Abstract: A first AC power source comprising a power plant (18), and a second power source, typically grid (10), are normally connected via a high speed isolation switching means (19) to provide sufficient AC power to a critical load (14). The power plant (18) comprises a power generating means, e.g. a fuel cell, (60) and a power conditioning system (PCS) (62) having an inverter (64). Power assurance means (65; 10?, 66, 64, 70; 74, 75) is/are operatively connected to at least one of the first and second power sources to enhance an even and continuous supply of power to the critical load (14). The power assurance means (65; 10?, 66, 64, 70; 74, 75) is/are operatively connected to the PCS inverter (64), and may be one, or a combination of, a surge suppression means (65), a double-conversion power connection means (10?, 66, 64, 70) having a rectifier (66); and/or stored energy means (74), such as a capacitor (75).

Abstract: A fuel cell system having a stack of proton exchange membrane fuel cells is operated in sub-freezing temperatures by draining any liquid water from the fuel cell water flow passages upon or after the previous shut-down of the stack before freezing can occur, and, thereafter a) starting-up the stack by directing fuel and oxidant reactants into the cell and connecting a load to the stack; b) using heat produced by the stack to increase the operating temperature of the stack to melt ice within the stack; and, c) upon the stack operating temperature reaching at least 0° C., circulating anti-freeze through stack coolers to maintain the temperature of the stack low enough to maintain a sufficiently low water vapor pressure within the cells to prevent cell dry out for at least as long as there is insufficient liquid water to circulate through the water flow passages.

Abstract: An auxiliary load (148) for a fuel cell stack (102) is alternatively connected and disconnected from the fuel cell external circuit (177, 178) by a switch (200) in response to a switch control (201), repetitively, during startup and shutdown. The switch may be an insulated gate bipolar transistor (208) which is turned on and off by hunting between an upper limit voltage (207) and a lower limit voltage (208), which may be performed by compare circuits (205, 206), by the controller (202), or by commercially available voltage responsive hysteresis switches. Schedules of duty cycle as a function of cell stack voltage for startup (212) and shutdown (213) control a pulse width modulator (215) which operates the switch. Controls (229, 231) may limit the modulation so that the auxiliary load does not overheat, in response to temperature (221) of the load or a voltage/power model (235). The auxiliary load may comprise a heater in a water accumulator (247), an air intake (257) or an enthalpy recovery device (262).

Abstract: In a fuel cell stack (11a), a larger number of fuel cells (18–21, 33–36) are interposed between successive cooler plates (13–15) without creating excessively high temperatures in those fuel cells (33–36) which are remote from the cooler plates, by virtue of increased air flow in air flow field channels (30a) which are deeper in fuel cells (30–36) remote from the cooler plates, compared with the flow field channels (30, 30b) which are in fuel cells (18–21) adjacent to the cooler plates. The thickness of air flow field plates (29b) may be increased to accommodate the increased depth of the air flow channels (30a). Fuel cells (18a) adjacent the cooler plate may have air flow field channels (30b) which are more shallow than normal whereby increased air utilization therein will be balanced by decreased air utilization in the cells (33–36, 33a) having deeper air flow channels (30a); in this case, the channels (30a) may be normal or deeper than normal.

Abstract: An arrangement and process are provided for regulating the humidification or dew point of inlet air supplied (124, 224, 324, 424) to combustion-supported reaction means (20, 120) of a fuel processing system in a fuel cell power plant (110, 210, 310, 410). In addition to flowing exhaust gas(es) (28, 128) in heat and energy exchange relation with inlet air through a primary energy recovery device (ERD) (30) of the gas/gas type, a supplemental ERD (50) of the gas/liquid (water) type uses water temperature to passively condense moisture from a gas stream, either of inlet air or of exhaust gas, to regulate the dew point of the air supplied to the combustion-supported reaction means (20, 120). The supplemental ERD (50) may have a gas channel (134) and a water channel (132) separated by an enthalpy exchange barrier (136), and may be relatively upstream or downstream of the primary ERD (30) relative to the flow of inlet air through the latter to regulate dew point indirectly or directly, respectively.

Abstract: Method and apparatus are provided for removing contaminants from a hydrogen processor feed stream, as in a fuel cell power plant (110). Inlet oxidant (38), typically air, required by a catalytic hydrogen processor (34) in a fuel processor (14) for a fuel cell stack assembly (12) in the power plant (110), may contain contaminants such as SO2 and the like. A cleansing arrangement, which includes an accumulator/degasifier (142, 46) acting as a scrubber, and possibly also a water transfer device (118), receives the inlet oxidant and provides the desired cleansing of contaminants. Water in the water transfer device and in the accumulator/degasifier serves to dissolve the water-soluble contaminants and cleanse them from the oxidant stream. The cleansed oxidant stream (138?) is then delivered to the hydrogen processor and to the fuel cell assembly, with minimal inclusion of detrimental contaminants such as sulfur.

