Abstract: A stack (10) of fuel cells (11) is provided with barriers (32) to prevent migration of a liquid electrolyte (such as phosphoric acid) out of the cells (11). The barrier (32) is secured within a step (34) defined within a land region (28) of a separator plate assembly (18) and extends from an edge (30) of the separator plate assembly (18) all or a portion of a distance between the edge (30) and a flow channel (24) defined within the separator plate assembly (18). The barrier (32) also extends away from the edge (30) a distance of between 0.051 and 2.0 millimeters (2 and 80 mils). The barrier (32) includes a hydrophobic, polymeric film (36), a pressure sensitive adhesive (38), as an assembly aid, and a fluoroelastomer bonding agent (40).

Abstract: A stack (10) of fuel cells (11) is manufactured with barriers (32) to prevent migration of a liquid electrolyte (such as phosphoric acid) out of the cells (11). The barrier (32) is secured within a step (34) formed within a land region (28) of a separator plate assembly (18) and extends from an edge (30) of the separator plate assembly (18) all or a portion of a distance between the edge (30) and a flow channel (24) defined within the separator plate assembly (18). The barrier (32) also extends away from the edge (30) a distance of between 0.051 and about 2.0 millimeters (about 2 and about 80 mils. The barrier (32) includes a hydrophobic, polymeric film (36), a pressure sensitive adhesive (38) as an assembly aid, and a fluoroelastomer bonding agent (40).

Abstract: An ammonia contact scrubber system (10) for removing ammonia from a fuel stream for a fuel cell (16) includes a contact scrubber (12) having a scrubber fuel inlet (14) and a scrubber fuel exhaust (20) for directing flow of the fuel stream through support material (24) within the scrubber (12) and into the fuel cell (16). An acid circulating loop (26) has an acid holding tank (28) holding a liquid acid solution (30), an acid feed line (32) secured in fluid communication between the holding tank (28) and a scrubber acid inlet (36) of the contact scrubber (12), an acid return (38) for returning the acid solution from the scrubber (12) to the acid holding tank (28), and an acid circulation pump (42) for pumping the acid solution (30) through the acid circulating loop (26) and through the support material (24) within the scrubber (12).

Abstract: A fuel cell separator plate assembly (20, 20a) includes a separator layer (22, 22a) and one or more reactant flow field layers (24, 24a, 26, 26a) comprising graphite flakes and a thermoplastic, hydrophobic resin which secures flow field layers on opposite sides of the separator layer. In another example, a separator plate assembly (20a) comprises a monolithic structure in which the separator portion (22a) and the flow field portions (24a, 26a) are all formed in a single piece of the same material. A method heats thermoplastic resin to its point of complete melting, then cools to its point where melting begins, increasing both electric and thermal conductivity. Methods include bonding under higher pressure than previously used, about 800 psi, or under pressures about 750 psi.

Abstract: A fuel cell separator plate assembly (20) includes a separator plate layer (22) and flow field layers (24, 26). In one disclosed example, the separator plate layer (22) comprises graphite and a hydrophobic resin. The hydrophobic resin of the separator plate layer (22) serves to secure the separator plate layer to flow field layers on opposite sides of the separator plate layer. In one example, at least one of the flow field layers (24, 26) comprises graphite and a hydrophobic resin such that the flow field layer is hydrophobic and nonporous. In another example, two graphite and hydrophobic resin flow field layers are used on opposite sides of a separator plate layer. One disclosed example includes all three layers comprising graphite and a hydrophobic resin.

Abstract: A method of heat treating a substrate for a fuel cell includes stacking substrates to form a group. A dimension is determined for a plate corresponding to a resulting mass that is less than a predetermined mass. The plate is arranged above the group to apply a weight of the plate to the group. The resulting masses for spacer plates and intermediate lifting plates, for example, are minimized to reduce the pressure differential between the bottom and top substrates in the heat treat assembly. In another disclosed method, a dimension for a plate, such as a top plate, is determined that corresponds to a resulting mass that is greater than a predetermined mass. The plate is arranged above the group to apply a weight of the plate to the group. The top plate resulting mass is selected to minimize a variation in the average pressure of the substrates throughout the heat treat assembly.

Abstract: An electrode substrate is disclosed that includes a plane and a through-plane direction. First and second carbon fibers are respectively arranged in the plane and through-plane direction. The substrate includes a thickness in the through-plane direction and the second fiber has a length less than the thickness. The first carbon fiber has a length greater than the thickness. In one example method of manufacturing the example substrate, PAN-based carbon fibers are blended with meso-phase pitch-based carbon fibers. A resin is applied to a non-woven felt constructed from the carbon fibers. The felt and resin are heated to a desired temperature to achieve a desired through-plane thermal conductivity.

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: A liquid electrolyte fuel cell power plant (6) includes a stack (7) of fuel cells (8) demarcated by fluid impermeable separator plates (19, 23) with additional wicking to ensure backflow of condensated electrolyte from a condensation zone (27) back through the active area of the fuel cells. Wicking material (49) is disposed in channels interspersed with reactant gas channels (20, 21); wicking material (54) is disposed in zones (53) formed within electrode substrates (16, 17); wicking material (58) is disposed on the base surface of reactant gas channels (20, 21); wicking material (62) is disposed between the ribs (50) of the separator plates (19, 23) and the adjacent surfaces of the substrates (16, 17); and wicking material (65) is formed as ribs on planar separator plates (19a, 23a), the spaces between the wicking ribs (65) comprising the reactant gas channels (20, 21).

