Abstract: A method for fuel cell system thermal management includes: maintaining a first zone at a first selected temperature range, maintaining a second zone at a second selected temperature range, and maintaining a third zone at a third selected temperature range. The second zone is in thermal communication with a first sensor and comprises a reformer, while the third zone is in thermal communication with a second sensor and comprises a fuel cell stack. The second selected temperature range is greater than the first selected temperature range, while the third selected temperature range is greater than the second selected temperature range.

Abstract: A current carrier for a solid oxide fuel cell system comprising a current-carrying core formed of a high-conductivity metallic material such as copper, brass, bronze, silver, silver-copper alloys, molybdenum, tungsten, or the like, and a protective jacket surrounding the core material. Preferably, the jacket is metallurgically bonded to the core. The jacket is formed of a high temperature alloy such as stainless steel, nickel, or a nickel alloy. The jacket is structurally competent to maintain the form of the electrical carrier at elevated temperatures at which the core material may be structurally incompetent. The current carrier may be sized comparable to conventional copper cables. The carrier is attached to a fuel cell current collector by a clamp assembly having a large surface contact area. Preferably, a contact paste consisting of fine silver particles forms a diffusion bond between the clamp and the carrier jacket, resulting in a low-loss connection.

Abstract: An SOFC stack module including an integral individual stack manifold containing all of the gas pathways necessary for supply and exhaust of fuel gas and cathode air to and from the stack chimneys. The stack is mounted and hermetically joined directly to the manifold without an intermediate base plate. Flanges at the inlet and outlet ports couple to system distributary manifolds via high temperature sealing joints. The manifold preferably is fabricated of a ferritic stainless steel, and may be formed in a one-piece casting, a combination of multiple castings and stamped plates metallurgically joined (brazed or welded together), or stamped from sheet metal stock. Preferably, the manifold includes fin structures extending into adjacent fuel gas and cathode air chambers to enhance balancing of temperatures by heat exchange therebetween. Heat exchange may be further improved by configuring the manifold to have a plurality of interleaved anode and cathode gas supply chambers.

Abstract: An etched interconnect for fuel cell elements comprising solid oxide electrolyte, an anode, and a cathode, includes a conductive base sheet having first and second faces having anode and cathode gas flow passages, respectively. The anode gas flow passages and cathode gas flow passages each have a unique geometry selected to optimize fuel and oxidant gas flow. In a preferred embodiment, the gas flow passages are prepared using a photochemical etching process.

Abstract: In a solid-oxide fuel cell assembly comprising a plurality of components having electrically-conductive mating surfaces therebetween, the surfaces are sealed by gasket elements that include first and second silver braze alloy layers and a dielectric layer, formed preferably of yttrium-stabilized zirconia (YSZ), disposed between the alloy layers. The alloy is capable of bonding to many ceramics, including YSZ, and is readily brazed to the oxide layer formed on many metals at elevated temperatures. Because the braze alloy is electrically conductive, a dielectric layer must be included to break conductivity in bonding applications where electrical insulation is required. YSZ functions as a reliable insulator and will not crystallize or fracture as do prior art glass insulators. The assembly is useful as an auxiliary power unit in a vehicle.

Abstract: In assembling an SOFC fuel cell stack from a plurality of cassettes, the mounting plate of one cassette is attached to, and insulated from, the separator plate of the next-adjacent cassette by a peripheral dielectric seal consisting of a ceramic coating and a metal braze. Materials suitable for the ceramic coating include yttrium stabilized zirconia (YSZ), zirconia toughened alumina, magnesium silicates such as the mineral forsterite, magnesium aluminates, magnesium aluminosilicates and lanthanum zirconate. The ceramic coating may be applied to the cassette's outer surface in known fashion as by physical vapor deposition, chemical vapor deposition, sputtering, and various methods of plasma spray. An underlayer of alumina may also be used to provide a redundant layer of electrical insulation.

