Fuel cell system, estimation device of amount of anode gas to be generated and estimation method of amount of anode gas to be generated

Abstract

There is disclosed a fuel cell system or the like capable of sufficiently reducing an exhaust hydrogen concentration even in a case where a fuel cell is operated in a state of a low power generation efficiency. A bypass valve B 1 is arranged between an oxidation gas supply path 11 and a cathode-off gas channel 12 . In a state in which supply of an oxidation gas to a cathode falls short, pumping hydrogen is included in a cathode-off gas. Therefore, a valve open degree of the bypass valve B 1 is regulated, and a flow rate of bypass air is regulated to control the exhaust hydrogen concentration.

1 . An estimation device for determining an estimated amount of an anode gas generated in a cathode of a fuel cell, the estimation device comprising:
 operation control means for operating the fuel cell at a low-efficiency operation point having a power loss larger than that of a usual operation point in a case where predetermined conditions are satisfied; the operation control means determining an air stoichiometric ratio of the fuel cell based on the low-efficiency operation point so as to operate the fuel cell at the low-efficiency operation point; and   estimated amount determination means for determining an estimated amount of the anode gas generated in the cathode, based on the air stoichiometric ratio determined by the operation control means or an output voltage of the fuel cell which has a correlation with the air stoichiometric ratio, by use of a preset relation of the air stoichiometric ratio of the fuel cell to the amount of the anode gas generated in the cathode, in a case where the fuel cell is operated at the low-efficiency operation point.   
     
     
         2 . The estimation device of the amount of the anode gas generated according to  claim 1 ,
 wherein the relation is represented by map data which indicates the amount of the anode gas generated with the air stoichiometric ration of the fuel cell as a parameter, and   wherein the estimated amount determination means determines the estimated amount of the anode gas generated in the cathode, based on the air stoichiometric ratio determined by the operation control means, by use of the map data.   
     
     
         3 . The estimation device of the amount of the anode gas generated according to  claim 1 , wherein the relation is set in consideration of at least one of a remaining amount of a non-reacted cathode gas which remains on a cathode side of the fuel cell and fluctuations of pressure losses of cells constituting the fuel cell, together with a power generation characteristic of the fuel cell and an amount of a cathode gas supplied to the fuel cell. 
     
     
         4 . The estimation device of the amount of the anode gas generated according to  claim 3 , wherein the relation is set in consideration of both the remaining amount of the non-reacted cathode gas and the fluctuations of the pressure losses of the cells. 
     
     
         5 . The estimation device of the amount of the anode gas generated according to  claim 1 , further comprising:
 a voltage monitor which detects the output voltage of the fuel cell,   wherein the estimated amount determination means determines the estimated amount of the anode gas generated in the cathode based on the output voltage detected by the voltage monitor.   
     
     
         6 . The estimation device of the amount of the anode gas generated according to  claim 5 ,
 wherein the voltage monitor detects a cell voltage of each of the cells of the fuel cell,   wherein the relation is represented by a reference function which indicates a relation between the cell voltage of a reference cell and the amount of the anode gas generated, and   wherein the estimated amount determination means determines the estimated amount of the anode gas generated in the cathode, based on the cell voltage of each cell detected by the voltage monitor, by use of the reference function.   
     
     
         7 . The estimation device of the amount of the anode gas generated according to  claim 1 , wherein the operation control means operates the fuel cell at the low-efficiency operation point in a case where the fuel cell needs to be warmed up or in a case where a catalyst activity of the fuel cell needs to be restored. 
     
     
         8 . A method of determining an estimated amount of an anode gas generated in a cathode of a fuel cell, the method comprising:
 an operation control step of operating the fuel cell at a low-efficiency operation point having a power loss larger than that of a usual operation point in a case where a predetermined condition is satisfied; wherein an air stoichiometric ratio of the fuel cell is determined based on the low-efficiency operation point so as to operate the fuel cell at the low-efficiency operation point; and   an estimated determination step of determining an estimated amount of the anode gas generated in the cathode, based on the air stoichiometric ratio determined by the operation control step or an output voltage of the fuel cell which has a correlation with the air stoichiometric ratio, by use of a preset relation of the air stoichiometric ratio of the fuel cell to the amount of the anode gas generated in the cathode, in a case where the fuel cell is operated at the low-efficiency operation point.   
     
     
         9 . The method of determining the amount of the anode gas generated according to  claim 8 ,
 wherein the relation is represented by map data which indicates the amount of the anode gas generated with the air stoichiometric ratio of the fuel cell as a parameter, and   wherein the estimated amount determination step determines the estimated amount of the anode gas generated in the cathode, based on the air stoichiometric ratio determined by the operation control step, by use of the map data.   
     
     
         10 . The method of determining the amount of the anode gas generated according to  claim 8 , wherein the relation is set in consideration of at least one of a remaining amount of a non-reacted cathode gas which remains on a cathode side of the fuel cell and fluctuations of pressure losses of cells constituting the fuel cell, together with the power generation characteristic of the fuel cell and an amount of a cathode gas supplied to the fuel cell. 
     
     
         11 . The method of determining the amount of the anode gas generated according to  claim 8 , wherein the estimated amount determination step determines the estimated amount of the anode gas generated in the cathode based on the output voltage of the fuel cell detected by a voltage monitor.