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Recovery efficiency in high-temperature aquifer thermal energy storage systems
Abstract
Aquifer Thermal Energy Storage (ATES) uses excess thermal energy to heat water which is stored in an aquifer until it is needed, at which time the hot water is recovered and the heat used for some purpose e.g. electricity generation. The recovery efficiency (i.e. the ratio of heat energy recovered to heat energy injected, R) is one of the most important factors dictating the viability of ATES systems.
The variation of R with various aquifer properties and operating parameters is explored for high temperature (HT) ATES systems with injection temperatures ≥90∘C, extending the results of previous studies to higher temperatures and a broader range of aquifer properties and operating conditions. R values are calculated using numerical models of a single-well ATES system, which is validated by comparison with previous field and modelling studies.
The results show that HT-ATES may be viable with injection temperatures as high as 300 ∘C, depending on the aquifer properties and operating parameters. Daily cycles are very efficient over a broad range of conditions, whereas the efficiency of annual cycles is much more variable. The most important parameters governing R are aquifer thickness, injection temperature, horizontal and vertical permeability, and dispersion length.
The R values are used to derive an improved version of the Rayleigh number relationship proposed by Schout et al. (2014), extending the applicability of this relationship to daily cycles and improving its accuracy for annual cycles. An alternative method for estimating R using a convolutional neural network is proposed.
The calculated R values may be considered best-case because aspects such as background groundwater flow and geochemical effects are ignored. Practical factors such as energy supply/demand requirements, reservoir and above-ground engineering, financial or regulatory aspects, and public acceptance are not considered. Nevertheless, the results of this study can be used for rapid screening of large areas for potential HT-ATES sites, defining requirements for potential sites, and estimating R values for specific sites, before performing detailed feasibility studies.
... Based on these cases an equation was created that used the modified Rayleigh number and Fig. 1 Operation modes of ATES system, extracted from Bloemendal and Hartog (2018), left heating of the ATES system, right cooling of the ATES system, providing heat to buildings which captures the relation between the model input parameters and η r . This temperature range was later extended to 90-300 °C by Sheldon et al. (2021). They focused on a larger amount of cases and proposed an equation for calculating η r based on the same modified Rayleigh number. ...
... By extending the number and range of parameter values, new insights are gained into more subtle effects not encountered in the previous study. This study also differs from the research done by Sheldon et al Sheldon et al. (2021). The used injection temperatures in this research are lower (25-80 • C instead of 90-300 • C), leading to less pronounced buoyancy flow. ...
... MT3DMS automatically reduces time step to meet this condition, which is sufficiently small to capture important processes around the well Bloemendal and Hartog (2018); Duijff et al. (2023). The simulation period was eight years, after which the operation and η r of the HT-ATES stabilized Beernink et al. (2024); Sheldon et al. (2021). Other parameters used in MODFLOW can be found in Table 1. ...
High-Temperature Aquifer Thermal Energy Storage (HT-ATES) can be used to reduce greenhouse gas emissions from heating. The thermal recovery efficiency is the main parameter indicating the performance of an HT-ATES system and it is influenced by multiple aquifer properties and storage characteristics. This study presents a method for estimating recovery efficiency through numerical modeling, data analysis, and curve fitting. This method shows the relation between the recovery efficiency and various storage conditions, such as aquifer properties and storage temperature. In addition, this research explores an analytical relationship between energetic efficiency and recovery efficiency and verifies that relationship with the generated data. The proposed method can be used for the purpose of initial screening to estimate the performance of an HT-ATES system and for efficiently using HT-ATES as a component in larger energy system models. This method uses the modified Rayleigh number in combination with aquifer thickness and injected volume and has a R 2 of 85%. The analytical relation between energetic efficiency and recovery efficiency was shown to be accurate for all calculated energetic efficiency values above 60% and is less accurate with lower calculated energetic efficiency values.
... Each period lasts a different amount of time, depending on system properties, climate conditions, demand, and others [19]. Thermal recovery efficiency increases for each successive cycle ( Figure 5), but the rate of increase decreases over time so that thermal recovery efficiency for the fifth cycle can be considered representative of the long-term behavior of the system [20]. . Schematic storage geometry variation of the thermal volume stored around an ATES well during one ATES cycle. ...
... Thermal recovery efficiency increases for each successive cycle ( Figure 5), but the rate of increase decreases over time so that thermal recovery efficiency for the fifth cycle can be considered representative of the long-term behavior of the system [20]. Thermal recovery efficiency increases for each successive cycle ( Figure 5), but of increase decreases over time so that thermal recovery efficiency for the fifth c be considered representative of the long-term behavior of the system [20]. ...
... Thermal recovery efficiency increases for each successive cycle ( Figure 5), but the rate of increase decreases over time so that thermal recovery efficiency for the fifth cycle can be considered representative of the long-term behavior of the system [20]. Thermal recovery efficiency increases for each successive cycle ( Figure 5), but of increase decreases over time so that thermal recovery efficiency for the fifth c be considered representative of the long-term behavior of the system [20]. ...
Since the heating and cooling sectors consume most of the energy in Europe through fossil fuels, the transition to a low-carbon and sustainable energy system is crucial. Underground Thermal Energy Storage (UTES) systems, such as aquifer thermal energy storage (ATES) and borehole thermal energy storage (BTES), offer promising solutions by enabling seasonal storage of renewable thermal energy, balancing the mismatch between supply and demand. ATES and BTES systems store excess heat or cold for later use, making them suitable for large-scale applications like residual heat storage from industrial or power generation processes by offering flexibility in heating and cooling. This review explores the geological and hydrogeological requirements for ATES and BTES systems, pointing out the importance of basic geological knowledge, laboratory and field investigations, and operational monitoring to optimize their performance. The study highlights the need for Slovenia to use the experiences of other European nations to overcome initial challenges, develop effective site evaluation methods, and integrate these systems into existing energy infrastructure.
... Around 3000 LT-ATES projects have successfully been implemented worldwide (Fleuchaus et al., 2018). In contrast, few HT-ATES projects have been developed, and numerous pilot HT-ATES plants are currently under development (McLing et al., 2022;Sheldon et al., 2021). The main challenges that impede the application of HT-ATES include factors such as (a) clogging due to particles and precipitation of minerals in the heat exchangers, wells, and aquifers (Holmslykke & Kjøller, 2023), (b) corrosion of ATES components and damage to the aquifer (Schout et al., 2014), (c) significant heat losses during transport in boreholes and aquifers, etcetera (Drijver, 2011). ...
... For HT-ATES, heat loss may result from not only the diffusive heat transport, driven by the gradient in temperature or the mechanical dispersion (Tang & Van Der Zee, 2022) but also by thermal stratification (Sheldon et al., 2021). The injected hot water tends to flow above the ambient water due to the lower density, namely buoyancy flow (Heldt et al., 2021). ...
... In this case, they proposed a modified Rayleigh number, which can correlate well with the recovery efficiency for all the simulated cases with two equations for different aquifer thicknesses. Sheldon et al. (2021) further extended the work of Schout et al. (2014), and they provided an improved version of the recovery efficiency-Rayleigh number relationship valid for HT-ATES operating at both annual circles and short-term cycles (e.g., daily cycles) and storage temperatures of up to 300°C. Nevertheless, the injection and production processes during HT-ATES involve both free convection due to density contrasts and forced convection due to the pumping at the well, namely mixed convection (Ward et al., 2007). ...
With their high storage capacity and energy efficiency as well as the compatibilities with renewable energy sources, high‐temperature aquifer thermal energy storage (HT‐ATES) systems are frequently the target today in the design of temporally and spatially balanced and continuous energy supply systems. The inherent density‐driven buoyancy flow is of greater importance with HT‐ATES, which may lead to a lower thermal recovery efficiency than conventional low‐temperature ATES. In this study, the governing equations for HT‐ATES considering buoyancy flow are nondimensionalized, and four key dimensionless parameters regarding thermal recovery efficiency are determined. Then, using numerical simulations, recovery efficiency for a sweep of the key dimensionless parameters for multiple cycles and storage volumes is examined. Ranges of the key dimensionless parameters for the three displacement regimes, that is, a buoyancy‐dominated regime, a conduction‐dominated regime, and a transition regime, are identified. 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, recovery efficiency is mainly correlated to the product of a material‐related parameter and the Peclet number. Multivariable regression functions are provided to estimate recovery efficiency using the dimensionless parameters. The recovery efficiency estimated by the regression function shows good agreement with the simulation results. Additionally, well screen designs for optimizing recovery efficiency at various degrees of intensity of buoyancy flow are investigated. The findings of this study can be used for a quick assessment and characterization of the potential HT‐ATES systems based on the geological and operational parameters.
... For example, Zeghici et al. (2015) simulated a hypothetical mono-well HT-ATES system and assumed loading for 180 days and unloading for 185 days, both with constant flow rates. Sheldon et al. (2021) also assumed constant flow rates for the 91-day long phases of loading, storage, unloading and standstill. Collignon et al. (2020) assumed constant annual flow rates as well with equal loading and unloading phases of four months separated by two months of rest for the annual cycle and Jin et al. (2022) also assumed constant flow rates in their simulations, which were used to train an machine-learning algorithm with the aim of HT-ATES storage optimization regarding multiple performance metrics. ...
... The relative potential of buoyant flow, which is a key process for HT-ATES, depends on the injection temperature, vertical permeability, aquifer thickness, and thermal parameters and may be assessed through Rayleigh number analysis (Krol et al., 2014). Schout et al. (2014) presented a correlation between a modified Rayleigh number and HT-ATES η, while Sheldon et al. (2021) extended this work to a wider range of hydrogeological and operational conditions. Although this approach overlooks the impact of ambient groundwater flow, it is nonetheless a useful tool for the first HT-ATES η estimation. ...
... Section 3.3 Initial and boundary conditions). This approach reduces heat loss compared to pumping schemes with equal injection and extraction volumes, as is frequently assumed in HT-ATES modeling (Schout et al., 2014;Sheldon et al., 2021). A reference scenario with equal extraction and injection volumes accordingly showed lower ηs of 52 and 79 % in the first and 26th years, respectively. ...
