

[0016] In a further embodiment, it is proposed that the second dynamic performance parameter is at least 20 times higher, preferable at least 40 times and especially preferred at least 60 times higher than the first dynamic performance parameter. This allows for an instantaneous consumption of detected changes in the input power by the electrolysis cells of the second type. Additional devices to buffer these changes, such as capacitors or batteries, can be avoided.

[0017] Another embodiment is provided, in which the first dynamic power parameter is in a range of values between 7%, inclusive, of a power rating of electrolysis cell of the first type per minute and 13%, inclusive, of a power rating of the electrolysis cell of the first type per minute. In this context, the power rating is the highest peak electrical power input allowed to be supplied for continuous operation of the corresponding equipment. Said load profile corresponds to classical electrolysis cells, e.g. such using alkaline electrolysis. Such electrolysis cells, having said load profile, are commonly used as they are cheap and providing good capacities.

[0018] Further, it is proposed that the second dynamic performance parameter is in a range of values between 7%, inclusive, of a power rating of the second type electrolysis cell per second and 13%, inclusive, of a power rating of the second type electrolysis cell per second. For example, said load profile can be realized by means of an electrolysis cell having a proton exchange membrane or an anion exchange membrane. In particular, the electrolysis electrodes of said electrolysis cells are directly deposited at the conducting membrane. In contrast to classical electrolysis cells, e.g. such using alkaline electrolysis, the proton or anion exchange membrane enables a fast adaption of a production rate to a change in the input power.

[0019] Another aspect of the invention relates to an electrolysis device for carrying out the process according to the invention.

[0020] Said electrolysis device comprises an electrolysis cell of a first type and an electrolysis cell of a second type. In one embodiment, the electrolysis device comprises a plurality of electrolysis cells of the first type as well as of the second type. In particular, said electrolysis cells are each configured to generate an electrolysis product from a supply medium by means of supplied electrical energy. In one embodiment, said electrolysis cells convert the supply medium water into H2 and O2; or the supply media CO2 and water into CO, small hydrocarbons or small oxygenates.

[0021] Further, said electrolysis device comprises a control device configured for carrying out the method according to the invention. Said control device can be an analog or digital circuit. In one embodiment, the control device comprises a sensor unit configured for detecting a change in the input power. Said sensor unit can further be configured to detect a current load of the electrolysis cells. Also, the control device can comprise a data processing unit. In one embodiment, said data processing unit is configured for carrying out the method according to the invention. In particular, said data processing unit is configured for distributing the input power to different electrolysis cells. Said data processing unit may be a computer, a microcontroller, a processor, or a programmable hardware component. Furthermore, it is conceivable that the data processing unit is a virtualized hardware resource of a computer cloud or a runtime environment with variable computing and / or storage capacities. Such a runtime environment is to be understood in the present context in the sense of computer science. Moreover, the data processing unit is preferably configured to read, write, transfer and / or process data.

[0022] By said electrolysis device, a high overall efficiency can be provided. In this way, also low levelized costs of the electrolysis product can be provided.

[0023] In an embodiment of the electrolysis device, the electrolysis cell of the first type is an alkaline electrolysis cell. In this way, a reliable and efficient electrolysis device can be provided. Further, this allows for using commonly available electrolysis cells having low production costs.

[0024] In a further embodiment of the electrolysis device, the electrolysis cell of the second type is a proton exchange membrane or an anion exchange membrane electrolysis cell. This enables to provide a flexible and fast adaptable electrolysis device, in particular in view of a fluctuating electrical power input generated from renewable energy sources. In this way, electrolysis cells are combined having a weak dynamic power parameter and a high dynamic power parameter. This enables the electrolysis device to consume the power input comprising fluctuations as generated by the renewable energy sources. Thus, waste of energy in order to protect the electrolysis cells against fluctuations in the input power can be avoided efficiently.

[0025] In a further embodiment, the electrolysis device has a plurality of electrolysis cells of the first and a plurality of electrolysis cells of the second type. In this way, a consistent capacity utilization of the electrolysis cells can be provided. In particular, the plurality of electrolysis cells can be grouped in such a way that an activation of capacity utilization of these groups can be controlled easily on the basis of a current total electrical input power. By this means, a substantially sustained operation of the electrolysis device can be secured.

