Solar Thermochemical Production of Syngas from H2O and CO2─Experimental Parametric Study, Control, and Automation

Abstract

We report on an experimental parametric study performed on a modular and fully automated solar fuel system for the solar-driven thermochemical splitting of CO2 and H2O. Concentrated solar energy is used as the source of high-temperature process heat for effecting a ceria-based redox cycle, producing syngas with a tailored H2/CO ratio. We determine the influence of the main operational parameters (namely: pressure, reduction-end and oxidation-start temperatures, CO2 and H2O mass flow rates) on the key performance indicators, such as the specific fuel yield, molar conversion, and solar-to-fuel energy efficiency. We show how the syngas product quality can be tailored for Fischer-Tropsch synthesis by selecting adequate oxidation conditions, eliminating the need for additional downstream refining of the syngas. The entire solar fuel system is fully automated based on real-time product gas analysis and feedback control loops, and can be further extended with an auto-optimization scheme that executes online mass and energy balances to guide performance improvement. An example of a solar run consisting of fully automated consecutive redox cycles is presented to show the implementation of this control scheme for the optimization of the solar fuel system.