The endothermal dissociation of zinc oxide into its elements, followed by t
he exothermal hydrolysis of zinc, is considered as a two-step water splitti
ng thermochemical cycle using high-temperature solar process heat. Thermogr
avimetric measurements were conducted on both reaction steps to elucidate t
he influence of temperature, oxygen partial pressure, inert gas flow rate,
and chemical impurities on the reaction kinetics. The dissociation rate inc
reased with the temperature and mass flow rate of an inert gas, and decreas
ed with the oxygen concentration in the inert gas. The hydrolysis reaction
proceeded faster for molten zinc and for zinc-containing impurities, but a
layer of ZnO prevented reaching completion. The implications on the reactor
design are discussed briefly. (C) 2000 Elsevier Science B.V. All rights re
served.