WO2024223270A1 - Hybrid electrolysis plant, electrolysis system and method for controlling the power of a hybrid electrolysis plant - Google Patents

Abstract

The invention relates to a method for controlling the power of an electrolysis plant (1) which is connected to a supply line (3) and has an alkaline electrolyser (5) and a PEM electrolyser (7) connected to the supply line (3) in parallel with the alkaline electrolyser (5). An electric input power (P_E) is fed into the supply line (3) and an electric output power (P_A) is drawn off from the supply line (3) by the hybrid electrolysis plant (1), wherein a balance between the input power (P_E) and the output power (P_A) is monitored. In the event of an imbalance, the output power (P_A) is adapted to the input power (P_E), wherein a first output power (P₁) of the alkaline electrolyser (5) and/or a second output power (P₂) of the PEM electrolyser (7) is controlled, wherein, while the alkaline electrolyser (5) is being controlled, a first temporal power change rate (R₁) is applied, and in the case of the PEM electrolyser (7), a second temporal power change rate (R₂) is applied. The invention also relates to a hybrid electrolysis plant (1) having an alkaline electrolyser (3) and a PEM electrolyser (5), and to an electrolysis system (10).

Description

Description

Hybrid electrolysis plant, electrolysis system and method for power control of a hybrid electrolysis plant

The present invention relates to a hybrid electrolysis plant, an electrolysis system comprising the electrolysis plant and a method for controlling the power of the hybrid electrolysis plant.

Driven by climate change, there are currently considerable efforts to cover as high a proportion of society's total energy needs as possible from renewable energy sources. In 2010, the German government agreed on an energy concept which, among other things, envisages 80% of gross electricity consumption from renewable energies by 2050. In 2017, this share was 36%. A large proportion of this, 24.2%, was generated by onshore and offshore wind turbines and photovoltaic systems. However, wind turbines and photovoltaic systems in particular are heavily subject to weather conditions and daily and annual fluctuations in solar radiation. The electricity generated by these systems is therefore not based on current demand, but on the current environmental conditions. This gives rise to the need for energy storage technologies to compensate for these differences.

The electrochemical production of hydrogen from water represents such a storage technology, because in this way unusable electrical energy, e.g. from temporary overproduction, can be chemically bound in hydrogen, stored, transported and released for use elsewhere. For this reason, research activities have been intensified for this purpose, including on electrolyzers for water electrolysis. One possible technology path for water electrolysis is, for example, the PEM electrolysis (PEM: "polymer electrolyte membrane", also "proton exchange membrane") of water. In such PEM electrolyzers,

REPLACEMENT BLADE (RULE 26) In acids, the hydrogen produced is usually produced in a two-phase stream with circulating water, from which it must first be separated before it can be used further. Another type of electrolysis of water is alkaline electrolysis, in which, for example, potassium hydroxide KOH is fed to the electrolyzer as a reactant in a concentrated aqueous solution. High-temperature and high-pressure electrolysis are also known. Mixed forms of electrolysis are also known, such as anion-exchange membrane electrolysis, also known as AEM electrolysis for short.

Electrolysis is a widely known electrochemical method in which a direct electrical current (DC) is used to drive an otherwise non-spontaneous chemical reaction. Electrolysis has recently received increased attention as a technological approach in the fight against climate change because it can be used in so-called "Power-to-X" processes. In this process, a supply medium as a reactant, e.g. water or CO2, is usually converted into chemical energy by electrolysis using renewable electrical energy. The electrolysis products as valuable materials that contain this energy are diverse and range, for example, from from hydrogen H ₂ with 0 ₂ as a by-product through hydrocarbons such as methane CH ₄ (also known as "synthetic natural gas" SNG or synthetic LNG in liquid form), ethylene C ₂ H ₄ or ethanol C ₂ H ₅ OH to ammonia NH ₃ or carbon monoxide CO. These molecules can be used as fuel, e.g. for vehicles or generators, or as a starting material for the chemical industry.

