Electrochemical system, and method for operating an electrochemical system

Abstract

The present invention relates to an electrochemical system (100) for power generation or for electrolysis, having a media supply region (10) for supplying media (40), wherein the media (40) have a reactant (42) and air (44), a cell stack (30) comprising a plurality of electrochemical cells (32), and a media feed region (20) for controlling the temperature of the media (40) and for conducting the media (40) from the media supply region (10) to the cell stack (30). The media feed region (20) has at least two heat exchangers (62, 64) and at least two electric heaters (22, 24) for indirectly heating a reactant inflow (28) comprising the reactant (42) in two stages, wherein the media feed region (20) has a first electric heater (22) for heating a first air flow (52) and a first heat exchanger (62) in order to heat the reactant inflow (28) to the cell stack (30) by means of the first heat exchanger (62) and the first air flow (52) in a first stage, wherein the media feed region (20) has a second electric heater (24) for heating a second air flow (54) and a second heat exchanger (64) in order to heat the reactant inflow (28) to the cell stack (30) by means of the second heat exchanger (64) and the second air flow (54) in a second stage, wherein the media feed region (20) has a third electric heater (26) for heating an air inflow (56) for feeding to the cell stack (30).

Description

[0001] PP34385WO / bg October 30, 2025 AVL List GmbH

[0002] Electrochemical system and method for operating an electrochemical system

[0003] The present invention relates to an electrochemical system for generating electricity or for electrolysis, and to a method for operating an electrochemical system for controlling the temperature of a reactant inflow.

[0004] Electrochemical systems for power generation or electrolysis are known in the prior art. Solid oxide fuel cells (SOFCs) require a very high temperature to maintain the electrochemical conversion until they reach their thermoneutral operating point. At this thermoneutral point, they can efficiently generate electricity and also supply excess heat via the exothermic oxidation of various gases as reactants.

[0005] Typically, complex heating conditions are preset to meet the various requirements of a cell stack in an electrochemical system. Furthermore, during operation at high temperatures, reactants are fed into the electrochemical cells of the cell stack because of limitations imposed by thermal or chemical stresses in the reactive layers of the electrochemical cells.

[0006] In so-called high-temperature co-electrolysis (Co-Solid Oxide Electrolyzer Cell: Co-SOEC; parallel H₂O & CO₂ high-temperature co-electrolysis), the reactants are also fed to the electrolysis cells at high temperatures. The carbon dioxide (CO₂) can originate from various sources (direct air capture, biogas processes, industrial exhaust gases, etc.). The water (H₂O) must be in vapor form. Depending on the CO₂ concentration and operating point, heat is also required for this process.

[0007] Consequently, heating and maintaining a high operating temperature of SOFC / SOEC systems is crucial for their operability, lifespan, and sustainability.

[0008] Against this background, one object of the present invention is to at least partially overcome the disadvantages described above. In particular, it is an object of the present invention to provide an electrochemical system PP34385WO / bg 30.10.2025 AVL List GmbH in which the heating of a reactant inflow is improved and which is flexible with regard to the reactants used and the mode of operation (current generation or electrolysis).

[0009] The foregoing problems are solved by an electrochemical system with the features of claim 1 and a method for operating an electrochemical system with the features of claim 7. Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings. Features and details described in connection with the electrochemical system according to the invention naturally also apply in connection with the method according to the invention for operating an electrochemical system, and vice versa, so that the disclosure of the individual aspects of the invention always refers, or can refer, to each other.

[0010] Accordingly, an electrochemical system for power generation or electrolysis is described. The electrochemical system comprises a media supply area for supplying the system with media, wherein the media consist of a reactant and air, a cell stack comprising several electrochemical cells, and a media feed area for temperature control of the media and for conveying the media from the media supply area to the cell stack. The media feed area includes at least two heat exchangers and at least two electric heaters for indirectly heating a reactant feed stream comprising the reactant in two stages.

[0011] By providing at least two heat exchangers and at least two electric heaters for indirect heating of the reactant inflow, the reactant inflow can be heated indirectly, thus allowing the configuration of the electrochemical system to be designed flexibly.

[0012] Accordingly, the choice of media can be flexible. The media can consist of either the reactant or air. Therefore, the media can contain both the reactant and air.

