Orals: Mon, 28 Apr | Room -2.43
Thermal Response Tests (TRT) are conducted to determine the equivalent thermal conductivity and, in some cases, the volumetric heat capacity of the subsurface, which are essential for designing low-temperature geothermal systems. During TRTs, heated water is circulated through a ground heat exchanger (GHE), while the temperature variations at the borehole's inlet and outlet are monitored over time (Pasquier et al., 2016). Generally, TRT interpretation yields averaged thermal properties along the entire GHE, overlooking variations in geological materials that can affect heat transfer efficiency. Acquiring detailed thermal and hydraulic property data at varying depths allows for the optimization of GHE design to enhance overall performance. Furthermore, traditional TRTs primarily rely on water temperature measurements, providing limited information into the spatial distribution of temperature changes in the surrounding geological environment.
Geophysical methods, such as electrical resistivity monitoring, can provide complementary measurements using the sensitivity of electrical resistivity to temperature changes. In this study, we investigate the use of geoelectrical monitoring during TRTs to image temperature variations in the geological environment to improve the recovery of localized thermal properties. A geoelectrical cable is placed inside the borehole during the TRT, with an electric current injected through surface and borehole electrodes. Another set of surface and borehole electrodes measures the resulting potential differences. Varying electrode spacing allows to measure apparent resistivity changes at different radial distances from the borehole. This means that electrical measurements are sensitive to temperature changes at various depths in the geological environment and could image heat transfer during the TRT. We conducted two proof-of-concept studies on standing column wells (SCW) in Varennes and Saint-Anne-des-Plaines in Québec, Canada, to test electrical monitoring during a TRT. The SCWs were subjected to heating, bleeding and recovery phases, while time-lapse electrical measurements were taken using a geoelectrical cable installed in the SCWs.
Field data shows a strong correlation between apparent electrical resistivity and temperature variations during heating and recovery cycles. Geoelectrical data is compared with infinite and cylindrical line source models to simulate temperature-induced resistivity changes around the SCW. Preliminary results indicate varying sensitivity of apparent resistivity variations to SCW water temperatures, as well as to the subsurface's thermal conductivity and heat capacity. Building on these findings, the study aims to derive localized thermal parameters from the geoelectrical data. This approach highlights the potential of geophysical monitoring to enhance the accuracy of thermal characterization in TRTs.
Pasquier, P., Nguyen, A., Eppner, F., Marcotte, D., & Baudron, P. (2016). Standing column wells. Advances in Ground-Source Heat Pump Systems (pp. 269–294). Elsevier. http://dx.doi.org/10.1016/B978-0-08-100311-4.00010-8
How to cite: Szabo Som, C., Fabien-Ouellet, G., Pasquier, P., and Dimech, A.: Geophysical Electrical Monitoring of Thermal Response Tests for Complementary Thermal Property Estimation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11992, https://doi.org/10.5194/egusphere-egu25-11992, 2025.
Accurate simulation of the heat pump inlet fluid temperature is critical to the design of an optimal, high performance ground source heat pump system. The closed-loop ground heat exchanger must be able to meet the heating and cooling demands while maintaining the inlet temperature within specified design limits over multiple years. This simulation usually relies on the use of a transfer function. Traditional approaches, often based on Eskilson's g-function, typically neglect the short-term effects from borehole thermal capacities, as well as the aquifer's heterogeneity and advection from groundwater flow. Overlooking these physical processes can lead to sub-optimal borefield designs.
This study addresses this situation by presenting a combined model for the near-instant construction of short-term transfer functions at the borehole outlet for a single closed-loop borehole installed in a multi-layered aquifer under groundwater flow. The approach leverages a wavelet decomposition scheme as a pre-processing step to improve the prediction accuracy of the target functions, which are approximated using three different artificial neural networks. Once independently trained, these sub-networks are then combined to streamline the implementation of the model in a source code or a spreadsheet and to reduce computational costs. The database used to train and test the artificial neural networks is derived from a 3D finite element model that provides realistic and accurate simulations of the ground heat exchanger over a 7-day period. For each simulation, the borehole and pipe geometry, the circulation flow rate, the thermal properties of the borehole's components (e.g. pipe, grout, heat carrier fluid), as well as both the thermal and hydraulic properties of the five geological layers are sampled from uniform distributions using Halton set. The database covers a wide range of hydrogeological environments, borehole configurations, and operating conditions.
The combined model shows good agreement with the numerical model-based transfer functions, achieving an average relative root mean square error of 7.03×10-3 over 4371 independent simulations. Furthermore, prediction times are as low as 0.05 milliseconds, enabling efficient design. This advancement provides a robust and efficient tool for improving the simulation and design of ground source heat pump systems. The combined model can also be used to interpret thermal response tests within a Bayesian framework for any given hydrogeological setting.
How to cite: Rose, C., Pasquier, P., Nguyen, A., and Labib, R.: Near-instant prediction of short-term transfer functions for closed-loop boreholes in heterogeneous aquifers influenced by groundwater flow using wavelet decomposition and neural networks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1651, https://doi.org/10.5194/egusphere-egu25-1651, 2025.
The presence of underground infrastructure has been shown to affect subsurface temperatures beneath dense urban areas, in a phenomenon known as the subsurface urban heat island (SUHI). The increase in temperature can impact the subsurface in several ways, including groundwater quality and ecosystems, goods production and storage, and infrastructure maintenance. Importantly, and most relevant to this work, this phenomenon can have considerable impact on the shallow geothermal potential of the ground under cities, and accounting for this is an important aspect of estimating and planning the comprehensive provision of heating and cooling using the ground.