... Previous studies showed that conduction and dispersion are important for low temperature wells (Bloemendal and Hartog, 2018;Doughty et al., 1982) and that at high storage temperatures relative to the ambient groundwater temperature, buoyancy-driven flow can considerably impact the performance (Buscheck et al., 1983;van Lopik et al., 2016). Recently, methods have been developed that assess the ratio of conduction versus buoyancy-driven flow and empirically estimate the thermal recovery efficiency of ATES wells at high storage temperature (Schout et al., 2014;Sheldon et al., 2021). Although these studies show that ATES performance is more variable at higher storage temperatures, their use for a wide range of storage temperatures and storage conditions is uncertain. ...
... Logically, when relatively large values of longitudinal dispersion lengths are used in simulations studies, dispersion has a strong impact. With α l = 5 in this study, α l = 10 m in Sheldon et al. (2021) or even up to α l = 100 m in Gao et al. (2019)), dispersion losses are equal or sometimes even larger than the losses due to conduction. Large values of α l are indeed reported in literature (Gelhar et al., 1992;Zech et al., 2022) for the length-scale of realistic thermal radii (Sheldon et al., 2021) for ATES systems (R th = 50 -150 m). ...
... With α l = 5 in this study, α l = 10 m in Sheldon et al. (2021) or even up to α l = 100 m in Gao et al. (2019)), dispersion losses are equal or sometimes even larger than the losses due to conduction. Large values of α l are indeed reported in literature (Gelhar et al., 1992;Zech et al., 2022) for the length-scale of realistic thermal radii (Sheldon et al., 2021) for ATES systems (R th = 50 -150 m). However, large values of α l like these seem to overestimate the actual effect of additional mixing due to macrodispersion for ATES systems (Sommer et al., 2013). ...
The technical and economic success of an Aquifer Thermal Energy Storage (ATES) system depends strongly on its thermal recovery efficiency, i.e. the ratio of the amount of energy that is recovered to the energy that was injected. Typically, conduction most strongly determines the thermal recovery efficiency of ATES systems at low storage temperatures (<25 °C), while the impact of buoyancy-driven flow can lead to high additional heat losses at high storage temperatures (>50 °C). To date, however, it is unclear how the relative contribution of these processes and mechanical dispersion to heat losses across a broad temperature range is affected by their interaction for the wide range of storage conditions that can be encountered in practice. Since such process-based insights are important to predict ATES performance and support the design phase, numerical thermo-hydraulic ATES simulations were conducted for a wide range of realistic operational storage conditions ([15-90 °C], [50,000-1,000,000 m 3 /year]) and hydrogeological conditions (aquifer thickness, horizontal hydraulic conductivity, anisotropy). The simulated heat loss fractions of all scenarios were evaluated with respect to analytical solutions to assess the contribution of the individual heat loss processes. Results show that the wide range of heat losses (10-80 % in the 5th year) is the result of varying contributions of conduction, dispersion and buoyancy-driven flow, which are largely determined by the geometry of the storage volume (ratio of screen length / thermal radius, L/R th) and the potential for buoyancy-driven flow (q0) as affected by the storage temperature and hydraulic conductivity of the aquifer. For ATES systems where conduction dominates the heat losses, a L/Rth ratio of 2 minimizes the thermal area over volume ratio (A/V) and resulting heat losses for a given storage volume. In contrast however, the impact of dispersion decreases with L/R th and particularly for ATES systems with a high potential for buoyancy-driven flow (q0 > 0.05 m/d), increasingly smaller L/R th ratios (<1) strongly reduce the heat losses due to tilting. Overall, the results of this study support the assessment of thermal recovery efficiencies for particular aquifer and storage conditions, thereby aiding the optimization of initial ATES designs.
... Since only reactions within one meter from the injection well were modelled, the temperature gradient in the reservoir following injection of heated formation water was assumed negligible [46][47][48]. All reactions were assumed to occur in the reservoir, and thus potential scaling in the heat storage facility prior to reinjection into the reservoir was not included in the model. ...
... The "initial" amount of minerals in the reservoir was, however, changed to the amount present after injection for six months at the first injection cycle. The reservoir temperature prior to the second injection was assumed equal to the average production temperature, T p , expressed by Sheldon et al. [48]: ...
... where R is the recovery efficiency, T i the injection temperature, and T amb the ambient reservoir temperature. The recovery efficiency was set to R = 0.5 prior to the second injection [48]. Using this equation, the "new" reservoir temperature is 85 • C prior to the second injection. ...
... 2 of 28 and free convection driven by density gradients between the warm and cold groundwater (Sheldon et al., 2021). Most studies on the thermal recovery efficiency of ATES invoke numerical modeling to capture these relevant processes, but such models require detailed data on (heterogeneous) aquifer composition and properties, and water injection and extraction rate timeseries, which may be unavailable or very costly to obtain from field characterization, while also requiring intensive model construction and simulation time. ...
... In Sheldon et al. (2021), Equation 26 (following Doughty et al.'s (1982) empirical observations) was applied to model mechanical dispersion in two scenarios with different relative storage durations: one with T in = T ex = T st , and another with T in = T ex = 2T st . However, Doughty et al. (1982) performed numerical simulations to fit Equation 26 only for the case of T in = T ex = T st . ...
... Also, Δγ is equal to the temperature difference between injected and native groundwater multiplied by α f , the coefficient of thermal expansion of water. Schout et al. (2014) and Sheldon et al. (2021) showed that this empirical equation is flexible: it is valid to describe the recovery efficiency after multiple operational cycles, that also include storage and rest periods. In the context of our study, this implies that ...
Seasonal warm and cold water storage in groundwater aquifers is a cost‐effective renewable energy technology for indoor heating and cooling. Simple dimensionless analytical solutions for the thermal recovery efficiency of Aquifer Thermal Energy Storage (ATES) systems are derived, subject to heat losses caused by thermal diffusion and mechanical dispersion. The analytical solutions pertain to transient pumping rates and storage durations, and multiple cycles of operation, and are applicable to various well configurations and thermal plume geometries. Heat losses to confining layers, its implications for optimizing plume geometries and aspect ratios, and heat spreading due to free convection are also discussed. This provides a general tool for broad and rapid assessment of aquifers and ATES systems. We show that if heat exchange with the confining layers is negligible, the thermal recovery efficiency of thermal plumes with cylindrical geometry is independent of the aquifer porosity and heat capacity C0. Therefore, if mechanical dispersion is negligible as is often the case, the only aquifer property that affects the recovery efficiency is the aquifer thermal conductivity. The field‐scale aquifer thermal conductivity λ can therefore be inferred from the recovery efficiency of a push‐pull heat recovery test. Remarkably, an increase in C0 could either increase, decrease, or not affect the recovery efficiency, depending on the thermal plume geometry. Hence, the analytical solutions reveal that the recovery efficiency is affected by complex interactions between the thermal plume geometry and aquifer properties. Approximate analytical solutions for subsurface temperature profiles over an entire ATES cycle are also derived.
... For HT-ATES systems, the occurrence of free thermal convection (buoyancy-driven flow) can be an important intrinsic process negatively affecting thermal recovery efficiencies (Schout et al., 2014;Van Lopik et al., 2016;Sheldon et al., 2021). This is in addition to the heat losses that also occur in LT-ATES systems due to thermal conduction and displacement by ambient groundwater flow (Doughty et al., 1982;Bloemendal and Hartog, 2018). ...
... In confined aquifers, these buoyancy-induced heat losses result from the tilting of thermal front due to the density difference between the hot injection water and cooler ambient groundwater (Hellström et al., 1979;Schout et al., 2014). In particular for smaller HT-ATES systems where the thermal front tilting occurs close to the HT-ATES well, as well as for systems where the free thermal convective component will be large, such as in more permeable aquifers and at larger temperature differences, the impact on the thermal recovery efficiency is significant (e.g., Molz et al., 1983a, b;Buscheck et al., 1983;Schout et al., 2014;Van Lopik et al., 2016, Sheldon et al., 2021. Depending on the system requirements and the hydrogeological characteristics of the subsurface, shortening of the storage time, a storage volume increase or an available, thinner storage aquifer might be considered for some cases to reduce the impact of thermal front tilting on the thermal recovery efficiency (Schout et al., 2014;Sheldon et al., 2021). ...
... In particular for smaller HT-ATES systems where the thermal front tilting occurs close to the HT-ATES well, as well as for systems where the free thermal convective component will be large, such as in more permeable aquifers and at larger temperature differences, the impact on the thermal recovery efficiency is significant (e.g., Molz et al., 1983a, b;Buscheck et al., 1983;Schout et al., 2014;Van Lopik et al., 2016, Sheldon et al., 2021. Depending on the system requirements and the hydrogeological characteristics of the subsurface, shortening of the storage time, a storage volume increase or an available, thinner storage aquifer might be considered for some cases to reduce the impact of thermal front tilting on the thermal recovery efficiency (Schout et al., 2014;Sheldon et al., 2021). Also the selection of a less (vertically) permeable storage aquifer or a smaller difference between storage and ambient groundwater temperatures might be considered, (e.g. ...