[0026] In another embodiment of the electrolysis device, a ratio of a number of electrolysis cells of the second type to a number of electrolysis cells of the first type is 1 to 40, preferably 1 to 20 and especially preferable 1 to 5. After buffering the changes of the input power, said input power is repartitioned and redistributed over the electrolysis cells, in particular in the way described before. In this way, capacities of the electrolysis cells of the second type can be freed to buffer further changes in the input power. This allows to optimize the consistent capacity utilization and, hence, the overall efficiency of the electrolysis device. Moreover, a number of fast and expensive electrolysis cells of the second type can be reduced in such a way that these solely are operated to consume or buffer fluctuations in the electrical input power. The part of the input power supplied to the remaining electrolysis cells can thus be kept at a constant level as far as possible.

[0027] The system according to the invention comprises the electrolyser according to the invention.

[0028] Furthermore, said system comprises a renewable energy source generating electrical energy which is supplied as input power for operating the electrolysis device. Said renewable energy source can be a photovoltaic assembly, a concentrated solar power plant and / or a wind power plant. For example, said photovoltaic assembly is assembled as a photovoltaic array comprising of a plurality of photovoltaic modules having each multiple photovoltaic cells. This enables the deployment of an autonomous system that can be installed in regions with weak or no infrastructure.

[0029] In an embodiment, it is conceivable that said system comprises also a peripheral assembly with different peripheral modules. Such a peripheral module is for example a compressing module configured to compress the electrolysis product, a chiller module for cooling down the compressed electrolysis product, a gas cleaning module configured to clean the electrolysis product, a connecting module configured to realize a connection to transportation vehicles or transportation pipelines, or a peripheral storage module configured to store electrolysis products in gaseous or liquid state. In one embodiment, at least one of said peripheral modules is fed with at least a part of the electrical energy generated by the renewable energy source of the system. In this way, a direct and efficient consumption of generated electrical energy is enabled. Feeding energy to an external power grid or storing excess energy can be minimized. As a result, a dimension of components of the system can be significantly reduced. Moreover, in this way operation in full island mode can be provided.

[0030] The properties, features and advantages of the invention described above, as well as the manner in which they are achieved, will be explained in more detail in connection with the figures in the following description of the example and variations thereof. The example and the corresponding variations serve to explain the invention and do not limit the invention to the combinations of features indicated therein, even with respect to functional features. Moreover, any of the features disclosed in the example below may be considered in isolation and suitably combined with the features of any of the above embodiments and their further aspects.BRIEF DESCRIPTION OF THE FIGURES

[0031] It is shown in:

[0032] FIG. 1 an example of a system comprising an electrolysis device in a schematic view as well as an illustration of an example of a method for operating this electrolysis device; and

[0033] FIG. 2 a schematic illustration of the example of the method for operating the electrolysis device in form of a flowchart.DETAILED DESCRIPTION

[0034] FIG. 1 shows a schematic view of an example of a system 18. Said system 18 comprises an electrolysis device 10, a renewable energy source 20 and a peripheral assembly 22. The renewable energy source 20 is exemplary a photovoltaic assembly. Additionally or alternatively, said renewable energy source 20 can comprise a wind power plant or a concentrated solar power plant. The peripheral assembly 22 comprises exemplary various not in detail illustrated peripheral modules 24 as a compressing module configured to compress electrolysis product, a chiller module for cooling down compressed electrolysis product, a gas cleaning module configured to clean electrolysis product, a connecting module configured for realizing a connection to transportation vehicles or transportation pipelines, or a peripheral storage unit configured to store electrolysis product in a gaseous or liquid state. In one embodiment, at least one of the peripheral modules 24 is fed with electrical energy generated by the renewable energy source 20.

