Rapid Open-Source-Based Simulation Approach for Coaxial Medium-Deep and Deep Borehole Heat Exchanger Systems

Dmitry Romanov (), Ingela Becker-Grupe, Amir M. Jodeiri, Marco Cozzini and Stefan Holler
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Dmitry Romanov: Faculty of Resource Management, HAWK Hildesheim/Holzminden/Göttingen University of Applied Sciences and Arts, Rudolf-Diesel-Straße 12, 37075 Göttingen, Germany
Ingela Becker-Grupe: Faculty of Resource Management, HAWK Hildesheim/Holzminden/Göttingen University of Applied Sciences and Arts, Rudolf-Diesel-Straße 12, 37075 Göttingen, Germany
Amir M. Jodeiri: EURAC Research, Institute for Renewable Energy, Viale Druso 1, 39100 Bolzano, Italy
Marco Cozzini: EURAC Research, Institute for Renewable Energy, Viale Druso 1, 39100 Bolzano, Italy
Stefan Holler: Faculty of Resource Management, HAWK Hildesheim/Holzminden/Göttingen University of Applied Sciences and Arts, Rudolf-Diesel-Straße 12, 37075 Göttingen, Germany

Energies, 2025, vol. 18, issue 18, 1-31

Abstract: Compared to shallow geothermal systems, coaxial medium-deep and deep borehole heat exchangers (MDBHE and DBHE) offer higher temperatures and heat extraction rates while requiring less surface area, making them attractive options for sustainable heat supply in combination with ground-source heat pumps (GSHP). However, existing simulation tools for such systems are often limited in computational efficiency or open-source availability. To address this gap, we propose a rapid modeling approach using the open-source Python package “pygfunction” (v2.3.0). Its workflow was adjusted to accept the fluid inlet temperature as input. The effective undisturbed ground temperature and ground thermophysical properties were weight-averaged considering stratified ground layers. Validation of the approach was conducted by comparing simulation results with 12 references, including established models and experimental data. The proposed method enables fast estimation of fluid temperatures and heat extraction rates for single boreholes and small-scale bore fields in both homogeneous and heterogeneous geological conditions at depths of 700–3000 m, thus supporting rapid assessments of the coefficient of performance (COP) of GSHP. The approach systematically underestimates fluid outlet temperatures by up to 2–3 °C, resulting in a maximum underestimation of COP of 4%. Under significant groundwater flow or extreme geothermal gradients, these errors may increase to 4 °C and 6%, respectively. Based on the available data, these discrepancies may result in errors in GSHP electric power estimation of approximately ±10%. The method offers practical value for GSHP performance evaluation, geothermal potential mapping, and district heating network planning, supporting geologists, engineers, planners, and decision-makers.

Keywords: deep geothermal energy; fast modeling; ground-source heat pumps; medium-deep geothermal energy; pygfunction (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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