The occurrence of free thermal convection negatively affects thermal recovery efficiencies of High-Temperature Aquifer Thermal Energy Storage (HT-ATES) systems. In this study the potential of applying a Multiple Partially Penetrating Well (MPPW) configuration to counteract the impact for seasonal HT-ATES is tested through numerical modeling with SEAWATv4. For scenarios where the thermal front is close to the HT-ATES well-screen and free thermal convection has considerable effect on the thermal recovery efficiency, the use of a MPPW configuration has great potential. Storage at a moderate temperature contrast (ΔT = 40 °C) between the hot injection volume and cold ambient groundwater in a high-permeability aquifer resulted in significant improvement of the thermal recovery efficiency with a MPPW configuration targeting injection in lower parts of the aquifer and recovery in the upper parts. For conventional, fully screened HT-ATES a thermal recovery efficiency of 0.43 is obtained while this is 0.59 with the MPPW scheme in the first recovery cycle. This recovery efficiency of 0.59 is only 0.11 less than a theoretical case with no buoyancy effects. For seasonal HT-ATES cases that face severe free thermal convection, rapid accumulation of heat in the upper part of the aquifer is observed and the MPPW configuration is less effective due to the long period between injection and recovery. Especially for HT-ATES cases that require a cut-off temperature, thermal recovery can be significantly improved and prolonged. For storage temperatures of 60 and 80 °C in a high-permeability aquifer, approximately 4 times more abstracted usable heat is obtained with the MPPW setup while considering a cut-off temperature of 40 °C. Moreover, the present study shows that the use of MPPW configurations in heterogeneous aquifers should be carefully planned. Improper application of MPPW is particularly vulnerable for simplification of the aquifer characteristics, and therefore proper site heterogeneity investigation and operational monitoring are required to benefit from optimal MPPW operation during HT-ATES.
... Among them, Doughty et al. (1982) first introduced a dimensionless factorenergy recovery efficiencyto quantify the thermal performance of a 2D ATES reservoir, defined as the ratio of extracted energy to the injected energy. Using numerical simulation, Sheldon et al. (2021) found that the aquifer thickness and permeability, injection fluid temperature as well as thermal dispersion length dominate the energy recovery efficiency in a single-well 2D ATES system. Sommer et al. (2013) demonstrated that short preferential pathways, short-circuiting and well interference in a heterogeneous 3D doublet ATES system result in the non-full utilization of the aquifer storage capacity and can cause 6 %~15 % lower energy recovery efficiency compared to the homogeneous case, which highlighted the importance of aquifer heterogeneity in the design and optimization of ATES system. ...
... We perform five cycles in this study, taking a total time of five years. The operational time for injecting and producing hot fluid can be influenced by factors such as local climate conditions, heating demand, etc. (Sheldon et al., 2021;Beernink et al., 2024). The nine months for heat storage and three months for heat extraction are chosen just for demonstration purposes. ...
... In this study, therefore, we investigate the effects of parameters, for which well-established hydrogeological measuring techniques exist, which are the horizontal and vertical hydraulic conductivities, specific storage, groundwater flow velocity, thermal conductivity and volumetric heat capacity. Numerical studies on HT-ATES so far have shown that of these parameters, thermal efficiency of an ATES is most dependent on vertical and horizontal hydraulic conductivity, but also depends on groundwater flow velocity, thermal conductivity and volumetric heat capacity (Gao et al. 2019;Jeon et al. 2015;Schout et al. 2014;Sheldon et al. 2021). ...
... In accordance with the present study, Gao et al. (2019) (injection temperature of 50 °C) and Jeon et al. (2015) (90 °C) identified k f h as having the highest impact on the thermal behavior, for which they used the recovery efficiency as a measure. Schout et al. (2014) (90 °C) and Sheldon et al. (2021) (up to 300 °C) found the recovery efficiency of HT-ATES to be most sensitive on k f h and k f v within the parameters considered. This finding is corroborated for a HT-HIT in this study. ...
In order to compensate for the variable mismatch between heat demand and heat production from renewable sources or waste heat, high-temperature aquifer thermal energy storage (HT-ATES) is a promising option. A reliable prediction of the energetic performance as well as thermal and hydraulic impacts of a HT-ATES requires a suitable model parameterization regarding the subsurface properties. In order to identify the subsurface parameters on which investigation efforts should be focused, we carried out an extensive sensitivity analysis of the thermal and hydraulic parameters for a high-temperature heat injection test (HIT) using numerical modeling of the governing coupled thermo-hydraulic processes. The heat injection test was carried out in a quaternary shallow aquifer using injection temperatures of about 75 °C over 5 days, accompanied by an extensive temperature monitoring. The sensitivity analysis is conducted for parameter ranges based on literature values, based on site investigation at the HIT site and based on a model calibrated to the measured temperature distribution following the heat injection. Comparing the parameter ranges thus obtained in this three-step approach allows to identify those parameters, for which model prediction uncertainty decreased most, which are also the parameters, that strongly affect the thermal behavior. The highest sensitivity is found for vertical and horizontal hydraulic conductivity as well as for groundwater flow velocity, indicating that investigation efforts for HT-ATES projects should focus on these parameters. Heat capacity and thermal conductivity have a smaller impact on the temperature distribution. Our work thus yields a consistent approach to identifying the parameters which can be best restricted by field investigations and subsequent model calibration. Focusing on these during field investigations thus enable improved model predictions of both HT-ATES operation and induced impacts.
... We perform five cycles in this study, taking a total time of five years. The operational time for injecting and producing hot fluid can be influenced by factors such as local climate conditions, heating demand, etc. (Sheldon et al., 2021;Beernink et al., 2024). The six months for heat storage and six months for heat extraction are chosen just for demonstration purposes. ...
... Previously, the MOOSE framework, in conjunction with the GOLEM application (Cacace and Jacquey, 2017), was utilized by Jacquey et al. (2018) to simulate hydraulic stimulation at the Geothermal Site of GroßSchönebeck. Moreover, Sheldon et al. (2021) employed MOOSE with PorousFlow module to investigate the thermo-hydraulics of an aquifer thermal energy storage system. Additionally, Smith et al. (2022) utilized MOOSE with Porous-Flow module to calculate permeability of fractures and its implications for geothermal fluid flow and the influence of seismic-scale faults. ...
This study presents a thermo-hydro-mechanical framework to model hydrothermal systems within a simplified faulted synthetic reservoir, replicating current production scenarios in The Netherlands and Germany. The reservoir, composed of porous and permeable sandstone, and the confining layer, made of porous but less permeable shale, undergoes a process where cold water is injected and hot water is extracted. A fault, situated 750 meters from the injection well, is investigated to examine the conditions when fault slip could occur. Various fault and formation stiffnesses are modeled to assess their impact on fault stability. Our analysis reveals that stress changes induced by hydrothermal operations can lead to fault reactivation, with the stiffness contrast between the reservoir and confining layers playing a significant role in when and where fault reactivation can occur. Stiffer confining layers lead to reactivation occurring more closely associated with the passage of the cooling front. In contrast, a stiffer reservoir results in greater and more gradual stress changes, making reactivation more closely related to the total volume of cooled rock.
... The Upper Jurassic reservoir of the North Alpine Foreland Basin comprises the most significant target horizon for conventional geothermal exploitation of the hydrothermal resource in the German Molasse Basin, southern Germany. This stems from the combined effect of favourable reservoir temperature and in situ hydraulic conditions (Steiner et al., 2014), while the reservoir conditions and geographical location, close to the Munich metropolitan area, turn it into a significant asset to contribute towards covering the high local energy demand. As manifesting a southward dipping towards the Northern Alpine Front, the karstified and fractured carbonate rocks attain depths of up to 6 km, and reservoir temperatures rise from approx. ...
Concepts of High-Temperature Aquifer Thermal Energy Storage (HT-ATES) (> 50 °C) are investigated in this study for system application in the Upper Jurassic reservoir (Malm aquifer) of the German Molasse Basin (North Alpine Foreland Basin). The karstified and fractured carbonate rocks exhibit favourable conditions for conventional geothermal exploitation of the hydrothermal resource. Here, we perform a physics-based numerical analysis to further assess the sustainability of HT-ATES development in the Upper Jurassic reservoir. With an estimated heating capacity of approx. 19.5 MW over half a year, our approach aims at determining numerically the efficiency of heat storage under the in situ Upper Jurassic reservoir conditions and projected operation parameters. In addition, the hydraulic performance of the HT-ATES system is further evaluated in terms of productivity and injectivity index. The numerical models build upon datasets from three operating geothermal sites at depths of approx. 2000–3000 m TVD, located in a subset of the reservoir dominated by karst-controlled fluid fluxes. Commonly considered as a single homogeneous unit, the 500 m thick reservoir is subdivided into three discrete layers based on field tests and borehole logs from the three considered sites. The introduced vertical heterogeneity with associated layer-specific enhanced permeabilities allows to examine potentially arising favourable heat transfer, and in combination with the facilitated high operation flow rates (100 kg s−1) to evaluate thermal recoveries in the multilayered reservoir. All simulations account for fluid density and viscosity variation based on thermodynamically consistent equations of state (EOS). Computation results reveal that the reservoir layering induces preferential fluid and heat migration primarily into the high-permeability zone, while thermal front propagation into the lower permeable rock matrix is inhibited. The simulations further display a gradual temperature increase in the warm wellbore and its surrounding host rock, and a consequent progressive improvement in the heat recovery efficiency. Despite the elevated permeability that may trigger advective heat losses, heat recovery factor values range from approx. 0.7 over the first year of operation to over 0.85 after 10 years of operation. An additional scenario is examined with fluid injection solely in the high permeable zone, in order to quantify potential enhancement in the recovery efficiency by omitting fluid injection in the lower-permeability layers where heat propagation is diminished. This is due to the geometrical shape of the thermally perturbed rock volume as heat losses occur during thermal equilibration between injected fluid and reservoir rock, as well as at the contact-surface area between propagating thermal front and adjacent rock matrix. Results suggest that under the stratified reservoir configuration, additionally constrained by the selected spatial distribution of rock properties, heat storage performed only into the upper high-permeability zone corresponds to an improved thermal performance. Simulation results further indicate that density-induced buoyant fluxes, which would considerably decrease thermal efficiencies are inhibited in the system, and the prevailing heat transport mechanism is forced convection.
... Traditionally, UTES systems have operated within a temperature range of 30 to 120 degrees Celsius [7,8,6], primarily because these systems have been used for direct applications such as temperature regulation in buildings. However, there is growing interest in applying UTES systems to industrial processes and power generation, thereby extending their temperature range. ...
