Abstract: A PEM fuel cell power plant includes fuel cells, each of which has a cathode reactant flow field plate which is substantially impermeable to fluids, a coolant source, and a fluid permeable anode reactant flow field plate adjacent to said coolant source. The anode reactant flow field plates pass coolant from the coolant sources into the cells where the coolant is evaporated to cool the cells. The cathode flow field plates prevent reactant crossover between adjacent cells. By providing a single permeable plate for each cell in the power plant the amount of coolant present in the power plant at shut down is limited to a degree which does not require adjunct coolant purging components to remove coolant from the plates when the power plant is shut down during freezing ambient conditions. Thus the amount of residual frozen coolant in the power plant that forms in the plates during shut down in such freezing conditions will be limited.

Abstract: During a process of shutting down a fuel cell power plant (11) the exits (28) of the anodes (14) are vented (76-77) under liquid (57). The liquid may be that of a coolant accumulator (57) of a fuel cell stack (12) cooled by conduction and convection of sensible heat into liquid coolant (FIG. 1) or evaporatively cooled (FIG. 4). The vent (77) may be under liquid all of the time (FIGS. 1, 3 and 4) or only after the stack has been drained of coolant (FIG. 2). The vent (77) may be the only vent for the anode exits (FIG. 3), or there may also be a purge vent valve (31) (FIGS. 1 and 4).

Abstract: The electrical output connections (155, 158) of a fuel cell stack (151) are short circuited (200; 211, 212) during start up from freezing temperatures. Before the stack is short circuited, fuel is provided in excess of stoichiometric amount for a limiting stack current, and oxidant is provided to assure stoichiometric amount for the limiting stack current.

Abstract: To mitigate bubble blockage in water passageways (78, 85), in or near reactant gas flow field plates (74, 81) of fuel cells (38), passageways are configured with (a) cross sections having intersecting polygons or other shapes, obtuse angles including triangles and trapezoids, or (b) hydrophobic surfaces (111), or (c) differing adjacent channels (127, 128), or (d) water permeable layers (93, 115, 116, 119) adjacent to water channels or hydrophobic/hydrophilic layers (114, 120), or (e) diverging channels (152).

Abstract: During fuel cell startup and shutdown or other power reduction transitions of a fuel cell power plant, the excess electric energy generated by consumption of reactants is extracted by a storage control (200) in response to a controller (185) as current applied to an energy storage system 201 (a battery). In a boost embodiment, an inductor (205) and a diode (209) connect one terminal (156) of the stack (151) of the battery. An electronic switch connects the juncture of the inductor and the diode to both the other terminal (155) of the stack and the battery. The switch is alternately gated on and off by a signal (212) from a controller (185) until sufficient energy is transferred from the stack to the battery. In a buck environment, the switch and the inductor (205) connect one terminal (156) of the stack to the battery. A diode connects the juncture of the switch with the inductor to the other terminal (155) of the fuel cell stack and the battery.

Abstract: A fuel cell (40) includes first and second catalysts (12?), (14?) secured to opposed surfaces of an electrolyte (16?); a first flow field (26?) secured in fluid communication with the first catalyst (12?) defining a plurality of flow channels (30A?, 30B?, 30C?, 30D?) between a plurality of ribs (32A?, 32B?, 32C?, 32D?, 32E?) of the first flow field (26?); and a backing layer (42) secured between the first flow field (26?) and the first catalyst (12?). The backing layer (42) includes a carbon black, a hydrophobic polymer, and randomly-dispersed carbon fibers (44). The carbon fibers (44) are at least twice as long as a width (46) of the flow channels (30A?, 30B?, 30C?, 30D?) defined in the adjacent first flow field (26?). The backing layer (42) replaces a known substrate (22) and diffusion layer (18).

Abstract: An inlet fuel distributor (10-10d) has a permeable baffle (39, 54, 54a, 60) between a fuel supply pipe (11, 83) and a fuel inlet manifold (12, 53, 53a, 63) causing fuel to be uniformly distributed along the length of the fuel inlet manifold. A surface (53, 68) may cause impinging fuel to turn and flow substantially omnidirectionally improving its uniformity. Recycle fuel may be provided (25, 71) into the flow downstream of the fuel inlet distributor. During startup, fuel or inert gas within the inlet fuel distributor and the fuel inlet manifold may be vented through an exhaust valve (57, 86) in response to a controller (58, 79) so as to present a uniform fuel front to the inlets of the fuel flow fields (58).

