... increasing world population and demands for higher standards of living and better air quality, the future energy demand is expected to increase signi cantly. To meet this demand poses great challenges. ... direct methanol fuel cell (DMFC), (3) molten carbonate fuel cell (MCFC), (4) phosphoric acid fuel cell (PAFC), (5) proton exchange membrane fuel cell (PEMFC), and (6) the solid oxide fuel cell (SOFC). ... from Alternative Fuels Data Center, Properties of Fuel, DOE Report, August 2005, available at www.afdc.doe.gov /fuel_ comp.html, April 2007. TABLE 1.5LHV Energy Densities of Fuels Fuel Energy Density...