Abstract: A method of operating a fuel cell power plant (10) including a stack (11) of fuel cells having an anode catalyst layer and a cathode electrode (15) including a catalyst layer disposed on catalyst support material is characterized by, during normal operation of said power plant, adjusting the voltage of the stack to be substantially equal to or less than a predetermined maximum voltage for the temperature of the stack. Further, said step of adjusting comprises adjusting the stack voltage to the lesser of: a) a predetermined voltage above which corrosion of catalyst support material is significant and below which corrosion of catalyst support material is insignificant at the temperature of the stack; and b) a predetermined voltage above which dissolution of catalyst is significant and below which dissolution of the catalyst is insignificant at the temperature of the stack.

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 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: The controller (185) of a fuel cell stack (151) in a vehicle (150) responds to lower demand to cause a diverter (172) to direct all air from the cathodes (19) except as required to generate sufficient power to limit cell voltage to a safe idle voltage threshold, cause storage in an energy storage system (201) sufficient to limit cell voltage to the idle voltage threshold unless SOC is too high, connects a voltage limiting load (220) to the stack sized to consume all power not consumed by auxiliary BOP, or, for longer idles, air-starves the stack and powers BOP from storage. In response to increase in a demand signal, the controller causes flow of all air to the cathodes. In response to an off signal (223) or a start signal (193) the controller causes a shutdown routine or a startup routine in each of which all generated power is stored to maintain fuel cell voltage below a threshold, or is consumed in the voltage limiting load.

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 power plant (5) includes a stack (6) of fuel cells, each of which have an anode (9), a cathode (10), and a PEM (11) disposed between the anode and the cathode. A controller (17) recognizes an indication (67) of no load demand (68) by a load (59), to operate (45) an air recycle loop (44-46) utilizing the process air blower (35) and transfer the power output (57) of the stack from the load (59) to an auxiliary load (60), comprising a resistance which will consume a predetermined small amount of power in response to the current applied thereto, when the stack operates at a critical voltage above which fuel cell corrosion is unacceptable. Fuel and air will also be reduced (16, 40). The controller may cause increased cathode recycle when the critical voltage is reached and increased air when the voltage is a fraction of a volt below the critical voltage.

Abstract: Fuel cell stacks (20) include fuel cells (22) in which internal pressure on membranes (28), caused by adjacent cross points (19) or ribs (9, 17) of gas flow field plates (7, 33) is reduced by lowering the axial load holding the stack together, after an initial high axial load, that establishes minimal possible internal resistance, has been held for between a few hours and 20 hours. The need for robust axial load restraints is also reduced. Pressure of cross points (19) can also be spread by stiffening components or adding stiffeners.

Abstract: A process for shutting down a fuel cell power plant (5) shuts off (40) process air, recycles (44-46) air exhaust 42 to air inlets 34, and connects an auxiliary load to the stack (6). Coulombs are counted by integrating (17) current (73) or voltage (75) to the load to determine when all oxygen in the air side (10, 27, 30, 34, 42, 44-47) of the power plant is consumed and a desired concentration of hydrogen is transferred to the air side of the power plant. The speed of the shutdown processes may be increased by increasing fuel pressure (15) or adding a battery (78) in series with the auxiliary load.

Abstract: The controller (185) of a fuel cell stack (151) in a vehicle (150) responds to lower demand to cause a diverter (172) to direct all air from the cathodes (19) except as required to generate sufficient power to limit cell voltage to a safe idle voltage threshold, cause storage in an energy storage system (201) sufficient to limit cell voltage to the idle voltage threshold unless SOC is too high, connects a voltage limiting load (220) to the stack sized to consume all power not consumed by auxiliary BOP, or, for longer idles, air-starves the stack and powers BOP from storage. In response to increase in a demand signal, the controller causes flow of all air to the cathodes. In response to an off signal (223) or a start signal (193) the controller causes a shutdown routine or a startup routine in each of which all generated power is stored to maintain fuel cell voltage below a threshold, or is consumed in the voltage limiting load.

Abstract: The invention is a hydrogen passivation shut down system for a fuel cell power plant (10, 200). During shut down of the plant (10, 200), hydrogen fuel is permitted to transfer between an anode flow path (24, 24?) and a cathode flow path (38, 38?) while a low-pressure hydrogen generator (202) selectively generates an adequate amount of hydrogen and directs flow of the low-pressure hydrogen into the fuel cell (12?) downstream from a hydrogen inlet valve (52?) to maintain the fuel cell (12?) in a passive state.

