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: A polymer electrolyte membrane (PEM) fuel cell power plant is cooled evaporatively by a non-circulating pressurized water coolant system. The coolant system utilizes a hydrophobic porous plug for bleeding air from the coolant water while maintaining coolant back pressure in a coolant flow field of the system. Furthermore, there is a first method for identifying appropriate parameters of the hydrophobic porous plug for use with a known particular coolant system; and a second method for determining proper operating conditions for a fuel cell water coolant system which can operate with a hydrophobic porous plug closure having known physical parameters.

Abstract: A fuel cell voltage monitor (12a, 12b, 40, 140, 440) detects and may respond to, a problematic operating condition at or near a fuel cell (10) or within a subset (n) of fuel cells, as in a fuel cell stack assembly (110). Two or more co-planar, spaced voltage leads or contacts in a fuel cell plane, as at a separator plate, detect the presence of a voltage difference within the plate/plane as an indication of an operating problem at or near the fuel cell. Placement of such arrangements of at least two spaced voltage leads at various subset intervals (n), of fuel cells in a stack assembly allow monitoring for such problems throughout the stack assembly, either by analysis of voltage difference between co-planar leads at respective individual fuel cells or by comparison of voltage differences between aligned pairs of voltage leads at opposite ends of a subset.

Abstract: A fuel cell stack (31) includes a plurality of fuel cells (9) each having an electrolyte such as a PEM (10), anode and cathode catalyst layers (13, 14), anode and cathode gas diffusion layers (16, 17), and water transport plates (21, 28) adjacent the gas diffusion layers. The cathode diffusion layer of cells near the cathode end (36) of the stack have a high water permeability, such as greater than 3×10?4 g/(Pa s m) at about 80° C. and about 1 atmosphere, whereas the cathode gas diffusion layer in cells near the anode end (35) have water vapor permeance greater than 3×10?4 g/(Pa s m) at about 80° C. and about 1 atmosphere. In one embodiment, the anode gas diffusion layer of cells near the anode end (35) of the stack have a higher liquid water permeability than the anode gas diffusion layer in cells near the cathode end; a second embodiment reverses that relationship.

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: A fuel cell power plant (10) includes a fuel cell (12) having a membrane electrode assembly (MEA) (16), disposed between an anode support plate (14) and a cathode support plate (18), the anode and/or cathode support plates include a hydrophilic substrate layer (80, 82) having a predetermined pore size. The pressure of the reactant gas streams (22, 24) is greater than the pressure of the coolant stream (26), such that a greater percentage of the pores within the hydrophilic substrate layer contain reactant gas rather than water. Any water that forms on the cathode side of the MEA will migrate through the cathode support plate and away from the MEA. Controlling the pressure also ensures that the coolant water will continually migrate from the coolant stream toward the anode side of the MEA, thereby preventing the membrane from becoming dry. Proper pore size and a pressure differential between coolant and reactants improves the electrical efficiency of the fuel cell.

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: 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 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 polymer electrolyte membrane (PEM) fuel cell power plant is cooled evaporatively by a non-circulating pressurized water coolant system. The coolant system utilizes a hydrophobic porous plug for bleeding air from the coolant water while maintaining coolant back pressure in a coolant flow field of the system. Furthermore, there is a first method for identifying appropriate parameters of the hydrophobic porous plug for use with a known particular coolant system; and a second method for determining proper operating conditions for a fuel cell water coolant system which can operate with a hydrophobic porous plug closure having known physical parameters.

Abstract: A polymer electrolyte membrane (PEM) fuel cell power plant is cooled evaporatively by a non-circulating pressurized water coolant system. The coolant system utilizes a hydrophobic porous plug for bleeding air from from the coolant water while maintaining coolant back pressure in a coolant flow field of the system. Furthermore, there is a first method for identifying appropriate parameters of the hydrophobic porous plug for use with a known particular coolant system; and a second method for determining proper operating conditions for a fuel cell water coolant system which can operate with a hydrophobic porous plug closure having known physical parameters.

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: A polymer electrolyte membrane (PEM) fuel cell power plant is cooled evaporatively by a non-circulating pressurized water coolant system. The coolant system utilizes a hydrophobic porous plug for bleeding air from the coolant water while maintaining coolant back pressure in a coolant flow field of the system. Furthermore, there is a first method for identifying appropriate parameters of the hydrophobic porous plug for use with a known particular coolant system; and a second method for determining proper operating conditions for a fuel cell water coolant system which can operate with a hydrophobic porous plug closure having known physical parameters.

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: 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: 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 method of controlling an amount of liquid in a fuel cell includes increasing the oxygen utilization within the fuel cell to increase heat. The heat reduces the amount of liquid in the fuel cell. A disclosed example method includes decreasing a supply of air to the fuel cell to lower a fuel cell voltage by increasing the oxygen utilization. The example method includes maintaining an essentially electrical current density while decreasing the supply of air.

Abstract: A method and apparatus for mitigating decay of multiple membrane electrode assemblies (20) in a fuel cell stack (12). Each membrane electrode assembly (20) includes an anode (16) and a cathode (18) on respectively opposite sides of a proton exchange membrane (14). The positioning of a plane of potential change (Xo) is controlled to be/maintained outside the membrane and within the cathode of each membrane electrode assembly, both during regular electrical load cycling and during relatively idle operation of a primary electrical load (28) connected to the fuel cell stack. A determination (22, 24, 54, 50) of electrical demand on the fuel cell stack is reflective of either regular electrical load cycling or relatively idle operation, and during relatively idle operation a secondary electrical load (52) is connected (26, 24?) to the stack and/or a flow of air (36) to the cathode is regulated (62, 60) to maintain the plane of potential change (Xo) outside the membrane.