SOLAR CHEMICAL

Solar chemical is any process that harnesses solar energy by absorbing sunlight and using it to drive an endothermic or photoelectrochemical chemical reaction Prototypes, but no large-scale systems, have been constructed.One approach has been to use conventional solar thermal collectors to drive chemical dissociation reactions. Ammonia can be separated into nitrogen and hydrogen at high temperature and with the aid of a catalyst, stored indefinitely, then recombined later to release the heat stored. A prototype system was constructed at the Australian National University].Another approach is to use focused sunlight to provide the energy needed to split water via photoelectrolysis into its constituent hydrogen and oxygen in the presence of a metallic catalyst such as zinc. Other research in this area has focused on semiconductors, and on the use of examined transition metal compounds, in particular titanium, niobium and tantalum oxides Unfortunately, these materials exhibit very low efficiencies, because they require ultraviolet light to drive the photoelectrolysis of water. Current materials also require an electrical voltage bias for the hydrogen and oxygen gas to evolve from the surface, another disadvantage. Current research is focusing on the development of materials capable of the same water splitting reaction using lower energy visible light.Solar thermal energy also has the potential to be used directly to drive chemical processes that require significant amounts of process heat, including at high temperatures that can be otherwise quite hard to attain.