Method for operating a fuel cell system and control device
By detecting parameters of key components of the fuel cell system before shutdown and activating the heat release device, the problem of water condensation during cold or ice-based startup of the fuel cell system is solved, achieving rapid drying and reliable startup.
Patent Information
- Application Number
- CN202480033055.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-05-17
- Filing Date
- 2024-05-10
- Publication Date
- 2026-01-09
AI Technical Summary
Fuel cell systems face the problem of ice layers obstructing the supply of reactant gases during cold or ice-based starts, which delays system startup.
By detecting parameters of critical components and comparing them with limit values before shutting down the fuel cell system, heat release devices such as heaters or cooling circuits are activated to ensure heating of critical components and prevent water condensation.
This effectively avoids delays during ice start-up, ensures rapid drying of the fuel cell system, and improves the reliability of cold and ice start-up.
Smart Images
Figure CN121311980A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for operating a fuel cell system and a control device configured to perform the steps of the method. Background Technology
[0002] Fuel cells convert fuels, such as hydrogen and oxygen, into electricity, heat, and water. To increase power, multiple fuel cells are typically connected in a fuel cell stack, and reactant gases are supplied via a supply channel running through the stack. Air is typically used as the oxygen donor, extracted from the surrounding environment and supplied to the cathode of the fuel cell stack. The fuel required for the anode of the fuel cell stack is stored in a suitable tank or storage system and metered using a metering valve. To conserve fuel, lean fuel from the fuel cell can be recycled via the anode loop. Recycling can be passively initiated by an ejector pump integrated in the anode loop and / or actively initiated by a recirculation blower integrated in the anode loop. All components together form a fuel cell system.
[0003] Water that accumulates during fuel cell system operation can freeze at low ambient temperatures when the system is shut down—if it is not separated and removed. There is a danger during fuel cell system restart, especially during ice starts, that ice can block the supply of the required reactant gases to the fuel cell. Therefore, liquid water is removed from the system using a water separator during operation. However, after shutdown, water vapor in the reactant gases can condense as the system cools further, posing a risk of freezing at low ambient temperatures. Furthermore, the fuel cell must first be brought to operating temperature during cold or ice starts. Summary of the Invention
[0004] The present invention therefore addresses the task of improving the cold-start capability and / or ice-start capability of fuel cell systems. To solve this task, a method having the features of claim 1 is proposed. Advantageous further extensions of the invention can be derived from the dependent claims. Furthermore, control equipment for implementing the steps of the method according to the invention is provided.
[0005] In the proposed method for operating a fuel cell system, the fuel cell stack is supplied with gaseous fuel, particularly hydrogen, at the anode side and with air as an oxygen donor at the cathode side. The following steps are performed before shutting down the fuel cell system: a) Determine at least one parameter within the fuel cell system and compare said at least one parameter with at least one pre-given first limit value; b) If the value is below the first limit, activate at least one device for releasing thermal energy at a critical location and / or component within the fuel cell system; c) Begin the drying process.
[0006] The proposed method allows for the reliable and efficient shutdown of fuel cell systems, particularly in a manner suitable for ice-start conditions. This method is ideal for short-distance travel, where critical components do not require sufficient warm-up. Under normal conditions, especially during longer trips or in high ambient temperatures, the anode and cathode systems are adequately heated through the accumulated operating time, which facilitates their drying. In exceptional cases, such as short-distance travel (“buying bread”), the operating time may be insufficient to heat the air system or anode system.
[0007] During the drying phase, the fuel cell stack is dried well because it reaches the operating temperature of approximately 65°C required for the drying phase relatively quickly. Water extracted from or blown out of the fuel cell stack condenses and subsequently freezes on critical components or parts of the air or anode systems, as cold surfaces remain in the rest of the system. This results in delays during ice start-up, as the frozen areas and / or components must first be thawed.
[0008] The method according to the invention avoids undesirable delays during ice startup. The method according to the invention ensures that, when the fuel cell system is shut down, no critical parts and / or components experience condensation due to low temperatures, thus preventing the formation of ice layers on these critical parts and / or components that would hinder subsequent startup.
[0009] By determining at least one parameter within the fuel cell system and comparing said at least one parameter with at least one pre-given first limit value performed in step a), it can be checked whether there are critical locations and / or components within the fuel cell system where water may condense during the drying process.
[0010] Before starting the drying process in step c), the critical parts and / or components are heated by activating at least one device for releasing heat energy on critical parts and / or components within the fuel cell system in step b).
[0011] Advantageous configurations and further extensions of the apparatus according to the invention for reducing the hydrogen concentration in the exhaust gas of a fuel cell system are given in the dependent claims.
[0012] Advantageously, after activating at least one device for releasing heat energy on critical parts and / or components, a predetermined time is waited before performing step c), during which the critical parts and / or components may heat up.
[0013] It is advantageous if at least one parameter mentioned in step a) is the turn-on time of the fuel cell system and this turn-on time is compared with a first time limit, because in this way it can be checked whether critical parts and / or components in the fuel cell system have had sufficient time to heat up. It is particularly advantageous if the first time threshold is determined based on the ambient temperature, because at particularly low ambient temperatures, the time span for heating critical parts and / or components can be longer.