Abstract: The invention is a hydrogen passivation shut down system for a fuel cell power plant (10, 200). During shut down of the plant (10, 200), hydrogen fuel is permitted to transfer between an anode flow path (24, 24?) and a cathode flow path (38, 38?). A passive hydrogen bleed line (202) permits passage of a smallest amount of hydrogen into the fuel cell (12?) necessary to maintain the fuel cell (12?) in a passive state. A diffusion media (204) may be secured in fluid communication with the bleed line (202) to maintain a constant, slow rate of diffusion of the hydrogen into the fuel cell (12?) despite varying pressure differentials between the shutdown fuel cell (12?) and ambient atmosphere adjacent the cell (12?).

Abstract: A method of operating a fuel cell power plant (10) including a stack (11) of fuel cells having an anode catalyst layer and a cathode electrode (15) including a catalyst layer disposed on catalyst support material is characterized by, during normal operation of said power plant, adjusting the voltage of the stack to be substantially equal to or less than a predetermined maximum voltage for the temperature of the stack. Further, said step of adjusting comprises adjusting the stack voltage to the lesser of: a) a predetermined voltage above which corrosion of catalyst support material is significant and below which corrosion of catalyst support material is insignificant at the temperature of the stack; and b) a predetermined voltage above which dissolution of catalyst is significant and below which dissolution of the catalyst is insignificant at the temperature of the stack.

Abstract: The invention is a hydrogen passivation shut down system for a fuel cell power plant (10, 200). During shut down of the plant (10, 200), hydrogen fuel is permitted to transfer between an anode flow path (24, 24?) and a cathode flow path (38, 38?). A controlled-oxidant flow device (209) near an oxygen source (58?) permits a minimal amount of atmospheric oxygen to enter the power plant (200) during shut down to equalize pressure between ambient atmosphere and the flow paths (24?, 28?) and to keep limited atmospheric oxygen entering the power plant (200) through the device (209) as far as possible from fuel cell flow fields (28?, 42?). A non-leaking hydrogen inlet valve (202), a non-leaking cathode exhaust valve (208), and a combined oxidant and fuel exhaust line (206) also minimize penetration of oxygen into the shut down power plant (200).

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 fuel cell includes an electrode assembly having an electrolyte between a cathode catalyst and an anode catalyst, and a flow field plate having a channel for delivering a reactant gas to the electrode assembly. The flow field plate includes a channel having a channel inlet. A porous diffusion layer is located between the electrode assembly and the flow field plate. The porous diffusion layer includes a first region near the channel inlet and a second region downstream from the first region relative to the channel inlet. The first region includes a filler material that partially blocks pores of the first region such that the first region has a first porosity and the second region has a second porosity that is greater than the first porosity.

Abstract: In a fuel cell stack, an inlet fuel distributor (15, 31, 31a, 31b) comprises a plurality of fuel distributing passageways (17-23, 40-47, 64) of substantially equal length and equal flow cross section to uniformly distribute fuel cell inlet fuel from a fuel supply conduit (13, 14, 50) to a fuel inlet manifold (28). The conduits may be either channels (40-47; 64) formed within a plate (39) or tubes (17-23). The channels may have single exits (65) or double exits (52, 53) into the fuel inlet manifold.

Abstract: Fuel cell stacks (20) include fuel cells (22) in which internal pressure on membranes (28), caused by adjacent cross points (19) or ribs (9, 17) of gas flow field plates (7, 33) is reduced by lowering the axial load holding the stack together, after an initial high axial load, that establishes minimal possible internal resistance, has been held for between a few hours and 20 hours. The need for robust axial load restraints is also reduced. Pressure of cross points (19) can also be spread by stiffening components or adding stiffeners.

Abstract: A process for shutting down a fuel cell power plant (5) shuts off (40) process air, recycles (44-46) air exhaust 42 to air inlets 34, and connects an auxiliary load to the stack (6). Coulombs are counted by integrating (17) current (73) or voltage (75) to the load to determine when all oxygen in the air side (10, 27, 30, 34, 42, 44-47) of the power plant is consumed and a desired concentration of hydrogen is transferred to the air side of the power plant. The speed of the shutdown processes may be increased by increasing fuel pressure (15) or adding a battery (78) in series with the auxiliary load.

Abstract: A fuel cell power plant (5) includes a stack (6) of fuel cells, each of which have an anode (9), a cathode (10), and a PEM (11) disposed between the anode and the cathode. A controller (17) recognizes an indication (67) of no load demand (68) by a load (59), to operate (45) an air recycle loop (44-46) utilizing the process air blower (35) and transfer the power output (57) of the stack from the load (59) to an auxiliary load (60), comprising a resistance which will consume a predetermined small amount of power in response to the current applied thereto, when the stack operates at a critical voltage above which fuel cell corrosion is unacceptable. Fuel and air will also be reduced (16, 40). The controller may cause increased cathode recycle when the critical voltage is reached and increased air when the voltage is a fraction of a volt below the critical voltage.

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.