Method of operating an electrolyzer system
Combining different electrolyzers with waste heat utilization increases the overall efficiency of hydrogen and oxygen production by preheating or evaporating water for the second electrolyzer, reducing electrical energy requirements.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- GIMPEL INGENIEUR- GMBH
- Filing Date
- 2025-11-24
- Publication Date
- 2026-06-04
Smart Images
Figure EP2025083969_04062026_PF_FP_ABST
Abstract
Description
[0001] Kassel, November 19, 2025
[0002] Lawyer's file GIM24089P1WO
[0003] Official file number
[0004] NN
[0005] Applicant:
[0006] Gimpel Engineering Company Ltd.
[0007] Moltkeplatz 1
[0008] 45138 Essen
[0009] Representative:
[0010] WALTHER PATENT
[0011] Walther ■ Bayer ■ Faber
[0012] Heimradstraße 2
[0013] 34130 Kassel, Germany
[0014] METHOD FOR OPERATING A
[0015] ELECTROLYSIS SYSTEM
[0016] The invention relates to a method for operating an electrolyzer system with which water is converted into oxygen and hydrogen, wherein heat is generated during the hydrogen production process, and wherein at least a second electrolyzer of a different design is provided, to which at least some of the heat from the first electrolyzer is supplied at least indirectly for operation, and wherein at least a first heat pump is provided, to which at least some of the heat from the first electrolyzer is supplied, and wherein heat is provided by means of the first heat pump, which is then transferred to the second electrolyzer. Prior Art
[0017] For example, DE 10 2019 202 439 A1 discloses a method for operating an electrolyzer system in which supplied water is split into hydrogen and oxygen by applying an electric current. The system also includes a heat pump to which waste heat generated in the process from an electrolyzer of the electrolyzer system is supplied in order to provide a heat transfer fluid with a higher temperature. The heat pump is intended to be powered by electricity from renewable energy sources.
[0018] The simple use of a heat pump to raise the energy level of the waste heat from an electrolyzer is thus well-known. Typically, heat transfer fluids are heated, for example, water in the simplest case, so that the waste heat from the electrolyzer is raised to a higher energy level, specifically to a higher temperature and / or pressure. The heat transfer fluid with the higher energy level is then fed into the district heating network. The cited document only refers to heat demand, which can also be the heat demand of the energy system itself. This system is intended to include several renewable energy sources, such as photovoltaic systems and / or wind turbines. Electricity is generated using such energy sources and can also be stored via battery storage or thermomechanical energy storage systems.The energy system comprises an electrolyzer for hydrogen electrolysis, and the hydrogen itself can also be stored. The result is an energy system that can provide energy when the sun is shining and the wind is blowing, and additionally offers a storage option via a hydrogen intermediate storage unit. This allows energy to be provided even without sun or wind by reconverting the hydrogen into electricity and using a heat pump. The proposed system does not increase the efficiency of the electrolyzer disclosed therein.
[0019] The subsequently published WO 2024 / 263522 A1 already proposes a transfer of heat from a first electrolyzer to a second electrolyzer, specifying a heating device, and the heating device can also be a heat pump.
[0020] WO2023 / 158433 A1 does not disclose a heat pump in the heat flow from a first to a second electrolyzer.
[0021] CN 1 16 676 611 A does not disclose a heat cascade between a heat pump and another heating device for heating the water supplied to the second electrolyzer.
[0022] REVELATION OF THE INVENTION
[0023] The object of the present invention is rather to propose a method for operating an electrolyzer system which initially serves to split water into oxygen and hydrogen, wherein the electrolyzer system is to have an increased overall efficiency.
[0024] This problem is solved starting from a method for operating an electrolyzer system according to the preamble of claim 1. Advantageous embodiments of the invention are specified in the dependent claims. The solution to the problem also consists of an electrolyzer system according to claim 13. The invention includes the technical teaching that the heat from the first heat pump is supplied via a fluid line to a heat exchanger directly to the second electrolyzer for heating purposes, by evaporating water in liquid form in the heat exchanger so that it is supplied to the second electrolyzer as water vapor, and wherein a heating device is provided with which the water in the form of water vapor is further heated after the heat exchanger.
