Hydrogen Production by Solar Thermochemical Water-Splitting Cycle via a Beam Down Concentrator

About 95% of the hydrogen presently produced is from natural gas and coal, and the remaining 5% is generated as a by-product from the production of chlorine through electrolysis1 . In the hydrogen economy (Crabtree et al., 2004; Penner, 2006; Marbán and Valdés-Solís, 2007), hydrogen is produced entirely from renewable energy. The easiest approach to advance renewable energy production is through solar photovoltaic and electrolysis, a pathway of high technology readiness level (TRL) suffering, however, from two downfalls. First of all, electricity is already an energy carrier, and transformation with a penalty into another energy carrier, hydrogen, is, in principle, flawed. The second problem is that the efficiency of commercial solar panels is relatively low. The cadmium telluride (CdTe) thin-film solar cells have a solar energy conversion efficiency of 17%. Production of hydrogen using the current best processes for water electrolysis has an efficiency of ∼70%. As here explained, the concentrated solar energy may be used to produce hydrogen using thermochemical water-splitting cycles at much global higher efficiency (fuel energy to incident sun energy). This research and development (R&D) effort is, therefore, undertaken to increase the TRL of this approach as a viable and economical option.