[0013] The reactant can include hydrogen (H₂), water (H₂O), carbon monoxide (CO), carbon dioxide (CO₂), and / or methane (CH₄) and / or other hydrocarbons. Nitrogen (N₂) and / or a protective gas (PP34385WO / bg 30.10.2025 AVL List GmbH) can also be added to the reactant. This can be beneficial during the start-up and stop-down processes of the electrochemical system.

[0014] The electrochemical system can be used under real-world conditions as a solid oxide fuel cell (SOFC), a solid oxide electrolyzer cell (SOEC), or a solid oxide co-electrolyzer cell (Co-SOEC). It can also serve as a test environment for SOFCs, SOECs, or Co-SOECs to test individual components, such as the cell stack. The system allows for flexible configuration of the media supplied to the cell stack and flexible configuration of the operating mode, i.e., fuel cell or electrolyzer.

[0015] Furthermore, the combination of heat exchangers and electric heaters for indirect heating of the reactant inflow, together with the reactant, water vapor and air supply, allows for a flexible configuration for the media and the operating mode.

[0016] The present invention contributes to the state of the art by providing a more flexible and simpler infrastructure that enables efficient connection of the media to the cell stack. This can shorten installation and commissioning times and thereby facilitate efficient testing. Simplicity and flexibility are paramount in the present invention. Accordingly, no afterburner or heat exchanger is used for the exhaust gas flows of the cell stack. Furthermore, the design of the present invention does not include an oil bath heat exchanger or a bypass path.

[0017] A stage can be a location where the reactant inflow is heated. Accordingly, the reactant inflow can be heated in two stages, i.e., at two different locations.

[0018] The electrochemical system can be a fuel cell system for generating electricity with at least one fuel cell stack, or an electrolysis system for electrolysis with at least one electrolysis cell stack.

[0019] According to the invention, in the electrochemical system the media supply area has a first electric heater for heating a first air stream and PP34385WO / bg 30.10.2025 AVL List GmbH a first heat exchanger to heat the reactant flow to the cell stack by means of the first heat exchanger and the first air stream in a first stage.

[0020] Advantageously, the reactant inflow is indirectly heated by the first electric heater. The first airflow is heated by the first electric heater. Afterwards, the first airflow is passed through the first heat exchanger and transfers its heat to the reactant inflow.

[0021] According to the invention, the media supply area of ​​the electrochemical system has a second electric heater for heating a second air stream and a second heat exchanger to heat the reactant flow to the cell stack in a second stage by means of the second heat exchanger and the second air stream.

[0022] Advantageously, the reactant inflow is indirectly heated by the second electric heater. The second airflow is heated by the second electric heater. This second airflow is then passed through the second heat exchanger, where it transfers its heat to the reactant inflow.

[0023] The reactant flow is heated by the second heat exchanger in the direction of the reactant flow downstream of the first heat exchanger. The heating of the reactant flow occurs in two stages: in the first stage, the reactant flow is heated by the first heat exchanger in the direction of the reactant flow upstream of the first stage, and in the second stage, the reactant flow is heated by the second heat exchanger.

[0024] According to the invention, the electrochemical system has a media supply area with a third electric heater for heating an air stream supplied to the cell stack. The air stream is heated directly by means of this third electric heater. This allows for a very simple design. Alternatively, it can also be advantageous to heat the air stream to the cell stack indirectly.

[0025] According to a further embodiment of the electrochemical system, the media supply area has a third electric heater for heating a third airflow and a third heat exchanger to supply an airflow to the PP34385WO / bg 30.10.2025 AVL List GmbH

[0026] The cell stack is heated using the third heat exchanger and the third airflow. The incoming airflow is heated only indirectly by means of the electric heater.

[0027] According to another embodiment of the electrochemical system, the electric heaters have built-in temperature sensors. These are specifically designed and positioned for component protection. Advantageously, this also allows the desired temperature of the corresponding airflows to be precisely set.

[0028] According to a further embodiment of the electrochemical system, the media supply area has a reactant line for conveying reactant to the first heat exchanger and a reactant line heat band, wherein the reactant line is surrounded by the reactant line heat band to prevent condensation in the reactant line.

