Thermochemical model studies of some high temperature solar energy conversion processes

Abstract: This thesis is a summary and discussion of five papers, mainly dealing with processes where solar thermal energy is utilized in the production of chemicals with high energy contents. The products considered in the present work are H2, Al, and Mg. The processes selected have been studied by computer simulation of the equilibrium conditions of the different reactions participating in the total process. Most effort has been devoted to studying two-step cyclic processes for the production of H2 through water splitting. As a result of these studies, it turned out that some supporting chemicals, especially the redox pair FeCl2-Fe304, have promising thermodynamic properties for this type of energy conversion.To obtain the necessary thermodynamic data for the candidate supporting redox systems with the solid solution phases ’(Fe,Co)0’ and (Fe,Co)304, experiments were carried out in the temperature range 970 - 1370 K. A mixture of these two phases, with pre-fixed compositions will generate a definite equilibrium oxygen pressure at a certain temperature. This oxygen pressure was determined, at various compositions and temperatures by using the solid state galvanic cell method. The results obtained were used to simulate the effects of this redox pair in a water splitting process.