Direct Solar Hydrogen Production
at the “Plataforma Solar de Almeria“ (PSA)
In several research and development projects, over the years, various concepts from the laboratory processes to pilot-scale preparation have been created. The direct solar hydrogen production using in thermal processes does not need coal, natural gas or oil as raw materials. Additionally, this process also simply saves the step to converte energy from heat into electricity and the high flaring and transmission losses of the existing electricity system. The German Aerospace Center (DLR) works until today, together with European partners since the 1970s, in exploring the direct production of hydrogen from solar energy.
In a thermochemical cycle processes in which water is split by means of several steps, one or more reactants in the process are recovered and recycled. Several hundred of these procedures are documented and are currently sporadic appearing as "breaking news" messages in the media. There are two groups: one uses inorganic sulfur compounds, such as sulfuric acid, the other method is based on metals or metal oxides, especially iron.
The process, based thermochemical cycle processes, is implementing iron oxide-based reactive material, alternately oxidized and reused again. A coated ceramic structure in a solar receiver-reactor is heated with concentrated solar radiation to about 800 ° C. The hydrogen reacts with the coating, to bound the oxygen and hydrogen is released. In a second reactor, the steam power is heated to about 1,200 degrees C. This escapes the reactive oxygen on the coating and the cycle begins again. (see our grafic)
This procedure has, after initial pilot tests of the Institute of Technical Thermodynamics at the DLR in Germany, its sucessfull dress rehearsal in November 2008 at the Spanish Plataforma Solar de Almeria. The two solar receiver-reactors are mounted in 28 meters high on the so-called SSPS Tower (Small Solar Power System). The units are installed in modular mode, currently designed for 100 kW. The structure is relatively unspectacular, the two reactors have the size of a normal household refrigerator. The already installed sun heliostats (mirrors), automatically following the sun, have a thermal capacity of max. 2.7 MW. The location in Tabernas, with over 3,000 hours of sunshine per year and a direct solar radiation of 1.900 kW / h per square meter provide Europe's best solar power.