[0025] The core of the invention is the combination of at least two electrolyzers of different designs into an electrolyzer system, so that different operating parameters can be used to utilize the heat of a first electrolyzer to heat the second electrolyzer, to preheat the water to be introduced into the second electrolyzer, or even to evaporate it. The efficiency of each individual electrolyzer does not increase in this respect; however, the combination of at least two electrolyzers of different designs into an electrolyzer system according to the invention can achieve a higher overall efficiency than the efficiencies of the respective individual electrolyzers.
[0026] The operation of the first electrolyzer, which splits water into its components oxygen and hydrogen by supplying an electric current, generates process heat or waste heat during the electrolysis process. According to the invention, this waste heat is to be supplied to the second electrolyzer either completely or at least partially, depending on requirements, either directly or indirectly, i.e., directly or indirectly, in the latter case via further means, for example, a heat pump. For example, a portion of the waste heat from the first electrolyzer can be supplied to a district heating network, and, if required, the proportion of heat allocated to the second electrolyzer can be distributed to it depending on the operating state of the second electrolyzer.In the case of an indirect allocation of heat from the first electrolyzer to the second electrolyzer, for example, another means can be interposed, for example to increase the temperature of the same or another heat transfer fluid, through which the heat is transferred from the first to the second electrolyzer.
[0027] For example, the first electrolyzer is a proton exchange membrane electrolyzer, also known simply as a PEM electrolyzer (from the English: Proton Exchange Membrane). The second electrolyzer can be a high-temperature electrolyzer, also known simply as an HT electrolyzer. The waste heat from operating a PEM electrolyzer is, for example, 50°C to 60°C.
[0028] However, within the scope of the invention, it is also conceivable that the first electrolyzer is formed using a high-temperature electrolyzer and / or that the second electrolyzer is formed using a proton exchange membrane electrolyzer. With such a setup, the waste heat from the first electrolyzer can also be used to heat the second electrolyzer.
[0029] High-temperature (HT) electrolyzers are known in various designs. These are operated, for example, at temperatures starting from 100°C, and there are also HT electrolyzers that can reach operating temperatures of up to 900°C. In these cases, water at a correspondingly high temperature is supplied to an HT electrolyzer, usually under pressure at temperatures well above 100°C, i.e., in a vapor state. In contrast, permeable membrane electrolyzers (PEM electrolyzers) are supplied with water at room temperature (20°C). For example, high-temperature electrolyzers are known, such as those based on the electrolyte ZrÜ2, which generate their own process heat but also require preheating or are supplied with steam.
[0030] High-temperature electrolyzers are more economical than conventional PEM water electrolysis at room temperature because some of the energy can be supplied in the form of heat, which is more readily available and / or less expensive than low-entropy electrical energy, and the electrolysis reaction can proceed more efficiently at higher temperatures. Thus, water vapor already at high temperature and high pressure can be efficiently supplied to a high-temperature electrolyzer, wherein, according to the invention, the high-energy state of the supplied water vapor is to originate at least partially from the electrolyzer of the first type, i.e., preferably a PEM electrolyzer.
