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WO-2026093270-A1 - METHOD FOR DETERMINING THE STATE OF A FUEL CELL SYSTEM

WO2026093270A1WO 2026093270 A1WO2026093270 A1WO 2026093270A1WO-2026093270-A1

Abstract

The invention relates to a method (100) for diagnosing the state of a fuel cell system (200), the method (100) having the steps of: - starting (101) the fuel cell system (200) with closed anode shut-off valves (207) and closed cathode shut-off valves (209); - opening (103) the anode shut-off valves (207) while the cathode shut-off valves (209) remain closed; - introducing (105) fresh hydrogen into an anode chamber (203) of a fuel cell stack (201) of the fuel cell system (200) while a cathode chamber (205) of the fuel cell stack (201) is closed, - applying (107) an electric charging current to the fuel cell stack (201), the charging current having a reversed polarity relative to a subsequent normal operation such that a voltage applied to respective fuel cells of the fuel cell stack (201) increases; - determining (109) the state of the fuel cell system (200) on the basis of a voltage curve at at least one fuel cell of the fuel cell stack (201) and/or an anode pressure measured by means of at least one anode pressure sensor provided at the anode chamber (203), - opening (111) the cathode shut-off valves (209), and - outputting (113) the state by means of an output interface (215).

Inventors

  • Strahl, Stephan
  • Moeller, Leonie Sophie

Assignees

  • ROBERT BOSCH GMBH

Dates

Publication Date
20260507
Application Date
20251028
Priority Date
20241029

Claims (13)

  1. 1. Method (100) for diagnosing a condition of a fuel cell system (200), wherein the method (100) comprises: Starting (101) the fuel cell system (200) with the anode shut-off valves (207) and cathode shut-off valves (209) closed, Opening (103) the anode shut-off valves (207) while the cathode shut-off valves (209) remain closed, Introducing (105) fresh hydrogen into an anode compartment (203) of a fuel cell stack (201) of the fuel cell system (200), while a cathode compartment (205) of the fuel cell stack (201) is closed, Imprinting (107) an electric charging current onto the fuel cell stack (201), with a polarity reversed relative to a subsequent normal operation, so that a voltage applied to each fuel cell of the fuel cell stack (201) increases, Determining (109) a state of the fuel cell system (200) based on a voltage profile at at least one fuel cell of the fuel cell stack (201) and/or an anode pressure measured by means of at least one anode pressure sensor arranged on the anode space (203), Opening (111) the cathode shut-off valves (209) and outputting (113) the state through an output interface (215). R.415639 - 16 -
  2. 2. Method (100) according to claim 1 , characterized in that the determination of the state of the fuel cell system (200) takes place in a time interval between the start of the imprinting (107) of the electric current onto the fuel cell stack (201) and the opening (111) of the cathode shut-off valves (209).
  3. 3. Method (100) according to claim 1 or 2, characterized in that the state is determined by determining at least one parameter from the following list of parameters: Double layer capacitance, membrane permeability, short-circuit resistance, electrochemically active area of a catalyst.
  4. 4. Method (100) according to one of the preceding claims, characterized in that the charging current is between 5 A/cm 2 and 50 mA/cm 2 .
  5. 5. Method (100) according to one of the preceding claims, characterized in that the introduction of fresh hydrogen into the anode compartment (203) is carried out for a predetermined period between 2 seconds and 30 seconds.
  6. 6. Method (100) according to one of the preceding claims, characterized in that the imprinting (107) of the charging current onto the fuel cell stack (201) and the determination of the state of the fuel cell system (200) before opening the cathode shut-off valves (209) is carried out several times. R.415639 - 17 -
  7. 7. Method (100) according to one of the preceding claims, characterized in that during the introduction of fresh hydrogen into the anode compartment (203), air is conveyed through an air system and directed through a bypass line past the fuel cell stack (201) into an exhaust gas tract.
  8. 8. Method (100) according to one of the preceding claims, characterized in that after imprinting (107) the charging current onto the fuel cell stack (201) and before opening (111) the cathode shut-off valves (209) an electric current with a relatively similar polarity as provided for in normal operation is drawn.
  9. 9. Method (100) according to one of claims 1 to 7, characterized in that the charging current and the anode pressure are adjusted such that a voltage profile measured at at least one fuel cell of the fuel cell stack (201) crosses a predetermined voltage level (Uev) at least three times.
  10. 10. Method (100) according to claim 9, characterized in that the anode pressure is adjusted such that it rises or falls monotonically and the charging current is reduced at least once and then rises again.
  11. 11. Method (100) according to claim 9 or 10, characterized in that the parameters double layer capacitance, membrane permeability, short-circuit resistance and electrochemically active area are determined using an electrochemical equivalent circuit diagram. R.415639 - 18 -
  12. 12. Fuel cell system (200) for converting energy, the fuel cell system (200) comprising: a fuel cell stack (201) comprising an anode compartment (203) and a cathode compartment (205), controllable anode shut-off valves (207) for opening or closing the anode compartment (203), controllable cathode shut-off valves (209) for opening or closing the cathode compartment (205), a hydrogen metering unit (211) for metering hydrogen into the anode compartment (203), a current/voltage source (213) for imposing a charging current on the fuel cell stack (201), an output interface (215) and a computing unit (217), the computing unit (217) being configured to anode shut-off valves (207), the cathode shut-off valves (209), the to control the hydrogen dosing unit (211), the current/voltage source (213) and the output interface (215) in order to carry out a method (100) according to one of claims 1 to 11.
  13. 13. Fuel cell system (200) according to claim 12, characterized in that the fuel cell system (200) comprises a bypass line that connects an air system for conveying air to an exhaust tract of the fuel cell system, wherein the bypass line directs the air past the fuel cell stack (201). ...

