Thermodynamic analysis of solar driven SnO2/SnO based thermochemical water splitting cycle

Abstract

There are many studies related on the SnO2/SnO based solar thermochemical water splitting cycle, however there are still no studies addressing on the detailed thermodynamic analysis of this process using HSC Chemistry software and its thermodynamic database. In this cycle, the first step belongs to the endothermic solar thermal reduction of SnO2 producing gaseous SnO and O2. The second step corresponds to the exothermic production of H2 via water splitting reaction using SnO produced in the first cycle, thereby regenerating SnO2 which can be recycled back to step 1. Thermodynamic equilibrium compositions associated with step 1 and 2 are identified as a function of reaction temperatures and partial pressures of O2 in the inert carrier gas. Furthermore, the thermodynamic efficiency analysis is performed by following the second law of thermodynamics to determine the cycle and solar-to-fuel energy conversion efficiencies associated with the SnO2/SnO based thermochemical water splitting cycle. Effects of thermal reduction and water splitting temperatures on various thermodynamic parameters are also investigated in detail. Obtained results indicate that the higher values of cycle efficiency (41.17%) and solar-to-fuel energy conversion efficiency (49.61%) are achievable by operating this cycle at a thermal reduction temperature of 1780 K and water splitting temperature equal to 800 K with 50% heat recuperation. This work gives a detailed thermodynamic and efficiency analysis of SnO2/SnO based two-step solar thermochemical water splitting cycle for hydrogen production.