Fuel cell system and operating method thereof

Abstract

The present invention includes a fuel cell ( 11 ), a fuel gas supplying device ( 16 ), an oxidizing gas supplying device ( 17 ) and a control apparatus ( 20 ) and further includes at least one of a temperature control device ( 19 ) which controls the temperature of the fuel cell ( 11 ) and a humidifying device ( 24 ) which humidifies at least one of the fuel gas and the oxidizing gas to be supplied to the fuel cell ( 11 ), wherein: the control apparatus ( 20 ) controls at least one of the temperature control device ( 19 ), the humidifying device ( 24 ), the fuel cell ( 11 ) and the fuel gas supplying device ( 16 ) to cause the temperature of the fuel cell ( 11 ) to be equal to at least one of the dew point of the fuel gas and the dew point of the oxidizing gas, before cutting off an electrical connection between the fuel cell ( 11 ) and a load; and then the control apparatus ( 20 ) cuts off the electrical connection between the fuel cell ( 11 ) and the load.

1 - 26 . (canceled) 
     
     
         27 . A method for operating a fuel cell system comprising a fuel cell which generates electric power using a fuel gas containing hydrogen and an oxidizing gas containing oxygen, a fuel gas supplying device which supplies the fuel gas to said fuel cell, an oxidizing gas supplying device which supplies the oxidizing gas to said fuel cell, and at least one of a temperature control device which controls a temperature of said fuel cell and a humidifying device which humidifies at least one of the fuel gas and the oxidizing gas to be supplied to said fuel cell,
 the method comprising the steps of:   driving at least one of said temperature control device, said humidifying device, said fuel cell and said fuel gas supplying device based on at least one of a dew point of the fuel gas and a dew point of the oxidizing gas or on information related to the dew point;   controlling the dew point of the fuel gas and the dew point of the oxidizing gas to be lower than the temperature of said fuel cell, and generating the electric power by said fuel cell; and   when cutting off an electrical connection between said fuel cell and the load after generating the electric power and in a case where at least one of the dew point of the fuel gas and the dew point of the oxidizing gas becomes equal to or higher than the temperature of said fuel cell, cutting off the electrical connection between said fuel cell and the load.   
     
     
         28 . The method according to  claim 27 , wherein the temperature control device is controlled to decrease the temperature of said fuel cell such that at least one of the dew point of the fuel gas and the dew point of the oxidizing gas becomes equal to or higher than the temperature of said fuel cell. 
     
     
         29 . The method according to  claim 27 , wherein a lower one of the dew point of the fuel gas and the dew point of the oxidizing gas is set to become equal to or higher than the temperature of said fuel cell. 
     
     
         30 . The method according to  claim 27 , wherein the humidifying device is controlled to increase at least one of the dew point of the fuel gas and the dew point of the oxidizing gas such that at least one of the dew point of the fuel gas and the dew point of the oxidizing gas becomes equal to or higher than the temperature of said fuel cell. 
     
     
         31 . The method according to  claim 30 , wherein a temperature of a humidifier in the humidifying device is controlled by at least one of a flow rate and a temperature of at least one of the fuel gas and the oxidizing gas to increase at least one of the dew point of the fuel gas and the dew point of the oxidizing gas. 
     
     
         32 . The method according to  claim 27 , wherein utilized as the information related to the dew point is an operating condition of said fuel gas supplying device. 
     
     
         33 . The method according to  claim 27 , wherein utilized as the information related to the dew point is an operating condition of at least one of said fuel cell and said humidifying device.