Abstract: Fuel cell stack assemblies (15, 16) connected in parallel through related power control portions (39, 40; 60, 61) of a system power converter (41) supply power to a common grid (22) or non-grid load (58) on an equal or near-equal current basis. Power command to one portion is one-half the total power (P*) minus a function (46) of the difference (45) in current from the stack assemblies. The other portion power command (P1*) for a utility grid (22) is the difference between the total power and the power command (P2*) to the first stack assembly. For a non-grid load, one portion (61) controls the load voltage, the other portion command (P2*) causes substantially equal currents. Altering (33b) actual current signals results in the cell stack assemblies providing different currents. A failed stack assembly is disconnected from the load and reactant; the non-failed assembly having an appropriate power command.

Abstract: A control method and arrangement (48, 50, 150, I, T, P, FFL) are provided in a fuel cell power plant (10) for regulating (48, FC) fuel flow to a steam-based fuel processing system (FPS) (14) associated with a low-temperature fuel cell stack assembly (12). A portion of the fuel provided by the FPS (14) is used to provide steam for the FPS. The fuel flow to the FPS is regulated as a function of the power demand (I) on the fuel cell (12) and at least the enthalpy of the steam (P, T), such that the steam enthalpy is regulated to meet increases and decreases in power demand without exceeding steam pressure limits. In addition to reliance on-steam pressure (P) as a fundamental measure of steam enthalpy, the control may additionally use reaction temperature (T) at, or in, a reformer, such as a catalytic steam reformer (132), to regulate fuel flow and thus, steam enthalpy.

Abstract: A control method and arrangement (48, 50, 150, I, T, P, FFL) are provided in a fuel cell power plant (10) for regulating (48, FC) fuel flow to a steam-based fuel processing system (FPS) (14) associated with a low-temperature fuel cell stack assembly (12). A portion of the fuel provided by the FPS (14) is used to provide steam for the FPS. The fuel flow to the FPS is regulated as a function of the power demand (I) on the fuel cell (12) and at least the enthalpy of the steam (P, T), such that the steam enthalpy is regulated to meet increases and decreases in power demand without exceeding steam pressure limits. In addition to reliance on-steam pressure (P) as a fundamental measure of steam enthalpy, the control may additionally use reaction temperature (T) at, or in, a reformer, such as a catalytic steam reformer (132), to regulate fuel flow and thus, steam enthalpy.

Abstract: A fuel cell power plant 10 having a fuel cell assembly 20 that may be operable at a high hydrogen utilization. The fuel cell assembly is provided with an inlet fuel stream 207, an inlet oxidant stream 210, and an inlet coolant stream 208, and further has an exhaust oxidant 75 stream and an exhaust coolant stream 205. A housing chamber 110 accepts the exhaust coolant stream and exposes it to a first gaseous stream. A mass and heat recovery device 95 accepts the first gaseous stream after the first gaseous stream is exposed to the exhaust coolant stream, and it promotes a transfer of thermal energy and moisture from the first gaseous stream to a second gaseous stream. The first gaseous stream includes the exhaust oxidant stream.

Abstract: A fuel cell power plant having a plurality of functionally integrated components including a fuel cell assembly provided with a fuel stream, an oxidant stream and a coolant stream. The fuel cell power plant functionally integrates a mass and heat recovery device for promoting a transfer of thermal energy and moisture between a first gaseous stream and a second gaseous stream, and a burner for processing the fuel exhausted from the fuel cell assembly during operation thereof. A housing chamber is utilized which accepts the oxidant stream exhausted from the fuel cell assembly after the exhausted oxidant stream has merged with a burner gaseous stream exhausted from the burner. The resultant merged airflow is subsequently directed to the housing chamber and to the mass and heat recovery device as the first gaseous stream.

Abstract: A fuel cell power plant in which the fuel cell stack is enclosed within a containment vessel and in which reformer burner exhaust is used to pressurize and purge the containment vessel is disclosed. The fuel cell power plant provides dynamic pressure balancing between the purge gas and fuel cell reactants to prevent leakage of the reactants from the fuel cell yet avoid an excessive pressure differential between the fuel cell and the containment vessel.

Abstract: Pressure differential 6 between cathode 2 and anode 3 is controlled by valve 24, 26 of valve complex 20. The complex 20 is located within anode recirculation loop 8, 9, 3, 20 whereby controllability is not lost with no flow through the anode. Control is thereby retained during nitrogen purging of the cathode.An orifice 22 in the valve complex 20 precludes accidental full closure of the complex, and is selected to avoid immediate damage to the fuel cell on such closure.

Abstract: Fuel cell coolant loop (2) is to be controlled to maintain set point 38 temperature of the return coolant. Waste heat heat exchanger 10 is controlled to maintain set point 22 temperature in the waste heat fluid. Heat rejection heat exchanger removes additional heat as required to maintain the set point (38) temperature.If both set point temperatures cannot be maintained, a control override allows the waste heat fluid temperature to drop.

Abstract: A fuel cell power plant and a method of operating a fuel cell power plant which allows indirect control of the reformer burner flame temperature are disclosed. A hydrocarbon fuel is reformed to provide a hydrogen rich fuel stream and the hydrogen rich fuel stream is oxidized in a fuel cell. A stream of anode exhaust and an oxidant stream comprising cathode exhaust and air are combusted in the reformer burner. The mass flow rate and composition of the oxidant stream are controlled to maintain the oxygen content of the burner exhaust within a predetermined range and thus maintain the flame temperature of the combustion mixture within a preferred range.

Abstract: A system and method for regulating the total oxygen content entering the cathode side of a fuel cell stack at less than full power depends on measurement of: oxygen partial pressure in the cathode exhaust stream; total flow entering the cathode; and current produced by the stack. During partial power operation of the stack, it is desirable to limit the cathode potential, or voltage, by recycling cathode exhaust and mixing it with incoming fresh air fed into the cathodes. This system ensures that the total oxygen flow to the cathodes remains constant at any given current by reducing the amount of fresh air flowing to the cathodes as the recycled cathode exhaust flow is increased.