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

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 (PE) is fed into the supply line (3) and an electric output power (PA) is drawn off from the supply line (3) by the hybrid electrolysis plant (1), wherein a balance between the input power (PE) and the output power (PA) is monitored. In the event of an imbalance, the output power (PA) is adapted to the input power (PE), 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

[0001] Description

[0002] Hybrid electrolysis plant, electrolysis system and method for power control of a hybrid electrolysis plant

[0003] 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.

[0004] At present, driven by climate change, there are considerable efforts to cover as high a proportion of society's total energy needs as possible from renewable energy sources. In 2010, the German Federal Government agreed on an energy concept which, among other things, envisages renewable energies accounting for 80% of gross electricity consumption 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 exposed 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 ambient conditions. This gives rise to the need for energy storage technologies to compensate for these differences.

[0005] 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. Therefore, research activities have been intensified, including on electrolyzers for water electrolysis. One possible technology path for water electrolysis, for example, is PEM electrolysis (PEM: "polymer electrolyte membrane," also "proton exchange membrane") of water. In such PEM electrolyzers,

[0006] REPLACEMENT SHEET (RULE 26) In electrolysis, the hydrogen produced is usually obtained in a two-phase stream with circulating water, from which it must first be separated before it can be used further. Another type of water electrolysis is alkaline electrolysis, in which, for example, potassium hydroxide KOH in concentrated aqueous solution is fed to the electrolyzer as the reactant. 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.

[0007] 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 of its potential for use in so-called "Power-to-X" processes. In these processes, a feedstock such as water or CO2 is typically converted into chemical energy through electrolysis using renewable electrical energy. The electrolysis products, which contain this energy, are diverse and range from hydrogen H2 with O2 as a by-product to hydrocarbons such as methane CH4 (also known as "synthetic natural gas" SNG or synthetic LNG in liquid form), ethylene C2H4 or ethanol C2H5OH to ammonia NH3 or carbon monoxide CO. These molecules can be used as fuel, e.g.for vehicles or generators, or as a raw material for the chemical industry.

[0008] In general, the electrolysis process must be supplied with a predictable and, if possible, constant or even power input, whereas the generation of renewable energies is known to deliver fluctuating output for a variety of reasons. For example, the amount of energy generated depends on weather conditions or the position of the sun, as is the case when the electrolysis power is provided by 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. To protect electrolysis cells from damage caused by fluctuations in input power, they must be operated in such a way that no energy shortage occurs during operation. To achieve this, the electricity generated cannot be used up completely, but must be discarded in parts. For example, if there is a surplus power on the generator side, the wind turbine is throttled back.This control intervention on the generator side is referred to as "wind curtailment" in a wind turbine.

[0009] 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 operated in an island network.

[0010] This object is achieved according to the invention by a method for power control of a hybrid electrolysis plant connected to a supply line, which has an alkaline electrolyzer and a PEM electrolyzer connected to the supply line in parallel with 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 plant, 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 regulated,Wherein, a first temporal power change rate is applied to the control of the alkaline electrolyzer, and a second temporal power change rate is applied to the control of the PEM electrolyzer. Furthermore, this task is solved by a hybrid electrolysis plant and an electrolysis system.

[0011] 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 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., because 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 PEM electrolysis.

[0012] A cost-effective coupling of volatile power generation plants with hydrogen production facilities such as electrolyzers can be achieved by combining the two electrolysis technologies. Alkaline electrolysis covers the base load, while the PEM system tracks the dynamic loads, resulting in a hybrid electrolysis plant.

[0013] The invention now meets the technical challenge of controlling the hybrid electrolysis plant in such a way that the load is distributed between the electrolysis systems in such a way that the PEM electrolysis follows rapid changes and the alkaline electrolysis 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 power control is adjusted in situ at the level of the individual systems, i.e. during operation, without any knowledge of the future load profile or at least a foreseeable high forecast uncertainty. The load generated in this way, for example,The electrolysis process, which is individually controlled by the mains rectifiers for alkaline electrolysis and PEM electrolysis, is advantageously designed as a hybrid combination of alkaline electrolysis and PEM electrolysis.

[0014] In this way it is achieved that in the case of island operation of, for example, wind farms, when the surplus 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.

[0015] Thus, an approach is proposed that overcomes the disadvantages of the state of the art with regard to hybrid alkaline-PEM electrolysis systems, with efficiency advantages resulting from the rectifier control.

[0016] With the power control of the invention, an imbalance between the consumed power and the input power is continuously monitored, and imbalances are compensated for, with a respective adapted load control being carried out for the alkaline electrolyzer and the PEM electrolyzer. It is possible for the input power to be provided on the supply line 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 grid or a DC grid is possible flexibly.