[0031] The waste heat from the first electrolyzer can be used, at least partially and preferably completely, to heat the second electrolyzer. This heating primarily concerns the heating of the water supplied to the second electrolyzer, but it can also heat the high-temperature electrolyzer itself. High-temperature electrolyzers are based on the principle that heat is absorbed from the environment or supplied to the electrolyzer, so that the energy content of the hydrogen produced is ultimately higher than the electrical energy input. Therefore, if heat from the first, PEM electrolyzer is supplied to the second electrolyzer (high-temperature electrolyzer), the amount of electrical energy required to operate the high-temperature electrolyzer can be reduced, thus increasing the overall efficiency of the electrolyzer system.It is preferably provided that the water supplied to the second electrolyzer is heated and, in particular, evaporated to reach the aforementioned temperatures of up to 900°C. Depending on the means employed to further increase the heat from the first electrolyzer, it is possible to achieve the temperatures required for operating the second electrolyzer without having to supply large amounts of electrical energy to the second electrolyzer outside the electrolysis system, for example, with at least one heat pump and / or a heating device that can be heated with fuel. In other words, the energy required to operate the second electrolyzer at very high temperatures is provided at least partially, and in particular predominantly, by at least one first electrolyzer.Depending on the size and operating mode of the electrolyzers, several PEM electrolyzers can be assigned to a single high-temperature electrolyzer to generate the necessary amount of heat, allowing the subsequent high-temperature electrolyzer to operate without significant electrical energy input. Consequently, the electrolyzer system may also include several secondary electrolyzers, particularly multiple high-temperature electrolyzers.
[0032] According to a further significant advantage of the method according to the invention, at least one first heat pump is installed, to which at least a portion of the heat from the first electrolyzer is supplied, so that heat is provided by means of the first heat pump and transferred to the second electrolyzer. In particular, a heat transfer fluid can enable the exchange of heat from the first electrolyzer to the second electrolyzer, so that the heat pump is interposed in this energy flow, and the waste heat from the first electrolyzer forms the heat source for the evaporator side of the heat pump, with the condenser side of the heat pump forming the heat source for the second electrolyzer.
[0033] A further advantage is that the second electrolyzer can also generate waste heat during operation, and at least some of this waste heat can be fed to the first heat pump. It is also conceivable that some of the waste heat generated by the second electrolyzer could be fed into a district heating network, while some of the heat from the second electrolyzer could be fed back into the first heat pump.
[0034] Additionally, at least one second heat pump can be installed, to which at least a portion of the heat from the second electrolyzer is supplied. This second heat pump can provide heat that, in turn, can serve as input heat for the operation of the second electrolyzer. Thus, it is ultimately possible and / or conceivable to establish a district heating network, in which the heat from the first heat pump and / or the heat from the second electrolyzer and / or the heat from the second heat pump is supplied to the district heating network. Portions of the heat flows can be diverted in such a way that the second electrolyzer can also be operated at an optimal operating point, so that only a minimal amount of electrical energy needs to be supplied to the second electrolyzer.Therefore, optimization can also take place against the backdrop of a significantly smaller amount of electrical energy required to operate the first and / or second heat pump.
[0035] To achieve the high operating temperatures of the second electrolyzer, which is a high-temperature electrolyzer, for example up to 900°C, the first heat pump can also form a cascade of several individual heat pumps operating in series to achieve a correspondingly higher temperature difference. Depending on the working fluids of the heat pumps in the cascade of several individual heat pumps operating in series, significantly higher output temperatures can be achieved.If the operating temperatures for operating the high-temperature electrolyzer cannot be reached using heat pumps, at least one heat pump or several individual heat pumps operating in a cascade can significantly contribute to the operation of the second electrolyzer and also to the heating of the second electrolyzer or the input steam using a heating device, so that only a small portion needs to be heated electrically.
[0036] The first heat pump can be located upstream of the heating device, so that at least some of the heat from the first electrolyzer is supplied to the first heat pump, and heat is transferred by means of the first heat pump to the water supplied to the second electrolyzer, in particular to evaporate the water. The heating device is specifically designed to heat the water supplied to the second electrolyzer, and is located downstream of the first heat pump, so that the heating device further heats the water evaporated by the first heat pump. Thus, according to the invention, a heat supply cascade is provided for evaporating and further heating the water supplied to the second electrolyzer, beyond its evaporation, to operating temperatures of a high-temperature electrolyzer, for example, to temperatures up to or above 900°C.