[0029] The reactant line heat tape is used to insulate the reactant line. This insulation prevents or at least reduces condensation within the reactant line.

[0030] According to a further embodiment of the electrochemical system, the media supply area has a steam line for conveying steam to the first heat exchanger and a steam line heating band, wherein the steam line is surrounded by the steam line heating band to prevent condensation in the steam line.

[0031] The steam pipe insulation tape is used to insulate the steam pipe. This insulation prevents or at least reduces condensation within the steam pipe.

[0032] According to another embodiment of the electrochemical system, the system has a separate reactant exhaust line and a separate air exhaust line. The reactant exhaust line and the air exhaust line are not connected and both terminate in a single exhaust outlet. This exhaust outlet can be located within the media supply area.

[0033] By keeping the two main exhaust pipes separate, flexible operation is possible. PP34385WO / bg 30.10.2025 AVL List GmbH

[0034] Furthermore, a method for operating an electrochemical system for controlling the temperature of a reactant inflow, comprising a reactant for supplying a cell stack of the electrochemical system, is described. The method comprises the following steps:

[0035] Heating an initial airflow using a first electric heater or via a heat exchanger,

[0036] Heating the reactant inflow by means of a first heat exchanger, wherein the first airflow is passed through the first heat exchanger to transfer heat to the reactant inflow,

[0037] Heating a second airflow using a second electric heater, and

[0038] Heating the reactant inflow by means of a second heat exchanger, wherein the second airflow is passed through the second heat exchanger to transfer heat to the reactant inflow.

[0039] Advantageously, the reactant flow is heated in two successive stages. The first stage of heating is achieved by the first heat exchanger. The second stage of heating is achieved by the second heat exchanger.

[0040] A further advantage is that the reactant flow is indirectly heated by the electric heaters. The actual heating of the reactant flow is achieved by the heat exchangers. The electric heaters are the active elements, as they provide the actual heating power. The heat exchangers, on the other hand, can be passive elements. The temperature of the reactant flow can be indirectly controlled via the electric heaters.

[0041] According to one embodiment of the method, the temperatures of the air streams are controlled by means of temperature sensors in the electric heaters. For this purpose, the temperature of the air streams can be continuously monitored by the temperature sensors, and the heating power of the electric heaters can then be regulated accordingly. PP34385WO / bg 30.10.2025 AVL List GmbH

[0042] Alternatively or additionally, the temperature of the reactant inflow can be measured. This temperature can then be used to control the electric heaters accordingly.

[0043] According to a further embodiment of the method, the method includes the following additional step: heating an air stream for supply to the cell stack by means of a third electric heater. Accordingly, the air stream is heated directly by means of the third electric heater.

[0044] According to a further embodiment of the method, the method comprises the following additional steps: heating a third airflow by means of a third electric heater, and heating an air supply to the cell stack by means of a third heat exchanger, wherein the third airflow is passed through the third heat exchanger to transfer heat to the air supply. Accordingly, the air supply is only indirectly heated by means of the third electric heater.

[0045] According to a further embodiment of the method, a reactant supplied to the reactant flow is controlled by at least one mass flow controller with an integrated proportional solenoid valve. The respective proportional solenoid valve is normally closed for safety reasons and is opened during operation if no control of the proportional solenoid valve is available for any reason.

[0046] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments are described in detail with reference to the drawings. The drawings show:

[0047] Fig. 1 shows a schematic view of an electrochemical system; and

[0048] Fig. 2 shows a flowchart of a process for operating an electrochemical system.

[0049] Fig. 1 shows a schematic view of an electrochemical system 100 for power generation or electrolysis. The electrochemical system 100 can be, among other things, a SOFC, SOEC, or Co-SOEC system. In particular, the electrochemical system 100 can be a test system for testing individual components of the system. The electrochemical system 100 has a media supply area 10, a cell stack 30, and a media feed area 20.

[0050] The cell stack 30 comprises several electrochemical cells 32, a cell stack reactant inlet 72, a cell stack reactant outlet 74, a cell stack air inlet 76 and a cell stack air outlet 78.

