Solar Thermal Reduction of Metal Oxides as a Promising Way of Converting CSP Into Clean Electricity on Demand
Abstract
Available main results of full endothermic reduction of different metal oxides with promising for solar thermochemical redox cycles for hydrogen production and electricity generation on demand are compared. New experimental results of preliminary non solar and solar tests related to an influence of such process parameters as the partial pressure of product gases, the rate of heating and cooling, temperature of metal vapours deposit sites on the morphology and purity of reduced metals, apparent kinetic parameters, undesired by-products formation and intensity of reoxidation are discussed. It is shown that pure reduced metals with strong metal-oxygen bond strength as aluminum and magnesium can be obtain in vacuum with fast preheating rate 150-200 degree per minute with temperatures and CO partial pressure at deposit sites no higher than 460-600°C and 0.07-0.1 mbar. Morphology of such reduced metals also strongly depends on deposit temperatures and can vary from conglomerates composed of submicron and nanocrystallines (50-60°C at water cooling deposit site), metallic flakes with spherical or flat micron and submicron particles (200°C about) to metallic plates (400-600°C). The main positive and negative results of different oxides reduction are described and promising ways of future desirable investigations are proposed.
Keywords
Metal oxides, Reduction, Solar thermal, Clean electricity, Csp, Accumulation of solar energy