[0037] The waste heat from the first electrolyzer can be utilized via a heat transfer fluid at a temperature of 45°C to 70°C, and preferably 50°C to 65°C. The heat from the first heat pump can be supplied to the second electrolyzer via a heat transfer fluid at a temperature of over 100°C up to 900°C. If a single first heat pump or a cascade of several individual heat pumps cannot provide such temperatures, further heating with other energy sources can be carried out to bring the feedwater steam for operating the second electrolyzer to operating temperatures of several hundred degrees Celsius, for example, up to 850°C or up to 900°C.
[0038] The invention further relates to an electrolyzer system for converting water into oxygen and hydrogen, wherein at least one first electrolyzer of the first type and at least one second electrolyzer of a second type differing from the first type are provided, wherein a first fluid line is provided from the first electrolyzer to the second electrolyzer, via which at least a portion of the heat from the first electrolyzer can be transferred at least indirectly to the second electrolyzer by means of a heat transfer fluid, wherein at least one first heat pump is provided such that at least a portion of the heat from the first electrolyzer can be supplied to it, and wherein the first heat pump is provided to transfer heat to the second electrolyzer, wherein a heat exchanger is provided to supply higher temperature heat from the first heat pump directly to the second electrolyzer via a fluid line for heating purposes.by evaporating water in liquid form in the heat exchanger so that it is supplied as water vapor to the second electrolyzer, and wherein a heating device is provided with which the supplied water is further heated after the heat exchanger.
[0039] The first heat pump can absorb heat from the heat transfer fluid of the first electrolyzer via an evaporator side and transfer heat via a condenser to another heat transfer fluid at a significantly higher temperature in order to heat the second electrolyzer or to supply it with heat, in particular to heat or evaporate water introduced into the second electrolyzer.
[0040] In particular, at least one second heat pump can be provided, to which heat from the second electrolyzer can be supplied via a second fluid line and / or a third fluid line can be provided, via which heat from the second heat pump can be supplied to the first heat pump and / or the second electrolyzer by means of a heat transfer medium.
[0041] PREFERRED EXAMPLE OF THE INVENTION
[0042] Further measures improving the invention are described in more detail below, together with a description of a preferred embodiment of the invention, with reference to the figures. The figures show:
[0043] Figure 1 shows a schematic view of the electrolysis system for carrying out the method according to the invention.
[0044] Figure 2 shows the view of the electrolysis system according to Figure 1 with an additional internal use of the waste heat from the second electrolyzer, and
[0045] Figure 3 shows the electrolysis system according to Figure 2 with several first heat pumps.
[0046] Figures 1, 2, and 3 share a schematic view of an electrolyzer system 1 with a first electrolyzer 10 and a second electrolyzer 11. Heat W1 is transferred from the first electrolyzer 10 to the second electrolyzer 11 via a heat transfer fluid through a first fluid line 16, which is generally represented graphically. Hydrogen 100 can be produced by both the first electrolyzer 10 and the second electrolyzer 11, with the simultaneous production of oxygen, which is not shown in detail.
[0047] Water 12 is supplied to both the first electrolyzer 10 and the second electrolyzer 11, wherein the water 12 can be supplied to the first electrolyzer 10 in liquid form and to the second electrolyzer 11 in liquid form or preferably in gaseous form.
[0048] The first electrolyzer 10 is designed as a PEM electrolyzer, shown in single unit form. Several first electrolyzers 10 of the PEM type can be operated in parallel and form part of the electrolyzer system 1. The second electrolyzer 11 is a high-temperature electrolyzer and is fed with steam. The water 12 shown can be introduced in liquid form, and the liquid water 12 can be evaporated in the heat exchanger 19 so that it is supplied as steam to the second electrolyzer 11.
