Patent ID: 7078117

Claim:
A method for humidifying a reactant gas supply stream for a solid polymer fuel cell, said reactant gas supply stream being directed to a reactant gas inlet port of said fuel cell, said fuel cell having a reactant gas exhaust stream directed from a reactant gas exhaust port of said fuel cell, said method comprising: (a) employing a membrane exchange humidifier comprising a supply stream chamber, an exhaust stream chamber, and a water permeable membrane separating said chambers, said membrane comprising a microporous polymer and a hydrophilic additive, said membrane when dry being substantially permeable to at least one component of at least one of said reactant gas supply and exhaust streams, and wherein the hydrophilic additive is present in an amount sufficient to render the water permeable membrane wettable to water; (b) directing said reactant gas supply stream through said supply stream chamber upstream of said fuel cell reactant gas inlet port; and (c) directing said reactant gas exhaust stream from said reactant gas exhaust port through said exhaust stream chamber; whereby water is transferred from said reactant gas exhaust stream to said reactant gas supply stream across said membrane.