A fuel cell system includes a fuel cell stack having a membrane electrode assembly and an internal reactant gas passage, a unit that detects or estimates an actual retained water quantity (R.W.Q.), and a power generation control unit having a normal-time mode, a normal-time drying mode and a stop-time drying mode. In the normal-time drying mode, the fuel cell stack is caused to generate electric power while being dried more than in the normal-time mode until the actual R.W.Q. is decreased to a target R.W.Q. In the stop-time drying mode, when the actual R.W.Q. is equal to or more than a flooding threshold at a time of detection of a system stop instruction, the fuel cell stack is caused to generate electric power while being dried more than in the normal-time drying mode until the actual R.W.Q. is decreased to a target R.W.Q.

A fuel cell system is disclosed, which includes an anode recirculation loop having a fuel cell stack for generating power, a flowmeter, a current sensor and a processor. The flowmeter is configured for measuring a fuel flow rate provided into the anode recirculation loop. The current sensor is configured for measuring a current drawn from the fuel cell stack. The processor is configured for determining a steam to carbon ratio in the anode recirculation loop based on the measured fuel flow rate and the measured current. The fuel cell system further includes a temperature sensor for measuring a temperature in the anode recirculation loop. The process is configured for determining the steam to carbon ration further based on the measured temperature. A method for operating the fuel cell system and a fuel cell power plant are also disclosed.

A method for performing one or more proactive remedial actions to prevent anode flow-field flooding in an anode side of a fuel cell stack at low stack current density. The method includes identifying one or more trigger conditions that could cause the anode flow-field to flood with water, and performing the one or more proactive remedial actions in response to the identified trigger conditions that removes water from the anode side flow-field prior to the anode flooding occurring.

A fuel cell system that generates electric power by supplying anode gas and cathode gas to a fuel cell includes a control valve adapted to control the pressure of the anode gas to be supplied to the fuel cell; a buffer unit adapted to store the anode-off gas to be discharged from the fuel cell; a pulsation operation unit adapted to control the control valve in order to periodically increase and decrease the pressure of the anode gas at a specific width of the pulsation; and a pulsation width correcting unit adapted to correct the width of the pulsation on the basis of the temperature of the buffer unit.

A hydrogen generation electricity system for producing electricity from hydrogen using a hydrogen carrier substance, comprising: a reaction chamber arranged for generating a H2 gas stream by converting the hydrogen carrier substance; wherein the reaction chamber comprises an inlet arranged for receiving the hydrogen carrier substance; an output conduit for exiting the H2 gas stream; a fuel cell arranged for producing electric energy by converting hydrogen; the output conduit is arranged for supplying the H2 gas stream from the reaction chamber to the fuel cell; the system further comprising: a humidity determining unit arranged for determining a humidity level of the H2 gas stream; a water providing means for providing H2O to the reaction chamber; and a water vapour control means arranged for controlling the water vapour level in the reaction chamber, in response to the determined humidity level, wherein the generated H2 gas stream comprises hydrogen and water vapour.

A method for controlling humidity in a fuel cell, wherein hydrogen is fed at a nominal pressure to the inlet of the cell, characterized in that at predetermined periodicity the following steps are repeated: instruction is given to open a hydrogen purge valve arranged on the outlet of the anode circuit; the pressure of hydrogen is measured at the inlet to the anode circuit of the cell, and the measured value is compared with a threshold pressure value; the purge valve is closed when the measured pressure is equal to or lower than the predetermined threshold pressure value; the opening time of the purge valve is measured; and the humidity level prevailing at the cathode of the cell is inferred therefrom.

A method for purging the hydrogen feed anode circuit of a fuel cell, whereby hydrogen is fed at a nominal pressure to the inlet of the cell, characterized in that at predetermined periodicity the following steps are repeated: instruction is given to open the hydrogen purge valve arranged on the outlet of the anode circuit; the pressure of hydrogen is measured at the inlet to the anode circuit of the cell, and the measured value is compared with a predetermined threshold pressure value; and the purge valve is closed when the measured pressure is equal to or lower than the predetermined threshold pressure value.

The fuel cell system determines whether or not condensation is occurring in the anode gas and the cathode gas on the basis of the humidity of the cathode gas detected by a first humidity sensor provided in the power generation cells and the humidity of the anode gas detected by a second humidity sensor provided in the power generation cells, and adjusts the water content in the cathode gas and/or the anode gas in which condensation is occurring.

A fuel cell system (200) for providing electrical energy. The system (200) comprises a fuel cell stack (201), an anode subsystem (203) with a proportional valve (205) for dosing a volume of gas to be fed to the fuel cell stack (201), a purge valve (207) for discharging gas from the anode subsystem (203) into an exhaust-gas path (209) of the fuel cell system (200), and a control unit (211) for controlling the proportional valve (205) and the purge valve (207). The control unit (211) is configured to use an electrical control current that is fed to the proportional valve (205) to readjust for a purging operation to draw conclusions regarding a hydrogen concentration in a gas that is fed to the purge valve (207), wherein the control unit (211) is furthermore configured to adjust the fuel cell system (200) in a manner dependent on the determined hydrogen concentration.

A voltage applying unit of a water detecting device applies, to a pair of electrodes, a voltage changing within an application range that includes a first voltage which is smaller than an electrolysis voltage of water and a second voltage which is larger than the electrolysis voltage of the water. A judging unit judges presence or absence of the water based on change in electric current measured by a current measuring unit when the voltage changing within the application range is applied to the pair of electrodes.