In general, the electrolysis process must be supplied with a predictable and as constant or even as possible power consumption, while the generation of renewable energy is known to provide a fluctuating output for various reasons. For example, the amount of energy generated depends on the weather conditions or the position of the sun, for example when the electrolysis power from a wind turbine or a photovoltaic system. In addition, the amount of energy generated depends on both the current time of year and the course of the day. In order to protect electrolysis cells from damage caused by fluctuations in the input power, they must be operated in such a way that there is as little energy shortage as possible during operation. To do this, the electricity generated cannot be used up completely, but must be discarded in parts. For example, if there is a surplus on the generator side, the wind turbine is throttled down. This control intervention on the generator side is known as "wind curtailment" in a wind turbine.

The object of the present invention is to improve the efficiency of the electrolysis process with regard to a fluctuating supply of electrical power for the electrolysis, in particular when operating in an island network.

This object is achieved according to the invention by a method for controlling the power of a hybrid electrolysis system connected to a supply line, which has an alkaline electrolyzer and a PEM electrolyzer connected to the supply line in parallel to the alkaline electrolyzer, wherein an electrical input power is fed into the supply line and an electrical consumption power is taken from the supply line by the hybrid electrolysis system, wherein a balance between the input power and the consumption power is monitored, and wherein in the event of an imbalance the consumption power is adapted to the input power, wherein a first consumption power of the alkaline electrolyzer and/or a second consumption power of the PEM electrolyzer is controlled, wherein a first temporal power change rate is applied when controlling the alkaline electrolyzer and a second temporal power change rate is applied to the PEM electrolyzer. Furthermore, this task is solved by a hybrid electrolysis plant and an electrolysis system.

The invention is based on the knowledge that electrolysis systems are particularly suitable for the production of green hydrogen. The two technologies available on the market are alkaline electrolysis and proton exchange membrane electrolysis, also known as PEM electrolysis for short. However, the two electrolysis systems and the electrolyzers required for them differ significantly in terms of their costs and the possible operating dynamics when load changes. While alkaline electrolyzers, which have been available on the market for some time, are more cost-effective, the power consumption of the electrolysis direct current in alkaline electrolyzers can only be changed very slowly. The alkaline systems are therefore only suitable to a limited extent for being directly coupled to volatile generation systems, e.g. wind farms, PV parks, etc., as they cannot follow the power profile of the generation quickly enough. PEM electrolysis, on the other hand, can be controlled much more dynamically and is therefore better suited for use in combination with volatile generators. However, these advantages come at the cost of higher costs for PEM electrolysis.

An economical coupling of volatile energy generation plants with hydrogen production plants such as electrolyzers can be achieved by combining the two electrolysis technologies. The alkaline electrolysis takes over the base load, while the PEM system follows the dynamic loads, resulting in a hybrid electrolysis plant.

The invention now meets the technical challenges of controlling the hybrid electrolysis plant in such a way that the load distribution between the electrolysis systems is carried out in such a way that the PEM electrolysis follows rapid changes and the alkaline electrolysis in a is operated or remains in a load range that is as constant as possible. Since the profile of the energy fed in can only be predicted to a limited extent, the control adjustment of the power control takes place at the level of the individual systems "in situ", i.e. during operation, without any knowledge of the future load profile or at least a foreseeable high level of forecast uncertainty. The electrolysis process, which is individually controlled in this way, for example via the respective mains rectifiers for alkaline electrolysis and for PEM electrolysis, is advantageously designed as a hybrid combination of alkaline electrolysis and PEM electrolysis.

In this way, it is achieved that in the case of island operation of, for example, wind farms, when the excess power cannot be used, the so-called wind power restriction, a disadvantageous "wind curtailment", no longer has to be applied or only in exceptional cases and only to a small extent. This results in cost advantages. This type of implementation of a separate power control with characteristic respective power transients for the alkaline electrolyzer and the PEM electrolyzer implemented in the control system, results in considerable cost advantages through the adapted operation of the hybrid electrolysis process. Here, for example, the power control is implemented as power control for a respective rectifier, via which the alkaline electrolyzer and the PEM electrolyzer are connected to the supply line.

