Method for operating an electrolyzer

Abstract

The invention relates to a method for operating an electrolyzer (200, 300, 400, 500) comprising at least one electrolysis cell (222), power electronics (212) configured to supply current to the at least one electrolysis cell (222), and a temperature control system configured to control the temperature of the at least one electrolysis cell (222) and the power electronics (212), wherein the method comprises: determining the current temperature of the at least one electrolysis cell (222), comparing the determined temperature with a predetermined minimum temperature, comparing the determined temperature with a predetermined target temperature, and operating the power electronics (212) to selectively generate waste heat when the determined temperature is lower than the minimum temperature or lower than the target temperature.wherein the waste heat from the power electronics (212) is transferred to the at least one electrolysis cell (222) via the temperature control system. Furthermore, a computing unit (240) and a computer program for carrying out such a process, as well as an electrolyzer (200, 300, 400, 500) with such a computing unit (240), are proposed.

Description

[0001] The present invention relates to a method for operating an electrolyzer as well as a computing unit and a computer program for carrying out the method and a corresponding electrolyzer. Background of the invention

[0002] Electrolysis systems require a certain operating temperature, which is above normal room temperature, to initiate the electrochemical splitting of water into hydrogen and oxygen. Typically, the lower the temperature, the more damage the electrolyzer will experience, as a higher voltage is required, leading to degradation of the electrolysis cells.

[0003] This damage can be consciously accepted, as the initial electrolysis process generates waste heat, which heats the electrolysis cell to operating temperature during use. Alternatively, the electrolyzer can be preheated. The heat for preheating can be generated either directly via the so-called stack (several electrolysis cells arranged in a stack) or via an additional heating unit. For example, a heating unit can be used to preheat feed water for the electrolyzer to a defined temperature and pump it through the electrolyzer, thereby also heating the electrolyzer itself. Disclosure of the invention

[0004] According to the invention, a method for operating an electrolyzer, as well as a computing unit, an electrolyzer, and a computer program for carrying out the method are proposed, having the features of the independent patent claims. Advantageous embodiments are the subject of the dependent claims and the following description.

[0005] The invention utilizes the measure of operating the power electronics required to operate an electrolyzer, instead of a dedicated heating unit, in such a way that they specifically generate waste heat, and of using this waste heat to preheat the electrolysis cell(s), particularly if they have a temperature lower than a minimum temperature. A minimum temperature is understood in particular to be a temperature below which damage to the electrolysis cell can be expected when it is energized for electrolysis. For example, the minimum temperature can be selected from a range between 15°C and 75°C, in particular from a range between 20°C and 50°C. For example, a minimum temperature of approximately 25°C can be specified.

[0006] In detail, the invention proposes a method for operating an electrolyzer which comprises at least one electrolysis cell, power electronics which are configured to supply current to the at least one electrolysis cell, and a temperature control system which is configured to temperature control the at least one electrolysis cell and to cool the power electronics, wherein the method comprises: determining a current temperature of the at least one electrolysis cell, comparing the determined temperature with a predeterminable minimum temperature, and operating the power electronics to specifically generate waste heat if the determined temperature is lower than the minimum temperature, wherein the waste heat of the power electronics is conducted to the at least one electrolysis cell by means of the temperature control system for heating the at least one electrolysis cell.By using power electronics to preheat at least one electrolysis cell, a dedicated heating device can be dispensed with, saving investment and operating costs and also having a positive impact on the overall efficiency of the system and the space required. In particular, a heating device would typically only be active for a relatively short operating period, since once the electrolysis cell is operating for electrolysis, enough waste heat is generated in the electrolysis cell at almost all operating points to keep the electrolysis cell above the minimum temperature.

