Based on a newly developed geological 3D reservoir model for the demonstration site of the 'Freib... more Based on a newly developed geological 3D reservoir model for the demonstration site of the 'Freiburger Bucht' in the Upper Rhine Graben (SW Germany), geothermal development and realization concepts of an aquifer thermal energy storage (ATES) in the Buntsandstein aquifer were elaborated and energetically evaluated by numerical modeling. The thermal-hydraulic coupled modeling was performed with the FE-software OpenGeoSys and COMSOL. For this purpose, the geological model was converted into a numerical model and calibrated by local and regional, hydrogeological and geothermal measured values. A detailed study based on two-phase storage-heating cycles per year with constant injection temperature on the 'hot side' of the ATES, different volumetric flow rates, and temperature spreads was performed to quantify possible storage capacities, energies, and efficiencies. The calculated efficiency of the cyclic storage operation in this study, averaged over 10 storage heating cycles, are between 50 and 85%, depending on flow rate and temperature spread. The efficiency of the individual storage heating cycles increases from year to year in all scenarios considered, as the 'hot side' of the storage heats up in the long term. To increase ATES' efficiency, also horizontal wells were integrated into the numerical model and the results were compared with those of inclined wells.
Due to an increased heat flow and the presence of several aquifers, the Upper Rhine Graben (URG) ... more Due to an increased heat flow and the presence of several aquifers, the Upper Rhine Graben (URG) offers favorable conditions for geothermal utilization and several geothermal projects have emerged in the last decade. Previous research in this tectonic setting proved that the hydraulic and geomechanical behavior of the geothermal reservoirs is mainly governed by the existence of mesoscale fractures and deep large-scale fault systems. The occurrence of induced seismicity as a result of fluid injection, however, clearly demonstrates that a better understanding on their role is still required.
Background The determination of the subsurface conditions and reservoir properties is indispensab... more Background The determination of the subsurface conditions and reservoir properties is indispensable for exploration and exploitation of a geothermal field. It includes the expected geological structures as well as the hydraulic, thermal, chemical and mechanical parameters of the target horizon which should be favorable for geothermal utilization. Most essential is a high permeability to supply sufficient flow rates and high temperatures (Stober and Bucher 2012). An area in Germany which fulfills the criteria is the Upper Rhine Graben with a unique geothermal potential (Agemar et al. 2014). Local temperature anomalies with elevated temperatures up to 165 °C are expected at a depth of 2500 m, while the average geothermal gradient of the URG is above 40K km −1 (Agemar et al. 2013). Especially the sedimentary formation of the Triassic, Buntsandstein and Muschelkalk shows high permeabilities, which are necessary to provide high flow rates (Stober and Bucher 2014).
The reaction path in the (Ba, Sr, Ca)SO 4 solid-solution aqueous-solution (SSAS) system was exper... more The reaction path in the (Ba, Sr, Ca)SO 4 solid-solution aqueous-solution (SSAS) system was experimentally studied using a batch-reactor method. The effect of the impurities "fluorite" and "iron sulfides" admixed in a natural barite sample on the reaction path was followed by analyzing the aqueous solution continuously. The dissolution and precipitation of the impurity "fluorite" affected strongly the reaction path in the SSAS system, especially the Ca/Sr/Ba ratio in the aqueous solution. This influence became stronger with decreasing CaSO 4 in the solid solution. The dissolution and precipitation of fluorite could hinder the CaSQ component from dissolving into water, and reduce the release rate of SO~-from the solid solution to the aqueous solution and the removing rate of Ba 2 ÷ from the aqueous solution. In the presence of fluorite and sulfides, the aqueous Ba 2 + and Sr 2 + concentrations were controlled by the dissolution-precipitation of the end-members BaSO 4 and SrSO 4 , respectively ; the aqueous F-, Ca ~ ~ and SO~-concentrations were controlled by the dissolution-precipitation of fluorite. The incongruent dissolution of the (Ba, Sr, Ca) SO4 solid solution caused the solid phase to become progressively more enriched in the more insoluble component (BaSO 4), while the aqueous composition shifted towards the more soluble end-members (Sr-SO 4 and CaSO n) as equilibrium was approached to.