[0035] For the sake of simplicity, said electrolysis device 10 comprises in the present embodiment four alkaline electrolysis cells 12 and one electrolysis cell 14 having a proton exchange membrane, hereinafter referred to as PEM-cell 14. In a variation of the embodiment, said electrolysis device 10 can comprise a plurality of PEM-cells 14. Alternatively or additionally to the PEM-cells 14, electrolysis cells having an anion exchange membrane can be provided. In one embodiment, the ratio of a number of said exchange membrane cells 14 to alkaline cells 12 is between a range of 1 to 4 to 1 to 40. In the present embodiment, the ratio is 1 to 4.

[0036] Furthermore, in the present embodiment, the four alkaline electrolysis cells 12 have each the same performance parameters. Exemplary, the alkaline electrolysis cell 12 has a dynamic power parameter of 10% of its power rating per minute within an operational load range between 10% and 100% of the corresponding power rating. Said PEM-cell 14 has a dynamic power parameter of 10% of its power rating per second within an operational load range between 10% and 100% of the corresponding power rating. Consequently, the dynamic power parameter of the PEM-cell 14 is 60 times higher than that of the alkaline electrolysis cell 12. This allows the PEM-cell 14 to adapt its load 60 times faster than the alkaline electrolysis cells 12. Accordingly, the PEM-cell 14 is capable to buffer fluctuations of the input power I.

[0037] Furthermore, the electrolysis device 10 comprises a control device 16. Said control device 16 can be an analog or digital circuit known to the person skilled in the art, configured to control the electrolysis device 10. An example of a method 100 for controlling said electrolysis device 10 is illustrated in FIG. 1 as well as in FIG. 2 in the form of a schematic flowchart.

[0038] In order to control the electrolysis device 10, initially an input power I is determined 114. Said input power I is generated in the present embodiment entirely by the renewable energy source 20. In variations of the embodiment, a part of the input power I can be drawn from a not further illustrated power grid, as for example a public power grid. Afterwards, in the present embodiment the determined 114 input power I is partitioned 106 in such that the PEM-cell 14 is operated at a level of 50% of its power rating. Said operating level can, however, be variated in view of corresponding needs. The remaining part of the input power I is partitioned 106 in such that all four alkaline electrolysis cells 12 are operated with the same load. In such, the input power I is selectively directed 104 to each electrolysis cell 12, 14 of the electrolysis device 10 in order to supply 108 them with electrical energy. In a variation of the present embodiment, said partitioning 106 of the input power I can also be based on further or alternative parameters of the alkaline electrolysis cell 12 and / or parameters of the PEM-cell 14. For example such a parameter is a total or an occupied capacity, a current load, a prospective load, a temperature of the electrolysis cell and / or a dynamic performance parameter of a corresponding electrolysis cell.

[0039] By means of the control device 16 the input power I is monitored. In the case of a constant level of the input power I, it is possible to operate the electrolysis device 10 without adapting the distribution of the input power I over said electrolysis cells 12, 14. However, if a change in the input power I is detected 102, also a change in said distribution is made in accordance with the dynamic power parameter of the electrolysis cells 12, 14 of the electrolysis device 10. In the present embodiment, the detected 102 change in the input power I is at the first directed 104 to the PEM-cell 14 in accordance with its dynamic power parameter. In this way, the change in the input power I is buffered by the PEM-cell 14. If the input power I has decreased, a load of the PEM-cell 14 is instantaneously adapted to the lower input power I. Else, if the input power I has increased, the load of the PEM-cell 14 is instantaneously adapted to the higher input power I. The distribution of the parts of the input power I regarding the alkaline electrolysis cells 12 remains at the moment unamended. In a variation of the present embodiment, it is conceivable that additionally a load of the alkaline electrolysis cells 12 is adapted due to the change in the input power I in accordance with its lower dynamic power parameter.

[0040] After the detected 102 change in the input power I, the input power I is repartitioned 110 in order to operate the PEM-cell 14 again at a load of 50% of its power rating. In such, the PEM-cell 14 can serve always as a reliable buffer. The remaining part of the input power I is repartitioned 110 in such that all four alkaline electrolysis cells 12 are operated again with the same load. To achieve the new distribution of the input power I over the electrolysis cells 12, 14, a part of the input power I directed 104 to each of the alkaline electrolysis cells 12 is adjusted 112 from a currently provided part to a predetermined part based on the dynamic power parameter of the alkaline electrolysis cells 12. Accordingly, the part of the input power I directed 104 to the PEM-cell 14 is adjusted 112 from a currently provided part to a predetermined part based on the sum of the four dynamic power parameters of the four alkaline electrolysis cells 12. In this context, the sum of the dynamic power parameters of the alkaline electrolysis cells 12 may not exceed the dynamic power parameter of the PEM-cell 14.

