In the past years thermochemical redox cycles for the production of hydrogen have been proposed and studied. The temperature requirements of these processes are significantly reduced compared to those of direct thermolysis through the introduction of metal oxides, which act as oxygen storage materials. The lower operating temperatures may be reached in solar concentrating facilities, thereby allowing the production of hydrogen from entirely renewable sources. The process is comprised of two reactions, a reduction of the metal oxide, in which oxygen is released, and the oxidation of the reduced oxide by water, in which hydrogen is produced. Generally, the reduction reaction is endothermic and is carried out at a higher temperature than the the slightly exothermic oxidation reaction. To overcome the thermal and time losses associated with the heating and cooling of the solid, the use of isothermal cycles has been proposed, in which the oxidation temperature is maintained at the same level as the reduction temperature. The effect of this operating choice on the overall efficiency has been the object of discussion for the past few years. In this research project we propose to study the efficiency of hydrogen production by water splitting on a manganese ferrite-sodium carbonate mixture. The process is characterized by roughly the same reduction and oxidation temperatures. Its study would therefore provide interesting insight on the effect of the operating temperatures of the reduction and oxidation reactions on the overall process efficiency.
In the past decade, increasing efforts have been devoted to research aimed at reducing our dependence on fossil fuels and increasing the share of renewable energy use. In this framework the possibility of developing decentralised hydrogen production unit is attractive. Traditionally, hydrogen production is carried out through the steam reforming of methane, an energy consuming process which requires the input of fossil fuels both as raw material and to reach the required reaction temperatures.
Water splitting thermochemical cycles bypass the need of methane or other hydrocarbons as raw materials. In addition, if coupled with solar concentrating facilities the energy input could derive entirely or partly from renewable sources.
As discussed above, the main purpose of the research is to evaluate the efficiency of hydrogen production through the thermochemical splitting of water of a mixed sodium carbonate manganese ferrite and compare the obtained value with the efficiencies of other candidate thermochemical processes. The result of this research will not only provide insight on the investigated process, but also contribute to the discussion on the selection of the optimal operating temperatures for water splitting redox cycles.
The method developed within this research could also be applied to other thermochemical cycles.