Comparative efficiency assessments for a range of hydrogen production processes

Efficiencies, based on energy and exergy, are comparatively assessed for a wide range of hydrogen production processes, including processes which are hydrocarbon-based (steam-methane reforming and coal gasification), non-hydrocarbon-based (water electrolysis and thermochemical water decomposition), and integrated (steam-methane reforming linked to the non-hydrocarbon-based processes). A process simulation and analysis computer code is used throughout. Overall efficiencies, based on primary resource inputs, are determined to range widely, from 21% to 86% for energy efficiencies, and from 19% to 78% for exergy efficiencies. Reductions in efficiencies from 100% are found to be attributable only to emissions for energy analysis, and mainly to internal consumptions for exergy analysis. Exergy losses associated with emissions account for a small portion of the total exergy losses. (C) 1998 International Association for Hydrogen Energy.