A barrier to the accurate assessment of city-scale shallow geothermal potential is scarcity of data on ground conditions, within both the natural and the built environment. The cost to acquire these subsurface data is prohibitively high, and uncertainties in the parameter values to use in numerical modelling remain, giving rise to propagated uncertainty in the results calculated for the potential, which is seldom accounted for. Quantifying the uncertainty in the determined geothermal potential given uncertain input parameters is an important step towards establishing meaningful potential estimates as well as understanding which parameters require more and/or more precise data measurements.
In a step towards this, this work builds on a previously published methodology for large-scale thermal and geothermal potential mapping, based on the identification of ground thermal archetypes. The methodology is expanded through the propagation of sources of input uncertainty, such as ground thermal parameters and temperature of subsurface infrastructure, to determine the variability in the ground temperature and, by extension, the large-scale geothermal potential within two boroughs of London, United Kingdom. Critical parameters are identified via an archetype-level sensitivity analysis and surrogate models are generated for each of the archetypes identified within the modelled domain. Uncertainty in the input parameters is propagated through to the volume-averaged temperature, using Monte Carlo simulations. The results show the effect of uncertainty from individual inputs as well as combined effects from multiple sources of uncertainty, contributing to an improved understanding of the reliability of shallow geothermal for space heating and cooling.
How to cite: Kreitmair, M., Mak, N., Torrico Siacara, A., and Choudhary, R.: Impact of input uncertainty within large-scale shallow geothermal assessment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17494, https://doi.org/10.5194/egusphere-egu25-17494, 2025.
Energy geostructures (EGS) and shallow underground thermal energy storage (UTES) systems are receiving increasing attention from the research community and policymakers thanks to the appealing energy savings that can be achieved and the consequent reduction in energy expenditures and carbon emissions. However, no implementations of EGS with UTES exist in the Czech Republic, neither at the building nor at the district level. This partly stems from a lack of knowledge of the ground response to thermal loading but also from an insufficient understanding of the interaction with other renewable energy sources and the associated challenges. We present site description with its ground and air tempetarure long term trends for a proof-of-concept model demonstrating the feasibility of an implementation of UTES in the Czech Republic. Furthermore, we present detailed soil description, soil mechanical properties and an extensive experimental program conducted under controlled conditions on the selected natural soil – Březno formation marlstones from Dubičná, the Czech Republic – to investigate the influence of temperature on soil compression behaviour. The experimental programme is conducted in an advanced thermo-hydro-mechanical (THM) oedometer cell and involves a series of compression and creep oedometer tests with the range of investigated temperatures between 20 and 60°C. The influence of temperature on both compressibility and the rate of creep deformation will be quantified within the studied temperature range. The experimental data will provide essential input for calibrating advanced coupled THM viscohypoplastic constitutive models, which will be further used in the proof-of-concept model.
How to cite: Jerman, J., Najser, J., Libiš, J., Roháč, J., and Scaringi, G.: Natural soil thermal behaviour and site description for the underground thermal energy storage case study, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13308, https://doi.org/10.5194/egusphere-egu25-13308, 2025.
We present a techno-economic screening tool for modeling, analysis, and optimization of High Temperature Aquifer Thermal Energy Storage (HT-ATES) systems, specifically based on data from the Vienna Basin. A 3D ATES model with high fidelity is constructed using an open-source finite element code, OpenGeoSys, and the ATES parameters (e.g., material properties or geometries) are varied through a Design of Experiment workflow. The first stage of this statistical analysis is to identify significant factors, followed by the second stage to create a response surface model, which efficiently approximates HT-ATES system outputs on a reduced parameter domain. The entire process requires only open-source software including pre-and post-processors, and the workflow is scripted using Python. By eliminating reliance on commercial simulators, this tool facilitates ATES performance assessment, delivering results in mere seconds.
How to cite: Khasheei, M., Yoshioka, K., Kulich, J., Scholey, R., and Götzl, G.: Development of an Open-Source Tool for Feasibility Assessment of Aquifer Thermal Energy Storage (FATES) based on Design of Experiment (DoE), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4955, https://doi.org/10.5194/egusphere-egu25-4955, 2025.
Geothermal applications, like other Solid Earth studies, suffer from different sources of uncertainty. These may arise, among others, from structural variations, and material properties. Joint considerations of these different sources are challenging since taking structural changes for process simulations into account requires a mesh for the given structural configuration. For the geological model generation, either implicit or explicit techniques are available. Implicit models would allow for an easy adaptation of the structural features but pose challenges in constructing water-tight unstructured meshes, as required for the process simulations. For explicit approaches, already the initial mesh construction is a labor-intensive procedure, potentially generating a couple of hundred thousand to millions of meshes, which are needed for probabilistic analyses, exceeds the typically available resources. Furthermore, fully automatized meshing procedures for complex explicit subsurface models remain an open challenge. In this contribution, we present methods from the field of computer vision, such as subdivision surfaces, to leverage some of these issues.
However, we face another computational challenge: Even if we are able to generate the desired amount of meshes, this does not address the computational burden of the process simulations themselves. Even for simple physical principles, large-scale geothermal models easily require a couple of hours per simulation using state-of-the-art solvers and high-performance computing infrastructures. This makes a probabilistic consideration unfeasible. Therefore, we illustrate in this study the construction of reliable and physically consistent surrogate models via physics-based machine learning methods that capture both the impact of structural variations and material properties on both conductive and convective temperature distributions. The obtained surrogate models typically reduced the computation time for a single simulation to a couple of milliseconds, reducing the computational burden by several orders of magnitude. Nonetheless, we require about a hundred simulations for the construction of the surrogate models. This entails the generation of a hundred meshes and the execution of a hundred simulations. However, this computational cost is significantly lower than the cost for the later analyses. Furthermore, the surrogate generates a continuous representation for the geometry. Consequently, we can represent, for instance, interface positions or dip angles for the fault for which no mesh has been generated, as long as the values are within the pre-defined training ranges.
