This session is dedicated to Underground Thermal Energy Storage (UTES) technologies, their performance and engineering, and new insights into related heat transport processes in the subsurface. In particular, the focus is on Aquifer Thermal Energy Storage (ATES), Borehole Thermal Energy Storage (BTES), Mine Thermal Energy Storage (MTES) and related ground-based variants such as pit storage, cavern storage and artificial water-gravel storage basins. This session aims to overcome technical obstacles concerning the design and sustainable operation of TES. We want to improve our understanding of any UTES-related thermal, hydraulic and other environmental effects.
In a broader context, we invite contributions that explore ways to enhance the social acceptance of UTES and integrate various renewable energy sources, such as geothermal, solar, and waste heat, into UTES technologies. This session aims to provide an overview of current and future research in the field, encompassing any temporal or spatial scale. Accurate characterisation of subsurface flow and heat transport, based on observations of induced or natural variations in the thermal regime, is essential in both research and practice. We seek contributions that offer new insights into experimental design advances, reports from novel field observations, and demonstrations of sequential or coupled modelling concepts. Key focus areas include the seasonal and long-term development of thermal and mechanical conditions in aquifers, heat transfer across aquifer boundaries, and the role of groundwater and geothermal energy in UTES. These aspects are crucial for predicting the long-term performance of heat and cold storage and production, as well as for integration into urban planning and policy making. We also invite hydrogeological studies that use heat as a natural or anthropogenic tracer to enhance thermal response testing or improve our understanding of relevant transport processes in aquifers.
There is an enormous potential for geothermal energy to address the issues of energy security and greenhouse gas emissions. Much of this potential remains undeveloped, in part due to concerns about the interface of geothermal energy development with other subsurface uses. In the deep subsurface, geothermal energy targets may overlap with existing oil and gas developments or areas that could be used for carbon storage and sequestration or production of other resources, such as lithium or helium. In the shallow subsurface, geothermal energy developments may overlap with groundwater resources that are critical water supplies and/or have important environmental functions. There is also the potential for shallow geothermal energy developments to interact with other subsurface infrastructure. These interactions in both the deep and shallow subsurface are likely to be problematic under projections of geothermal energy potential that have not considered other subsurface uses. New approaches to subsurface management that consider energy security, reduction of greenhouse gas emissions and water security using a range of possible developments may provide a clearer vision to develop the world’s geothermal resources.
How to cite: Ferguson, G.: Balancing Geothermal Potential and Subsurface Challenges, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14599, https://doi.org/10.5194/egusphere-egu25-14599, 2025.
The large-scale thermal use of near-surface groundwater is often limited extent due to the far-reaching thermal impacts and the large number of potentially affected third-party rights. Silvestri et al. (2025) first described the principle of unidirectional ATES. Unlike conventional thermal groundwater usage, where the production well is positioned upstream in the groundwater flow and the injection well downstream, unidirectional ATES works in reverse (inversion of a classic open-loop system). This ensures that, with a balanced heating and cooling ratio and a well spacing adjusted to the local groundwater flow velocity, the heat plume generated in summer by cooling operation reaches the extraction well a season later. In winter, the increased groundwater temperature is used for heating purposes, increasing the efficiency of the heat pump system. The same effect vice versa applies to the cooling season.
Equally important is the significant reduction in thermal anomalies caused by this principle. The plume of cooled or heated water is recaptured by the production well located downstream, leading to lower thermal impact on groundwater. This makes large scale projects only feasible, as they clearly minimize thermal interference with third-party interests.
In this specific case, the Steiermärkische Krankenanstaltengesellschaft (KAGes) plans to cover a large portion of the thermal power for LKH Graz Süd hospital (currently partly derived from fossil fuels) using shallow geothermal energy. Due to the excellent hydraulic properties of the aquifer in the Graz area, the required thermal output of about 3.5 MW could be achieved with three pairs of wells. In a conventional system of this size, the thermally influenced front would extend over 3 km of length, making approval in the urban area of Graz impossible.
This work presents an innovative unidirectional ATES system adapted to the local groundwater conditions (hydraulic conductivity, aquifer thickness, groundwater gradient). The project site was hydrogeologically surveyed, characterized, and compared with publicly available data. After developing the hydrogeological conceptual model, a coupled flow and heat transport model was established to simulate the system's operation. First, the optimal distance between the extraction and injection wells was determined based on local groundwater conditions, followed by a sensitivity analysis investigating the system's efficiency in terms of heat recovery depending on the flow velocity and extraction rate.
The transition from the theoretical approach of Silvestri et al. (2025) to practical implementation presents several challenges. Due to the climatic conditions, the outdoor air temperature in Graz does not follow a cosine pattern as described by Silvestri et al. (2025). Therefore, a fully balanced heating and cooling ratio cannot be achieved, limiting the system's functionality. Additionally, the thermal anomaly shifts due to inhomogeneities in the aquifer's geometry and hydraulic properties. Nonetheless, the results of this study showed that the new unidirectional ATES approach can not only significantly reduce thermal impacts, even with an unbalanced heating and cooling ratio, but also increase the system's heat recovery efficiency.
Silvestri, V., Crosta, G., Previati, A., Frattini, P., & Bloemendal, M. (2025). Uni-directional ATES in high groundwater flow aquifers. Geothermics, 125, Article 103152. https://doi.org/10.1016/j.geothermics.2024.103152
How to cite: Petschacher, N. and Vasvári, V.: The first unidirectional ATES in Austria – from theory to practical implementation , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9502, https://doi.org/10.5194/egusphere-egu25-9502, 2025.
Wind curtailment is a particularly acute challenge to wind energy integration in China. Since wind energy is intermittent and unpredictable, and its generation may not coincide in time with usage demands, its large-scale inclusion will introduce adjustment difficulties to power grids or regional heating network and large-scale wind curtailment problems can also occur. The addition of energy storage to wind energy generation can be a key solution to this problem.
High temperature aquifer thermal energy storage (HT-ATES) is a cost-effective and suitable technology to store large amounts of energy, and has been increasingly used for heating of buildings. It has been demonstrated as an efficient and stable tool to buffer the seasonal imbalance and significantly contribute to reduce greenhouse gas emissions.
Here we proposed a novel coupling strategy to combine wind power with HT-ATES for regional heating. The excess wind energy is firstly transformed for boiling water, which is then injected into the medium-deep aquifer for storage. In Winter time, the stored water is thereby extracted for heating. Based upon this hybrid system, the objective of smooth heat delivery can be achieved, and the problem of the instability in wind energy generation is solved while waste is prevented.
To achieve a comprehensive analysis of the feasibility of the hybrid system and the estimation of its thermal performance, a surface-to-subsurface model is established via the integration between TRNSYS and OpenGeoSys(OGS) platform. TRNSYS is applied to simulate the conversion from wind energy to thermal energy, while OGS focuses on the modeling of hydro-thermal coupled transport in the subsurface. The coupling is achieved via the input/output data exchange. The integrated model provides new insight into the thermal recovery efficiency of the whole system and allows us to decipher the relative importance of the controlling parameters.
The results obtained from the model show that the 600 kW wind turbine and HT- ATES hybrid system can provide around 4 GWh of the energy capacity after the 10th cycle, and the thermal recovery factor can be achieved up to 80%, which indicates a techno-economical promising perspective for the wide replication of the hybrid system.
How to cite: Huang, Y. and Qiu, N.: Feasibility Assessment of a Hybrid System Combining the Wind Power and High-temperature Aquifer Thermal Storage for Regional Heating, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11226, https://doi.org/10.5194/egusphere-egu25-11226, 2025.
For a successful global energy transition more seasonal thermal energy storage (STES) and district heating and cooling systems are needed. Hence, the economic aspects of STES are essential during the decision-making phase of planning a district heating and cooling system. Until now, only few studies exist on the capital costs of STES and particular aquifer thermal energy storage systems (ATES). Hence, this study aims to identify and analyse the capital costs of 132 existing ATES systems in Europe. Our results show that surface and subsurface installations contribute to 45% and 55% of the total capital costs, respectively. Drilling costs only account for about 8% of total capital costs. The results also illustrate a decrease in capital costs per installed heating and cooling capacity with increasing capacity. Capital costs per installed capacity converge to about 300 €/kW after 2 MW of installed heating and cooling capacity. Hence, larger ATES systems should be favoured. Compared with other seasonal thermal energy storage (STES) systems, ATES systems have the lowest capital costs per storage volume (< 10 €/m3) and the lowest per stored energy (130 – 1630 €/MWh). Hence, if the hydrogeological conditions at a site are favourable for an ATES system, this system should be the preferred STES system. In particular, if cooling and heating are required in equal proportions.
How to cite: Herrmann, M., Fleuchaus, P., Godschalk, B., Verbiest, M., Sørensen, S. N., and Blum, P.: Aquifer thermal energy storage (ATES): How much do they cost?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15656, https://doi.org/10.5194/egusphere-egu25-15656, 2025.
Aquifer Thermal Energy Storage (ATES) systems deliver low-carbon heating and cooling to the built environment. ATES offers higher efficiency (higher coefficient of performance, COP) compared to other low carbon heating and cooling technologies, because it captures, stores and re-uses both heat and cool that would otherwise be wasted. ATES also offers long term sustainable operation when the system is balanced, so there is no net extraction of heat or cool from the aquifer.