Abstract: A fuel cell stack (32) includes a plurality of fuel cells in which each fuel cell is formed between a pair of conductive, porous, substantially hydrophilic plates (17) having oxidant reactant gas flow field channels (12-15) on a first surface and fuel reactant gas flow field channels (19, 19a) on a second surface opposite to the first surface, each ˜f the plates being separated from a plate adjacent thereto by a unitized electrode assembly (20) including a cathode electrode (22), having a gas diffusion layer (GDL) an anode electrode (23) having a GDL with catalyst between each GDL and a membrane (21) disposed therebetween. Above the stack is a condenser (33} having tubes (34) that receive coolant air (39, 40} to condense water vapor out of oxidant exhaust in a chamber (43). Inter-cell wicking strips (26) receive condensate and conduct it along the length of the stack to all cells.

Abstract: A durable catalyst support/catalyst is capable of extended water gas shift operation under conditions of high temperature, pressure, and sulfur levels. The support is a homogeneous, nanocrystalline, mixed metal oxide of at least three metals, the first being cerium, the second being Zr, and/or Hf, and the third importantly being Ti, the three metals comprising at least 80% of the metal constituents of the mixed metal oxide and the Ti being present in a range of 5% to 45% by metals-only atomic percent of the mixed metal oxide. The mixed metal oxide has an average crystallite size less than 6 nm and forms a skeletal structure with pores whose diameters are in the range of 4-9 nm and normally greater than the average crystallite size. The surface area of the skeletal structure per volume of the material of the structure is greater than about 240 m2/cm3. The method of making and use are also described.

Abstract: The invention is a hydrogen passivation shut down system for a fuel cell power plant (10). An anode flow path (24) is in fluid communication with an anode catalyst (14) for directing hydrogen fuel to flow adjacent to the anode catalyst (14), and a cathode flow path (38) is in fluid communication with a cathode catalyst (16) for directing an oxidant to flow adjacent to the cathode catalyst (16) of a fuel cell (12). Hydrogen fuel is permitted to transfer between the anode flow path (24) and the cathode flow path (38). A hydrogen reservoir (66) is secured in fluid communication with the anode flow path (24) for receiving and storing hydrogen during fuel cell (12) operation, and for releasing the hydrogen into the fuel cell (12) whenever the fuel cell (12) is shut down.

Abstract: The direction of flow of purged fuel reactant gas (20) is sensed (38, 39, 44, 53, 54) to ensure it flows outwardly from a fuel cell stack (9) towards the ambient (21). If the purged fuel reactant. gas is not flowing outwardly, a signal (39) causes a controller (26) to open the circuit (35) thereby disconnecting the electrical load (33) from the fuel cell stack.

Abstract: A method for operating a fuel cell power plant to supply power to an internal load and an external load, includes the steps of evaluating power needs of the internal and external loads to determine a fixed IDC value sufficient to supply the needs; providing auxiliary power to the internal load and output power to the external load so as to maintain operation of the fuel cell power plant at the fixed IDC value; and adjusting at least one of the auxiliary power to the internal load and output power to the external load so as to maintain operation of the fuel cell power plant at the fixed IDC value. Operation within a preselected voltage range is also provided.

Abstract: During fuel cell startup and shutdown or other power reduction transitions of a fuel cell power plant, the excess electric energy generated by consumption of reactants is extracted by a storage control (200) in response to a controller (185) as current applied to an energy storage system 201 (a battery). In a boost embodiment, an inductor (205) and a diode (209) connect one terminal (156) of the stack (151) of the battery. An electronic switch connects the juncture of the inductor and the diode to both the other terminal (155) of the stack and the battery. The switch is alternately gated on and off by a signal (212) from a controller (185) until sufficient energy is transferred from the stack to the battery. In a buck environment, the switch and the inductor (205) connect one terminal (156) of the stack to the battery. A diode connects the juncture of the switch with the inductor to the other terminal (155) of the fuel cell stack and the battery.