[0049] It is conceivable that the waste heat from the first electrolyzer 10 is insufficient to reach the operating temperature of the second electrolyzer 11 or the temperature of the water 12. Therefore, a heating device 21, such as a combustion device or an electric heating device, may be provided to further heat the second electrolyzer 11 and / or the water 12, regardless of its state of matter. The heating device 21 can thus supply heat Qpoint. In the same way as shown in Figures 1, 2, and 3, the heating device 21 can also be installed in the first fluid line 16d, 16e, which leads directly into the second electrolyzer 11 (which is not shown).
[0050] The heat pumps 13 and 14 shown each have an evaporator and a condenser; furthermore, the heat pumps have a compressor and an expansion valve, the basic operating principle of a heat pump 13, 14 is known and is not explained in more detail here.If heat is supplied to the heat pumps 13, 14, for example, the heat W1 of the first electrolyzer 10 in Figure 1, and the heat W3 of the second electrolyzer 11 of the first heat pump 13 and the heat W3 of the second electrolyzer 11 of the second heat pump 14 in Figure 2, the heat supplied to the heat pumps 13, 14 serves to evaporate the working fluid in the evaporator, wherein the heat released by the heat pump, for example, in Figures 1 and 2, the heat W2 of the first heat pump 13 and the heat W4 of the second heat pump 14, and in Figure 3, the heat W2 from the individual heat pumps 13a, 13b, 13c and the heat W4 from the second heat pump 14, is released by the heat pumps 13, 14 via the condenser. The heats W2 and W4 emitted from the heat pumps 13, 14 have a higher temperature level than the heats W1 and W3 supplied from the first electrolyzer 10 and the second electrolyzer 11.The heat quantities W1, W2, W3 and W4 described herein are bound in a heat transfer fluid, which is supplied to and removed from the heat pumps 13, 14 as a heat flow.
[0051] Figure 1 shows an embodiment in which the heat W1 from the first electrolyzer 10 is supplied, for example, directly to the second electrolyzer 11 for heating via a first fluid line 16b. For this purpose, a heat storage device 20, for example a thermal battery, can be interposed, to which the fluid line 16c leads from the first electrolyzer 10 and which is connected to the second electrolyzer 11 via the fluid line 16e. The heat W1 from the first electrolyzer 10 is additionally and / or alternatively supplied via the fluid line 16b to a first heat pump 13, which is operated with electrical energy, represented by an electrical symbol, so that heat W1 at a lower temperature is converted into heat W2 at a higher temperature, which can then be fed, for example, into a district heating network 15.
[0052] The second electrolyzer 11 can also be heated via a fluid line 16b to the first heat pump 13 and via a second section 16d from the first heat pump 13. Waste heat from the second electrolyzer 11 can be supplied to the first heat pump 13 via the second fluid line 17 and / or the waste heat from the second electrolyzer 11 can be returned to the first electrolyzer 10 for heating via the second fluid line 17. A further portion of the waste heat from the second electrolyzer 11 can also be supplied to a district heating network 15, for example.
[0053] If the second electrolyzer 11 is supplied with water 12, this water can be evaporated via a heat exchanger 19 by supplying the heat W1 from the first electrolyzer 10 to the heat exchanger 19 via fluid line 16a. In a manner not shown in detail, the heat exchanger 19 can also be heated according to this arrangement so that the appropriate temperature is reached to evaporate the water 12 supplied to the second electrolyzer 11 and bring it to the required temperature. Figure 2 shows a modified embodiment in which the heat W1 from the first electrolyzer 10 is supplied completely to the first heat pump 13 via a first fluid line 16.This generates heat W2 of a higher temperature from the first heat pump 13, which is supplied via the fluid line 16d to the heat exchanger 19 and directly to the second electrolyzer 11 for heating, as shown by the heat W2 from the first heat pump 13. The first fluid line 16d serves this purpose, transporting a suitable heat transfer fluid.
[0054] Furthermore, a second heat pump 14 is installed, which absorbs the heat W3 from the second electrolyzer 11 and supplies it, at a higher temperature, to the second electrolyzer 11 via a further section of the second fluid line 18. Similarly, the heat W4 from the second heat pump 14 can also be supplied to the heat exchanger 19.