We consider here the design of a large ATES system to supply heating and cooling to a site in London. The target aquifer is the heterogeneous London Chalk, a dual porosity system in which groundwater flow occurs primarily within fractured and/or karstified intervals. A small number of ATES and other open-loop geothermal systems currently operate in London. Most comprise a single doublet and supply only a small proportion of the site heating and/or cooling demand. The largest operating systems comprise four doublets and supply peak heating and cooling demand of order 2-3 MW.
The analysis reported here is novel for four reasons. First, we implemented a probabilistic method to assess the initial capacity of the system. The Monte-Carlo approach assigns input distributions for uncertain design parameters prior to detailed analysis, such as borehole flow rates, injection temperature, thermal recovery factor (and hence production temperature), heat pump COP, and heating and cooling periods. The approach produces a distribution of predicted values for peak and annual heating and cooling supply, that provide insight into the range of potential system capacity.
Second, for detailed analysis we implemented a controller in our groundwater numerical simulator that continually updates borehole flowrates to meet a predefined heating and cooling demand for a given period. The controller accounts for the heat pump contribution and the difference between the produced groundwater temperature and the target heating or cooling temperature. The controller manages changes in groundwater temperature observed during production, modifying the flow rate to meet the heating or cooling demand.
Third, we investigated a large system installed on a relatively small site (ca. 500 m x 400 m) with peak heating demand of order 14 MW. A key challenge for ATES in urban environments is to deliver the energy and power density (energy per unit area, and power per unit area) commensurate with demand. Finally, we tested the impact of heterogeneity in the Chalk aquifer, using realistic geological models informed by operational data and modelling of nearby ATES systems. Our results suggest that a large system on the site is feasible and could meet a substantial proportion (and in some cases, all) of the heating and cooling demand. The most significant limitation on system capacity is the potential for aquifer heterogeneity to create laterally spreading plumes that result in thermal breakthrough.
How to cite: Jackson, M., Jacquemyn, C., Chow, Z., Bahlali, M., and Firth, H.: Scoping analysis for a large Aquifer Thermal Energy Storage (ATES) system in the London Chalk aquifer, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18063, https://doi.org/10.5194/egusphere-egu25-18063, 2025.
The Chalk aquifer in London is a highly heterogeneous dual-porosity system, characterised by high-permeability features resulting from fracturing and/or karstification within a low-permeability matrix. These high-permeability zones can be truncated by faults or marl layers of low permeability. Boreholes in London frequently reveal a prominent high-permeability flow zone at the top of the Chalk. Despite this, many predictive models for shallow geothermal systems in the region treat the aquifer as homogeneous, potentially leading to significant overestimations of heating and cooling delivery.
This study evaluates the influence of aquifer heterogeneity on the performance of Aquifer Thermal Energy Storage (ATES) systems through a model calibrated with data from an operational ATES installation in London. The system consists of four borehole doublets. Initial analysis indicates a well-balanced energy ratio of 0.09 and thermal recovery rates of approximately 40% for warm wells and 25% for cold wells. This presentation focuses on the four-step history-matching methodology employed in the study.
In Step 1, quality control was applied to the observed data, including lithological and flow logs, hydraulic head and flow rate data from borehole commissioning tests, and hourly flow rate and temperature measurements spanning five years of operation. Quality control was challenging due to the operational configuration, in which boreholes function as independent doublets, alternating between primary doublets during heating and cooling cycles and activating additional doublets as needed to meet demand.
Step 2 involved constructing multiple plausible geological scenarios informed by data from other boreholes in London, prior studies on Chalk aquifer heterogeneity, and field observations of Chalk outcrops. Permeability values were calibrated to match borehole flow log data.
Step 3 used the Nelder-Mead optimization technique to iteratively refine model inputs, achieving a match to borehole commissioning test data while maintaining consistency with flow log data. This step resulted in a set of hydrogeological models that provided comparable quality matches to the test data.
In the final step, the Nelder-Mead optimization was employed with the ensemble of models from Step 3 to match the temperature profiles recorded during system operation. This phase posed challenges due to the extended simulation times required. The outcome was a suite of coupled thermo-hydrogeological models that accurately reflected the observed data. The results highlight the critical role of heterogeneity in shaping thermal plume behaviour within the Chalk aquifer. Thin, high-permeability layers lead to "pancake-like" thermal plumes, which exacerbate conductive heat losses and increase the risk of thermal interference between laterally offset boreholes.
These findings emphasise the importance of accounting for subsurface heterogeneity in designing and operating ATES systems. The results are being used to evaluate the feasibility of scaling ATES technology across London.
How to cite: Firth, H., Jacquemyn, C., Hampson, G., and Jackson, M.: History Matching an Operating Aquifer Thermal Energy Storage System in the Heterogeneous Chalk Aquifer under London, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11484, https://doi.org/10.5194/egusphere-egu25-11484, 2025.
Aquifer Thermal Energy Storage (ATES) and Open-Loop unidirectional shallow Geothermal (OLG) systems are delivering low-carbon heating and cooling to the built environment. Both technologies require similar infrastructure: two or more boreholes, hydraulic pumps, heat exchanger(s) and heat pump(s). Both systems also offer sustainable operation when the heat and cool energy injected into, and extracted from, the aquifer is balanced. However, ATES systems benefit from energy storage and re-use, with thermal energy recovery reaching 70-90% for systems with no interference between warm and cool plumes in the aquifer. Here we compare ATES and OLG energy production and energy production per area (energy density) for a suite of common aquifer properties and design decisions. Energy production is an important metric because systems must be engineered to meet an identified demand, but energy density is equally important when systems must operate within a limited surface footprint. All systems investigated here are energy balanced.
Results indicate that ATES systems always produce more energy (on average 80%) than equivalent OLG systems, even when thermal recovery is low. Maximum energy delivery depends on large boreholes spacing and short screen lengths. Maximum energy density increases with increasing screen length and reduced well spacing. The optimal combination for energy production and energy density combines long screens with boreholes spaced just far enough to prevent thermal breakthrough. The thermal plumes produced in ATES deployments have an areal extent that is, on average, 30% larger than that of equivalent OLG systems, but their energy production is much higher, enabling 44% higher energy production for the same area. Given the higher energy production and energy density offered by ATES, and the higher system coefficient of performance resulting from the use of pre-warmed and cooled groundwater, we argue that ATES systems should always be considered ahead of equivalent OLG systems. Furthermore, this means from a planning perspective that more deployments can be packed in the same area.
How to cite: Jacquemyn, C. and Jackson, M. D.: Optimal doublet spacing for Aquifer Thermal Energy Storage (ATES) and open-loop unidirectional shallow geothermal (OLG) systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20345, https://doi.org/10.5194/egusphere-egu25-20345, 2025.
Only a few low-temperature aquifer thermal energy storage sites (LT-ATES) exist in Germany. Our project aims to demonstrate the implementation of a LT-ATES system in an urban area motivated by the increasing demand for cooling in summer. The backyard of an office building complex in Berlin-Mitte was chosen as our test site. Due to the densely built-up conditions, it was not possible to implement a classic doublet system. A coaxial well with a drilling depth of 27 m and a filter distance of 6 m was therefore implemented, which can only be operated using a flow-through principle. In a coaxial well the groundwater is drawn from the lower end of the well system and fed to the heat pump via the inner pipe. After the thermal energy is extracted, the groundwater is re-injected via an outer pipe within the same borehole into a shallower layer. The injection of cooled or heated groundwater in winter and summer, respectively, results in vertical circulation of the groundwater within the aquifer. The permissible temperature spread is limited to 3 K in Berlin. With reference to the local ambient groundwater temperature of around 13 °C, the thermal loading of the aquifer therefore can only vary between 10 °C and 16 °C. The well system was planned as an integrated heating and cooling source as part of the energy-efficient building refurbishment and is used to cover the base load with a maximum flow rate of 6 m³/h. The well went into operation at the end of June 2024.
We monitor the thermal-hydraulic, geochemical and ecological influences on the aquifer using three monitoring wells which are also located in the backyard. Fiber optic cables were installed for depth-differentiated temperature measurements. In addition, continuous measurements of groundwater level, conductivity and flow rates are carried out. To record the thermal influences on the groundwater ecology, groundwater samples are regularly taken at the site and compared with other samples in Berlin.
The potential for seasonal heat storage in the aquifer has been modelled indicating a potential thermal short circuit in the well configuration and raising the question of whether the well system is a seasonal regeneration of the aquifer rather than an active thermal storage. Increasing the distance between the filter sections might solve the problem. Preliminary monitoring results show a significant and increasing influence of the air temperature over the course of the summer and over the entire well length causing a interaction with well operation.
How to cite: Mauerberger, A., Rettenmaier, D., Zorn, R., Blum, P., Herrmann, M., Viernickel, M., Eichelbaum, F., Fleuchaus, P., Katzenmeier, S., Stoeck, T., and Hahn, H. J.: Low-Temperature ATES in Germany: Demonstrating the Opportunities and Limitations in Berlin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17714, https://doi.org/10.5194/egusphere-egu25-17714, 2025.