Description

R.415639 - 1 - Description Title Method for determining the state of a fuel cell system The presented invention relates to a method for determining a state of a fuel cell system and a fuel cell system according to the attached claims. State of the art Diagnosing the condition of a fuel cell system allows, on the one hand, the user to be informed about this condition and, on the other hand, the fuel cell system to be adjusted or adapted to this condition in order to maximize, for example, its RUL (remaining useful life) and energy efficiency. In this context, the acquisition of detailed information on the electrochemical active surface area (ECSA), membrane permeability and double-layer capacity is particularly relevant. These quantities can be determined using the so-called Galvanostatic Charge Method (GCM) in a stationary flowing gas atmosphere, such as nitrogen on the cathode side and hydrogen on the anode side. One variant (AGCM - Adapted Galvanostatic Charge Method) proposes to perform inerting not by flowing gases, but by a closed inert volume, so that closed anode and cathode shut-off valves are present and no mass exchange with the environment takes place. R.415639 - 2 - The trapped, inert gas volume is processed using the system's own special procedure for shutting down a fuel cell system, known as "cathode oxygen depletion." After deactivating the fuel cell stack, a waiting period of 3–6 hours is required to allow the trapped gases to homogenize through diffusion processes both within the two half-cells and across the membrane between them. An equilibrated state is a prerequisite for initiating state determination or characterization based on a measurement that relies on the fuel cell stack being recharged from its equilibrated state at least once, but preferably several times, with one or more different charging currents. Charging initiates various electrochemical processes that generate a characteristic voltage response, from which various stack characteristics are extracted, allowing conclusions to be drawn about the state of the fuel cell system. After each charging process, an equilibrated starting state must be established again, which necessitates waiting times for equilibration before and during the measurement. Furthermore, the fuel cell stack may be briefly energized while unattended. Additionally, a processing unit must be woken up for measurement, or it may not be switched off, which minimizes the energy efficiency of the fuel cell system. Disclosure of the invention Within the scope of the presented invention, a method for diagnosing the condition of a fuel cell system and a fuel cell system are presented. Further features and details of the invention will become apparent from the respective dependent claims, the description, and the drawings. Features and details related to the R.415639 - 3 - methods according to the invention are described, of course also in connection with the fuel cell system according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, mutual reference is always made or can be made. The presented invention serves to provide a robust fuel cell system. Thus, according to a first aspect of the presented invention, a method for diagnosing the condition of a fuel cell system is presented. The presented method comprises starting the fuel cell system with the anode and cathode shut-off valves closed, opening the anode shut-off valves while the cathode shut-off valves remain closed, introducing fresh hydrogen into an anode compartment of a fuel cell stack of the fuel cell system while a cathode compartment of the fuel cell stack is closed, applying an electrical charging current to the fuel cell stack with a polarity reversed relative to subsequent normal operation, such that the voltage applied to the respective fuel cells of the fuel cell stack increases, determining a state of the fuel cell system based on a voltage profile at at least one fuel cell of the fuel cell stack and/or an anode pressure measured by at least one anode pressure sensor arranged on the anode compartment, opening the cathode shut-off valves, and outputting the state via an output interface. In the context of the presented invention, an output interface is understood to be an interface for providing information, such as a communication interface. To output the status, the output interface can include an output unit, such as a display. R.415639 - 4 - and/or transfer the state to a memory or provide the state to a control function for adjusting the fuel cell system. The presented method is performed during the start-up process of a fuel cell system and is based on a closed half-cell, namely a closed cathode subsystem or a closed cathode compartment. While the cathode compartment is closed, the other half-cell, namely the anode subsystem or the anode compartment, is flushed with fresh hydrogen. This configuration makes it possible to ut