[0051] Media supply area 10 comprises media 40. Media 40 can contain at least one reactant 42, nitrogen N2, a protective gas 98, water 38, and air 44. Reactant 42 can contain hydrogen H2, carbon monoxide CO, carbon dioxide CO2, and / or methane CH4. All different media can be stored in separate storage tanks. Media supply area 10 can additionally include a power supply 12, an air outlet 14, and an exhaust outlet 16.

[0052] The media feed area 20 serves to temper the media 40 and to convey the media 40 from the media supply area 10 to the cell stack 30. For this purpose, the media feed area 20 has at least two heat exchangers 62, 64 and at least two electric heaters 22, 24. A reactant inflow 28 comprising the reactant 42 is indirectly heated in two stages by means of the heat exchangers 62, 64 and the electric heaters 22, 24.

[0053] As shown in Fig. 1, the reactant inflow 28, comprising reactant 42, is directed via the first heat exchanger 62 and then via the second heat exchanger 64 to the cell stack reactant inlet 72 of the cell stack 30. The first airflow 52 is passed through the first electric heater 22 and heated there. The heated airflow 52 is then passed through the first heat exchanger 62 and transfers its heat to the reactant inflow 28. The first stage of heating the reactant inflow 28 takes place at the first heat exchanger 62.

[0054] The second airflow 54 is passed through the second electric heater 24 and heated by it. The heated airflow 54 then passes through the second heat exchanger 64, where it transfers its heat to the reactant supply 28. The second stage of heating the reactant supply 28 takes place in the second heat exchanger 64 (PP34385WO / bg 30.10.2025 AVL List GmbH), as the second heat exchanger 64 is located downstream of the first heat exchanger 62 in the direction of the reactant supply 28 flow.

[0055] As can be seen in Fig. 1, the media supply area 20 additionally has a third electric heater 26. The third electric heater 26 heats the air supply 56, which is fed to the cell stack air inlet 76. The air supply 56 is thus heated directly.

[0056] Alternatively, as not shown in Fig. 1, the media supply area 20 could include a third electric heater 26 for heating a third airflow and a third heat exchanger. The airflow 56 to the cell stack 30 could then be heated by means of the third heat exchanger and the third airflow. Here, the airflow 56 is heated only indirectly.

[0057] All electric heaters 22, 24, 26 can have built-in temperature sensors for regulating the temperature of the electric heaters 22, 24, 26. This allows the corresponding airflows 52, 54, 54 to be tempered as desired.

[0058] The air 44, which may be compressed air, is passed through an air pressure valve 80 and then divided into the first air stream 52, the second air stream 54, and the air supply stream 56. Additionally, a first air valve 82 may be located in the first air stream 52, a second air valve 84 in the second air stream 54, and a third air valve 86 in the air supply stream 56. Furthermore, the air pressure valve 80, the first air valve 82, the second air valve 84, and the third air valve 86 may be located in the media supply area 10.

[0059] Furthermore, the air 44 can also be directed via a vent valve 60 and an element 92 to the first airflow 52, ​​to the second airflow 54, and to the air supply 56. The vent valve 60 and the element 92 can be located in the media supply area 10.

[0060] The various reactants 42 and the nitrogen N2 can each be routed through a mass flow controller 50 and can be fed into the reactant line 46 via a mixer M. This allows the mass flow controller 50 to determine the quantity of each reactant 42 and the quantity of nitrogen N2 present in the reactant inflow 28. PP34385WO / bg 30.10.2025 AVL List GmbH

[0061] Each mass flow controller 50 can have an integrated proportional solenoid valve to regulate the respective mass flow. For safety reasons, the integrated proportional solenoid valve is normally closed and opens during operation. This is the case as long as no control signals are applied to the integrated proportional solenoid valve.

[0062] A protective gas 98 can also be fed into the reactant line 46 via a vent valve 18 and an element 94 via the mixer M.

[0063] The vent valve 18 and element 94, as well as the exhaust outlet 16 and element 92, are specifically designed as venting paths and vent valves, which are used in the event of an emergency shutdown of the system. The vent valve 18 and the exhaust outlet 16 are closed during normal operation but are opened during non-power operation. Elements 92 and 94 are preferably designed as mechanical rotameters, which are configured to protect the system even in the event of a failure, allowing the system to be shut down in a controlled manner.

