Thermodynamic efficiency analysis of ZnO/Zn based solar thermochemical CH4 reforming and H2O splitting cycle

Abstract

The ZnO/Zn based CH4 reforming (MR) and H2O splitting (WS) process was thermody- namically scrutinized in this investigation. Two process arrangements i.e., ZnO/Zn based open (ZS) process and ZnO/Zn based semi-open (ZSH) process were considered to perform the thermodynamic analysis. The ZS process resulted into production of Zn and syngas, whereas the H2 and syngas was generated from the ZSH process. For both processes, the results obtained during the equilibrium analysis shows that the thermal reduction (TR) of ZnO was feasible at 1200 K in presence of CH4 as the reducing agent. In case of the ZS process, the rise in the CH4/ZnO ratio from 0.1 to 1 resulted into an upsurge in the total solar energy required to run the cycle ( _Q solar ZS) and solar-to-fuel energy conversion effi- ciency ( hsolar to fuel ZS) by 460.1 kW and 13.0%, respectively. For the ZSH process, the total solar energy required to run the cycle ( _Q solar ZSH ) was decreased from 598.3 to 595.9 kW and the solar-to-fuel energy conversion efficiency ( hsolar to fuel ZSH ) was increased from 76.6 to 76.7% with the upturn in the WS temperature (TL) from 500 to 675 K. At identical experi- mental conditions, the hsolar to fuel ZSH was observed to be higher than the hsolar to fuel ZS .