In physics, energy is the ability of a physical system to do work on other physical systems. Ther... more In physics, energy is the ability of a physical system to do work on other physical systems. There are many different forms of energy including mechanical (potential, kinetic), thermal, electric, chemical and nuclear energy. Thermal energy can be understood as the random motion of atoms and molecules.
Renewable & Sustainable Energy Reviews, Oct 1, 2018
To meet the global climate change mitigation targets, more attention has to be paid to the decarb... more To meet the global climate change mitigation targets, more attention has to be paid to the decarbonization of the heating and cooling sector. Aquifer Thermal Energy Storage (ATES) is considered to bridge the gap between periods of highest energy demand and highest energy supply. The objective of this study therefore is to review the global application status of ATES underpinned by operational statistics from existing projects. ATES is particularly suited to provide heating and cooling for large-scale applications such as public and commercial buildings, district heating, or industrial purposes. Compared to conventional technologies, ATES systems achieve energy savings between 40% and 70% and CO 2 savings of up to several thousand tons per year. Capital costs decline with increasing installed capacity, averaging 0.2 Mio. € for small systems and 2 Mio. € for large applications. The typical payback time is 2-10 years. Worldwide, there are currently more than 2800 ATES systems in operation, abstracting more than 2.5 TWh of heating and cooling per year. 99% are low-temperature systems (LT-ATES) with storage temperatures of < 25°C. 85% of all systems are located in the Netherlands, and a further 10% are found in Sweden, Denmark, and Belgium. However, there is an increasing interest in ATES technology in several countries such as Great Britain, Germany, Japan, Turkey, and China. The great discrepancy in global ATES development is attributed to several market barriers that impede market penetration. Such barriers are of socioeconomic and legislative nature.
Based on a newly developed geological 3D reservoir model for the demonstration site of the 'Freib... more Based on a newly developed geological 3D reservoir model for the demonstration site of the 'Freiburger Bucht' in the Upper Rhine Graben (SW Germany), geothermal development and realization concepts of an aquifer thermal energy storage (ATES) in the Buntsandstein aquifer were elaborated and energetically evaluated by numerical modeling. The thermal-hydraulic coupled modeling was performed with the FE-software OpenGeoSys and COMSOL. For this purpose, the geological model was converted into a numerical model and calibrated by local and regional, hydrogeological and geothermal measured values. A detailed study based on two-phase storage-heating cycles per year with constant injection temperature on the 'hot side' of the ATES, different volumetric flow rates, and temperature spreads was performed to quantify possible storage capacities, energies, and efficiencies. The calculated efficiency of the cyclic storage operation in this study, averaged over 10 storage heating cycles, are between 50 and 85%, depending on flow rate and temperature spread. The efficiency of the individual storage heating cycles increases from year to year in all scenarios considered, as the 'hot side' of the storage heats up in the long term. To increase ATES' efficiency, also horizontal wells were integrated into the numerical model and the results were compared with those of inclined wells.
Due to an increased heat flow and the presence of several aquifers, the Upper Rhine Graben (URG) ... more Due to an increased heat flow and the presence of several aquifers, the Upper Rhine Graben (URG) offers favorable conditions for geothermal utilization and several geothermal projects have emerged in the last decade. Previous research in this tectonic setting proved that the hydraulic and geomechanical behavior of the geothermal reservoirs is mainly governed by the existence of mesoscale fractures and deep large-scale fault systems. The occurrence of induced seismicity as a result of fluid injection, however, clearly demonstrates that a better understanding on their role is still required.