Abstract: A method of main reformer startup is disclosed. The method comprises introducing a first supply of fuel and a first supply of air into a micro-reformer. The first supply of fuel is increased to produce a heated reformate in the micro-reformer. The heated reformate is directed through a main reformer in order to heat the main reformer. At least a portion of the heated reformate is burned in the main reformer. A second supply of fuel and a second supply of air is introduced into the main reformer to produce a main supply of reformate. A method for maintaining a vehicle device in standby condition is also disclosed.

Abstract: A minimum joint thickness can be assured by incorporating beads or particles having a diameter corresponding to the joint thickness desired and which are infusible at the brazing temperature. Preferably such particles are formed of high-melting metals, metal oxides, ceramics, or cermets and are mixed into the alloy paste prior to fusing. In a preferred embodiment, the particle-containing paste is mixed with a non-flux carrier to facilitate application to the elements to be brazed. Exemplary application methods may include painting, rolling, screening, or extrusion dispensing. Brazing alloys in accordance with the invention are useful in bonding ceramics to ceramics, ceramics to metals, and metals to metals.

Abstract: In a fuel cell assembly, nickel-based anodes are readily oxidized when exposed to oxygen as may happen through atmospheric invasion of the assembly during cool-down following shutdown of the assembly. Repeated anode oxidation and reduction can be destructive of the anodes, leading to cracking and failure. To prevent such oxygen migration, oxygen getter devices containing oxygen-gettering material such as metallic nickel are provided in the fuel passageways leading to and from the anodes. Oxidation of the oxygen-gettering material is readily reversed through reduction by fuel when the assembly is restarted.

Abstract: In a modular fuel cell cassette for forming a fuel cell stack, anode openings in the mounting plate and separator plate are separated and connected by modular spacer rings such that the cassette is incompressible at operating temperatures and compressive loads within the stack. The spacer rings are formed in modules wherein all of the rings required for all of the anode supply chimneys or all of the anode exhaust chimneys of any given cassette are ganged together and include a perimeter rail to which the rings are connected which automatically orients and positions the rings within the cassette during assembly thereof. The present invention eliminates the prior art need for individually positioning and spot welding each prior art ring in place prior to assembly of a prior art cassette. Two different structural embodiments for a spacer ring module are disclosed.

Abstract: A method of main reformer startup is disclosed. The method comprises introducing a first supply of fuel and a first supply of air into a micro-reformer. The first supply of fuel is increased to produce a heated reformate in the micro-reformer. The heated reformate is directed through a main reformer in order to heat the main reformer. At least a portion of the heated reformate is burned in the main reformer. A second supply of fuel and a second supply of air is introduced into the main reformer to produce a main supply of reformate. A method for maintaining a vehicle device in standby condition is also disclosed.

Abstract: An electrical interconnect for a solid-oxide fuel cell stack assembly, including a novel sintering paste and an improved manufacturing process for an anode and cathode electrical contacts is disclosed. On the anode side, the paste contains a metallic oxide such as NiO, and an amount of sacrificial pore-forming particles, such as carbon particles or polymer spheres, which are vaporized during sintering of the paste, resulting in a very porous connection having good electrical conductivity and good adhesion. A preferred level of pore-former in the paste is about 40 volume percent. On the cathode side, the paste contains a noble metal such as for example, gold, platinum, palladium or rhodium, and an amount of the sacrificial pore-forming particles. The paste may be applied to the surfaces in a grid pattern or, because the resulting contact is porous after sintering, it may be applied as a continuous layer.

Abstract: A modular fuel cell cassette for use in assembling a fuel cell stack comprising a metal separator plate and a metal cell-mounting plate joined at their edges to form a hollow cassette. A fuel cell subassembly is attached to the mounting plate and extends through an opening in the mounting plate. The plates include openings to form chimney manifolds for supply and exhaust of fuel gas to the anode and air to the cathode. A conductive interconnect element extends from the fuel cell subassembly to make contact with the next cassette in a stack. The anode openings in the mounting plate and separator plate are separated by spacer rings such that the cassette is incompressible. A fuel cell stack comprises a plurality of cassettes, the mounting plate of one cassette being attached to, and insulated from, the separator plate of the next-adjacent cassette by a dielectric seal surrounding the interconnect.

