Journal of the Japan Society of Engineering Geology
Online ISSN : 1884-0973
Print ISSN : 0286-7737
ISSN-L : 0286-7737
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Volume 51, Issue 6
Special Issue
Displaying 1-5 of 5 articles from this issue
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Original Article
  • An Attempt of Installation Potential Assessment on Groundwater Heat Pumps
    —Studies on Continuity of Impermeable Layers and Groundwater Chemistry—
    Tomoyuki OHTANI, Kohji KAMIYA, Kozue KANAI, Yu SAWAMURA, Satoru KOJIMA ...
    2011 Volume 51 Issue 6 Pages 257-264
    Published: 2011
    Released on J-STAGE: March 31, 2013
    DOIhttps://doi.org/10.5110/jjseg.51.257
    JOURNAL FREE ACCESS
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     The continuity of impermeable layers and groundwater chemistry are studied using geological and hydrological information in Gifu city to assess installation potential of groundwater heat pumps. For former study, an estimation of sedimentation environment by diatom fossils and a measurement of water level change by groundwater pumping-up are performed. Extracted diatom fossils are composed of the fresh water assemblage, and suggest that the formation with these fossils was sedimented at the back marsh and its continuity is not good. The measurement result of groundwater level change shows that two aquifers above and under the impermeable layer are connected hydrologically. The latter study revealed that the groundwater with low dissolved contents is widely spread in the urban area of Gifu city. Although the contents of free carbon dioxide are higher than the recommended value in most areas, approximate <10mg/L of free carbon dioxide is assumed to be possible to utilize of groundwater heat pumps based on the present utilization situation. The result of continuity of impermeable layers shows that the influences of groundwater pumping-up for heat pumps are not concentrated into one aquifer due to aquifer connection. Groundwater chemistry reveals that the groundwater can be directly used in the heat pumps due to their low resolved contents.
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Report
  • A Ground Source Heat Pump System in Central Tokyo
    —A Case Study of Retrofit for a Small Office Building—
    Masakatsu SASADA, Shinji TAKASUGI, Masayuki TATENO
    2011 Volume 51 Issue 6 Pages 265-272
    Published: 2011
    Released on J-STAGE: March 31, 2013
    DOIhttps://doi.org/10.5110/jjseg.51.265
    JOURNAL FREE ACCESS
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     A ground source heat pump system was installed for a small office building in Central Tokyo. It is made up of a water-source heat pump unit, 8 boreholes of 75 m deep for heat exchanger, and polyethylene pipes. Coefficient of Performance (COP) of the heat pump system was 4.3 in average for the first year. Forty nine percent of electricity was reduced by the ground source heat pump system, compared to the conventional air source heat pump system which previously worked there. Geology of the building site is unconsolidated Quaternary sediments of gravel, sand and silt, and their thermal conductivity was estimated to be 1.8 W/(m·K). Thermal energy of 51 GJ was produced from the ground source and that of 53 GJ was discharged there during the first year. Such good balance of subsurface heat exchange suggests sustainability of the heat pump system working for the Sasada Building.
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  • Geothermal Development and Utilization in Hachijojima Island
    Kazuo MATSUYAMA, Yasuto TAKEDA, Masahiro SHIMODA, Koichi TAKAMURA, Tak ...
    2011 Volume 51 Issue 6 Pages 273-279
    Published: 2011
    Released on J-STAGE: March 31, 2013
    DOIhttps://doi.org/10.5110/jjseg.51.273
    JOURNAL FREE ACCESS
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     Exploitation of geothermal energy in Hachijojima was started at 1984 by Tokyo Electric Power Company (TEPCO). The Geothermal Development Promotion Survey was carried out between 1989 and 1991, by New Energy and Industrial Technology Development Organization (NEDO). In this government project, a high potential geothermal reservoir with temperature of more than 300 centigrade was confirmed within the subsurface of southern Mt. Higashiyama area.
     This government project was followed by the investigation for detail design and construction of power plant by TEPCO, and three production wells were successfully drilled in 1995. Commissioning of geothermal power plant was started on 25th March 1999 with one of these three wells an average of 2000 kW consistent power supply. This power is used as a base energy of the whole island power supply, and contributes an equivalent reduction of 40% of CO2 emissions compared to the similar capacity diesel powered generation. During winter season, power plant supplies residual heat source to adjacent green houses by circulating water system.
     Based on this geothermal exploitation, the development of hot springs has been started since 1992 by Hachijo-machi. As a result, four hot springs for public bathing facilities are operating today, and about 170,000 people are enjoying the hot spa every year.
     This report elaborates the history of geothermal development and exploitation, geological setting of geothermal resource in Hachijojima Island and recent utilization of residual heat sources from the geothermal power plant.
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  • Subsurface Temperature Increase Caused by Effects of CO2 Aquifer Storage Experiment
    Akinobu MIYAKOSHI, Toshiyuki TOSHA, Shinichi TAKAKURA
    2011 Volume 51 Issue 6 Pages 280-287
    Published: 2011
    Released on J-STAGE: March 31, 2013
    DOIhttps://doi.org/10.5110/jjseg.51.280
    JOURNAL FREE ACCESS
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     An experiment of CO2 gas injection into the shallow confined aquifer has been conducted, and subsurface thermal environment change caused by effects of CO2 gas injection was observed. Subsurface temperature increase was found in the injected aquifer, excepting the temporary drop of temperature in the injection well. The part of subsurface temperature increase was formed from the depth of 44m to 48m, and the temperature increase was most significant around the upper surface of the aquifer at the depth of 47m. This suggests that injected CO2 gas expanded along the upper surface of the aquifer. Moreover, groundwater quality variation showed decrease of pH and increase of ORP accompanying the dissolution of CO2 gas. It was considered that the increase of subsurface temperature was caused by generated heat accompanying oxidization of iron minerals in the aquifer. The part of temperature increase was recognized 35 days after the end of the injection, although it was shrinking with time progress. This suggests that effects of subsurface thermal environment change remain for a long period in spite of the shallow aquifer around the depth of 50m.
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