Combination of electrolyzer and electrical energy storage device

Abstract

Optimization of the operation of an electrolyzer and an electric energy storage device. The total system includes, as subsystems, an electrolyzer (1) for producing hydrogen and an electric energy storage device (2). The electrolyzer (1) and the electric energy storage device (2) are directly or indirectly connected to a power grid (5) for the transmission of electric energy. Furthermore, the electrolyzer (1) and the electric energy storage device (2) are connected to each other for the transmission of electric energy. The electrolyzer (1) has a plurality of electrolysis blocks (10), and the electric energy storage device (2) has a plurality of battery modules (11). The battery modules (11) are connected to each of the electrolysis blocks (10) via respective converter circuits (12). The electrolysis blocks (10) or the battery modules (11) form a series connection connected to the power grid (5) via an inverter unit (4).

Description

[Technical Field]

[0001] The present invention is based on a total system. the total system includes as subsystems an electrolyzer for producing hydrogen and an electrical energy storage device; - the electrolysis device and the electrical energy storage device are directly or indirectly connected to the power grid for the transmission of electrical energy; The electrolyzer and the electrical energy storage device are connected to each other for the transmission of electrical energy. [Background technology]

[0002] From DE 10 2004 014 142 A1 an electrolyzer is known which is supplied by a wind park. Fluctuations in the electrical energy supply from the wind park are compensated for by adjusting the operation of the electrolyzer and / or by adjusting the operation of an alternative load and / or by adjusting the operation of an alternative energy source. The alternative load and the alternative energy source may be a battery. When operating the alternative load and the alternative energy source, a current control of the electrolysis module is taken into account.

[0003] From Non-Patent Document 1, a total system is known which includes as subsystems, in particular an electrolyzer for producing hydrogen and an energy storage device. The electrolyzer and the electrical energy storage device are directly or indirectly connected to each other and to the power grid for the transmission of electrical energy. The total system is controlled by a control device, which knows the current state of the subsystems.

[0004] Similar systems are known from other publications, such as Patent Document 2 and Patent Document 3.

[0005] Hydrogen is already being used today and will be used in many industrial sectors in the future, such as refineries, fertilizer plants, chemical plants, the steel and metals industry, etc. For example, the steel industry requires large amounts of hydrogen to produce pig iron from iron ore by direct reduction without emitting carbon dioxide.

[0006] Currently, there are three known large-scale methods of electrolysis that are technically applicable: alkaline electrolysis, PEM electrolysis, and high-temperature electrolysis.

[0007] In alkaline electrolysis, water is split into hydrogen and oxygen by passing an electric current through a potassium hydroxide solution. The process is carried out at a temperature of approximately 80°C. The method is relatively inexpensive. However, it is not easy to change the current rapidly. Furthermore, if the potassium hydroxide solution is cold, the resistance increases and the efficiency decreases. Furthermore, changes in current also affect the temperature of the potassium hydroxide solution. Therefore, in practice, the power output of alkaline electrolysis can only be adjusted in the range of approximately 50% to 100%. Furthermore, a stage for reheating the potassium hydroxide solution is required after shutdown.

[0008] In PEM electrolysis, the electrolyzer is made of a proton-permeable polymer membrane, coated with a porous electrode made of platinum on carbon on the cathode side and a noble metal (e.g., iridium) present as a metal or oxide on the anode side. Water is split on the anode side, producing oxygen and positively charged hydrogen ions. The latter migrate through the membrane to the cathode side, where they combine with electrons to form free hydrogen. This process is faster, more controllable, and more widely adjustable. However, it is somewhat more expensive.

[0009] High-temperature electrolysis operates at temperatures of several hundred degrees Celsius, for example, 500 to 600 degrees Celsius. Part of the required energy is provided in the form of heat, thereby reducing the demand for electricity. This method is particularly suitable when waste heat from other plants (e.g., steel mills) is available that would otherwise be unavailable. Electrical controllability is somewhat limited compared to PEM electrolysis because a ceramic, yttrium-stabilized zirconium oxide, is used as the separator. This ceramic should be kept as hot as possible. If cooled, a phase transition would occur, which could lead to cracks. Therefore, control is usually only possible within a range of 70% to 100%.

[0010] The electrolyzer requires direct current. The connection of the electrolyzer to the supply network, which is generally configured as a three-phase power network, is made via an inverter unit.

