A catalyst-assisted chemical heat pump system, consisting of a reversible hydrogenation couple and distillation, is able to provide 200℃ heat using a 90℃ heat source and a 30℃ coolant. In order to enhance the thermal efficiency of this system, conversion of low-quality heat into chemical energy was accomplished efficiently under boiling conditions by use of dehydrogenation catalysts in liquid-film states, where the catalyst/solution amount ratios were large enough for attaching the catalyst layer to the reactor wall directly. Under boiling and refluxing conditions, superheated catalysts gave an equilibrium-exceeding conversion (29.6 %>11.1 % at 90℃) at a high enthalpy efficiency (34.4 %).

A 2-propanol/acetone-based thermodriven cell, consisting of 2-propanol dehydrogenation at the negative electrode and acetone hydrogenation at the positive electrode, is possible to convert low-quality thermal energy lower than 100℃ into electric energy directly. An efficient hydrogen-spillover ability was verified by use of carbon-supported metal catalysts under boiling and refluxing conditions, where the catalyst-to-substrate amount ratio was important. The size effect of palladium fine particles on hydrogen spillover was remarkable. It was found that the composite effect of palladium with ruthenium took an essential role as well.

All kinds of energy resources, including intermittent energies such as solar radiation and the wind power, can be converted and unified into the one type of energy, namely hydrogen, Hence hydrogen fuel cells facilitate us to build an energy system that supplies robust, clean, and economical electricity. This paper reports investigations on the structure of fuel cell hydrogen energy system in the light of the best energy mix,a nd with the aid of Genetic Algorithm.

This study aimed to prepare a Ni-M(Hhydride of hydrogen storage alloy) rechargeable battery with a large capacity for a solar vehicle. The energy density of the prepared battery was about 46 Wh/kg. After 170 charge-discharge cycles, the initial capacity was found to be decreased to 75% Analyses of charge-discharge characteristics of this battery were made based on data obtained from actual running tests using a solar vehicle. Discussion is made on the effect of KOH pretreatment of a Mm-Ni alloy used for the negative electrode and the performance of the prepared Ni-MH battery.

As an example of estimating the environmental impact of hydrogen energy system, we calculated the emission of CO₂ at hydrogen production and at transportation through gas pipelines. The emission was estimated using environmental I/O table. The CO₂ emission depend strongly on the kind of primary energy. For the energy transportation, less emission was obtained in case of long distance transportation using tubes inadequate diameters than electric power transportation for the same amount of energy.