(258a) Thermodynamic Efficiency Analysis of the S-I Process for Nuclear Hydrogen Production

           The Sulfur-Iodine process for thermochemical
water decomposition (1) is considered a leading candidate for large-scale
production of hydrogen using nuclear energy.  Since the nuclear plant will
likely be the biggest component of the capital cost, net thermal efficiency,
which is a measure of the hydrogen fuel value obtained per unit of nuclear
reactor heat output, will be a key determinant of economic feasibility.  Many
analyses of the net thermal efficiency have been carried out, with results
ranging from 35% to 57%, depending strongly on system assumptions and often on
results from models which are subject to considerable uncertainty (1-4).  This
work develops a procedure to calculate a set of upper-limit efficiencies that
minimize model dependence and maximize generality through careful statements of
overall, sectional and equipment-based system reversibilities and integrated
energy utilization (5).  From these results, extensions are made to determine
the consequences of process changes, as well as their sensitivities, either by
modification of flows and states or by expected corrections to model
predictions based on data and other information.  This effort is intended to
step toward a reliable benchmark procedure for objectively evaluating
alternative processes, a way to improve existing processes, and a path to focus
needed fundamental research.

References

           1. L.C. Brown, G.E. Besenbruch, J.E. Funk, A.C.
Marshall, P.S. Pickard, S.K. Schowalter, " High efficiency generation of
hydrogen fuels using nuclear power; DE-FG03-99-SF21888, Final technical report
for the period Aug. 1, 1999 through Sep. 30, 2002", La Jolla, CA: General Atomics Corp. report GA-A24285, Jun. 2003.

           2. G. Berry, Encyclopedia of Energy,
"Hydrogen Production", Vol. III, Elsevier, 2004, p. 253.

           3. S. Goldstein, J. Borgard, X. Vitart, Int.
J. Hydrogen Energy, 2005, 30, 619.

           4. S. Kasahara, G.-J. Hwang, H. Nakajima, H.-S.
Choi, K. Onuki, and M. Nomura, ?Effects of Process Parameters of the IS Process
on Total Thermal Efficiency to Produce Hydrogen from Water?, J. Chem. Eng. Japan 36(7), 887-99 (2003).

           5. J. de Swaan Arons, H. van der Kooi, K.
Sankaranarayanan, "Efficiency and Sustainability in the Energy and
Chemical Industries", Marcel Dekker, 2004.