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: 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: A method of making an electrochemical cell electrode substrate includes creating an aqueous or dry mixture of chopped carbon fibers, chopped cross-linkable resin fibers that are still fuseable after being formed into a felt, such as novolac, a temporary binder, such as polyvinyl alcohol fiber or powder, forming a non-woven felt from either an aqueous suspension of the aqueous mixture or an air suspension of the dry mixture, by a non-woven, wet-lay or dry-lay, respectively, felt forming process, a resin curing agent, such as hexamethylene tetramine may be included in the aqueous or dry mixture, or it may be coated onto the formed felt; pressing one or more layers of the formed felt for 1-5 minutes to a controlled thickness and a controlled porosity at a temperature at which the resin melts, cross-links and then cures, such as 150° C.-200° C.; and heat treating the pressed felt in a substantially inert atmosphere, first to 750° C.-1000° C. and then to 1000° C.-3000° C.

Abstract: An ammonia contact scrubber system (10) for removing ammonia from a fuel stream for a fuel cell (16) includes a contact scrubber (12) having a scrubber fuel inlet (14) and a scrubber fuel exhaust (20) for directing flow of the fuel stream through support material (24) within the scrubber (12) and into the fuel cell (16). An acid circulating loop (26) has an acid holding tank (28) holding a liquid acid solution (30), an acid feed line (32) secured in fluid communication between the holding tank (28) and a scrubber acid inlet (36) of the contact scrubber (12), an acid return (38) for returning the acid solution from the scrubber (12) to the acid holding tank (28), and an acid circulation pump (42) for pumping the acid solution (30) through the acid circulating loop (26) and through the support material (24) within the scrubber (12).

Abstract: A fuel cell (8a) having a matrix (11) for containing phosphoric acid (or other liquid) electrolyte with an anode catalyst (12) on one side and a cathode catalyst (13) on the other side includes an anode substrate (16a) in contact with the anode catalyst and a cathode substrate (17a) in contact with the cathode catalyst, the anode substrate being thicker than the cathode substrate by a ratio of between 1.75 to 1.0 and 3.0 to 1.0. Non-porous, hydrophobic separator plate assemblies (19) provide fuel flow channels (20) and oxidant flow channels (21) as well as demarcating the fuel cells.

Abstract: To evaporatively cool fuel cells, the pressure in steam carrying channels on one side of a hydrophobic porous liquid/vapor barrier layer disposed between adjacent fuel cells is reduced to below the vapor pressure of liquid water passing through liquid water carrying channels on the other side of the barrier layer, such as by using a vacuum pump. This causes some of the liquid water to boil and change to steam. The steam passes through the barrier layer into the steam channels and is carried out of the cells. The operating temperature of the fuel cell is adjusted by controlling the pressure within the steam channels, such as by controlling the amount of heat removed from the steam after it leaves the steam channels.

Abstract: Water transfer means (86) transfers fuel cell product water from a cathode water transport plate (34) to an anode water transport plate (23) of the same or a different fuel cell, wholly within a fuel cell stack (50), (disposed within each fuel cell of a fuel cell stack (50)). The water transfer means may be a very high permeability proton exchange membrane (21a), a water transfer band (90) such as silicon carbide particles, a porous water transfer zone (107), with or without a flow restrictor (109), internal water manifolds (112, 113) which extend through an entire fuel cell stack, or internal manifolds (112a, 112b, 112c, 112d, 113a, 113b, 113c, 113d) which extend only through groups of cells between solid plates (71).

Abstract: In a fuel cell for a fuel cell power plant having a PEM (9), a cathode comprising at least a catalyst (10) and a support substrate (17), possibly with a diffusion layer (16), on one side of the PEM, and an anode comprising at least an anode support substrate (14) and an anode catalyst (11) on the opposite side of the PEM, and a porous water transport plate having reactant gas flow field channels (31, 32) (21, 28) adjacent to each of said support substrates as well as water flow channels (22) in at least one of said water transport plates, the thermal conductance of the cathode is less than about one-half of the thermal conductance of the anode, and preferably less than one-quarter of the thermal conductance of the anode, to promote flow of water from the cathode to the anode and to the adjacent water transport plate, obviating the need, in some cases, for water or reactant pressure pumps.

Abstract: A fuel cell stack (50) includes fuel cells (16, 18, 19) with anode and cathode water transport plates (23, 31, 34, 37) having porosity of at least 50%, thereby to significantly increase the amount of water stored within the water transport plates when the stack is shut down, which doubles the heat of fusion as the ice in the pores melts during a startup following freeze. This extends the period of time before the water in the pores reaches a hard freeze at ?20° C. from 180 hours to 280 hours. A controller (60) controls the bypass (55) of a heat exchanger (54) to cause the temperature of the stack to reach a temperature sufficient to raise the sensible heat of the stack by 20%-40% above what it is with the fuel cell power plant operating steady state, prior to being shut down, thereby increasing the hours required for the fuel cell to cool down to 0° C. in ?20° C. environment from 60 hours to 90 hours, allowing easier startups when shut down for less than 90 hours.

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 stack (11) of fuel cells have water flow channels receiving water through a pump (33) from an accumulator (29) having double walls (63, 66) with vacuum insulation panels (VIPs) (65, 68) therebetween, auxiliary DC power source (80) (battery or supercapacitor) is disposed in a container (43) having double walls (81, 86) with VIPs (65, 68) encapsulated therebetween. A keep-warm heater (51) keeps the source warm enough for at least half power capacity, the source driving its own heater as well as a keep-warm heater (50) in the accumulator to keep the accumulator above freezing. A microwave heater (58) disposed in the accumulator distributes energy to melt ice using fuel cell stack power upon startup.