Decarbonising the heating and cooling sector is essential for reducing our global CO2 emissions. One possibility to achieve significant greenhouse gas emission savings in space heating and cooling is the application of aquifer thermal energy storage (ATES) systems. Hence, this study will provide an overview on the technical potential of ATES systems in Europe. Important criteria for efficient ATES operation considered in this assessment encompass suitable hydrogeological conditions, such as aquifer productivity and groundwater flow velocity, and balanced space heating and cooling demands. Hence, this talk will provide an overview of the future potential of ATES systems in Europe including the chances and barriers for adoption with such systems, which can play an important part in achieving our ambitious climate targets. General aquifer availability and climatic conditions showed potential across Europe about 10 years ago. However, adoption outside a few regions such as the Netherlands and Denmark remained limited. More detailed potential studies confirmed potential in the UK, Spain and Germany. In Germany, more than 50% of the area is suitable for the application of LT-ATES systems. Furthermore, in northern Germany, we could identify key locations for the deployment of LT-ATES by estimating the cooling demand of hospitals with aerial images. Finally, the talk will provide a shortcoming analysis for an improved deployment of ATES systems in Europe and the need for more detailed potential analysis for specific regions.
How to cite: Blum, P., Menberg, K., Stemmle, R., Bloemendal, M., Noethen, M., Bayer, P., Regnier, G., Steffel, I., and Jackson, M.: Potential of aquifer thermal energy storage (ATES) systems in Europe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18919, https://doi.org/10.5194/egusphere-egu25-18919, 2025.
ATES (Aquifer Thermal Energy Storage) is a CO2-free technology for seasonal heating or cooling of buildings based on the storage and recovery of thermal energy in the aquifer. Since aquifers in urban areas are often contaminated with organic pollutants, the application of ATES raises the research question whether this type of heat management can accelerate natural attenuation processes. In the KONATES project, we are investigating how the storage of warm water (70°C) in an aquifer contaminated with trichloroethene (TCE) impacts the aquifer’s microbiome structure and its potential for reductive dehalogenation of TCE. In laboratory experiments we could demonstrate that the native microbiome of the contaminated aquifer can reductively dehalogenate TCE within a temperature range typical for low-temperature ATES (12°C to 25°C). However, these processes are significantly inhibited or entirely absent at temperatures characteristic for intermediate- to high-temperature ATES (30°C to 70°C). The effect of hot water (70°C) injection into an TCE contaminated aquifer on the microbial community composition, with specific focus on thermophiles and organohalide respiring bacteria, was investigated. Additionally, the extent of TCE reductive dehalogenation in the contaminated aquifer and the impact of ATES on this process was assessed using dual-element compound-specific stable isotope analysis, allowing distinguishing from e.g. dilution effects due to mixing of water.
How to cite: Birkigt, J., Hopp, R., Höfgen, H. F., Engelbrecht, B. Z., Keller, N.-S., Kümmel, S., Köhler, R., Weiß, H., Nijenhuis, I., and Vogt, C.: KONATES: A Model Experiment on the Use of Contaminated Aquifers for Heat Management with ATES Plants - Microbiological and Isotopic Investigations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17503, https://doi.org/10.5194/egusphere-egu25-17503, 2025.
For all applications dealing with the production or injection of groundwater, it is extremely important to know the hydraulic characteristics of the aquifer for a proper site planning and successful project development. The hydraulic tests required for this are usually carried out after drilling and setting the filter and include a first well development in order to minimize the influence of the drilling mud and the alteration of the near wellbore area caused by the drilling operation. This normally requires a temporal decoupling of the first well development and the main hydraulic test to be carried out afterwards. In order to optimize the ATES development, a combination of well development and hydraulic testing including physicochemical monitoring is suggested. This method was carried out at the High-Temperature Aquifer Thermal Energy Storage (HT-ATES) site in Berlin Adlershof to show that hydraulic parameters, such as productivity index, skin factor, transmissibility, and storage coefficient can also be determined already during the well development. For this purpose, five- and two-stage step-rate tests were carried out, each with subsequent shut-in phases. The combination of analytical and numerical modelling was employed to analyse the test performance. For the analysis, radially varying permeability around the borehole was assumed in order to identify the influence area of the drilling mud and to determine its transient course. The application of a combination of a classic transient pressure analysis together with numerical models leads to a reliable characterization of the aquifer. For the Hettangian (Jurassic) aquifer, which was accessed via a filter section between 369 and 387 m TVD, this combination of methods, indicates a permeability of 1.5 to 2.0 D and a productivity index of 1.1 to 1.2 l/s/bar. The method enabled to determine the drilling mud influence area which is in the range of 0.35 m and corresponds to, a skin factor of 0.7 to 1.8.
How to cite: Schwarze, C., Pei, L., Virchow, L., Petrova, E., Norden, B., Regenspurg, S., Kieling, K., Blöcher, G., and Kranz, S.: Characterization of the hydraulic properties of a planned Aquifer Thermal Energy Storage (ATES) system during well development, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16166, https://doi.org/10.5194/egusphere-egu25-16166, 2025.
High-temperature Aquifer Thermal Energy Storage (HT-ATES) has the potential to reduce greenhouse gas emissions from the heating sector due to its capability of making excess or renewable based heat from the summer period available in winter. The economic viability of HT-ATES is largely determined by the thermal recovery, i.e. the fraction of recovered heat from the previously injected heat. The heterogeneity of the storage formation has an impact on both the induced thermal plume in the subsurface and on the thermal recovery and results in uncertainties of both parameters. This study aims at quantifying these uncertainties resulting from the subsurface heterogeneity.
The case study of Hamburg-Wilhelmsburg (Northern Germany) is considered, where heat can be stored in the Lower Lignite Sands at around 200 m b.g.l. The geostatistical data basis consisted of 26 boreholes in HH-Wilhelmsburg and 476 boreholes distributed over the whole of Hamburg. The lithologies described in these boreholes were grouped into three indicators with high, medium and low permeability, which were parameterized by literature data. Indicator variogram analysis was applied and the thus derived geostatistical parameters were used for conditional sequential indicator simulation, resulting in 30 realizations of indicator distributions for the model domain. HT-ATES operation was simulated for 26 years by a thermo-hydraulically coupled model with OpenGeoSys. In three additional scenarios with 30 realization each, three different exploration boreholes were added to the conditioning data at a distance of 10 m to the warm ATES well, in order to examine the resulting benefit of such an exploration borehole for reducing the prediction uncertainty.
Simulation results show that considering the heterogeneity of the hydraulic permeability leads to substantial variability in the predicted thermal plume. This spatial uncertainty is reduced in all three scenarios which include an exploration borehole. Also, the predicted warm well return temperatures are significantly less variable between realizations, when the exploration boreholes are included in the conditioning data. For the scenario without an exploration well the mean thermal recovery increases from 36% in the first year to 63% in the 26th year. The standard deviation of the thermal recovery thereby increases from 7% to 10%. The exploration borehole scenarios show different mean thermal recoveries of 29%, 41% and 46% in year one and 53%, 78% and 84% in year 26. The standard deviation is maximum 2% in all three scenarios at all times. This shows, that a large reduction in uncertainty can be expected if an exploration borehole in the direct vicinity of the ATES warm well is available.
How to cite: Heldt, S., Beyer, C., and Bauer, S.: Impact of heterogeneity on high-temperature aquifer thermal energy storage: a case study, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11773, https://doi.org/10.5194/egusphere-egu25-11773, 2025.
Aquifer Thermal Energy Storage (ATES) is an effective solution to store thermal energy but its climate protection potential remains largely unused. Concern about negative changes in groundwater chemistry is often cited as an obstacle especially for HT-ATES (high-temperature ATES), although the underlying results are almost exclusively based on laboratory tests. Increasing temperature in this context up to 80 °C can impact subsurface processes like carbonate precipitation, silicate dissolution, trace element mobility, release of DOC, redox processes and microbial activity including biodegradation. However, to date there is only one HT-ATES field test in which the geochemical impacts on groundwater quality was investigated in detail showing that the geochemical changes were relatively small compared to the variability of the baseline monitoring and were smaller than in associated laboratory tests. However, it is still unclear whether or to what extent these results can also be representative for other sites. In order to expand the basis for assessing hydrochemical impacts, e.g., also for deriving regulatory measures, it is therefore necessary to carry out similar field tests at different sites.
Therefore a HT-ATES field test system was performed in a near-surface quaternary aquifer contaminated with chlorinated hydrocarbons (CHCs < 3 mg/l) in Leipzig, Germany consisting of coarse sands, and gravels and is overlain by a glacial till. The field test system includes 13 monitoring wells, as well as a cold, a warm, and a control well with an injection rate of 0.6 m³/h targeting the horizon at 11-14 mbgs with a temperature of ˜70°C. Before being injected, water was treated using activated carbon filters, zeolites, water softening, and deferrization. Samples were collected during 3 baseline measurements, 3 injection, 3 extraction phases, an interim and a post-operational phase. Samples were analyzed for major ions, trace elements, total inorganic carbon, non-purgeable organic carbon and NH+4. Temperature in the aquifer was 12-62°C during operation.
The concentrations of almost all trace elements during the warm water injection remained within the baseline concentration range. Arsenic, which was below the detection limit at all measuring points during baseline monitoring, increased during the warm water injection to still low values between 2 and 5 µg/L exclusively at one measuring point with the highest temperatures (45-62 °C). The arsenic concentrations decreased from 5 to 2 µg/L between the first and the third warm water injection suggesting that only a very small amount of arsenic can be eluted. Nickel concentrations decreased by up to 30% during warming. Al, Pb, Cd, Cr, Co, Cu, Mo, Se, Tl, V, and Sn stayed below the detection limit and all other elements remained below the no effect levels (GFS/LAWA).
