Fuel cell energy conversion devices and use of hydrogen as an energy carrier have benefited from major technological advancements in recent years. Fuel cells can provide continuous power with extremely low (or zero) criteria pollutant and greenhouse gas emissions from a variety of renewable and fossil fuels that well compliments the relative intermittency of many forms of renewable power. The sustainability of energy conversion is aided by the highly efficient use of limited fossil fuel reserves, of renewable fuels such as biogas, landfill and digester gas, and of waste fuel streams that can be accomplished using a fuel cell system. Hydrogen can play a significant role in that it is one of only a few options that can enable transportable power with zero pollutant and greenhouse gas emissions at the point of use. In addition, hydrogen can be efficiently produced with very low emissions from a variety of renewable and more sustainable primary energy sources such as wind, solar, and nuclear power (by water electrolysis or splitting), from biogases and industrial waste streams, as well as from fossil fuels such as natural gas and coal. While there are many significant technical hurdles to overcome before fuel cell technology can become widely available and while significant investments will be required to enable the widespread use of hydrogen as an energy carrier, recent developments are proving the environmental and energy efficiency performance, diversity, continuous power capabilities, and potential future economic competitiveness of fuel cell and hydrogen technologies that could enable their future contributions to a more sustainable and renewable energy future. The current paper introduces some potential future roles of fuel cells and hydrogen and highlights some work being conducted at the National Fuel Cell Research Center. © 2009 Elsevier B.V. All rights reserved.