Thus, an approach is proposed that overcomes the disadvantages of the state of the art with respect to hybrid alkaline-PEM electrolysis plants, while providing efficiency advantages through rectifier control.

In the power control of the invention, an imbalance between the consumption power and the input power is continuously monitored and imbalances are compensated. chen, whereby a respective adapted load control is carried out for the alkaline electrolyzer and the PEM electrolyzer. It is possible that the input power on the supply line is provided as AC input power or as a DC supply line. The supply line is then designed as a central AC supply line or accordingly as a DC supply line, so that operation in an AC network or a DC network is possible flexibly.

It is proposed to implement a power control that uses a physical quantity that represents a power imbalance at the grid connection point of the hybrid electrolysis plant as the control input quantity and continuously monitors this quantity. In alternating voltage networks, this is preferably the grid frequency of the AG grid; in direct voltage networks, it is the direct voltage. If there is an imbalance between the fed-in input power and the consumed power, this control input quantity changes. In an alternating voltage network, for example, the grid frequency can increase if the input power is greater than the consumed power. In a direct voltage network, the grid voltage would increase in this case.

As a result, the first power consumption and the second power consumption are then increased accordingly, for example. The power control is implemented in such a way that the alkaline electrolyzer and the PEM electrolyzer have predetermined and adjustable power change rates during transient operation, which differ greatly from one another. In the event of a power imbalance, the second power consumption for the PEM electrolyzer is preferably changed much more quickly than the first power change rate for the alkaline electrolyzer. By limiting or defining the operating intervals for specific power change rates, volatile components are removed in a controlled manner by the PEM system. whereas with the alkaline electrolyzer, the first power consumption is hardly adjusted in the event of short power changes. A new operating point of the alkaline electrolyzer is only reached with a considerable time delay.

However, if there is an imbalance in performance over a longer period of time, the alkaline electrolyzer is adjusted and adjusted to a new operating point, so that an adjusted, e.g. increased, base load reduction is advantageously achieved by the alkaline electrolyzer. This approach allows alkaline and PEM systems to be combined and operated in a hybrid electrolysis plant without directly coupling the respective performance control. Such a control concept can therefore also be easily expanded by connecting additional electrolyzers.

It is particularly advantageous that the control concept allows fluctuations in the input power, i.e. those caused by the generator side, to be distributed in a targeted manner across the electrolysis system between the alkaline electrolyzer and the PEM electrolyzer by means of appropriate current supply. In this way, fluctuations and imbalances in the power balance can be significantly reduced or buffered depending on the respective specified first and second power change rates. This enables a corresponding hybrid electrolysis system to use the generated volatile renewable input power almost completely for electrolysis purposes despite fluctuations occurring, so that the efficiency with regard to the volatile renewable energy that can be used for electrolysis purposes is increased.

In a particularly preferred embodiment of the method, the first power consumption is taken via a first rectifier and supplied as direct current power to the alkaline electro- lyser and the second power consumption is taken via a second rectifier and fed to the PEM electrolyser.

In this case, controllable and adjustable rectifiers are used as the first and second rectifiers, so that individual regulation and control of the first power consumption and the second power consumption can be carried out at the respective network connection point of the electrolyzers. For example, a phase control can be implemented for the power control in the rectifiers. This advantageously makes it possible to connect and flexibly adapt the power control to a supply line designed as an AG network via an independent rectifier control for the alkaline electrolyzer and the PEM electrolyzer.

In the method, the second power change rate of the second rectifier is preferably set greater than the first power change rate of the first rectifier.