We want to highlight, especially the convective aspect of the study since most approaches that have been presented so far are applicable to linear problems only. Hence, the transferability of these approaches to nonlinear hyperbolic partial differential equations, as required for hydrothermal studies, is a major challenge. By using the here proposed methodology this challenge is overcome and demonstrates great potential for future applications.
How to cite: Degen, D., Cacace, M., and Wellmann, F.: Joint Investigations of Structural and Process Related Variabilities using Physics-Based Machine Learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8340, https://doi.org/10.5194/egusphere-egu25-8340, 2025.
While geothermal systems already contribute as low-emission energy sources, a drastic increase in its production is required to meet net-zero targets towards mid-century. For further geothermal energy production growth, supercritical geothermal systems are expected to play a major role as high enthalpy under supercritical conditions can scale up energy generation in one order of magnitude. Despite their potential, the development and characteristics of supercritical reservoirs are little understood. This study provides new insights on the three-dimensional evolution of supercritical conditions and their dependence on factors like magmatic intrusion shape and stage through numerical simulations. Simulation results show that during the early phases of intrusion, upward convection leads to the formation of zones surrounding the intrusion, while cooler fluids dominate the upper central areas. Intermittent supercritical reservoirs, characterized by dynamic convective processes, may form near the surface (around 1 km depth) with lifespans of 200 to 300 years. The findings highlight the importance of targeting exploration efforts on areas surrounding magmatic intrusions. These regions are essential for understanding reservoir dynamics, recognizing dominant convection patterns, and locating zones with the highest energy potential.
How to cite: Criollo, R., Vilarrasa, V., and Yoshioka, K.: Dynamics of Supercritical Geothermal Systems for Next-Generation Energy Solutions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12936, https://doi.org/10.5194/egusphere-egu25-12936, 2025.
The Vendenheim geothermal project, located at the north of Strasbourg France, in the Upper Rhine Graben, was halted due to the occurrence of two clusters of induced seismic events. One of these clusters is located far from the wells (4-5 km). Therefore, in the framework of the DT-GEO project (Horizon Europe), we developed a 3D thermo-hydro-mechanical (THM) model to have a better idea of the natural convective hydro-thermal conditions of this reservoir and to propose possible mechanisms that triggered these events. The geometry of this model was obtained from the GEORG platform, including the main geological units and faults. The geological properties and initial/boundary conditions were obtained from nearby reservoirs (such as Soultz-sous-Forets), which are also located in the Upper Rhine Graben. The hydro-thermal-mechanical equations were solved using the open-source finite element code MOOSE/GOLEM. We present here the results of our modelling, which focuses on the hydrothermal circulation in the reservoir area, like temperature and heat flux profiles, and the analysis of fault stability. We therefore propose a model that explains the natural conditions at the site and can serve as the initial conditions that existed prior to injection. In addition, as a perspective, our study can be used to understand the mechanisms that caused the induced events.
How to cite: Abreu Torres, J., Schmittbuhl, J., Cacace, M., Blöcher, G., and Hutka, G.: Long range modelization of the natural hydrothermal convection in the Vendenheim geothermal site., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16638, https://doi.org/10.5194/egusphere-egu25-16638, 2025.
The GeoLaB infrastructure currently in planning stages will be the first underground research laboratory (URL) for investigating the sustainable und safe use of deep geothermal energy in Germany. The Odenwald is currently being investigated as a potential candidate for the GeoLaB. To support researchers from multiple research centres in Germany, a digital infrastructure has been developed for a digital twin of the laboratory. A 3D visualisation of the surrounding area has been modelled, containing geographical, hydrological, geological, and administrative data. On the surface, this gives an overview of settlements, protection areas, land use and much more. In addition, the subsurface includes detailed information on geological layers and existing boreholes. Currently seismic and hydrological campaigns are conducted in the area and test drillings are being performed. All the available data from these campaigns will be added into the visualisation framework along with the layout of a potential tunnel system. This system serves to support the planning stage of the project and provide information for knowledge transfer activities for stakeholders and the public. The visualisation is interactive and users can explore the integrated datasets. Supplemental information such as websites, videos, or documents can be linked to specific structures to provide additional information. Already set up data loggers and sensors are being shown and measured data can be accessed by simply clicking the respective 3D representation.
To allow this kind of real time data access and interaction, a complex data management system has been set up for storing a large collection of heterogeneous data related to the location, the infrastructure, measurement campaigns, experiments, and any other data within the context of GeoLaB. It contains not only geoscientific data that is feeding the digital twin of the laboratory, but also documentation, public relations material, publications and much more.
Over time, with more data being gathered and measured this system will be gradually expanded. The functionality to integrate the results of numerical simulations has already been implemented into the framework. This allows to compare observed and simulated data for more reliable insights into complex hydro-thermal-mechanical and chemical processes within the host rock and will provide a large benefit during both the planning and the productive stage, when research experiments within the tunnel system are being set up. For now, this visualisation and the data management framework provide an interactive overview of all the available project-related data in a unified context and give a descriptive and intuitive presentation of the site and ongoing activities. In the future, the system will be expanded into a full digital twin of the site to explore and check many aspects of the ongoing research activities within GeoLaB. We will also briefly present the GeoDT project, which is specifically dedicated to the data and model integration of the Odenwald site.
How to cite: Kolditz, O., Goldstein, S., Jahn, M., Steinhülb, J., Kohl, T., Sass, I., and Rink, K.: GeoLaB: A digital infrastructure for a geothermal laboratory, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8368, https://doi.org/10.5194/egusphere-egu25-8368, 2025.
