Thermodynamic efficiency analysis of zinc oxide based solar driven thermochemical H2O splitting cycle: Effect of partial pressure of O2, thermal reduction and H2O splitting temperatures

In this paper, the thermodynamic efficiency analysis of ZnO-based solar-driven thermochemical H2O splitting cycle is performed and compared with the SnO2-based H2O splitting cycle. The HSC Chemistry 7.1 software is used for this analysis and effects of thermal reduction (T-H) and water splitting temperature (T-L) on various thermodynamic parameters associated with the ZnO-based H2O splitting cycle are explored. The thermodynamic equilibrium compositions allied with the ZnO reduction and re-oxidation of Zn via H2O splitting reaction are identified by varying the T-H, T-L, and P-O2 in the inert gas. The efficiency analysis indicates that the highest cycle and solar-to-fuel energy conversion efficiency equal to 41.1 and 49.5% can be achieved at T-H = 1340 K and T-L = 650 K. Both efficiencies can be increased further by more than 10% via employing heat recuperation (50%). Based on the cycle and solar-to-fuel energy conversion efficiency values, the ZnO-based H2O splitting cycle seems to be more attractive than SnO2-based H2O splitting cycle. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.