STEP—A Solar Chemical Process to End Anthropogenic Global Warming. II: Experimental Results

Abstract

Alternative chemical processes are needed to decrease the level of atmospheric greenhouse gases. Experimental support is presented of our STEP theory, which predicted a path to recycle and remove CO2 at high (∼50%) solar efficiency. In STEP (solar thermal electrochemical production) of energetic molecules, electrolysis occurs, heated by excess and renewable thermal energy at high-temperature potentials below that of the room-temperature energy stored in the products. STEP is demonstrated in the efficient formation of metals, fuels, chlorine, and carbon capture. As one example, CO2 is converted to solid carbon, or CO, by distinguishing sunlight that is energy sufficient to drive photovoltaic charge transfer and applying all excess energy to heat and decrease the free energy of the enodothermic CO2 splitting electrolysis. The energy efficiency, based on chemical flow out to solar flow in, is high, at least 34%, and may reach over 50% but will depend on the extent of the solar thermal energy captured for the molten electrolysis. As another example, in an alternative to carbothermal iron production, which is responsible for 25% of worldwide industrial CO2 emissions, iron is produced without CO2 in solar thermal heated molten carbonate. Fe(III) (14 m) (as in the iron ore, hematite) is soluble in molten Li2O and Li2CO3, providing a facile path for STEP iron electrolysis. Also, water is efficiently STEP electrolyzed in molten salts to hydrogen. Finally, of relevance to bleach production and desalinization, chlorine, sodium, and magnesium are formed from the chlorides. STEP provides a different pathway for solar energy conversion, at high efficiency, and is capable of proactively removing carbon dioxide and also generating a range of useful chemicals without greenhouse gas emission.