H2 producing hybrid solar thermochemical ZnSO4/ZnO water splitting cycle: Thermodynamic efficiency analysis.

This investigation reports the thermodynamic efficiency analysis of a hybrid ZnSO 4 /ZnO water-splitting cycle. The data required for efficiency calculations are gathered from HSC Chemistry Software. The prime goal is to examine the effects of the thermal energy needed for heating inert sweep gas and separating the gaseous components in the cycle on the solar-to-fuel energy conversion efficiency. Complete dissociation of ZnSO 4 into ZnO, SO 2 , and O 2 is considered. Besides, a comprehensive re-oxidation of ZnO in the presence of SO 2 and H 2 O is assumed. A thermodynamic process model, which includes reduction and oxidation reactors, two separators, multiple gas-to-gas heat exchangers, two heaters, and one ideal H 2 /O 2 fuel cell, is developed and used to analyze the efficiency. The energy required for the separation of inert/O 2 /SO 2 gas mixture is observed to be one of the significant contributors to the energy needed to drive the ZnSO 4 /ZnO WS cycle. The solar power required (989.9 kW) is recorded to be the lowest for the inert gas molar flow rate equal to 10 mol/s. Because of the low solar energy requirement, the maximum solar-to-fuel energy conversion efficiency (28.4 %) is attained at the thermal reduction temperature of 1445 K. • Thermodynamic efficiency analysis of the ZnSO 4 /ZnO water splitting cycles is conducted. • The molar flow rate of inert gas is responsible for the variation in most process parameters. • Solar energy required is significantly affected by the rise in the energy penalty allied with the separators. • The maximum solar-to-fuel energy conversion efficiency (28.4 %) is achieved at a molar flow rate of inert gas equal to 10 mol/s. [ABSTRACT FROM AUTHOR]