Practical application of high-efficiency ground source heat pump system utilizing groundwater flow generated near pumping wells

2022 Fiscal Year Final Research Report

• Project/Area Number: 19H02655
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 31020:Earth resource engineering, Energy sciences-related
• Research Institution: Akita University
• Principal Investigator: Fujii Hikari 秋田大学, 国際資源学研究科, 教授 (80332526)
• Co-Investigator(Kenkyū-buntansha): 内田 洋平 国立研究開発法人産業技術総合研究所, エネルギー・環境領域, 研究チーム長 (90356577)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 地中熱利用 / シミュレーション / 地下水 / 温暖化対策

Outline of Final Research Achievements

In the heating and cooling test in the Akita Plain, the heating COP was improved by about 0.5 due to the groundwater flow despite the water level drop caused by pumping up water in winter. Sensitivity calculations using a numerical model showed that the heat exchange well performance was further improved by increasing the pumping rate, but the rate of improvement gradually decreased. A potential mapping in the same plain showed that the length of the heat exchange well can be reduced by up to 30% due to artificial groundwater flow around the pumping well, and that there is no effect of pumping up to 3 km away from the pumping well.
In the thermal response test in the Yamagata Basin, as in the case of the Akita Plain, a large improvement in the heat exchange capacity was observed with an increase in the amount of pumped water. No clear correlation was found between the well distance between and the improvement of the heat exchange capacity.

Free Research Field

石油天然ガス・地熱開発工学

Academic Significance and Societal Importance of the Research Achievements

揚水井が地盤中に発生させる広範囲な地下水流れをエネルギー効率改善という点からから着目して利用した例は国内外に見られず，本研究成果は学術的意義が高いと考えられる。また，本研究では天然の地下水流れに基づいて構築した地下水流動系モデルと，地域の揚水井の設置状況調査を統合させてGSHPポテンシャルマップを構築するが，これは国内外で例を見ず独自性の高い試みと判断される。
さらに，本研究成果は温暖化対策の切り札と考えられている地中熱利用冷暖房システムの高効率化に寄与し，普及を促進すると判断されるため，本研究は温暖化対策やカーボンニュトラルの達成へに貢献し，社会的意義が大きいと考えられる。