Abstract:
Disclosed herein is a method of purging a fuel cell, by which water present in fuel cell stacks is discharged outside the fuel cell stacks together with gas by opening and closing a purge valve, including: conducting a short-period purge several times using the purge valve; and conducting a long-period purge once using the purge valve, wherein the short-period purge and the long-period purge are repeatedly conducted. The method of purging a fuel cell is advantageous in that the short-period purge is conducted several times using a purge valve and then the long-period purge is conducted once, and these short-period purges and the long-period purge are repeatedly conducted, so that the problems occurring when only a short-period purge or only a long-period purge is conducted can be solved, with the result that the efficiency and performance of the fuel cell are improved and the fuel cell can be stably operated.
Abstract:
A fuel cell separator, a fuel cell stack having the fuel cell separator, and a reactant gas control method of the fuel cell stack are provided. That is, even when the fuel cell stack operates under the low load operation condition, a reactant gas is supplied to the reactant gas passages of the fuel cell separator, and thus, the length of the passage can be shortened by 50% as compared with the prior art having only one reactant gas passage. Therefore, the reactant gas can be effectively supplied without experiencing pressure loss. Further, in the high load operation of the fuel cell stack, the reactant gas is introduced into the first reactant gas passage of the fuel cell separator and utilized in half of the whole electrode area. Subsequently, the reactant gas is introduced into the second reactant gas passage and utilized in the remaining half of the electrode area. The flow rate of the reactant gas flowing along the passage channels is increased by two times, even when the reactant gas utilizing rate is identical as compared with the reactant gas flow in the low load operation. As a result, the moisture existing in the passage channels can be more effectively discharged and the flooding phenomenon occurring in the high load operation can be prevented. By controlling the reactant gas supply in accordance with an operation condition of the fuel cell stack without experiencing pressure loss and deterioration of the utilizing rate, the flooding phenomenon and concentration polarization phenomenon that occur in the fuel cell stack can be prevented.
Abstract:
A glass substrate is provided with a durable and abrasion-resistant water-repellent surface, by coating a surface of the substrate with a silica solution which has been subjected to a two-step aging process, respectively in the presence of basic and acidic catalysts, which is then thermally treated to provide a coarse-surfaced silica layer including fine crystalline silica particles, which is then coated with a water-repellent layer made of fluoroalkylsilane.
Abstract:
A fuel cell separator, a fuel cell stack having the fuel cell separator, and a reactant gas control method of the fuel cell stack are provided. That is, even when the fuel cell stack operates under the low load operation condition, a reactant gas is supplied to the reactant gas passages of the fuel cell separator, and thus, the length of the passage can be shortened by 50% as compared with the prior art having only one reactant gas passage. Therefore, the reactant gas can be effectively supplied without experiencing pressure loss. Further, in the high load operation of the fuel cell stack, the reactant gas is introduced into the first reactant gas passage of the fuel cell separator and utilized in half of the whole electrode area. Subsequently, the reactant gas is introduced into the second reactant gas passage and utilized in the remaining half of the electrode area. The flow rate of the reactant gas flowing along the passage channels is increased by two times, even when the reactant gas utilizing rate is identical as compared with the reactant gas flow in the low load operation. As a result, the moisture existing in the passage channels can be more effectively discharged and the flooding phenomenon occurring in the high load operation can be prevented. By controlling the reactant gas supply in accordance with an operation condition of the fuel cell stack without experiencing pressure loss and deterioration of the utilizing rate, the flooding phenomenon and concentration polarization phenomenon that occur in the fuel cell stack can be prevented.
Abstract:
A lamellar structure graphite foil is used as a material for a separator for a fuel cell, and a hydrophobic layer is formed by impregnation on flow-field channels of the graphite foil. Such a separator is manufactured by forming the flow field channel by etching the graphite foil formed with the mask pattern thereon and forming a hydrophobic layer by impregnation. According to such a separator, performance of a fuel cell stack is enhanced and the manufacturing process of a separator is simplified.
Abstract:
The present invention relates to a Membrane Electrode Assembly (MEA) which significantly enhances power density as well as structural reliability and method for producing the same. More specifically, it relates to the Membrane Electrode Assembly which has a plurality of protuberances and method for producing the same. The present invention involves making supporting bodies to have a plurality of protuberances on one side of the supporting bodies, forming a catalyst layer on one side of the supporting bodies having the protuberances, interposing a polymer-electrolyte-membrane between the supporting bodies, aligning the supporting bodies for the protuberances to engage each other; and hot-pressing the aligned supporting bodies. The present invention can increase the area of a three-phase boundary in which oxidation-reduction reaction of hydrogen and oxygen occurs and decrease resistance to ion conduction; consequently fuel cells have the characteristic of a large output of power density.
Abstract:
A water-repellent glass comprising a uniform and optically transparent silica film with excellent durability and hardness is prepared by a process which comprises: (a) preparing a colloidal silica suspension by hydrolyzing and polycondensing an alkoxysilane in an organic solvent under a basic condition in the presence of water, and then treating the colloidal silica suspension under an acidic condition, to obtain a silica dispersion containing cross-linked spherical silica particles and linear polysiloxane, (b) combining the silica dispersion with a mixed solvent composed of acetic acid and an alcohol to obtain a coating composition, (c) applying the coating composition on the surface of a glass substrate to form a silica layer therefrom, (d) heat treating the silica layer to provide a silica film on the glass substrate, and (e) applying a water-repellent agent on the silica film to provide the water-repellent glass.
Abstract:
Disclosed is a cell voltage monitoring apparatus for monitoring output voltages of a plurality of unit cells in a cell having the unit cells. The cell voltage monitoring apparatus includes: a reference voltage generator for generating a predetermined reference voltage from the unit cell generation voltage; a voltage comparator for comparing a generation voltage of a monitor unit cell and the reference voltage; a signal separator for outputting a signal that is electrically separated from an output signal of the voltage comparator; and an operation processor for determining normality of the cell voltage from a signal output by the signal separator.
Abstract:
A water-repellent glass having a durable and abrasion-resistant silica layer is prepared by a process containing the following steps: (a) preparing a silica solution by subjecting a metal alkoxide-based silane compound to a two step aging process wherein the two step aging process is proceeded either by conducting a first aging step under a basic condition and a second aging step under an acidic condition or vice versa, (b) applying the resulting silica composition onto the surface of a glass substrate, (c) subjecting the glass substrate coated with the silica composition to a thermal treatment, and (d) coating the resulting coarse silica layer with a water-repellent layer.
Abstract:
The present invention relates to a sealing structure for polymer electrolyte fuel cell, which comprises a bipolar plate with sealing groove to be filled with rubber using a dispenser, and a gasket interposed between the bipolar plate and a membrane electrode assembly. That is, according to the present invention, the thickness deviation in a gasket can be softened by interposing a gasket between a rubber ands a membrane electrode assembly after filling rubber in a sealing groove formed on a bipolar plate using a dispenser. Also, nonuniform stress distribution can be resolved because a gasket covers with a pressure despite the height deviation of rubber, and a stress is not directly transmitted to a membrane electrode assembly and dispersed by a gasket despite nonuniform stress distribution.