Abstract: A fuel cell power plant (36) has vertical fuel cells (102) each sharing a half of a hybrid separator plate (100) which includes a solid fuel flow plate (105) having horizontal fuel flow channels (106) on one surface and coolant channels (108) on an upper portion of the opposite surface, bonded to a plain rear side of a porous, hydrophilic oxidant flow field plate (115) having vertical oxidant flow channels (118). Coolant permeates through the upper portion of the porous, hydrophilic oxidant flow field plates and enters the oxidant flow channels, where it evaporates as the water trickles downward through the oxidant flow field channels, thereby cooling the fuel cell.

Abstract: Coolant velocity greater than zero everywhere within the coolant channels (78, 85) of fuel cells (38) in a fuel cell stack (37) is assured by providing a flow of biphase fluid in the coolant channels, the flow being created by the outflow of a condenser (59). Positive pressure is applied to the coolant inlet (66) of the coolant channels. Biphase flow from an oxidant exhaust condenser, which may be a vehicle radiator (120), renders the coolant return flow more freeze tolerant. Using biphase flow within the coolant channels eliminates the need for a bubble-clearing liquid pump and reduces liquid inventory and other plumbing; this makes the fuel cell power plant more freeze tolerant.

Abstract: Fuel cells (38) have passageways (83, 84) that provide water through one or both reactant gas flow field plates (75, 81) of each fuel cell, whereby the fuel cell is cooled evaporatively. The water passageways may be vented by a porous plug (not shown), or by a microvacuum pump (89). A condenser (59) may have a reservoir (64); the condenser (59) may be a vehicle radiator. A highly water permeable wicking layer (90) is disposed adjacent to one or both water passageways (83, 84) which exist between individual fuel cells (38). The passageways may be flow-through passageways (83) (FIG. 5) or they may be interdigitated passageways (83a, 83b) (FIG. 6) in order to increase the flow of water-purging air through the wicking layer (90) utilized to clear the stack of water during shutdown in cold environments.

Abstract: Coolant velocity greater than zero everywhere within the coolant channels (78, 85) of fuel cells (38) in a fuel cell stack (37) is assured by providing a flow of gas in the coolant channels, the flow being created by gas pressure from a source (92) of pressurized gas, an oxidant reactant air pump (52), a source (75) of hydrogen-containing fuel, or the fuel outlet (47), or the outflow of a condenser (59). Positive pressure may be applied to the coolant inlet (66) or negative pressure from an eductor (97) may be applied to a gas outlet (90) of the coolant channels, or both. Using gas to induce flow within the coolant channels eliminates the need for a bubble-clearing liquid pump and reduces liquid inventory and other plumbing; this makes the fuel cell power plant more freeze tolerant. Biphase flow from the condenser, which may be a vehicle radiator (120), renders the coolant return flow more freeze tolerant. Separate cooler plates (122) may be used with a coolant management system (125).

Abstract: In a proton exchange membrane fuel cell power plant (9) in which each fuel cell (11) employs reactant gas flow field channels (51) extending inwardly from a surface of a conductive, hydrophilic reactant gas flow field plate (50), for at least one of the reactants of the fuel cell, a region (63) of the reactant gas flow field channels is substantially shallower than the remaining portion (60) of the flow field channels thereby decreasing resistance to a gas phase mass transfer from the wetted walls of the flow field plate to the gas in the region (63); the resulting increase in thickness of the web (58) adjacent the region (63) reduces the resistance to liquid water transport from the first coolant channel (52) to the inlet edge (55) of the plate (50) providing a higher evaporation rate into the reactant gas in the shallow region (63).

Abstract: A fuel cell for a fuel cell power plant having gas diffusion layers which do not have microporous layers, includes a PEM (9), a cathode comprising at least a cathode catalyst (10) and a gas diffusion layer (17) on one side of the PEM, and an anode comprising at least an anode catalyst (11) and a gas diffusion layer (14) 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 conductivity of the cathode and/or the anode gas dif- fusion layers is less than about one-quarter of the thermal conductivity of conventional gas diffusion layers, less than about 0.25 W/m/K, to promote flow of water from the cathodes to the anodes and to the adjacent water transport plates, during start-up at normal ambient temperatures (lower than normal PEM fuel cell operating temperatures).