[0064] The media supply area 10 can further include a water tank for water 38, a water pump 70, and a water flow meter 90. The water pump 70 can pump the water 38 from the water tank, through the water flow meter 90, to the water evaporator 96. The water flow meter 90 can be used to regulate the pumping speed of the water pump 70. As shown in Fig. 1, the water evaporator 96 is located in the media supply area 20. Alternatively, the water evaporator 96 could also be located in the media supply area 10.

[0065] The steam exiting the water evaporator 96 is directed via the steam line 66 to a mixer M. The reactant line 46 also leads into this mixer M. The reactant inflow 28 is directed from this mixer M.

[0066] The reactant line 46 can be surrounded by a reactant line heating band 48. This can prevent or at least reduce condensation within the reactant line 46. Similarly, the steam line 66 can be surrounded by a steam line heating band 68. This can prevent or at least reduce condensation within the reactant line 46. PP34385WO / bg 30.10.2025 AVL List GmbH

[0067] Condensation within the steam line 66 is prevented or at least reduced.

[0068] After passing through the heat exchangers 62, 64, the first airflow 52 and the second airflow 54 are combined by means of a mixer M and directed to the air outlet 14.

[0069] The cell stack 30, in particular the several electrochemical cells 32, can be supplied with power via the power supply 12.

[0070] The electrochemical system 100 has a separate reactant exhaust line 34, which leads from the cell stack reactant outlet 74 to the exhaust outlet 16, and a separate air exhaust line 36, which leads from the cell stack air outlet 78 to the exhaust outlet 16. A reactant exhaust line backflow preventer 104 can be arranged in the reactant exhaust line 34. Furthermore, an air exhaust line backflow preventer 106 can be arranged in the air exhaust line 36.

[0071] Fig. 2 shows a flowchart of a method for operating an electrochemical system 100. In particular, the temperature of the reactant inflow 28 comprising the reactant 42 can be controlled by means of this method. The reactant inflow 28 serves to supply the cell stack 30 of the electrochemical system 100. The method comprises the following steps:

[0072] In a first step S1, a first airflow 52 is heated by means of a first electric heater 22.

[0073] In a second step S2, the reactant inflow 28 is heated by means of a first heat exchanger 62. For this purpose, the first airflow 52 is passed through the first heat exchanger 62 to transfer heat to the reactant inflow 28.

[0074] In a third step S3, a second airflow 54 is heated by means of a second electric heater 24.

[0075] In a fourth step S4, the reactant inflow 28 is heated by means of a second heat exchanger 64. For this purpose, the second airflow 54 is passed through the second heat exchanger 64 to transfer heat to the reactant inflow 28. PP34385WO / bg 30.10.2025 AVL List GmbH

[0076] Steps S1 to S4 do not need to be performed in the specified order.

