Multi‑sense monitoring using Distributed Fiber‑Optic Sensing for temperature, groundwater flow and acoustics in Aquifer Thermal Energy Storage Systems

Aquifer Thermal Energy Storage (ATES) systems play an increasingly important role in balancing urban heating and cooling demand. Their sustainable operation requires high‑resolution monitoring of subsurface thermal and hydraulic processes, particularly the movement of thermal plumes, groundwater flow dynamics, and operational disturbances during injection and extraction. Traditional monitoring approaches provide only sparse spatial information, limiting the ability to characterize key ATES behaviors. Distributed fiber‑optic sensing (DFOS) offers a step‑change in monitoring capability by enabling continuous measurements along the full depth of wells and monitoring infrastructure.

We present a use case of the ATES system on the Deltares campus in Delft using a multi‑sense DFOS approach that combines Distributed Temperature Sensing (DTS), Active‑Heating DTS (AH‑DTS) and Distributed Acoustic Sensing (DAS). DTS provides the temperature distribution along the well filters and how this evolves over time to get insights into plume migration. AH‑DTS provides estimates of (changes in) groundwater flow velocity by analyzing heating curves measured by the fiber, enabling analysis of preferential flow at specific depth intervals paths. DAS can capture hydrodynamic and operational acoustic signals associated with injection, production, and well hydraulics, offering additional insight into transient system behavior.

Integrating DTS, AH‑DTS and DAS provides low-cost monitoring at aquifer depth that can help reduce uncertainty and provides insights in thermal–hydraulic processes governing ATES performance. This multi‑sense DFOS approach enhances predictive modelling, enables early detection of thermal short‑circuiting or unintended flow pathways, and supports more efficient, reliable and sustainable ATES operation.