Solar hydrogen production via ZnO/Zn based thermochemical water splitting cycle: Effect of partial reduction of ZnO

Abstract

This investigation reports the examination of the influence of partial reduction of ZnO on the thermodynamic parameters allied with the ZnO/Zn WS cycle. The efficiency analysis was conducted by developing and following the ZnO/Zn process flow configuration. By estimating the equilibrium compositions, the percentage of ZnO reduction (ZnO-R) as a function of the thermal reduction (TR) temperature (TH) was determined. After identifying the ZnO-R percentages, the influence of TH and ZnO-R on the thermodynamic process parameters was explored. Overall results of the efficiency analysis indicate that the operation of the partially reduced ZnO/Zn WS cycle, in the temperature range of 1040 K–1240 K, was more useful rather than operating at 1340 K. ZnO-R equal to 57.2% (TH = 1240 K) was favorable to operate the ZnO/Zn WS cycle as a further rise in the ZnO-R did not yield any significant improvement in the solar-to-fuel energy conversion efficiency. At ZnO-R equal to 57.2% (TH = 1240 K), by applying 50% HR, a value of 62.6% as the efficiency of solar to fuel can be achieved.