H2 generation via solar assisted CaO/Ca thermochemical H2O splitting cycle

This investigation reports the thermodynamic evaluation of a solar assisted CaO-based H2O splitting (Ca-WS) cycle. An HSC Chemistry 9.9 software was utilized for performing the thermodynamic equilibrium as well as efficiency analysis. Results associated with the equilibrium analysis indicate that the thermal reduction of the CaO (TR-Ca) was improved from 0 to 100% with an upsurge in the thermal reduction temperature (T-H) from 1900 K to 2230 K. The water splitting (WS) reaction was feasible at all temperatures above 300 K. However, to keep the Ca in the solid phase it was carried out at T-H = 1050 K. Due to the rise in the individual enthalpies of the Ca and O-2, the solar energy required to run the reactor (Q(solar-reactor-Ca-WS)) and heater (Q(solar-reactor-Ca-WS)) was increased by 775.5 kW and 69.5 kW as the T-H rose from 1900 K to 2230 K. The solar energy required to run the Ca-WS cycle (Q(solar-cycle-Ca-WS)) was also enhanced by 1568.2 kW due to the similar increment in the T-H. The solar-to-fuel energy conversion efficiency associated with the Ca-WS cycle (eta(solar-to-fuel-Ca-WS)) was first increased up to 19.5% and then decreased to 17.1% as a function of the rise in T-H from 1900 K to 2230 K. Overall, the Ca-WS cycle can achieve the maximum possible eta(solar-to-fuel-Ca-WS) (19.5%) at T-H and T-L equal to 2040 K and 1050 K. For the identical operating conditions, the eta(solar-to-fuel-Ca-WS) was further increased up to 38.5% due to the employment of heat recuperation. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study conducted a thermodynamic evaluation of a solar assisted CaO-based water splitting cycle using HSC Chemistry 9.9 software. The results showed that the thermal reduction efficiency increased with the rise in temperature, leading to higher solar energy requirements. Additionally, the energy conversion efficiency of the cycle was further improved through the use of heat recuperation techniques.