An aircraft electrical power supply system includes a fuel cell auxiliary power unit (APU) that supplies auxiliary electrical power to an aircraft, a fuel cell power plant that supplies primary electrical power to the aircraft, and a hydrogen storage unit that supplies hydrogen to the fuel cell APU and the fuel cell power plant.

The present invention relates to an SOEC system (1), comprising a fuel cell stack (2) having a gas side (3) and an air side (4), and an ejector (5) for supplying a process fluid to a gas inlet (6) on the gas side (3), wherein the ejector (5) comprises a primary inlet (7), for introducing a water-containing primary process fluid through a primary line (8) of the SOEC system (1) into a primary portion (9) of the ejector (5), and a secondary inlet (10), for introducing recirculated secondary process fluid through a recirculation line (11) of the SOEC system (1) from a gas outlet (12) on the gas side (3) into a secondary portion (13) of the ejector (5), wherein the SOEC system (1) further comprises a control gas supply portion (14) for supplying control gas into the primary portion (9) and into the secondary portion (13) in order to control a pressure and/or mass flow in the primary portion (9) and in the secondary portion (13), and wherein the control gas supply portion (14) comprises a valve arrangement (19, 20) for controlling the pressure and/or the mass flow in the primary portion (9) and in the secondary portion (13). The invention further relates to a method for operating an SOEC system (1) according to the invention.

A method for operating a fuel cell system comprising a control unit and at least one fuel cell comprises a cycle of the following steps: recording of an actual U/I characteristic curve of the fuel cell, comparison of the recorded actual U/I characteristic curve of the fuel cell with a target U/I characteristic curve stored in a memory, at least within a predetermined or pre-determinable current range, and determination of the difference between the target U/I characteristic curve and the actual U/I characteristic curve within the current range, comprising the following steps: continuous or clocked repetition of the cycle until the difference reaches or exceeds a predetermined or pre-determinable difference limit value, and adjustment of at least one parameter of the control unit to reduce or minimize the difference.

Provided is a fuel cell system including: a fuel cell; a reactant gas supply section; a converter; an alternating-current superimposing unit; a phase difference deriving unit configured to derive a phase difference that is a phase lag of an alternating-current voltage relative to an alternating current in an alternating-current component output from the fuel cell; and a first inference unit. The first inference unit infers that the fuel cell is in an inappropriate wet state, when the absolute value of an amount of change in the phase difference has become equal to or larger than a predetermined criterion value immediately after the magnitude of a change in the value of at least one of parameters that are a flow rate of a reactant gas, a stoichiometric ratio, and an output current has exceeded a predetermined criterion.

A water removing system and method of a fuel cell vehicle using impedance are provided. The system measures measure the low frequency impedance of a fuel cell stack when a fuel cell system is stopped in a low temperature condition, and adjusts the air supply amount and supply time for removing the water supercharged into the fuel cell stack using the measured low frequency impedance. Thus, air is prevented from being unnecessarily supercharged into the fuel cell stack and at the same time, the water remaining in the fuel cell stack is removed.

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.

Disclosed are a method and apparatus for subzero start-up of a fuel cell. The method for the subzero start-up of the fuel cell includes: introducing a gas containing hydrogen having a mass percentage of 5% to 100% to a hydrogen electrode and an air electrode of the fuel cell (2) under a condition of minus 50° C. to 0° C.; applying a current or a voltage to the fuel cell (2), and utilizing ohmic heat generation, reaction heat, and concentration overpotential heat generation of the fuel cell (2) to raise the fuel cell (2) to a required temperature or to cause the fuel cell (2) to reach to a set time, so as to implement the subzero start-up of the fuel cell.

A water removing system and method of a fuel cell vehicle using impedance are provided. The system measures measure the low frequency impedance of a fuel cell stack when a fuel cell system is stopped in a low temperature condition, and adjusts the air supply amount and supply time for removing the water supercharged into the fuel cell stack using the measured low frequency impedance. Thus, air is prevented from being unnecessarily supercharged into the fuel cell stack and at the same time, the water remaining in the fuel cell stack is removed.

Systems, methods, and devices of the various embodiments provide a hardware and software architecture enabling electrochemical impedance spectroscopy (“EIS”) to be performed on multiple electrochemical devices, such as fuel cells, at the same time without human interaction with the electrochemical devices and to use EIS to dynamically monitor the performance of a fuel cell system. Embodiment methods may include determining an impedance of a set of fuel cells using electrochemical impedance spectroscopy, determining an ohmic polarization of the set of fuel cells from the impedance, determining a concentration polarization of the set of fuel cells from the impedance, comparing the ohmic polarization of the set of fuel cells to a first threshold, comparing the concentration polarization of the set of fuel cells to a second threshold, and initiating a corrective action when the ohmic polarization is above the first threshold or when the concentration polarization is below the second threshold.

A fuel cell system and method, the system including power generating fuel cells disposed in a stack, each power generating fuel cell including an anode, a cathode, and an electrolyte, a sensing fuel cell including an anode, a cathode, and an electrolyte, and a fuel processor configured to purify a fuel provided to the power generating fuel cells and the sensing fuel cell. The anode of the sensing fuel cell is thinner than the anodes of the power generating fuel cells.