[0007] In at least one embodiment, the method further comprises comparing the determined temperature with a predeterminable target temperature (e.g. nominal operating temperature 70°C), and operating the power electronics to specifically generate waste heat if the determined temperature is lower than the target temperature. This allows the at least one electrolysis cell to be used for electrolysis as quickly as possible (from reaching the minimum temperature) and, at the same time, to be heated up to its target temperature as quickly as possible, which is preferably selected such that the electrolysis efficiency is maximized, i.e. the electrolysis is carried out with optimal energy consumption. In some cases, the target temperature can also be identical to the minimum temperature, wherein in particular a target temperature (orMinimum temperature) can be selected, which can correspond to the minimum temperature explained above (to exclude damage to at least one electrolysis cell), the target temperature just explained (to maximize efficiency) or a temperature between these two extreme examples (compromise between high availability and high efficiency).

[0008] In particular, the temperature control system can also be configured to dissipate heat from the power electronics and / or the at least one electrolysis cell when the target temperature is reached or exceeded, in order to prevent damage to the components due to excessively high operating temperatures. Typically, a cooling system is already present, which can now also be used within the scope of this invention to preheat the at least one electrolysis cell by specifically discharging the waste heat generated by the power electronics to the electrolysis cell.

[0009] In at least one embodiment, the method comprises operating the power electronics in such a way that the at least one electrolysis cell is not supplied with current if the determined temperature is lower than the minimum temperature. This reliably prevents damage to the electrolysis cell due to overvoltage and / or overcurrent caused by excessively low temperatures.

[0010] In at least one embodiment, the method comprises operating the power electronics in such a way that the at least one electrolysis cell is supplied with current, and operating the temperature control system in such a way that waste heat is conducted from the power electronics to the at least one electrolysis cell when the determined temperature is higher than the minimum temperature and lower than the target temperature (if different temperatures were selected). This allows the electrolysis cell to continue heating even after the minimum temperature has been reached, while electrolysis has already started. This allows the desired operating temperature (target temperature) to be reached even faster, since the electrolysis cell itself also generates waste heat during operation.

[0011] In at least one embodiment, the method further comprises operating the temperature control system to dissipate heat from the power electronics and from the at least one electrolysis cell when the determined temperature is greater than the target temperature. As already mentioned, the temperature control system can thus be used throughout the entire operating period to set the most optimal temperature possible and thus for both preheating and cooling during normal operation. In other words, an existing cooling system is also used to preheat the electrolysis cell.

[0012] A computing unit according to the invention, e.g. a programmable logic controller (PLC), is configured, in particular in terms of programming, to carry out a method according to the invention.

[0013] The implementation of a method according to the invention, for example in the form of an optimized sequence control, in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, since this entails particularly low costs, in particular if an executive control is also used for further tasks and is therefore already present. Finally, a machine-readable storage medium is provided with a computer program stored thereon as described above. Suitable storage media or data carriers for providing the computer program are, in particular, magnetic, optical and electrical memories, such as hard disks, flash memories, EEPROMs, DVDs, etc. Downloading a program via computer networks (Internet, intranet, etc.) is also possible. Such a download can be wired or cable-based or wireless (e.g.via a Wi-Fi network, a 3G, 4G, 5G or 6G connection, etc.).

[0014] Furthermore, an electrolyzer with a computing unit according to the invention is proposed. These units benefit from the advantages explained above with regard to embodiments of the method according to the invention in a corresponding manner.

[0015] In at least one embodiment, the temperature control system of the electrolyzer is configured to supply heat from the power electronics to the at least one electrolysis cell in a heating mode and to remove heat from the at least one electrolysis cell in a normal mode. Thus, a single temperature control system can be used both for heating the electrolysis cell(s) and for cooling them. In particular, this eliminates the need for a separate heating device.

