This study examines the integration of coaxial borehole heat exchangers (CBHEs) into a hybrid renewable heating system for a school and swimming pool complex in northern Germany. Numerical simulations using COMSOL Multiphysics compared the thermal performance of CBHEs to conventional U-tube borehole heat exchangers (BHEs) and assessed the impact of borehole spacing (5 m vs. 10 m) on thermal interference and seasonal heat extraction over 20 years. Results show that 10 m spacing yields higher outlet temperatures and greater cumulative seasonal heat extraction compared to 5 m spacing. The CBHEs field outperformed U‑tube BHEs field.

Summer surplus heat from solar collectors and a wind-driven boiler is injected into the ground to recharge the field, offsetting winter cooling and improving extraction efficiency. Towards the end of winter, as heat demand declines, only a reduced number of peripheral probes are activated to match lower loads.

Economic analysis, based on the levelized cost of heat (LCOH), compared four configurations (5 m and 10 m spacing, each paired with wind or solar energy) at discount rates of 5% and 7%. The 10 m CBHE system coupled with wind energy achieved the lowest LCOH and fastest payback within approximately nine years, outperforming both the 5 m wind-driven and all solar-driven scenarios.

The findings highlight a trade-off between wider spacing, which reduces thermal interference, and increased drilling costs. Overall, a 10 m-spaced CBHE field sector-coupled to wind power and supported by seasonal heat storage emerges as a technically robust and economically viable solution for institutional heating.

Deep borehole heat exchangers (DBHEs) are attractive due to their high heat extraction rates and low surface area requirements compared to shallow geothermal systems. Various numerical, analytical, and semi-analytical models exist for DBHE simulation, but many lack versatility or computational efficiency. The Python package “pygfunction,” commonly used for shallow geothermal borehole fields, enables evaluation of thermal response factors (g-functions) with minimal computational effort. However, its suitability for DBHE simulation has not been tested. Thus, this study investigates whether pygfunction adequately models deep coaxial BHEs and assesses the expected margin of error.

To simulate DBHEs, the undisturbed ground temperature and thermophysical properties were averaged along borehole depth in pygfunction. Model results were compared against numerical and semi-analytical simulations, as well as experimental literature data. Scenarios considered a range of depths (700–3000 m), target parameters, and configurations including multiple underground layers with distinct thermophysical properties. Results indicate that the current pygfunction version (2.3.0) does not accurately simulate the fluid temperature profile along the DBHE length, due to assumptions valid for shallow systems only. Nevertheless, pygfunction predicts fluid inlet and outlet temperatures and heat extraction rates of DBHEs reasonably well, with a mean underestimation error of approximately 10%.

Thus, pygfunction can offer computationally efficient and sufficiently accurate results for further ground-source heat pump modeling involving DBHEs. These findings are relevant for researchers and engineers in the field of deep and medium-deep geothermal energy, particularly where rapid computation and reasonable accuracy are required for preliminary design and analysis.

This focused workshop offers a structured and practical introduction to Artificial Intelligence (AI) in the geothermal sector. It begins with a broad introduction to AI, then progressively zooms in on company integration strategies and real-world geothermal use cases. With expert inputs from industry and academia, attendees will leave with a better understanding of how AI can enhance both daily operations and specialized geothermal tasks, from seismic interpretation to borehole optimization.

Since 2000, the Groß Schönebeck site has served as a multidisciplinary research platform, investigating the extraction of geothermal energy via a 4.4 km doublet well system. As part of the TRANSGEO project, a study was conducted to explore alternative geothermal development options at the site. The study considered the potential of utilising the existing infrastructure for electricity generation and heating purposes. Although the Rotliegend formation was identified as a potential geothermal reservoir with a temperature of ~150°C, it was found to be insufficiently permeable for commercial-level heat production. The study therefore implemented two new technological approaches: an open-system development scenario involving a fracture-dominated Enhanced Geothermal Systems (EGS) and a closed-system scenario involving a single-well coaxial Deep Borehole Heat Exchanger (DBHE) concepts. The fracture-dominated EGS concept is designed to extract heat from the Rotliegend Formation at a depth of 4.2 km, while the coaxial DBHE concept utilises the highly conductive salt layers of the Zechstein Formation at a depth of 3.8 km. A series of numerical simulations were conducted using the CMG STARS software to assess the optimal energy yield from each well. The study's results are complemented by a discussion of measures that could be implemented to increase these concept's feasibility, as well as an economic assessment of the investment required for the hypothetical development scenarios versus the potential revenue. The study provides a comprehensive overview of the procedural steps of the field development phase, in accordance with the local regulatory framework and with a particular focus on the two scenarios.

Geothermal energy plays an important role for Germany’s heating transition and decarbonization. Yet, the development of conventional hydrothermal systems is often constrained by geological limitations. Enhanced geothermal systems, particularly those employing multistage hydraulic stimulation, offer a transformative solution. Adapted from the oil and gas industry and already successfully demonstrated in the United States, this technology enables geothermal deployment in a wider range of geological settings, potentially unlocking substantial low-emission heating potential for Germany.

Despite these technical developments, public acceptance remains a significant barrier. Although geothermal hydraulic stimulation outside of water- and nature protection areas is legally permitted in Germany, widespread skepticism, driven by concerns over environmental risks, property damage due to induced seismicity, and incorrectly associate with shale gas fracking continues to delay projects. In contrast to the United States, where pilot projects have gained traction, Europe is lagging behind in implementation.

This student project at the Technical University of Munich explored how the social acceptance of both conventional and next-generation geothermal technologies can be improved. Performing interviews in the Munich area, we assessed public attitudes, identified key concerns, and developed targeted communication strategies. We also examined the effectiveness of creative content – such as videos, infographics, and social media, in addressing misinformation and fostering public dialogue.

By identifying the causes of skepticism and offering tailored informational materials, we aim to support the broader rollout of innovative geothermal technologies across Germany. Our findings are intended to help policymakers, project developers and communicators to better align technological innovation with societal readiness.