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EP-4740255-A1 - SYSTEMS AND METHODS FOR PERFORMING PRESSURE FREQUENCY RESPONSE ANALYSIS IN TESTING OF ELECTROCHEMICAL DEVICES

EP4740255A1EP 4740255 A1EP4740255 A1EP 4740255A1EP-4740255-A1

Abstract

Systems and methods for diagnostic testing and operation of electrochemical devices using pressure perturbation techniques are provided. In some embodiments, the systems and methods can be used to conduct pressure frequency response analysis (pFRA), such as electrochemical pressure impedance spectroscopy (EPIS) or other techniques, on fuel cell assemblies. In addition to a primary reactant control valve used to control the supply of a reactant to the fuel cell, a secondary adjustable valve is located upstream of the fuel cell under test and downstream of the primary reactant control valve. The secondary adjustable valve can be adjusted so that pressure oscillations applied near the outlet of the fuel cell are also observed at the fuel cell inlet. This can make it possible to obtain reliable pFRA signals at the fuel cell inlet as well as at the outlet. The secondary adjustable valve can also be adjusted to control the linearity of the voltage response.

Inventors

  • NIROUMAND, AMIR MASOUD
  • ZHANG, QINGXIN
  • SCHNEIDER-COPPOLINO, Merissa
  • KULIKOVSKY, ANDREI
  • HOMAYOUNI, Hooman
  • GATES, Byron Daniel

Assignees

  • Greenlight Innovation Corporation

Dates

Publication Date
20260513
Application Date
20240704

Claims (20)