[0017] The proposal is to implement power control which uses a physical variable representing a power imbalance at the grid connection point of the hybrid electrolysis plant as the control input variable and which continuously monitors this variable. In AC grids, this is preferably the grid frequency of the AG grid; in DC grids, it is the DC voltage. If there is an imbalance between the fed-in input power and the consumed power, this control input variable changes. In an AC grid, for example, the grid frequency can rise if the input power is greater than the consumed power. In a DC grid, the grid voltage would increase in this case.

[0018] As a result, the first and 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 each have predetermined and adjustable power change rates that differ greatly from one another during transient operation. 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 taken up by the PEM system in a controlled manner, whereas in the alkaline electrolyzer the first power consumption is hardly adjusted during short power changes.A new operating point of the alkaline electrolyzer is only reached with a considerable time delay.

[0019] However, if a power imbalance persists over a longer period of time, the alkaline electrolyzer is adjusted and tracked to a new operating point, advantageously resulting in an adjusted, e.g., increased, base load draw 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 power control. Such a control concept can therefore be easily expanded by connecting additional electrolyzers.

[0020] A particular advantage is that the control concept specifically distributes fluctuations in input power, i.e. those caused by the generator side, across the electrolysis plant 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 respectively specified first and second power change rates. This enables a corresponding hybrid electrolysis plant to use the generated volatile renewable input power almost entirely for electrolysis purposes despite occurring fluctuations, thus increasing the efficiency with regard to the volatile renewable energy that can be used for electrolysis purposes.

[0021] 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 electrolyzer and the second power consumption is taken via a second rectifier and supplied to the PEM electrolyzer.

[0022] Controllable and adjustable rectifiers are used as the first and second rectifiers, respectively, allowing individual regulation and control of the first power consumption and the second power consumption at the respective grid connection point of the electrolyzers. For example, a phase-angle control can be implemented for power control in the rectifiers. This advantageously enables connection and flexibly adjustable power control to a supply line designed as an AG grid via independent rectifier control for the alkaline electrolyzer and the PEM electrolyzer.

[0023] 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.

[0024] As a result, the respective power consumption of both rectifiers - the first rectifier of the alkaline electrolyzer and the second rectifier of the PEM electrolyzer - is adjusted and tracked at a specific power change rate using a rectifier control system alone. Due to the planned differences in the respectively 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 by the PEM system as a priority by the power control system, while the alkaline system hardly reacts to short power changes.

[0025] In a preferred embodiment of the method, it is proposed that the second power change rate is set at least 20 times higher, preferably at least 40 times and particularly preferably at least 60 times higher than the first power change rate.

[0026] This enables immediate consumption and almost instantaneous tracking of any detected change in 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.

[0027] For a further preferred embodiment of the method, it is provided that the first power change rate is set within 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.

[0028] In this context, the rated power is the highest peak electrical power, the maximum power consumption, that may be provided for continuous operation of the corresponding electrolyzer. This load profile for power control and during transient operation is adapted to alkaline electrolysis cells, such as those installed in large numbers in alkaline electrolysis systems. Such electrolysis cells with this load profile are frequently used because they are inexpensive to manufacture and offer good base load capabilities.

[0029] 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 passed 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 said electrolysis cells are deposited directly on the conductive membrane. In contrast to classic electrolysis cells, e.g.with alkaline electrolysis, the proton or anion exchange membrane allows a very rapid adjustment of a production rate and thus an adjustment of the second take-up power to a change in the input power.

[0030] Preferably, in the method, in the event of a very rapid increase in the input power 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.

[0031] To further accommodate very rapid load peaks, a short-term grid storage system can be used as an energy storage device, for example, one based on supercapacitors or a flywheel storage system. The energy storage system can then accommodate 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.

[0032] 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.

[0033] This allows the stored energy to be fed back into the electrolysis plant and used for electrolysis purposes, 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 designed such that the alkaline electrolyzer is operated at the highest possible initial power consumption of at least 70%, preferably more than 80%, of its rated power.

[0034] The primary control objective is to ensure that the alkaline electrolyzer is fully utilized to achieve the highest and most stable base load or base capacity as the operating point of the electrolysis plant, and the first power consumption is implemented accordingly in the power control. Thus, longer-term and quasi-stationary input power is primarily supplied to the alkaline electrolyzer for electrolysis, which is supplied with power via the adjustable and controllable first rectifier.

[0035] This overriding 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. A planned 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 mode with the highest possible initial power consumption and a 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. In this way, changes in power can be efficiently tracked and absorbed.

[0036] 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, based on the forecast data, a respective setpoint is specified for the first power consumption and the second power consumption. Advantageously implementable, for example, is a power control which, for example, uses 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, the first power consumption and the second power consumption are set as target powers or setpoint powers of the alkaline electrolyzer or the PEM electrolyzer according to a predetermined distribution. The forecast data are updated regularly and the electrolysis plant is adjusted accordingly.

