Patent ID: 7960067

Claim:
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, 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; said control system is capable of periodically or continuously controlling oxidant stoichiometry and comprises an electronic control unit (ECU); and 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; (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; and (3) controlling said oxidant stoichiometry according to the formula: ξ c = 0.42 ⁢ ( γ + 2 ) 3 ⁢ ⁢ η fuel ⁢ p p sat wherein ξ c is the oxidant stoichiometry, γ is the ratio of water to fuel in the fuel supply, p sat is the water vapor saturation pressure corresponding to the cell temperature, p is the cathode operating pressure, and η fuel is the fuel efficiency.