Where = heat of formation of water at standard conditions (the energy that is released when hydrogen bonds with oxygen), [kJ]= heat inputs, [kJ]W = work inputs to system (pumping, compression, etc), [kJ]= efficiency of conversion of various pumps, compressor, etc. In 1969, an “International Round Table on Direct Production of Hydrogen with Nuclear Heat” was held at Ispra, Italy. Twenty-four cycles resulted from this initiation of study . The Ispra project resulted in bringing the concept of thermochemical cycles from a purely theoretical idea to a potentially viable method for sustainable hydrogen production. At present, there have been nearly 300 proposed cycles . Though thermochemical cycles have yet to be scaled-up to any sort of commercial capacity, they are regarded as potentially being highly efficient, sustainable, inexpensive, large scale hydrogen production methods. In general, the selling point behind such methods is that they theoretically require only water and heat, while all intermediate reactants and products are recycled in a closed process. Similarly, the only outputs of a thermochemical process are hydrogen and oxygen. Though promising, thermochemical cycles are not as easy to implement as they look on paper. Undesirable side reactions, complicated separation schemes, and corrosion are just some of the problems still plaguing thermochemical hydrogen production and hindering a demonstrable laboratory-scale process from one that is commercially viable on a large-scale. The most heavily studied purely thermochemical cycle is the Sulfur-Iodine Cycle, shown in, which was studied extensively by General Atomics throughout the 1970s and 1980s. Presently at Oregon State, the Yokochi Group in the Department of Chemical, Biological, and Environmental Engineering is investigating alternative solvents for the highlight reaction in Figure 1, the Bunsen Reaction, in order to streamline downstream separation processes and thereby significantly improve overall process efficiency. This cycle is promising; theoretical calculations show that this cycle can be up to 51% efficient .
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