With the demand for sustainable and energy-efficient heating and cooling systems increasing, Ground Source Heat Pump (GSHP) systems have emerged as a promising alternative to conventional Air Source Heat Pump (ASHP) systems. Unlike standalone GSHP systems, shared-loop configurations optimize ground heat exchanger (GHE) usage by balancing heating and cooling demands across multiple users, thereby improving overall system efficiency. The current study investigates the environmental advantages of using a shared-loop GSHP system, compared to ASHP systems, through a Life Cycle Analysis (LCA) approach in terms of CO2-equivalent emissions. The LCA analysis considers different climate zones and the sizing of the shared boreholes is estimated based on peak shaving and the available surface area. The environmental evaluation is conducted using the openLCA software and ReCiPe as the impact assessment method, with the implementation of the Ecoinvent database. The obtained results demonstrate that shared-loop GSHP systems offer lower emissions over conventional systems, particularly in scenarios with high heating demands and in regions with moderate to extreme climates. Additionally, the systems are highly dependent on the electricity mix of the area, as in the case of stand-alone GSHP systems. While both systems contribute toward the renewable energy transition, wider benefits should be considered under a range of conditions.
How to cite: Aresti, L., Panayiotou, G., Georgiou, G., Ciapala, B., and Christodoulides, P.: Environmental benefits with shared-loop ground source heat pump systems compared to Air source heat pumps systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10802, https://doi.org/10.5194/egusphere-egu25-10802, 2025.
The increasing adoption of Ground Source Heat Pump (GSHP) systems in modern energy infrastructures in urban areas, particularly within the 5th generation district heating and cooling (5GDHC) networks, highlights the need for advanced computational tools to enable efficient evaluation and optimization. Addressing this need, this study presents an integrative simulation tool that combines detailed heat pump and ground heat exchanger models. This computational tool incorporates a data-driven parameter optimization process, enhancing the model's ability to accurately represent real-world dynamics.
The computational framework couples a thermodynamically detailed heat pump model with a subsurface heat transfer model to capture the complex thermal interactions between the heat pump and the ground heat exchangers. Heat exchange processes, including Borehole Heat Exchanger (BHE) inlet/outlet temperatures and ground thermal behavior, are simulated in detail considering site-specific conditions. Python programming serves as the integration platform, ensuring seamless data exchange and synchronized simulation between the models while enabling efficient parameter calibration and optimization.
The developed tool is applied to evaluate the thermal performance of designed BHE sites under realistic operational scenarios, utilizing high-resolution time series of heating and cooling loads. Key performance metrics, such as seasonal coefficient of performance (SCOP), ground thermal regeneration, and overall system efficiency and sustainability, are analyzed to provide actionable insights into system performance. This work can complement existing initiatives like the Wärmegut project, contributing to the broader effort of advancing shallow geothermal energy technologies and their integration into optimized energy systems.
How to cite: Liu, Q., Meneses Riosecoa, E., Huang, M., and Moeck, I.: Performance Assessment of Ground Source Heat Pump Systems Using a Co-Simulation Tool Integrating Heat Pump and Ground Heat Exchanger Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17701, https://doi.org/10.5194/egusphere-egu25-17701, 2025.
As global efforts toward energy sustainability increase, Ground Source Heat Pump (GSHP) systems have gathered significant attention as a renewable solution for space heating and cooling. The current study focuses on the initial performance investigation of shared-loop GSHP systems in the climatic condition of Cyprus, a Mediterranean island characterized by mild winters and hot summers. Shared-loop configurations, which connect multiple buildings or units to a common ground heat exchanger (GHE), are particularly promising for an urban environment, such as dense populated or space-constrained areas, offering the potential for enhancing efficiency and reducing the initial investment. The shared-loop configuration offers advantages in terms of the reduced infrastructure required and the related costs, with the aim to improve utilization of ground resources. This study investigates theoretical cases, and evaluates the operational performance of shared-loop GSHP systems. The study employs numerical modeling tools, such as TRNSYS, to estimate the heating loads of the users, as well as to assess the system’s capacity. Borehole sizing and ground thermal characteristic, are estimated based on the selected location and from previous experimental data. Preliminary results indicate that shared-loop GSHP systems can achieve a high system efficiency, however concerns are raised related to effectively balancing the thermal loads among users. Additionally, the ability of shared-loop systems to adapt to varying building and climate conditions makes them a flexible and future-proof solution.
How to cite: Christodoulides, P., Panayiotou, G., Filippou, C., and Aresti, L.: Initial performance investigation of shared-loops ground source heat pump systems in the Mediterranean island of Cyprus, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10678, https://doi.org/10.5194/egusphere-egu25-10678, 2025.
Temperatures in the shallow urban subsurface are typically elevated. Locally, e.g. near underground car parks or other underground infrastructures, they may be ≥5 K warmer than background temperatures. Often these temperature anomalies are discussed as a heat source for shallow geothermal heat recycling. This could significantly lower local temperatures. Here we investigate the short-term impacts of underground temperature anomalies in the soil on atmospheric energy fluxes in Berlin after two days using the large eddy simulation (LES) microclimate model PALM-4U. Two scenarios are compared: a reference case and one where temperatures at 3 m depth are increased by 5 K.
We find pronounced changes in sensible heat flux (SHF), ground heat flux (GHF), surface temperature and 2 m potential temperature. Even after the very short time period of two days a maximum increase of 0.64 K in 2 m potential temperature is simulated. With increasing height, the influencing effect diminishes. These findings demonstrate that soil temperature anomalies significantly alter the temperature distribution and energy budget within urban systems.
