Cathode saturation arrangement for fuel cell power plant

Abstract

The heat from various portions of a fuel cell power plant ( 110 ) are redistributed in a manner allowing desired modification of/to the heat removal means ( 152, 156 ), e. g., radiator ( 152 ), included in the coolant loop for the fuel cell stack assembly (CSA) ( 12 ). A humidifier ( 70 ) added in the coolant loop ( 114 ) and the inlet oxidant (air) stream ( 134 ′) serves to relatively increase the humidification of the inlet air while removing heat from the coolant prior to entering the CSA ( 12 ). The combined effects are to relatively increase the temperature of the coolant exiting the CSA without similarly increasing the temperature of the coolant entering the CSA, and to relatively increase the temperature differential (“pinch”) between the coolant entering the heat removal means and the cooling air of the heat removal means ( 152, 156 ). This latter effect permits a relative reduction in the size/capacity of the heat removal means ( 152, 156 ).

1 . In a fuel cell power plant ( 110 ) including a fuel cell stack assembly ( 12 ); an inlet oxidant stream ( 134 , 134 ′) operatively connected to a fuel cell stack assembly oxidant region inlet ( 36 ); a coolant loop ( 114 ) operatively connected to a fuel cell stack assembly coolant region inlet ( 48 ) and outlet ( 50 ), the coolant loop ( 114 ) including a heat removal means ( 152 ,  156 ) configured as a sink to transfer heat from a fuel cell stack assembly coolant at a source temperature to a sink temperature lower than the source temperature, the difference between said source temperature and said sink temperature being a temperature differential, a method of relatively increasing said temperature differential comprising the steps of:
 cooling ( 74 ) the coolant in the coolant loop ( 114 ) by heat and mass transfer subsequent to passing the heat removal means ( 152 ,  156 ) and prior to return introduction of the coolant to the fuel cell stack assembly ( 12 ); and   relatively increasing the temperature and humidity ( 72 ) of the inlet oxidant stream ( 134 ′) prior to introduction of the inlet oxidant stream to the fuel cell stack assembly oxidant region inlet ( 36 ), thereby to distribute the heat of at least the fuel cell stack assembly ( 12 ) and the heat removal means ( 152 ,  156 ) so as to relatively increase the coolant exit temperature from the fuel cell stack assembly ( 12 ) and to the heat removal means ( 152 ,  156 ) so as to relatively increase said temperature differential between the source temperature and the sink temperature.   
     
     
         2 . The method of  claim 1  wherein the steps of cooling ( 74 ) the coolant in the coolant loop ( 114 ) by heat and mass transfer subsequent to passing the heat removal means ( 152 ,  156 ) and prior to return introduction of the coolant to the fuel cell stack assembly ( 12 ) and of relatively increasing the temperature and humidity ( 72 ) of the inlet oxidant stream ( 134 ,  134 ′) prior to introduction of the inlet oxidant stream to the fuel cell stack assembly oxidant region inlet ( 36 ) comprise flowing the coolant and the oxidant stream through a humidifier ( 70 ) connected in the coolant loop ( 114 ) between the heat removal means ( 152 ,  156 ) and the coolant region inlet ( 48 ) and in the inlet oxidant stream ( 134 ′) to perform both steps. 
     
     
         3 . In a fuel cell power plant ( 110 ) including a fuel cell stack assembly ( 12 ); an inlet oxidant stream ( 134 ,  134 ′) operatively connected to a fuel cell stack assembly oxidant region inlet ( 36 ); a coolant loop ( 114 ) operatively connected to a fuel cell stack assembly coolant region inlet ( 48 ) and outlet ( 50 ), the coolant loop ( 114 ) including a heat removal means ( 152 ,  156 ) configured as a sink to transfer heat from a fuel cell stack assembly coolant at a source temperature to a sink temperature lower than the source temperature, the difference between said source temperature and said sink temperature being a temperature differential, a method of relatively increasing said temperature differential comprising the steps of:
 cooling ( 74 ) the coolant in the coolant loop ( 114 ) subsequent to passing the heat removal means ( 152 ,  156 ) and prior to return introduction of the coolant to the fuel cell stack assembly ( 12 ); and   relatively increasing the temperature and humidity ( 72 ) of the inlet oxidant stream ( 134 ′) prior to introduction of the inlet oxidant stream to the fuel cell stack assembly oxidant region inlet ( 36 ), thereby to distribute the heat of at least the fuel cell stack assembly ( 12 ) and the heat removal means ( 152 ,  156 ) so as to relatively increase the coolant exit temperature from the fuel cell stack assembly ( 12 ) and to the heat removal means ( 152 ,  156 ) so as to relatively increase said temperature differential between the source temperature and the sink temperature; and   said steps of cooling ( 74 ) the coolant in the coolant loop ( 114 ) subsequent to passing the heat removal means ( 152 ,  156 ) and prior to return introduction of the coolant to the fuel cell stack assembly ( 12 ) and of relatively increasing the temperature and humidity ( 72 ) of the inlet oxidant stream ( 134 ,  134 ′) prior to introduction of the inlet oxidant stream to the fuel cell stack assembly oxidant region inlet ( 36 ) comprise flowing both the coolant and the oxidant stream through a humidifier ( 70 ) connected in the coolant loop ( 114 ) and in the inlet oxidant stream ( 134 ′) to perform both steps.