[0014] It is advantageous if, due to the high precision and the possibility of individual analysis and evaluation of each component, at least one parameter mentioned in step a) is the actual temperature of the anode side and / or cathode side, and this actual temperature is compared with a first temperature limit. In this case, the actual temperature of the anode side and / or cathode side within the fuel cell system can be detected by means of at least one temperature sensor.
[0015] It is advantageous if at least one heater arranged on the anode side and / or cathode side is activated in step b), as this enables localized heating of critical parts and / or components. Alternatively, at least one cooling circuit may be coupled to the critical parts and / or components in step b).
[0016] It is particularly advantageous to determine when the drying process begins by performing heat calculations over time and / or by querying the temperature, since steps a) and b) do not need to be repeated and can proceed directly to step c.
[0017] When implementing the method according to the invention, at least one electric heater, such as a PTC heating element and / or a resistance heater, can preferably be used. The electric heater requires little installation space and is particularly robust, allowing it to be integrated almost anywhere in the fuel cell system. The PTC heating element further has the advantage of being self-regulating, thus preventing overheating. When using a resistance heater, overheating can be prevented by means of a temperature sensor that regulates the temperature of the resistance heater. The temperature sensor can be integrated into the resistance heater.
[0018] At least one electric heater can preferably be powered by a battery. In mobile applications, batteries are particularly important for motor vehicles.
[0019] Furthermore, a control device for a fuel cell system is proposed, configured to implement the steps of the method according to the invention. With the aid of the control device, the method can be largely automated. For this purpose, the corresponding limit values are preferably stored in the control device. Based on the result of one or more comparisons, at least one device for releasing thermal energy can be activated by means of the control device. Attached Figure Description
[0020] The invention will now be further described with reference to the accompanying drawings. The drawings show: Figure 1 : A schematic diagram applicable to a fuel cell system performing the method according to the invention, and Figure 2 : A flowchart describing the process of the method according to the present invention. Detailed Implementation
[0021] exist Figure 1 The fuel cell system 1 shown includes a fuel cell stack 2, which is supplied with fuel, such as hydrogen, at the anode side and with air as an oxygen donor at the cathode side during system operation.
[0022] Fuel is stored in tank 11 and metered into anode circuit 18 via metering valve 12. Through anode circuit 18, both fresh fuel as anode gas and recirculated anode gas are supplied to fuel cell stack 2. For passive recirculation, an injection pump 13 is integrated into anode circuit 18. A recirculation blower 14 is also provided, by which anode gas can be actively recirculated. Because the anode gas exiting fuel cell stack 2 may contain liquid water, the aforementioned anode gas is supplied to water separator 15. If the water separator is full, vent valve 16 can be opened to vent it. The anode circuit can be flushed by opening flush valve 17.
[0023] The air supplied to the fuel cell stack 2 is extracted from the surrounding environment and is therefore first supplied to the air filter 23. The air is then compressed by the air compressor 21, as the electrochemical processes in the fuel cell require a certain air mass flow rate and a certain pressure level. The air compressor 21 is arranged downstream of the air filter 23 in the cathode inlet path 19. A turbine 22 is arranged in the cathode exhaust path 20, through which the air exiting the fuel cell stack 2 is discharged; the turbine drives the air compressor 21 or supports an electric drive (not shown) for the air compressor 21. A portion of the energy used for compression can be recovered by means of the turbine 22. The cathode inlet path 19 and the cathode exhaust path 20 are further connected by another component. In this case, it can be a humidification device 24, for example, in the form of a membrane humidifier, and / or a heat transfer device. The humidity and / or temperature of the air in the cathode inlet path 19 can be adjusted by means of this other component.
[0024] The fuel cell stack 2 shown is further connected to a cooling circuit 5, which is used to cool the fuel cell stack 2 during system operation. The cooling circuit includes a cooling medium pump 9 for delivering a cooling medium through the fuel cell stack 2. Additionally, a three-way valve 26 is integrated into the cooling circuit 5 for switching a bypass path 27, which bypasses the vehicle cooler 28.
[0025] Temperature sensors 8 are integrated in the cooling circuit 5 in the inlet 6 region entering the fuel cell stack 2 and in the outlet 7 region exiting the fuel cell stack 2. Additional temperature sensors 8 are located in the inlet or outlet regions of the anode circuit 18, cathode inlet path 19, and cathode exhaust path 20, respectively. The actual temperatures of the reactant gases and cooling medium on the anode and / or cathode sides can be detected using the temperature sensors 8. The core temperature of the fuel cell stack 2 can then be deduced from the cooling medium temperature.
[0026] exist Figure 1 The temperature sensor 8 shown provides its measured value to the control device 10, which compares the measured value—especially when the system is shut down—with a first limit value stored in the control device 10. If the comparison indicates that the value is below at least one first limit value, at least one heater 3, 4 is activated.