[0041] Although the invention has been further illustrated and described in detail by the above examples, the invention is not limited by the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims

1. A method for controlling an electrolysis device, the method comprising:detecting a change in an input power; anddirecting the detected change in the input power to an electrolysis cell of a first type of the electrolysis device and / or an electrolysis cell of a second type of the electrolysis device on a basis of a first dynamic performance parameter of the electrolysis cell of the first type and / or a second dynamic performance parameter of the electrolysis cell of the second type.

2. The method according to claim 1, wherein the input power is partitioned on the basis of a parameter of an electrolysis cell of a first type and / or a parameter of an electrolysis cell of a second type and directed to said electrolysis cells in order to supply said electrolysis cells with a predetermined part of the input power.

3. The method according to claim 2, wherein, after a change in the input power, said input power is repartitioned on the basis of a parameter of the electrolysis cell of a first type and / or a parameter of the electrolysis cell of a second type in order to supply said electrolysis cells with a predetermined part of the input power.

4. The method according to claim 1, wherein a part of the input power directed to the electrolysis cell of the first type is adjusted from a currently provided part to a predetermined part based on the corresponding first dynamic performance parameter.

5. The method according claim 1, wherein a part of the input power directed to the electrolysis cell of the second type is adjusted from a currently provided part to a predetermined part based on the first dynamic performance parameter of an electrolysis cell of the first type.

6. The method according to claim 1, wherein the second dynamic performance parameter is higher than the first dynamic performance parameter.

7. The method according to claim 1, wherein the second dynamic performance parameter is at least 20 times higher, preferable at least 40 times and especially preferred at least 60 times higher than the first dynamic performance parameter.

8. The method according to claim 1, wherein the first dynamic performance parameter is in a range of values between 7%, inclusive, of a power rating of the first type electrolysis cell per minute and 13%, inclusive, of a power rating of the first type electrolysis cell per minute.

9. The method according to claim 1, wherein the second dynamic performance parameter is in a range of values between 7%, inclusive, of a power rating of the second type electrolysis cell per second and 13%, inclusive, of a power rating of the second type electrolysis cell per second.

10. An electrolysis device comprising:an electrolysis cell of a first type;an electrolysis cell of a second type; anda control device configured to:detect a change in an input power; anddirect the detected change in the input power to an electrolysis cell of a first type of the electrolysis device and / or an electrolysis cell of a second type of the electrolysis device on a basis of a first dynamic performance parameter of the electrolysis cell of the first type and / or a second dynamic performance parameter of the electrolysis cell of the second type.

11. The electrolysis device according to claim 10, wherein the electrolysis cell of the first type is an alkaline electrolysis cell.

12. The electrolysis device according to claim 10, wherein the electrolysis cell of the second type is a proton exchange membrane or an anion exchange membrane electrolysis cell.

13. The electrolysis device according to claim 10, having a plurality of electrolysis cells of the first and a plurality of electrolysis cells of the second type.

14. The electrolysis device according to claim 13, wherein a ratio of a number of electrolysis cells of the second type to a number of electrolysis cells of the first type is between 1 to 40.

15. A system comprising:an electrolysis device comprising:an electrolysis cell of a first type;an electrolysis cell of a second type; anda control device configured to:detect a change in an input power; anddirect the detected change in the input power to an electrolysis cell of a first type of the electrolysis device and / or an electrolysis cell of a second type of the electrolysis device on a basis of a first dynamic performance parameter of the electrolysis cell of the first type and / or a second dynamic performance parameter of the electrolysis cell of the second type;anda renewable energy source generating electrical energy which is supplied as input power for operating the electrolysis device.

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