Hydrogen produced by the water-splitting reaction is one of the alternate sources derived from fossil fuels. However, the present systems for the hydrogen production still require the extra energy or processes such as heating, milling and adding the chemical agent. The hot springs in Japan are naturally in high temperature and in wide range of pH. We investigated the combination of hot spring water and waste aluminum that are appropriate for hydrogen production without extra energy. Here, we used waste aluminum for reducer of water-splitting reactor. The hydrogen production system in Onsen (hot spring) area has a potential to promote not only the environmental and energy problems but also the activation of the local community as the system of “local production for local consumption”. In this study, the effects of the characters of hot springs and the conditions of the hydrogen generator system were revealed by the laboratory experiments. The water-splitting reaction was enhanced by using the hot spring water of (1) lower pH (< 2), (2) higher temperature, and (3) higher ratio of HCl/H2SO4. The concentration of cations in the fluid is not related to the reaction rate of hydrogen production. The prototype of the hydrogen generator for the water splitting reaction by using the acidic hot spring water and waste aluminum was developed and used in two type systems: batch and flow-through. The laboratory experiment by using the original generator revealed that hydrogen production was more efficient in the flow-through system because of constant pH value of fluid.