[0027] exist Figure 1 The diagram illustrates multiple heaters 3 and 4, but not all of these heaters are required. Furthermore, the locations shown are merely illustrative and may be changed.
[0028] The first heater 3 is integrated on the anode side into a component at risk of icing. In this case, the component is the jet pump 13, the recirculation blower 14, the water separator 15, the vent valve 16, and the temperature sensor 8 arranged on the inlet side. Another first heater 3 is integrated on the cathode side into a valve 25, which is arranged in the cathode exhaust path 20.
[0029] At least one second heater 4 is integrated into the cooling circuit 5, specifically into the region of the pump integrated into the bypass path. Alternatively, the heater 4 may be arranged in the region of the coolant pump 9 or at any other location within the cooling circuit 5. Figure 1 The location is shown in the diagram. By activating at least one heater 3, 4, the fuel cell system 1 can be targeted to heat critical parts and / or components during system shutdown.
[0030] The method for operating a fuel cell system, and in particular shutting down a fuel cell system, according to the present invention is as follows: Figure 2 To be explained.
[0031] Once the control device 10 receives the command "stop" (step 100), the parameters within the fuel cell system 1 are first determined by the control device 10.
[0032] This parameter can be the actual temperature on the anode side and / or the cathode side. Preferably, the actual temperature on the anode side and / or the cathode side is determined at critical locations and / or components within the fuel cell system 1.
[0033] Critical areas and / or components within fuel cell system 1 are regions that heat up more slowly than the rest of fuel cell system 1. Due to the still-cold surfaces, water extracted or blown from the reactor by the air system or H2 system condenses and may even freeze at critical areas and / or components.
[0034] The at least one parameter is then compared with at least one pre-given first limit value in method step 110. If the at least one parameter is the actual temperature on the anode side and / or the cathode side, it is compared with the first limit value for temperature.
[0035] In an alternative implementation, the parameter may be the on-time of the fuel cell system since startup. This on-time is then compared with a first limit value of time in method step 110.
[0036] The first time limit can be fixed and predetermined or determined based on the ambient temperature of the fuel cell system.
[0037] If the parameter is less than the first limit value, then at least one device for releasing thermal energy at a critical location and / or component 3 within the fuel cell system 1 is activated in method step 120.
[0038] If the parameter is greater than the first limit value, the drying process is initiated in method step 130 because there are no critical parts, components or areas within the fuel cell system 1 that could have temperatures that could cause water to condense.
[0039] After method step 120, optional method step 140 may be performed, in which, after activating at least one device for releasing heat energy on the critical part and / or component 3, a predetermined time is waited before performing method step 130.
[0040] The device for releasing heat energy on critical parts and / or components 3 may be at least one heater arranged on the anode side and / or cathode side, which is activated in method step 120.
[0041] Alternatively or additionally, at least one cooling circuit may be coupled to a critical part and / or component. To raise the cooling circuit to the desired temperature, another heater 4 in the cooling circuit may be activated. To couple the cooling circuit to the critical part and / or component, a valve may be opened to allow heated cooling liquid to flow from the cooling circuit to the critical part and / or component. At least one electric heater 3, 4 may be, for example, a PTC heating element and / or a resistance heater preferably powered by a battery.
[0042] After activating at least one device for releasing heat energy on critical parts and / or components 3, the timing of the drying process can be determined by heat calculation over time and / or by temperature query.
Claims
1. A method for operating a fuel cell system (1), wherein the fuel cell stack (2) of the fuel cell system (1) is supplied with gaseous fuel, particularly hydrogen, at the anode side and with air as an oxygen donor at the cathode side, and wherein the following steps are performed before shutting down the fuel cell system (1): a) Determine at least one parameter within the fuel cell system (1) and compare the at least one parameter with at least one pre-given first limit value; b) If the value is below the first limit, at least one device for releasing heat energy on critical parts and / or components (3, 4) within the fuel cell system (1) is activated; c) Begin the drying process.
2. The method according to claim 1, characterized in that, After activating at least one device for releasing heat energy on critical parts and / or components (3, 4), wait for a predetermined time before performing step c).
3. The method according to claim 1, wherein, In step a), the at least one parameter is the turn-on time of the fuel cell system, and the turn-on time is compared with a first limit value of time.
4. The method according to claim 3, wherein, The first threshold for time is determined based on the ambient temperature.
5. The method according to claim 1, wherein, In step a), the at least one parameter is the actual temperature on the anode side and / or the cathode side, and it is compared with a first limit value of temperature.
6. The method according to claim 1 or 2, wherein, The actual temperature of the anode side and / or cathode side within the fuel cell system (1) is detected by means of at least one temperature sensor (8).
7. The method according to any one of the preceding claims, wherein, In step b), at least one heater (3) arranged on the anode side and / or cathode side is activated.
8. The method according to any one of the preceding claims, wherein, In step b), at least one cooling circuit is coupled to the critical location and / or component.
9. The method according to any one of the preceding claims, wherein, The timing of the drying process is determined by performing heat calculations over time and / or by querying temperature.
10. A control device for a fuel cell system (1), the control device being configured to implement the steps of the method according to any one of the preceding claims.