An illustrative example system for managing hydrogen utilization in a fuel cell power plant includes a first hydrogen concentration sensor that provides an indication of a first concentration of hydrogen in a fluid flowing into an anode inlet of the power plant. A second hydrogen concentration sensor provides an indication of a second concentration of hydrogen in a fluid flowing out of an anode exit of the power plant. A processor determines a utilization of hydrogen by the power plant based on the first and second concentrations.

A method increases the safety and/or the reliability of the operation of a fuel cell stack. The method determines that the fuel cell stack is in a space with a reduced air exchange rate. The method determines consumption information with respect to an oxygen consumption of the fuel cell stack within an interval of time. The method determines, on the basis of the air exchange rate, inflow information with respect to an amount of oxygen which was supplied to the space within the interval of time. The method determines an estimated value for an oxygen content of air in the space on the basis of the consumption information and on the basis of the inflow information.

A control unit estimates a discharged fuel gas amount, i.e., an amount of fuel gas discharged from the outlet of a cathode flow field, of a fuel exhaust gas introduced from a communication flow path to the inlet of the cathode flow field and then flowing through a cathode. The control unit calculates an oxygen-containing gas amount necessary for dilution at the time of discharge into the atmosphere, from the estimated discharged fuel gas amount, and sets a discharge amount of the air pump, based on the calculated oxygen-containing gas amount.

Fuel cell systems configured for efficient byproduct recovery and reuse are disclosed herein. In one embodiment, a fuel cell system includes a reformer configured to reform a fuel containing methane (CH.sub.4) with steam to produce a reformed fuel having methane (CH.sub.4), carbon monoxide (CO), and hydrogen (H.sub.2). The fuel cell system also includes a fuel cell configured to perform an electrochemical reaction between a first portion of the reformed fuel and oxygen (O.sub.2) to produce electricity and an exhaust having carbon dioxide (CO.sub.2), water (H.sub.2O), and a second portion of the reformed fuel. The fuel cell system further includes an oxygen enricher configured to generate an oxygen enriched gas and a combustion chamber configured to combust the second portion of the reformed fuel with the oxygen enriched gas.

Disclosed are a gas sampling system and a gas sampling method for a fuel cell, a current density distribution estimation method for the fuel cell, a calibration method and a calibration device for an internal state model for the fuel cell, and a computer equipment. The gas sampling method for a fuel cell includes arranging a plurality of sampling pipelines and a plurality of sampling points, the plurality of sampling points being arranged at a cathode inlet, an anode outlet, an anode inlet, a cathode outlet, and in an anode flow channel, and a cathode flow channel of the fuel cell, the sampling points arranged in the anode flow channel and the cathode flow channel being located in central regions of cross sections of the flow channels, and the sampling pipelines being connected to the plurality of sampling points, respectively, and configured to guide gas inside the fuel cell out.

A fuel cell system includes a controller which controls operations of an oxidizing gas supply/discharge system and a fuel gas supply/discharge system, and controls power generation of a fuel cell stack, and, when detecting a fuel gas concentration abnormality that a fuel gas concentration in an exhaust gas exceeds an allowable value during the power generation of the fuel cell stack, the controller increases a flow rate of air fed by an air compressor, and controls an opening of a bypass valve to execute exhaust gas dilution control for increasing a ratio of the flow rate of the air flowing out from the bypass piping to an exhaust gas piping with respect to the flow rate of the air to be supplied to the fuel cell stack.

A fuel cell system includes a fuel cell in which cells are stacked, a voltage sensor that detects a voltage in unit of one or more of the cells, a control unit that determines an operating point of the fuel cell and causes the fuel cell to operate. The control unit causes the fuel cell to operate at a low efficiency operating point having a lower efficiency than an efficiency of a reference operating point in a warm-up operation. In the warm-up operation, the control unit calculates a total number of the cells in which the voltage detected by the voltage sensor is equal to or less than a predetermined first reference voltage and calculates an exhaust hydrogen concentration based on the total number or the cells.

A method for treating hydrogen-containing and oxygen-containing residual gases of fuel cells, wherein the residual gases are fed to a gas circuit, and a residual gas mixture resulting therefrom is circulated in the gas circuit by a device for converting hydrogen and oxygen to water. In order to reduce the amount of hydrogen and oxygen in the residual gas mixture, at least part of the residual gas mixture is discharged from the gas circuit.

A system for capturing carbon dioxide in flue gas includes a fuel cell assembly including at least one fuel cell including a cathode portion configured to receive, as cathode inlet gas, the flue gas generated by the flue gas generating device or a derivative thereof, and to output cathode exhaust gas and an anode portion configure to receive an anode inlet gas and to output anode exhaust gas, a fuel cell assembly voltage monitor configured to measure a voltage across the fuel cell assembly, and a controller configured to receive the measured voltage across the fuel cell assembly from the fuel cell assembly voltage monitor, determine an estimated carbon dioxide utilization of the fuel cell assembly based on the measured voltage across the fuel cell assembly, and reduce the carbon dioxide utilization of the fuel cell assembly when the determined estimated carbon dioxide utilization is above a predetermined threshold utilization.

A fuel cell system and a method for purge and removing water during its stop and start process, the system comprises a fuel cell stack, an air supply system connected to a cathode at a cathode side of the fuel cell stack, and a hydrogen supply system connected to an anode at an anode side of the fuel cell stack, the air supply system includes an air compressor, an air inlet tube, and an air outlet tube, the air outlet tube is connected to a low-oxygen gas storage tank through a manifold, and the low-oxygen gas storage tank is connected back to the hydrogen supply system through a circulating tube. The method expels standing water from the fuel cell stack using an air compressor to continuously supply air to both the anode side and the cathode side of the fuel cell stack, so as to further protect the stack.