The invention relates to a fuel cell stack having a variety of individual cells stacked up to form a stack, having at least one humidifier section integrated into the stack and arranged at one end of the individual cells as an electrochemical section. The invention is characterized in that a heat exchanger section is arranged on the side of the at least one humidifier section facing away from the electrochemical section, wherein flow plates for distributing fluids in at least three sections of the stack have the same external geometry.

A fuel cell system is provided that includes a fuel cell with an assembly of multiple individual cells, each of which has an anode section, an electrolyte membrane, and a cathode section, an anode gas supply, which leads to an anode gas inlet and includes a fuel cell and a fuel metering device, a cathode gas supply, and a passive anode gas recirculation device, which connects an anode gas outlet to the recirculation gas inlet of a mixer arranged in the anode gas supply. The fuel cell system is started up after a standstill in that in a first phase, the fuel cell is activated while fuel is supplied from the fuel source, and the anode recirculation is suppressed without actively blocking the anode gas recirculation device, and in a second phase, anode gas is recirculated in addition to the supply of fuel from the fuel source.

A fuel cell system is provided that includes a fuel cell with an assembly of multiple individual cells, each of which has an anode section, an electrolyte membrane, and a cathode section, an anode gas supply, which leads to an anode gas inlet and includes a fuel cell and a fuel metering device, a cathode gas supply, and a passive anode gas recirculation device, which connects an anode gas outlet to the recirculation gas inlet of a mixer arranged in the anode gas supply. The fuel cell system is started up after a standstill in that in a first phase, the fuel cell is activated while fuel is supplied from the fuel source, and the anode recirculation is suppressed without actively blocking the anode gas recirculation device, and in a second phase, anode gas is recirculated in addition to the supply of fuel from the fuel source.

A pressurized air supply system supplies, to a pressurization object device, flowing air that includes at least one of compressed air, which is generated by compressing air supplied from an air supply source, or discharged air from a turbocharger compressor forming a turbocharger. The compressor is controlled such that a saturated steam temperature of the flowing air supplied from the air supply source to the pressurization object device is lower than a temperature in the pressurization object device, at startup.

A pressurized air supply system supplies, to a pressurization object device, flowing air that includes at least one of compressed air, which is generated by compressing air supplied from an air supply source, or discharged air from a turbocharger compressor forming a turbocharger. The compressor is controlled such that a saturated steam temperature of the flowing air supplied from the air supply source to the pressurization object device is lower than a temperature in the pressurization object device, at startup.

A fuel cell system includes a fuel cell unit having an air inlet, a fuel inlet and an electrical energy outlet and a fuel cell exhaust outlet and a turbo-compressor unit to convert air from an air supply to compressed inlet air for the fuel cell unit. The turbo-compressor unit comprising a turbine and a compressor connected to a common rotatable shaft. The system also includes means for obtaining conditioned air exhausted from an enclosed space and directing the conditioned exhaust air to the turbine of turbo-compressor unit such that the conditioned exhaust air is expanded by the turbine causing rotation of the shaft and corresponding rotation of the compressor, means for providing air from the air supply to the compressor to be compressed and output from the compressor unit and provided as compressed inlet air to the air inlet of the fuel cell unit.

A fuel cell system includes a fuel cell unit having an air inlet, a fuel inlet and an electrical energy outlet and a fuel cell exhaust outlet and a turbo-compressor unit to convert air from an air supply to compressed inlet air for the fuel cell unit. The turbo-compressor unit comprising a turbine and a compressor connected to a common rotatable shaft. The system also includes means for obtaining conditioned air exhausted from an enclosed space and directing the conditioned exhaust air to the turbine of turbo-compressor unit such that the conditioned exhaust air is expanded by the turbine causing rotation of the shaft and corresponding rotation of the compressor, means for providing air from the air supply to the compressor to be compressed and output from the compressor unit and provided as compressed inlet air to the air inlet of the fuel cell unit.

A method for operating a fuel cell assembly, the fuel cell assembly including a fuel cell stack having a solid oxide fuel cell, the solid oxide fuel cell having an anode, a cathode, and an electrolyte, the method including: determining a temperature setpoint for the fuel cell stack, for output products of the fuel cell stack, or both; and controlling a volume of oxidant provided to the anode in response to the determined temperature setpoint to control a temperature of the fuel cell stack, a temperature of the output products of the fuel cell stack, or both.

A method for operating a fuel cell assembly, the fuel cell assembly including a fuel cell stack having a solid oxide fuel cell, the solid oxide fuel cell having an anode, a cathode, and an electrolyte, the method including: determining a temperature setpoint for the fuel cell stack, for output products of the fuel cell stack, or both; and controlling a volume of oxidant provided to the anode in response to the determined temperature setpoint to control a temperature of the fuel cell stack, a temperature of the output products of the fuel cell stack, or both.

A method for operating a propulsion system for an aircraft, the propulsion system including a gas turbine engine and a fuel cell assembly, the fuel cell assembly comprising a fuel cell stack having a fuel cell defining an outlet positioned to remove output products from the fuel cell during operation, the method including: executing a startup sequence for the gas turbine engine, wherein executing the startup sequence comprises initiating the startup sequence for the gas turbine engine; executing a startup sequence for the fuel cell assembly concurrently with, or subsequent to, initiating the startup sequence for the gas turbine engine; and operating the fuel cell assembly to provide output products to a combustion section of the gas turbine engine.