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.

A fuel cell system includes a fuel cell stack of a plurality of power generation cells and an impedance measuring device for measuring the impedance in the fuel cell stack. When stopping the operation of the fuel cell system, a method for stopping the operation of the fuel cell system operates the plurality of power generation cells to generate electric power, until the impedance value becomes equal to or greater than an objective impedance value. After the impedance value has become equal to or greater than the objective impedance value, the operation stopping method still continues the power generation of the multiple power generation cells for a given period of time.

In one or more embodiments of the novel aircraft fuel cell system without the use of a buffer battery, the fuel cell and compressor would be sized sufficiently larger for the intended application, allowing the compressor to change speeds much faster. This in turn would allow power outputs to change much quicker. If power outputs can change as quickly as the application dictates, then a buffer battery is not necessary. In one or more embodiments, because the system is mostly electronically controlled, software can be written to protect the fuel cell from instantaneous power spikes. If a large power output is suddenly requested of the fuel cell, the software can smooth out the demand curve to provide an easier load profile to follow.

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.

In one or more embodiments of the novel aircraft fuel cell system without the use of a buffer battery, the fuel cell and compressor would be sized sufficiently larger for the intended application, allowing the compressor to change speeds much faster. This in turn would allow power outputs to change much quicker. If power outputs can change as quickly as the application dictates, then a buffer battery is not necessary. In one or more embodiments, because the system is mostly electronically controlled, software can be written to protect the fuel cell from instantaneous power spikes. If a large power output is suddenly requested of the fuel cell, the software can smooth out the demand curve to provide an easier load profile to follow.

In a case where each of the temperature, the impedance, and the output current of a fuel cell stack falls within a predetermined range, the output voltage of the fuel cell stack is measured, and the measured output voltage is compared with a reference value to thereby determine the degree of degradation of the fuel cell stack.

Systems and methods for monitoring the isolation resistance of one or more fuel cells are described herein. In one example, a system includes a current transformer having a hollow core. First and second portions of a load line from a fuel cell are located within the hollow core. The first portion of the load line is electrically between an anode of a fuel cell and an electrical load, while the second portion of the load line being electrically between a cathode of the fuel cell and the electrical load. The current transformer is configured to output an electrical signal proportional to a current passing through the hollow core. This electrical signal can then be used to determine the isolation resistance of the fuel cell.

To provide a fuel cell system capable of evaluating degradation of an electrolyte membrane by quantifying metal ions involved in degradation of an electrolyte membrane instead of evaluating degradation of an electrolyte membrane itself. A fuel cell system comprising a fuel cell, a fuel gas system for supplying fuel gas to an anode of the fuel cell, an oxidant gas system for supplying oxidant gas to a cathode of the fuel cell, a voltage detector for detecting a voltage of the fuel cell, and a controller.

A fuel cell vehicle includes a high voltage apparatus for a fuel cell, a compressor for an air conditioner disposed under the high voltage apparatus for the fuel cell and constituting a module integrated with the high voltage apparatus for the fuel cell, and a power control unit separated from the high voltage apparatus for the fuel cell, disposed at a vehicle body over the compressor and configured to control an operation of a motor. The compressor and the high voltage apparatus for the fuel cell are connected by a single power wiring.