[0016] In particular, the temperature control system can have at least one heat exchanger designed to thermally couple the power electronics to the at least one electrolysis cell. This allows separate temperature control medium circuits to be used for the power electronics on the one hand and the electrolysis cell on the other, which can be advantageous, for example, if different temperature control media are to be used in order to account for the different operating conditions (e.g. different maximum temperatures) of the two components. Alternatively, the temperature control system can also be designed to supply a temperature control medium heated directly by the power electronics to the at least one electrolysis cell without heat exchange. This allows heat to be introduced into the electrolysis cell(s) particularly efficiently in heating mode, so that they can be heated to the minimum or target temperature more quickly.In at least one such embodiment, the fluid subjected to electrolysis can itself be used as the temperature control medium, i.e. the fluid to be electrolyzed can be heated before it is fed to the at least one electrolysis cell. This is typically pure water. However, it is very important to pay attention to the material properties of the cooling circuit, since the electrolysis cell can typically only process very pure water with low conductivity. If components are installed in the temperature control system that do not tolerate this water or dissolve in this water, this option is not possible. This option can be used for power electronics, where these important material properties are taken into account in the cooling system. In this case, however, additives such as glycol cannot be used in the temperature control medium.

[0017] Alternatively or additionally, the temperature control system may comprise at least one heat exchanger configured to dissipate heat from the at least one electrolysis cell and from the power electronics. The use of one or more heat exchangers for heat dissipation offers the advantage that a refrigerant circuit can be used as a heat sink, allowing for particularly good control of the thermal output.

[0018] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0019] The invention is illustrated schematically in the drawing using exemplary embodiments and is described below with reference to the drawing. Short description of the drawings Fig. 1 shows a non-inventive arrangement with an electrolysis cell unit, a power electronics and a cooling device for the electrolysis cell unit and the power electronics Fig. 2 shows a first embodiment of an electrolyzer according to the invention as a block diagram. Fig. 3 shows a second embodiment of an electrolyzer according to the invention as a block diagram. Fig. 4 shows a third embodiment of an electrolyzer according to the invention as a block diagram. Fig. 5 shows a fourth embodiment of an electrolyzer according to the invention as a block diagram. Embodiment(s) of the invention

[0020] In Fig. 1, a non-inventive embodiment of an electrolyzer is shown schematically and designated overall by 100. The electrolyzer 100 comprises an electrolysis cell unit 120 with at least one electrolysis cell 122, as well as a first heat exchanger 126 and a first cooling unit 124, which are configured to cool the at least one electrolysis cell 122. Furthermore, the electrolyzer 100 comprises a power electronics unit 110 with power electronics 112, which is configured to supply current to the at least one electrolysis cell 122, as well as a second heat exchanger 116 and a second cooling unit 114, which are configured to cool the power electronics. In the non-inventive embodiment of the electrolyzer 100, as shown in Fig. 1, two separate cooling circuits are provided for cooling the power electronics 112 and the at least one electrolysis cell 122.

[0021] In contrast, in the inventive designs of the electrolyzer, as described in the Fig. 2 to 5, temperature control systems (which can also be operated, among other things, as cooling circuits) are provided in each case, in which heat exchange between the power electronics 212 and at least one electrolysis cell 222 is possible. Components with the same function are provided with identical reference numerals in all figures illustrating embodiments of an electrolyzer according to the invention, which are each explained in more detail in connection with the figure in which they are first illustrated.

[0022] There are in the Fig. 2 to 5 each show two operating modes for each of the embodiments shown: View "A" for a heating mode in which heat from the power electronics 212 is used to heat the at least one electrolysis cell 222, and View "B" for a normal operating mode in which heat is dissipated from the at least one electrolysis cell 222 (and also from the power electronics 212). Solid lines indicate lines through which temperature control medium flows in the respective operating mode, while dashed lines represent lines that are inactive in the respective operating mode, i.e., no temperature control medium flows through them. The dash-dot lines represent signal lines for controlling the respective components, wherein the signal line can be wired or partially or completely wireless.