This study presents an innovative approach to integrating concentrated solar power (CSP) with ultra-high-temperature underground thermal energy storage (UTES) as a geothermal battery for power generation. UHT-UTES is a combination of a CSP plant and a Geothermal Battery. The system consists of two main wells, a Brayton cycle and an Organic Rankine Cycle (ORC), which are used to convert the heat from the CSP into electricity. The ORC is used to extract heat from the CSP and the ORC is used to extract heat. The analytical solution is based on a one-dimensional (1D) approach to calculate the heat injection cycle in the battery, employing a one-dimensional approach. The numerical results show that the system can maintain more than 94% of its initial output capacity after 30 years, demonstrating the potential of this hybrid approach to enhance the longevity and reliability of renewable energy systems. The study further shows that the effectiveness of the UHT-UTES system depends on site-specific parameters, such as Direct Normal Irradiance (DNI) and subsurface temperatures.
... Several studies have highlighted the role of RTES in renewable energy integration, energy efficiency and the reduction of greenhouse gas emissions (Banks 2012;Bloemendal et al. 2014;Sheldon et al. 2021;Beckers et al. 2022;Pastore and Cherubini 2022). Thermal storage in subsurface porous media refers to the practice of storing thermal energy in the form of hot water within the porous layers of rock, sand or soil underground, which can be later retrieved for various applications such as space heating, domestic hot water, electricity generation and industrial processes. ...
The intermittency of renewable energy sources necessitates effective energy storage solutions. This study narrows in on Reservoir Thermal Energy Storage (RTES) as a system to bridge the supply-demand gap through the storage and recovery of heated water for periods ranging from daily to monthly timescales. By injecting hot water into subsurface formations and later retrieving it for use in electricity generation or direct heating, the viability of RTES is explored for load-leveling applications, typically on daily to monthly timescales, rather than extended seasonal or multi-year storage. Many factors including formation parameters (permeability, porosity, thermal conductivity of rock, thickness, insulating layers), completion parameters like injection well design, operational parameters such as injection and production rates, and schedule affect the facility's performance. The two key performance indicators (KPI) considered herein are the produced water temperature and the heat recovery factor. In this study, three operational strategies and four different well completions are investigated using a coupled fluid-thermal simulation model. Heat loss from the upper and lower boundaries of the reservoir is also studied. While the immediate impact of initial hydro-thermal charging on produced water temperature may not persist in the long-term operation, it does influence the overall system efficiency by reducing the cumulative heat recovery. Through detailed analysis, it is demonstrated that vertical injection across the entire well length offers a balanced approach between minimizing pumping costs and maximizing heat extraction efficiency. This study establishes basic calculations for developing innovative operational and completion strategies to maximize the long-term economic benefit of RTES.
... Another approach to using ambient ground temperature for cooling in 5GDHC systems is to use an aquifer thermal energy storage (ATES) system (Sheldon et al., 2021). An ATES system uses the groundwater in an aquifer to store and release heat. ...
District heating (DH) networks are a key component of low-carbon urban heating in the future, as greenhouse gas emissions and sustainability concerns drive the heating sector to transform itself. DH is not a new technology, but it has been constantly evolving. The latest generation of DH facilitates the distribution of low-temperature renewable heat sources. In recent years, most studies have focused on managing peak demand, improving low-carbon technologies, and improving load prediction. However, there is a risk of misinterpretation, as recent generations of DH, which operate at significantly lower temperatures than conventional DH, are being developed simultaneously. This review aims to analyze the different definitions of the fifth-generation district heating and cooling (5GDHC) and introduce a straightforward concept of this new technology. It also describes the potential strengths, weaknesses, and challenges of integrating 5GDHC into existing systems, as well as practical recommendations. Finally, it analyzes the crucial components and notable characteristics of 5GDHC to provide a clear picture of its evolution and uniqueness.
... Guo et al. [41] assessed the viability a compressed air energy storage in aquifers in reducing the intermittency effects of RE sources based on the review of numerical modeling and theoretical studies of this system. Other significant developments and optimizations of the operational and economic performance of AqTES, have been summarized in literature [37][38][39][40][41][42][43][44]. AqTES technologies are functional in several countries around the world, with >90 % operating in Netherlands [1]. ...
Integrating renewable energy systems into the grid has various difficulties, especially in terms of reliability, stability, and adequate operation. To control unpredictable loads, one potential approach is to incorporate energy storage systems (ESSs) into the power network. The implementation of an ESS is dependent on its technical properties, the implementation site, the electrical energy source (conventional or renewable energy types), and its related costs. Therefore, an up-to-date database with technical and economic properties, cost data, and applications is necessary for decision-making purposes. Moreover, the integration of ESSs with renewables should be based on an optimal sizing analysis that incorporates system modeling and proper formulations of technical and financial design criteria. This paper provides an overview of recent developments in the field of energy storage; combining a comprehensive assessment of the technical and economic characteristics of the various types of energy storage systems, and creating a pertinent database with the technical specifications and cost figures of both established and newly developed energy storage systems. The reviewed research works present all metrics that affect the performance of each type of storage and discuss their future directives and innovations. Moreover, recent analyses of integrating energy storage systems with hybrid photovoltaic/wind power systems are also discussed in terms of system modeling, performance analysis indicators, and optimization methods. By combining all these aspects, our research significantly contributes to the existing literature and offers a holistic understanding of energy storage systems and their role in hybrid power plant applications.
... The thermal efficiency of energy storage systems is intrinsically tied to the effective utilization of energy and the economic operation of these systems [10,11]. Systems exhibiting high thermal efficiency can mitigate thermal energy losses, thereby reducing operational costs and lessening environmental heat load. ...
... For LT-ATES systems, conduction and dispersion leads to energy losses (Bloemendal & Hartog, 2018). Additionally for HT-ATES systems, energy losses due to buoyancy flow (also often referred to as free convection) can be of considerable impact on the performance (Sheldon et al., 2021;van Lopik et al., 2016;Winterleitner et al., 2018). Buoyancy flow occurs because of the density difference between the stored hot (light) groundwater and the cold (dense) ambient groundwater. ...
The suitability of high temperature aquifer thermal energy storage (HT-ATES) systems, among many other applications in the subsurface, is for a large extent determined by the hydrogeological aquifer properties. Important subsurface properties that are challenging to fully determine in the field are the hydraulic conductivity, the vertical variation of hydraulic conductivity and associated anisotropy factor between vertical and horizontal hydraulic conductivity. To know to what extend these uncertain parameters need to be known for optimal design, the effect these properties have on the performance of HT-ATES wells is studied via numerical simulations of ATES wells under varying operational conditions for yearly storage cycles. Results show that for low temperature storage (<30 °C), hydraulic conductivity anisotropy does not affect the recovery efficiency, as energy losses driven by buoyancy flow do not occur. For storage at high temperature (90 °C), buoyancy flow negatively affects recovery efficiencies, but it's influence decreases with lower vertical permeability (higher anisotropy). HT-ATES wells in vertically layered aquifers are compared to homogeneous aquifers with equal upscaled hydraulic conductivity determined with averaging. When the vertical layering variation occurs on a relatively large scale, the systems perform differently (in most cases more energy loss due to buoyancy flow and conduction, in some cases positive influence due to re-use of upward driven hot water.) Only when the layers are small (m scale) and equally distributed across the height of the aquifer, HT-ATES performance is similar to equal homogeneous anisotropic scenario. In general, the results of this study indicate that the variability of hydraulic conductivity anisotropy and layering in an aquifer impact HT-ATES performance. Moreover, upscaling of initial hydraulic conductivity for performance modelling is often not possible on the aquifer scale. Hence, it is essential to perform characterization of the aquifer on appropriate scales (both small scale and large scale) and perform modelling by using appropriately upscaled hydraulic conductivity or by simulating the appropriate sub-layers in the aquifer.
... For example, Schout et al. (2014) extended the widely adopted Rayleigh number -recovery factor relationship for identifying site suitability of LT-RTES systems (Gutierrez-Neri et al., 2011) to HT-RTES systems. Sheldon et al. (2021) further improved the Rayleigh number relationship to consider daily cycles for HT-RTES systems. In addition to recovery factor, the performance metrics of HT-RTES include storage capacity, operational duration, etc. Jin et al. (2021Jin et al. ( , 2022 performed stochastic thermo-hydraulic simulations and used a machine learning algorithm to directly correlate formation parameters and operational conditions with multiple HT-RTES performance metrics using the simulated big data. ...
Reservoir thermal energy storage (RTES) is a promising technology to balance the mismatch between energy supply and demand. In particular, high temperature (HT) RTES can stabilize the grid with increasing penetration of renewable energy generation. This paper presents the investigation of the mechanical deformation and chemical reaction influences on the performance of HT-ATES for the Lower Tuscaloosa site. Thermo-hydraulic (TH), thermo-hydro-mechanical (THM), and thermo-hydro-chemical (THC) coupled simulations were performed with different operational modes and injection rates for a fixed five-spot well configuration and a seasonal cycle. The results show that (1) geomechanical-induced porosity change is mainly contributed by effective stress change, and the porosity change is distributed through the whole system; (2) geochemistry-induced porosity change is located near the hot well, and its change is one order of magnitude higher than the geomechanical effect; (3) both the operation mode and the injection rate have a huge influence on the RTES performance and lower injection rate with push-pull operation mode has the best performance with recovery factor around 70% for this RTES system. These results shed light on the deployment of HT-RTES in the US and around the world.
1 INTRODUCTION
The concept of reservoir thermal energy storage (RTES), also known as geological thermal energy storage (GeoTES) or aquifer thermal energy storage (ATES), to mitigate the mismatch between energy supply and demand has been applied around the world since the 1960s with mixed success. Given its nearly unlimited storage capacity and easy accessibility, RTES has the potential to become an indispensable component to achieve the goal of carbon-neutral energy.
