Processes and materials for solar thermochemical production of fuels and chemical commodities

Abstract

To use heat from carbon-free sources like concentrated solar radiation to drive chemical reactions for the production of transportation fuels or of chemical commodities represents a promising way to replace established industrial processes and to avoid substantial amounts of climate relevant emissions. Recent developments offer attractive medium- to long-term prospects for the provision of chemicals like ammonia, sulfur, phosphates or cement and fuels like hydrogen and synthesis gas. The direct use of solar heat to drive endothermal chemical reactions in a temperature range between 500 and 1800 °C is possible. In the field of solar fuels production so-called thermo-chemical cycles are a viable option to produce hydrogen from water or syngas from water and CO2 at an acceptable temperature level. The most prominent examples are cycles from the so-called sulphur family, the hybrid sulphur and the sulphur-iodine process, and redox cycles applying metal/metal oxide pairs or multi-valent metal oxides which are capable to reversible incorporate oxygen in this lattice. The present analysis gives an overview on recent developments and the state-of-the art of high temperature fuels or chemical commodities producing solar processes. It will have a look on the most important performance parameters involved and will give an outlook on further potential and necessary developments. In addition we look at variants of such processes offering the chance to use them for thermo-chemically storage of solar heat or for air separation.