Mobilisation of CHCs from the sediment as a result of the temperature increase was not observed. Instead, dissolved CHC concentrations decreased by up to 90 %. This study reinforces findings from previous research that such temperature variations do not cause critical hydrochemical effects on groundwater quality.
Acknowledgements: This study is part of the KONATES project funded by the German Federal Ministry of Education and Research (03G0916B).
How to cite: Miri, M., Voß, J., Altendorf, D., and Köber, R.: Impacts of Temperature Variations on Geochemical Processes in an HT-ATES System: A Field Site Assessment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17693, https://doi.org/10.5194/egusphere-egu25-17693, 2025.
High-temperature aquifer thermal energy storage (HT-ATES), with its high storage capacity and energy efficiency and its compatibilities with renewable energy sources, arouses broad interest. The density-driven buoyancy flow becomes more significant for HT-ATES, which may lead to a lower thermal recovery efficiency than the conventional low-temperature ATES. Thus, understanding the displacement and thermal transport processes during HT-ATES is essential for predicting and assessing the performance of HT-ATES. In this study, the governing equations for HT-ATES considering the buoyancy flow are nondimensionalized, and five key dimensionless parameters regarding the thermal recovery efficiency are determined. Then, numerical simulations are implemented to study the recovery efficiency for a sweep of the key dimensionless groups for multiple circulations and storage volumes. It is found that the displacement processes can be classified into three regimes: a buoyancy-dominated regime, a conduction-dominated regime, and a transition regime. In the buoyancy-dominated regime, recovery efficiency is mainly correlated to the ratio between the Rayleigh number and the Peclet number. In the conduction-dominated regime, the recovery efficiency is mainly correlated to the product of a material-related parameter and the Peclet number. Then, multivariable regression functions are provided to estimate the recovery efficiency using the dimensionless parameters. The recovery efficiency estimated by the regression function shows good agreement with the simulation results. Finally, well screen designs for optimizing recovery efficiency at various intensities of buoyancy flow are investigated.
How to cite: Gao, H., Zhou, D., Tatomir, A., Li, K., Ganzer, L., Jaeger, P., Brenner, G., and Sauter, M.: Estimation of recovery efficiency in high-temperature aquifer thermal energy storage considering buoyancy flow, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7689, https://doi.org/10.5194/egusphere-egu25-7689, 2025.
Underground thermal energy storage (UTES) offers a promising yet underutilized solution for balancing supply and demand in heating and cooling applications. This is especially relevant within the UK’s decarbonization strategy. Applications such as data centres, which have significant cooling demands and generate waste heat, typically rely on grid electricity for cooling while ejecting heat into the atmosphere. However, UTES presents an opportunity to store this excess heat underground whilst meeting cooling demands. The stored energy can later be extracted for heating purposes, addressing both cooling and heating requirements simultaneously.
This study explores an innovative approach to meeting high cooling and heating demands using novel mixed-circuit borehole heat exchanger (BHE) arrays which combine heat exchange and storage. These arrays are particularly suited for applications with continuous cooling needs, such as data centres. This approach is designed to balance the near-constant cooling loads of data centres with the variable heating demands of nearby residential heating networks, using the ground as an energy buffer. The proposed system employs a network of closed-loop BHEs, where fluid circulates through the subsurface, transferring heat via conduction through the borehole wall. Acting as a temporary UTES buffer, the subsurface enables simultaneous heat injection and extraction in a mixed circuit to meet end-user demands.
To test this concept, mixed-circuit BHE arrays will be trialled at the UK Geoenergy Observatories. During a short-duration experiment, heat and cooling energy will be simultaneously injected and extracted within a shared array, recording thermal plume propagation and fluid temperature within the BHEs. The resulting data will be analysed and used to validate numerical models, providing insights into the feasibility of large-scale mixed-circuit BHE arrays for UTES. These models will contribute to optimizing mixed-circuit arrays for energy security, decarbonizing the heating and cooling sectors, and improving the understanding of UTES systems.
By integrating trial data, the study aims to develop scalable solutions for mixed-circuit BHE arrays, offering cost-effective continuous passive cooling while meeting heating demands. It will focus on optimizing system design, controls, and array performance. The key innovation lies in the real-time integration of cooling and heating within a single system, enabling flexible operation that aligns the steady cooling demands of data centres with the variable heating needs of district networks.
How to cite: Brown, C., Kolo, I., Falcone, G., Friedrich, D., and Watson, S.: Investigating mixed-circuit injection-extraction strategies between borehole heat exchangers in a cooling dominated system, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3141, https://doi.org/10.5194/egusphere-egu25-3141, 2025.
In situ thermal response testing (TRT) is routinely undertaken to determine the ground’s effective thermal conductivity around closed loop borehole heat exchangers. In recent years, development of state of the art in TRT has included the addition of distributed temperature sensing (DTS) to allow insights about the relative thermal properties of specific geological horizons around the ground heat exchanger. In this context, the SmartRes project implememented a novel combined application of fibre optic DTS to track thermal plume development around an open borehole in the Chalk aquifer that had been equipped with a closed loop ground heat exchanger and subject to a heat injection TRT. The test site, Trumplett’s Farm in Berkshire (England), is known to have very high rates of groundwater movement through a dual porosity material, with particular flow concentrations in specific horizons of the highly fractured Chalk aquifer.
The fibre-optic DTS system allowed for measurement of temperature change every 0.5m down the 100m ground heat exchanger, on a 4-minute cycle, and clearly illustrated the different flow horizons in higher detail than with a standard TRT. The high resolution of measurement in space and time permitted even relatively thin geological units with differential ground water flow to be identified. Meanwhile, thermistors at 5m spacing were also installed in adjacent boreholes to monitor temperature changes and showed good agreement with the average temperatures recorded DTS in the same holes.
Based on DTS data and temperatures of the heated circulating fluid, the ground’s thermal conductivity was calculated during the 72h heating phase of the TRT and the recovery phase when heat injection was stopped. The results clearly illustrated the difference in overall thermal behaviour captured by the fluid, and the different stratigraphic units through which the borehole was constructed. The temperature changes in the high ground water flow zones were so subdued due to advection effects that it makes interpretation of the traditional TRT difficult and of limited use in the context of classic closed loop thermal design.
While the techniques illustrated in this field experiment are unlikely to be commercially viable for closed loop geothermal system deployment, they are potentially significant for the development and subsequent monitoring of open loop systems and/or aquifer thermal energy storage. In these scenarios it is much more important to understand the nuances of the in situ hydrogeological regime which may impact plume development and long-term system sustainability.
Keywords: geothermal energy, Thermal Response Test, Distributed Temperature Sensing, thermal conductivity.
How to cite: Kyrkou, K., Booth, A., Loveridge, F., Kelly, J., Jackson, M., Hough, E., and Boon, D.: Distributed thermal response testing in a fractured chalk aquifer with high groundwater flow, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16436, https://doi.org/10.5194/egusphere-egu25-16436, 2025.
The Darcy-scale approach effectively aggregates pore-scale behaviors for hydrogeological applications. However, understanding the influence of pore-scale heterogeneity on the estimation of Darcy-scale quantities (e.g. Darcy flux, dispersion coefficients) remains limited. To address this, the solute and heat tracer experiments were conducted using three different sands with distinct particle size distributions (d50 = 0.52, 0.76, 0.84 mm; U = 1.41, 1.50, 2.02). Tracer front velocities and dispersion coefficients of solute and heat were analyzed by applying analytical models. Observed electrical conductivity and temperature time series demonstrated good agreement with analytical solutions (R2 > 0.9), thereby confirming the validity of the chosen solutions. As the results of examining the tracer front velocity estimates, However, Darcy flux was significantly underestimated in both solute and heat. The underestimation of velocities was more pronounced in smaller particle sizes and wider particle size distributions due to pore-scale heterogeneity arising from the complexity of the pore network. Unlike velocities, normalized dispersion coefficients along with the Peclet number exhibited a larger dispersion for the increase of pore network complexity. Consequently, our findings emphasize considering the potential uncertainty caused by pore-scale heterogeneity on Darcy-scale quantities.
Keywords: Pore-scale heterogeneity; Tracer front velocity; Thermal dispersion; Solute dispersion; Lab-scale experiment
Acknowledgements
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2022R1A2C1006696). This work was also supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government(MSIT) (No. 2022R1A5A1085103). This work was also supported by the Nuclear Research and Development Program of the National Research Foundation of Korea (NRF-2021M2E1A1085200).
How to cite: Baek, J., Park, B.-H., Rau, G., and Lee, K.-K.: Influence of Pore-Scale Heterogeneity on Darcy-Scale Heat and Solute Transport, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6288, https://doi.org/10.5194/egusphere-egu25-6288, 2025.