[0011] Battery banks have been known for a long time. They are used to temporarily store electrical energy. Such battery banks are charged when electrical energy is abundant and therefore cheap, and discharged when electrical energy is scarce and therefore expensive. Here too, an inverter unit is required to connect the battery bank to the power grid. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] U.S. Patent No. 8,288,888 [Patent Document 2] U.S. Patent No. 7,444,189 [Patent Document 3] US Patent Application Publication No. 2022 / 0302708 [Non-patent literature]

[0013] [Non-Patent Document 1] “Gruene Energieversorgung der Stahlindustrie”, Stahl und Eisen, (Germany), August 2022, p.22-24 Summary of the Invention [Problem to be solved by the invention]

[0014] The object of the present invention is to create the possibility of combining the operation of the electrolyzer and the operation of the battery bank in an easy way and making them adjustable to one another. [Means for solving the problem]

[0015] This problem is solved by a total system having the features of claim 1. Advantageous configurations of the total system are the subject of dependent claims 2 to 7.

[0016] According to the invention, a total system of the type mentioned at the beginning comprises: the electrolysis device comprises a plurality of electrolysis blocks; the electrical energy storage device comprises a plurality of battery modules; - the battery modules are connected to each electrolysis block via a converter circuit, respectively; and the electrolysis blocks or battery modules form a series connection and are connected to the grid via an inverter unit; It is composed of:

[0017] This configuration is easy to implement in terms of circuit technology and is very efficient. In particular, it is possible to integrate the electrolyzer into a battery bank, or vice versa, taking advantage of the fact that the operating voltages of the electrolysis cells and the battery cells are similar, i.e., in the low single-digit volt range.

[0018] Preferably, each electrolysis block is configured as a parallel connection of several electrolysis lines, each configured as a series connection of several electrolysis cells, thereby allowing the capacity and performance of the electrolysis block to be scaled as required.

[0019] Preferably, the electrolysis block (or alternatively the electrolysis lines if configured as a parallel connection of electrolysis lines) has a solid steel shell, which leaves only the electrical connections for current and sensors, and the inlets and outlets for the electrolyte and product gases accessible.

[0020] Preferably, each battery module comprises a plurality of battery blocks connected in series, and each battery block comprises a plurality of battery cells connected in parallel, thereby enabling the capacity and performance of the battery module to be scaled up or down as needed.

[0021] Preferably, each battery module includes a balancing circuit that balances the state of charge of the battery blocks of each battery module among the series-connected battery blocks of each battery module.

[0022] Such balancing circuits are known, see for example the German Wikipedia at https: / / de.wikipedia.org / wiki / Balancer and the English Wikipedia at https: / / en.wikipedia.org / wiki / Battery_balancing.

[0023] The battery blocks themselves do not require balancing circuitry, since the state of charge of the individual battery cells within each battery block is automatically equalized, and the electrolysis blocks do not require balancing circuitry, since it is immaterial whether certain electrolysis cells produce somewhat more hydrogen than others.

[0024] The converter circuit may be configured as a synchronous converter, a boost converter, or a buck converter, depending on the requirements. Synchronous converters have the advantage of allowing bidirectional energy exchange. Boost and buck converters allow energy flow in only one direction, but are cost-effectively implemented and easier to operate. Converter circuits such as those described above and their operation are well known to those skilled in the art. For example, relevant articles can be found in the German and English Wikipedia.

[0025] The above-mentioned characteristics, features and advantages of the present invention, as well as the manner in which they are achieved, will be more clearly and particularly understood in connection with the following detailed description of the preferred embodiments, taken in conjunction with the drawings, in which: [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a diagram showing a total system. [Figure 2] FIG. 1 shows an electrolysis device and an energy storage device. [Figure 3] FIG. 1 shows an electrolysis device and an energy storage device. [Figure 4] FIG. 1 shows an electrolysis block. [Figure 5] FIG. 2 is a diagram showing a battery module. [Figure 6] FIG. 2 is a diagram illustrating a converter circuit. [Figure 7] FIG. 1 illustrates an alternative converter circuit. [Figure 8] FIG. 10 shows a further alternative converter circuit. DETAILED DESCRIPTION OF THE INVENTION

[0027] According to Figure 1, the total system comprises as a subsystem an electrolyser 1. During operation, the electrolyser 1 produces hydrogen. The total system further comprises as a further subsystem an electrical energy storage device 2.