Abstract: Water in a fuel cell accumulator is kept above freezing by a hydrogen/oxygen catalytic combustor fed hydrogen through a mechanical thermostatic valve in thermal communication with the container and connected to a hydrogen supply. The system includes an ejector hydrogen/oxygen combustor and a diffusion hydrogen/oxygen combustor for warming a medium within a container such as water in the accumulator of a fuel cell in response to a mechanic hydrostatic valve which conducts hydrogen to a combustor responsive to the temperature of the container.

Abstract: An example fuel cell assembly includes a separator plate. Non-porous and hydrophobic flow field layers are associated with the separator plate. An electrolyte retaining matrix comprises silicon carbide powder and has a mean particle size of about 3 microns and a thickness of about 0.05 mm Hydrophilic substrates are associated with catalyst layers. The hydrophilic substrates are about 70% porous and have a void volume that is about 40% filled with transferable phosphoric acid in an initial condition. A condensation zone cools a vapor passing from the assembly to less than about 140° C.

Abstract: Recycle fuel gas is provided (36) to an impeller (34, 34a) for application to the input (24) of the anode flow fields of a fuel cell stack (25). The impeller may be an ejector (34) having its primary input (33) connected to a source (11) of hydrogen and its secondary input (35) connected to the outlet (27, 37) of the fuel cells anode flow fields. The ejector outlet provides the minimum fuel flow required at the lowest power rating. The impeller may be an electrochemical hydrogen pump (34a) with a constant current generator (50) providing for a substantially constant recycle flow (the highest not more than double the lowest), and one pressure regulator (20) providing minimum flow of fresh fuel to the fuel inlets of the first stack. Pressure regulators (20, 21) control the amount of fresh fuel to the anode flow fields for power in excess of minimum power.

Abstract: A pair of reactant cover plates, e.g., fluid manifolds or protective covers (11, 12), on opposite sides of a fuel cell stack (7) are drawn to the fuel cells (14) and pressure plates (8) by tensioning lines, e.g., cables (23) or straps (23a), which may extend around structures, e.g., pins or extensions (11a, 12a; 11e, 12e) extending outwardly from the ends of the cover plates or guides (22a) on the stack, e.g., on the pressure plates in a closed loop, and are tensioned by a tensioning device, such as a turnbuckle (24).

Abstract: A fuel cell assembly (20) has a plurality of characteristics that extend the useful life of the assembly. In one example, flow field layers are non-porous and hydrophobic such that they have an acid absorption rate of less than about 0.10 mg/khr-cm2. An electrolyte retaining matrix has a reaction rate with phosphoric acid of less than about 0.010 mg/khr-cm2. Hydrophilic substrates associated with catalyst layers have an initial transferable phosphoric acid content of less than about 25 mg/cm2. A condensation zone provides an evaporative phosphoric acid loss rate that is less than about 0.17 mg/khr-cm2.

Abstract: A durable Pd-based alloy is used for a H2-selective membrane in a hydrogen generator, as in the fuel processor of a fuel cell plant. The Pd-based alloy includes Cu as a binary element, and further includes “X”, where “X” comprises at least one metal from group “M” that is BCC and acts to stabilize the ? BCC phase for stability during operating temperatures. The metal from group “M” is selected from the group consisting of Fe, Cr, Nb, Ta, V, Mo, and W, with Nb and Ta being most preferred. “X” may further comprise at least one metal from a group “N” that is non-BCC, preferably FCC, that enhances other properties of the membrane, such as ductility. The metal from group “N” is selected from the group consisting of Ag, Au, Re, Ru, Rh, Y, Ce, Ni, Ir, Pt, Co, La and In. The at. % of Pd in the binary Pd—Cu alloy ranges from about 35 at. % to about 55 at. %, and the at. % of “X” in the higher order alloy, based on said binary alloy, is in the range of about 1 at. % to about 15 at. %.

Abstract: A site management system (11) is provided for a power system (8) at site in a utility distribution grid (10). The power system (8) includes multiple fuel cell power plants, e.g., fuel cells, (18) and one or more loads (14), for selective connection/disconnection with the grid (10). The site management system (11) controls the power plants (18) in an integrated manner, alternatively in a grid connected mode and a grid independent mode. The multiple power plants (18) at the site may be viewed and operated as a unified distributed resource on the grid (10). The site management system (11) provides signals representative of the present power capability (Kw Capacity—88) of each of the power plants (18), and a signal (Total Kw Capacity—95) representative of the total present power capability at the site.