Abstract: The heat from various portions of a fuel cell power plant (110) are redistributed in a manner allowing desired modification of/to the heat removal means (152,156), e. g., radiator (152), included in the coolant loop for the fuel cell stack assembly (CSA) (12). A humidifier (70) added in the coolant loop (114) and the inlet oxidant (air) stream (134?) serves to relatively increase the humidification of the inlet air while removing heat from the coolant prior to entering the CSA (12). The combined effects are to relatively increase the temperature of the coolant exiting the CSA without similarly increasing the temperature of the coolant entering the CSA, and to relatively increase the temperature differential (“pinch”) between the coolant entering the heat removal means and the cooling air of the heat removal means (152, 156). This latter effect permits a relative reduction in the size/capacity of the heat removal means (152, 156).

Abstract: During startup or shutdown of a fuel cell power plant, the electric energy generated by consumption of reactants is extracted by a storage control (200) in response to a controller (185) as current applied to an energy storage system 201 (a battery). In a boost embodiment, an inductor (205) and a diode (209) connect one terminal (156) of the stack (151) of the battery. An electronic switch connects the juncture of the inductor and the diode to both the other terminal (155) of the stack and the battery. The switch is alternately gated on and off by a signal (212) from a controller (185) until sufficient energy is transferred from the stack to the battery. In a buck environment, the switch and the inductor (205) connect one terminal (156) of the stack to the battery. A diode connects the juncture of the switch with the inductor to the other terminal (155) of the fuel cell stack and the battery.

Abstract: A method for operating a fuel cell power plant to provide end-use electricity, end-use heat and end-use reformate includes the steps of providing a fuel cell power plant that consumes reformate to provide electricity and heat, said fuel cell power plant having a nominal reformate flow rate and including a fuel processor system for generating reformate from a hydrocarbon fuel; operating the fuel processor system so as to provide a reformate flow at a rate greater than the nominal reformate flow rate; operating the fuel cell power plant using a first portion of the reformate flow to generate the electricity and the heat, the first portion being less than or equal to the nominal reformate flow rate; and providing a second portion of the reformate flow as the end-use reformate.

Abstract: A fuel cell power plant system includes the ability to operate an enthalpy recovery device even under cold conditions. A bypass arrangement allows for selectively bypassing one or more portions of the enthalpy recovery device under selected conditions. In one example, the enthalpy recovery device is completely bypassed under selected temperature conditions to allow the device to freeze and then later to be used under more favorable temperature conditions. In another example, the enthalpy recovery device is selectively bypassed during a system startup operation. One example includes a heater associated with the enthalpy recovery device. Another example includes preheating oxidant supplied to one portion of the enthalpy recovery device.

Abstract: A PEM fuel cell system (19) has a multifunction oxidant manifold (98) disposed contiguously beneath a fuel cell stack (20), serving as coolant accumulator (28). An electric heater (45) is powered by the fuel cell electrical output (47, 51) during frozen startup. Auxiliary pump (54) and conduits (55, 57, 58) forces water (28) above oxidant pressure in upper coolant manifold (41), into the oxidant flow fields to be warmed before flowing from the oxidant exhaust to the accumulator to melt additional ice. Alternatively, melted coolant is forced by oxidant pressure into coolant channels for heating. Conduit (61) conducts coolant from the coolant flow fields to the accumulator. A condensing heat exchanger (65) embedded in accumulator coolant receives oxidant exhaust. A condensing heat exchanger (70) has cold inlet air (75) and warm moist oxidant exhaust (72) on opposite sides, condensing liquid into the accumulator.

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 fuel cell (12) whenever the fuel cell (12) is shut down.

Abstract: Method and apparatus are provided for removing contaminants from a hydrogen processor feed stream, as in a fuel cell power plant (110). Inlet oxidant (38), typically air, required by a catalytic hydrogen processor (34) in a fuel processor (14) for a fuel cell stack assembly (12) in the power plant (110), may contain contaminants such as SO2 and the like. A cleansing arrangement, which includes an accumulator/degasifier (142, 46) acting as a scrubber, and possibly also a water transfer device (118), receives the inlet oxidant and provides the desired cleansing of contaminants. Water in the water transfer device and in the accumulator/degasifier serves to dissolve the water-soluble contaminants and cleanse them from the oxidant stream. The cleansed oxidant stream (138?) is then delivered to the hydrogen processor and to the fuel cell assembly, with minimal inclusion of detrimental contaminants such as sulfur.