[0028] The total system can include further subsystems, such as a steel industry plant or generally electricity and / or hydrogen consuming facilities (not shown). In many cases, the total system also includes a hydrogen storage device 3 as another subsystem. The hydrogen storage device 3 may be configured as a storage device in the strict sense, i.e., a dedicated hydrogen storage device. However, a hydrogen transport pipeline network also has a certain storage capacity and can be used as the hydrogen storage device 3 in the present invention. In the case of a dedicated storage device, the hydrogen storage device 3 may alternatively be located above or below ground. The hydrogen storage device 3 is directly or indirectly connected to the electrolyzer 1 to receive hydrogen and directly or indirectly connected to a hydrogen consuming device to discharge hydrogen. This is shown in FIG. 1 by the upper connecting lines between the electrolyzer 1 and the hydrogen storage device 3. The hydrogen storage device 3 allows for more flexible configuration of the operation of the electrolyzer 1, especially in cooperation with hydrogen consuming devices.

[0029] The electrolyzer 1 and the electric energy storage device 2 are connected to each other for the transmission of electric energy and are further connected directly or indirectly to a power supply grid 5 via an inverter unit 4. The inverter unit 4 is preferably configured to be able to adjust the voltages applied to the electrolyzer 1 and the energy storage device 2.

[0030] The supply network 5 is typically a three-phase power supply network and therefore a polyphase supply network. Three-phase power supply networks often operate at medium voltages of 20 kV to 30 kV or at high voltages of 110 kV.

[0031] The total system further includes a controller 6. The controller 6 is programmed with a control program 7. The control program 7 includes machine code 8 that can be processed by the controller 6. Programmed by the control program 7, the controller 6 processes the machine code 8. Processing of the machine code 8 by the controller 6 causes the controller 6 to control the total system.

[0032] The electrolysis device 1 comprises a number of electrolysis cells (= the smallest possible unit) in a combination of electrical series and parallel connections. The production of hydrogen in each electrolysis cell is mainly proportional to the current flowing through it. The voltage dropped across each electrolysis cell is a function of the current. The voltage may additionally depend on the temperature of the electrolyte and the wear of the membranes of each electrolysis cell. The efficiency with which each electrolysis cell operates corresponds mainly to the voltage dropped across each electrolysis cell. The wear depends on the temperature and the current.

[0033] The energy storage device 2 comprises a number of battery cells (= the smallest possible units) in a combination of electrical series and parallel connections. The voltage of each battery cell depends on its state of charge and, due to its internal resistance, on the current passing through it. The state of charge of each battery cell is calculated by integrating the current from a known initial value. The internal resistance depends, for example, on the temperature and wear of each battery cell, and in some cases may also depend on the state of charge. The wear in turn depends on the current passing through each battery cell and on the state of charge of each battery cell. In some cases, it may also depend on other variables, such as existing wear or temperature.

[0034] In the following, two configurations of the two basic subsystems 1, 2, namely the electrolyzer 1 and the energy storage device 2, are described in relation to Figures 2 and 3. In the configurations shown in Figures 3 and 4, the electrolyzer 1 and the energy storage device 2 are integrated with each other as far as the electrical connections are concerned.

[0035] 2 and 3 includes a plurality of electrolytic blocks 10. Furthermore, the energy storage device 2 includes a plurality of battery modules 11. The battery modules 11 are connected to each of the electrolytic blocks 10 via respective converter circuits 12. The number of electrolytic blocks 10 can be determined as needed. For example, it can be 10, 15, 20, 50, or 100. Other numbers are also possible, such as less than 10, more than 100, or between 10 and 100. Generally, however, the number of electrolytic blocks 10 will be between 10 and 30. However, regardless of the number of electrolytic blocks 10, there will always be the same number of battery modules 11 and converter circuits 12, so that exactly the same number of groups, each consisting of one electrolytic block 10, one battery module 11, and one converter circuit 12, can be formed.

[0036] In the configuration shown in FIG. 2, the electrolytic blocks 10 form an (electrical) series connection, which is connected to the power grid 5 via the inverter units 4. That is, the series connection of the electrolytic blocks 10 is directly connected to the power grid 5 via the inverter units 4. In contrast, in the configuration shown in FIG. 2, the battery modules 11 are connected to the power grid 5 only via their respective converter circuits 12, and thus indirectly. Therefore, in the configuration shown in FIG. 2, the battery modules 11 are, so to speak, accessories to each electrolytic block 10. In the configuration shown in FIG. 3, the opposite is true: here, the battery modules 11 form an (electrical) series connection, which is connected to the power grid 5 via the inverter units 4. Therefore, in the configuration shown in FIG. 4, the electrolytic blocks 10 are, so to speak, accessories to each battery module 11.

