摘要:
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′).
摘要:
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′).
摘要:
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.
摘要:
Fuel cells (38) have minute water passageways (67) that provide water through one or both reactant gas flow field plates (74, 82) of each fuel cell, whereby the fuel cell is cooled evaporatively. The water passageways (67; 78, 85; 78a, 85a) may be vented by a porous plug (69), or by a microvacuum pump (89) that does not pump any water from the passageways, or simply vented (99) to atmosphere. A condenser (59) may have a contiguous reservoir (64); the condenser (59) may be vertical, such as a vehicle radiator (FIG. 1), or may be horizontal, contiguous with the top of the fuel cell stack (37, FIG. 5). The passageways may be grooves (76, 77; 83, 84) in the reactant gas flow plates (75, 81) or the passageways may comprise a plane of porous hydrophilic material (78a, 85a) contiguous with substantially the entire surface of one or both of the reactant gas flow field plates.
摘要:
Fuel cells (38) have water passageways (67; 78, 85; 78a, 85a) that provide water through reactant gas flow field plates (74, 81) to cool the fuel cell. The water passageways 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 reactant air exhaust, may have a contiguous reservoir (64, 128), may be vertical, (a vehicle radiator, FIG. 2), may be horizontal, contiguous with the top of the fuel cell stack (37, FIG. 5), or below (124) the fuel cell stack (120). The passageways may be grooves (76, 77; 83, 84) or may comprise a plane of porous hydrophilic material (78a, 85a) contiguous with substantially the entire surface of one or both of the reactant gas flow field plates. Air flow in the condenser may be controlled by shutters (155). The condenser may be a heat exchanger (59a) having freeze-proof liquid flowing through a coil (161) thereof, the amount being controlled by a valve (166). A deionizer (175) may be used.
摘要:
A fuel cell power plant (19, 19a) has a plurality of fuel cells (70, 70a, 70c) arranged in a stack (20, 20c), each fuel cell having porous, at least partially hydrophilic water transport plates (75, 81) with fuel (74) and oxidant (82) reactant gas channels, there being water channels (78, 85, 78a, 85a, 78c, 85c) exchanging water with the water transport plates. On shut down, water is retained in the water channels and water transport plates by means of either a micro vacuum pump (46), one or two valves (89, 90, 118, 120), a check valve (95, 99), capillary force in the water channels to prevent water from entering the reactant channels which, if frozen, could block flow of reactant gas upon startup.
摘要:
A fuel cell power plant (19, 19a) has a plurality of fuel cells (70, 70a, 70c) arranged in a stack (20, 20c), each fuel cell having porous, at least partially hydrophilic water transport plates (75, 81) with fuel (74) and oxidant (82) reactant gas channels, there being water channels (78, 85, 78a, 85a, 78c, 85c) exchanging water with the water transport plates. On shut down, water is retained in the water channels and water transport plates by means of either a micro vacuum pump (46), one or two valves (89, 90, 118, 120), a check valve (95, 99), capillary force in the water channels to prevent water from entering the reactant channels which, if frozen, could block flow of reactant gas upon startup.
摘要:
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.
摘要:
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.
摘要:
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.