Why are these findings important? In urban environments like Berlin, changes in soil heat fluxes can exacerbate urban warming, emphasizing their importance for urban heat island (UHI) dynamics and related societal challenges. Hence, the understanding of the soil-land-atmosphere coupling is of utmost importance not only regarding energy flux dynamics but even more for shallow geothermal energy applications and its effects on urban microclimates, particularly for urban heat mitigation. Subsurface heat recycling and alleviating underground thermal pollution have been disregarded so far. However, subsurface heat recycling can provide a green, renewable, and carbon free energy solution for heating or cooling demands, when the technical feasibility of the geothermal potential is given. We demonstrate that soil temperature anomalies significantly influence the temperature distribution and energy budget of a system. Thus, in a reverse sense the potential of cooling the subsurface through shallow geothermal systems can be a sustainable method for creating climate resilient cities.
How to cite: Glocke, P., Holst, C. C., Dohmwirth, V., and Benz, S. A.: Unveiling the impact of shallow geothermal heat recycling and underground heat sources on urban heat fluxes and climate resilience, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14785, https://doi.org/10.5194/egusphere-egu25-14785, 2025.
Groundwater heat pump (GWHP) systems have recently gained attention as renewable energy sources, recognized for their high efficiency and potential for energy savings. Despite their potential, there are many considerations in design and operation due to the direct use of groundwater. Long-term operational data are crucial for accurate system analysis and control, but studies utilizing such data remain limited. Furthermore, the consideration of external social factors such as COVID-19, leading significant lifestyle changes, in relation to the energy consumption patterns of GWHP systems has been rarely reported. In this study, long-term operational data were collected at 1-hour intervals from a GWHP system in a university library in South Korea, spanning September 2017 to December 2023. The dataset covers periods before, during, and after COVID-19, enabling an analysis of heating and cooling patterns and their thermal impacts on groundwater. Results revealed significant reductions in energy consumption and thermal impacts on groundwater during strict COVID-19 restrictions. These findings can contribute to the efficient design and operation of GWHP systems and provide a comparative case study on conditions before and after the epidemic restrictions.
Key words: Groundwater heat pump system, Long-term operational data, Heating and cooling load, Groundwater impact
Acknowledgement: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2022R1A2C1006696).
How to cite: Oh, H.-R., Baek, J.-Y., Ha, S.-W., An, K.-M., and Lee, K.-K.: Analysis of 6-Year Operational Data from a Groundwater Heat Pump System in a University Library in South Korea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5393, https://doi.org/10.5194/egusphere-egu25-5393, 2025.
Shallow Geothermal Energy (SGE) systems, a form of Renewable Energy Systems (RES), integrate Ground Source Heat Pumps (GSHPs) for sustainable heating and cooling in buildings. These systems rely on Ground Heat Exchangers (GHEs) to facilitate thermal energy transfer between the building and the ground. Despite their higher performance and environmental benefits compared to conventional systems, GSHPs have seen limited adoption due to substantial upfront costs and extended payback periods. To address these challenges, the current study explores the application and implementation of different foundation elements to act as Energy Geo-Structures (EGs) by utilizing foundation slabs and retaining walls within underground parking spaces as GHEs. Computational modeling was conducted using the COMSOL Multiphysics software, with a focus on a residential building in Cyprus designed to meet nearly Zero Energy Building (nZEB) standards. The heating and cooling demands were assessed using TRNSYS software and integrated into the analysis of the proposed system. Results demonstrated that not all EGs systems achieved steady thermal performance and high Coefficient of Performance (COP) values. This study underscores the potential of partial loading and of integrating these foundation elements as GHEs, positioning them as a viable and sustainable alternative for residential energy systems.
How to cite: Florides, G., Aresti, L., and Christodoulides, P.: Comparison between different foundation elements as an Energy Geo-Structure in a Moderate Climate, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18579, https://doi.org/10.5194/egusphere-egu25-18579, 2025.
This study investigates the interaction between groundwater extraction and Aquifer Thermal Energy Storage (ATES) systems, aiming to optimize subsurface resource use sustainably. As demands on the subsurface grow, energy storage and groundwater extraction conflicts could impact efficiency, safety, and environmental quality [1]. Using a synthetic model based on the Grobbendonk extraction zone in Belgium, the research simulates groundwater flow and heat transport, focusing on the impact of varying distances between ATES and groundwater wells. The results reveal that proximity affects both groundwater temperature and ATES thermal recovery efficiency, with efficiency ranging from 35% at the closest distance (120 m) to 80% at the farthest (1900 m). Despite some temperature changes at close proximity, the findings open discussions about the potential co-location of ATES systems and groundwater extraction activities. This approach could expand the applicability of ATES closer to groundwater extraction wells while maintaining water quality and thermal efficiency.
We discuss the impact of the research results on policy and different management scenarios in Belgium.
References
[1] Deleersnyder, W., Tas, L., Szwoch, D., & Hermans, T. (2024, November). Exploring Interactions between Groundwater Extraction and Shallow Geothermal Energy to Use the Subsurface Optimally and Sustainably. In Fifth EAGE Global Energy Transition Conference & Exhibition (GET 2024) (Vol. 2024, No. 1, pp. 1-4). European Association of Geoscientists & Engineers.
How to cite: Deleersnyder, W., Tas, L., and Hermans, T.: Aquifer Thermal Energy Storage within a groundwater protection area: Possible interactions between competing subsurface activities, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7341, https://doi.org/10.5194/egusphere-egu25-7341, 2025.
The shallow geothermal resources are used worldwide to produce thermal energy in support of the decarbonization process. To fully exploit geothermal resources on a national scale, appropriate tools need to be developed, such as mapping of ground thermal properties, which enables identification of the shallow geothermal potential of large areas. Using the ISPRA (Italian Institute for Environmental Protection and Research) public database, we classified more than 28000 Italian perforation sites resulting from hydrological research studies, surveys, or civil engineering works. The ISPRA database provides generic and non-uniform lithological descriptions for each site. The lithological descriptions have been harmonized to obtain 28 classes that summarize the lithological variation in Italian shallow underground soils. Geological maps, additional well data, and further geological information have been used to interpret those lithological descriptions that were unclear or not fully-explained. Based on the lithological classification, we estimated the vertical trend of thermal conductivity within the perforation sites and the related geothermal potential concerning closed-loop geothermal probes. The obtained trends have been used to compute the mean thermal conductivity of the subsurface at shallow depth and the mean geothermal potential. We finally produced online-available national-scale maps that can be used to highlight the shallow geothermal potential of specific regions and to identify areas in the Italian territory that might be suitable for low enthalpy geothermal purposes.