Thermo-sensitive (TS) tracers have the potential to contribute to the understanding of heat transfer in porous media and ascertain financial revenues by reducing reservoir lifetime prediction uncertainty. The application of TS tracers highly depends on the reservoir velocity distribution and tracer reaction rates. Assuming reservoir properties as homogeneous and isotropic, this study investigated the ability of TS tracers to monitor the thermal front movement. The analytically estimated thermal front positions are compared with the predictions of numerical simulations. Results indicate that the thermal front positions can be accurately estimated using tracer technology, with the overall correlation coefficient between estimated and observed positions exceeding 0.99. Additionally, the front position can be precisely predicted based on the data from observation points. However, prediction accuracy critically relies on the understanding of velocity distribution within the reservoir. Provided the velocity distribution is unknown, the maximum error between the estimation and observation can be ca. 50%. Furthermore, the TS tracer shows high applicability, and can be utilized with a wide range of operational parameters, i.e., injection rate, and reservoir environments, i.e., initial reservoir temperature and porosity.
How to cite: Zhou, D., Tatomir, A., Gao, H., Liu, Q., and Sauter, M.: Thermo-Sensitive Tracer Technology to Monitor the Movement of Thermal Front in Geothermal Energy Production, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7463, https://doi.org/10.5194/egusphere-egu25-7463, 2025.
The utilization of underground thermal energy storage (UTES) systems is essential for balancing fluctuations between high demand and surplus of heating/cooling in modern energy systems. By integrating intermittent renewable energy sources and reducing reliance on conventional energy sources, UTES contributes significantly to a more sustainable heat and cold supply. Long-term seasonal storage, in particular, provides a potential solution for reducing greenhouse gas emissions. In recent years, several UTES systems have been constructed, contributing to the ongoing development and eventual market maturity of various ground-based technologies. Nevertheless, there is no comprehensive environmental evaluation available yet that compares these technologies across their life cycle phases. Thereby, the construction phase is of particular importance, as environmental impacts can vary significantly depending on the type of installation, specific components, and storage size.
This study evaluates the environmental impacts related to the construction phase of three different types of UTES using the life cycle assessment (LCA) framework according to ISO 14040 and 14044. The following three thermal energy storages are comparatively analyzed: a tank thermal energy storage in Munich (Germany), a water-gravel thermal energy storage in Eggenstein-Leopoldshafen (Germany), and a pit thermal energy storage in Marstal (Denmark). Results are further compared with those from an aquifer thermal energy storage (ATES) system in Bonn (Germany). The LCA identifies and quantifies the key factors influencing environmental impacts during construction, highlights significant differences among the technologies, and identifies opportunities for improvement. For instance, the utilization of water as a filling material in closed systems, an underground construction method, and the realization of large storage volumes with a reduced surface-to-volume ratio enhance environmental performance. Conversely, materials such as concrete, steel, foam glass gravel, and polyethylene contribute significantly to the environmental impact and should be replaced or minimized wherever possible, using sustainable alternatives without compromising storage capacity and efficiency.
How to cite: Weise, J., Bott, C., Menberg, K., and Bayer, P.: Environmental impacts from constructing seasonal underground thermal energy storage systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6553, https://doi.org/10.5194/egusphere-egu25-6553, 2025.
Posters on site: Mon, 28 Apr, 16:15–18:00 | Hall X4
Wind turbines may frequently experience shutdowns despite favourable wind conditions due to several factors, primarily related to grid stability and market dynamics. When electricity generation exceeds demand, particularly during periods of high renewable output, operators may be required to curtail production to prevent grid overload. This situation can lead to significant energy waste, as the turbines are unable to contribute to the grid despite their capacity to generate power.
The Power-to-Heat and Underground Thermal Energy Storage (UTES) concepts enhance the utilization of surplus renewable energy sources to generate heat, which can then be stored and used for various applications, including district heating and industrial processes. By integrating wind energy with geothermal resources, these systems can effectively store excess electricity generated during peak wind conditions, converting it into thermal energy for later use. This approach not only addresses the intermittent nature of wind power but also leverages the stable and consistent characteristics of geothermal energy.
This study explores the preconditions for implementing a wind-geothermal energy storage system tailored to the resources and environmental landscape of Poland. The analysis includes existing wind farms and examines the strategic placement of wind turbines across the country, highlighting regions with optimal wind potential as identified in various meteorological assessments. The northern parts of the country exhibit the highest onshore and offshore wind potential; however, this is not aligned with the geothermal resources available.
Furthermore, a detailed mapping of both shallow and deep geothermal potential will be presented, which is critical for effectively integrating geothermal energy into the proposed storage system. The study considers Aquifer Thermal Energy Storage (ATES) systems, which could enhance energy efficiency and stability in conjunction with wind energy production, serving as a Power-to-Heat example.
By synthesizing data on wind potential, existing infrastructure, and geothermal resources, this study aims to outline a framework for developing a sustainable and resilient energy storage solution. The research is conducted using publicly available spatial data and Geographic Information Systems (GIS) to ensure comprehensive analysis and visualization of the relevant resources.
How to cite: Halaj, E.: Preconditions for a Wind-Geothermal Energy Storage system, a case study from Poland , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-286, https://doi.org/10.5194/egusphere-egu25-286, 2025.
Quantifying advective heat transport in sedimentary aquifers is crucial for understanding processes and applications such as shallow geothermal systems, streambed flux estimation, and aquifer property assessment. Heterogeneous aquifers are ubiquitous and present significant challenges, as the substantial variability in hydraulic conductivity gives rise to preferential flow pathways, non-uniform temperature fronts, and enhanced thermal dispersion. This study systematically conducts direct numerical Monte-Carlo simulations using the Multiphysics Object-Oriented Simulation Environment (MOOSE) to analyze heat transport. We simulate the evolution of a heat plume generated by a borehole heat exchanger in a three-dimensional aquifer of heterogeneous hydraulic conductivity. We characterize the evolving heat plume by calculating dispersion coefficients and effective thermal retardation factors, defined as the ratio of the thermal front velocity to the seepage velocity, averaged over an ensemble of heterogeneous realizations. In addition, we consider varying degrees of heterogeneity and examine the role of the thermal Péclet number in influencing the effective thermal retardation factor.
Results show that for aquifers with homogeneous hydraulic conductivity, the effective thermal retardation factor matches the theoretically predicted apparent thermal retardation factor. However, in heterogeneous systems, the effective thermal retardation factor is significantly reduced compared to the apparent value during the initial phases of transport. This discrepancy becomes more pronounced with increasing thermal Péclet numbers. The reduction in the effective thermal retardation factor can be explained by preferential flow through high-conductivity zones and delayed heat diffusion into low-conductivity regions. We link this phenomenon to local thermal non-equilibrium (LTNE) effects occurring at the field scale. Our findings reveal insights into heat transport in hydraulically heterogeneous systems and highlight the importance of field-scale LTNE effects. Considering these effects in real-world applications, for example field tracer tests in heterogeneous streambeds or shallow geothermal energy use, could improve process understanding, predictions and optimized design.
How to cite: Gebhardt, H., Zech, A., Rau, G., and Bayer, P.: Thermal retardation in porous media of macro-scale heterogeneity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3454, https://doi.org/10.5194/egusphere-egu25-3454, 2025.
Seasonal Underground Thermal Energy Storage (UTES) offers a promising solution to balance future energy supply and demand. Specifically, Aquifer Thermal Energy Storage (ATES) systems facilitate the seasonal storage of energy, providing up to 10–100 MW of thermal output that can be utilized during periods of high energy demand (Dinkelman & Van Bergen, 2022). These systems store surplus heat from sources such as geothermal or power-to-heat systems, particularly from fluctuating renewable energy during summer. The extracted water is heated, reinjected into the ground via an injection well for storage and later retrieved through a production well during colder seasons. Despite the widespread adoption of ATES systems across Europe—especially in the Netherlands—Austria currently lacks any operational ATES plants.
The “ATESref” project presented here aims at evaluating the geological, technical, and economic feasibility of seasonal heat storage in the medium-to-deep subsurface of the Fürstenfeld area in the Styrian Basin (Austria). Geological studies and reprocessing of existing seismic profiles are used to estimate the depth, thickness, and spatial distribution of potential storage formations in coarse grained Neogene sediments, such as the Sarmatian-aged Carinthian gravel (approximately 650 m below ground level) and the Badenian Sandschaler Zone (approximately 1,600 m below ground level). Existing boreholes provide well logging data for deriving hydraulic parameters, which are incorporated into a numerical model. Subsequently this model helps to simulate plant operations, predict thermal effects on the subsurface, assesse impacts on third-party water rights, and estimate the potential of storable thermal energy.
The numerical model will then be refined into a storage simulation model, ensuring parameter accuracy and plausibility. This model will address questions about integrating the storage system efficiently into the existing district heating network. System simulations will evaluate the yields and loads for the Fürstenfeld case study, aiming to optimize renewable energy usage and incorporate existing excess heat sources.
Given that most storage horizons lie within the basin fill, reinjection of thermal water into the clastic sedimentary aquifers is a critical factor. Austria currently lacks deep geothermal applications in both unconsolidated and consolidated clastic sediments. A previous attempt to operate a doublet system in Badenian sediments failed due to abrupt collapse of the reinjection process. Findings from the completed “Reinjection” project point to technical causes behind this failure. Building on these insights, the “ATESref” project will develop a concept to reactivate this system for the use-case in Fürstenfeld, paving the way to achieve reinjection.
