日本エネルギー学会誌
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84 巻 , 2 号
選択された号の論文の4件中1~4を表示しています
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  • 醍醐 市朗, 若松 貴史, 山末 英嗣, 石原 慶一
    84 巻 (2005) 2 号 p. 119-125
    公開日: 2010/06/28
    ジャーナル フリー
    The improving energy efficiency for transportation sector in Japan is an important factor to resolve the problem of global warming. However, there are few researchers considering physical as well as sociological evaluation of the energy efficiency with respect to various kinds of transportations. The purpose of this study is to evaluate the physical and sociological energy loss by the use of “overall friction coefficient” (OFC). It is defined as the energy used for transportation divided by transported mass, transported distance and gravitational constant. The data concerning automobiles, trains, ships and planes are collected for both passenger and cargo. Each value of OFC is plotted as a function of the average speed. Three expressions are presented for three different transportations; ideal cargo transportation, ideal passenger transportation and real passenger transportation. It is noted that the OFC for the passenger transportation shows a minimum around an average speed of 110km/h showing the best energy efficiency at around this speed.
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  • Kazuya KUNITOMO, Yasushi TAKAMOTO, Masaaki NAITO, Jun-ichiro YAG
    84 巻 (2005) 2 号 p. 126-133
    公開日: 2010/06/28
    ジャーナル フリー
    It is possible to improve the productivity and flexibility of the blast furnace operation and also to substitute energy sources in the pig iron production processes by combining the partial reduction process using low carbon content energy sources such as natural gas with the blast furnace process. In this case, the blast furnace process conducts the final reduction and melting of the partially reduced iron ore produced in the partial reduction process. The production rate of the partially reduced iron ore is much higher than that of the fully reduced iron one, because the reduction rate tends to decrease remarkably as the reduction degree rises. As for the technological problems of using the partially reduced ore in the blast furnace process, the deadman temperature might decrease if a large amount of fine iron ore that has been partially reduced is injected. However, if the appropriate amount is used, the reducing agent rate may lower, and productivity can be improved without decreasing the deadman temperature. This method not only reduces energy consumption in the existing blast furnace ironmaking process, but also reduces the energy consumption related to carbon dioxide emission in the total hot metal production processes, including the partial reduction process.
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  • 小田 潤一郎, 松橋 隆治, 吉田 好邦, 高嶋 隆太
    84 巻 (2005) 2 号 p. 134-141
    公開日: 2010/06/28
    ジャーナル フリー
    In this paper, we consider the investment risk of nuclear power plants using the real options approach. It is essential that the Japanese society evaluate the investment risk, because nuclear power plants are facing definite uncertainty and Japanese governments intend to promote and assist nuclear power plants through subsidies and policy actions.
    We assumed that the wholesale market prices of electricity constitute the definite uncertainty and that the wholesale market prices follow the geometric Brownian motion with drift. Using the Bellman equation and a lattice framework, we evaluated the value of investment opportunity, the value of equipment, and the critical prices that are optimal prices to invest in a nuclear power plant in the finite time horizon.
    This analysis shows that higher volatility of the wholesale market prices would give power companies lower incentive to construct electric power plants, particularly capital-intensive power plants. In order to deliberate and hold the Japanese governments accountable for the economics of nuclear power plants, multifaceted evaluation is needed.
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  • 本庄 孝子, 井田 民男, 渕端 学, 佐野 寛
    84 巻 (2005) 2 号 p. 142-148
    公開日: 2010/06/28
    ジャーナル フリー
    Woody biomass is a hopeful energy resource to reduce greenhouse gas emission, and it is widely used in north Europe. Little amount of woody biomass is utilized for energy production, although Japan has much forest. Because most forests in Japan are located in steep mountain ranges. If woody biomass can be changed to high energy density fuel, the transportability of fuel will be improved, and the woody biomass will be potentially introduced in Japan. The purpose of our study is to improve the calorific density of cellulose by hot-press method, and to produce the semi-carbonized pellets. Cellulose is a main component of woody biomass. The cellulose is gradually dehydrated during the carbonization. The organic volatiles, however, are lost at the same time, and the energy yield of the carbonized cellulose is decreased. Therefore, the semi-carbonizing conditions, at which maximum energy yield can be achieved, should be investigated. In addition, the semi-carbonized pellet considerably contains tar in it. It is good for long storage because the tar becomes an antiseptic. This study examined to find the optimum condition of semi-carbonization for a preparation of pellet fuel.
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