How to cite: Squarzoni, G., Colucci, F., and Bernardo, N.: Shallow geothermal properties maps of the Italian underground soil: a lithological approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10574, https://doi.org/10.5194/egusphere-egu25-10574, 2025.
Shallow geothermal energy is one of the renewable energy sources that, when properly utilized, has a minimal impact on the environment. The relatively high investment cost of installing the system can be reduced if the local natural conditions are well defined. Knowledge of local soil properties and understanding of heat transfer in the natural environment are essential. One way to evaluate thermal properties is to perform the thermal response test (TRT). The main advantage of the method is that it provides the actual average thermal conductivity in the vicinity of the well, taking into account local hydrogeological factors and physical properties of the rock. The thermal conductivity determined in this way may differ significantly from laboratory or field measurements because they do not take into account all the factors that affect thermal conductivity in the subsurface.
The study presents the estimation of the thermal parameters of the subsurface using the results of the thermal response test carried out for the purpose of designing the geothermal system for heat storage (eastern part of central Slovenia).
In one of the borehole heat exchangers (BHE), we performed the TRT, which formed the basis for the calibration of the numerical model. First, we created a static numerical model, based on the average annual data of subsurface temperature, heat flow, thermal conductivity, and volumetric heat capacity of the subsurface. Further, we created a transient numerical model in which we included one-minute data of the BHE inlet temperature and flow rate, which were used to calibrate the thermal conductivity and volumetric heat capacity of the subsurface. In the next step, we will validate the numerical model with the operating data of the BHE field to determine the efficiency of the borehole thermal energy storage.
How to cite: Adrinek, S. and Janža, M.: Numerical calibration of rock thermal parameters based on thermal response test data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17119, https://doi.org/10.5194/egusphere-egu25-17119, 2025.
The use of renewable energies as an integration in multivalent district heating and cooling networks
(DHC) has been growing in recent years and a few systems are already operative across Europe.
A proper design is of paramount importance to guarantee the energy performance of the system. This work deals with the optimization of the technical and geometrical characteristics of borehole heat exchangers (BHE) in a well-defined hydrogeological context, aimed at the integrating the space heating and cooling of buildings. The test site is NW Italy where a gas-fired DH grid is currently operating. Three different configurations were analysed by investigating their thermal performances according to available geological information that revealed an aquifer in the first 36 m, overlying a poorly permeable marly succession. Numerical simulations were used to validate the geological, hydrogeological, and thermo-physical models by back-analysing the experimental results of a Thermal Response Test (TRT) on a pilot 150 m deep BHE. Five-years simulations were then performed to compare 150-m and 36-m polyethylene 2U, and 36-m steel coaxial BHEs. Results show higher thermal power extractions in the shallower 2U BHE (56.03 W/m) compared to the deeper one (42.47 W/m), probably due to presence of the aquifer which surely plays an important role in increasing the thermal power. The coaxial configuration shows the best performance both in terms of specific power (74.51 W/m) and borehole thermal resistance (0.02 mK/W). Outcomes of the study confirm that finding the best coupling between the geological framework and technical requirements, ensure the best energy performance and economic sustainability.
How to cite: Giordano, N., Chicco, J. M., and Mandrone, G.: The role of acquifer characteristics in the thermal performance of different borehole heat exchanger configurations: a case study in NW Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19305, https://doi.org/10.5194/egusphere-egu25-19305, 2025.
Climate change has a significant negative impact on water resources in the catchment area of Lake Velence, Hungary, which is a source of increasing conflicts amoung stakeholders and various water users. The area of the lake is an ecologically diverse, partly a Ramsar site, and consecutively, a dynamically developing, economically expanding area with rapid population growth, of which wetlands are a prominent, central element. As a result of significantly increasing new residents and newly built modern properties, the area has a high solar panel capacity, and thus the renewable energy production rate per property is outstanding at a national level. The negative impacts of climate change on water resources can be compensated by replenishing water resources from outside of the catchment area. The hilly nature of the area and the high solar panel supply serve as advantages if combined with pumped hydro-storage reservoirs.
The aim of the research is to develop a possible inter-basin water replenishment system based on the territorial characteristics, while fulfilling the economic-social-environmental needs. The water replenishment system considers the ecological aspects, the hilly characteristics of the area and the solar panel capacities of nearby settlements, as pumped water reservoirs are developed that balance the daytime peaks of renewable energy production. At the same time, the reservoirs are suitable for replenishing the water resources of Lake Velence from external watersheds, in a sustainable way with low carbon footprint. Using the excess water volumes above the ecological water demand of the watercourses available in the external, neighboring watershed, and the existing solar panel capacities of the nearby settlements, we optimize a sustainable renewable energy storage and water replenishment system that meets social, economic and environmental needs of the area.
How to cite: Kalman, A., Chappon, M., and Bene, K.: Combining interbasin water replenishment and solar capacities for sustainable energy and water management in the catchment of Lake Velence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19915, https://doi.org/10.5194/egusphere-egu25-19915, 2025.
It is essential to secure large-capacity ultra-long cycle ESS technology suitable for the facility capacity level of large wind and solar power plants in order to effectively respond to Korea's national agenda of spreading the supply of new and renewable energy for the transition to a carbon-neutral society.