References:
Dinkelman Dorien & Van Bergen Frank: Evaluation of the country-wide potential for High-Temperature Aquifer Thermal Energy Storage (HT-ATES) in the Netherlands, European Geothermal Congress, Berlin, 2022
How to cite: Hölbling, M., Petschacher, N., Schreilechner, M., Muhr, D., Vasvári, V., Eichkitz, C., Böchzelt, B., Brunneder, M., and Hengel, F.: ATESref - Aquifer Thermal Energy Storage and Reinjection using the example of Fürstenfeld, Austria, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5218, https://doi.org/10.5194/egusphere-egu25-5218, 2025.
Seasonal thermal energy storage (sTES) is elementary for decarbonizing district heating systems in urban areas. To overcome related land use conflicts, the re-use of idle infrastructure or industrial facilities is proposed. Existing infrastructure and basins can be refurbished as large-scale heat storage devices. This avoids demolition efforts and construction costs for new concrete structures or the application of costly components (e.g., insulation layers). However, structures not specifically designed for sTES may experience notable challenges that compromise efficiency, including suboptimal geometries or interactions with shallow groundwater conditions.
Our study presents an innovative approach for dealing with increased heat losses of poorly insulated Reno-sTES facilities installed in shallow aquifers. In the groundwater downstream, we propose and test the installation of a geothermal trench that is connected via a geothermal heat pump with the same energy system. The objective is to optimize the technical performance and robustness of the sTES by integrating the ambient ground as an additional storage medium, and by “recycling” ambient heat loss. Using a further development of the previously presented STORE model [1,2]. For simulating water-gravel thermal energy storage, the effects of various (e.g., geometrical) geothermal trench setups are analyzed, revealing thermal impacts, ideal configurations, and optimal operation modes. Based on a synthetic study, we focus on both the performance of the geothermal trench and the Reno-sTES. The scenario analysis with generalized parameter settings (e.g., different groundwater regimes, geothermal trench operation schemes) reveals the applicability of this innovative approach for optimizing closed-loop, ground-based sTES implementations in practice.
References:
- [1] Bott, C., Ehrenwirth, M., Trinkl, C., Bayer, P. (2022). Component-based modeling of ground-coupled seasonal thermal energy storages. Applied Thermal Engineering, 118810.
- [2] Bott, C., Dahash, A., Noethen, M., Bayer, P. (2024). Influence of thermal energy storage basins on the subsurface and shallow groundwater. Journal of Energy Storage, 92, 112222.
How to cite: Bott, C., Hoffmann, D., and Bayer, P.: Recycling of subsurface heat loss from thermal energy storage basins through geothermal trenches, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5644, https://doi.org/10.5194/egusphere-egu25-5644, 2025.
In the KONATES project a pilot-scale Aquifer Thermal Energy Storage (ATES) system at the scientific park in Leipzig, Germany has been built, where the shallow quaternary aquifer is contaminated with chlorinated hydrocarbons. To demonstrate the integration of thermal energy storage and groundwater remediation, a surface remediation system works alongside the ATES facility.
Especially when ATES systems are located in an urban environment, regulatory limits are present on temperature increases at property boundaries, typically restricting them to a few Kelvin, while the injection temperatures range between 70 °C and 80 °C. This requires careful planning of injection and extraction cycles and flow rates to fulfill these regulations.
Complicated by dense infrastructure and the need for numerous monitoring wells to observe hydraulic, thermal, geochemical, and microbiological changes, the pilot-scale ATES operation requires a three-dimensional numerical model to simulate hydraulic flow and heat transport in the aquifer. This model predicts heat transport in the subsurface based on varying injection timeframes and flow rates.
Considering regulatory constraints and high groundwater velocities, the model recommends an operational strategy of two 10-day injection cycles each followed by 10-day extraction periods at a pumping rate of 0.6 m3/h and an injection temperature of 70 °C. The first batch of monitoring data shows that the numerical model predictions were successful in predicting the groundwater temperatures for the experiment. Meanwhile, it is also found that the aquifer is more heterogeneous than previously assumed. Implementing those behaviors in the model is an ongoing task to optimize the next experiment runs.
This work highlights the value of coupled hydro-thermal models in designing ATES systems to meet regulatory and site-specific challenges in urban environments.
How to cite: Dörnbrack, M., Weiß, H., and Shao, H.: Models for the experiment design of a combined ATES and remediation pilot plant in an urban environment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5675, https://doi.org/10.5194/egusphere-egu25-5675, 2025.
Groundwater is an important global resource, providing water for industry, irrigation, geothermal uses and potable water. Moreover, groundwater harbours the world's largest terrestrial freshwater biome. Climate change and anthropogenic activities cause diverse changes in groundwater systems. Particularly, these processes lead to an increase in groundwater temperature under densely populated urban areas. While physico-chemical effects have been widely studied, the consequences for groundwater ecosystems are scarcely understood. Thus, understanding how these sensitive ecosystems respond to stressors, such as temperature increase and oxygen depletion, is crucial for sustainable groundwater management, especially in cities.
Our work aims to provide a spatial and temporal overview of groundwater fauna (stygofauna) in two cities in Germany to identify alterations in groundwater fauna due to natural or anthropogenic impacts. To this end, groundwater fauna and several (hydro-)geological, site-specific, climatic and physico-chemical (water) parameters are analysed in 39 monitoring wells in Karlsruhe and 406 wells in Berlin, respectively.
In Karlsruhe, statistical analyses indicate a connection between abiotic groundwater characteristics, such as temperature and dissolved oxygen, and land use. The groundwater temperature shows a warming trend towards densely built-up areas within the study area, yet no substantial change in temperature can be observed over time. In contrast, the oxygen content shows spatially and temporally unstable conditions, with a significant decrease over time, presumably due to degradation processes and a low oxygen input. Also, differences in the spatial distribution of groundwater fauna species due to abiotic groundwater characteristics are identified. Over time, the groundwater fauna community in Karlsruhe has remained largely stable. However, the number of individuals has decreased significantly, which coincides with decreasing contents of dissolved oxygen.
In Berlin, six investigation sites were selected for a detailed assessment of relevant influences on stygofauna. No correlation with groundwater temperature was found based on the data from the individual sites, although a warming trend towards Berlin's city centre is visible. Land use, dissolved oxygen content and exchange with surface waters are the main factors impacting the faunal colonisation of monitoring wells. Generally, urban sites with low oxygen levels and certain levels of pollutants show unfavourable living conditions. In contrast, sites outside the city centre, in nature reserves and close to surface waters contain a more diverse faunal community with more individuals. Based on these findings, a conceptual model was developed to showcase processes and interactions in the groundwater of Berlin.
The results of our study reveal heterogeneous and time-varying conditions in urban groundwater as a habitat. The influence of temperature and, thus, potential geothermal energy systems on groundwater fauna could not be statistically proven for both cities. However, both study areas share the dependence of the groundwater fauna on the content of dissolved oxygen. Contrary to Karlsruhe, the land use in Berlin influences the fauna composition, as the fauna in Berlin depends on the surface water impact. Information on urban groundwater ecosystems should be integrated into urban and energy planning for sustainable subsurface use. In addition, studies in other cities with large-scale, repeated measurement campaigns are necessary to verify our results.
How to cite: Glatting, F., Schmid, L., Bindschädel, E., Hemmerle, H., Bölscher, J., Geppert, M., Blum, P., and Menberg, K.: Effects of anthropogenic impacts on urban groundwater fauna, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8671, https://doi.org/10.5194/egusphere-egu25-8671, 2025.
Aquifer thermal energy storage (ATES) is a well-established technology that bridges the seasonal mismatch between summertime heat supply and wintertime heat demand. Due to the storage of available excess heat, such as waste heat, it promotes the decarbonization of the space heating sector. Typically, a minimum transmissivity of the storage formation is required for ATES to achieve the necessary capacity of the pumping wells. However, depending on local hydrogeological conditions or existing subsurface usage, such high-transmissivity aquifers may not always be available, and the use of low-transmissivity aquifers may be required. In such cases, the applicable pumping rate per well may be significantly limited to prevent aquifer depletion and mechanical uplift of the confining layer, increasing both the required number of well doublets and the complexity of the system design.
Here, an analytical approach is presented to determine the minimum required number of well doublets and their spacing, considering both thermal and hydraulic design constraints. Commonly used well separation rules based on the thermal radius serve as the thermal design constraint to avoid thermal interference between wells and limit the minimum well distance. The maximum allowable head change defines the hydraulic design constraint and limits the maximum well spacing. In multi-doublet well fields, the superposition of pressure fields of adjacent wells may notably affect the observed head change, which in turn impacts the possible pumping rate. Consequently, this approach is derived for typical ATES-well field configurations, i.e., the “lane” and “checkerboard” layout.
This method is demonstrated in a case study of a low-temperature ATES on the campus of Kiel University in Germany. Results show that for lower transmissivities, the “checkerboard” layout requires fewer well doublets than the “lane” layout to achieve the specific target pumping rate of 200 m3/h. Depending on the assumed geological and operational conditions, up to eleven well doublets are required for the “lane” layout, whereas nine well doublets are sufficient for the “checkerboard” layout. This is because the increased hydraulic superposition between injecting and extracting wells reduces the observed head change and, in turn, increases the possible maximum pumping rate per well. This method allows to facilitate better ATES system design during an initial feasibility study or potential assessment by integrating both thermal and hydraulic constraints, thereby potentially reducing overall capital and well maintenance costs.
How to cite: Nordheim, J. N., Beyer, C., and Bauer, S.: Analytical dimensioning of ATES system size and well spacing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9040, https://doi.org/10.5194/egusphere-egu25-9040, 2025.
