Diagnosis Method of Failure in PEMFC Using Magnetic Fields

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In recent years, fuel cell is emerging as clean energy sources with high energy efficiency. The proton exchange membrane fuel cell (PEMFC) is currently being used in various applications since they have the advantages of compact, lightweight, and relatively easy to start-up. PEMFCs have been developed to improve the output and efficiency in I-V performance. One of the challenges is to improve gas diffusion. To overcome the challenge, it requires the use of materials with suitable drainage properties and proper water management in the gas diffusion layer (GDL) and in the flow channels. Therefore, PEMFC diagnostic techniques are needed to detect flooding and plugging that affect performance and efficiency.However, it is difficult to diagnose generation failures due to flooding from parameters such as current, voltage, pressure and temperature measured in conventional systems. Therefore, in this study, we focused on the magnetic field of the PEMFC from generated current.In case there is not failure in power generation, it is assumed that magnetic field is not generated in the vertical direction from the cells’ surface, as current flows only in the vertical direction to the cells’ surface according to Ampere's law. However, when failure occurs due to the flooding, the current was diverted due to the defect. This means that the current in the direction parallel to the cells’ surface occurs, therefore, a magnetic field in the perpendicular direction is generated. This study aims to detect power generation inhibition due to flooding by comparing the magnetic fields during the normal and the failure operation.In this study, three types of cells were used for experiments: “normal cell”, “filled flow channels cell” to simulate flooding and plugging, and “hydrophilized cell” to enhance internal water retention of the GDL. The filled flow channels and the hydrophilized cell were operated for an hour under the same conditions as the normal cell to determine the changes in magnetic fields due to differences in internal conditions. During this experiment, 3-axis magnetic sensors was used for measuring magnetic fields in PEMFC. It was installed perpendicularly over the surface of the cathode-side for magnetic field measurement. Additionally, the current distribution was measured, and compared it with the magnetic field.The experimental results from this study showed that the magnetic field vectors on the cells’ surface, as observed from the anode side, exhibited clockwise rotation in three kinds of cells. This vector corresponds to the magnetic field obtained from Ampere's law concerning the macroscopic current direction of the cell. Furthermore, in the current distribution measurements, a bias in the current towards the gas upstream side of the normal cell and the cell with filled flow channels was observed. In the magnetic field measurements, the center of the rotation formed by the magnetic field vector was located on the gas upstream side, and similar results to the current distribution measurement were obtained. In comparing the magnetic fields of the cells, significant differences were found in both the parallel and vertical magnetic field comparison between the normal cell and filled flow channels or hydrophilized cell, compared to the changes in experimental conditions of the normal cell. These indicate that the magnetic field was changed by diverting currents due to filling the flow channels and water retention. Additionally, significant differences in the vertical magnetic fields on the cells’ surface at upper part of the cell were observed between the normal cell and filled flow channels or hydrophilized cell. Moreover, differences were also measured in the parts where the flow channels were filled in the cell. The result suggests that the potential for detecting power generation failures in cell with filled flow channels or hydrophilized cell.In this study, three different types of PEMFC cells were used to compare the magnetic fields generated from the current. The current was diverted due to filling the flow channels and water retention of water, which results in a significant difference in the vertical magnetic field generated. This indicates that power generation inhibition due to flooding can be detected from the vertical magnetic field.