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) intersecting polygons, obtuse angles including triangles, 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).

Abstract: Water passageways (67; 78, 85; 78a, 85a) that provide water through reactant gas flow field plates (74, 81) to cool the fuel cells (38) may be grooves (76, 77; 83, 84) or may comprise a plane of porous hydrophilic material (78a, 85a), may be vented to atmosphere (99) by a porous plug (69), or pumped (89, 146) with or without removing any water from the passageways. A condenser (59, 124) receives exhaust of reactant air that evaporatively cools the stack (37), and may have a contiguous reservoir (64, 128), be vertical (a vehicle radiator, FIG. 2), be horizontal across the top of the stack (37, FIG. 5), or below (124) the stack (120). Condenser air flow may be controlled by shutters (155), or by a controlled, freeze-proof heat exchanger (59a). A deionizer (175) may be used. Sensible heat transferred into the water is removed by a heat exchanger 182; a controller (185) controls water flow (180) and temperature as well as air flow to provide predetermined allocation of cooling between evaporative and sensible.

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 stack (10) is operated with a low air utilization which is very low when the stack is providing low current density, and is operated with air utilization increasing as a function of current density above a predetermined current density.

Abstract: A device that is useful for managing moisture content within a fuel cell assembly (24) includes a hydrophilic layer (46) between a solid reactant distribution plate layer and a hydrophobic layer (38) adjacent to a catalyst layer (34). In disclosed examples, the hydrophilic layer (46) is positioned relative to the reactant distribution plate to have a flow field configuration similar to that of the reactant distribution plate so that the hydrophilic layer does not interfere with reactant flow through the hydrophobic layer to the catalyst layer. A disclosed example includes a reactant distribution plate comprising a solid, non-porous material and the hydrophilic material to establish the hydrophilic layer (46). In another example, the hydrophilic layer (46) is applied to, secured to or positioned against of ribs of the reactant distribution plate.

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: A fuel cell system includes a fuel cell, a controller, a resistance sensor, and a regulator. The fuel cell has a cathode plate, an anode plate, and an ion-exchange membrane interposed between the cathode plate and the anode plate. The controller is for controlling a gas flow rate to the anode plate. The resistance sensor is coupled to the fuel cell for measuring a resistance of the fuel cell. The regulator is coupled to the controller and coupled to the anode plate for regulating the gas flow to the anode plate. The controller receives a signal from the resistance sensor and is configured to control the regulator to adjust the gas flow to the anode plate based on the signal from the resistance sensor.

Abstract: Fuel cell systems (100, 400) and related methods involving accumulators (106, 200, 300, 406) with multiple regions (R1, R2; R1?, R2?) of differing water fill rates are provided. At least one accumulator region with a relatively more-rapid fill rate (R2; R2?) than another accumulator region (R1; R1?) is drained of water at shutdown under freezing conditions to allow at least that region to be free of water and ice. That region is then available to receive water from and supply water to, a fuel cell (102; 402) nominally upon start-up. The region having the relatively more-rapid fill rate (R2; R2?) may typically be of relatively lesser volume, and may be positioned either relatively below or relatively above the other region(s).

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: A fuel cell includes a first flow field plate for an anode side and a second flow field plate for a cathode side where each of the first flow field plates include channels configured to provide matching interdigitated flow fields. The fuel cell includes the first flow plate that receives fuel and a second flow plate arranged on an opposite side of the polymer electrolyte membrane for receiving an oxidant. Each fuel flow plate includes ribs that separate inlet channels from outlet channels. Inlet flow entering the inlet channel is directed over these ribs into an adjacent outlet channel. The outlet channel then provides for outlet flow of the fuel, oxidant and water. Because a solid plate polymer electrolyte fuel cell does not include flow field plates having a porous configuration, water management is difficult to balance and is accomplished through the polymer electrolyte membrane.

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: 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: 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) intersecting polygons, obtuse angles including triangles, 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).

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.