[0037] According to FIG. 4, each electrolytic block 10 is configured as a parallel connection of several electrolytic lines 13. There may be only one electrolytic line 13 per electrolytic block 10. In this case, the parallel connection is degenerated. However, in many cases, each electrolytic block 10 has several electrolytic lines 13, and thus a true parallel connection exists. In general, the number of electrolytic lines 13 per electrolytic block 10 is the same for all electrolytic blocks 10. In general, the number of electrolytic lines 13 per electrolytic block 10 will be between 10 and 30.

[0038] Regardless of the number of electrolysis lines 13, each electrolysis line 13 is configured as a series connection of several electrolysis cells 14, according to FIG. 4. The electrolysis cells 14 of each electrolysis line 13 are arranged one after the other, electrically, mechanically and fluidically. Each electrolysis cell 14 is the smallest possible unit. Each electrolysis cell 14 is characterized in particular by its electrochemical operating voltage, which is usually in the low single-digit volt range, for example between 1.5 V and 2.0 V.

[0039] The number of electrolysis cells 14 per electrolysis line 13 can be determined as needed. The number of electrolysis cells 14 can be, for example, 50, 80, 100, 120, 150, or 200. Other numbers are also possible, such as less than 50, more than 200, or between 50 and 200. Within each electrolysis block 10, the number of electrolysis cells 14 per electrolysis line 13 is uniformly the same. From electrolysis block 10 to electrolysis block 10, this number can vary. However, in general, the number of electrolysis cells 14 per electrolysis line 13 will be between 50 and 250, and in particular between 100 and 200.

[0040] The product of the number of electrolysis blocks 10 and the number of electrolysis cells 14 per electrolysis line 13 is often in the range of 500 to 3000, in particular in the range of 1000 to 2000.

[0041] The interior of the electrolysis block 10 or electrolysis line 13 may not be easily accessible. For example, the electrolysis block 10 or electrolysis line 13 has a solid steel shell, so that only the electrical connections for the current and sensors and the inlets and outlets for the electrolyte and the product gas are accessible. Depending on the arrangement within the shell, the electrolysis can be carried out under pressure, saving energy for example for the subsequent compression of the hydrogen, which would otherwise be required for the storage of the hydrogen, for example in the hydrogen storage device 3.

[0042] Similarly, according to FIG. 5 , each battery module 11 includes a series connection of multiple battery blocks 15. The number of battery blocks 15 per battery module 11 may be determined as needed. The number of battery blocks 15 may be, for example, 50, 80, 100, 120, 150, or 200. Other numbers are possible, such as less than 50, more than 200, or between 50 and 200. The number of battery blocks 15 is often the same for all battery modules 11. However, this is not required. Rather, the number of battery blocks 15 may vary from battery module 11 to battery module 11. However, typically, the number of battery blocks 15 per battery module 11 will be between 50 and 250, and particularly between 100 and 200.

[0043] The battery blocks 15 have a parallel connection of multiple battery cells 16. The number of battery cells 16 per battery block 15 may be only one. In this case, the parallel connection is degenerated. However, in many cases, each battery block 15 has multiple battery cells 16, so that a true parallel connection exists. Generally, the number of battery cells 16 per battery block 15 is the same for all battery blocks 15. However, the number of battery cells 16 per battery block 15 is generally between 50 and 500, and particularly between 100 and 400.

[0044] Each battery cell 16 is the smallest possible unit and is characterized, inter alia, by its electrochemical operating voltage, which is also typically in the low single-digit volt range, e.g., between 1.2 V and 5.0 V, and particularly for lithium cells, between 3.2 V and 4.2 V.

[0045] Generally, each battery module 11 includes a balancing circuit 17. Each balancing circuit 17 balances the state of charge of the battery blocks 15 of each battery module 11 within the series-connected battery blocks 15 of each battery module 11. Balancing circuits 17 are known as such.

[0046] The converter circuits 12 may be configured as desired. For example, as shown in FIG. 6, the converter circuits 12 may be configured as synchronous converters. In this case, each converter circuit 12 includes two electronic switch elements 18 (MOSFETs according to the depiction in FIG. 6, but other semiconductor switches are possible) and an inductor 19. The capacitor 20 shown in FIG. 6 is often present, but is not required. Alternatively, the converter circuits 12 may be configured as boost or buck converters, as shown in FIGS. 7 and 8. In general, the converter circuits 12 are uniformly configured.

[0047] When the converter circuits 12 are configured as synchronous converters, the unit with the higher operating voltage is generally located at the input side of each converter circuit 12. This can be either each electrolysis block 10 or each battery module 11, depending on the structure of the electrolysis block 10 and the battery module 11. When the converter circuits 12 are configured as boost or buck converters, the direction of energy flow is fixed. In this case, each battery module 11 must always be located at the input side of each converter circuit 12. Configuring the converter device 12 as a boost or buck converter is possible, especially in the configuration shown in FIG. 3.

