Patent ID: 7112378

Claim:
A method of operating a fuel cell system, comprising: rotating an enthalpy wheel; flowing cathode exhaust from a fuel cell stack through the enthalpy wheel; flowing air through the enthalpy wheel to increase the humidity of the air; flowing the humidified air from the enthalpy wheel to a cathode electrode chamber of the fuel cell stack; flowing hydrogen through an anode electrode chamber of the fuel cell stack to produce an amount of electrical current; supplying the electrical current to a load; increasing a rotational speed of the enthalpy wheel to increase a dew point temperature of the humidified air fed to the fuel cell from the enthalpy wheel decreasing the rotational speed of the enthalpy wheel to decrease the dew point temperature of the humidified air fed to the fuel cell from the enthalpy wheel; flowing a coolant through the fuel cell stack; varying a stack inlet temperature of the coolant to maintain the stack inlet temperature of the coolant within a predetennined threshold; and varying the flow of the coolant through the stack to regulate a temperature differential between the stack inlet temperature of the coolant and a stack outlet temperature of the coolant.