LAUSR

Abstract Thermochemical cycle is a promising way for hydrogen production. Although the Gibbs free energy function has been used to assess thermochemical cycle reactions, it is difficult to explain exergy transfer and degeneration. There is no universal principle to explain the mechanism of triggering an endothermic reaction from the viewpoint of exergy. To fill the gap, novel exergy- and energy level-based analysis methods for thermochemical cycle reactions are proposed. Interrelationships of exergy and anergy in thermochemical reactions are analyzed. Energy level equations are built to provide a basic requirement that should be satisfied to trigger a thermochemical reaction. Additionally, a basic principle is proposed to explain the mechanism behind the methods of triggering an endothermic reaction. The results find that the certain exergy (or energy level) standard should be satisfied to trigger a thermochemical reaction. Increasing the exergy input beyond the exergy requirement or decreasing the exergy requirement lower than the exergy supplied by the reaction enthalpy is the basic principle for triggering an endothermic reaction. The proposed analysis methods provide new insights to analyze thermochemical cycle reactions.