A method for diagnosing a state of a fuel cell stack as being contaminated includes measuring an impedance of a fuel cell stack at a predetermined low frequency and a predetermined high frequency, increasing an amount of fuel or oxidizer supplied to the fuel cell stack when the impedance at the predetermined high frequency is lower than a first critical point and the impedance at the predetermined low frequency is higher than a second critical point, remeasuring the impedance of the fuel cell stack at the predetermined low frequency, and determining that the fuel cell stack is contaminated when the impedance at the predetermined low frequency that is measured in the remeasuring step is higher than the second critical point.

Disclosed is a heat exchange apparatus for cooling water of a fuel cell, the heat exchange apparatus including a body, through which a cooling water pipe, through which cooling water that is to be supplied to a fuel cell stack flows, passes, and a heat accumulator provided in the interior of the body and filled with a PCM heat accumulation material that is to exchange heat with the cooling water. The body includes a medium space provided between the cooling water pipe and the heat accumulator and filled with a medium material. The PCM heat accumulation material exchanges heat with the cooling water by the medium material.

A method for controlling a fuel cell vehicle includes acquiring a state data, deriving a mathematical voltage model by substituting the acquired state data into a voltage calculation formula, measuring a voltage of a fuel cell, approximating a mathematical voltage model to a measurement voltage and deriving the reaction area data when the mathematical voltage model approximates the measurement voltage, and controlling the system of the fuel cell vehicle based on the derived reaction area data to eliminate or prevent an over-humidification situation of the fuel cell.

A fuel cell system operates under at least one of the conditions of no humidity or high temperature, and an operating method thereof, are characterized in that a fuel cell has a fuel gas flow path and an oxidant gas flow path arranged such that fuel gas and oxidant gas flow in opposite directions, a determining apparatus that determines the amount of water near the oxidant gas flow path inlet, and a fuel gas control apparatus which increases the amount of water near the oxidant gas flow path inlet by increasing the fuel gas flowrate and/or reducing the fuel gas pressure if it is determined in the determining apparatus that the amount of water near the oxidant gas flow path inlet is insufficient.

A technique of diagnosing a fuel cell stack is provided. In particular, current and voltage of a fuel cell stack are measured during driving of a fuel cell vehicle and the current and voltage are sequentially stored. It is then determined based on the stored current whether the vehicle is being operated at constant current. Different factors are analyzed depending on whether the vehicle is being operated at constant current, and then it is determined whether the fuel cell stack is in a normal state. A moisture supply into the fuel cell stack is calculated if it is determined that the fuel cell stack is not in the normal state. Based on the calculated moisture supply, whether the fuel cell stack is in a dryout state is diagnosed.

An object is to provide a technique of enhancing the accuracy of estimation of the water content of a fuel cell on the occurrence of localized drying of an electrolyte membrane. In a fuel cell system, until satisfaction of a second condition indicating that localized drying of the electrolyte membrane is eliminated after satisfaction of a first condition indicating that localized drying of the electrolyte membrane occurs, a water content estimator performs a second water content estimation process that estimates the water content of the fuel cell based on an output current value of the fuel cell, in place of a first water content estimation process that estimates the water content of the fuel cell based on an impedance of the fuel cell. The first condition is that an oxidizing gas stoichiometric ratio is equal to or higher than a predetermined reference value and that a first elapsed time has elapsed since the oxidizing gas stoichiometric ratio becomes equal to or higher than the predetermined reference value. The second condition is that an accumulated current value by accumulation of the output current value for a second elapsed time since satisfaction of the first condition is equal to or greater than a reference value of accumulated current value or that the oxidizing gas stoichiometric ratio is lower than the predetermined reference value and that a third elapsed time has elapsed since the oxidizing gas stoichiometric ratio becomes lower than the predetermined reference value.

A state determination device for a fuel cell for generating power upon receiving the supply of anode gas and cathode gas, comprising: an internal impedance measurement unit configured to measure an internal impedance of the fuel cell on the basis of an alternating-current signal of a predetermined frequency output from the fuel cell; and an anode reaction resistance estimation/calculation unit configured to calculate an estimation value of a reaction resistance of an anode electrode of the fuel cell on the basis of a measurement value of the internal impedance, wherein: the predetermined frequency is selected such that a difference between the estimation value of the reaction resistance of the anode electrode during hydrogen starvation and the estimation value of the reaction resistance of the anode electrode during oxygen starvation is not smaller than a predetermined value.

A state detection device for fuel cell includes a supposed high-frequency impedance value setting unit configured to set a supposed high-frequency impedance value on the basis of an impedance measurement value belonging to an arc region of an impedance curve of the fuel cell, an actually measured high-frequency impedance value calculation unit configured to obtain an actually measured high-frequency impedance value on the basis of an impedance measurement value belonging to a non-arc region of the impedance curve of the fuel cell, and an ionomer resistance estimation unit configured to estimate a value obtained by subtracting the actually measured high-frequency impedance value from the supposed high-frequency impedance value as an ionomer resistance value. The supposed high-frequency impedance value setting unit sets a value of an intersection of an equivalent circuit impedance curve set on the basis of the impedance measurement value belonging to the arc region and a real ads as the supposed high-frequency impedance value.

A fuel cell internal state detection system includes estimation object state quantity setting unit for setting a suitable estimation object state quantity as an index of an internal state, an impedance value acquisition unit configured to obtain an impedance value of a fuel cell, an impedance usability judging unit configured to judge whether or not the obtained impedance value is usable for the calculation of the estimation object state quantity, estimation object state quantity calculation unit for calculating the estimation object state quantity set by the estimation object state quantity setting unit on the basis of the obtained impedance value when the impedance value is judged to be usable for the calculation of the estimation object state quantity by the impedance usability judging unit, and an unusable-scene process execution unit configured to perform an unusable-scene process when the impedance value is judged not to be usable for the calculation of the estimation object state quantity by the impedance usability judging unit.

A fuel cell system includes a fuel supply unit that supplies a fuel to electrolyte membrane of fuel cell, an oxidant supply unit that supplies an oxidant to the electrolyte membrane, and an electricity generation control unit that controls electricity generation by the fuel cell by controlling supply of the oxidant by the oxidant supply unit and supply of the fuel by the fuel supply unit. the fuel cell system includes a wet/dry state detection unit configured to detect a wet/dry state of the electrolyte membrane, a flow rate adjustment unit configured to adjust a flow rate of the fuel supplied to the fuel cell by the fuel supply unit; and a temperature adjustment unit configured to adjust a temperature of the oxidant supplied to the fuel cell by the oxidant supply unit. when reducing an amount of water in the electrolyte membrane in accordance with a signal output from the wet/dry state detection unit, the electricity generation control unit is configured to reduce the flow rate of the fuel, and increase the temperature of the oxidant in accordance with the signal from the wet/dry state detection unit, compared with when increasing the amount of water in the electrolyte membrane.