Abstract: A fuel cell system and a method of controlling the fuel cell system are provided. The fuel cell system includes at least one bypass valve that is disposed between a passage in an inlet of a fuel cell stack and a bypass passage that is branched from the passage within the inlet and that is connected to a discharge port of the fuel cell stack. In addition, a controller bypasses air supplied from an air blower to the discharge port by adjusting an opening degree of the bypass valve.

Abstract: To diagnose a fault of a fuel cell stack, an alternating current having a first optimal frequency of a first frequency domain to diagnose a drop in cell voltage and an alternating current having a second optimal frequency of a second frequency domain to diagnose a cause of the drop in cell voltage are supplied to the fuel cell stack are provided. A distortion rate is then calculated based on voltage of the fuel cell stack according to the alternating current of the first optimal frequency, and the drop in cell voltage is diagnosed based on the calculated distortion rate. Also, impedance is calculated based on voltage and a current of the fuel cell stack according to the alternating current of the second optimal frequency and amount of water is calculated based on the calculated in the fuel cell stack, and the cause of the drop in cell voltage is diagnosed based on the calculated impedance and amount of water.

Abstract: A safety apparatus uses a fuel cell and a high voltage battery as a power source, and includes: a first voltage sensor that measures a voltage of a positive side of a voltage bus; a second voltage sensor that measures a voltage of a negative side of the voltage bus; and a controller that determines an electrical insulation between the positive side of the voltage bus and the electrical chassis based on the voltage of the positive side of the voltage bus and determines an electrical insulation between the negative side of the voltage bus and the electrical chassis based on the voltage of the negative side of the voltage bus.

Abstract: The present invention provides a manifold block for a fuel cell stack, coupled to a fuel cell stack module and having a gas passage and a cooling water passage. The manifold block includes an insulating member and an insulating cover. The insulating member is inserted into the cooling water passage and contacts an inner surface of the cooling water passage. The insulating member has a tube-like shape and electrically insulates the inner surface of the cooling water passage. The insulating cover is inserted into the cooling water passage and contacts an inner surface of the insulating member. The insulating cover fixes and protects the insulating member.

Abstract: Disclosed is an end plate for a fuel cell including an anti-bending plate, in which an anti-bending plate is assembled with an insert having a sandwich structure and the insert is injection molded, thereby easily preventing the insert from being bent due to an injection molding pressure. In the disclosed end plate, a sandwich insert including two or more stacked plates each having a specific shape is manufactured, and an anti-bending plate is coupled to the sandwich insert and then is injection molded, thereby easily preventing the sandwich insert from being bent due to a resin pressure in the injection molding process, contrary to a conventional integral metal insert.

Abstract: The present invention provides a method for manufacturing a composite separator for a polymer electrolyte membrane fuel cell. The method comprises: preparing a prepreg as a continuous carbon fiber-reinforced composite and a graphite foil; allowing the cut prepreg and graphite foil to pass through a stacking/compression roller to be compressed; allowing the prepreg in which the graphite foil is integrally stacked to be heated and pressed by a hot press such that hydrogen, air, and coolant flow fields are formed or to pass through a hot roller to be formed into a separator; removing unnecessary portions from the heated and pressed separator using a trim cutter; and post-curing the thus formed separator, wherein the graphite foil may be stacked on the prepreg as the continuous carbon fiber-reinforced composite such that a graphite layer is integrally formed with the prepreg.

Abstract: A system for activating a fuel cell includes a flow meter for measuring the amount of water discharged from an outlet of the air electrode and an outlet of the fuel electrode; a pressure sensor for measuring the pressure at the respective outlets; and a back pressure regulator receiving flow values measured by the flow meters and pressure values measured by the pressure sensors, which are fed back from a controller, and regulating a pressure difference (?P=PCathode?PAnode) to be a value greater than 0. With the system, the activation time of a fuel cell and the amount of hydrogen used for the activation can be reduced, thus improving the productivity and manufacturing cost.

Abstract: Disclosed are a safety system of a fuel cell vehicle and a control method for the safety system. A safety system of a fuel cell vehicle using a fuel cell and a high voltage battery as a power source may include: a power switch disposed on a power wire connecting the power source and a power load to each other; an insulation resistance measuring device measuring an insulation resistance between the power wire and a chassis; and a controller controlling an operation of the power switch based on a measured insulation resistance measured by the insulation resistance measuring device. When the measured insulation resistance is equal to or less than a reference resistance, the controller enters a safe mode and the power switch is turned off to thereby block power supplied to the power load.

Abstract: The present disclosure provides an end plate for a fuel cell including a sandwich insert, in which a metal insert has a sandwich insert structure including a plurality of stacked plates, thereby securing strength and achieving a lightweight structure. The sandwich insert is manufactured by staking two or more plates, each having a specific shape, followed by injection molding the sandwich insert with a plastic injection molded body, thereby securing strength and also achieving a lightweight structure, contrary to a conventional integral metal insert.

Abstract: A method for manufacturing a manifold for a fuel cell with a multilayer structure by injection-molding individual manifolds, each having welding projections and welding guides, and bonding the injection-molded individual manifolds by vibration welding includes arranging welding projections of an upper individual manifold and welding guides of a lower individual manifold to be engaged with each other while maintaining a uniform gap between each other to bond a plurality of individual manifolds in an up and down stacking structure, pressing the lower individual manifold upward, and applying vibration to the upper individual manifold in the left and right direction, thus bonding the upper and lower individual manifolds. Among the welding projections of the upper individual manifold, a non-horizontal welding projection whose longitudinal direction does not coincide with the vibration direction of the individual manifold has a variable height.