Most successful deployments of RTES are operated at low temperatures (LT) (< 25°C), mainly to heat buildings by storing excess thermal energy during the low-use periods (summer) and recovering it during peak energy demand periods (winter). As reviewed by Fleuchaus et al. (2018), there are currently more than 2800 RTES systems worldwide, and 99% are LT-RTES. However, only high-temperature (HT) RTES has the capacity to serve as an earth battery for stabilizing the grid as indicated in McLing et al. (2019). The research and development of HT-RTES have mainly focused on site suitability studies and performance optimization by only considering fluid flow and heat transfer. For example, Schout et al. (2014) extended the widely adopted Rayleigh number - recovery factor relationship for identifying site suitability of LT-RTES systems (Gutierrez-Neri et al., 2011) to HT-RTES systems. Sheldon et al. (2021) further improved the Rayleigh number relationship to consider daily cycles for HT-RTES systems. In addition to recovery factor, the performance metrics of HT-RTES include storage capacity, operational duration, etc. Jin et al. (2021, 2022) performed stochastic thermo-hydraulic simulations and used a machine learning algorithm to directly correlate formation parameters and operational conditions with multiple HT-RTES performance metrics using the simulated big data. All these investigations can facilitate the deployment of HT-RTES. However, geomechanical response and geochemical reactions involved during the operation of a HT-RTES system can potentially induce risks as identified by Fleuchaus et al. (2020), and their effects on HT-RTES performance have not been systematically reported.
... For example, Schout et al. (2014) extended the widely adopted Rayleigh number -recovery factor relationship for identifying site suitability of LT-RTES systems (Gutierrez-Neri et al., 2011) to HT-RTES systems. Sheldon et al. (2021) further improved the Rayleigh number relationship to consider daily cycles for HT-RTES systems. In addition to recovery factor, the performance metrics of HT-RTES include storage capacity, operational duration, etc. Jin et al. (2021Jin et al. ( , 2022 performed stochastic thermo-hydraulic simulations and used a machine learning algorithm to directly correlate formation parameters and operational conditions with multiple HT-RTES performance metrics using the simulated big data. ...
Reservoir thermal energy storage (RTES) is a promising technology to balance the mismatch between energy supply and demand. In particular, high temperature (HT) RTES can stabilize the grid with increasing penetration of renewable energy generation. This paper presents the investigation of the mechanical deformation and chemical reaction influences on the performance of HT-ATES for the Lower Tuscaloosa site. Thermo-hydraulic (TH), thermo-hydro-mechanical (THM), and thermo-hydro-chemical (THC) coupled simulations were performed with different operational modes and injection rates for a fixed five-spot well configuration and a seasonal cycle. The results show that (1) geomechanical-induced porosity change is mainly contributed by effective stress change, and the porosity change is distributed through the whole system; (2) geochemistry-induced porosity change is located near the hot well, and its change is one order of magnitude higher than the geomechanical effect; (3) both the operation mode and the injection rate have a huge influence on the RTES performance and lower injection rate with push-pull operation mode has the best performance with recovery factor around 70% for this RTES system. These results shed light on the deployment of HT-RTES in the US and around the world.
In coastal areas the seawater intrusion region underlying freshwater aquifers represents a low quality but wide and deep geo resource. Seasonal thermal energy storage and recovery is an important component of district heating and cooling system to manage renewable energy fluctuations, such as solar irradiance or waste heat from industrial processes, and the corresponding mismatch of thermal energy demand and supply. A numerical tool to evaluate the performance of seasonal Borehole Thermal Energy Storage (BTES) system to store and recover solar energy in the seawater intrusion region, underlying the shallow freshwater aquifer and with thermally and hydraulically insulated upper borehole section is developed and applied to the coastal carbonate aquifer of the metropolitan area of Bari (Italy). The hourly thermal demand of the University Sport Centre of Bari is used as benchmark. The design and performance of the BTES system is strongly dependent on the geological and hydrogeological context as well as on the environmental and operational conditions. The aquifer characterization suggests to locate BTES zone at a depth higher than 100 m from the freshwater – saltwater interface where carbonate unit appears less fractured and karstified showing a value of bulk permeability less than 10⁻¹² m² and the groundwater flow is slow (∼10⁻³ md⁻¹). Rayleigh number criterion is used as constraint to determine the maximum heat storage temperature (∼70°C) in order to preserve the lateral thermal stratification and the thermal impact on the shallow freshwater resource. A novel mathematical and computational model is developed to help the design of BTES system and to evaluate its efficiency. The results indicate that the thermal losses within thermally insulated zone influence the effective thermal recovery factor which, according to the baseline scenario, is equal to 47% after five years of operation. The heat energy production of the solar heating system, covers the heat demand with percentage range of 79–117%. The location of BTES in deep seawater region attenuates the decreases of efficiency due to the groundwater flow which became significant at specific discharge around 10⁻² md⁻¹. Changing the operation schedule with a shorter heating storage period increases the thermal recovery factor of the BTES of 11.19% after five years of operation, but at the same time the trend of the heat energy production shows a surplus during the midseason and deficit during the winter and summer season respect to the thermal demand. Great care must be taken on the maximum heat storage temperature. A low heat storage temperature ensures a wider safety margin with regards to the thermal stratification and the thermal impact on the shallow aquifer. Anyway, a decrease of 10°C on the maximum heat storage temperature produces a deficit of the heat production respect to the thermal demand in the range of 15%–21%.
High-temperature reservoir thermal energy storage (HT-RTES) has the potential to become an indispensable component in achieving the goal of the net-zero carbon economy, given its capability to balance the intermittent nature of renewable energy generation. In this study, a machine-learning-assisted computational framework is presented to identify HT-RTES site with optimal performance metrics by combining physics-based simulation with stochastic hydrogeologic formation and thermal energy storage operation parameters, artificial neural network regression of the simulation data, and genetic algorithm-enabled multi-objective optimization. A doublet well configuration with a layered (aquitard-aquifer-aquitard) generic reservoir is simulated for cases of continuous operation and seasonal-cycle operation scenarios. Neural network-based surrogate models are developed for the two scenarios and applied to generate the Pareto fronts of the HT-RTES performance for four potential HT-RTES sites. The developed Pareto optimal solutions indicate the performance of HT-RTES is operation-scenario (i.e., fluid cycle) and reservoir-site dependent, and the performance metrics have competing effects for a given site and a given fluid cycle. The developed neural network models can be applied to identify suitable sites for HT-RTES, and the proposed framework sheds light on the design of resilient HT-RTES systems.
This paper presents the numerical investigation of the geological thermal energy storage (GeoTES) by considering well configuration, discrete fracture network (DFN), and mechanical effect. After validated against field experiments, the MOOSE framework was used to simulate the GeoTES with geological properties from the Weber/Tensleep formation. Mono-well, doublets with different well distance, 5-spot with and without discrete fracture network, and 5-spot with and without mechanical deformation were modeled based on annual injection-storage-extraction-rest cycle for over 10 years. Each period in a cycle lasts for one season, and the same amount of water was injected and extracted within each year. Results show that: (1) the highest recovery efficiency 37% is yielded from the mono-well and the 5-spot without DFN, suggesting that extracting thermal energy directly from the injection well is the best practice; (2) the presence of DFN yield less recovery efficiency, and the pore pressure continues to build-up; (3) thermal expansion and mechanical volumetric strain increase upon three months of injection can only increase the formation permeability about 3% at maximum, indicating the influence the mechanical behavior is negligible for the investigated GeoTES. Future work towards a detailed reservoir model with consideration of chemical reaction is undergoing.
Harnessing modern parallel computing resources to achieve complex multiphysics simulations is a daunting task. The Multiphysics Object Oriented Simulation Environment (MOOSE) aims to enable such development by providing simplified interfaces for specification of partial differential equations, boundary conditions, material properties, and all aspects of a simulation without the need to consider the parallel, adaptive, nonlinear, finite element solve that is handled internally. Through the use of interfaces and inheritance, each portion of a simulation becomes reusable and composable in a manner that allows disparate research groups to share code and create an ecosystem of growing capability that lowers the barrier for the creation of multiphysics simulation codes. Included within the framework is a unique capability for building multiscale, multiphysics simulations through simultaneous execution of multiple sub-applications with data transfers between the scales. Other capabilities include automatic differentiation, scaling to a large number of processors, hybrid parallelism, and mesh adaptivity. To date, MOOSE-based applications have been created in areas of science and engineering such as nuclear physics, geothermal science, magneto-hydrodynamics, seismic events, compressible and incompressible fluid flow, microstructure evolution, and advanced manufacturing processes.
Aquifer Thermal Energy Storage (ATES) systems combined with a heat pump save energy for space heating and cooling of buildings. In most countries the temperature of the stored heat is allowed up to 25-30°C. However, when heat is available at higher temperatures (e.g. waste heat, solar heat), it is more efficient to store higher temperatures because that improves heat pump performance or makes it unnecessary. Therefore, interest in HT-ATES development is growing. Next to developing new HT-ATES projects, there is also a large potential for additional energy savings by transforming 'regular' low-temperature LT-ATES systems to a HT-ATES. Such a transformation is tested for a greenhouse system in the Netherlands. This greenhouse has a LT-ATES system operational since 2012, and from 2015 onwards heat is stored in the warm well at temperatures up to 45°C. In this HT-ATES transformation pilot, water quality parameters are closely monitored as well as temperature distribution in the subsurface (using DTS). Together with the operators, the results from the ATES monitoring are used to continuously improve system performance. Numerical groundwater and heat flow simulations of actual and expected well pumping data are used to evaluate how well operation can be optimized. In this paper, the optimization using monitoring results and simulations is discussed as well as general and site specific lessons/conclusions for such transformations.
