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.

抄録全体を表示

地熱熱水は貯留層温度，pH，貯留層岩石成分の影響を受け複雑な組成を有し，これらの特性は地表設備ならびに地下の貯留層において生じるシリカの沈殿に様々な影響を及ぼしている。本研究では地熱貯留層において熱水中の懸濁物質および熱水pH がシリカの沈殿に及ぼす影響を明らかにする目的で，アモルファスシリカに対する飽和比が2.5 の人工熱水を作成し，熱水中の懸濁物質濃度（0, 0.1, 1.0ppm）およびpH（pH8, pH5.5）を変えて人工熱水を多孔質層に流量一定および温度一定（80℃）条件下で供給する実験を行った。長さ5cm，内径4mm のガラス管に石英砂を充填し、5 本直列に接続して全長25cm の多孔質層を作成した。また，懸濁物質としてベントナイトを使用した。実験終了後は，多孔質層内の石英砂を取り出し，SEM による沈殿物の形状観察を行った。その結果，懸濁物質の濃度が高くなると多孔質層の平均浸透率が大きく低下するが，pH が低くなるとその低下速度が緩和されることを明らかにした。また，SEM 観察により石英砂表面の沈殿物が多いほど浸透率が低下していることがわかった。

抄録全体を表示