As a result, both rectifiers - the first rectifier of the alkaline electrolyzer and the second rectifier of the PEM electrolyzer - adjust and track the respective power consumption with a specific power change rate using rectifier control alone. Due to the intended differences in the respective specified power change rate, in the event of an imbalance the second power consumption of the second rectifier in the PEM electrolyzer is changed much more quickly than is done via the first rectifier in the alkaline electrolyzer. By limiting the change rates in this way, volatile components are automatically taken up primarily by the PEM system by the power control, while the alkaline system hardly reacts to short power changes.

In a preferred embodiment of the method, it is proposed that the second power change rate be at least 20 times higher. preferably at least 40 times and particularly preferably at least 60 times higher than the first power change rate.

This enables immediate consumption and almost instantaneous tracking of a detected change in the input power, primarily by the PEM electrolyzer. Additional devices for absorbing or buffering these changes, such as capacitors or batteries, can be avoided or made significantly smaller.

For a further preferred embodiment of the method, it is provided that the first power change rate is set in a value range of 5% to 15% per minute with respect to the nominal power of the alkaline electrolyzer. Particularly preferably, a value range of 7% to 13% per minute with respect to the nominal power of the alkaline electrolyzer can be set or passed through for a transient.

In this context, the nominal power is the highest peak electrical power as the maximum power consumption that can be provided for the continuous operation of the corresponding electrolyzer. This load profile for power control and in transient operation is adapted to alkaline electrolysis cells, as installed in large numbers in an alkaline electrolysis plant. Such electrolysis cells with this load profile are frequently used because they are inexpensive to manufacture and offer good base load capabilities.

For a further preferred embodiment of the method, it is proposed that the second power change rate is set in a value range of 5% to 15% per second with respect to the nominal power of the PEM electrolyzer. Particularly preferably, a value range of 7% to 13% per second with respect to the nominal power of the PEM electrolyzer can be set or run through for a transient. For example, this load profile can be realized by means of an electrolyzer with an electrolysis cell with a proton exchange membrane or an anion exchange membrane. In particular, the electrolysis electrodes of the electrolysis cells mentioned are deposited directly on the conductive membrane. In contrast to classic electrolysis cells, e.g. with alkaline electrolysis, the proton or anion exchange membrane enables a very rapid adjustment of a production rate and thus an adjustment of the second take-off power to a change in the input power.

Preferably, in the method, when the input power increases very quickly, which is greater than the second power change rate, the excess electrical energy is stored in an energy storage device connected to the supply line.

In order to additionally enable the absorption of very fast load peaks, a short-term grid storage system can be provided as an energy storage system, for example designed as an energy storage system based on supercapacitors or on a flywheel storage system. The energy storage system can then, if required, absorb such high power changes, i.e. very steep, short-term transients or peak loads, for which even the load change dynamics of a PEM electrolyzer are too slow.

In this case, the method preferably proposes that energy stored in the energy storage device is taken and fed into the supply line as electrical power.

This makes it possible to feed back and use stored energy for electrolysis purposes in the electrolysis plant, thus further increasing efficiency. The empty energy storage unit is then available again to absorb peak loads and store energy. In a particularly preferred embodiment of the method, the power control of the hybrid electrolysis plant is carried out in such a way that the alkaline electrolyzer is operated at the highest possible first power consumption of at least 70%, preferably more than 80%, of its nominal power.

The primary control objective is to ensure that the alkaline electrolyzer is fully utilized in order to achieve the highest and most stable base load or base load possible as the operating point of the electrolysis plant, and the first power consumption is implemented accordingly in the power control. Longer-term and quasi-stationary input power is therefore primarily fed to the alkaline electrolyzer for electrolysis, which is supplied with power via the adjustable and controllable first rectifier.

This primary control premise implemented in the power control prevents practically all excess input power from always being absorbed by the PEM electrolyzer and/or the energy storage unit. For this purpose, additional, higher-level control loops are preferably implemented in the power control. An energy storage unit as described above should therefore practically always be empty in the long term, while the alkaline electrolyzer is operated in a quasi-stationary manner with the highest possible initial consumption power and high base load. These higher-level control objectives mean that the electrolysis plant can be operated with a higher level of efficiency overall and can be used, for example, for increased hydrogen production. Changes in power can be efficiently followed up and absorbed in this way.

