This paper presents the introduction condition of a passive type hydrogen storage system according to the basic hydrogen absorption and desorption experiment using several hundred g alloys. The annealed MmNi_4.6Al_0.4 was selected as a hydrogen storing material for the residential use in terms of equilibrium pressure and Plateau slope. When the hydrogen was discharged from or charged toMmNi_4.6Al_0.4, the endothermic or exothermic amount was 21.7, 18.5 W per 1NL/min hydrogen respectively. It was cleared that the hydrogen was absorbed in the condition of the ambient temperature 10～28℃ and the absorption flow rate less than 0.2NL/(min･kg). And also, it was cleared that more than 95% of total hydrogen storage capacity was desorbed in the condition of the ambient temperature 18～28℃, and the flow rate less than 0.34NL/(min･kg).

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Although conventional life cycle assessment (LCA) is a useful tool to evaluate environmental impacts of products, there are some cases where it cannot provide sufficient information for environmental policy making due to the analytical perspective. The objective of this study is to develop a new method that contributes to making policy on the introduction of environmentally sound products into a society from mid- and long-term viewpoints. An inter-temporal linear programming model was developed that determines an optimal schedule for the introduction of environmentally sound products to minimize the cumulative environmental burden over time on a social scale. The cumulative burden is calculated across the life cycle of all the products in a society considering the lifetime distribution of the products. The model was applied to explore an optimal introduction of green cars and the maximum CO₂ reduction potential under socio-economic constraints in Japan. The empirical study found that optimal configuration within limited budget consists of not only more high-efficient cars such as hybrids and electrics but also diesels. That is, it is effective for minimization of CO₂ emissions that the limited budget is not concentrated on the best car but widely distributed some types of green cars.

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