[0023] In Fig. 2, a first embodiment of an electrolyzer according to the invention is schematically shown and designated overall by 200. The electrolyzer 200 comprises power electronics 212 for supplying current to an electrolysis cell stack with at least one electrolysis cell 222. The electrolyzer 200 is constructed relatively similarly to the non-inventive electrolyzer 100 with regard to its temperature control system. It also comprises dedicated heat exchangers 216, 226 and cooling units 214, 224, which are designed to dissipate waste heat from the power electronics 212 or the at least one electrolysis cell 222, as described in Part B of the Fig. 2 shown.

[0024] In contrast to the electrolyzer 100 of the Fig. 1, the electrolyzer 200 also comprises a further heat exchanger 236, which is designed to be flowed through by both the temperature control medium of the power electronics 212 and the temperature control medium of the at least one electrolysis cell 222, as shown in part A of the Fig. 2. Thus, heat can be exchanged between the power electronics 212 and the at least one electrolysis cell 222. In embodiments of a method according to the invention for operating the electrolyzer 200, this is used to heat the at least one electrolysis cell 222, provided its temperature falls below a predeterminable minimum temperature (e.g., temperature below which energization of the at least one electrolysis cell 222 could lead to degradation due to overvoltage) and / or a predeterminable target temperature (e.g., optimal operating temperature; nominal operating temperature). The minimum and target temperatures can also be identical, for example, to ensure that the at least one electrolysis cell 222 can be operated with maximum efficiency and / or to maximize its service life.In order to heat the at least one electrolysis cell 222, the power electronics 212 is controlled in such a way that it has a high power loss, but does not supply current to the at least one electrolysis cell 222. In this operating mode, the temperature control medium of the power electronics 212 is not passed through the heat exchanger 216, which is designed to dissipate heat from the power electronics by means of the cooling unit 214, but rather to the heat exchanger 236, which transfers the heat at least partially to the temperature control medium of the at least one electrolysis cell 222. For this purpose, control valves 218 in the temperature control circuit on the side of the power electronics 212 and control valves 228 in the temperature control circuit on the side of the at least one electrolysis cell 222 are switched in such a way that the respective temperature control media flow through the common heat exchanger 236, in particular in counterflow to one another, and then to the power electronics 212 orthe at least one electrolysis cell 222 without flowing through the respective heat exchanger 216, 226, which is each configured to transfer heat to the respective cooling unit 214, 224. Thus, a large portion of the deliberately generated waste heat of the power electronics 212 can be used to heat or preheat the at least one electrolysis cell 222, as described in Part A of the . Fig. 1 shown.

[0025] Once the minimum temperature is reached, the power electronics 212 can be controlled to supply current to the at least one electrolysis cell 222 to start the electrolysis. However, the temperature control system can initially continue to operate as described above to further heat the at least one electrolysis cell 222, i.e., transfer heat from the power electronics 212 to the at least one electrolysis cell 222 via the common heat exchanger 236 if the cell has not (yet) reached its target temperature.

[0026] If, however, the target temperature of the at least one electrolysis cell is reached or exceeded (or in cases where the minimum and target temperatures are identical), the control valves 218, 228 can be controlled in such a way that the respective temperature control media of the power electronics 212 and the at least one electrolysis cell 222 are redirected to the corresponding heat exchangers 216 and 226 of their respective cooling circuits, so that no more heat transfer takes place from the power electronics 212 to the at least one electrolysis cell 222 (situation according to Part B of the Fig. 2). This mode of operation then corresponds to the conventional procedure, as it is also used in the non-inventive arrangement according to Fig. 1 can be carried out. The cooling units 214, 224 can each be controlled in their performance according to the respective cooling requirements of the power electronics 212 or the at least one electrolysis cell 222.

[0027] The temperature of the at least one electrolysis cell 222 can be determined, in particular, sensor-based and / or model-based. In the example shown, the control of the units 214, 224, the control valves 218, 228, and the power electronics 212 is carried out by a computing unit 240, which is also configured, in particular, to determine the relevant temperatures (e.g., the current temperature of the at least one electrolysis cell 222) and to compare them with the minimum and / or target temperature. Depending on the result of the comparison, the computing unit 240 can modify the control of valves 218, 228, (temperature control medium) pumps (not shown separately in the drawing), units 214, 224, and / or power electronics 212.