In addition, the method can preferably provide for the power control to be carried out in such a way that forecast data for the input power are regularly used and a respective target value is specified based on the forecast data for the first power consumption and the second power consumption. One advantageous way to implement power control is to use available wind forecast data or other weather data at regular intervals - approximately every 15 minutes - and, based on a resulting forecast of the input power, to set the first power consumption and the second power consumption as target power or setpoint power of the alkaline electrolyzer or the PEM electrolyzer according to a predetermined distribution. The forecast data is updated regularly and the electrolysis plant is adjusted accordingly.

A further aspect of the invention relates to a hybrid electrolysis plant for carrying out the process according to the invention.

The hybrid electrolysis plant comprises an alkaline electrolyzer and a PEM electrolyzer as well as a control device which is designed to carry out the method for power control.

The hybrid electrolysis system comprises an electrolysis cell with a cell structure for alkaline electrolysis and an electrolysis cell with a cell structure for a PEM electrolyzer. The hybrid electrolysis system preferably comprises several electrolysis cells of each of the two types, which can be stacked to form a respective electrolysis module. An alkaline electrolyzer or a PEM electrolyzer can have several electrolysis modules connected in series. In particular, the electrolysis cells are each set up in such a way that they generate an electrolysis product from a supply medium by means of supplied electrical energy. The electrolysis cells preferably convert the supply medium water into H ₂ and 0 _2. However, it is also possible that the supply of C0 ₂ and water as educts of an electrolysis leads to carbon monoxide CO, small hydrocarbons or small oxygen-containing compounds as electrolysis products. In a particularly preferred embodiment of the hybrid electrolysis plant, a rectifier control is implemented in the control device so that a respective power control of the first rectifier and the second rectifier can be carried out.

This advantageously results in independent load control of the alkaline electrolyzer and the PEM electrolyzer in the network in a hybrid electrolysis plant. The power control and load distribution is implemented individually and independently via the rectifier system with the first rectifier and the second rectifier in the hybrid electrolysis plant by means of a controllable rectifier. The first rectifier and the second rectifier can be controlled individually and independently in such a way that the first power consumption and the second power consumption can be adjusted as direct current power at the output of the respective rectifier. A phase control can advantageously be provided for adjusting the power consumption and the individual current supply. For example, in a thyristor-based rectifier the ignition pulse of the thyristors can be controlled via a control pulse. After the control pulse has gone out, the current flow continues until the next zero crossing. By shifting the switch-on time, the energy or power that flows to the consumer at the output can be changed. However, the concept of power control and distribution of power between the first rectifier and the second rectifier is not limited to a specific type of circuit implementation of the rectification.

Preferably, the hybrid electrolysis plant is provided with an energy storage device designed as a short-term grid storage device, which in particular has a supercapacitor or a flywheel storage device.

This is advantageous in order to be able to accommodate very fast load peaks if required. The resulting The energy storage system can be activated in the event of large changes in power and can absorb those load peaks for which the dynamics of the PEM electrolysis are too slow. The energy stored in the energy storage system is to be fed back promptly so that the power consumption and power output of the hybrid electrolysis system can be kept in balance even in the event of a transient change in the input power on the generator side.

The electrolysis system according to the invention comprises a hybrid electrolysis plant according to the invention.

In addition, the electrolysis system comprises a renewable energy plant that generates electrical energy that is supplied as input power for operating the electrolysis device and fed into the utility line. This renewable energy plant can be a photovoltaic plant, a solar thermal power plant and/or a wind turbine. For example, the photovoltaic assembly is constructed as a photovoltaic plant consisting of a plurality of photovoltaic modules, each having several photovoltaic cells. This enables the use of an autonomous system, a so-called island grid, which can be installed in regions with little or no infrastructure.

