Total thermal efficiency of a new open-loop SI thermochemical cycle for the production of hydrogen, sulfuric acid and electric power was investigated. The new system without CO2 emission is composed of sulfuric acid industry process which provides the chemical reactant SO2 and heat, electric energy demands of the system and SI open-loop cycle separated into the Bunsen reaction system, the HIx system and the H2SO4 concentration system. The selection of SI cycle to run in an open-loop fashion for China is tied-up with two important facts: (1) sulfur iron ore as SO2 source is inexpensive and abundantly available; (2) the product sulfuric acid, in addition to hydrogen, is valuable and marketable. The mass and heat balance of the process were calculated with the optimized conditions. Thermal efficiency for hydrogen production was 66.3% with ideal operating conditions of the EED cell and heat exchangers in the case of generating electric power without waste heat and was 70.9% in the case of high performance waste heat recovery. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.