Abstract: A fuel cell system that includes a control system for regulating the power produced by the fuel cell system. The fuel cell system includes a fuel cell stack adapted to produce electrical power from a feed. In some embodiments, the fuel cell system includes a fuel processing assembly adapted to produce the feed for the fuel cell stack from one or more feedstocks. The control system regulates the power produced by the fuel cell system to prevent damage to, and/or failure of, the system.

Abstract: Fuel cell systems and methods for providing power to an energy-consuming device and cooling of the energy-consuming device utilizing the endothermic process of desorbing hydrogen gas from a hydride bed. Fuel cell systems include a fuel cell stack, a hydrogen storage device having a volume of a hydrogen storage material, and a heat exchange system operatively connected to the hydrogen storage device and configured to heat the hydrogen storage material to desorb hydrogen gas therefrom for delivery to the fuel cell stack. The heat exchange system is further configured to deliver a cooled fluid stream to the energy-consuming device for cooling thereof. The cooled fluid stream may be produced, or cooled, by the endothermic desorption of hydrogen gas from the hydrogen storage device. In some fuel cell systems, the heat exchange system utilizes heat from the energy-consuming device to heat the hydrogen storage material for desorption of hydrogen gas therefrom.

Abstract: Systems and methods for initiating use of, or starting up, fuel cell stacks in subfreezing temperatures. The fuel cell stacks include a thermal management system that is adapted to deliver a liquid heat exchange fluid into thermal communication with a fuel cell stack, such as to heat the stack during startup of the stack when the stack is at a subfreezing temperature or operated in a subfreezing environment. In some embodiments, the thermal management system includes a heat exchange circuit that is configured to provide delivery of the liquid heat exchange fluid to the fuel cell stack even when the conduits are at a subfreezing temperature. In some embodiments, the fuel cell system is configured to deliver liquid heat exchange fluid from the fuel cell stack and heat exchange circuit when the thermal management system is not being utilized.

Abstract: Hydrogen-producing fuel processing assemblies and methods for delivering feedstock to a hydrogen-producing region of a hydrogen-producing fuel processing assembly. In some embodiments, the fuel processing assemblies include a feedstock delivery system that includes a pump assembly and a stall prevention mechanism that is adapted to reduce pressure in an outlet conduit during periods in which the pump assembly is not emitting a liquid outlet stream within or above a hydrogen-producing pressure range. In some embodiments, pressure in the outlet conduit is isolated from pressure in the hydrogen-producing region of the fuel processing assembly and is reduced during periods in which a liquid stream is not being pumped within or above a hydrogen-producing pressure range.

Abstract: Systems and methods for initiating startup of PSA assemblies in hydrogen-processing assemblies, which may include a hydrogen-generation assembly and/or a fuel cell stack. The systems and methods include startup procedures that provide for pressurization of the adsorbent beds of the PSA assembly without the need for a stored quantity or other supply of purified hydrogen gas. The systems and methods additionally or alternatively include startup procedures that restrict or even prevent contamination of portions of the PSA assembly, hydrogen storage devices and/or accumulator tanks with an impure gas stream and/or decrease accumulation of the impure gas stream therein. This impure gas stream may be the mixed gas, reformate, or other gas stream that is intended to be purified by the PSA assembly when the PSA assembly is in its hydrogen-purifying operating state.

Abstract: Liquid leak detection systems, and fuel cell systems and hydrogen-producing fuel processing systems containing the same. The liquid leak detection systems are adapted to detect liquid leaks from the fuel cell and/or fuel processing systems and to respond thereto, such as by interrupting the delivery of liquid reactants, by generating an alert, by transitioning the fuel processing system to a different operating state, and/or by shutting down the fuel processing and/or fuel cell system. The liquid leak detection systems may include a controller and at least one liquid detector, and in some embodiments may include a cover. In some embodiments, the liquid detector includes a signal emitter and a signal detector. In some embodiments, the liquid detector includes at least a pair of spaced-apart conductive members that nominally define an open circuit. In some embodiments, the cover is adapted to repel water and/or includes conductive particulate.

