Aquifer Thermal Energy Storage (ATES) systems use reversible abstraction and injection in combination with warm and cold wells to provide efficient heating and cooling solutions at scales up to ~0.5 MW per installation. It has been shown that these systems are able to improve the efficiency of thermal installations, but rely on an appropriate design, especially when several ATES systems share the same aquifer. In this work, we combine groundwater flow and heat transport numerical models with optimization frameworks to investigate the optimal distribution of wells for avoiding system interferences and improving recovery efficiency. To that end, we employ hypothetical modelling scenarios based on geological properties of the Sherwood Sandstone bedrock aquifer as one of the main potential targets for the development of ATES systems in the UK. Some of the available information is acquired from activities at the UK Geoenergy Observatory (UKGEOS) in Cheshire, which is under construction and will be equipped with a range of technologies and monitoring sensors for research, training, and on-site experiments. The Observatory will be open to industry and the research community to evaluate technological options for shallow geothermal use and energy storage and to gain a detailed hydraulic and thermal characterization of the Sherwood Sandstone. As practical application, we present an approach for the optimal design of the installation of multiple doublets that consider various spatial features as decision variables. The benchmark solution is provided by a simulation-optimization framework that uses a direct coupling of the groundwater flow and heat transport numerical model with an evolutionary algorithm. This approach is typically hampered by increased computational cost due to the time-intensive numerical simulations and the thousands of objective function evaluations required until convergence of the evolutionary algorithm is achieved. Therefore, we also investigate a lower computational resource strategy by applying surrogate-assisted optimization methods which are either embedded in the operations of the evolutionary algorithm or utilize an adaptive-recursive framework. The performance of the surrogate-based optimization method is assessed via several independent optimization trials and for different computational budgets. The ability of the surrogate-based optimization frameworks to approximate a near global solution is compared against the benchmark solution.

How to cite: Christelis, V., González Quirós, A., Abesser, C., Boon, D., Hough, E., and Spence, M.: Integration of at-scale field observations and application of surrogate modelling strategies for optimal design of ATES systems in the Sherwood Sandstone aquifer, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8903, https://doi.org/10.5194/egusphere-egu23-8903, 2023.

Aquifer thermal energy storage (ATES) is one of the main types of geo-storage concepts aimed at an efficient energy supply and for achieving a low-carbon energy balance. In ATES, thermal energy is stored underground for later use; for instance, by intentionally injecting warm water - heated up by excess heat energy of industry and commerce - into the aquifer, and recovering it later for heating purposes, e.g., during the winter period. However, a significant number of ATES projects suffer from operational and maintenance issues or failures. Mineral precipitation (scaling) and flocculation, or microbial growth are major risks for ATES. By reducing the permeability in reservoirs, these processes threaten medium- to long-term operational reliability.  

The BMBF-funded research project ‘UnClog-ATES’ comprehensively investigates clogging and scaling in two typical reservoirs for ATES systems (siliciclastic sediments and carbonate-bearing sediments) which are widely distributed and exhibit different reactivity with respect to temperature and hydrochemical changes. Laboratory-scale flow-through column experiments as well as batch reactor experiments will be performed to simulate transport under representative ATES conditions (pressure, temperature, hydraulics, and chemical composition). Additionally, countermeasures (e.g., scaling inhibitors, acids, or CO₂) will be investigated to maximize the potential of ATES in the future. Finally, based on numerical reactive solute transport models, a catalog of criteria for users and decision-makers will be created to facilitate an initial site assessment in order to minimize the operational risk of ATES at this level.

How to cite: Arab, A., Gabler, L., Binder, M., Engelmann, C., Viehweger, C., and Scheytt, T.: Analyzing clogging and scaling processes in carbonate and siliciclastic ATES systems based on column and batch experiments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11413, https://doi.org/10.5194/egusphere-egu23-11413, 2023.