[0055] Finally, the heat from the second heat pump 14 can also be supplied to a district heating network 15 together with the heat W3 from the second electrolyzer 11.
[0056] Figure 3 shows a cascade arrangement of several individual heat pumps 13a, 13b, 13c, each receiving heat from the preceding heat pump 13a, 13b, where the introduced water 12 is evaporated in the heat exchanger 19 for the second electrolyzer 11. Heat from the second heat pump 14 can also be transferred via individual pipes to the individual heat pumps 13a, 13b, 13c.
[0057] For individual heat pumps 13a, 13b, 13c, a fluid line 16d for transferring heat W2 to the second electrolyzer 11 is also possible, although this option is merely an additional example. With such an arrangement of several individual heat pumps 13a, 13b, 13c, a much larger temperature difference can be achieved between the temperature of the heat transfer fluid for heat W1 and the temperature of the heat transfer fluid for heat W2. In the same arrangement, heat pump 14 can also comprise several individual heat pumps.
[0058] The invention is not limited in its implementation to the preferred embodiment described above. Rather, a number of variants are conceivable, which utilize the solution presented even in fundamentally different designs. All features and / or advantages arising from the claims, the description, or the drawings, including design details or spatial arrangements, can be essential to the invention, both individually and in various combinations.
[0059] Reference symbol list:
[0060] I Electrolyzer system
[0061] 10 first electrolyzer
[0062] II second electrolyzer
[0063] 12 Water
[0064] 13 first heat pump
[0065] 13a Single heat pump
[0066] 13b Single heat pump
[0067] 13c Single heat pump
[0068] 14 second heat pump
[0069] 15 District heating network
[0070] 16 first fluid line
[0071] 16a Fluid line
[0072] 16b Fluid line
[0073] 16c Fluid line
[0074] 16d Fluid line
[0075] 16e Fluid line
[0076] 17 second fluid line
[0077] 18 third fluid line
[0078] 19 heat exchangers
[0079] 20 heat storage units
[0080] 21 Heating unit 100 Hydrogen
[0081] W1 Heat of the first electrolyzer
[0082] W2 Heat from the first heat pump
[0083] W3 Heat from the second electrolyzer W4 Heat from the second heat pump
[0084] Qpoint heat supply
Claims
Claims:
1. A method for operating an electrolyzer system (1) with which water is converted into oxygen and hydrogen (100), wherein at least one first electrolyzer (10) of the first type is provided, which generates heat (W1) during the formation of hydrogen (100), and wherein at least one second electrolyzer (11) of a second type, differing from the first type, is provided, to which at least a portion of the heat (W1) from the first electrolyzer (10) is supplied at least indirectly for operation, and wherein at least one first heat pump (13) is provided, to which at least a portion of the heat (W1) from the first electrolyzer (10) is supplied, and in that heat (W2) is provided by means of the first heat pump (13), which is transferred to the second electrolyzer (11), characterized in that the heat (W2) from the first heat pump (13) is supplied via a fluid line (16d) to a heat exchanger (19) directly to the second electrolyzer (11) for heating. becomes,by evaporating water (12) in liquid form in the heat exchanger (19) so that it is supplied as water vapor to the second electrolyzer (11) and wherein a heating device (21) is provided with which the water (12) in the form of water vapor is further heated after the heat exchanger (19).
2. Method according to claim 1, characterized in that the first electrolyzer (10) is formed by means of a proton exchange membrane electrolyzer and / or that the second electrolyzer (11) is formed by means of a high-temperature electrolyzer, or that the first electrolyzer (10) is formed by means of a high-temperature electrolyzer and / or that the second electrolyzer (11) is formed by means of a proton exchange membrane electrolyzer.
3. Method according to claim 1 or 2, characterized in that the heat (W1) of the first electrolyzer (10) is used at least partly directly for preheating, heating and / or preheating the water supplied to the second electrolyzer (11).
