Development of Urban-type Geothermal Heat Pump Systems for Minimizing Heat Island Phenomena

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For the optimum design and the evaluation of thermophysical properties of ground, field tests were carried out at experimental heat exchange wells of.50m deep which were newly-drilled in Fukuoka City and Karatsu City. In thermal response tests (TRTs), vertical temperature profiles were measured using optical fiber thermometers and the temperature data were interpreted to develop an estimation procedure of the vertical thermal conductivity distributions with high accuracy. In Fukuoka City, cooling and heating tests were carried out for the collection of long-term operation data. On the basis of the obtained operation record and the geological information at the test site, a numerical model was constructed and validated with field test data for the optimization of well design and operation strategy. In Karatsu City, operation data of an air-conditioning system of 200m2 floor space were collected for one year to develop a system model of a Geothermal Heat Pump (GHP) air-conditioning syste … More m with the integration of the results of TRT and groundwater velocity measurements. At the same location, electrical prospecting of groundwater level was conducted for the exploration of optimum location of GHP systems.For the optimum site selection of GHP systems with the consideration to the advection effect of groundwater flow, field surveys of groundwater flow were carried out in Akita, Chikushi and Fukui Plain, Japan. Groundwater samples were collected at several locations of different geological settings and elevations for the analysis of water qualities and the stable isotope ratio of oxygen and hydrogen. Profiles of ground temperature were also measured with high resolution using a thermister thermometer. On the basis of the above data, groundwater environment maps were developed to investigate the field-scale groundwater flow system. Field-wide numerical models of groundwater flow system were then developed using numerical simulation software, FEFLOW, for estimating the distribution of groundwater velocity, direction and temperature in each plain. Using the numerical model, suitability maps of GHP system were developed for the optimum site selection of future installation of GHP system.Cold heat storage system with the cooling of quarry walls was developed in Hinai Town, Akita. In a rectangular space in a underground quarry of green tuff, horizontal holes and observation holes were drilled. The horizontal holes were connected in series with water pipes to cool the walls with heat pump and to demonstrate the energy saving efficiency of the heat storage system. Air temperatures and those of surface and inside of the walls, etc. were monitored to demonstrate that a cooling space of 0-2℃ could be established with the use of cold heat in winter. Less