Abstract:
An electrochemical fuel cell assembly comprises a fuel cell stack having a fuel delivery inlet and a fuel delivery outlet. The fuel cell stack further includes a number of fuel cells each having a membrane-electrode assembly and a fluid flow path coupled between the fuel delivery inlet and the fuel delivery outlet for delivery of fuel to the membrane- electrode assembly. A fuel delivery conduit is coupled to the fuel delivery inlet for delivery of fluid fuel to the stack. A bleed conduit is coupled to the fuel delivery outlet for venting fluid out of the stack. A variable orifice flow control device coupled to the bleed conduit configured to dynamically vary an amount of fluid from the fuel delivery outlet passing into the bleed conduit as a function of one or more of the control parameters: (i) measured fuel concentration; (ii) measured humidity; (iii) cell voltages of fuel cells in the stack; (iv) impedance of fuel cells in the stack; (v) resistance of fuel cells in the stack. The variable orifice flow control device may be coupled to a recirculation conduit and may be configured to dynamically vary a proportion of fluid from the fuel delivery outlet passing into the bleed conduit as a function of the control parameters.
Abstract:
The IR resistance of each unit cell 2 is measured (step S14), and a highest unit cell voltage as a threshold voltage is set based on the IR resistance and the load current (step S18). The setting of the highest unit cell voltage uses map data that approximates current-voltage characteristics of a unit cell when the fuel gas is insufficiently supplied. In that case, the highest unit cell voltage is determined based on the voltage with respect to the load current obtained from the map data, and the IR loss calculated from the IR resistance and the load current. This highest unit cell voltage is compared with the measured unit cell voltage (step S22). If the unit cell voltage is below the highest unit cell voltage, the power generation of the fuel cell is stopped or restrained (step S24).
Abstract:
An integrated heat management assembly that is thermally coupled to a component requiring temperature control is provided. The integrated heat management assembly in one embodiment of the invention is a heat switch which includes two opposed surfaces, a first surface being a hot contact which is coupled to the component, and the second surface being a cold contact which is coupled to a heat sink. An actuator which may be a phase changing material, is mechanically coupled to one of the two surfaces such that when the component reaches a threshold temperature, the actuator is triggered to bring the two surfaces into contact. In this manner, the hot surface conducts heat to the cold surface which then delivers heat to the heat sink to thereby lower the temperature of the component. Other embodiments include heat pipes associated with the heat switch in order to further dissipate heat or to divert it to other areas of the component requiring temperature control. Corresponding techniques are provided in accordance with the method of the invention.
Abstract:
Some embodiments of the present invention provide a system and method that incorporates a call to an alarm recovery sequence into a safety system for use within a fuel cell testing system. In other embodiments of the present invention there is provided a safety system and method, for use within a fuel cell testing system, which is able to suspend a (fuel cell testing) trial and initiate an alarm recovery sequence upon detecting that a corresponding alarm threshold has been violated. The safety system and method is then able to restart the trial if it is determined that the alarm recovery sequence was successful, in that the process and operating parameters that violated the particular alarm threshold have been brought back to within a safe operating range.
Abstract:
Eine Vorrichtung und ein Verfahren zum Regeln der Luftfeuchte in einer Brennstoffzelle erfasst eine Sprungantwort der Abgabespannung einer Brennstoffzelle bei unterbrochener Versorgung elektrischer Verbraucher und ermittelt aus der erfassten Sprungantwort Parameter des dynamischen Zeitverhaltens und errechnet damit eine Kapazität der Brennstoffzelle. In Abhängigkeit einer eventuellen Abweichung von einer vorgegebenen Kapazität wird eine Befeuchtungssteuereinheit dazu veranlasst, die Befeuchtung zu erhöhen oder zu senken. Damit wird eine in situ Erfassung des Feuchtehaushalts einer Brennstoffzelle möglich, die deren elektrische Leistung über einen längeren Zeitraum konstant halten kann, was insbesondere Wartungsintervalle verlängern kann.