4. Method according to one of the preceding claims, characterized in that water (12) is supplied to the second electrolyzer (11), wherein the heat (W1) of the first electrolyzer (10) is at least partially transferred to the supplied water (12) and the water (12) is heated and / or the water (12) is evaporated.
5. Method according to one of the preceding claims, characterized in that the first heat pump (13) is located upstream of the heating device (21), so that at least a part of the heat (W1) of the first electrolyzer (10) is supplied to the first heat pump (13) and / or that heat (W2) is transferred to the water (12) supplied to the second electrolyzer (11) by means of the first heat pump (13), in particular to evaporate the water (12).
6. Method according to one of the preceding claims, characterized in that the second electrolyzer (11) generates heat (W3) during operation, wherein at least a part of the heat (W3) of the second electrolyzer (11) is supplied to the first heat pump (13) and / or to the water (12) supplied to the second electrolyzer (11).
7. Method according to one of the preceding claims, characterized in that the heating device (21) is configured to heat the water (12) which is supplied to the second electrolyzer (11), wherein the heating device (21) is located downstream of the first heat pump (13), so that the heating device (21) further heats the water (12) evaporated by the first heat pump (13).
8. Method according to one of the preceding claims, characterized in that at least a second heat pump (14) is provided, to which at least a part of the heat (W3) of the second electrolyzer (11) is supplied.
9. Method according to claim 8, characterized in that the second heat pump (14) provides heat (W4) which is supplied to the second electrolyzer (11) and / or the heat exchanger (19) and / or the first electrolyzer (10).
10. Method according to one of the aforementioned claims, characterized in that 21 that a district heating network (15) is set up, wherein the heat (W2) from the first heat pump (13) and / or the heat (W3) from the second electrolyzer (11) and / or the heat (W4) from the second heat pump (14) is supplied to the district heating network (15).
11. Method according to one of the preceding claims, characterized in that the first heat pump (13) is a cascade of several individual heat pumps (13a, 13b, 13c) operating in series.
12. Method according to one of the preceding claims, characterized in that the heat (W1) from the first electrolyzer (10) is provided via a heat transfer fluid with a temperature of 45°C to 65°C and / or of 50°C to 60°C.
13. Method according to one of the preceding claims, characterized in that the heat (W2) from the first heat pump (13) is supplied to the second electrolyzer (11) via a heat transfer fluid with a temperature of over 100°C to 900°C.
14. Electrolyzer system (1) for converting water into oxygen and hydrogen (100), wherein at least one first electrolyzer (10) of the first type and at least one second electrolyzer (11) of a second type different from the first type are provided, wherein a first fluid line (16) is provided from the first electrolyzer (10) to the second electrolyzer (11), through which at least part of the heat (W1) of the first electrolyzer (10) is transferred at least indirectly to the second electrolyzer by means of a heat transfer fluid. 22 (11) is transferable, wherein at least one first heat pump (13) is configured such that at least a part of the heat (W1) from the first electrolyzer (10) can be supplied to it, and wherein the first heat pump (13) is configured to supply heat (W2) to the second electrolyzer (11), characterized in that a heat exchanger (19) is provided to supply heat (W2) of higher temperature from the first heat pump (13) directly to the second electrolyzer (11) for heating via a fluid line (16d), by evaporating water (12) in liquid form in the heat exchanger (19) so that it is supplied as water vapor to the second electrolyzer (11), and wherein a heating device (21) is provided with which the supplied water (12) is further heated after the heat exchanger (19).
15. Electrolyzer system (1) according to claim 14, characterized in that at least a second heat pump (14) is provided to which heat (W3) from the second electrolyzer (11) can be supplied via a second fluid line (17) and / or wherein a third fluid line (18) is provided through which heat (W4) from the second heat pump (14) can be supplied at least indirectly or directly to the first heat pump (13) and / or the heat exchanger (19) and / or the second electrolyzer (11) by means of a heat transfer medium.