[0028] In principle analogous to the electrolyzer 200 just described, the Fig. 3, which is designated overall by 300, also has a heat exchanger 236, which is designed to transfer heat from the power electronics 212 to the at least one electrolysis cell 222. The operation of the electrolyzer 300 for heating the at least one electrolysis cell 222 in a case in which it falls below its minimum temperature and / or target temperature is essentially identical to that just described with reference to Fig. 2 in the case of the electrolyzer 200. This operating situation is again described in Part A of the Fig. 3 shown.

[0029] However, the electrolyzer 300, which is in Fig. 3, only a single cooling unit 234, which is designed to dissipate heat from both the power electronics 212 and the at least one electrolysis cell 222. Accordingly, if the temperature of the at least one electrolysis cell 222 exceeds the predeterminable target temperature, the control valves 218 on the power electronics 212 side and the valves 228 on the at least one electrolysis cell 222 side are controlled such that two separate cooling circuits are formed, wherein the common heat exchanger 236 functions as a heat exchanger for the temperature control medium of the power electronics 212 and a further heat exchanger 226 is operated as a cooler for the temperature control medium of the at least one electrolysis cell 222. The cooling medium for both heat exchangers 226, 236 is provided by means of the common cooling unit 234 (also controlled by the computing unit 240) (see Part B of the Fig. 3).

[0030] A third embodiment of an electrolyzer according to the invention is shown in Fig. 4 and is designated as 400 in total. The electrolyzer 400 differs from electrolyzer 300 in particular in that the two heat exchangers 226, 236 are now combined into a single common heat exchanger 236, which is designed, on the one hand, to transfer heat from the power electronics 212 to the at least one electrolysis cell 222 (see part A of the Fig. 4), and on the other hand, is configured to dissipate heat from the power electronics 212 via the common cooling unit 234. In this embodiment of the electrolyzer 400, the temperature control medium of the at least one electrolysis cell 222 is simultaneously also the cooling fluid of the cooling unit 234.

[0031] Which path the tempering medium (cooling fluid) takes, i.e. whether heat is transferred from the power electronics 212 to the at least one electrolysis cell 222 (part A of Fig. 4) or is discharged by means of the cooling unit 234 (part B of Fig. 4), is set by means of the common control valves 238, which can also be controlled by the computing unit 240. Their setting determines whether the cooling unit 234 is integrated into the temperature control system or isolated from it. Compared to the other embodiments explained here, the one described in Fig. The third embodiment of the electrolyzer 400 shown in Figure 4 has the fewest components and is therefore the most cost-effective variant from an investment cost perspective. However, variants with more heat exchangers have the advantage of a less interdependent temperature control of the two heat-generating components, power electronics 212 and electrolysis cell(s) 222.

[0032] In Fig. Finally, Figure 5 shows a fourth variant of an electrolyzer according to the invention, designated overall by 500. The electrolyzer 500 differs from the third embodiment of the electrolyzer 400 in particular in that the temperature control medium of the power electronics 212 is simultaneously the temperature control medium of the at least one electrolysis cell 222, while the cooling medium of the cooling unit 234 is conducted in a separate line system. In other words, no heat exchanger is provided between the power electronics 212 and the electrolysis cell(s), so that heat from the power electronics 212 can be transferred directly to the electrolysis cell(s) 222 without intermediate conversion, which contributes to an even faster warm-up of the electrolysis cell(s) and thus to a faster start-up of the at least one electrolysis cell 222.In this case, the heat exchanger 226 is designed to dissipate excess heat from the two components power electronics 212 and electrolysis cell(s) 222 and is therefore used during the warm-up operation (part A of . Fig. 5) is not flowed through by the temperature control medium of the line electronics 212 or electrolysis cell(s) 222.