The electrolysis system is therefore preferably designed such that the hybrid electrolysis plant is connected to the renewable energy plant via a supply line designed as a central AC line, whereby an island network is formed.

Further advantages, features and details of the invention emerge from the following description of preferred embodiments and from the drawing. The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and/or shown alone in the single figures are not only in the respective wells, but also in other combinations or on its own, without departing from the scope of the invention.

Examples of the invention are explained in more detail with reference to a drawing. This shows schematically and in a highly simplified manner the

FIG an electrolysis system with a renewable energy plant and with a hybrid electrolysis plant.

The only FIG shows a schematic representation of an electrolysis system 10 with a renewable energy system 15 and with a hybrid electrolysis system 1. The renewable energy system 15 has a wind energy system 15A and a photovoltaic system 15B, so that during operation an electrical input power P _E obtained from renewable energy generation - in the present embodiment as an alternating current power - can be fed into the supply line 3. The hybrid electrolysis system 1 comprises an alkaline electrolyzer 5 and a PEM electrolyzer 7, wherein the electrolyzers 5, 7 are each connected to the central supply line 3 at separate network connection points. This provides an alternating current-based island network. The alkaline electrolyzer 5 is connected to the supply line 3 via a first rectifier 9A and the PEM electrolyzer 7 via a second rectifier 9B, so that a parallel connection is realized. A respective rectifier 9A, 9B supplies a respective electrolyzer 5, 7 with a regulated direct current for the electrolysis. An energy storage device 11 is additionally connected to the supply line 3 at a separate network connection point via a further rectifier 9. The alkaline electrolyzer 5 has a number of alkaline electrolysis modules 17 connected in series, each with a plurality of alkaline electrolysis cells. Accordingly, the PEM electrolyzer 7 comprises a number of electrolysis modules 19 connected in series, each with a Large number of PEM electrolysis cells. Due to its modularity, the hybrid electrolysis storage 1 is scalable and designed for large power consumption P _A and can be expanded accordingly.

To regulate the power of the hybrid electrolysis plant 1, a control device 13 is provided which is designed to regulate and distribute the fed-in input power P _E in order to achieve as much balance as possible with the consumption power P _A of the hybrid electrolysis plant 1. A specific load control of the consumers involved is implemented in the control device 13, which includes the alkaline electrolyzer 5, the PEM electrolyzer 7 and the energy storage device 11 and individually controls their load over time. For this purpose, the control device 13 supplies a respective control signal Si, S ₂ , S at its output, which in each case acts on the assigned rectifier 9A, 9B, 9. The first rectifier 9A is controlled via the control signal Si, so that a first power consumption P ₂ specified by the control device 13 is decoupled from the supply line 3 and fed to the alkaline electrolyzer 5 as direct current power. The second rectifier 9B is correspondingly controlled via the control signal S ₂ , so that a second power consumption P ₂ specified by the control device 13 is decoupled from the supply line 3 and fed to the PEM electrolyzer 7 as direct current power. In addition, during peak loads on the generator side, electrical energy can be temporarily stored in the energy storage device 11 with a storage line P _s and, if required, stored again in the supply line 3. For this purpose, the rectifier 9 is set up for bidirectional operation and connected to the grid connection point.