Aquifer thermal energy storage (ATES) is a technology with worldwide potential to provide sustainable space heating and cooling using groundwater stored at different temperatures. In areas with high ambient groundwater flow velocity (> 25 m/y) thermal energy losses by displacement of groundwater may be prevented by application of multiple doublets. In such configurations two or more warm and two or more cold wells are aligned in the direction of the ambient groundwater flow. By controlling the infiltration and extraction rates of the upstream and downstream wells, the advection by ambient groundwater flow can be compensated by storing thermal energy through the upstream well, while re-extracting it from the downstream well. This study uses analytical and numerical tools and a case study to analyze the relevant processes, and provides guidelines for well placement and an operation strategy for ATES wells in aquifers with considerable groundwater flow. The size of the thermal radius relative to ambient groundwater flow velocity is an important metric. With multiple wells to counteract groundwater flow, this ratio affects the pumping scheme of these wells. The optimal distance between them is around 0.4 times the distance traveled by the groundwater in one year. A larger distance negatively affects the efficiency during the first years of operation.
High temperature aquifer thermal energy storage (HT-ATES) can contribute to the integration of renewable energy sources in the energy system, the replacement of fossil fuel-based heat supply and the utilization of surplus heat from industrial sources. However, there is limited understanding on the drivers, barriers and conditions of HT-ATES implementation. The objective of this study is to partly fill this knowledge gap by developing a methodological framework for a quick scan on market potential of HT-ATES. Based on the application of this framework to a case study in the Netherlands, it is concluded that the proposed method is suitable for a pre-feasibility analysis on the HT-ATES market potential. The investigated case study has a planned district heating system with geothermal energy as the heat source. HT-ATES is found to be cost-effective compared to a reference technology, i.e. a natural gas boiler, in the scenarios under existing and more sustainable alternative policies. The lifetime of HT-ATES and the size of heat demand have a strong influence on the market potential.
Aquifer thermal energy storage (ATES) is a technology with worldwide potential to provide sustainable space
heating and cooling using groundwater stored at different temperatures. The thermal recovery efficiency is one
of the main parameters that determines the overall energy savings of ATES systems and is affected by storage
specifics and site-specific hydrogeological conditions. Although beneficial for the optimization of ATES design,
thus far a systematic analysis of how different principal factors affect thermal recovery efficiency is lacking.
Therefore, analytical approaches were developed, extended and tested numerically to evaluate how the loss of
stored thermal energy by conduction, dispersion and displacement by ambient groundwater flow affect thermal
recovery efficiency under different storage conditions. The practical framework provided in this study is valid for
the wide range of practical conditions as derived from 331 low-temperature (< 25 °C) ATES systems in practice.
Results show that thermal energy losses from the stored volume by conduction across the boundaries of the
stored volume dominate those by dispersion for all practical storage conditions evaluated. In addition to conduction,
the displacement of stored thermal volumes by ambient groundwater flow is also an important process
controlling the thermal recovery efficiencies of ATES systems. An analytical expression was derived to describe
the thermal recovery efficiency as a function of the ratio of the thermal radius of the stored volume over ambient
groundwater flow velocity (Rth/u). For the heat losses by conduction, simulation results showed that the thermal
recovery efficiency decreases linearly with increasing surface area over volume ratios for the stored volume (A/
V), as was confirmed by the derivation of A/V-ratios for previous ATES studies. In the presence of ambient
groundwater flow, the simulations showed that for Rth/u <1 year, displacement losses dominated conduction
losses. Finally, for the optimization of overall thermal recovery efficiency as affected by these two main processes,
the optimal design value for the ratio of well screen length over thermal radius (L/Rth) was shown to
decrease with increasing ambient flow velocities while the sensitivity for this value increased. While in the
absence of ambient flow a relatively broad optimum exists around an L/Rth-ratio of 0.5–3, at 40 m/year of
ambient groundwater flow the optimal L/Rth-value ranges from 0.25 to 0.75. With the insights from this study,
the consideration of storage volumes, the selection of suitable aquifer sections and well screen lengths can be
supported in the optimization of ATES systems world-wide.
Energy Procedia; Volume 135, October 2017, Pages 327-336
(https://www.sciencedirect.com/science/article/pii/S1876610217346295)
High Temperature Aquifer Thermal Energy Storage (HT-ATES) has developed from a demonstration stage to a mature technology over the past decades. The specific storage capacity costs are lower by a factor of 20 compared to above-ground storage systems. Depending on geology, system configuration and temperature level, medium deep aquifers (approx. 400 m – 1,000 m) enable seasonal heat storage from 1 GWh/a up to 100 GWh/a. Typical heat recovery factors are in between 60 – 80 %. However, only three systems have been built and reached normal operation in Europe. Moreover, although substantial parts of the subsurface in Germany, for example, are suitable for ATES systems, over 10 years have passed since the most recent project has been put into operation.
Despite substantial advantages and a great potential of bridging the gap between constant production and seasonally varying demand, ATES is quite complex and conditional. Critical hydro-geological conditions (e.g. permeability, porosity, mineralisation) as well as relevant ordinances and regulations from the mining and local water authorities should be complied with. In addition, geothermal projects are not always supported by public acceptance as drilling boreholes today is a sensitive and emotional topic.
This contribution deals with an interdisciplinary approach to evaluate all parameters (geology, legal classification, public acceptance, water chemistry, applications/revenue models and drilling technology) affecting a cost-effective operation of ATES systems in North Germany. One main objective is to identify possible locations for ATES in the North German Basin and to derive generalizable success factors. Preliminary results and an overview of the project supported by the Federal Ministry of Economic Affairs and Energy are presented. The project consortium consists of Leuphana University of Lüneburg and GeoDienste GmbH, supported by GeoEnergy Celle e.V.
Keyword: Aquifer Thermal Energy Storage (ATES), medium-deep, geological-technical-economic potential
The Leuphana University of Lueneburg changed to renewable energy supply with the first climate-neutral energy balance for heat, electricity, cars and business trips in 2014. The heating network is based on two biomethane-powered combined-heat-and-power (CHP) units of 525 kWel. each. A total of 720 kWp photovoltaics with 95% self-consumption covers > 20% of the electrical demand. We present the campus development and transformation to provide a best-practice example for conversion to exergy-efficient renewable energy systems.The new central building provides a large auditorium, seminar rooms, offices, a cafeteria, machine hall and space for exhibitions and events. It uses low-grade heat at 58 °C for optimized integration of short and long term heat storage installations. The architecture and façade design significantly lower cooling demand (≈ 2.5 kWh/m²a), modern lighting systems and user integration allow for superior overall energy efficiency. Exergy efficiency, storage options and emissions of the campus system as well as energy efficiency of the buildings were analysed. A high-temperature aquifer thermal energy storage (HT-ATES) installation perfectly matches the low-exergy heating demands and increases the share of CHP-heat, resulting in an additional surplus of 2.3 GWh/a of renewable electricity and additional savings of 2.424 t CO2-eq./a.
The concept of Underground Thermal Energy Storage (UTES) has evolved from theory to the point where system feasibility has been demonstrated technically and commercially in particular for low-temperature applications. These types of systems are typically referred to as Aquifer Thermal Energy Storage (ATES).
One of the most common applications of ATES is the heating and cooling of spaces. In contrast, high-temperature energy storage (HTES) systems have received less attention. HTES applications (where the temperature ranges between 60-100°C) can be of significant value, especially in connection with energy sources which are not controlled by immediate demand such as residual heat (e.g. from power plants or industrial processes) or renewable sources such as geothermal or solar energy. By storing temporally the excess of energy, a better balance between the supply and demand can be obtained. It can
also be applied as back-up capacity or to simply preserve the heat and energy. An overview of the different type of UTES systems and their most common applications is given in [1].
An important aspect of a HTES project is the recovery (or storage) efficiency, defined as the relation between the amount of recovered energy in one season and the amount stored during another season. This work presents the results of a modelling study on the hydrothermal behaviour of an HTES system. Simulations are carried out to evaluate the influence of hydraulic, thermal, and operational parameters on the recovery efficiency.
Geothermal resources used to generate power are complex systems. The hydrother‐ mal, high-temperature geothermal reservoirs, which are the only commercially exploited ones up to now, are usually found several (1-3 km) kilometers deep, and they should be exploited in a sustainable way. Thus, in order to support decisions on optimal exploitation policies, efforts focused on investigating how reservoirs respond to exploitation are routinely made. The better strategies always involve a compromise of controlling energy extraction from geothermal reservoirs without overexploiting the resource. Currently, methods based on the analysis of monitoring data of either the geochemical characteristics of fluids discharged (water and steam) or production data gathered from wells have been used to assess the reservoir performance, making it possible to predict the occurrence of negative processes in terms of production. However, by the analysis of combined geochemical and production data through simulation of wells, the well-bottom thermodynamic conditions of fluids are included in the study, allowing more reliable results to be obtained. Besides, the comparison of actual patterns of behavior of chemical and production indicators with those characteristic for typical processes, helps in identifying different physical phenomena and in deciding which is dominant in the case of the occurrence of more than one processes.
We present an overview of the risks that underground thermal energy storage (UTES) can impose on the groundwater system, drinking water production, and the subsurface environment in general. We describe existing policy and licensing arrangements for UTES in the Netherlands, as well as the capability of the current and future Dutch policy and legal framework to minimize or mitigate risks from UTES on groundwater resources. A survey at the European Union member state level indicates that regulation and research on the potential impacts of UTES on groundwater resources and the subsurface environment often lag behind the technological development of and ever-growing demand for this renewable energy source. The lack of a clear and scientifically underpinned risk management strategy implies that potentially unwanted risks might be taken at vulnerable locations such as near well fields used for drinking water production, whereas at other sites, the application of UTES is avoided without proper reasons. This means that the sustainability of UTES as a form of renewable energy is currently not fully understood, and the technology may be compromising the natural resilience of the subsurface environment. We recognize three main issues that should be addressed to secure sustainable application of UTES: Scientific research is required to further elucidate the impacts of UTES on groundwater; cross-sectoral subsurface planning is required to minimize negative conflicts between UTES and other subsurface interests; and EU-wide guidelines and standards are required for quality assurance and control when installing UTES systems.
This paper describes a case study on HT-ATES in the community of Vierpolders, The Netherlands, meant for storage of excess heat from a geothermal doublet.