[0037] A further aspect of the invention relates to a hybrid electrolysis plant for carrying out the process according to the invention.

[0038] 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 power control method.

[0039] 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. Preferably, the hybrid electrolysis system 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 designed to generate an electrolysis product from a supply medium by means of supplied electrical energy. Preferably, the electrolysis cells convert the supply medium water into H2 and O2. However, it is also possible for the supply of CO2 and water as reactants in an electrolysis to lead 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.

[0040] 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 are 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 such that the first power consumption and the second power consumption can be adjusted as direct current power at the output of the respective rectifier. Advantageously, a phase control can be provided for adjusting the power consumption and the individual current supply. For example, in a thyristor-based rectifier the firing pulse of the thyristors can be controlled via a control pulse.After the control pulse is extinguished, the current flow continues until the next zero crossing. By shifting the switch-on time, the energy or power flowing to the load at the output can be changed. However, the concept of power control and power distribution between the first rectifier and the second rectifier is not limited to a specific type of circuit implementation of the rectification.

[0041] Preferably, the hybrid electrolysis plant is provided with an energy storage device designed as a short-term grid storage device, which in particular comprises a supercapacitor or a flywheel storage device.

[0042] This is advantageous because it allows for the additional absorption of very rapid load peaks, if necessary. The energy storage system designed in this way can be activated during significant power fluctuations and absorb those load peaks for which even the dynamics of PEM electrolysis are too slow. A prompt feed-back of the energy stored in the energy storage system is provided, so that in the hybrid electrolysis system, the power consumption and power output can be kept in balance even in the event of a transient change in the input power on the generator side.

[0043] The electrolysis system according to the invention comprises a hybrid electrolysis plant according to the invention.

[0044] In addition, the electrolysis system includes a renewable energy plant that generates electrical energy that is supplied as input power for operating the electrolysis device and fed into the utility grid. This renewable energy plant can be a photovoltaic system, a solar thermal power plant, and / or a wind turbine. For example, the photovoltaic assembly is constructed as a photovoltaic array 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.

[0045] The electrolysis system is therefore preferably designed in such a way that the hybrid electrolysis plant is connected to the renewable energy plant via a supply line designed as a central AC string, whereby an island network is formed.

[0046] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. 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 can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0047] Examples of the invention are explained in more detail with reference to the accompanying drawings. These show schematically and in a highly simplified manner the

[0048] FIG an electrolysis system with a renewable energy plant and with a hybrid electrolysis plant.

[0049] The sole FIGURE shows a schematic representation of an electrolysis system 10 with a renewable energy plant 15 and with a hybrid electrolysis plant 1. The renewable energy plant 15 has a wind turbine 15A and a photovoltaic plant 15B, so that during operation an electrical input power P obtained from renewable energy generation E- in the present embodiment as an alternating current power - is provided and 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 grid connection points. This provides an alternating current-based island grid. 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 grid 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 plurality of PEM electrolysis cells. Due to its modularity, the hybrid electrolysis unit 1 is scalable and suitable for large power consumption P. A designed and expandable accordingly.

[0050] For the power control of the hybrid electrolysis plant 1, a control device 13 is provided, which with regard to the control and distribution of the fed-in input power P E to achieve, if possible, an equilibrium with the power consumption P Athe hybrid electrolysis plant 1 is designed. In this case, a specific load control of the consumers involved is implemented in the control device 13, which comprises 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, S2, S at its output, which in each case acts on the assigned rectifier 9A, 9B, 9. In this case, the first rectifier 9A is controlled via the control signal Si, so that a first power consumption P2 predetermined by the control device 13 is coupled out of the supply line 3 and supplied to the alkaline electrolyzer 5 as direct current power.Accordingly, the second rectifier 9B is controlled via the control signal S2, so that a second power consumption P2 specified by the control device 13 is extracted from the supply line 3 and supplied to the PEM electrolyzer 7 as direct current power. In addition, during peak loads on the generator side, electrical energy can be fed into the energy storage device 11 via a storage line P. s temporarily stored and, if necessary, released into the supply line 3. For this purpose, the rectifier 9 is configured for bidirectional operation and connected to the grid connection point.