Over the past decade, there have been numerous attempts to use low-grade waste heat (30 oC and 100 oC) for a variety of different applications, especially district heating systems. However, the initial investment in waste heat recovery systems is usually high and the temperature is too low to meet the needs of the different end users. One possible solution is to integrate seasonal thermal energy storage with data centers or other industries that deals with waste heat. This is especially possible when considering borehole thermal energy storage (BTES), as it is highly adaptable, expandable and economical. However, almost all research and technical applications of BTES systems have focused on solar energy storage, with the exception of the projects in Emmaboda (Sweden) and Chifeng (China), where BTES systems have been used to store waste heat. In this paper, the results of a series of measurements on a BTES in Norway are presented and numerical simulations are performed to evaluate the long-term performance of the BTES once it is connected to a continuous supply of waste heat from a data center. The results obtained show how important a long-term prediction of the system performance is for planning and optimization. It was found that the storage temperature and heat recovery of the BTES are lower than expected when the quantity and quality of waste heat is overestimated. It seems that the borehole has the capacity to store  heat at a temperature of more than 75 C, but it may reduce its functionality over time and shorten its lifespan from 30 to 10 years.

How to cite: Gholami, R.: Thermal Energy Storage Integration with Waste Heat: What are the Challenges?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16904, https://doi.org/10.5194/egusphere-egu23-16904, 2023.

In central Europe, the majority of the CO₂ emissions in the energy sector are related to the provision of building and process heat. Due to seasonal fluctuations in demand, especially to provide heat for residential and industrial buildings, local storage of excess heat in summer for utilization in winter is becoming increasingly important. With the current state of technology and foreseeable developments, sufficient amounts of heat can only be stored underground, taking advantage of the large available storage volumes. In contrast to typical near-surface aquifer thermal energy storage (ATES), the utilization of deep reservoirs enables the storage of much larger thermal energies due to potentially significantly higher injection temperatures (e.g. > 80 °C).

Previous studies demonstrated the high potential of deep reservoirs for high-temperature (HT) ATES, in particular for former hydrocarbon reservoirs in the Upper Rhine Graben. However, these studies focused on thermo-hydraulic processes, only rarely considering the impact of coupled mechanical processes. Using the case study of the DeepStor project, a demonstrator for HT-ATES under development in the north of Karlsruhe (Germany), the present study investigates the influence of coupled thermo-hydraulic-mechanical (THM) processes during the operation of HT-ATES systems.

In particular, we investigate the impact of seasonal HT-ATES with biannual injection/production cycles on the stress distribution in the subsurface and subsequently caused displacements in the reservoir and the surface as well as the shear capacity at faults. This study further aims at improving the understanding of poro- and thermoelastic processes related to HT-ATES. Whereas the thermoelastic component dominates the vertical displacements at the top of the reservoir, the uplift at the surface is primarily controlled by the poroelastic component. Furthermore, an assessment of potential risks such as surface uplift or shear capacity at faults is performed. Our results show that surface uplift is primarily controlled by the reservoir depth, Young’s modulus, and the injection/production flow rate.

How to cite: Stricker, K., Egert, R., Fokker, P., Vardon, P. J., van Wees, J. D., Schill, E., and Kohl, T.: Risk assessment of high-temperature heat storage (HT-ATES) at the DeepStor demonstrator site, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12390, https://doi.org/10.5194/egusphere-egu23-12390, 2023.

The seasonal storage of heat has the potential to reduce greenhouse gas emissions, since it accounts for the seasonal disbalance between heat production and demand in renewable-based energy-systems. High temperature aquifer thermal energy storage (HT-ATES) is a heat storage technology utilising the subsurface and therefore provides high storage capacity with limited above-ground usage, which is especially required in urban areas. Since the temperature difference between the ambient groundwater and the injected water (> 50 °C) results in density differences, convective buoyancy flow can be induced by HT-ATES. This process leads to an uneven heat distribution over the aquifer thickness, reduced storage efficiency and increased thermal impacts. The occurrence and intensity of buoyancy flow is site-specific, since it depends on operational parameters, such as injection temperature, as well as geological parameters, such as aquifer thickness and especially vertical and horizontal permeability.

The geological site considered for HT-ATES storage is located in Hamburg, Germany, using the Miocene Lower Braunkohlensande (brown coal sands) as storage aquifer. This sedimentological formation was deposited in a coastal transition regime between terrestrial and shallow-marine settings and consists mainly of sands. Peat swamps and lagoons formed brown coal, silt and clay layers, which have the potential to hinder convection due to their low permeability, depending on their lateral extent in relation to the size of the induced heat plume by HT-ATES. Lithological classifications of 25 wells provide the data basis for the geological analysis.