  1. 1. A method for testing a fuel cell assembly, the fuel cell assembly comprising a cathode-side having a cathode inlet and a cathode outlet, and an anode-side having an anode inlet and an anode outlet, the method comprising: while supplying an oxidant stream to the cathode inlet via a primary oxidant control valve, adjusting a secondary oxidant control valve located downstream of the primary oxidant control valve and upstream of the cathode inlet to a partially closed position; while operating the fuel cell assembly to supply electrical power to a load: applying pressure oscillations at or downstream of the cathode outlet over a range of frequencies; and measuring pressure-induced voltage oscillations across the fuel cell assembly if the fuel cell is operating at constant current, or measuring pressure-induced current oscillations in the fuel cell assembly if the fuel cell is operating at constant voltage.
  2. 2. The method of claim 1 wherein the step of adjusting the secondary oxidant control valve to a partially closed position comprises, prior to the applying pressure oscillations at or downstream of the cathode outlet over the range of frequencies and measuring the pressure-induced voltage oscillations or measuring the pressure-induced current oscillations: applying pressure oscillations at or downstream of the cathode outlet at a first frequency; measuring the amplitude of associated pressure oscillations at or upstream of the cathode inlet; and adjusting the secondary oxidant control valve to a first partially closed position so that the associated pressure oscillations at or upstream of the cathode inlet have a desired amplitude.
  3. 3. The method of claim 2 wherein the step of adjusting the secondary oxidant control valve to the first partially closed position so that the associated pressure oscillations at or upstream of the cathode inlet have a desired amplitude comprises adjusting the secondary oxidant control valve to the first partially closed position so that the associated pressure oscillations at or upstream of the cathode inlet are at least detectable.
  4. 4. The method of claim 2 further comprising comparing the amplitude of the pressure oscillations applied at or downstream of the cathode outlet at the first frequency with the amplitude of the associated pressure oscillations observed at or upstream of the cathode inlet; and wherein the step of adjusting the secondary oxidant control valve so that the associated pressure oscillations at or upstream of the cathode inlet have a desired amplitude comprises adjusting the secondary oxidant control valve to the first partially closed position so that the associated pressure oscillations observed at or upstream of the cathode inlet have the desired amplitude relative to the pressure oscillations applied downstream of the cathode outlet at the first frequency.
  5. 5. The method of claim 4 wherein the step of adjusting the secondary oxidant control valve to the first partially closed position so that the associated pressure oscillations observed at or upstream of the cathode inlet have the desired amplitude relative to the pressure oscillations applied downstream of the cathode outlet at the first frequency comprises adjusting the secondary oxidant control valve so that the amplitude of the associated pressure oscillations at or upstream of the cathode inlet is of the same order of magnitude as the amplitude of the pressure oscillations applied at or downstream of the cathode outlet.
  6. 6. The method of any of claims 2 to 5 wherein the first frequency is the highest frequency in the range of frequencies.
  7. 7. The method of any of claims 2 to 6 further comprising supplying fuel to the anode inlet while applying the pressure oscillations at or downstream of the cathode outlet at the first frequency and adjusting the secondary oxidant control valve to the first partially closed position.
  8. 8. The method of any of claims 2 to 7 further comprising operating the fuel cell assembly to supply electrical power to a load while applying pressure oscillations at or downstream of the cathode outlet at the first frequency and adjusting the secondary oxidant control valve to the first partially closed position.
  9. 9. The method of any of claims 2 to 8 wherein the method further comprises leaving the secondary oxidant control valve set at the first partially closed position while applying pressure oscillations at or downstream of the cathode outlet over the range of frequencies.
  10. 10. The method of any of claims 2 to 8 wherein the method further comprises further adjusting the secondary oxidant control valve while applying pressure oscillations at or downstream of the cathode outlet over the range of frequencies.
  11. 11. The method of claim 10 wherein the step of further adjusting the secondary oxidant control valve comprises further adjusting the secondary oxidant control valve based on the frequency of the pressure oscillations being applied.
  12. 12. The method of claim 10 wherein the step of further adjusting the secondary oxidant control valve comprises adjusting the secondary oxidant control valve to adjust the linearity of a pressure-induced voltage response.
  13. 13. The method of any of claims 1 to 12 wherein the step of applying pressure oscillations at or downstream of the cathode outlet comprises using a pressure control valve located at or downstream of the cathode outlet to apply the pressure oscillations.
  14. 14. The method of any of claims 1 to 13 wherein the fuel cell assembly is a single fuel cell.
  15. 15. The method of any of claims 1 to 13 wherein the fuel cell assembly is a fuel cell stack comprising a plurality of fuel cells, and the method comprising measuring pressure- induced voltage oscillations across each fuel cell in the fuel cell stack.
  16. 16. A fuel cell testing system for testing a fuel cell assembly comprising a cathode-side having a cathode inlet and a cathode outlet, and an anode-side having an anode inlet and an anode outlet, the system comprising: an oxidant supply subsystem for supplying oxidant to the cathode-side via the cathode inlet, the oxidant supply subsystem comprising a primary oxidant control valve located upstream of the cathode inlet; a cathode back pressure valve located at or downstream of the cathode outlet; a fuel supply subsystem for supplying a fuel stream to the anode-side via the anode inlet, the fuel supply subsystem comprising a primary fuel control valve located upstream of the cathode inlet; an anode back pressure valve located at or downstream of the anode outlet; a voltage monitoring subsystem for measuring the voltage across one or more fuel cells in the fuel cell assembly; an electrical load connectable to receive electrical power generated by the fuel cell assembly; and an adjustable secondary oxidant control valve located upstream of the cathode inlet and downstream of the primary oxidant control valve.
  17. 17. The fuel cell testing system of claim 16 further comprising a humidifier located upstream of the cathode inlet for humidifying the oxidant stream supplied to the cathode-side via the cathode inlet, where the primary oxidant control valve is located upstream of the humidifier and the adjustable secondary oxidant control valve is located downstream of the humidifier, between the humidifier and the cathode inlet.
  18. 18. The fuel cell testing system of any of claims 16 to 17 wherein during operation of the system, when the electrical load is connected and receiving electrical power generated by the fuel cell assembly and pressure oscillations are being applied at or downstream of the cathode outlet using the cathode back pressure valve, adjusting the adjustable secondary control valve changes the amplitude of the associated pressure oscillations at or upstream of the cathode inlet.
  19. 19. The fuel cell testing system of any of claims 16 to 17 wherein during operation of the system, when the electrical load is receiving electrical power generated by the fuel cell assembly and pressure oscillations are being applied at or downstream of the cathode outlet using the cathode back pressure valve, adjusting the adjustable secondary control valve changes the linearity of a pressure-induced voltage response measured using the voltage monitoring subsystem.
  20. 20. The fuel cell testing system of any of claims 16 to 19 wherein the adjustable secondary oxidant control valve is located directly upstream of the cathode inlet.

