An overview and critical assessment of thermochemical hydrogen production methods

In the present study, the most common thermochemical cycles in the literature for hydrogen production are reviewed and discussed comparatively. These thermochemical cycles are first classified in accordance with the number of cycle steps. Then, the main thermochemical cycles that fall under the corresponding categories are further described and evaluated. The thermochemical cycles that can be potentially energized primarily via thermal energy from nuclear plants are highlighted. The main seven methods are comparatively evaluated through efficiencies, production cost, global warming potential, and acidification potential. Although there are previous studies showing interest in a similar field, this peer review intends to provide useful content for the researchers working in the field. The results of this study show a promising direction for using four of these cycles, namely Cu-Cl, V-Cl, Mg-Cl and S-I cycles, due to their high performance values in terms of energy effi-ciency as 52.6%, 69%, 63.63% and 46.9%, and in terms of exergy efficiency as 78.21%, 77.28%, 71%, 62.39%, respectively. Furthermore, these thermochemical cycles appear to be suitable for clean hydrogen production with a cost as low as 1.71 $/kg H2.