Abstract: Combustion fuel stream supply systems for use with pressure swing adsorption (PSA) assemblies, and hydrogen-generation assemblies and/or fuel cell systems containing the same. The PSA assemblies are operated according to a PSA cycle to receive a mixed gas stream and, while producing a product hydrogen stream therefrom, intermittently discharge a byproduct stream. The byproduct stream, when available, may be delivered as a fuel stream to a heating assembly, which may heat the hydrogen-producing region that produces the mixed gas stream. A combustion fuel stream supply system selectively supplies an auxiliary fuel stream when a byproduct stream is not discharged or otherwise does not have a predetermined combustion fuel value sufficient, when combusted, to maintain the hydrogen-producing region within a desired temperature range. The one or more streams supplied to the heating assembly have a combined combustion fuel value at least as great as the predetermined threshold value.

Abstract: Systems and methods for regulating fuel cell air flow, such as during low loads and/or cold temperature operation. These systems and methods may include providing a thermal management fluid, such as air, to the fuel cell stack, transferring thermal energy between the thermal management fluid and the fuel cell stack, and varying the flow rate of the thermal management fluid that comes into contact with the fuel cell stack to maintain the temperature of the fuel cell stack within an acceptable temperature range. Varying the flow rate of the thermal management fluid may include varying the overall supply rate of the thermal management fluid within the fuel cell system and/or providing an alternative flow path for the thermal management fluid such that a portion of the thermal management fluid supplied by the fuel cell system does not come into contact with the fuel cell stack.

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: 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: Thermally primed fuel processing assemblies and hydrogen-producing fuel cell systems that include the same. The thermally primed fuel processing assemblies include at least one hydrogen-producing region housed within an internal compartment of a heated containment structure. In some embodiments, the heated containment structure is an oven. In some embodiments, the compartment also contains a purification region and/or heating assembly. In some embodiments, the containment structure is adapted to heat and maintain the internal compartment at or above a threshold temperature, which may correspond to a suitable hydrogen-producing temperature. In some embodiments, the containment structure is adapted to maintain this temperature during periods in which the fuel cell system is not producing power and/or not producing power to satisfy an applied load to the system. In some embodiments, the fuel cell system is adapted to provide backup power to a power source, which may be adapted to power the containment structure.

Abstract: Systems and methods for producing hydrogen gas with a fuel processing system that includes a hydrogen-producing region that produces hydrogen gas from a feed stream and a heating assembly that consumes a fuel stream to produce a heated exhaust stream for heating the hydrogen-producing region. In some embodiments, the heating assembly heats the hydrogen-producing region to at least a minimum hydrogen-producing temperature. In some embodiments, the rate at which an air stream is delivered to the heating assembly is controlled to selectively increase or decrease the temperature of the heated exhaust stream. In some embodiments, the feed stream and the fuel stream both contain a carbon-containing feedstock and at least 25 wt % water. In some embodiments, the feed and fuel streams have the same composition.

Abstract: Combustion-based heating assemblies and hydrogen-producing fuel processing assemblies that include at least a reforming region adapted to be heated by the heating assemblies. The heating assembly may include at least one fuel chamber and at least one heating and ignition source. The at least one fuel chamber may be adapted to receive at least one fuel stream at a first temperature. The fuel stream may include a liquid, combustible, carbon-containing fuel having an ignition temperature greater than the first temperature at which the fuel stream is delivered to the fuel chamber. The at least one heating and ignition source may be adapted to heat at least a portion of the fuel chamber to raise the temperature of at least a portion of the carbon-containing fuel to a second temperature at least as great as the ignition temperature and to ignite the carbon-containing fuel. Methods of use are also disclosed.

Abstract: Pressure swing adsorption (PSA) assemblies with purge control systems, and hydrogen-generation assemblies and/or fuel cell systems containing the same. The PSA assemblies are operated according to a PSA cycle to produce a product hydrogen stream and a byproduct stream from a mixed gas stream. The byproduct stream may be delivered as a fuel stream to a heating assembly, which may heat the hydrogen-producing region that produces the mixed gas stream. The PSA assemblies may be adapted to regulate the flow of purge gas utilized therein, such as according to a predetermined, non-constant profile. In some embodiments, the flow of purge gas is regulated to maintain the flow rate and/or fuel value of the byproduct stream at or within a determined range of a threshold value, and/or to regulate the flow of purge gas to limit the concentration of carbon monoxide in a heated exhaust stream produced from the byproduct stream.

Abstract: Fuel cell systems and methods for controlling the operation of components of the fuel cell system, which may include a fuel source and a fuel cell stack. In some examples, a fuel source is adapted to provide supply fuel to a fuel cell stack at a supply pressure. The fuel cell stack produces electric current at a production amperage. In some examples, a control system is adapted to control operation of the fuel cell stack based on a pressure detected at the fuel cell stack. In some examples, a target production amperage is determined based on the detected pressure, such that when electric current is produced at the target production amperage for the detected pressure, the fuel cell stack consumes a predetermined proportion of the supply fuel.