Abstract: Hydrogen-producing fuel processing systems, hydrogen purification membranes, hydrogen purification devices, fuel processing and fuel cell systems that include hydrogen purification devices, and methods for operating the same. In some embodiments, operation of the fuel processing system is initiated by heating at least the reforming region of the fuel processing system to at least a selected hydrogen-producing operating temperature. In some embodiments, an electric heater is utilized to perform this initial heating. In some embodiments, use of the electric heater is discontinued after startup, and a burner or other combustion-based heating assembly combusts a fuel to heat at least the hydrogen producing region, such as due to the reforming region utilizing an endothermic catalytic reaction to produce hydrogen gas.

Abstract: Fuel cell systems and methods for controlling the operation of fuel cell assemblies included therein. In some embodiments, the fuel cell assemblies include a fuel processor and a fuel cell stack, and the fuel cell system includes a control system that controls the operation thereof based upon at least one variable associated therewith. In some embodiments, the variable is associated with the hydrogen (or other product) stream from the fuel processor. In some embodiments, the variable is the pressure of this stream. In some embodiments, the control system controls the operation of the fuel cell system to maintain the pressure of the hydrogen stream within one or more threshold values. In some embodiments, the control system controls the operation of the fuel cell system to maintain the pressure of the hydrogen stream within selected threshold values and to maintain the fuel cell stack's output voltage above a selected threshold.

Abstract: A fuel cell system that includes a control system for regulating the power produced by the fuel cell system. The fuel cell system includes a fuel cell stack adapted to produce electrical power from a feed. In some embodiments, the fuel cell system includes a fuel processing assembly adapted to produce the feed for the fuel cell stack from one or more feedstocks. The control system regulates the power produced by the fuel cell system to prevent damage to, and/or failure of, the system.

Abstract: Hydrogen-producing fuel processing assemblies and methods for delivering feedstock to a hydrogen-producing region of a hydrogen-producing fuel processing assembly. In some embodiments, the fuel processing assemblies include a feedstock delivery system that includes a pump assembly and a stall prevention mechanism that is adapted to reduce pressure in an outlet conduit during periods in which the pump assembly is not emitting a liquid outlet stream within or above a hydrogen-producing pressure range. In some embodiments, pressure in the outlet conduit is isolated from pressure in the hydrogen-producing region of the fuel processing assembly and is reduced during periods in which a liquid stream is not being pumped within or above a hydrogen-producing pressure range.

Abstract: Hydrogen-producing fuel processing systems, hydrogen purification membranes, hydrogen purification devices, fuel processing and fuel cell systems that include hydrogen purification devices, and methods for operating the same. In some embodiments, operation of the fuel processing system is initiated by heating at least the reforming region of the fuel processing system to at least a selected hydrogen-producing operating temperature. In some embodiments, an electric heater is utilized to perform this initial heating. In some embodiments, use of the electric heater is discontinued after startup, and a burner or other combustion-based heating assembly combusts a fuel to heat at least the hydrogen producing region, such as due to the reforming region utilizing an endothermic catalytic reaction to produce hydrogen gas.

Abstract: The present disclosure is directed to systems and methods for actively controlling the steam-to-carbon ratio in hydrogen-producing fuel processing systems that include a feedstock delivery system. The feedstock delivery system supplies a combined feedstock stream including steam and carbon-containing feedstock to a hydrogen-producing region, which produces a mixed gas stream including hydrogen gas as a majority component therefrom. The systems and methods may include measuring a thermodynamic property of a steam stream, a carbon-containing feedstock stream, and/or the combined feedstock stream and controlling the flow rate and/or pressure of a water stream, the steam stream, and/or the carbon-containing feedstock stream based on a desired steam-to-carbon ratio in the combined feedstock stream and/or a desired flow rate of the mixed gas stream and may include feedforward and/or feedback control strategies.

Abstract: Fuel cell stacks and systems with thermal management systems to deliver a liquid heat exchange fluid into thermal communication with the stack and thereafter recycle the stream. In some embodiments, the system is adapted to selectively apportion the recycled liquid stream between a stream that, prior to reuse as a heat exchange stream, is returned to a fluid reservoir and/or selectively cooled, and/or selectively returned to the reservoir and mixed with heat exchange fluid in the reservoir, and a stream that is returned into thermal communication with the stack without returning the stream to the reservoir and/or without heating or cooling and/or without being mixed with additional heat exchange fluid. In some embodiments, the system is adapted to automatically apportion the recycled stream responsive to its temperature. In some embodiments, the system includes a thermostatic valve and/or selectively apportions the recycled stream without requiring an electronic controller or manual input.

