Direct oxidation fuel cell systems with regulated fuel concentration and oxidant flow

Abstract

A direct oxidation fuel cell (DOFC) system, comprises at least one fuel cell assembly including a cathode and an anode with an electrolyte positioned therebetween; a source of liquid fuel in fluid communication with an inlet of the anode; an oxidant supply in fluid communication with an inlet of the cathode; a liquid/gas (L/G) separator in fluid communication with outlets of the anode and cathode for: (1) receiving unreacted fuel and liquid and gaseous products, and (2) supplying a solution of fuel and liquid product to the anode inlet; and a control system for measuring the amount of liquid product and controlling oxidant stoichiometry of the system operation in response to the measured amount of liquid product. Alternatively, the control system controls the concentration of the liquid fuel in the solution supplied to the anode inlet, based upon the system operating temperature or output power.

1 . A direct oxidation fuel cell (DOFC) system, comprising: 
 (a) at least one fuel cell assembly including a cathode and an anode with an electrolyte positioned therebetween;    (by a source of liquid fuel in fluid communication with an inlet of said anode;    (c) an oxidant supply in fluid communication with an inlet of said cathode;    (d) a liquid/gas (L/G) separator in fluid communication with outlets of said anode and cathode for: (1) receiving unreacted fuel, liquid product, and gases, and (2) supplying a solution of liquid fuel in liquid product to said inlet of said anode; and    (e) a control system for measuring the amount of said liquid product and controlling oxidant stoichiometry of said DOFC system during operation at an appropriate value in response to said measured amount of liquid product.    
   
   
       2 . The DOFC system as in  claim 1 , wherein: 
 said control system includes a sensor for measuring said amount of liquid product.    
   
   
       3 . The DOFC system as in  claim 2 , wherein: 
 said sensor measures the amount of said liquid product contained in said L/G separator.    
   
   
       4 . The DOFC system as in  claim 1 , wherein: 
 said control system is capable of periodically or continuously controlling said oxidant stoichiometry.    
   
   
       5 . The DOFC system as in  claim 1 , wherein: 
 said control system comprises an electronic control unit (ECU).    
   
   
       6 . The DOFC system as in  claim 5 , wherein: 
 said ECU, comprises an electronic computer programmed for: (1) comparing said measured amount of liquid product with a predetermined amount for determining whether said measured amount is greater than, smaller than, or the same as said predetermined amount; (2) determining a calculation factor based upon said comparison; (3) calculating said appropriate value of oxidant stoichiometry utilizing said calculation factor; and (4) regulating said oxidant supply to achieve said appropriate value of oxidant stoichiometry.    
   
   
       7 . A direct oxidation fuel cell (DOFC) system, comprising: 
 (a) at least one fuel cell assembly including a cathode and an anode with an electrolyte positioned therebetween;    (b) a source of liquid fuel in fluid communication with an inlet of said anode;    (c) an oxidant supply in fluid communication with an inlet of said cathode;    (d) a liquid/gas (L/G) separator for: (1) receiving unreacted fuel, liquid product, and gases from said cathode and anode, and (2) supplying a solution of liquid fuel in liquid product to said inlet of said anode; and    (e) a control system for controlling the concentration of said liquid fuel in said solution supplied to said inlet of said anode.    
   
   
       8 . The DOFC system as in  claim 7 , wherein: 
 said control system is capable of regulating supply of said liquid fuel to said inlet of said anode from said source of liquid fuel and from said L/G separator.    
   
   
       9 . The DOFC system as in  claim 8 , wherein: 
 said control system is capable of periodically or continuously controlling said oxidant stoichiometry and comprises an electronic control unit (ECU).    
   
   
       10 . The DOFC system as in  claim 9 , wherein: 
 said control system includes a sensor for measuring the operating temperature of said at least one fuel cell assembly, and said ECU comprises an electronic computer programmed for: (1) determining an appropriate concentration of said liquid fuel in said solution supplied to said inlet of said anode based upon the operating temperature of said at least one fuel cell assembly measured by said sensor; and (2) regulating said supply of said liquid fuel to said inlet of said anode from said source of liquid fuel and from said L/G separator to achieve said appropriate concentration.    
   