[0051] During operation of the electrolysis system 10, an electrical input power P E fed into the supply line 3 and an electrical power consumption P Afrom the hybrid electrolysis plant 1 in total from the supply line 3. In this case, a balance is maintained between the input power P E and the power consumption P A monitored , whereby in case of an imbalance the power consumption P A to the input power P Eis adjusted, wherein a first power consumption P2 of the alkaline electrolyzer 5 and / or a second power consumption P2 of the PEM electrolyzer 7 is regulated. The alkaline electrolyzer 5 is controlled using a first temporal power change rate Ri, and a second temporal power change rate R2 is applied to the PEM electrolyzer 7. The temporal power change rate R2 is many times greater than the temporal change rate R2, typically in the range of a factor of 20 to 60. This results in adjusted capacity control, in which the power consumption P2 for the alkaline electrolyzer 5 is changed and adjusted more slowly over time, while the power consumption P2 for the PEM electrolyzer 7 is changed significantly 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 FIGURE for the respective rectifiers 9A, 9B, 9 show the power P over time t. Here, P is the qualitative curve of the volatile input power. E and the respective temporal course of the regulated power consumption P2, P2, P s shown in accordance with the rectifier control implemented in the control device 13. Over time, the control device 13 specifically detects different transients in the power consumption P2, P2 and the storage power P s causes a balance between input power P E and power consumption P A maintained or reached again.

[0052] For example, with an increased input power P EFor both rectifiers 9A, 9B, the first power consumption P2 and the second power consumption P2 are increased. The value ranges for the power change rates R2, R2 implemented in the power control of the control device 13 result from the respective derivative dP2(t) / dt or dP2(t) / dt - i.e., the change in the respective power consumption P2, P2 per time or a so-called power transient. The set and permissible value ranges for the power change rates Ri, R2 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 adjustment and control of the power consumption P2, P2 is carried out via the respective control of the first rectifier 9A and the second rectifier 9B.

[0053] 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 P2 is changed and adjusted significantly faster, already in the range of seconds, than the first power consumption P2 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 R2, R2, volatile components are automatically and primarily taken by the PEM electrolyzer 7, while the alkaline electrolyzer 5 reacts almost unnoticed to short-term power changes.However, if a power imbalance persists over a longer period on a time scale in the minute range corresponding to the power change rate R2, the alkaline electrolyzer 5 is also adjusted and tracked, so that the alkaline electrolyzer 7 dynamically adapts to a base load decrease. 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 correspondingly scalable in an electrolysis plant 1.Through this load control, the alkaline electrolyzer 5 is operated as continuously and quasi-stationarily as possible at the highest possible first power consumption P2 of more than 70% of its nominal power, for example 85%. The PEM electrolyzer 7 is operated more dynamically during transients, as the PEM electrolyzer 7 is better designed for responding to short-term load changes. In order to maintain an appropriate dynamic power reserve for a higher and a lower second power consumption P2, as needed, the PEM electrolyzer 7 is intended to be operated on average over time at partial load, for example at a medium partial load of 40% to 60% or a high partial load between 60% and 75% of its nominal load.A corresponding operational control for the PEM electrolyzer 7 is implemented in the control device 13, so that a control signal S2 is output for the second rectifier 9B for supplying direct current to the PEM electrolyzer 7. For capacity control, the control device 13 is equipped for power control such that forecast data for the input power P is available. E can be regularly consulted and read in, so that based on the forecast data for the first power consumption P2 and the second power consumption P2 a respective target value is determined and corresponding control signals S2, S2 for the rectifiers 9A, 9B of the electrolyzers 5, 7 and, if necessary, the rectifier 9 for the operation of the energy storage P s .

Claims

Patent claims 1. A method for power control of a hybrid electrolysis plant (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 with the alkaline electrolyzer (5), wherein an electrical input power (P E ) is fed into the supply line (3) and an electrical power consumption (P A ) is taken from the hybrid electrolysis plant ( 1 ) from the supply line (3), whereby a balance is maintained between the input power (P E ) and the power consumption (P A ) is monitored, and in case of an imbalance the power consumption (P A ) to the input power (P E), wherein a first power consumption (P2) of the alkaline electrolyzer (5) and / or a second power consumption (P2) of the PEM electrolyzer (7) is controlled, wherein a first temporal power change rate (Ri) is applied in the control of the alkaline electrolyzer (5) and a second temporal power change rate (R2) is applied in the PEM electrolyzer (7).

2. The method according to claim 1, wherein the first power take-off (P2) is taken off via a first rectifier (9A) and supplied as direct current power to the alkaline electrolyzer (5) and the second power take-off (P2) is taken off 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 (R2) of the second rectifier (9B) is set greater than the first power change rate (R2) of the first rectifier (9A).

4. Method according to claim 1, wherein the second power change rate (R2) is at least 20 times higher, preferably at least 40 times and especially 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. Method according to claim 7, in which energy stored in the energy storage device (11) is extracted 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 the highest possible first power consumption (Pi) 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 in such a way that forecast data for the input power (P E) are used regularly and a respective target value is specified based on the forecast data for the first power consumption (Pi) and the second power consumption (P2).

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 power control method 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 used 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, wherein the hybrid electrolysis plant (1) is connected to the renewable energy plant (15) via a supply line (3) designed as a central AG string, whereby an island network is formed.

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