Assessment of potential groundwater contamination by ground source heat pump operation using solute transport models
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ORIGINAL RESEARCH
Assessment of potential groundwater contamination by ground source heat pump operation using solute transport models Shigeoki Moritani1 · Hirotaka Saito2 · Pyone Win Win3 · Yuji Kohgo2 Received: 20 June 2020 / Accepted: 22 September 2020 © Islamic Azad University 2020
Abstract Globally, over the past few decades, there has been a rapid increase in the use of ground source heat pump (GSHP) systems for heating and cooling purposes. Although these systems are more energy efficient than conventional air source heat pump systems, their association with potential groundwater contamination risks, e.g., the leakage of heat exchanger fluids like glycol, is a major concern. In this study, HYDRUS software was used to simulate the transportation of fluids from such systems into an aquifer. To better understand the transport environment, a geological survey was conducted and a > 50 m deep observation well was dug close to the GSHP installation site. To determine the physical properties of the soil, core samples were collected and analyzed; to determine the flow rate of the groundwater as well as the hydrological properties of the aquifer, measurements were conducted using a velocimeter that was installed in the borehole of the observation well. A laboratory column containing aquifer soil was used to determine drainage breakthrough curves. The hydrological parameters of the soil and the solute were used for the simulation under a virtual groundwater environment. The flow of groundwater resulted in the dispersion of the contaminant from its source, and its concentration was significantly reduced owing to degradation presumedly by biological activity. Additionally, two methods for the elimination of the contaminant from aquifers (enforced biodegradation and decontamination by pumping) were identified. Keywords Confined aquifer · Breakthrough curve · HYDRUS simulation · Ground source heat pump · Groundwater
Introduction A relatively constant soil temperature within a depth range of 50–100 m has the potential to act as an energy source for heat pumps that are used for the heating and cooling of buildings. These so-called ground source heat pumps (GSHPs) have demonstrated a higher energy efficiency compared with air source heat pumps that have been extensively used globally [1]. Currently, owing to recent hot summers, during the construction of buildings, household air conditioners are now installed as a standard in Japan, even in cold northern regions. The use of GSHP systems is expected to * Shigeoki Moritani moritani@hirosaki‑u.ac.jp 1
Faculty of Agriculture and Life Science, Hirosaki University, Aomori, Japan
2
Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan
3
Land Management Group, Murdoch University, Perth, Australia
decrease greenhouse gas emissions from power plants and help curb energy shortages. The majority of the predominantly used GHSPs are closed types, within which an antifreeze fluid solution is circulated through a closed U-tube that is usual
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