Groundwater beneath urban areas is affected by a number of natural and anthropogenic factors, such as geological and hydrogeological characteristics, as well as dense anthropogenic infrastructure, such as surface land use, heated basements, underground car parks, and train tunnels. Understanding groundwater flow and heat transport processes in such complex urban areas is therefore essential not only for planning thermal and hydraulic subsurface uses, but also for ecological and sustainable management of urban aquifers. This also involves examining the key hydrogeological or anthropogenic characteristics that influence subsurface thermal conditions, thereby supporting decision-making for management purposes. Physics-based numerical models excel at simulating flow and heat transport at different scales, adopting various assumptions. However, a realistic 3D city-scale model in a complex geological setting requires an accurate and computationally efficient approach, as management purposes need iterative simulation of different usage scenarios.
To this end, a 3D groundwater flow and heat transport model is developed for Berlin, for an area covering 118 km². It is based on a detailed 3D geological model created with Leapfrog Geo software using available geological data. To reduce computational time, the area is divided into smaller blocks, each representing the hydro-geological and anthropogenic characteristics of the heterogeneous urban area. Initially, all blocks are simulated at low resolution for different combinations of geological and anthropogenic characteristics to generate input-output relationships between these characteristics of each volume and the groundwater temperatures. Resulting input-output pairs are then used to cluster the modeled volumes into archetypes with similar hydrogeological behavior and thermal states by utilizing a decision tree approach. Finally, simulated archetypes are spatially re-combined to create a city-scale temperature map. Furthermore, to assess the key characteristics governing the thermal status of groundwater, contribution of each parameter to the decision tree is calculated.
The results reveal that, among all, the area of heated basements contributes most to groundwater temperature distribution, especially for the blocks where there is no substantial groundwater flow and conductive heat transport processes dominate. However, for the blocks with sufficient flow, upstream temperature entering the blocks is the main characteristic. Moreover, our findings highlight a close link to surface land use. As an example, the average temperature in Tiergarten location, which is a green area with a less anthropogenic influence is found to be around 11.8 °C to 12.0°C, on shallowest depth of blocks i.e. 0-50 m below ground, while in densely built-up areas, such as Alexanderplatz, the temperature could raise to 14.8°C. Furthermore, using the resulting temperature map, enables us to identify local hotspots or low-spots, which is not possible to observe in alternatives such as interpolated maps created from a dense number of measurements.
This study presents a computationally efficient city-scale modeling approach, which in future could be utilized as a tool for performing iterative simulations for different subsurface use scenarios such as geothermal use, drinking water use, or protecting ecological habitats. Also, it provides a tool for investigating long-term climate change effects on groundwater quality and for assessing groundwater quantity and quality at city-scale.
How to cite: Hajizadeh Javaran, M. R., Kreitmair, M., Makasis, N., Blum, P., and Menberg, K.: 3D City-scale groundwater flow and heat transport modelling using an archetype approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11384, https://doi.org/10.5194/egusphere-egu25-11384, 2025.
Austria is committed to achieving climate neutrality by 2040, and no later than 2050. Implementing seasonal heat storage can aid in decarbonizing district heating networks (DHNs) by storing excess heat from summer for use during the heating season. High-temperature aquifer thermal energy storage (HT-ATES) provides an affordable and large-scale solution for storing hot water, provided that suitable geological conditions and excess heat for storage are available. This study explores the potential for implementing HT-ATES technology in Austria by identifying sedimentary rock formations suitable for HT-ATES and analyzing spatial datasets, such as the distribution of district heating networks across the country and the corresponding heating demand. To assess the need for seasonal heat storage, operators of Austria’s largest DHNs were consulted. An open-source Python-based tool (FATES) was employed to evaluate subsurface storage performance. After identifying key parameters for each assessed ATES site, a Monte Carlo simulation was conducted to estimate the probability distribution of the heat recovery factor and the heat production during discharge.
How to cite: Kulich, J., Khasheei, M., Ott, H., and Yoshioka, K.: Austria’s Potential for High Temperature ATES, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17521, https://doi.org/10.5194/egusphere-egu25-17521, 2025.
Underground Thermal Energy Storage (UTES) technologies are essential for advancing low-carbon heating and cooling systems, particularly in urban areas where space constraints and retrofitting challenges pose significant barriers. In this study the performance of a system of novel coaxial diagonal borehole heat exchangers (BHE) is analyzed during September–December 2024.
The Home Smart Energy (HSE) system, implemented in Medemblik, Netherlands, features a nine-borehole diagonal array arranged in a circular configuration. The boreholes are drilled at a 60° or 45° angle to depths of up to 40 meters, operating in a closed-loop coaxial setup. A brine mixture of water, operates with a flow rate of 3100 l/h, and 14% glycol lowers the freezing point below 0°C, allowing the system to supply higher capacities. The heat pump extracts the heat from the BHE’s, supported by solar thermal collectors to charge the BHE’s in summer, ensuring efficient year-round heating. An extensive monitoring framework, including Distributed Temperature Sensing (DTS), provides detailed insights into system performance during operation.
The HSE system demonstrated consistent performance under varying configurations and conditions. With all nine boreholes active, the system achieved a seasonal Coefficient of Performance (COP) ranging from 3.8 to 5.2, with daily energy outputs averaging 125 to 220 kWh/day. During December 2024, tests were conducted using three boreholes in different configurations at a reduced flow rate of 2800 l/h. These tests showed that borehole arrangement moderately influenced system performance, with the adjacent configuration achieving slightly higher energy outputs and COP, compared to the dispersed configuration.
The system also demonstrated significant energy cost savings of €954 during November and December 2024, attributed to a reduction in gas consumption by over 700 m³ compared to the previous year. These findings confirm that diagonal shallow co-axial borehole arrays are a scalable and sustainable UTES solution, offering substantial energy savings and CO₂ reductions in dense urban settings.
Keywords: UTES, diagonal boreholes, geothermal energy, COP, solar thermal storage, urban heating, thermal recovery.
Acknowledgments: This work is funded by de Vreeden, Eiland Medemblik BV (EM), TSH, and Kansen voor West / EFRO in the “Home Smart Energy” project
How to cite: Hashemi, A., Bloemendal, M., Vardon, P., Goverse, P., and De Rechter, G.: Efficient Urban Geothermal Heating with a Compact Diagonal Borehole Heat Exchanger Array: Seasonal Performance and Configuration Insights, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17602, https://doi.org/10.5194/egusphere-egu25-17602, 2025.
Post-mining sites have become a focus of interest for researchers in terms of their potential use as energy storage sites. One of such ideas is the concept of Adiabatic Compressed Air Energy Storage (CAES) in mine shafts, developed and patented by scientists from Silesian University of Technology. This idea incorporates a suspended TES (Thermal Energy Storage) bed filled with accumulation material. The key element of the system's effectiveness is the selection of the proper accumulation material. This material should have a high ability to accumulate and retain heat, be economical, easily accessible, and have a low environmental footprint.
This research presents the results of analyses of geomaterial mixtures based on wastes from basalt open-pit mines and aggregate processing waste, with the addition of cement binders. In particular, the focus was on the use of basalt dust, which is a by-product of dedusting and basalt processing. The tested mixtures are used to construct a packed bed of granular material.
Thermal properties of the mixtures, such as heat capacity, were analyzed using the Thempos SH-3 sensor from Meter. The heat capacity of the tested mixture was determined to be 1.9 C [MJ/m3×K], compared to the heat capacity of basalt, which ranges from 0.7 to 2.14 C [MJ/m3×K].
Flow analysis demonstrated that a bed with a regular grain shape heats up 12% faster than a bed with irregular grain shapes. The geometry of the granular bed significantly impacted air flow and heat distribution, with regular-shaped beds providing better and more uniform results compared to irregular beds.
The study highlights the potential application of waste-based geomaterial mixtures in thermal energy storage systems, emphasizing their thermal performance and suitability for packed bed construction. These findings contribute to the development of sustainable energy storage solutions leveraging post-mining and industrial by-products.
How to cite: Snarski, O., Korpak, W., Kołodziej, K., and Lutyński, M.: Evaluation of Geomaterial Mixtures for Sustainable Energy Storage Solutions especially in Post-Mining Sites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18279, https://doi.org/10.5194/egusphere-egu25-18279, 2025.
Aquifer Thermal Energy Storage (ATES) offers sustainable, low carbon heating and cooling to the built environment. Optimising the design and operation of ATES installations requires numerical simulation of groundwater flow and heat transport in heterogeneous aquifers. These simulations are typically computationally expensive: high spatial resolution is required to properly resolve pressure, flow and temperature fields; moreover, high temporal resolution may be necessary to control numerical diffusion and/or resolve frequent changes in injection flowrate and temperature. Simulations of systems that utilize multiple boreholes, or when the interactions between neighbouring systems must be captured, are particularly challenging. Multiple simulations may be required to quantify the impact of uncertain aquifer heterogeneity. Yet the time available for aquifer modelling in many commercial projects is very limited. Rapid but accurate approaches to simulate subsurface flow and heat transport in ATES and other shallow geothermal deployments are urgently required.
