The invention relates to a method for operating a fuel cell device (10), wherein the fuel cell device (10) is operated in accordance with a quality characteristic of a fuel that is used. According to the invention, the quality characteristic is determined from a partial analysis of the constituents of the fuel that is used. The invention further relates to a fuel cell device (10) that is operated by means of such a method.

An illustrative example hydrogen concentration sensor includes a first end plate. A hydrogen evolving electrode assembly that generates hydrogen is situated adjacent the first end plate and at least partially exposed through an opening through the end plate. A separator plate is between the hydrogen evolving electrode assembly and a detection electrode assembly. The separator plate includes a passage to allow a flow of hydrogen generated by the hydrogen evolving electrode assembly to the detection electrode assembly. A second end plate is situated adjacent the detection electrode assembly and includes a second opening where a portion of the detection electrode assembly is exposed to a fluid of interest to provide an indication of a concentration of hydrogen in the fluid of interest.

A method for determining a storage capacity or average oxidation state (AOS) of a redox flow battery system including an anolyte and a catholyte includes discharging a portion of the anolyte and catholyte of the redox flow battery system at a discharge rate that is within 10% of a preselected discharge rate; after discharging the redox flow battery system, determining an end OCV; and determining the storage capacity or AOS from the end OCV. Other methods can be used to determine the storage capacity or AOS using a measured OCV.

A redox flow battery system includes an anolyte having a first ionic species in solution; a catholyte having a second ionic species in solution, where the redox flow battery system is configured to reduce the first ionic species in the anolyte and oxidize the second ionic species in the catholyte during charging; a first electrode in contact with the anolyte, where the first electrode includes channels for collection of particles of reduced metallic impurities in the anolyte; a second electrode in contact with the catholyte; and a separator separating the anolyte from the catholyte. A method of reducing metallic impurities in an anolyte of a redox flow battery system includes reducing the metallic impurities in the anolyte; collecting particles of the reduced metallic impurities; and removing the collected particles using a cleaning solution.

An apparatus and a method for controlling a fuel electrode drain valve of a fuel cell system are disclosed. The apparatus includes: a hydrogen sensor that measures the concentration of hydrogen released by opening a fuel electrode drain valve, a first pressure sensor that measures the inlet pressure of the fuel electrode drain valve, a second pressure sensor that measures the outlet pressure of the fuel electrode drain valve; and a controller that controls the opening area of the fuel electrode drain valve to the maximum value when draining the condensate and controls the opening area of the fuel electrode drain valve based on the difference between the inlet pressure and the outlet pressure of the fuel electrode drain valve when purging the hydrogen.

An apparatus and a method for controlling a fuel electrode drain valve of a fuel cell system are disclosed. The apparatus includes: a hydrogen sensor that measures the concentration of hydrogen released by opening a fuel electrode drain valve, a first pressure sensor that measures the inlet pressure of the fuel electrode drain valve, a second pressure sensor that measures the outlet pressure of the fuel electrode drain valve; and a controller that controls the opening area of the fuel electrode drain valve to the maximum value when draining the condensate and controls the opening area of the fuel electrode drain valve based on the difference between the inlet pressure and the outlet pressure of the fuel electrode drain valve when purging the hydrogen.

A method of examining a fuel cell by means of a cyclic voltammetry analysis, wherein the cyclic voltammetry analysis is used to ascertain a gas composition in the fuel cell. The fuel cell has a first gas space for a first reactant and a second gas space for a second reactant, where no reactant is supplied at least to one of the two gas spaces, especially to either gas space, during the cyclic voltammetry analysis. The cyclic voltammetry analysis is used to ascertain a concentration of hydrogen in the gas spaces.

A control unit of a fuel cell system measures or estimates an amount of nitrogen in an anode flow field, performs a first comparison by comparing the amount of nitrogen with the first threshold amount, performs a second comparison by comparing a differential pressure calculated by subtracting a cathode pressure value indicating a pressure inside a cathode flow field from an anode pressure value indicating a pressure inside the anode flow field with the second threshold pressure when the amount of nitrogen in the anode flow field is greater than the first threshold amount in the first comparison, and controls opening and closing of a valve based on the result of the first comparison and the result of the second comparison.

A control unit of a fuel cell system estimates an amount of nitrogen in an anode flow field, performs a first comparison by comparing the estimated amount of nitrogen with a first threshold amount, performs a second comparison by comparing a target power generation amount as a target amount of power generation by a fuel cell stack with a second threshold amount in a case where the estimated amount of nitrogen in the anode flow field exceeds the first threshold amount in the first comparison, and controls opening and closing of a first valve and opening and closing of the second valve based on a result of the first comparison and a result of the second comparison.

Methods and systems are provided for iron preformation in a redox flow battery. In one example, a method may include, in a first condition, discharging and then charging the redox flow battery, and in a second condition, charging the redox flow battery including preforming iron metal at a negative electrode of the redox flow battery, and thereafter entering an idle mode of the redox flow battery including adjusting one or more electrolyte conditions. In some examples, each of preforming the iron metal and adjusting the one or more electrolyte conditions may increase a battery charge capacity to greater than a threshold battery charge capacity.