Abstract: Fuel cell systems and methods that perform maintenance hydration by supplying power to satisfy at least part of an applied load from an energy-consuming assembly while a primary power source is in electrical communication with and available to supply power to the energy-consuming assembly to satisfy the portion of the applied load. In some embodiments, the systems or methods may determine a start time, or start condition, for hydration of the fuel cell system. Power may be supplied from the activated fuel cell system at an output voltage that is higher than a voltage at which power from the primary power source is being supplied, such that the applied load is satisfied, at least in part, by power from the fuel cell system instead of from the primary power source. Upon operation for a period sufficient to rehydrate the fuel cell stack, operation of the fuel cell system may be discontinued.

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-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: Feedstock delivery systems and hydrogen-producing fuel processing assemblies and fuel cell systems containing the same. The feedstock delivery systems include a liquid pump that draws at least one liquid feedstock from a supply and delivers at least one feed stream containing the feedstock(s) to a fuel processor, such as to the hydrogen-producing region thereof. The feedstock delivery system further includes a recycle conduit that establishes a fluid flow path for the liquid feedstock(s) from a location downstream of the pump back to a location upstream of the pump. In some embodiments, the feedstock delivery system further includes a flow restrictor associated with the recycle conduit and a pressure-actuated valve that selectively permits the recycled feedstock to bypass the flow restrictor. In some embodiments, the pump is configured to draw a greater flow rate of the feed stream from the supply than is delivered to the fuel processor.

Abstract: Hydrogen-producing fuel processing assemblies for producing hydrogen gas. The assemblies include a catalyst chamber, a heat source adapted to heat the catalyst chamber, a hydrogen-producing region within the catalyst chamber adapted to produce hydrogen gas from a feed stream, and a conductive guide structure within the catalyst chamber adapted to conduct and distribute heat from the heat source within the hydrogen-producing region and to direct fluid through the hydrogen-producing region. In some embodiments, the conductive guide structure includes a helical member. In some embodiments, the assembly further includes a vaporization region within the catalyst chamber. In some embodiments, the fuel processing assembly is adapted to produce hydrogen gas via a steam reforming or other endothermic reaction.

Abstract: Thermal and hydration management systems and methods for fuel cell systems, including control of electrolytic membrane hydration levels. In some embodiments, the thermal properties of the fuel cell are controlled based on a variable associated with the oxidant supply stream and/or a variable associated with the fuel cell energy output. In some embodiments, the temperature of the fuel cell is controlled based on the temperature of the oxidant supply stream. In some embodiments, the temperature range across the fuel cell stack is controlled based on the flow rate of the oxidant stream and the electrical output generated by the fuel cell stack. In some embodiments, the humidity within the fuel cell stack is controlled. In some embodiments, the liquid water content of the cathode exhaust stream is controlled.

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: Fuel cell systems and methods for controlling the operation of components of the fuel cell system, which may include a fuel source and a fuel cell stack. In some examples, a fuel source is adapted to provide supply fuel to a fuel cell stack at a supply pressure. The fuel cell stack produces electric current at a production amperage. In some examples, a control system is adapted to control operation of the fuel cell stack based on a pressure detected at the fuel cell stack. In some examples, a target production amperage is determined based on the detected pressure, such that when electric current is produced at the target production amperage for the detected pressure, the fuel cell stack consumes a predetermined proportion of the supply fuel.

Abstract: Systems and methods for producing hydrogen gas with a fuel processing system that includes a hydrogen-producing region that produces hydrogen gas from a feed stream and a heating assembly that consumes a fuel stream to produce a heated exhaust stream for heating the hydrogen-producing region. In some embodiments, the heating assembly heats the hydrogen-producing region to at least a minimum hydrogen-producing temperature. In some embodiments, the rate at which an air stream is delivered to the heating assembly is controlled to selectively increase or decrease the temperature of the heated exhaust stream. In some embodiments, the feed stream and the fuel stream both contain a carbon-containing feedstock and at least 25 wt % water. In some embodiments, the feed and fuel streams have the same composition.

Abstract: Thermally primed fuel processing assemblies and hydrogen-producing fuel cell systems that include the same. The thermally primed fuel processing assemblies include at least one hydrogen-producing region housed within an internal compartment of a heated containment structure. In some embodiments, the heated containment structure is an oven. In some embodiments, the compartment also contains a purification region and/or heating assembly. In some embodiments, the containment structure is adapted to heat and maintain the internal compartment at or above a threshold temperature, which may correspond to a suitable hydrogen-producing temperature. In some embodiments, the containment structure is adapted to maintain this temperature during periods in which the fuel cell system is not producing power and/or not producing power to satisfy an applied load to the system. In some embodiments, the fuel cell system is adapted to provide backup power to a power source, which may be adapted to power the containment structure.

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.