Research News

Accidental clogging in geothermal wells reveals need for monitoring to ensure long-term usability

Aquifer thermal energy storage (ATES) system in winter

ATES uses water stored underground and pumped through a system of pipes for heating and cooling buildings.

Credit: Osaka Metropolitan University

Aquifer thermal energy storage (ATES) systems, which use geothermal heat as a renewable energy source, is one of the solutions to reducing fuel consumption and carbon dioxide emission. This system stores heat underground in aquifers, using groundwater as a heat medium. The heat is then extracted as needed according to the season to efficiently heat and cool buildings.

Its use is mainly expanding in Europe, and its widespread introduction is expected in Japan. However, regular inspection is required to utilize these systems without faults.

This fact became evident when a research group led by Specially Appointed Professor Harue Masuda at the Osaka Metropolitan University Urban Resilience Research Center identified clogging that occurred in the plumbing pipe of an ATES well at a facility in Osaka.

In their findings, iron oxyhydroxide precipitation occurred after a vent was accidentally left open, allowing for air to enter the geothermal wells through plumbing pipes. In turn, an oxygen-rich environment formed and iron oxyhydroxide spread through the piping, causing a clog, leak, and subsequent mixing of groundwater between two aquifers at different depths of each well. Fortunately, natural microbial activity resolved the clog and restored the groundwater.

Observation of this chain of events revealed that it is crucial to evaluate the water quality before the well is put into operation, and to continuously monitor for long-term use of the ATES system.

“The results of this research show that geochemical analysis of groundwater, which has not been emphasized in the engineering field until now, is effective and essential for the stable, widespread use of the ATES system,” stated Professor Masuda. “We believe that by proposing a method for monitoring water quality as a guideline, we can establish the ATES system as a technology that can be used for the long term.”

The findings are published in Geothermics.

Funding

This study was financially supported by Mitsubishi Heavy Industries Thermal Systems Inc.

Paper information

Journal: Geothermics
Title: Natural recovery from Fe-oxyhydroxide clogging of a geothermal well in Osaka, Japan
DOI: 10.1016/j.geothermics.2024.103187
Authors: Harue Masuda, Yasuhisa Nakaso, Masaki Nakao, Linri Cui
Published: 28 October 2024
URL: https://doi.org/10.1016/j.geothermics.2024.103187

Contact

Harue Masuda

Urban Resilience Research Center
Email: harue[at]omu.ac.jp

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