Thermochemical cycle based on solid intermediates for hydrogen storage and on-demand production

Abstract

Thermochemical water splitting processes based on Sulfur-Iodine cycle can be conveniently improved using solid intermediates, in order to increase the global yield and avoid the use of concentrated acid at high temperatures. In this context, an innovative process has been conceived, where a metal oxide, namely NiO, is reduced into oxygen and the correspondent metal, which can be suitably stored and reacted with steam into hydrogen when and where necessary. Data previously obtained and published, together with the integration of experimental results have been used to evaluate the technical feasibility and the heat duties of each step of the proposed cycle. The starting point was a Nickel compounds based process already extensively characterized, which has been modified using low toxic Iron (III) species as intermediates for oxygen formation. Based on the theoretical and experimental analysis carried out, the resulting cycle thermal efficiency is quite promising, about 19%, also taking into account the hydrogen generation step.