Journal of the Geothermal Research Society of Japan
Online ISSN : 1883-5775
Print ISSN : 0388-6735
ISSN-L : 0388-6735
Volume 37, Issue 4
Displaying 1-3 of 3 articles from this issue
Article
  • Gaurav SHRESTHA, Youhei UCHIDA, Mayumi YOSHIOKA, Hikari FUJII, Seiichi ...
    2015 Volume 37 Issue 4 Pages 133-141
    Published: October 25, 2015
    Released on J-STAGE: April 25, 2016
    JOURNAL FREE ACCESS
    Assessment of development potential of ground-source heat energy in a regional scale basis is necessary for the best suited design of ground-source heat pump (GSHP) system and its sustainable growth in Japan. Evaluation of usage potential of GSHP system in Tsugaru Plain was conducted in this study, where field survey data of groundwater and subsurface temperature were not sufficient enough as observation wells were lacking. In order to comprehend groundwater flow system and subsurface temperature distribution of the plain, Shrestha et al. (2015) developed a 3D field-wide analysis model and verified it by incorporating the results of thermal response tests, in absence of observed data. In Shrestha et al. (2015), distribution map of effective thermal conductivity was prepared, which was overlaid with the calculated subsurface temperature distribution map in GIS, and a potential map was prepared.In this study, the potential assessment method used in Shrestha et al. (2015) was upgraded by developing potential maps for GSHP system with a new approach, using a performance curve of particular heat pump and ground-heat exchanger model. Based on local topography, geology and the results of the field-wide analysis model, single ground heat exchanger models were constructed at 11 locations in the plain, and heat exchange simulations were conducted. Outputs of the simulations were utilized to prepare potential maps showing spatial distribution of heat exchange rates and coefficient of performance (COP) of heat pump. For COP estimation, the performance curve of heat pump was used. Distribution map of COP including operation cost of the heat pump was prepared with the aim of illustrating economic efficiency of the GSHP system, which is unique to this study. These potential maps prepared for space-heating purpose are significant for proper site selection of the GSHP system, and they can assist for optimum design and economic feasibility of the system.
    Download PDF (1913K)
  • Loren TUSARA, Ryuichi ITOI, Rie YAMASHIRO, Daisuke FUKUDA, Yoshitaka K ...
    2015 Volume 37 Issue 4 Pages 143-152
    Published: October 25, 2015
    Released on J-STAGE: April 25, 2016
    JOURNAL FREE ACCESS
    The complexity of the geothermal water composition as affected by the reservoir temperature, brine pH and composition of rock mass among others would result in different effects in the silica deposition process in the surface facilities and in the reservoir. The effect of the suspended solids in the silica deposition in the geothermal field is herein investigated under different suspended material concentration (0, 0.1 and 1.0 ppm) and at varying pH (pH8 and pH5.5) of silica-supersaturated synthetic brine with respect to amorphous silica with saturation ratio of 2.5. The effect of suspended material in the solution is shown to have caused a significant decrease in the permeability of the porous column only in the presence of supersaturated silica in the solution. To account for the physical change in the porous medium upon deposition of suspended particles, the average permeability of the porous medium was measured during the course of the experiment and the filling material of the porous medium was observed under SEM at the end of the experiment to characterize for the morphology of the solid deposits along the porous medium. Decrease rate of the permeability hastens for higher concentration of suspended material in the synthetic brine. It slows down upon lowering the brine pH with the same suspended material concentration. These changes in the permeability of the porous medium were also observed in the SEM images as relative amount of the solid deposits.
    Download PDF (2025K)
Report
feedback
Top