[0077] PP34385WO / bg October 30, 2025 AVL Ust GmbH

[0078] Reference symbol list

[0079] 10 Media supply area

[0080] 12 Power supply

[0081] 14 Air outlet

[0082] 16 Exhaust outlet

[0083] 18 Vent valve

[0084] 20 Media feed area

[0085] 22 first electric heater

[0086] 24 second electric heater

[0087] 26 third electric heater

[0088] 28 Reactant influx

[0089] 30 cell stacks

[0090] 32 multiple electrochemical cells

[0091] 34 Reactant exhaust line

[0092] 36 Air exhaust pipe

[0093] 38 Water

[0094] 40 Medium

[0095] 42 Reactant

[0096] 44 Air

[0097] 46 Reactant line

[0098] 48 Reactant line heating band

[0099] 50 mass flow controllers

[0100] 52 first airflow

[0101] 54 second airflow

[0102] 56 Airflow

[0103] 60 Vent valve

[0104] 62 first heat exchanger PP34385WO / bg 30.10.2025 AVL List GmbH

[0105] 64 second heat exchanger

[0106] 66 Water vapor line

[0107] 68 Water vapor line heating tape

[0108] 70 Water pump

[0109] 72-cell stack reactant inlet

[0110] 74-cell stack reactant outlet

[0111] 76-cell stack air intake

[0112] 78-cell stack air outlet

[0113] 80 Air pressure valve

[0114] 82 first air valve

[0115] 84 second air valve

[0116] 86 third air valve 86

[0117] 90 Water flow measuring device

[0118] 92 Element

[0119] 94 Element

[0120] 96 water evaporators

[0121] 98 Shielding gas

[0122] 100 electrochemical system

[0123] 104 Reactant exhaust gas line backflow valve

[0124] 106 Air exhaust pipe backflow valve

[0125] M Mixer

Claims

PP34385WO / bg 30.10.2025 AVL List GmbH Patentansprüche 1. Electrochemical system (100) for power generation or electrolysis, comprising a media supply area (10) for supplying media (40), wherein the media (40) comprise a reactant (42) and air (44), a cell stack (30) comprising several electrochemical cells (32), and a media feed area (20) for temperature-controlling the media (40) and for conveying the media (40) from the media supply area (10) to the cell stack (30), wherein the media feed area (20) comprises at least two heat exchangers (62, 64) and at least two electric heaters (22, 24) for indirectly heating a reactant feed (28) comprising the reactant (42) in two stages, wherein the media feed area (20) comprises a first electric heater (22) for heating a first air stream (52) and a first heat exchanger (62) exhibitsto heat the reactant inflow (28) to the cell stack (30) in a first stage by means of the first heat exchanger (62) and the first airflow (52), wherein the media supply area (20) has a second electric heater (24) for heating a second airflow (54) and a second heat exchanger (64) to heat the reactant inflow (28) to the cell stack (30) in a second stage by means of the second heat exchanger (64) and the second airflow (54), characterized in that the media supply area (20) has a third electric heater (26) for heating an airflow (56) for supplying to the cell stack (30).

2. Electrochemical system (100) according to claim 1, characterized in that the media supply area has a third electric heater (26) for heating a third air stream and a third heat exchanger to heat an air supply (56) to the cell stack (30) by means of the third heat exchanger and the third air stream. PP34385WO / bg October 30, 2025 AVL List GmbH 3. Electrochemical system (100) according to one of the preceding claims, characterized in that the electric heaters (22, 24, 26) have built-in temperature sensors.

4. Electrochemical system (100) according to one of the preceding claims, characterized in that the media supply area (20) has a reactant line (46) for conveying reactant (42) to the first heat exchanger (62) and a reactant line heating band (48), wherein the reactant line (46) is surrounded by the reactant line heating band (48) to prevent condensation in the reactant line (46).

5. Electrochemical system (100) according to one of the preceding claims, characterized in that the media supply area (20) has a steam line (66) for conveying steam to the first heat exchanger (62) and a steam line heating band (68), wherein the steam line (66) is surrounded by the steam line heating band (68) to prevent condensation in the steam line (66).

6. Electrochemical system (100) according to one of the preceding claims, characterized in that the electrochemical system (100) has a separate reactant exhaust line (34) and a separate air exhaust line (36).

7. Method for operating an electrochemical system (100) for controlling the temperature of a reactant inflow (28) comprising a reactant (42) for supplying a cell stack (30) of the electrochemical system (100), characterized by the steps: Heating a first airflow (52) by means of a first electric heater (22), Heating the reactant inflow (28) by means of a first heat exchanger (62), wherein the first airflow (52) is passed through the first heat exchanger (62) to transfer heat to the reactant inflow (28), Heating a second airflow (54) by means of a second electric heater (24), and PP34385WO / bg October 30, 2025 AVL List GmbH Heating the reactant inflow (28) by means of a second heat exchanger (64), wherein the second airflow (54) is passed through the second heat exchanger (64) to transfer heat to the reactant inflow (28), Heating a third airflow by means of a third electric heater (26), and Heating an air inflow (56) to the cell stack (30) by means of a third heat exchanger, wherein the third airflow is passed through the third heat exchanger to transfer heat to the air inflow (56).

8. Method according to claim 7, characterized in that the temperatures of the air streams (52, 54) are controlled by means of temperature sensors in the electric heaters (22, 24).

9. Method according to claim 7 or 8, characterized by the further step: Heating an air stream (56) for supply to the cell stack (30) by means of a third electric heater (26).

10. Method according to one of claims 7 to 9, characterized in that a reactant (42) supplied to the reactant inflow (28) is controlled via at least one mass flow controller (50) with integrated proportional solenoid valve.

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