Patent ID: 8124290

Claim:
A method of operating a fuel cell power plant ( 9 ) comprising: a fuel cell stack ( 10 ) including a plurality of fuel cells having anodes ( 11 ) with inlets ( 15 ) and outlets ( 30 ), cathodes ( 12 ) with inlets ( 51 ) and outlets ( 55 ), and coolant channels ( 13 ); either (a) a coolant accumulator ( 60 ) and a coolant circulator ( 66 ) for circulating coolant through said accumulator and said coolant channels, or (b) a condenser ( 90 ) connected to said exits ( 55 ) of said cathodes ( 12 ), the condensate of said condenser in fluid communication ( 60 a , 85 ) with said coolant channels ( 13 ), said condenser having a cooling device ( 92 ); a controller ( 20 ); a source ( 18 , 24 ) of liquid hydrogen providing gaseous hydrogen in response to absorption of heat; a fluid connection ( 16 - 19 ) between gaseous hydrogen from said source and the inlets of said anodes; said method characterized by: controlling the operation of said fuel cell power plant during fuel boil-off operation, to produce heat and electric power at less than about 10% of normal maximum current density when satisfying a load, in response to hydrogen gas boiling off from said source of liquid hydrogen; and operating the controller, the cathode air pump and either (a) the coolant circulator or (b) the cooling device during fuel boil-off operation in response to electric power generated by said fuel cell stack.