Abstract: A fuel cell system is provided that is capable of operating at high temperatures and near-ambient pressure with partial humidification of air supplied to the fuel cell stack. The fuel cells of the stack incorporate gas diffusion barrier layers at the cathode side thereof. The system includes a cooling loop for circulating a liquid coolant through the stack. In some embodiments, an incoming air stream is partially humidified with water vapor transferred from a cathode exhaust stream in a gas-exchange humidifier or enthalpy wheel. In other embodiments, a cathode recycle is employed to partially humidify the incoming air. The humidity of the air and cathode exhaust streams is maintained below a stack saturation point. Methods of operating the fuel cell system are also provided.

Abstract: A system and method for starting up a fuel cell system are disclosed. Briefly described, an embodiment for starting an electrochemical reaction between a fuel and an oxidant during a start-up process includes a fuel cell stack operable to output a nominal voltage during a normal operating condition and operable to output a reduced start-up voltage during the start-up process, and includes at least one balance of plant (BOP) device that supports operation of the fuel cell stack, operable at a nominal output when sourced by the fuel cell stack at the nominal voltage, and operable at a reduced output when sourced by the fuel cell stack at the reduced start-up voltage.

Abstract: Improvements in startup time for an electrochemical fuel cell system from freezing and sub-freezing temperatures may be observed by minimizing the coolant volume in the coolant subsystem. In particular, this may be accomplished by having a two pump—dual loop cooling subsystem. During startup, one pump directs coolant through a startup coolant loop and after either the fuel cell stack or the coolant temperature reaches a predetermined threshold value, coolant from a main or standard coolant loop is then directed to the fuel cell stack. In an embodiment, coolant from the standard loop mixes with coolant in the startup loop after the predetermined threshold temperature is reached.

Abstract: A system and method for starting up a fuel cell system are disclosed. Briefly described, an embodiment for starting an electrochemical reaction between a fuel and an oxidant during a start-up process includes a fuel cell stack operable to output a nominal voltage during a normal operating condition and operable to output a reduced start-up voltage during the start-up process, and includes at least one balance of plant (BOP) device that supports operation of the fuel cell stack, operable at a nominal output when sourced by the fuel cell stack at the nominal voltage, and operable at a reduced output when sourced by the fuel cell stack at the reduced start-up voltage.

Abstract: A fuel cell system is provided that is capable of operating at high temperatures and near-ambient pressure with partial humidification of air supplied to the fuel cell stack. The fuel cells of the stack incorporate gas diffusion barrier layers at the cathode side thereof. The system includes a cooling loop for circulating a liquid coolant through the stack. In some embodiments, an incoming air stream is partially humidified with water vapor transferred from a cathode exhaust stream in a gas-exchange humidifier or enthalpy wheel. In other embodiments, a cathode recycle is employed to partially humidify the incoming air. The humidity of the air and cathode exhaust streams is maintained below a stack saturation point. Methods of operating the fuel cell system are also provided.

Abstract: A fuel cell system is provided that is capable of operating at high temperatures and near-ambient pressure with partial humidification of air supplied to the fuel cell stack. The fuel cells of the stack incorporate gas diffusion barrier layers at the cathode side thereof. The system includes a cooling loop for circulating a liquid coolant through the stack. In some embodiments, an incoming air stream is partially humidified with water vapor transferred from a cathode exhaust stream in a gas-exchange humidifier or enthalpy wheel. In other embodiments, a cathode recycle is employed to partially humidify the incoming air. The humidity of the air and cathode exhaust streams is maintained below a stack saturation point. Methods of operating the fuel cell system are also provided.