This paper describes the practical experiences and geochemical impact of water treatment methods to prevent
clogging of the wells by mineral precipitation.
Since 2005, the Neubrandenburg aquifer thermal energy store (ATES) which is installed at a depth of approx. 1,200 m is in regular operation. This presentation focuses on the energy bal-ances of the three cycles of operation completed so far without any major problems. The store was charged with 14,300 MWh in 2005/06 and 12,800 MWh in 2007/08, and 6,500 or 5,900 MWh were discharged with a recovery coefficient of 46 %, respectively. The previous 50 % share of the peak-load boilers in the heat supply decreased to 0.2 % by 2007/2008. Generally, the materials and equipment applied in the thermal water loop proved their suit-ability, with very few exceptions. Numerous full analyses of samples from both wells were assessed within the framework of the accompanying geochemical and microbiological monitoring programme. The most impor-tant results are presented here.
The use of redox potential measurements for corrosion and scaling monitoring, including microbially mediated processes, is demonstrated. As a case study, monitoring data from 10 years of operation of an Aquifer Thermal Energy Storage site (ATES) located in Berlin, Germany, were examined.
(Fe2 +)-activities as well as [Fe3 +]-build up rates were calculated from redox potential, pH, conductivity, temperature and dissolved oxygen measurements. Calculations are based on assuming (Fe3 +)-activity being controlled by Fe(OH)3-solubility, the primary iron(III)-precipitate. This approach was tested using a simple log-linear model including dissolved oxygen besides major Fe2 +-ligands. Measured redox potential values in groundwater used for thermal storage are met within ± 8 mV. In other systems comprising natural groundwater and in heating and cooling systems in buildings, quantitatively interpretable values are obtained also.
It was possible to calculate particulate [Fe3 +]-loads in the storage fluids in the order of 2 μM and correlate a decrease in filter lifetimes to [Fe3 +]-build up rates, although observations show clear signs of microbially mediated scaling processes involving iron and sulphur cycling.
Macroscopic dispersion is the mixing, on the scale of several hundreds of grain diameters, at a point in a permeable medium that is free of boundary effects. Megascopic dispersion is the one-dimensional (1D) dispersion derived by averaging across an entire cross section. This work investigates how both dispersions vary with heterogeneity, aspect ratio, diffusion coefficient, and autocorrelation. The theoretical results are compared to existing field and laboratory data and to existing theories for limiting cases.
The degree of autocorrelation in the medium determines whether or not megascopic dispersivity (dispersion coefficient divided by velocity) is uniquely defined. Large correlation distances (with respect to the medium dimensions) imply a dispersivity that grows with distance traveled. Small correlation distances imply a dispersivity that is eventually stabilized at some constant value. This value is related to the heterogeneity of the medium. On the field scale, diffusion is insignificant, but on a laboratory scale, it can stabilize the dispersivity even if the medium is correlated. Macroscopic dispersivity is sensitive to diffusion in both the laboratory and field scale. It is smaller than or equal to megascopic dispersivity, also in conformance with experimental data, and comparable to laboratory-measured dispersivity.
After the German re-unification in 1990, the Reichstag building in Berlin was completely refurbished to house again the German Parliament, the "Bundestag". The design of this work was in the hands of the British architect Sir Norman Foster, and since the first presentation of his plans in 1992 the energy concept included a geothermal component, i.e. the storage of thermal energy in the underground. Two aquifers at different depth are used to store cold (ca. 60 m) and heat (ca. 300 m). The paper explains the system concept and the realised installation and presents first results of a monitoring campaign. The underground storage is operational since 1999, however, the full capacity of the total system and the final operational strategy could not be tested before completion of the energy network and all buildings involved in 2003. Both storage systems, after minor teething problems, performed to satisfaction. The monitoring was of great importance to detect and solve some operational inaccuracies and to optimise the system hardware as well as the operational strategies.
Numerical-simulation studies of transport and flow in porous media are essential in many practical fields of research. Including the coupling of different physical processes allows accurate modelling of the effects of fluid flow and temperature changes on the subsurface reservoir structure, and conversely, the effects of reservoir-structure changes on fluids and heat. In this study, we introduce the development of a physics module for non-isothermal, multicomponent, multiphase flow in porous media, as part of the open-source, multiphysics simulation framework MOOSE.
Through tight interfaces with existing physics modules for solid mechanics and aqueous geochemistry, massively parallel, fully implicit, fully coupled thermo-hydro-mechanical-chemical simulations are possible. MOOSE and the porous flow module are freely available under an open-source license, making MOOSE a platform for collaborative efforts in this field of research.
Aquifer thermal energy storage (ATES) has been confirmed to be an effective thermal energy storage method and medium-to-high-temperature (MHT) ATES is receiving renewed interest. To illustrate the thermal performance of MHT ATES systems in the presence of natural regional groundwater flow and facilitate the future implementation of such systems, simulations including the effect of thermal dispersion are performed for a typical confined ATES system that consists of doublet wells and is operated in cyclic mode. The simulation model is validated using experimental data. The sensitivity of the system performance to hydrogeological and design/operation parameters is assessed using the thermal front, thermal breakthrough time, characteristic tilting time, and thermal recovery ratio. Based on the simulation results, the rules governing the influence of these parameters are presented and feasible storage site conditions and design/operation parameters for MHT ATES application are suggested.
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 CO2 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 socio-economic and legislative nature.
This updated edition of a widely admired text provides a user-friendly introduction to the field that requires only routine mathematics. The book starts with the elements of fluid mechanics and heat transfer, and covers a wide range of applications from fibrous insulation and catalytic reactors to geological strata, nuclear waste disposal, geothermal reservoirs, and the storage of heat-generating materials. As the standard reference in the field, this book will be essential to researchers and practicing engineers, while remaining an accessible introduction for graduate students and others entering the field. The new edition features 2700 new references covering a number of rapidly expanding fields, including the heat transfer properties of nanofluids and applications involving local thermal non-equilibrium and microfluidic effects.
• Recognized as the standard reference in the field
• Includes a comprehensive, 350-page reference list
• Cited over 5900 times to date in its various editions
• Serves as an introduction for those entering the field and as a comprehensive reference for experienced researchers
• Covers the latest developments in research on nanofluids and CO2 sequestration
There are three types of petroleum wells potentially capable of supplying geothermal energy for electric power generation: (a) a producing oil or gas well with a water cut, (b) an oil or gas well abandoned because of a high water cut, and (c) a geopressured brine well with dissolved gas. This paper considers the basic technical and economic aspects of power generations from each of the three types of wells and presents case histories of estimating the available power capacity of a typical well (or a group of wells) in each of the above categories. We have conducted these assessments for commercial developers and operators. The power capacity of wells in the first category is determined primarily by the production rate and temperature of the produced water, ambient temperature, and conversion efficiency of the geothermal power plant. The factors that control the wellhead temperature of the produced fluid are: formation temperature, well depth, well diameter and production rate. Our assessment of some producing oil wells in the Middle East showed that in spite of an attractive formation temperature, the wellhead temperature of the produced water was too low compared to the ambient temperature to allow commercial generation of geothermal power. However, solar energy or the gas being flared in such a field could be used to boost the temperature of the produced water and increase the power capacity. The power capacity of an abandoned gas well depends on: (a) production rate and temperature of the produced water, (b) ambient temperature, (c) conversion efficiency of the geothermal power plant, (d) water salinity, (e) gas content in the produced fluid, (f) heating value of the gas, and (g) the characteristics of the equipment used to generate power from the produced gas. The production rates of water and gas from such a well depend on the hydraulic properties of the formation, gas content (dissolved as well as free) in the formation water, formation temperature and pressure, and well design. It is shown that the well's productivity could be substantially improved by working it over; both pumping and self-flowing the well are considered. A conceptual design of a hybrid system to produce power from both the produced gas and water is proposed. A case history of assessment of such a gas well from the U.S. Gulf Coast is presented in the paper; it is concluded that power generation from the well is technically feasible, and can be commercially acceptable. The possible approaches to improving the project economics are discussed.
According to the decision of the German Parliament, forward-looking, environmentally responsible, and examplary energetic concepts were to be implemented for the supply of energy to the Parliament buildings in the Spree river curve in Berlin, focusing on the high utilisation of the primary energy. Vegetable-oil fired block type cogeneration units and the integration of one aquifer heat and cold store, respectively, are to make sure that 82 % of the electric work of the overall complex and even 90 % of the annual heat demand will be covered by power and heat cogeneration. The cold store – to be charged in particular with ambient winter cold – will cover 60 % of the cold demand in summer. Thus, the environment-benign combustion of bio-fuel plus the operation of the cold store will result in a 60 % reduction of CO 2 emission compared to conventional technical solutions. At the time of the compilation of this manuscript, the system was in the phase of commissioning.
High-temperature aquifer thermal energy storage (HT-ATES) is an
important technique for energy conservation. A controlling factor for
the economic feasibility of HT-ATES is the recovery efficiency. Due to
the effects of density-driven flow (free convection), HT-ATES systems
applied in permeable aquifers typically have lower recovery efficiencies
than conventional (low-temperature) ATES systems. For a reliable
estimation of the recovery efficiency it is, therefore, important to
take the effect of density-driven flow into account. A numerical
evaluation of the prime factors influencing the recovery efficiency of
HT-ATES systems is presented. Sensitivity runs evaluating the effects of
aquifer properties, as well as operational variables, were performed to
deduce the most important factors that control the recovery efficiency.
A correlation was found between the dimensionless Rayleigh number (a
measure of the relative strength of free convection) and the calculated
recovery efficiencies. Based on a modified Rayleigh number, two simple
analytical solutions are proposed to calculate the recovery efficiency,
each one covering a different range of aquifer thicknesses. The
analytical solutions accurately reproduce all numerically modeled
scenarios with an average error of less than 3 %. The proposed method
can be of practical use when considering or designing an HT-ATES system.