The aim of this study is to evaluate the influence of thin low permeability layers on induced buoyancy flow and thus HT-ATES performance, as measured by heat recovery. To this end, a site-specific numerical HT-ATES model is created, which simulates the coupled thermo-hydraulic processes. Different scenarios with varied vertical permeability as well as the number and lateral extent of low-permeability layers show the effect on density-driven buoyancy flow and HT-ATES efficiency. Increasing the vertical permeability by a factor of 10 results in an efficiency decrease from 78 % to 57 % in the 10^th storage cycle. The findings serve as a process understanding basis for complex heterogeneous facies models of the HT-ATES site, which will be based on the geostatistical evaluation of site data.

How to cite: Heldt, S. and Bauer, S.: Evaluating the impact of anisotropy and low-permeability layers on high temperature aquifer thermal energy storage performance, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14087, https://doi.org/10.5194/egusphere-egu23-14087, 2023.

The current energy crisis since February 2022, have led governments to put in place short and long-term measures aimed at shielding consumers from the direct impact of the rising energy prices across Europe, and to counteract the continuous economic volatility. The pressure is high for finding solutions to reduce energy imports, and fight against climate change impacts. The numerous debates on climate change such as the COP27 are pushing for a greater acceleration in decarbonising the energy sector. Low carbon sources such as geothermal energy can substantially decrease energy consumptions and costs, especially if included into decarbonized heating and cooling grids (Chicco et al., 2022). The use of geothermal energy for thermal energy production and storage in district heating and cooling (DHC) grids may also be a key element in overcoming short-term energy peaks overcoming of the gap between energy supply and demand, which is still a challenge for the energy transition.  In this framework, underground thermal energy Storage (UTES) systems can be a key element for efficient operation of heating and cooling grids. Here, we present a study aimed at evaluating the performance of one of the most promising underground thermal energy storage systems, which uses boreholes to store heat or cold (BTES). Aimed at testifying the replicability of the used methodology, we replicated the same workflow already presented in Chicco and Mandrone (2022) but on a different area in northern Italy, with similar hydrogeological and thermo-physical characteristics. Based on real field data, the study focused on numerical simulations aimed at understanding how these technologies can be used as backup systems, or when the energy demand overcomes that supplied by conventional heating systems. Obtained results proved again how the integration of these technologies in DHC contexts can contribute to greater energy and economic savings, showing that BTES are very flexible to meet both the base and peak load requests for several users.

Chicco, J.M.; Antonijevic, D.; Bloemendal, M.; Cecinato, F.; Goetzl, G.; Hajto, M.; Hartog, N.; Mandrone, G.; Vacha, D.; Vardon, P.J. Improving the Efficiency of District Heating and Cooling Using a Geothermal Technology: Underground Thermal Energy Storage (UTES). In New Metropolitan Perspectives; Calabrò, F., Della Spina, L., Piñeira Mantiñán, M.J., Eds.; NMP 2022; Lecture Notes in Networks and Systems; Springer: Cham, Switzerland, 2022, 482, 1699–1710. https://doi.org/10.1007/978-3-031-06825-6_164

Chicco, J.M.; Mandrone, G. Modelling the Energy Production of a Borehole Thermal Energy Storage (BTES) System. Energies 2022, 15, 9587. https://doi.org/10.3390/en15249587

How to cite: Chicco, J. and Mandrone, G.: Borehole thermal energy storage (BTES) as backup systems in district heating and cooling contexts: results from numerical simulations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14917, https://doi.org/10.5194/egusphere-egu23-14917, 2023.