Abstract: Hydrogen-processing assemblies, components of hydrogen-processing assemblies, and fuel-processing and fuel cell systems that include hydrogen-processing assemblies. The hydrogen-processing assemblies include a hydrogen-separation assembly positioned within the internal volume of an enclosure in a spaced relation to at least a portion of the internal perimeter of the body of the enclosure.

Abstract: The present disclosure is directed to systems and methods for maintaining hydrogen-selective membranes during periods of inactivity. These systems and methods may include heating and maintaining at least the hydrogen-selective membrane of a hydrogen-producing fuel processing system in a thermally buffered state and/or controlling the chemical composition of the gas streams that may come into contact with the hydrogen-selective membrane. Controlling the chemical composition of the gas streams that may come into contact with the hydrogen-selective membrane may include maintaining a positive pressure of an inert, blanket, reducing, and/or non-oxidizing gas within the membrane separation assembly and/or periodically supplying a reducing gas stream to the membrane separation assembly.

Abstract: A fuel cell system that includes a control system for regulating the power produced by the fuel cell system. The fuel cell system includes a fuel cell stack adapted to produce electrical power from a feed. In some embodiments, the fuel cell system includes a fuel processing assembly adapted to produce the feed for the fuel cell stack from one or more feedstocks. The control system regulates the power produced by the fuel cell system to prevent damage to, and/or failure of, the system.

Abstract: Hydrogen-producing fuel processing systems, hydrogen purification membranes, hydrogen purification devices, fuel processing and fuel cell systems that include hydrogen purification devices, and methods for operating the same. In some embodiments, operation of the fuel processing system is initiated by heating at least the reforming region of the fuel processing system to at least a selected hydrogen-producing operating temperature. In some embodiments, an electric heater is utilized to perform this initial heating. In some embodiments, use of the electric heater is discontinued after startup, and a burner or other combustion-based heating assembly combusts a fuel to heat at least the hydrogen producing region, such as due to the reforming region utilizing an endothermic catalytic reaction to produce hydrogen gas.

Abstract: Systems and methods for initiating use of, or starting up, fuel cell stacks in subfreezing temperatures. The fuel cell stacks include a thermal management system that is adapted to deliver a liquid heat exchange fluid into thermal communication with a fuel cell stack, such as to heat the stack during startup of the stack when the stack is at a subfreezing temperature or operated in a subfreezing environment. In some embodiments, the thermal management system includes a heat exchange circuit that is configured to provide delivery of the liquid heat exchange fluid to the fuel cell stack even when the conduits are at a subfreezing temperature. In some embodiments, the fuel cell system is configured to deliver liquid heat exchange fluid from the fuel cell stack and heat exchange circuit when the thermal management system is not being utilized.

Abstract: Hydrogen-producing fuel processing assemblies and fuel cell systems with at least one temperature-responsive valve assembly, and methods for feedback regulation of the hydrogen-producing region. The temperature-responsive valve assembly responds automatically to the temperature of a gas stream of interest to regulate the flow of a subject gas stream therethrough. In some embodiments, these streams are the same streams, while in others, they are different streams. The streams may include at least the reformate stream from a hydrogen-producing region of the fuel processing assembly, the byproduct stream from a purification region, and the product gas stream from the purification region. In some embodiments, the subject gas stream may be the byproduct stream, which is in fluid communication for delivery as a combustible fuel stream for a burner or other heating assembly that produces an exhaust stream to heat the hydrogen-producing region of the fuel processing assembly.

Abstract: Fuel cell stacks and systems with thermal management systems to deliver a liquid heat exchange fluid into thermal communication with the stack and thereafter recycle the stream. In some embodiments, the system is adapted to selectively apportion the recycled liquid stream between a stream that, prior to reuse as a heat exchange stream, is returned to a fluid reservoir and/or selectively cooled, and/or selectively returned to the reservoir and mixed with heat exchange fluid in the reservoir, and a stream that is returned into thermal communication with the stack without returning the stream to the reservoir and/or without heating or cooling and/or without being mixed with additional heat exchange fluid. In some embodiments, the system is adapted to automatically apportion the recycled stream responsive to its temperature. In some embodiments, the system includes a thermostatic valve and/or selectively apportions the recycled stream without requiring an electronic controller or manual input.