A reforming element for a molten carbonate fuel cell stack and corresponding methods are provided that can reduce or minimize temperature differences within the fuel cell stack when operating the fuel cell stack with enhanced CO.sub.2 utilization. The reforming element can include at least one surface with a reforming catalyst deposited on the surface. A difference between the minimum and maximum reforming catalyst density and/or activity on a first portion of the at least one surface can be 20% to 75%, with the highest catalyst densities and/or activities being in proximity to the side of the fuel cell stack corresponding to at least one of the anode inlet and the cathode inlet.

The invention relates to a fuel cell system (2) with at least one fuel cell stack (19), which comprises an anode chamber (20) and a cathode chamber (21), with at least one air conveying device (3) for the supply of the cathode chamber (21) with air via a feed air line (22), with an outlet air line (23) from the cathode chamber (21), with at least one fuel supply device (26) for the supply of the anode chamber (20) with fuel, with at least one anode circuit (28) for the recirculation of unused fuel around the anode chamber (20), furthermore with a cathode bypass (37). The fuel cell system according to the invention is characterized in that the cathode bypass line (37) branches off from the feed air line (22) upstream of or in the region of a valve device (35) in said feed air line (22), and opens into the outlet air line downstream of or in the region of a further valve device (36) in said outlet air line (23), wherein a gas jet pump (38) which can be driven by the air which flows around the cathode chamber (21) is arranged in the cathode bypass (37), which gas jet pump (38) is connected switchably on the suction side to the anode chamber (20) and/or the cathode chamber (21).

Methods of determining concentrations and/or amounts of redox-active elements at each valence state in an electrolyte solution of a redox flow battery are provided. Once determined, the concentrations and/or amounts of the redox-active elements at each valence state can be used to determine side-reactions, make chemical adjustments, periodically monitor battery capacity, adjust performance, or to otherwise determine a baseline concentration of the redox-active ions for any purpose.

A method for starting a fuel cell in a fuel cell system, at temperatures below the freezing point of water, includes, in a first step, that the hydrogen concentration in the anode is increased; after which, in a second step, an anode pressure is increased for a fixed period of time, and while air is supplied to the cathode, the maximum possible current is drawn from the fuel cell, and after which, in a third step, the fuel cell is switched in a load-free manner and the anode pressure is reduced. After the third step, the second step and the third step are repeated successively until a sufficient performance of the fuel cell for its normal operation is reached.

The invention relates to a method for switching off a fuel cell system (100) having a fuel cell stack (10), that has anode chambers (13) and cathode chambers (12), and a cathode supply (20) having a cathode supply path (21) for supplying an oxygenated cathode operating gas into the cathode chambers (12), a compressor (23) arranged in the cathode supply path(21) and a cathode exhaust path (22) for discharging a cathode exhaust gas from the cathode chambers (12).

The method comprises the steps of:

(a) Maintenance of the cathode chambers (12) under excess pressure while preventing a flow of cathode operating gas through the cathode chambers (12) while keeping the cathode operating gas that is present in the cathode chambers (12) oxygen-depleted;

(b) Expansion of the oxygen-depleted cathode operating gas present in the cathode chambers (12) via the cathode supply path (31) [sic] and/or the cathode exhaust path (22), and

(c) Separation of the cathode chambers (12) from the environment.

The present disclosure relates to an apparatus for controlling an operation of a fuel cell system and a method therefor. The present disclosure may include a voltage sensor that measures an output voltage of a fuel cell stack, an air compressor that supplies air to a cathode of the fuel cell stack, a valve driver that adjusts an opening degree of an Airflow Control Valve (ACV), and a controller that, in an idle stop state, drives the air compressor at a lowest level and controls the opening degree of the ACV such that the output voltage of the fuel cell stack maintains a reference range.

Disclosed is a method of controlling an air supply system for a fuel cell. The air supply system includes a fuel cell stack, an air channel to supply air to an inlet of the fuel cell stack, a gas adsorption unit disposed on the air channel and configured to adsorb oxygen contained in air introduced into the air channel. In particular, the method includes: determining whether a power generation operation of the fuel cell stack is resumed; when the power generation operation of the fuel cell stack is resumed, controlling a voltage source to apply a voltage to the gas adsorption unit; and supplying air to the fuel cell stack through the air channel in a state in which the voltage is applied to the gas adsorption unit.

A method for no-purge starting up a fuel cell system is provided. The method includes calculating a nitrogen partial pressure from a target hydrogen concentration during driving that corresponds to a condition in which start-up without purging is possible and calculating a target hydrogen pressure satisfying the target hydrogen concentration from the calculated nitrogen partial pressure. Further, hydrogen is then supplied to the system based on the target hydrogen pressure.

First, a reaction gas is supplied to a fuel cell stack including a laminate of solid polymer electrolyte fuel cells and power generation is performed so that a temperature of the fuel cell stack reaches 65° C. or higher (heating power generation step). Next, the reaction gas is supplied to the fuel cell stack and the power generation is performed under a condition in which relative humidity is 100% or more (cleaning power generation step). Cooling water of room temperature may be supplied to the fuel cell stack from the outside before the cleaning power generation step is performed after the heating power generation step is completed, or after the cleaning power generation step is completed (quenching step).

A method of operating a fuel cell system comprising a fuel cell assembly configured to generate electrical power from a fuel flow and an oxidant flow, the method comprising a first phase and a subsequent second phase, the first phase comprising; operating the fuel cell assembly with a first stoichiometric ratio of oxidant flow to fuel flow to generate electrical power; providing said generated electrical power to a heater element for heating a coolant for supply to said fuel cell assembly; the second phase comprising; delivering coolant heated in the first phase to the fuel cell assembly; operating the fuel cell assembly with a second stoichiometric ratio of oxidant flow to fuel flow to generate electrical power, the second stoichiometric ratio lower than the first ratio.