Hydrogen production by water splitting on manganese ferrite-sodium carbonate mixture: Feasibility tests in a packed bed solar reactor-receiver

The sodium manganese mixed ferrite thermochemical cycle Na(Mn1/3Fe2/3)O2/
(MnFe2O4 þ Na2CO3) for sustainable hydrogen production has been implemented in a solar
reactor-receiver, packed with indirectly heated MnFe2O4/Na2CO3 mixture pellets, with the
aim of verifying its feasibility and of determining the critical aspects of the process. The
reactor operates at nearly constant temperature in the range 750-800 °C; the shift between
the hydrogen-producing and regeneration steps is obtained by switching the reactive gas
from water to carbon dioxide. Hydrogen produced during 1-h operation of the reactor is in
the range of 130-460 mmol/g of mixture, depending on experimental conditions. Compared
to other existing prototypes, the implemented process obtains comparable production
efficiencies while operating at lower temperature both in the hydrogen production and
regeneration phases.