This research team developed a large-capacity long-period energy storage device called "blue battery" using seawater. Blue battery is an ESS technology that stores renewable energy by separating salt in seawater into cations (e.g., Na+) and anions (Cl-). When the salt of seawater is ion-separated, the catholyte becomes a basic solution with a pH of 10-11, and the anolyte becomes an acidic solution with a pH of 3-4. When energy is stored with an acid-base, the theoretical energy storage density is about 10 Wh/L (57.6 kJ/mol), which is relatively low compared to the existing energy storage technology. This research team started the evaluation of the original technology performance of the blue battery on a '2×2 cm2' laboratory scale and succeeded in commissioning a 1 kW/10 kWh blue battery pilot system for the first time in Korea. The 10 kW blue battery system was designed for the purpose of controlling the variability of sunlight, which is pointed out as the main cause of Jeju's renewable energy output control, and the enterprise management system was designed by assuming that it accommodates the expected excess power (1 kW, up to 30% of the power generated) generated from 3 kW solar power generation (about 10 kW)
The economic feasibility of blue batteries was analyzed in two ways: the life cycle analysis of blue batteries themselves and the analysis of carbon reduction when using blue batteries.
First, the economic feasibility of the battery itself was analyzed. As a representative electrochemical long-term energy storage technology, there is a vanadium redox flow battery (VRFB). As a result of conducting the life cycle economic analysis (LCA) of VRFB and blue batteries, it was analyzed that the LCOS of VRFB was 6.05 euros/kWh, while the blue battery was 3.07 euros/kWh, which was nearly 50% cheaper.
Second, the economic feasibility and carbon emission reduction effects were analyzed when solar power generation and blue batteries were introduced into the electricity supply structure of this Jeju farm. The higher the power unit price and the higher the CF, the higher the economic feasibility of installing blue batteries. It can be seen that the introduction of blue batteries significantly increases the effect of reducing carbon emissions by utilizing surplus power. In particular, when solar power generation facilities and blue batteries are installed together, they not only secure power supply safety by compensating for the shortcomings of solar power generation, which is greatly affected by the amount of sunlight, but also significantly reduce carbon costs, indicating economic advantages in the long run.
Blue battery technology using seawater has long-term advantages even when analyzing economic feasibility, is an eco-friendly energy storage technology that does not emit environmental pollutants during energy storage (charging) and power generation (discharging).
How to cite: Cho, H.: Development and Economic Analysis of Blue Batteries Using Seawater, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4986, https://doi.org/10.5194/egusphere-egu25-4986, 2025.
Geothermal heat is an almost emission-free energy source, and it has become an important replacement for fossil fuels used to heat buildings. A promising geothermal system is the Coaxial Borehole Heat Exchanger (CBHE). It is a tube-in-tube system, where the “cold” fluid is injected into the annulus of the coaxial. The fluid becomes heated from the surrounding rocks on its way down the well, and the “hot” fluid returns to the surface through the inner tube. Here, we present numerical methods for deep coaxial borehole heat exchangers using compressible working fluids, such as supercritical CO2.
Pressure and the temperature in compressible fluids become coupled. A usual numerical approach is to decouple the temperature- and the pressure equations, where these equations are solved separately. We compare a fully coupled numerical scheme with three different schemes of decoupled pressure and temperature. These four schemes are (1) fully coupled and implicit temperature and pressure; (2) serially coupled implicit temperature and explicit pressure; and (3) serially coupled explicit temperature and pressure. These finite-difference schemes were tested using Ramey’s approximation of the heat flow from the rock. The final scheme was: (4) the coupling of a 1-dimensional pipe simulator with a transient temperature equation for the well bore and the transient conductive cooling of the rock.
Benchmarking of the numerical schemes was done by comparing their results. Schemes (1), (2) and (4) were in excellent agreement. The serially coupled explicit scheme (3) could produce useful results, considering its simplicity and speed and the uncertainties associated with rock properties. The testing of the schemes was done assuming a constant flow rate and quasi-stationary state of the fluid in the well.
For a constant mass flow rate, scheme (2) is recommended. Scheme (4) showed that just a few residence times were enough to establish a quasi-stationary state in the fluid. The CO2 test cases demonstrated the thermosiphon effect, and also showed how the temperature increased with increasing pressure — an effect directly related to the thermal expansibility of the fluid.
Reference:
M. Wangen, Numerical solutions for coaxial borehole heat exchangers using CO2 as a working fluid, Applied Thermal Engineering, 264 (2025) 125295, DOI: doi.org/10.1016/j.applthermaleng.2024.125295
How to cite: Wangen, M.: Numerical simulation of Coaxial Borehole Heat exchangers using supercritical CO2 as a working fluid, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13750, https://doi.org/10.5194/egusphere-egu25-13750, 2025.
Our study aims to demonstrate the control of fracture aperture opening on the apparent normal stiffness of fractures during fluid injection, a key factor governing the hydro-mechanical behavior of impermeable rock formations containing highly permeable fractures. Using the Distinct Element Method (DEM) implemented in 3DEC, we simulate fluid injection into a 100 m planar fracture through a line source under constant overpressure. By systematically varying the assigned fracture normal stiffness, we perform a sensitivity analysis on how aperture changes affect the apparent stiffness. For theoretical validation, we adopt a semi-analytical approach, which includes two governing equations: one assuming a negligible aperture gradient and another without this assumption. Numerical results closely match these semi-analytical solutions. In the “soft” fracture regime, the apparent stiffness decreases over time, eventually falling below the nominal stiffness assigned at a small-scale as the aperture grows. Conversely, in the “rigid” regime—where the aperture gradient is negligible—this effect is not observed. These findings underscore the role of time-dependent aperture evolution in controlling fracture stiffness during fluid injection.
