The invention relates to a method for operating a fuel cell system (1), in particular a PEM fuel cell system, in which at least one fuel cell (2) is supplied with a hydrogen-containing anode gas via an anode gas path (3) and anode gas exiting the fuel cell (2) is returned via a recirculation path (4), wherein, in order to reduce a nitrogen content in the anode gas, a flush valve (5) arranged in the recirculation path (4) is opened and the recirculation path (4) is flushed. According to the invention, the actual composition of the anode gas is determined using at least one sensor (6) and the ageing status of the at least one fuel cell (2) is determined by comparing the determined actual composition with a target composition and/or an actual composition determined earlier. The invention also relates to a control device (7) for carrying out the method according to the invention.

A gas sensor comprises a substrate, a first semiconductor-based sensor element for determining the density and/or viscosity of a gas, which element is arranged above the substrate and which has a resonant element, and a cover arranged above the first sensor element, wherein the substrate and/or the cover has an opening to allow the passage of a gas to the first sensor element.

A method for controlling a carbon dioxide utilization in a fuel cell assembly includes: measuring a voltage across the fuel cell assembly; determining an estimated carbon dioxide utilization of the fuel cell assembly based on at least the measured voltage across the fuel cell assembly by determining an expected voltage of the fuel cell assembly based on at least a temperature of the fuel cell assembly, a current density across the fuel cell assembly, a fuel utilization of the fuel cell assembly, and a cathode oxygen utilization of the fuel cell assembly; determining the estimated carbon dioxide utilization based on a comparison between the measured voltage and the determined expected voltage; comparing the determined estimated carbon dioxide utilization to a predetermined threshold utilization; and upon determining that the determined estimated carbon dioxide utilization is higher than the predetermined threshold utilization, reducing the carbon utilization of the fuel cell assembly.

A device for controlling compensation for an air flow rate upon discharge of hydrogen off-gas and a method for controlling compensation for an air flow rate using the same is an air flow rate control device configured to control a flow rate of air supplied to a fuel cell cathode through an air supply unit of a fuel cell system, wherein the air flow rate control device is configured to determine whether a fuel discharge valve of the fuel cell system is opened and determine a fuel diffusion amount per unit time, wherein the fuel diffusion amount corresponds to an amount of the hydrogen off-gas discharged through the fuel discharge valve and diffused into an air supply unit through a humidifier, and compensate a target air flow rate depending on an oxygen concentration reduction proportion, determined according to the determined fuel diffusion amount per unit time and flow rate information of the air supply unit.

Disclosed is a unitized regenerative fuel cell system, comprised of a unitized regenerative fuel cell able to operate in a fuel cell mode for electric power generation and in a water electrolysis mode for hydrogen and oxygen production, and a plurality of fire-detecting sensors for detecting fire in each zone of a tunnel, and configured to supply oxygen to zones wherein fire has not occurred if occurrence of fire has been detected in a tunnel, and a method for controlling the same.

Disclosed is a unitized regenerative fuel cell system, comprised of a unitized regenerative fuel cell able to operate in a fuel cell mode for electric power generation and in a water electrolysis mode for hydrogen and oxygen production, and a plurality of fire-detecting sensors for detecting fire in each zone of a tunnel, and configured to supply oxygen to zones wherein fire has not occurred if occurrence of fire has been detected in a tunnel, and a method for controlling the same.

In accordance with the principles of the present invention, a system and method for the management of the power applied to electrolytic cell is provided. The power management consists a constant current regulation, H-bridge control by pulse width modulation (PWM), and dimming control of the applied current to the electrolytic cell. The constant current regulation is an analog control that maintains the applied current at a user-defined current setpoint. The time scale of constant current regulation ranges from tenth of microseconds to milliseconds. The PWM control of the H-bridge allows for the instant adjustment of the electrolytic production output by turning the cell on and off; the time scale of the PWM control ranges from tenths of milliseconds to seconds. The dimming control allows the change of the applied constant current; the time scale of the dimming control ranges from milliseconds to hours and longer.

The invention relates to a fuel cell system (100) with at least one fuel cell (90), each fuel cell (90) having a cathode inlet (92), and with a housing (50) in which the at least one fuel cell (90) is arranged, the housing (50) having at least one ventilation inlet (52) through which at least one ventilation fluid flows in and at least one outflow outlet (54) through which at least one outflow fluid flows out. The fuel cell system (100) further comprises a supply line (14) to the at least one cathode inlet (92) for providing a supply fluid from a first fluid source to the at least one cathode inlet (14), and a compressor (16) in the supply line (14) for compressing the supply fluid. The fuel cell system (100) also comprises a fluidly communicating ventilation line (24) between the supply line (14) and the at least one ventilation inlet (52) for connecting the supply line (14) to the at least one ventilation line (52), the fluidly communicating ventilation line (24) being connected to the supply line (14) between the compressor (16) and the at least one cathode inlet (92), and/or a compressor cooling line (32) for cooling the compressor (16) and a fluidly communicating compressor ventilation line (34) between the compressor cooling line (32) and the at least one ventilation inlet (52) for connecting the compressor cooling line (32) to the at least one ventilation inlet (52).

The present invention provides, in a first aspect, an electrical generation system which includes an electrolyzer and a fuel cell system. The electrolyzer is coupled to a source of water and a power source. The electrolyzer is configured to generate oxygen and hydrogen utilizing water from the water source and electrical power from the power source. The fuel cell system is coupled to the electrolyzer to receive a flow of the hydrogen from the electrolyzer at an anode thereof. The fuel cell system includes a cathode having a cathode chamber coupled to a source of ambient air. The cathode chamber is coupled to the electrolyzer to selectively allow a flow of the oxygen from the electrolyzer to the cathode chamber and to selectively allow a flow of air from the source of ambient air to the cathode chamber. The fuel cell system is configured to generate electricity in a fuel cell reaction utilizing the hydrogen and the oxygen.

A method of controlling a fuel cell device includes: a step of determining whether impedance between a fuel electrode and an oxidant electrode is greater than a predetermined threshold during a steady operation of the fuel cell device; a step of decreasing a flow rate of a gas circulating via a circulation passage connecting a gas introduction passage of the gas supply unit to a gas discharge passage when the impedance is greater than the predetermined threshold; a step of measuring the voltage between the fuel electrode and the oxidant electrode when the impedance is equal to or less than the predetermined threshold, and determining whether the voltage is equal to or less than a first predetermined threshold; and a step of increasing the flow rate of the gas circulating via the circulation passage when the voltage is equal to or less than the first predetermined threshold.