Abstract: A fuel cell system is disclosed. The fuel cell system has at least one fuel cell stack which is arranged in a housing. The housing has at least one ventilation connection to the surroundings or to another volume. The ventilation connection has a valve device.

Abstract: The invention relates to a method for operating a PEM or DMFC fuel cell in the minimal- or partial-load region. According to the invention, the size of the cell surface, on which the fuel cell reaction takes place, is altered by means of opening or closing of feed channels, which serve to supply reaction medium to the cell surface.

Abstract: A self-healing membrane, especially for using in PEM fuel cells. The membrane comprises at least one porous material which is not ion-conductive and at least one polymer, ion-conductive electrolyte which has a higher melting point or decomposition point that the porous material which is not ion-conductive. If a hole, crack or the like forms in the membrane, the porous material which is not ion-conductive melts due to the temperature rise occurring at the leaking point, before the polymer, ion-conductive electrolyte melts or decomposes and seals the membrane at this point. The inventive membrane heals occurring defects itself in this way, and is thus self-healing.

Abstract: The performance of a direct feed fuel cell such as, for example, a direct methanol fuel cell, with an anode having a CO-tolerant catalyst, such as a Pt—Ru catalyst, is improved by periodically reducing the output power of the cell to be less than the normal minimum output of the cell. This is effected, for example, by switching the cell at predetermined time intervals to an open circuit or reduced output power condition.

Abstract: The invention relates to a method for operating a PEM or DMFC fuel cell in the minimal- or partial-load region. According to the invention, the size of the cell surface, on which the fuel cell reaction takes place, is altered by means of opening or closing of feed channels, which serve to supply reaction medium to the cell surface.

Abstract: The invention relates to a fuel cell stack, comprising alternately arranged membrane-electrode units (3) and separator plates (2, 2a) for the introduction and removal of the reactant and oxidative fluid, whereby the separator plate (2, 2a) has a surface structure and the opposing face has the negative surface structure, by means of a shaping process. According to the invention, on stacking the separator plates (2, 2a), the surface structure of a separator plate (2) is opposite the corresponding negative surface structure of the neighboring separator plate (2a).

Abstract: The performance of a direct feed fuel cell such as, for example, a direct methanol fuel cell, with an anode having a CO-tolerant catalyst, such as a Pt-Ru catalyst, is improved by periodically reducing the output power of the cell to be less than the normal minimum output of the cell. This is effected, for example, by switching the cell at predetermined time intervals to an open circuit or reduced output power condition.

Abstract: An electrochemical cell stack has alternately arranged membrane electrode assemblies (12) and separator plates (11) having channel regions (13) via which the reactant or oxidant fluids are supplied to and removed from the membrane electrode assembly (12), the separator plates (11), on one side, having a surface structure of channels (15) and ridges (14) located therebetween and, on the other side, having a surface structure which is negative with respect thereto.

Abstract: The present invention relates to improving the overall efficiency of a fuel cell system by reducing parasitic power consumption. A controller is programmed to decrease oxidant stoichiometry until oxidant starvation is detected or until oxidant stoichiometry is about one. When oxidant starvation is detected, the oxidant stoichiometry is increased until oxidant starvation is no longer detected. The fuel cell system employs a sensor for detecting an operational characteristic such as voltage output, or oxygen or hydrogen concentration in the cathode exhaust stream. The controller uses the operational characteristic to calculate oxidant stoichiometry or to determine when there is oxidant starvation at the cathode.

Abstract: A method and apparatus are provided for starting and operating an electric power generation system comprising an electrochemical fuel cell stack for supplying electric current to an external electrical circuit. The stack comprises at least one fuel cell comprising a membrane electrode assembly comprising an anode, a cathode, and a water permeable ion exchange membrane interposed between the anode and the cathode. A fuel stream and an oxidant stream are each flowable to the fuel cell. At least a portion of the membrane electrode assembly has a temperature below the freezing temperature of water. The supply of electric current to the external circuit from the fuel cell stack is commenced such that the temperature of the membrane electrode assembly exceeds the freezing temperature of water.