Consumption-based fuel cell monitoring and control

Abstract

Fuel cell systems and methods for controlling the operation of components of the fuel cell system, such as which may include a fuel source and a fuel cell stack. In some examples, a fuel source is adapted to provide supply fuel to a fuel cell stack at a supply pressure. In some systems, fuel not used by the fuel cell stack is discharged through at least one exit orifice at an exit pressure. In some examples, a control system is adapted to control operation of one or both of the fuel source and the fuel cell stack based on the flow of unused fuel. In some examples, a target pressure is determined based on the level of electrical current produced by a fuel cell stack, such that when fuel is supplied at the target pressure, the fuel cell stack consumes a given proportion of the supply fuel.

1 . A method of operating a fuel cell system, the method comprising:
 providing supply fuel at a supply pressure;   applying oxidant and the supply fuel to a fuel cell stack, which includes at least one fuel cell, and which is adapted to produce electrical current therefrom;   detecting the level of electrical current produced by the fuel cell stack;   determining a target proportion of the supply fuel applied to the fuel cell stack that is consumed by the fuel cell stack for a given level of electrical current produced by the fuel cell stack; and   varying the supply pressure to maintain a proportion of supply fuel applied to the fuel cell stack that is consumed by the fuel cell stack at about the target proportion of the supply fuel.   
     
     
         2 . The method of  claim 1 , the method further comprising detecting a change in the electrical current produced by the fuel cell stack, wherein the varying includes varying the supply pressure based at least in part on the detected change in the electrical current. 
     
     
         3 . The method of  claim 1 , in which providing supply fuel includes applying one or more feedstocks to a fuel processing apparatus in a manner producing the supply fuel at the supply pressure, and in which varying the supply pressure includes varying applying the one or more feedstocks to the fuel processing apparatus in a manner that varies the supply pressure to maintain the proportion of the supply fuel applied to the fuel cell stack that is consumed by the fuel cell stack at about the target proportion of supply fuel. 
     
     
         4 . The method of  claim 3 , the method further comprising determining a flow of supply fuel, and controlling production of the supply fuel based on the determined flow of supply fuel. 
     
     
         5 . The method of  claim 4 , in which producing the supply fuel includes determining an efficiency of the production of the supply fuel based on the determined flow of supply fuel, and controlling the production of the supply fuel includes controlling the production of the supply fuel in a manner improving the efficiency of the production of the supply fuel. 
     
     
         6 . The method of  claim 4 , in which producing the supply fuel includes producing the supply fuel using a chemical process, and further in which controlling the production of the supply fuel includes determining a stoichiometry of the chemical process based on the determined flow of supply fuel and controlling production of the supply fuel based on the determined stoichiometry. 
     
     
         7 . The method of  claim 4 , in which determining the flow of supply fuel includes determining the flow of supply fuel based at least in part on the level of electrical current produced by the fuel cell stack. 
     
     
         8 . The method of  claim 1 , the method further including discharging fuel unused by the fuel cell stack. 
     
     
         9 . The method of  claim 8 , the method further including calculating a flow of fuel unused by the fuel cell stack. 
     
     
         10 . The method of  claim 9 , in which determining the flow of supply fuel includes determining the flow of supply fuel based on the level of electrical current produced by the fuel cell stack and the flow of fuel unused by the fuel cell stack. 
     
     
         11 . The method of  claim 8 , wherein the target proportion of supply fuel is less than 100%. 
     
     
         12 . The method of  claim 8 , wherein the target proportion of supply fuel is between 70% and 83%. 
     
     
         13 . A method of operating a fuel cell system, the method comprising:
 providing supply fuel at a supply pressure;   applying oxidant and the supply fuel to a fuel cell stack, which includes at least one fuel cell, and which is adapted to produce electrical current therefrom;   detecting the level of electrical current produced by the fuel cell stack;   determining a target proportion of the supply fuel applied to the fuel cell stack that is consumed by the fuel cell stack;   determining a target pressure of the supply fuel at which the fuel cell stack consumes the target proportion of the supply fuel for a given level of electrical current produced by the fuel cell stack; and   maintaining the supply pressure at about the target pressure.   
     
     
         14 . The method of  claim 13 , the method further comprising detecting a change in the electrical current produced by the fuel cell stack, and changing the target pressure based at least in part on the detected change in the electrical current. 
     
     
         15 . The method of  claim 13 , in which providing supply fuel includes applying one or more feedstocks to a fuel processing apparatus in a manner producing the supply fuel at the supply pressure, and in which maintaining the supply pressure includes applying the one or more feedstocks to the fuel processing apparatus in a manner maintaining the supply pressure at about the target pressure. 
     
     
         16 . The method of  claim 13 , the method further including discharging fuel unused by the fuel cell stack. 
     
     
         17 . A method of operating a fuel cell system, the method comprising:
 providing supply fuel at a supply pressure;   applying oxidant and the supply fuel to a fuel cell stack, which includes at least one fuel cell, and which is adapted to produce electrical current therefrom;   detecting the level of electrical current produced by the fuel cell stack;   determining a target proportion of the supply fuel applied to the fuel cell stack that is consumed by the fuel cell stack for a given level of electrical current produced by the fuel cell stack;   determining a target pressure of the supply fuel at which the fuel cell stack consumes the target proportion of the supply fuel; and   maintaining the supply pressure at about the target pressure.   
     
     
         18 . The method of  claim 17 , the method further comprising detecting a change in the electrical current produced by the fuel cell stack, and changing the target proportion of the supply fuel based at least in part on the detected change in the electrical current. 
     
     
         19 . The method of  claim 17 , in which providing supply fuel includes applying one or more feedstocks to a fuel processing apparatus in a manner producing the supply fuel at the supply pressure, and in which maintaining the supply pressure includes applying the one or more feedstocks to the fuel processing apparatus in a manner maintaining the supply pressure at about the target pressure. 
     
     
         20 . The method of  claim 17 , the method further including discharging fuel unused by the fuel cell stack.