Fuel cells for vehicle propulsion applications: a thermodynamic systems analysis

The liquid- and air-cooled phosphoric acid, the proton exchange membrane, and the monolithic solid oxide fuel cell systems are analyzed for use in vehicle propulsion applications. System efficiency and input energy distribution are examined as a function of electrochemical fuel utilization and other operating parameters. The liquid-cooled phosphoric acid and the monolithic solid oxide fuel cell systems have efficiencies approaching 40%; the air-cooled phosphoric acid and the proton exchange membrane fuel cells offer efficiencies near 30%. Thus the efficiencies of all of these fuel cell systems are much greater than the efficiencies of internal combustion engines. The analyses indicate further that these fuel cells should be operated at the highest practical electrochemical fuel utilization rates for best efficiency and dynamic response, as well as minimum component volume and cost