Abstract: The present invention provides a porous medium with increased hydrophobicity and a method of manufacturing the same, in which a micro-nano dual structure is provided by forming nanoprotrusions with a high aspect ratio by performing plasma etching on the surface of a porous medium with a micrometer-scale surface roughness and a hydrophobic thin film is deposited on the surface of the micro-nano dual structure, thus significantly increasing hydrophobicity. When this highly hydrophobic porous medium is used as a gas diffusion layer of a fuel cell, it is possible to efficiently discharge water produced during electrochemical reaction of the fuel cell, thus preventing flooding in the fuel cell. Moreover, it is possible to sufficiently supply reactant gases such as hydrogen and air (oxygen) to a membrane electrode assembly (MEA), thus improving the performance of the fuel cell.

Abstract: The present invention provides a composite separator for a polymer electrolyte membrane fuel cell (PEMFC) and a method for manufacturing the same, in which a graphite foil prepared by compressing expanded graphite is stacked on a carbon fiber-reinforced composite prepreg or a mixed solution prepared by mixing graphite flake and powder with a resin solvent is applied to the cured composite prepreg such that a graphite layer is integrally molded on the outermost end of the separator.

Abstract: Disclosed is a fuel cell with enhanced mass transfer characteristics in which a highly hydrophobic porous medium, which is prepared by forming a micro-nano dual structure in which nanometer-scale protrusions with a high aspect ratio are formed on the surface of a porous medium with a micrometer-scale roughness by plasma etching and then by depositing a hydrophobic thin film thereon, is used as a gas diffusion layer, thereby increasing hydrophobicity due to the micro-nano dual structure and the hydrophobic thin film. When this highly hydrophobic porous medium is used as a gas diffusion layer for a fuel cell, it is possible to reduce water flooding by efficiently discharging water produced by an electrochemical reaction of the fuel cell and to improve the performance of the fuel cell by facilitating the supply of reactant gases such as hydrogen and air (oxygen) to a membrane-electrode assembly (MEA).

Abstract: The present invention provides a fuel cell stack with enhanced freeze-thaw durability. In particular, the fuel cell stack includes a gas diffusion layer between a membrane-electrode assembly and a bipolar plate. The gas diffusion layer has a structure that reduces contact resistance in a fuel cell and is cut at a certain angle such that the machine direction (high stiffness direction) of GDL roll is not in parallel with the major flow field direction of the bipolar plate, resulting in an increased GDL stiffness in a width direction perpendicular to a major flow field direction of a bipolar plate.

Abstract: The present invention provides a composite separator for a polymer electrolyte membrane fuel cell (PEMFC) and a method for manufacturing the same, in which a graphite foil prepared by compressing expanded graphite is stacked on a carbon fiber-reinforced composite prepreg or a mixed solution prepared by mixing graphite flake and powder with a resin solvent is applied to the cured composite prepreg such that a graphite layer is integrally molded on the outermost end of the separator.

Abstract: Disclosed is a fuel cell with enhanced mass transfer characteristics in which a highly hydrophobic porous medium, which is prepared by forming a micro-nano dual structure in which nanometer-scale protrusions with a high aspect ratio are formed on the surface of a porous medium with a micrometer-scale roughness by plasma etching and then by depositing a hydrophobic thin film thereon, is used as a gas diffusion layer, thereby increasing hydrophobicity due to the micro-nano dual structure and the hydrophobic thin film. When this highly hydrophobic porous medium is used as a gas diffusion layer for a fuel cell, it is possible to reduce water flooding by efficiently discharging water produced by an electrochemical reaction of the fuel cell and to improve the performance of the fuel cell by facilitating the supply of reactant gases such as hydrogen and air (oxygen) to a membrane-electrode assembly (MEA).

Abstract: The present invention provides a porous medium with increased hydrophobicity and a method of manufacturing the same, in which a micro-nano dual structure is provided by forming nanoprotrusions with a high aspect ratio by performing plasma etching on the surface of a porous medium with a micrometer-scale surface roughness and a hydrophobic thin film is deposited on the surface of the micro-nano dual structure, thus significantly increasing hydrophobicity. When this highly hydrophobic porous medium is used as a gas diffusion layer of a fuel cell, it is possible to efficiently discharge water produced during electrochemical reaction of the fuel cell, thus preventing flooding in the fuel cell. Moreover, it is possible to sufficiently supply reactant gases such as hydrogen and air (oxygen) to a membrane electrode assembly (MEA), thus improving the performance of the fuel cell.

Abstract: The present invention provides an apparatus and method for manufacturing a metal separator for a fuel cell, which can manufacture large-sized metal separators in large quantities using metal plates such as stainless steel by thermoplastic deformation using an incremental and synchronized rubber molding process.

Abstract: The present invention provides a fuel cell separator with a gasket and a method for manufacturing the same, which can prevent corrosion of the separator and improve corrosion resistance of the separator. In particular, the present invention provides a fuel cell separator with a gasket and a method for manufacturing the same, in which an adhesive is coated on the entire or partial surface of the separator, preferably by screen printing. A process of integrally molding a gasket to the separator is then performed such that the edges of the separator are not exposed to the outside after the injection molding process but, rather, are coated with the resin adhesive. The present invention thereby prevents corrosion of the separator, improves corrosion resistance of the separator, and prevents formation of burrs during the injection molding process.

Abstract: A technique is described herein for monitoring the operational state of a fuel cell stack by the detection of nonlinearity in such a manner that an external test signal for frequency response is generated and applied to the fuel cell stack during operation, the resulting signal output from the fuel cell stack is measured, and the harmonic content of the measured signal is analyzed, the method including: applying a multiple frequency test signal comprising at least two sinusoidal waves as the test signal for frequency response to the fuel cell stack; and analyzing the resulting current or voltage signal output from the fuel cell stack.