During operation of the electrolysis system 10, an electrical input power P _E is fed into the supply line 3 and an electrical consumption power P _A is taken from the supply line 3 by the hybrid electrolysis system 1. In this case, a Equilibrium between the input power P _E and the power consumption P _A is monitored, wherein in the event of an imbalance the power consumption P _A is adapted to the input power P _E , wherein a first power consumption P ₂ of the alkaline electrolyzer 5 and/or a second power consumption P ₂ of the PEM electrolyzer 7 is regulated. The alkaline electrolyzer 5 is regulated using a first temporal power change rate Ri, and a second temporal power change rate R ₂ is applied to the PEM electrolyzer 7. The temporal power change rate R ₂ is many times greater than the temporal change rate R ₂ , typically in the range of a factor of 20 to 60. This results in adapted load control, in which the power consumption P ₂ for the alkaline electrolyzer 5 is changed and adjusted more slowly over time, while for the PEM electrolyzer 7 the power consumption P ₂ is changed much more quickly and the PEM electrolyzer 7 can therefore be moved to a changed operating point in a timely manner. The diagrams shown in the FIG for the respective rectifier 9A, 9B, 9 show the power P over time t. The qualitative course of the volatile input power P _E and the respective temporal course of the regulated power consumption P ₂ , P ₂ , P _s are shown in accordance with the rectifier control implemented in the control device 13. Over time, the control device 13 causes specifically different transients in the input power P ₂ , P ₂ and the storage power P _s , so that an equilibrium between input power P _E and output power P _A is maintained or achieved again.

For example, if the input power P _E is increased, the first power consumption P ₂ and the second power consumption P ₂ are increased for both rectifiers 9A, 9B. The value ranges for the power change rates R ₂ , R ₂ implemented in the power control of the control device 13 result from the respective derivative dP ₂ ( t ) /dt or dP ₂ ( t ) /dt - i.e. the change in the respective power consumption P ₂ , P ₂ per Time or a so-called power transient. The set and permissible value ranges for the power change rates Ri, R ₂ as a systemic reaction to a changed input power P _E differ considerably - by one to two orders of magnitude - for the alkaline electrolyzer 3 and for the PEM electrolyzer 7. The adaptation and control of the power consumption P ₂ , P ₂ takes place via the respective control of the first rectifier 9A and the second rectifier 9B.

If a power imbalance is detected, the control device 13 controls the second rectifier 9B of the PEM electrolyzer 7 in such a way that the second power consumption P ₂ is changed and adjusted much more quickly, even in the matter of seconds, than the first power consumption P ₂ of the first rectifier 9A, which supplies the alkaline electrolyzer 5 with direct current power. By limiting the value range of the power change rates R ₂ , R _{2 ,} volatile components are automatically taken up primarily by the PEM electrolyzer 7, while the alkaline electrolyzer 5 hardly reacts to short-term power changes. However, if a power imbalance occurs over a longer period of time on a time scale in the minute range corresponding to the power change rate R ₂ , the alkaline electrolyzer 5 is also adjusted and tracked here, so that the alkaline electrolyzer 7 dynamically adjusts to a base load consumption. This approach allows the alkaline electrolyzer 5 and the PEM electrolyzer 7 to be advantageously combined in the electrolysis system 10 without directly coupling the respective control of the electrolyzers 5, 7. Such an electrolysis system 10 is therefore also easily expandable with regard to a large input line and can be scaled accordingly in an electrolysis plant 1. This load control enables the alkaline electrolyzer 5 to be operated as continuously and quasi-stationary as possible at the highest possible first consumption power P ₂ of more than 70% of its nominal power, for example 85%. PEM electrolyzer 7 is operated more dynamically during transients because PEM electrolyzer 7 is better designed to react to short-term load changes. In order to maintain a corresponding dynamic power reserve for a higher and a lower second power consumption P ₂ if required, it is intended to operate PEM electrolyzer 7 on average over time in partial load operation, for example at an average partial load of 40% to 60% or a high partial load between 60% and 75% of its nominal load. Appropriate operating control for PEM electrolyzer 7 is implemented in control device 13 so that a control signal S ₂ can be output for second rectifier 9B to supply direct current to PEM electrolyzer 7. For capacity control, the control device 13 is upgraded for power control in such a way that forecast data for the input power P _E can be regularly used and read in, so that based on the forecast data for the first power consumption P ₂ and the second power consumption P ₂ a respective target value is determined and corresponding control signals S ₂ , S ₂ for the rectifiers 9A, 9B of the electrolyzers 5 , 7 and, if required, the rectifier 9 for the operation of the energy storage device P _s .