Machine Learning (ML) offers a rapid alternative to conventional numerical simulation of complex subsurface flow and transport processes. Here we introduce the use of a Graph Neural Network (GNN)-based ML approach, on a purely data-driven basis, to significantly increase simulation efficiency whilst retaining its accuracy. The ML proxy is trained using outputs from our in-house Imperial College Finite Element Reservoir Simulator (IC-FERST), an advanced code that uses dynamic mesh optimization to provide high solution accuracy at lower computational cost. The practical consequence here is that the mesh changes between solution snap-shots used for training. Conventional Convolutional Neural Network (CNN)-based models require a fixed mesh. Here, to enable a fast proxy under variable mesh, we implement a GNN-based model with auto-regressive approach.
We demonstrate that heat transport in the aquifer can be accurately captured by deploying an auto-regressive graph U-net architecture on the unstructured graph data. As a pioneer model in the field, it is proven to successfully replicate subsequent time steps on any given mesh topology of the current state. To further unleash the potential of our GNN-based approach, we further introduce a transformer-based Graph neural network to enable a stronger capability in capturing long range changes under continuous latent rollout. The model can take in the initial state of the reservoir in arbitrary mesh, perform prediction in latent rollout, and recover the latent representation of the prediction back to physical space on any given query mesh, allowing the integration of adaptive mesh refinement adjusted to fit the predicted solution on unstructured graphs.
Our results suggest a promising approach to rapid simulation of ATES, in which simulation times are reduced from tens of hours to a few minutes.
How to cite: Fung, N. H., Wen, G., and Jackson, M.: Rapid simulation of Aquifer Thermal Energy Storage using Machine Learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19992, https://doi.org/10.5194/egusphere-egu25-19992, 2025.
Geothermal energy is widely recognized as a key contributor to decarbonization. Nevertheless, as of 2023, 81% of Germany's heating and cooling energy demand was still met by fossil fuels, with only 13% supplied by geothermal systems. Aquifer Thermal Energy Storage (ATES) offers a solution to bridge the gap between seasonal thermal energy supply and demand by storing excess heat in summer and cold in winter.
Germany's aquifers, particularly in the North German Basin (NGB), Upper Rhine Graben (URG), and German Molasse Basin (GMB), hold significant potential for geothermal applications at both shallow and greater depths. For the NGB, siliciclastic aquifers in the Lower Jurassic (Hettangian-Pliensbachian) and Upper Triassic (Rhaetian) formations are promising targets for deeper ATES systems. However, high-temperature ATES applications at greater depths remain rare, primarily due to high investment costs, operational uncertainties, and associated risks.
A key requirement for sustainable ATES operation is to maintain the mechanical, physical, and chemical stability of the subsurface. Changes in physico-chemical boundary conditions, such as temperature fluctuations, oxygen intrusion, and carbon dioxide outgassing, can adversely impact groundwater quality, hydraulic permeability, and well integrity. Key processes causing porosity alterations include ochre formation and incrustation from iron and manganese precipitation, aluminium precipitation, sintering and silicification from lime, silicate, sulfate, or sulfide deposits, sanding and colmation, and biofilm formation through microbial activity.
This study investigates fluid-mineral interactions in a siliciclastic aquifer of Hettangian age in Berlin, representative of the North German Basin. Numerical modelling was conducted, using the geochemical code PHREEQC version 3.7.3, to study the impact of gas pressure and temperature on fluid-mineral equilibria. Specifically, the effects of groundwater temperature at constant partial gas pressures were analysed. Furthermore, the tendency for mineral precipitation/dissolution was evaluated under varying partial pressures of carbon dioxide and oxygen at selected temperatures (5°C, 20°C, 40°C, 60°C, 80°C), simulating the effects of carbon dioxide outgassing and oxygen intrusion on the reservoir. Using the site specific mineralogical and geochemical composition, we numerically investigate the effects of ATES-induced boundary conditions on mineral precipitation and dissolution, with a focus on porosity alterations in saline groundwater environments. Results are presented as contour plots visualising precipitation and dissolution trends as a function of temperature and carbon dioxide or oxygen concentration in anoxic aquifers with low or negligible carbonate content.
The findings aim to enhance the understanding of deep ATES applications and develop strategies for mitigating risks to ensure sustainable operation. This research provides valuable insights into the challenges and opportunities of deeper ATES systems in siliciclastic formations, contributing to the broader goal of decarbonizing Germany’s energy sector through innovative geothermal solutions.
How to cite: Kliwer, T., Schiperski, F., Gitter, M., and Neumann, T.: Aquifer Thermal Energy Storage (ATES) in Berlin – Numerical Assessment of Challenges and Opportunities in Deeper Siliciclastic Aquifers from a Geochemical Perspective, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19865, https://doi.org/10.5194/egusphere-egu25-19865, 2025.
Aquifer Thermal Energy Storage (ATES) systems are gaining attention as a method to store surplus thermal energy in aquifers. However, during ATES operation, changes in pressure and temperature conditions can initiate clogging and scaling processes, leading to operational and maintenance issues or failures. In the “UnClog-ATES” project (funded by the BMBF, Germany), we investigate clogging and scaling processes in carbonate aquifers and develop countermeasures such as scaling inhibitors or CO₂ addition through an interdisciplinary approach that combines microbiology, geology, hydrogeology, and geochemistry.
Aiming at carbonate aquifers, we used two types of limestone: i) Jurassic limestone from Upper Malm, Germany ("Treuchtlinger Marmor”; primarily calcite) and ii) Marble from Hammerunterwiesenthal, Germany (“Erzgebirgsmarmor”; mainly composed of calcite and dolomite). Water samples from the Erzgebirge marble quarry served as fluid phase in all experiments, which were conducted at ATES-relevant temperatures (5–60 °C).
Shaking experiments (0-D) assess the influence of hydrochemical environments and rock compositions on rock and fluid alteration. A series of time-dependent shaking experiments at 5, 40, and 60 °C revealed that, with Erzgebirgsmarmor, Ca concentrations in fluid decrease over time at all three temperatures, while Mg concentrations increase. Conversely, Treuchtlinger Marmor exhibits the opposite behavior. PHREEQC modeling of the 60 °C experiments predicts precipitation of dolomite, calcite, aragonite, and vaterite.
1-D column experiments systematically simulate ATES conditions, including temperature and chemistry to model transport processes. Preliminary results at 12 °C with Treuchtlinger Marmor indicate precipitation of dolomite, calcite and aragonite. Early findings from a 40 °C test run comparing both carbonate rocks show differences over time and compared to the results at 12 °C in pH, electric conductivity and alkalinity.
These results highlight the need of further site specific investigations to enhance our understanding of hydrochemical processes and reactions during ATES operations. Findings from this study will improve the prediction of dissolution and precipitation processes and the development of effective countermeasures for clogging and scaling during ATES in carbonate aquifers.
How to cite: Gabler, L., Arab, A., Schiperski, F., and Scheytt, T.: Hydrochemical Reactions during Aquifer Thermal Energy Storage (ATES) in Carbonate Aquifers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19087, https://doi.org/10.5194/egusphere-egu25-19087, 2025.
High-Temperature Aquifer Thermal Energy Storage (HT-ATES) can provide flexibility to the heat provision systems as required by the transient fluctuation in the thermal energy demand. Such multicomponent-system concepts are currently experiencing increasing attention in the German Molasse Basin (southern Germany), where, HT-ATES can compose an essential element of the energy systems, contributing towards the transition to decarbonized heat supply. In this work, we highlight an example from the greater area of Munich to analyze the efficient integration of seasonal high-temperature heat storage in the highly utilized Lower Cretaceous and Upper Jurassic geothermal reservoir (North Alpine Foreland Basin) into a local District Heating Network (DHN). The favorable geographic location in the greater area of Munich holds the advantage of large amounts of available excess energy and suitable subsurface conditions for HT-ATES concept development, combined with large DHNs to utilize the surplus energy. The case study network operates within a range of 72 °C up to 94 °C in dependency to the atmospheric temperature. It is equipped with a geothermal plant comprising its prime heat source element, while it is further supported by a supplementary conventional fossil-fuel powered heat provision unit to cover peaks in demand and redundancies.
Our energy system analysis aims at extending the investigated network by numerically integrating the HT-ATES in the form of a seasonal heat provision component to cover peak loads, and thus partly replace the fossil-fueled heat generator. To this end, we initially elaborate on the efficient design and operation of the multicomponent energy system with focus on the integration of the HT-ATES into the heat supply scheme. Subsequently, the co-simulation approach that captures the interaction between the different subsystem elements is in focus. The HT-ATES system is simulated with the MOOSE-based GOLEM numerical code, and describes the thermal-hydraulic processes triggered by the storage of high-temperature fluids with 110 °C into the Lower Cretaceous and Upper Jurassic geothermal reservoir. In parallel, the DHN is modelled with the TRNSYS-TUD software environment and, apart from the thermal-hydraulic parameters of the analyzed DHN, it additionally provides the transient accumulated load curve. The coupling of the two systems requires the exchange of both the operating mass fluxes and fluid temperature between the two modelled systems.
How to cite: Tzoufka, K., Bock, K., Blöcher, G., Lehmann, L., Cacace, M., Pfrang, D., Felsmann, C., and Zosseder, K.: Performance assessment of subsurface seasonal thermal energy storage coupled with a geothermal-powered district heating network: an example from the German Molasse Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19340, https://doi.org/10.5194/egusphere-egu25-19340, 2025.