Decarbonising the heating and cooling sector is crucial for reducing our global CO₂ emissions. One promising option for environmental friendly energy supply in buildings is the use of shallow geothermal energy (SGE) (< 400 m depth) such as ground source heat pump (GSHP), groundwater heat pump (GWHP) and tunnel geothermal systems. In addition, renewable energy sources such as wind and solar are typically intermittent in nature, which is why they are characterized by an abundant but limited instantaneous availability. Peak time shaving and shifting by thermal energy storage are therefore considered as a key to the transition of the heating and cooling sector from fossil-based to zero-carbon. To balance these temporal variations in the availability and demand, Underground Thermal Energy Storage (UTES) systems could be used. In particular, Aquifer Thermal Energy Storage (ATES) systems are characterized by high storage capacities and low storage costs and is, therefore, drawing growing attention worldwide. However, only little is known about global application and distribution of ATES systems. Hence, this talk will provide an overview of the present and future potential of ATES systems including the chances and risks associated with such systems, which can play an important part in achieving our ambiguous climate targets.

How to cite: Blum, P., Menberg, K., Fleuchaus, P., Schüppler, S., Stemmle, R., Barth, F., and Bayer, P.: Chances and risks of aquifer thermal energy storage (ATES) systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9471, https://doi.org/10.5194/egusphere-egu23-9471, 2023.

Low temperature Aquifer Thermal Energy Storage (ATES) is increasingly used for space heating and cooling. Though these systems emit 3-4 times less CO₂ compared to gas heating, they still require a substantial amount of electricity, mostly because of the heat pump (~60%). Storing higher temperatures (HT) to be used for direct heating can be a solution to circumvent the use of a heat pump, however the return temperature after heating is not usually cold enough to use directly for cooling. The first HT ATES systems that are implemented have either no cooling, or alternative means for cooling. With better insulated buildings, that require both heating and cooling, as well as an increased pressure on the electricity grid, an autarkic system is needed that can supply both heating and cooling. The ATES Triplet system aims to do just that.

Similar to and HT ATES system, the ATES Triplet stores hot water at supply temperature needed for space heating in a hot well. Unlike the HT-ATES system, it also aims to store water at the supply temperature for cooling in a cold well. This heat and cold can be harvested by solar collectors and dry coolers (or other green heat/cold sources locally available). After the water extracted from the wells is used to heat/cool the building, the solar collectors and dry coolers can be used to store water at the right temperatures. However, the availability of these sources can be insufficient to reach the required temperatures. A third well is added that functions as a buffer. Water used for heating or cooling can be stored here until there is enough heating/cooling capacity available from the solar collectors and dry coolers to upgrade the water to the required temperature, and store in the hot or cold well. Furthermore, the solar collectors and dry coolers can also be used for direct space heating and cooling, making the entire system and autarkic heating and cooling system.

Initial simulations show a substantial reduction to operational CO₂ emissions compared to conventional heating systems. Though a higher initial investment is required, systems also show an increased economic performance over conventional ATES systems and gas heating. Further research will investigate the effect of subsurface conditions, system layout and other operational conditions on the economic and environmental performance of the system.

How to cite: van Esch, M. S., Bloemendal, M., Hartog, N., and Vardon, P. J.: The reduction of heating and cooling CO2 emissions with the ATES triplet, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15738, https://doi.org/10.5194/egusphere-egu23-15738, 2023.

Accurate prediction of heat transport in porous media is important for understanding geoscience processes and properties and to design applications, for example geothermal energy systems. While heat transport is generally modelled assuming of local thermal equilibrium (LTE), i.e., instantaneous heat transfer between the fluid and solid phases, previous studies have demonstrated presence of local thermal non-equilibrium (LTNE), i.e., delayed heat transfer, in natural porous materials. However, factors that influence the rate of heat transfer between the phases and their significance for inherently heterogeneous natural systems remain unknown and untested. We develop an open-source fully coupled, finite-element application to numerically simulate heat transfer between the fluid and solid phases. This is based on the Multiphysics Object-Oriented Simulation Environment (MOOSE) and allows massively parallel modelling of heat transport including customized transfer rates. We verify our model using an analytical solution considering LTNE and illustrate several applications. The model can be used to investigate processes that affect heat transport such as heat transfer mechanisms and their dependence on different hydrogeological conditions.

How to cite: Lee, H., Wilkins, A., Blum, P., Bayer, P., and Rau, G.: Fully coupled heat transport modelling in porous media considering transfer between phases, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8618, https://doi.org/10.5194/egusphere-egu23-8618, 2023.