[0033] In normal operation of the electrolyzer 500 (see part B of the Fig. 5), however, the control valves 218 (on the side of the power electronics 212) and 228 (on the side of the at least one electrolysis cell 222) are controlled such that the temperature control medium flows in the required amount to the power electronics 212 and the electrolysis cell(s) 222 in order to control them (in particular to cool them) to their respective target temperatures. As shown in the figure, the temperature control medium flows can be combined on the warm side of the heat exchanger 226 and divided again on the cold side. It can also be advantageous to provide separate passages through the heat exchanger 226 so that during normal operation (part B of Fig. 5) of the electrolyzer 500, separate cooling circuits are formed for power electronics 212 and electrolysis cell(s) in order to achieve better controllability.

Claims

[1] Method for operating an electrolyzer (200, 300, 400, 500) comprising at least one electrolysis cell (222), power electronics (212) configured to supply current to the at least one electrolysis cell (222), and a temperature control system configured to control the temperature of the at least one electrolysis cell (222) and the power electronics (212), the method comprising: Determining a current temperature of the at least one electrolysis cell (222), Comparing the determined temperature with a predeterminable minimum temperature, and Operating the power electronics (212) for the targeted generation of waste heat when the determined temperature is lower than the minimum temperature, wherein the waste heat of the power electronics (212) is conducted to the at least one electrolysis cell (222) by means of the temperature control system for heating the at least one electrolysis cell (222). [2] Method according to claim 1, comprising operating the power electronics (212) such that the at least one electrolysis cell (222) is not energized when the determined temperature is lower than the minimum temperature. [3] Method according to claim 1 or 2, comprising comparing the determined temperature with a predeterminable target temperature, and operating the power electronics (212) to selectively generate waste heat when the determined temperature is lower than the target temperature. [4] Method according to claim 3, comprising operating the power electronics (212) such that the at least one electrolysis cell (222) is energized, and the temperature control system such that waste heat is conducted from the power electronics (212) to the at least one electrolysis cell (222) when the determined temperature is higher than the minimum temperature and lower than the target temperature. [5] Method according to claim 3 or 4, comprising operating the temperature control system to dissipate heat from the power electronics (212) and from the at least one electrolysis cell (222) when the determined temperature is greater than the target temperature. [6] Computing unit (240) which is configured to carry out all method steps of a method according to one of the preceding claims. [7] Electrolyzer (200, 300, 400, 500) with at least one electrolysis cell (222), power electronics (212) which are designed to supply current to the at least one electrolysis cell (222), a temperature control system which is designed to control the temperature of the at least one electrolysis cell (222) and the power electronics (212), and a computing unit (240) according to claim 6. [8] Electrolyzer (200, 300, 400, 500) according to claim 7, wherein the temperature control system is configured to supply heat from the power electronics (212) to the at least one electrolysis cell (222) in a heating operating mode (A) and to remove heat from the at least one electrolysis cell (222) in a normal operating mode (B). [9] Electrolyzer (200, 300, 400) according to claim 8, wherein the temperature control system comprises at least one heat exchanger (236) which is configured to thermally couple the power electronics (212) to the at least one electrolysis cell (222). [10] Electrolyzer (500) according to claim 8, wherein the temperature control system is configured to supply a temperature control medium heated directly by the power electronics (212) to the at least one electrolysis cell (222) without heat exchange. [11] Electrolyzer (200, 300, 500) according to one of claims 7 to 10, wherein the temperature control system comprises at least one heat exchanger (216, 226, 236) which is designed to dissipate heat from the at least one electrolysis cell (222) and from the power electronics (212). [12] Computer program which causes a computing unit (240) to carry out all method steps of a method according to one of claims 1 to 5 when it is executed on the computing unit (240). [13] A machine-readable storage medium having stored thereon a computer program according to claim 12.

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