To aid in testing the idea of storing thermal energy in aquifers, an
experiment was performed by Auburn University in which 54,784
m3 of water was pumped from a shallow supply aquifer, heated
to an average temperature of 55°C, and injected into a deeper
confined aquifer where the ambient temperature was 20°C. After a
storage period of 51 days, 55,345 m3 of water were produced
from the confined aquifer. Throughout the experiment, which lasted
approximately 6 months, groundwater temperatures were recorded at six
depths in each of 10 observation wells, and hydraulic heads were
recorded in five observation wells. In order to prevent errors due to
thermal convection, most of the observation wells recording temperature
had to be backfilled with sand. During the 41-day production period, the
temperature of the produced water varied from 55° to 33°C, and
65% of the injected thermal energy was recovered. At no time was an
appreciable amount of free thermal convection observed in the storage
formation. The dominant heat dissipation mechanisms appeared to be
hydrodynamic thermal dispersion and possible mixing of cold and hot
water induced by clogging and unclogging of the injection-production
well. On the basis of laboratory and field studies, it was concluded
that clogging of the injection well, which constituted the major
technical problem during the experiment, was caused by the
freshwater-sensitive nature of the storage aquifer. Due to the
relatively low concentration of cations in the supply water, clay
particles would swell, disperse, and migrate until they became trapped
in the relatively small pores connecting the larger pores. Surging the
pump and back washing the injection well would dislodge the clogging
particles and temporarily improve the storage formation permeability.
The phenomenon seems largely independent of temperature because it was
reproduced in the laboratory with unheated water. It may, however,
depend on pore velocity. Future research should be directed toward
procedures for selecting storage aquifers that will have minimal
susceptibility to clogging and other geochemical problems. Procedures
for overcoming such difficulties are needed also because clogging and
related phenomena will be more the rule than the exception. Designing an
aquifer thermal storage system for maximum energy recovery would involve
selecting an appropriate aquifer, analyzing the effects of hydrodynamic
thermal dispersion and thermal convection if it is predicted to occur,
anticipating geochemical problems, designing the optimum
supply-injection-production well configuration and injecting a
sufficiently large volume of heated water to realize economies of scale
related to increasing volume-surface area ratio.
When a well is pumped or otherwise discharged, water‐levels in its neighborhood are lowered. Unless this lowering occurs instantaneously it represents a loss of storage, either by the un‐watering of a portion of the previously saturated sediments if the aquifer is nonartesian or by release of stored water by the compaction of the aquifer due to the lowered pressure if the aquifer is artesian. The mathematical theory of ground‐water hydraulics has been based, apparently entirely, on a postulate that equilibrium has been attained and therefore that water‐levels are no longer falling. In a great number of hydrologic problems, involving a well or pumping district near or in which water‐levels are falling, the current theory is therefore not strictly applicable. This paper investigates in part the nature and consequences of a mathematical theory that considers the motion of ground‐water before equilibrium is reached and, as a consequence, involves time as a variable.
This study considers the thermal behavior around a storage well in the case when buoyancy effects can be neglected. A dimensionless formulation of the energy transport equations for the aquifer system is presented, and the key dimensionless parameters are discussed. A numerical model using a steady flow field is used to simulate heat transport in the aquifer and confining layers around the injection/production well during the aquifer thermal energy storage cycle. The key parameters are varied in order to understand their influence on the percent of the injected energy that can be recovered and the temperature of the extracted water. The results are presented graphically. 26 refs.
Analytical solutions for the pressure distribution and the flow field are derived for several idealized situations involving an injection well and a vertical plane or cylindrical interface between two fluids of different density and viscosity in an infinite anisotropic aquifer bounded by two horizontal planes. The interface, or transition zone, between the two fluids may be either sharp or of finite width. The buoyancy flow induced by the density difference will cause the two-fluid interface to tilt. A characteristic time scale for the buoyancy tilting rate is deduced. The conditions at the well are found to have only a small influence on the buoyancy flow except very close to the well. The buoyancy flow decreases with increasing width of the transition zone.
A critical review of dispersivity observations from 59 different field
sites was developed by compiling extensive tabulations of information on
aquifer type, hydraulic properties, flow configuration, type of
monitoring network, tracer, method of data interpretation, overall scale
of observation and longitudinal, horizontal transverse and vertical
transverse dispersivities from original sources. This information was
then used to classify the dispersivity data into three reliability
classes. Overall, the data indicate a trend of systematic increase of
the longitudinal dispersivity with observation scale but the trend is
much less clear when the reliability of the data is considered. The
longitudinal dispersivities ranged from 10-2 to
104 m for scales ranging from 10-1 to
105 m, but the largest scale for high reliability data was
only 250 m. When the data are classified according to porous versus
fractured media there does not appear to be any significant difference
between these aquifer types. At a given scale, the longitudinal
dispersivity values are found to range over 2-3 orders of magnitude and
the higher reliability data tend to fall in the lower portion of this
range. It is not appropriate to represent the longitudinal dispersivity
data by a single universal line. The variations in dispersivity reflect
the influence of differing degrees of aquifer heterogeneity at different
sites. The data on transverse dispersivities are more limited but
clearly indicate that vertical transverse dispersivities are typically
an order of magnitude smaller than horizontal transverse dispersivities.
Reanalyses of data from several of the field sites show that improved
interpretations most often lead to smaller dispersivities. Overall, it
is concluded that longitudinal dispersivities in the lower part of the
indicated range are more likely to be realistic for field applications.
In 1997, the International Association for the Properties of Water and Steam (IAPWS) adopted a new formulation for the thermodynamic proper-ties of water and steam for industrial use. This new formulation, called IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam (IAPWS-IF97), replaces the previous industrial formulation, IFC-67, that had formed the basis for power-plant calculations and other applications in energy engineering since the late 1960's. IAPWS-IF97 improves significantly both the accuracy and the speed of the calculation of the thermodynamic properties compared with IFC-67. The differences between IAPWS-IF97 and IFC-67 will require many users, particularly boiler and turbine manufacturers, to modify design and application codes. This paper summarizes the need and the requirements for such a new industrial formulation and gives the entire numerical information about the individual equations of IAPWS-IF97. Moreover, the scientific basis for the development of the equations is summarized and the achieved quality of IAPWS-IF97 is presented regarding the three criterions accuracy, consistency along region boundaries, and computation speed. For comparison, corresponding results for the previous standard IFC-67 are also presented.
Electrical power plant and solar heating systems have been proposed wherein confined ground-water aquifers are used as temporary storage reservoirs for thermal energy in the form of moderate to high temperature water (140°F-400°F; 60°C-204°C). The Water Resources Research Institute of Auburn University has performed an aquifer storage experiment involving warm water (97°F; 36°C). The objectives of the experimental program were to begin actual testing of the concept of heat storage in aquifers and to provide data for calibration of mathematical models describing the simultaneous transport of water and heat. Phase I consisted of drilling an exploratory well at the selected field site near Mobile, Alabama. Phase II involved construction of the central injection well, three observation wells, and performance of preliminary pumping tests. Phase III was devoted to construction of the remainder of the observation well field, performance of final pumping tests, and measurement of aquifer thermal properties; while Phase IV was devoted to a cycle of warm-water injection, storage, and recovery. It was concluded that heat storage aquifers must have low natural pore velocities, and care must be taken not to clog the injection well with solids or precipitated chemicals. Swelling of clays in the storage formation must be minimized, and hydraulic pressures capable of breaching the confining layers must be avoided. Mechanical and chemical clogging problems may be minimized by using formation water as influent to the heating system. For a 36-day storage of 2 million gallons, the calculated energy recovery factor of 0.69 was considered promising. Future research should be directed toward experimental studies involving larger volumes of water and high-injection temperatures. Study should be directed also to the geochemistry problem and the effect of high temperatures on the mechanical and hydraulic properties of clay confining layers.
A new approach to the derivation of local extremum diminishing finite element schemes is presented. The monotonicity of the Galerkin discretization is enforced by adding discrete diffusion so as to eliminate all negative off-diagonal matrix entries. The resulting low-order operator of upwind type acts as a preconditioner within an outer defect correction loop. A generalization of TVD concepts is employed to design solution-dependent antidiffusive fluxes which are inserted into the defect vector to preclude excessive smearing of solution profiles by numerical diffusion. Standard TVD limiters can be applied edge-by-edge using a special reconstruction of local three-point stencils. As a fully multidimensional alternative to this technique, a new limiting strategy is introduced. A node-oriented flux limiter is constructed so as to control the ratio of upstream and downstream edge contributions which are associated with the positive and negative off-diagonal coefficients of the high-order transport operator, respectively. The proposed algorithm can be readily incorporated into existing flow solvers as a ‘black-box’ postprocessing tool for the matrix assembly routine. Its performance is illustrated by a number of numerical examples for scalar convection problems and incompressible flows in two and three dimensions.
Modeling ground surface deformation at the Swiss HEATSTORE underground thermal energy storage sites
- D T Birdsell
- M O Saar
Engineering aspects of geothermal production well with down hole pumps
- Kaya
HEATSTORE SWITZERLAND: New opportunities of geothermal district heating network sustainable growth by high temperature aquifer thermal energy storage development
- L Guglielmetti
- P Alt-Epping
- D T Birdsell
- F De Oliveira Filho
- L-W Diamond
- T Driesner
- O.-E Eruteya
- P Hollmuller
- Y Makhloufi
- U Marti
- F Martin
- P Meier
- M Meyer
- J Mindel
- A Moscariello
- C Nawratil De Bono
- Quiquerez
- Loïc
- M O Saar
- R Sohrabi
- B Valley
- D Van Den Heuvel
- C Wanner
Heatstore: High temperature underground thermal energy storage
- Joris Koornneef
- Guglielmetti
- Luca
- Hahn
- Florian
- Egermann
- Patrick
- Vangkilde-Pedersen
- Thomas
- Edda Aradottir
- Sif
- Allaerts
- Koen
- Viveiros
- Fátima
- Maarten Saaltink
High temperature aquifer storage
- Martina Ueckert
- Reinhard Niessner
- Thomas Baumann