Abstract: A textured surface is formed on at least one of a fuel cell mounting plate or fuel cell subassembly to define a joint spacing between these two components. In a preferred embodiment, the textured surface comprises a plurality of dimples coined or otherwise formed in the metal mounting plate. The joint spacing improves the manufacturing and assembly process of the fuel cell cassettes through precise application and control of the brazing process which improves the braze joint strength while reducing material cost.

Abstract: A method for fuel cell system thermal management includes: maintaining a first zone at a first selected temperature range, maintaining a second zone at a second selected temperature range, and maintaining a third zone at a third selected temperature range. The second zone is in thermal communication with a first sensor and comprises a reformer, while the third zone is in thermal communication with a second sensor and comprises a fuel cell stack. The second selected temperature range is greater than the first selected temperature range, while the third selected temperature range is greater than the second selected temperature range.

Abstract: A method of operating a fuel cell includes the step of selectively connecting and disconnecting the fuel cell to at least one electrical load dependent at least in part upon at least one of a fuel cell voltage, a fuel cell current and a fuel cell temperature.

Abstract: A brazing alloy comprising elemental silver alloyed with elemental silicon in a silver/silicon ratio between about 95/5 and 99/1, preferably about 97/3. Small amounts of silicon alloyed with silver depress the alloy liquidus curve significantly, the liquidus temperature of a silver and silicon eutectic alloy being about 837° C. Brazing alloys in accordance with the invention are useful in bonding ceramics to ceramics, ceramics to metals, and metals to metals. Copper, vanadium, or other oxygen-reactive surface bonding elements may also be included. Silver/silicon alloys are useful in applications such as assembly of components of solid oxide fuel cells. A variety of silver/silicon alloy brazes can be used within the same fuel cell so that subsequent brazing can be performed without reliquifying a previous braze. A brazing alloy comprising elemental silver and ruthenium in a silver/ruthenium ratio between 97/3 and 99/1 is also included.

Abstract: A solid-oxide fuel cell system wherein a reformate combustor is disposed in the reformate flow path between a hydrocarbon reformer and a fuel cell stack. At system start-up, reformate is partially burned within the combustor by admitting combustion air, and the partially-burned reformate is passed through the anode chambers of the stack to warm the anodes. In addition, reformate is passed through a cathode-air heat exchanger to warm combustion air entering the cathode chambers of the stack. The combustor may continue to be supplied with a low level of air during steady-state operation of the SOFC, thereby providing a moist environment within the anode chambers to prevent coking of the anodes and providing additional heat to the reformate. The combustor decouples the reformer from the stack thermodynamically, permitting the reformer and the stack each to run in its own optimal temperature range.

Abstract: A minimum joint thickness can be assured by incorporating beads or particles having a diameter corresponding to the joint thickness desired and which are infusible at the brazing temperature. Preferably such particles are formed of high-melting metals, metal oxides, ceramics, or cermets and are mixed into the alloy paste prior to fusing. In a preferred embodiment, the particle-containing paste is mixed with a non-flux carrier to facilitate application to the elements to be brazed. Exemplary application methods may include painting, rolling, screening, or extrusion dispensing. Brazing alloys in accordance with the invention are useful in bonding ceramics to ceramics, ceramics to metals, and metals to metals.

Abstract: A method for improving the efficiency of a hydrocarbon catalytic reformer and close-coupled fuel cell system by recycling a percentage of the anode exhaust syngas directly into the reformer in a range between about 20% and about 60%. Oxygen is supplied to the reformer at start-up. Under equilibrium conditions, oxygen required for reforming of hydrocarbon fuel is derived entirely from endothermic reforming of water and carbon dioxide in the recycled syngas. Recycling of anode syngas into the reformer increases fuel efficiency, adds excess water to the reformate to increase protection against anode coking, and protects the fuel cell stack against air- and water-borne contaminants. A method for producing an excess amount of syngas for exporting for other purposes is also provided.