Solar hydrogen production via erbium oxide based thermochemical water splitting cycle

The erbium oxide based water splitting (Eb-WS) cycle was thermodynamically studied by using the HSC Chemistry software and databases. The first step of the Eb-WS cycle involves thermal reduction of Er2O3, whereas the second step corresponds to the production of H-2 via water splitting reaction. Equilibrium compositions associated with the thermal reduction and water splitting steps were determined by performing HSC simulations. Influence of partial pressure of oxygen (P-O2) in the inert purge gas on thermal reduction temperature (T-H) and equilibrium compositions associated with the solar thermal dissociation of Er2O3 was identified. Furthermore, energy and exergy analysis of the Eb-WS cycle was carried out to estimate the cycle (eta(cycle)) and solar-to-fuel conversion efficiency (eta(solar-to-fuel)). Simulation results indicate that the eta(cycle) and eta(solar-to-fuel) of Eb-WS cycle increase with the decrease in T-H. Also, the eta(cycle) and eta(solar-to-fuel) can be increased further via the recuperation of the heat released by the water splitting reactor and the quench unit. The eta(solar-to -fuel) of Eb-WS cycle was observed to be equivalent to that of ceria cycle. Published by AIP Publishing.