A novel three-step GeO2/GeO thermochemical water splitting cycle for solar hydrogen production

Abstract

This investigation reports the thermodynamic exploration of a novel three-step GeO2/GeO water splitting (WS) cycle. The thermodynamic computations were performed by using the data obtained from HSC Chemistry thermodynamic software. Numerous process parameters allied with the GeO2/GeO WS cycle were estimated by drifting the thermal reduction (TH) and water splitting temperature (TL). The entire analysis was divided into two section: a) equilibrium analysis and b) efficiency analysis. The equilibrium analysis was useful to determine the TH and TL required for the initiation of the thermal reduction (TR) of GeO2 and re-oxidation of GeO via WS reaction. Furthermore, the influence of PO2 on the TH required for the comprehensive dissociation of GeO2 into GeO and O2 was also studied. The efficiency analysis was conducted by drifting the TH and TL in the range of 2080 to 1280 K and 500e1000 K, respectively. Obtained results indicate that the minimum Q_ solar cycle ¼ 624:3 kW and maximum hsolar to fuel ¼ 45:7% in case of the GeO2/GeO WS cycle can be attained when the TR of GeO2 was carried out at 1280 K and the WS reaction was performed at 1000 K. This hsolar to fuel ¼ 45:7% was observed to be higher than the SnO2/SnO WS cycle (39.3%) and lower than the ZnO/Zn WS cycle (49.3%). The Q_ solar cycle can be further decreased to 463.9 kW and the hsolar to fuel can be upsurged up to 61.5% by applying 50% heat recuperation.