Process Description
The thermochemical two-step water splitting process uses two redox steps. The steps of solar hydrogen production by iron baised two-step cycle are:
(1) M(II)Fe2(III)O4 → M(II)O + 2Fe(II)O + ½O2 (Reduction)
(2) M(II)O + 2Fe(II)O + H2O → M(II)Fe2(III)O4 + H2 (Oxidation)
Where M can by any number of metals often Fe itself, Co, Ni, Mn, Zn or mixtures thereof. The endothermic reduction step (1) is carried out at high temperatures greater than 1400 oC, though the "Hercynite cycle" is capable of temperatures as low as 1200 oC. The oxidative water splitting step (2) occurs at a lower ~1000 oC temperature which produces the original ferrite material in addition to hydrogen gas. The temperature level is realized by using a solar power tower and a set of heliostats to collect the solar thermal energy.
Read more about this topic: Iron Oxide Cycle
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