Description

SYSTEMS AND METHODS FOR PERFORMING PRESSURE FREQUENCY RESPONSE ANALYSIS IN TESTING OF ELECTROCHEMICAL DEVICES Cross-Reference to Related Applications [0001] This application is related to and claims priority benefits from U.S. Provisional Patent Application Serial No. 63/525,001 filed July 5, 2023, entitled “Systems and Methods for Performing Electrochemical Pressure Impedance Spectroscopy”. The ‘001 application is incorporated by reference herein in its entirety. Field of the Invention [0002] The present invention relates to apparatus, systems and methods for diagnostic testing and operation of electrochemical devices using pressure perturbation techniques. In particular, embodiments of the apparatus, systems and methods can be used to conduct pressure frequency response analysis (pFRA) methods, such as electrochemical pressure impedance spectroscopy (EPIS), on fuel cell assemblies. Background of the Invention [0003] Frequency response analysis (FRA) methods, such as electrochemical impedance spectroscopy (EIS), are powerful diagnostic techniques that can be used in testing of various electrochemical assemblies, including fuel cells and electrolyzers. Such methods can provide valuable insights into the electrochemical behavior, performance, and durability of these devices by separating the dynamic processes in the device under test (DUT) based on their response time. Note that in some FRA methods, an oscillation excitation is imposed, e.g. on the current, and the voltage response is measured. If the amplitude of the current excitation is large, it will typically result in harmonics in the voltage response due to DUT non-linearities. However, if the excitation is sufficiently small, the response does not exhibit higher harmonics and only contains the fundamental frequency. In this case, the DUT can be considered to be behaving in a linear manner, and the FRA response reduces to a single spectrum, such as EIS. [0004] Other methods that have been developed more recently, and that can be used in testing electrochemical assemblies such as fuel cells are pressure frequency response analysis (pFRA) methods, such as electrochemical pressure impedance spectroscopy (EPIS). These pFRA methods can combine the benefits of FRA and pressure measurements to further enhance the understanding and characterization of fuel cells. [0005] Such pFRA methods generally involve the measurement of impedance under varying pressure perturbations, and can provide information on electrode kinetics, mass transport, and other processes occurring within fuel cells. Use of pFRA can allow researchers and engineers to gain a deeper understanding of the fundamental electrochemical processes and mechanisms occurring within the fuel cell. An advantage of using pFRA is that it can be used to differentiate and analyze various components and processes that contribute to the overall impedance of a fuel cell. [0006] Typically, pFRA experiments involve applying pressure perturbations to a fuel cell at different frequencies and measuring the resulting voltage response or current response at a fixed current or potential, respectively. By varying the pressure frequency, an impedance spectrum can be obtained. The obtained data can then be analyzed using mathematical models and fitting algorithms to extract specific parameters and evaluate the performance of the fuel cell. [0007] This kind of testing and analysis may be particularly useful in fuel cell research and development, as it can provide valuable information regarding the effects of pressure on various fuel cell components, such as the catalyst layers, gas diffusion layers, membraneelectrode assemblies, and/or on flow field conditions. This knowledge can help researchers enhance or optimize the design and operation of fuel cells, leading to improved efficiency, durability, and performance. [0008] Furthermore, pFRA can be utilized for the diagnosis of fuel cell degradation and failure mechanisms. By monitoring changes in impedance under different pressure conditions over time, researchers can identify performance losses, catalyst degradation, or other issues affecting operation of a fuel cell. This diagnostic capability can facilitate proactive maintenance and enable the development of strategies to enhance fuel cell reliability and lifespan. Test methods involving pFRA can also be used in fuel cells to diagnose or provide information about operating conditions such as reactant flow conditions, humidity conditions, as well as liquid water condensation and accumulation. This can inform adjusting and optimizing fuel cell operating conditions to improve performance and durability of the fuel cell. Summary of the Invention [0009] In embodiments of a method for testing a fuel cell assembly, where the fuel cell assembly comprises a cathode-side having a cathode inlet and a cathode outlet, and an anodeside having an anode inlet and an anode outlet, the method comprises: [0010] while supplying an oxidan