Background The determination of the subsurface conditions and reservoir properties is indispensab... more Background The determination of the subsurface conditions and reservoir properties is indispensable for exploration and exploitation of a geothermal field. It includes the expected geological structures as well as the hydraulic, thermal, chemical and mechanical parameters of the target horizon which should be favorable for geothermal utilization. Most essential is a high permeability to supply sufficient flow rates and high temperatures (Stober and Bucher 2012). An area in Germany which fulfills the criteria is the Upper Rhine Graben with a unique geothermal potential (Agemar et al. 2014). Local temperature anomalies with elevated temperatures up to 165 °C are expected at a depth of 2500 m, while the average geothermal gradient of the URG is above 40K km −1 (Agemar et al. 2013). Especially the sedimentary formation of the Triassic, Buntsandstein and Muschelkalk shows high permeabilities, which are necessary to provide high flow rates (Stober and Bucher 2014).
The reaction path in the (Ba, Sr, Ca)SO 4 solid-solution aqueous-solution (SSAS) system was exper... more The reaction path in the (Ba, Sr, Ca)SO 4 solid-solution aqueous-solution (SSAS) system was experimentally studied using a batch-reactor method. The effect of the impurities "fluorite" and "iron sulfides" admixed in a natural barite sample on the reaction path was followed by analyzing the aqueous solution continuously. The dissolution and precipitation of the impurity "fluorite" affected strongly the reaction path in the SSAS system, especially the Ca/Sr/Ba ratio in the aqueous solution. This influence became stronger with decreasing CaSO 4 in the solid solution. The dissolution and precipitation of fluorite could hinder the CaSQ component from dissolving into water, and reduce the release rate of SO~-from the solid solution to the aqueous solution and the removing rate of Ba 2 ÷ from the aqueous solution. In the presence of fluorite and sulfides, the aqueous Ba 2 + and Sr 2 + concentrations were controlled by the dissolution-precipitation of the end-members BaSO 4 and SrSO 4 , respectively ; the aqueous F-, Ca ~ ~ and SO~-concentrations were controlled by the dissolution-precipitation of fluorite. The incongruent dissolution of the (Ba, Sr, Ca) SO4 solid solution caused the solid phase to become progressively more enriched in the more insoluble component (BaSO 4), while the aqueous composition shifted towards the more soluble end-members (Sr-SO 4 and CaSO n) as equilibrium was approached to.
In physics, energy is the ability of a physical system to do work on other physical systems. Ther... more In physics, energy is the ability of a physical system to do work on other physical systems. There are many different forms of energy including mechanical (potential, kinetic), thermal, electric, chemical and nuclear energy. Thermal energy can be understood as the random motion of atoms and molecules.
Renewable & Sustainable Energy Reviews, Oct 1, 2018
To meet the global climate change mitigation targets, more attention has to be paid to the decarb... more To meet the global climate change mitigation targets, more attention has to be paid to the decarbonization of the heating and cooling sector. Aquifer Thermal Energy Storage (ATES) is considered to bridge the gap between periods of highest energy demand and highest energy supply. The objective of this study therefore is to review the global application status of ATES underpinned by operational statistics from existing projects. ATES is particularly suited to provide heating and cooling for large-scale applications such as public and commercial buildings, district heating, or industrial purposes. Compared to conventional technologies, ATES systems achieve energy savings between 40% and 70% and CO 2 savings of up to several thousand tons per year. Capital costs decline with increasing installed capacity, averaging 0.2 Mio. € for small systems and 2 Mio. € for large applications. The typical payback time is 2-10 years. Worldwide, there are currently more than 2800 ATES systems in operation, abstracting more than 2.5 TWh of heating and cooling per year. 99% are low-temperature systems (LT-ATES) with storage temperatures of < 25°C. 85% of all systems are located in the Netherlands, and a further 10% are found in Sweden, Denmark, and Belgium. However, there is an increasing interest in ATES technology in several countries such as Great Britain, Germany, Japan, Turkey, and China. The great discrepancy in global ATES development is attributed to several market barriers that impede market penetration. Such barriers are of socioeconomic and legislative nature.
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