Geochemical and hydraulic analysis of groundwater for heat utilization around Sakuragaike in Nanto City, Toyama Prefectu
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ORIGINAL ARTICLE
Geochemical and hydraulic analysis of groundwater for heat utilization around Sakuragaike in Nanto City, Toyama Prefecture, Japan Haruka Mori1 · Akira Ueda1 · Yosihisa Ogawa2 Received: 25 February 2020 / Accepted: 29 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Oxygen isotopes, major and minor chemical compositions of 23 groundwater and 5 river water samples from the southern part of Nanto City were analyzed. From these results, the possibility of groundwater heat utilization was discussed. The water temperatures fluctuated between summer and winter. The groundwater in this area nearby Sho River is strongly influenced by river water infiltration and most groundwater in other areas is considered to be derived from precipitation. The Ca2+, HCO3−, and S iO2 concentrations increase due to reactions with rocks during water flow from the surrounding mountains to the alluvial fan areas. In some areas, Fe scale (goethite) is assumed to be precipitated from groundwater in heat exchangers and water pipes. Based on these results, an area around Sakuragaike potentially suitable for utilization of groundwater heat was selected for study. Keywords Groundwater · Hydrochemistry · Heat utilization · Oxygen isotope
Introduction At present, interest in natural energy sources has intensified worldwide, and utilization of underground heat is one of a number of renewable energy types that have attracted attention. Geothermal heat utilizes the temperature difference between the ground and air temperatures because ground temperatures at depths of approximately 10 m or greater below surface are close to the annual average air temperature of the land. Room heating and cooling using geothermal heat pumps (ground source heat-pump system: GSHP) are utilized worldwide (Huttrer 1997; Diao et al. 2004; Lee and Hahn 2006; Russo et al. 2011; Ni et al. 2011), and the total installed capacities are greatest at approximately 12,000 MW in the USA, approximately 5210 MW in China, and approximately 4460 MW in Sweden (Lund et al. 2010), * Akira Ueda [email protected]‑toyama.ac.jp 1
Department of Environmental Biology and Chemistry, Faculty of Science, University of Toyama, 3190, Gofuku, Toyama 930‑8555, Japan
Chuetsu-Kogyo Company, 800 Noguchi, Nanto, Toyama 939‑1844, Japan
2
whereas Japan, at present, lags with approximately 44 MW of installed capacity (Ministry of the Environment 2015). Geothermal heat pumps are generally divided into two types: open and closed. In the closed type, a heat exchange facility is installed by drilling a well and underground heat is recovered by passing heat-containing fluid through a U-shaped pipe. For the open heat-pump type, groundwater is pumped from the ground and is used directly. Therefore, this second type can be used only where there is groundwater, the water quality changes because of the return of groundwater to the ground, and the problem of chemical precipitation (scale) in the heat exchanger must be considered. However, the open type has the
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