著者

盛田 耕二

出版者

公益社団法人 日本地下水学会

雑誌

地下水学会誌 (ISSN:09134182)

巻号頁・発行日

vol.36, no.3, pp.243-257, 1994-09-20 (Released:2012-12-11)

参考文献数

32

被引用文献数

2

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The realization of heat extraction from magma has long been one of the dreams of mankind because of its huge potential as an energy source. However, current levels of technology, materials and understanding of magma seem to be far from the levels needed. On the other hand, several potential geothermal resources including Hot Wet Rock, Super Hot Rock and magma origin fluid systems lie on the way toward magma. These potential resources should provide suitable places for developing or improving technologies or materials, and for acquiring a deeper understanding of magma.The author's strategy is to begin an R&D program with easier or shallower potential resources, and realizing power generation with them, progressing toward magma step by step. In order to achieve this strategy, the development of a closed system downhole heat exchanger is essential. The author has been proposing the Downhole. Coaxial Heat Exchanger (DCHE) system and carrying out studies on it assuming Hot Wet Rock as the first target.By means of an experiment carried out in Hawaii, it was proved that a highly efficient DCHE is technically feasible and works as predicted. Also, it was indicated by a feasibility study that the. possibility of the practical use of the DCHE system is very high. The next step is to demonstrate the DCHE's ability to produce more than 5 MW / DCHE (the criterion for economical power generation from a middle to long term point of view) with a 3,000m long DCHE at Hot Wet Rock and at the same time to proceed with the development of technologies necessary for the realization of the practical use of the system.On the other hand, there is another possible application of the DCHE. A combined DCHE-heat pump space heating system makes possible the utilization of generally distributed shallow and low quality geothermal resources. This system is applicable for wherever space heating is needed. Hence, huge amounts of thermal energy can also be supplied with the combined heating systems. The author intends to initiate studies regarding the space heating system.Thus, the degree of contribution of the DCHE system in energy and environmental issues may be the greatest among the various heat extraction methods and conventional geothermal steam or brine extraction methods.

著者

盛田 耕二 藤田 勉 杉本 静哉 山田 恭暉 向井 良一

出版者

THE GEOTHERMAL RESEARCH SOCIETY OF JAPAN

雑誌

日本地熱学会誌 (ISSN:03886735)

巻号頁・発行日

vol.14, no.1, pp.29-45, 1992-01-25 (Released:2010-02-05)

参考文献数

3

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The purpose of this study was to clarify the level of thermal output per DCHE at which power generation using a downhole coaxial heat exchanger (DCHE) becomes economical. Another goal was to clarify the geothermal resources favourable for this system. The following conclusions are drawn in this paper: (1) When heat is transferred only by conduction in the formation as in Hot Dry Rock, the power generation sytem appears to be uneconomical. On the other hand, in the case of Hot Wet Rock where the convective heat transfer mechanism is dominant, there appears to be a greater possibility of the realization of this system. (2) In the case in which the estimated net thermal output after one year of operation was 10.4 MWt/DCHE, the adjusted mean power generation cost for 15 years of plant operation under the current subsidy system was estimated to be 16.4 Yen/kWh. In this case, the power generation system might become economical in the near future. Hence, under conditions similar to those assumed in this study, 10 MWt/DCHE of the net thermal output is though to be a good criterion for judging whether the system is practical or not. In order to investigate the possibility of the realization of this system and to clarify the favourable characteristics of the formation in further detail, it is essential to accumulate in-situ data carrying out heat extraction experiments in high temperature and permeable formation.