   
       11 . The DOFC system as in  claim 10 , wherein: 
 said computer is programmed with a predetermined relationship between said concentration of said liquid fuel supplied to said inlet of said anode and said operating temperature of said at least one fuel cell assembly.    
   
   
       12 . The DOFC system as in  claim 9 , wherein: 
 said ECU comprises an electronic computer programmed for: (1) determining an appropriate concentration of said liquid fuel in said solution supplied to said inlet of said anode based upon a desired output power of said at least one fuel cell assembly;    and (2) regulating said supply of said liquid fuel to said inlet of said anode from said source of liquid fuel and from said L/G separator to achieve said appropriate concentration.    
   
   
       13 . The DOFC system as in  claim 12 , wherein: 
 said computer is programmed with a predetermined relationship between said concentration of said liquid fuel in said solution supplied to said inlet of said anode and said output power of said at least one fuel cell assembly.    
   
   
       14 . A method of operating a direct oxidation fuel cell (DOFC) system comprising at least one fuel cell assembly including a cathode and an anode with an electrolyte positioned therebetween, a source of liquid fuel in fluid communication with an inlet of said anode, an oxidant supply in fluid communication with an inlet of said cathode; and a liquid/gas (L/G) separator in fluid communication with outlets of said anode and cathode for: (I) receiving unreacted fuel, liquid product, and gases, and (2) supplying a solution of liquid fuel in liquid product to said inlet of said anode, comprising: 
 measuring the amount of said liquid product and controlling oxidant stoichiometry of said DOFC system during operation at an appropriate value in response to said measured amount of liquid product.    
   
   
       15 . The method according to  claim 14 , comprising: 
 utilizing a sensor capable of measuring the amount of said liquid product contained in said L/G separator.    
   
   
       16 . The method according to  claim 15 , further comprising: 
 utilizing an electronic computer programmed for: (1) comparing said measured amount of liquid product with a predetermined amount for determining whether said measured amount is greater than, smaller than, or the same as said predetermined amount; (2) determining a calculation factor based upon said comparison; (3) calculating said appropriate oxidant stoichiometry utilizing said calculation factor; and (4) regulating said oxidant supply to achieve said appropriate oxidant stoichiometry.    
   
   
       17 . A method of operating a direct oxidation fuel cell (DOFC) system comprising at least one fuel cell assembly including a cathode and an anode with an electrolyte positioned therebetween, a source of liquid fuel in fluid communication with an inlet of said anode, an oxidant supply in fluid communication with an inlet of said cathode; and a liquid/gas (L/G) separator in fluid communication with outlets of said anode and cathode for: (1) receiving unreacted fuel, liquid product, and gases, and (2) supplying a solution of liquid fuel in liquid product to said inlet of said anode, comprising: 
 controlling the concentration of said liquid fuel in said solution supplied to said inlet of said anode.    
   
   
       18 . The method according to  claim 17 , comprising: 
 regulating supply of said liquid fuel to said inlet of said anode from said source of liquid fuel and from said L/G separator.    
   
   
       19 . The method according to  claim 18 , comprising: 
 utilizing a sensor for measuring the operating temperature of said at least one fuel cell assembly and an electronic computer programmed for: (1) determining an appropriate concentration of said liquid fuel in said solution supplied to said inlet of said anode based upon the operating temperature of said at least one fuel cell assembly measured by said sensor; and (2) regulating said supply of said liquid fuel to said inlet of said anode from said source of liquid fuel and from said L/G separator to achieve said appropriate concentration.    
   
   
       20 . The method according to  claim 19 , comprising: 
 utilizing a computer programmed with a predetermined relationship between said concentration of said liquid fuel in said solution supplied to said inlet of said anode and said operating temperature of said at least one fuel cell assembly.    
   
   
       21 . The method according to  claim 18 , comprising: 
 utilizing an electronic computer programmed for: (1) determining an appropriate concentration of said liquid fuel in said solution supplied to said inlet of said anode based upon a desired output power of said at least one fuel cell assembly; and (2) regulating said supply of said liquid fuel to said inlet of said anode from said source of liquid fuel and from said L/G separator to achieve said appropriate concentration.    
   
   
       22 . The method according to  claim 21 , comprising: 
 utilizing a computer programmed with a predetermined relationship between said concentration of said liquid fuel in said solution supplied to said inlet of said anode and said output power of said at least one fuel cell assembly.