A fuel cell power plant having a fuel cell assembly includes an anode provided with a fuel stream, a cathode provided with an oxidant stream, an ion exchange membrane oriented between said anode and said cathode, and a coolant loop circulating a coolant stream in fluid communication with the fuel cell assembly. An oxidant source is utilized for supplying the fuel cell assembly with the oxidant stream at a predetermined pressure, while a coolant regulator oriented along the coolant loop lowers the coolant stream to a subambient pressure prior to the coolant stream coming into fluid communication with the fuel cell assembly.