Abstract: A freeze tolerant fuel cell power plant (10) includes at least one fuel cell (12), a coolant loop (42) having a porous water transport plate (44) secured in a heat and mass exchange relationship with the fuel cell (12) and a coolant pump (46) for circulating a coolant through the plate (44) and for transferring water into or out of the plate (44) with the coolant. A coolant heat exchanger (52) removes heat from the coolant, and an accumulator (66) stores the coolant and fuel cell product water and directs the product water out of the accumulator (66). The coolant is a two-component mixed coolant liquid circulating through the coolant loop (42) consisting of between 80 and 95 volume percent of a low freezing temperature water immiscible fluid component and between 5 and 20 volume percent of a water component.

Abstract: A fuel cell power plant (10) having a fuel concentration sensor cell (54) is disclosed for detecting a concentration of fuel in a fuel cell (12) of the plant (10). A portion of a fuel exhaust stream is directed to flow through the sensor cell (54) adjacent to a membrane electrode assembly (60) of the sensor cell (54). A power circuit (62) may or may not deliver an electrical current to the cell (12), while changes in voltage across the cell (12) that are proportional to changes in hydrogen concentrations within the fuel exhaust stream are detected by a detector (68) which communicates the changes to a controller (108) for controlling a rate of fuel supply to the fuel cell (12). A porous sensor water transport plate (74) cools, humidifies delivers and removes liquid from the sensor cell (12).

Abstract: A fuel gas-steam reformer assembly, preferably an autothermal reformer assembly, for use in a fuel cell power plant, includes a catalyst bed which is formed from a cylindrical monolithic open cell foam body. The foam body is preferably formed from a high temperature material such as stainless steel, nickel alloys and iron-aluminum alloys, or from a ceramic material. The foam body includes open cells or pores which are contained within the metal or ceramic lattice. The lattice is coated with a porous wash coat which serves as a high surface area substrate onto which catalysts used in the reformer are applied. The foam body has an inlet end into which a mixture of fuel, steam and air is fed to begin the reforming process. An inlet portion of the foam body may be provided with an iron oxide and/or noble metal catalyst and the remainder of the foam body may be provided with a nickel and/or noble metal catalyst.

Abstract: A vane (31) at the juncture of orthogonal conduits (25–28) allows flow of air to and from the air inlet/outlet manifold (12) of a fuel cell stack (11) when it is disposed in a first position, and totally blocks the conduits (25, 26) so as to isolate the air flow fields of the fuel cells (17, 18) when in a position normal to the first position. A vane (41) can comprise the divider of the air inlet/outlet manifold when in a vertical position, and totally block off the manifold when in a horizontal position. A vane (59) can align with the divider (24) of an air inlet/out manifold when in a vertical position, and block the passage between the manifold and conduits (44, 46) when in a horizontal position. Similar vanes may be used for single-valve selection of flow or containment of fuel reactant gas.

Abstract: A burner assembly includes a catalyzed burner for combusting an anode exhaust stream from a polymer electrolyte membrane (PEM) fuel cell power plant. The catalysts coated onto the burner can be platinum, rhodium, or mixtures thereof. The burner includes open cells which are formed by a lattice, which cells communicate with each other throughout the entire catalyzed burner. Heat produced by combustion of hydrogen in the anode exhaust stream is used to produce steam for use in a steam reformer in the PEM fuel cell assembly. The catalyzed burner has a high surface area wherein about 70–90% of the volume of the burner is preferably open cells, and the burner has a low pressure drop of about two to three inches water from the anode exhaust stream inlet to the anode exhaust stream outlet. The burner assembly operates at essentially ambient pressure and at a temperature of up to about 1,700° F. (927° C.). The burner assembly can combust anode exhaust during normal operation of the fuel cell assembly.

Abstract: A fuel cell system includes a fuel cell (1) having a water passage and passage for gas required for power generation, a first protection device (5, 10) which prevents freezing of water in the fuel cell by maintaining the temperature of the fuel cell (1), and a second protection device (11, 12) which prevents freezing of water in the fuel cell by discharging the water in the fuel cell (1). A controller (50) selects one of the first protection device (5, 10) and the second protection device (11, 12) as the protection device to be used when the fuel cell (1) has stopped, and the fuel cell (1) is protected from freezing of water by operating the selected protection device.

Abstract: Method and apparatus for changing the state of operation of a fuel cell, such as starting the fuel cell up or shutting the fuel cell down, are disclosed. An idle load is applied to the fuel cell when the cell temperature is between about normal operating temperature and a transition temperature, and fuel and oxidizer are supplied to the fuel cell commensurate with the power delivered to the idle load. Below the transition temperature, purging/passivation procedures known in the art can be followed, and an open or dummy load applied to the fuel cell. At normal operating temperature or above a service load is applied to the fuel cell.