Claims

patent claims 1. Method for power control of a hybrid electrolysis system (1) connected to a supply line (3), which has an alkaline electrolyzer (5) and a PEM electrolyzer (7) connected to the supply line (3) in parallel to the alkaline electrolyzer (5), wherein an electrical input power (P _E ) is fed into the supply line (3) and an electrical consumption power (P _A ) is taken from the supply line (3) by the hybrid electrolysis system (1), wherein a balance between the input power (P _E ) and the consumption power (P _A ) is monitored, and wherein in the event of an imbalance the consumption power (P _A ) is adapted to the input power (P _E ), wherein a first consumption power (P ₂ ) of the alkaline electrolyzer (5) and/or a second consumption power (P ₂ ) of the PEM electrolyzer (7) is controlled, wherein when controlling the alkaline electrolyzer (5), a first rate of change in power over time (Ri) and in the PEM electrolyzer (7) a second temporal power change rate (R ₂ ) is applied. 2. Method according to claim 1, wherein the first power consumption (P ₂ ) is taken via a first rectifier (9A) and supplied as direct current power to the alkaline electrolyzer (5) and the second power consumption (P ₂ ) is taken via a second rectifier (9B) and supplied to the PEM electrolyzer (7). 3. The method according to claim 2, wherein the second power change rate (R ₂ ) of the second rectifier (9B) is set greater than the first power change rate (R ₂ ) of the first rectifier (9A). 4. Method according to claim 1, wherein the second power change rate (R ₂ ) is at least 20 times higher, preferably at least 40 times and particularly preferably set at least 60 times higher than the first power change rate (Ri) . 5. Method according to one of the preceding claims, wherein the first power change rate (Ri) is set in a value range of 5% to 15% per minute with respect to the nominal power of the alkaline electrolyzer (5). 6. Method according to one of the preceding claims, wherein the second power change rate (R2) is set in a value range of 5% to 15% per second with respect to the nominal power of the PEM electrolyzer (7). 7. Method according to one of the preceding claims, wherein in the case of a very rapid increase in the input power which is greater than the second power change rate (R2), the excess electrical energy is stored in an energy storage device (11) connected to the supply line (3). 8. The method according to claim 7, wherein energy stored in the energy storage device (11) is taken and fed into the supply line (3) as electrical power. 9. Method according to one of the preceding claims, wherein the power control of the hybrid electrolysis plant (1) is carried out such that the alkaline electrolyzer (5) is operated at a first consumption power (Pi) as high as possible of at least 70%, preferably more than 80%, of its nominal power. 10. The method according to claim 9, wherein the power control is carried out such that forecast data for the input power (P _E ) are regularly used and a respective target value is specified based on the forecast data for the first power consumption (Pi) and the second power consumption (P ₂ ). 11. Hybrid electrolysis plant (1) comprising an alkaline electrolyzer (3) and a PEM electrolyzer (5) and a control device (13) which is designed to carry out the method for power control according to one of claims 1 to 10. 12. Hybrid electrolysis plant (1) according to claim 11, wherein a rectifier control is implemented in the control device (), so that a respective power control of the first rectifier (9A) and the second rectifier (9B) can be carried out. 13. Hybrid electrolysis plant (1) according to claim 11 or 12, with an energy storage device (11) designed as a short-term grid storage device, which in particular has a supercapacitor or a flywheel storage device. 14. Electrolysis system (10) comprising: a hybrid electrolysis plant (1) according to one of the preceding claims 11 to 13; a renewable energy plant (15) which generates electrical energy which is supplied as input power (P _E ) for the operation of the electrolysis device (10) and fed into the supply line. 15. Electrolysis system (10) according to claim 14, in which the hybrid electrolysis system (1) is connected to the renewable energy system (15) via a supply line (3) designed as a central AG line, whereby an island network is formed.