[0048] In the configuration shown in Figures 2 and 3, n+1 control variables are set for n groups (each consisting of one electrolysis block 10, one battery module 11, and one converter circuit 12). One of the control variables is the operating mode of the inverter unit 4. Its operation determines the total amount of energy supplied to the electrolyzer 1 and the energy storage device 2 (this value may temporarily become negative). The other n control variables are the operating mode of the converter circuit 12, in particular its pulse width ratio. The operating mode of the converter circuit 12 determines how much of the current emitted from the inverter unit 4 is distributed to each electrolysis block 10 and each battery module 11. This distribution may be uniformly the same for all n groups, but this is not required. In any case, the inverter unit 4 and the converter circuit 12 should be controlled so that a specific voltage is applied to the unit consisting of the electrolyzer 1 and the energy storage device 2 and the current of the battery module 11 has a specific value.

[0049] Fully controlled operation is possible, however preferably voltages and currents are sensed insofar as necessary and incorporated into corresponding control circuits for determining the operation of the inverter unit 4 and converter circuit 12.

[0050] The described interconnected structure of the electrolyzer 1 and the energy storage device 2 is advantageous because it is particularly modular. For example, if an individual electrolysis block 10 and / or an individual battery module 11 and / or an individual converter circuit 12 requires maintenance, repair, or replacement, the corresponding group can be bypassed via a switching device (not shown). Meanwhile, the other groups can continue to operate and can often be maintained unchanged or almost unchanged, although the operation of the inverter unit 4 and / or the remaining converter circuits 12 may need to be adjusted. In particular, the entire electrolyzer 1 and energy storage device 2 can continue to operate.

[0051] The present invention has many advantages, in particular, it is possible to comprehensively optimize the operation of the total system consisting of subsystems 1, 2, etc.

[0052] Although the present invention has been shown and described in detail by means of preferred embodiments, the present invention is not limited to the disclosed examples, and those skilled in the art can derive other variants without departing from the scope of protection of the present invention. [Explanation of symbols]

[0053] 1. Electrolyzer 2. Energy storage device 3 Hydrogen storage device 4 Inverter Unit 5 Supply network 6. Control device 7 Control Program 8 Machine Code 10 Electrolysis Block 11 Battery Module 12 Converter circuit 13 Electrolysis Line 14 Electrolysis Cell 15 Battery Block 16 battery cells 17 Balanced Circuit 18 Electronic Switching Elements 19 Inductors 20 Capacitor

Claims

1. A total system including, as subsystems, an electrolyzer (1) for producing hydrogen and an electrical energy storage device (2), - the electrolyzer (1) and the electrical energy storage device (2) are directly or indirectly connected to a power grid (5) for the transmission of electrical energy; - the electrolysis device (1) and the electrical energy storage device (2) are connected to each other for the transmission of electrical energy; - said electrolysis device (1) comprises a plurality of electrolysis blocks (10), - said electrical energy storage device (2) comprises a plurality of battery modules (11), - said battery modules (11) are connected to each of said electrolysis blocks (10) via respective converter circuits (12); - a total system in which the electrolysis blocks (10) or the battery modules (11) form a series connection connected to a supply network (5) via an inverter unit (4).

2. 2. The total system according to claim 1, characterized in that each of the electrolysis blocks (10) is configured as a parallel connection of a plurality of electrolysis lines (13), each of the electrolysis lines (13) being configured as a series connection of a plurality of electrolysis cells (14).

3. 3. A total system according to claim 2, characterized in that the electrolysis line (13) has a solid steel outer shell, whereby only electrical connections for current and sensors, as well as inlets and outlets for the electrolyte and the product gases, are accessible.

4. 3. A total system according to claim 1 or 2, characterized in that the electrolysis block (10) has a solid steel outer shell, by which only electrical connections for current and sensors, as well as inlets and outlets for the electrolyte and the produced gases, are accessible.

5. 5. The total system according to claim 1, wherein each of the battery modules (11) comprises a series connection of a plurality of battery blocks (15), and each of the battery blocks (15) comprises a parallel connection of a plurality of battery cells (16).

6. 6. The total system according to claim 5, wherein each of the battery modules (11) has a balancing circuit (17) that balances the charge states of the battery blocks (15) of each battery module (11) within the series-connected battery blocks (15) of each battery module (11).

7. 7. A total system according to any one of claims 1 to 6, characterized in that the converter circuit (12) is configured as a synchronous converter, a boost converter or a buck converter.

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