Systems and methods are provided for using fuel cell staging to reduce or minimize variations in current density when operating molten carbonate fuel cells with elevated CO.sub.2 utilization. The fuel cell staging can mitigate the amount of alternative ion transport that occurs when operating molten carbonate fuel cells under conditions for elevated CO.sub.2 utilization.

When a time point of occurrence of a stop state of a fuel cell system is predicted during traveling, a drying state control that causes a fuel cell stack to transition to a dry state is started a predetermined time (a required drying time) before the predicted time point of occurrence of the stop state.

Systems and methods are provided for using fuel cell staging to reduce or minimize variations in current density when operating molten carbonate fuel cells with elevated CO.sub.2 utilization. The fuel cell staging can mitigate the amount of alternative ion transport that occurs when operating molten carbonate fuel cells under conditions for elevated CO.sub.2 utilization.

A method for controlling a fuel cell system includes supplying an oxidant gas, via an oxidant gas supply channel, to a cathode electrode of a fuel cell. The oxidant gas is moistened to be supplied to the cathode electrode with a humidifier. An opening degree of a bypass channel valve is decreased via a feedforward control to a first opening degree when an impedance has reached a lower limit value. The opening degree of the bypass channel valve is increased via the feedforward control to a second opening degree when the impedance has reached an upper limit value. The first opening degree is smaller than the second opening degree.

When a time point of occurrence of a stop state of a fuel cell system is predicted during traveling, a drying state control that causes a fuel cell stack to transition to a dry state is started a predetermined time (a required drying time) before the predicted time point of occurrence of the stop state.

The present disclosure provides a method and apparatus to perform an electrochemical process by manipulating the charge on an electrode involved in the primary circuit of the electrochemical reaction. The amount of charge on the electrode can be manipulated independent of the bias voltage of the primary circuit and is accomplished by coupling the electrode with various different configurations.

A redox flow battery which includes a battery cell to which a positive-electrode electrolyte and a negative-electrode electrolyte are supplied; a plurality of positive-electrode electrolyte tanks that store the positive-electrode electrolyte; a plurality of negative-electrode electrolyte tanks that store the negative-electrode electrolyte; a positive-electrode electrolyte tank switching device that switches a positive-electrode electrolyte tank among the plurality of positive electrolyte tanks; a negative-electrode electrolyte tank switching device that switches a negative-electrode electrolyte tank among the plurality of negative-electrode electrolyte tanks; a polarity switching unit that switches the polarity of the electrodes of the battery cells; and a controller for controlling switching the polarity of the electrodes, switching of the plurality of positive-electrode electrolyte tanks and switching of the plurality of negative-electrode electrolyte tanks. Also disclosed is a method for operating the redox flow battery.

A fuel cell system includes a controller configured to execute refreshing control for removing an oxide film on a catalyst during an operation of a fuel cell, and an impedance measurer configured to measure an impedance of the fuel cell during the operation of the fuel cell. The impedance measurer executes a calculation process for calculating the impedance by using measurement values of a current and a voltage of the fuel cell in a predetermined measurement time, and outputs a substitute value prepared in advance as the impedance when the start of the refreshing control during the measurement time is detected.

The present disclosure provides a method and apparatus to perform an electrochemical process by manipulating the charge on an electrode involved in the primary circuit of the electrochemical reaction. The amount of charge on the electrode can be manipulated independent of the bias voltage of the primary circuit and is accomplished by coupling the electrode with various different configurations.

A method for repairing a fuel cell stack having a plurality of individual cells involves the steps of: a) identifying at least one degraded individual cell in the fuel cell stack; and b) deactivating the at least one degraded individual cell.