How to cite: Ahmadov, K., Schmittbuhl, J., and Candela, T.: Coupling between pressure and opening during fluid injection into a fracture—implication for fracture normal stiffness, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19074, https://doi.org/10.5194/egusphere-egu25-19074, 2025.
Geothermal energy in Poland is predominantly utilized for heating, with an increasing focus on recreational and therapeutic applications. The Malopolska region is particularly notable for its concentration of geothermal wells, characterized by high temperatures and low mineralization waters. These geothermal waters can reach temperatures of approximately 82°C, with total dissolved solids (TDS) below 3 g/dm³, primarily classified as SO4–Cl–Na–Ca and SO4–Cl–Ca–Na types.
Also important possibility of using geothermal resources is the closed-loop geothermal system technology, drilled into the Earth with a series of multilateral wellbores, which may contribute to the growing importance of the use of geothermal energy in Poland in the coming years.
People are increasingly paying attention to effective use of renewable sources of energy. Recent trends indicate a growing interest among customers in the potential of geothermal resources for energy transition as well as well-being applications, especially in cascade systems. This study examines tourist interest and rising interest in efficient use of geothermal water in centers within the Malopolska region for diverse purposes, confirming the area's substantial potential for further geothermal energy utilization.
How to cite: Wachowicz-Pyzik, A., Halaj, E., Pajak, L., Stefaniuk, M., Florek, R., and Nowak, M.: A new approach to geothermal resources uses in versatile purposes ‒ Case Study from S Poland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17642, https://doi.org/10.5194/egusphere-egu25-17642, 2025.
Repurposing oil and gas fields for geothermal energy has gained attention, with several global pilot projects and feasibility studies (Watson et al., 2020). The Wytch Farm oil field in southern England is a promising candidate for this transition. Studies (Singh et al., 2017; Gluyas et al., 2018; Watson et al., 2020) have highlighted its favorable infrastructure and geological characteristics for geothermal energy. With a significant decline in hydrocarbon output (water cut of ~90%), the economic viability of oil extraction has diminished, creating an opportunity for geothermal applications (Gluyas et al., 2018).
Wytch Farm’s primary Sherwood Sandstone reservoir, at 1585m depth, is targeted for low-enthalpy geothermal energy production. This transition could extend the field’s operational life and contribute to the UK’s decarbonization goals by providing renewable, low-carbon energy. Potential geothermal district heating markets include Poole, Weymouth, Dorchester, and possibly larger urban centers like Bournemouth, assuming efficient infrastructure minimizes heat loss.
Accurately evaluating geothermal potential is crucial for determining energy output, economic feasibility, and the design of heating systems or geothermal plants. This study quantifies potential energy output from Wytch Farm wells, providing a foundation for a detailed feasibility evaluation, while accounting for geological and operational uncertainties.
Though Wytch Farm has been identified as a potential geothermal resource, previous studies did not fully address temperature and depth estimates. Recorded temperatures of 65-67°C (Singh et al., 2017; Gluyas et al., 2018; Watson et al., 2020) were cited, but our preliminary analysis of corrected bottom-hole temperature (BHT) data from the Sherwood Sandstone suggests a temperature range of 75-98°C. This indicates that earlier studies may have underestimated the geothermal potential of the site. Elevated reservoir temperatures are also observed in offshore and certain onshore wells.
In conclusion, this study highlights the potential of repurposing Wytch Farm for geothermal energy production, providing a more accurate assessment of its geothermal capacity and identifying factors influencing heat retention. The initial findings support the feasibility of transforming the site into a renewable energy resource, aligning with the UK’s decarbonization goals, and demonstrating the role of legacy oil and gas fields in the sustainable energy transition.
References:
- Gluyas, J. G., et al. (2018). Keeping warm: a review of deep geothermal potential of the UK. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy.
- Singh, H., et al. (2017). Harnessing Geothermal Energy from Mature Onshore Oil Fields-The Wytch Farm Case Study. Work. Geotherm. Reserv. Eng.
- Watson, S. M., et al. (2020). Repurposing hydrocarbon wells for geothermal use in the UK: The onshore fields with the greatest potential. Energies.
How to cite: Abdelhafez, A., Brunt, R., and Hollis, C.: Assessment of the Geothermal Potential of the Wytch Farm Oil Field, UK, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13521, https://doi.org/10.5194/egusphere-egu25-13521, 2025.
Geothermal exploration conducted by the Geological Survey and Mining Management Agency (GSMMA) of Taiwan has estimated the region's geothermal potential to reach up to 40 gigawatts (GW). The national strategic plan aims for an installed capacity of approximately 3 to 6 GW by 2050. However, the potential for shallow geothermal energy is currently assessed at less than 1 GW. To achieve the ambitious target of 3 to 6 GW of geothermal capacity, Taiwan must prioritize the development of deep geothermal resources through the utilization of Enhanced Geothermal System (EGS) or Advanced Geothermal System (AGS) technologies. Taiwan’s geographical location within an arc-continent collision zone results in a high geothermal gradient, although significant land constraints present challenges. The geothermal reservoir beneath Taiwan is relatively small and limited by the availability of fractured spaces to store thermal water, a consequence of the region's compressed tectonic activity. Consequently, the deployment of EGS or AGS technologies is critical for the construction of large-scale geothermal power facilities, thereby facilitating the achievement of Taiwan’s geothermal energy goals. However, the AGS remains prohibitively expensive and lacks commercial applications globally. As such, EGS presents a more viable solution for the development of geothermal energy in Taiwan.
How to cite: Song, S.-R., Song, T.-R. (., and Lu, Y.-C.: EGS: A Solution for Taiwan Geothermal Energy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5288, https://doi.org/10.5194/egusphere-egu25-5288, 2025.
