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1.
A mathematical model is developed for simulating the thermal energy transfer in a confined aquifer with different geological properties in the underlying and overlying rocks. The solutions for temperature distributions in the aquifer, underlying rock, and overlying rock are derived by the Laplace transforms and their corresponding time-domain solutions are evaluated by the modified Crump method. Field data adopted from the literature are used as examples to demonstrate the applicability of the solutions in modeling the heat transfer in an aquifer thermal energy storage (ATES) system. The results show that the aquifer temperature increases with time, injection flow rate, and water temperature. However, the temperature decreases with increasing radial and vertical distances. The heat transfer in the rocks is slow and has an effect on the aquifer temperature only after a long period of injection time. The influence distance depends on the aquifer physical and thermal properties, injection flow rate, and injected water temperature. A larger value of thermal diffusivity or injection flow rate will result in a longer influence distance. The present solution can be used as a tool for designing the heat injection facilities for an ATES system. 相似文献
2.
Aquifer thermal energy storage (ATES) is used for seasonal storage of large quantities of thermal energy. Due to the increasing demand for sustainable energy, the number of ATES systems has increased rapidly, which has raised questions on the effect of ATES systems on their surroundings as well as their thermal performance. Furthermore, the increasing density of systems generates concern regarding thermal interference between the wells of one system and between neighboring systems. An assessment is made of (1) the thermal storage performance, and (2) the heat transport around the wells of an existing ATES system in the Netherlands. Reconstruction of flow rates and injection and extraction temperatures from hourly logs of operational data from 2005 to 2012 show that the average thermal recovery is 82 % for cold storage and 68 % for heat storage. Subsurface heat transport is monitored using distributed temperature sensing. Although the measurements reveal unequal distribution of flow rate over different parts of the well screen and preferential flow due to aquifer heterogeneity, sufficient well spacing has avoided thermal interference. However, oversizing of well spacing may limit the number of systems that can be realized in an area and lower the potential of ATES. 相似文献
3.
Aquifer thermal energy storage (ATES) is an underground thermal energy storage technology with a large potential to decarbonise the heating and cooling of buildings. ATES installations typically store thermal energy in aquifers that are also exploited for potable water, so a major consideration during development is ensuring that system operation will not lead to groundwater pollution. In this study, the risk of contamination due to upconing of a shallow freshwater/saltwater interface during ATES operation is investigated. Fluid flow, and heat and salt (chloride ion) transport are simulated in a homogeneous aquifer during ATES operation via a well doublet. The impact of geological, hydrological and operational parameters is investigated in a sensitivity analysis. Two new dimensionless numbers are proposed to characterise salt upconing and redistribution during ATES operation and provide a close match to simulated concentrations: CR,w characterises the contamination risk at the ATES installation, and CR,d characterises the risk at locations downstream of the ATES installation with respect to background groundwater flow. ATES systems with CR,w and CR,d < 10 introduce low risk of contamination in a homogenous aquifer, with chloride concentration at, and downstream of, the ATES system, remaining below the World Health Organisation’s advised limit. ATES installations with CR,w and CR,d > 10 cause a rapid increase in aquifer chloride concentration. The results are used to estimate an exclusion distance beyond which ATES system operation will not cause contamination in a homogenous aquifer. The dimensionless parameters proposed allow rapid assessment of the potential for saltwater contamination during ATES operation. 相似文献
4.
A modeling study was carried out to evaluate the influence of aquifer heterogeneity, as represented by geologic layering, on heat transport and storage in an aquifer thermal energy storage (ATES) system in Agassiz, British Columbia, Canada. Two 3D heat transport models were developed and calibrated using the flow and heat transport code FEFLOW including: a “non-layered” model domain with homogeneous hydraulic and thermal properties; and, a “layered” model domain with variable hydraulic and thermal properties assigned to discrete geological units to represent aquifer heterogeneity. The base model (non-layered) shows limited sensitivity for the ranges of all thermal and hydraulic properties expected at the site; the model is most sensitive to vertical anisotropy and hydraulic gradient. Simulated and observed temperatures within the wells reflect a combination of screen placement and layering, with inconsistencies largely explained by the lateral continuity of high permeability layers represented in the model. Simulation of heat injection, storage and recovery show preferential transport along high permeability layers, resulting in longitudinal plume distortion, and overall higher short-term storage efficiencies. 相似文献
5.
Temperature distribution and heat transport are studied in a coastal aquifer at De Panne in the western Belgian coastal plain. Field observations include temperature profiles of groundwater in the dunes and temperature measurements at the water table in a profile on the shore. Freshwater–saltwater distribution is known from previous studies. These are used to constrain a density-dependent model simulating the freshwater–saltwater distribution and heat transport using the SEAWAT code. The yearly fluctuation of the groundwater temperature in the phreatic aquifer under the dunes, shore and sea, and the influence of a tidal inlet in the dunes are simulated. The observations show that seawater temperature variations determine the temperature variations on the shore whereas atmospheric temperature changes determine this in the dunes. Yearly temperature fluctuations imposed at the water table propagate mainly vertically in the aquifer with only limited lateral influence. Heat transport is mainly convection dominated. Thickness of the surficial zone is determined by the amplitude of the groundwater temperature at the water table and the groundwater flow. Establishment of a tidal inlet in the dunes results in asymmetric temperature profiles under and in the vicinity of it. 相似文献
6.
The impact of groundwater withdrawals on the interaction between multi-layered aquifers with different water qualities in the Viterbo geothermal area (central Italy) was studied. In this area, deep thermal waters are used to supply thermal spas and public pools. A shallow overlying aquifer carries cold and fresh water, used for irrigation and the local drinking-water supply. Starting with a conceptual hydrogeological model, two simplified numerical models were implemented: a steady-state flow model of the entire groundwater system, and a steady-state flow and heat transport model of a representative area, which included complex interactions between the aquifers. The impact of increased withdrawals associated with potential future development of the thermal aquifer must be considered in terms of the water temperature of the existing thermal sources. However, withdrawals from the shallow aquifer might also influence the discharge of thermal sources and quality of the water withdrawn from the shallow wells. The exploitation of the two aquifers is dependent on the hydraulic conductivity and thickness of the intervening aquitard, which maintains the delicate hydrogeological equilibrium. Effective methods to control this equilibrium include monitoring the vertical gradient between the two aquifers and the residual discharge of natural thermal springs. 相似文献
7.
The progressive electrification of the building conditioning sector in recent years has greatly contributed to reducing greenhouse gas emissions by using renewable energy sources, particularly shallow geothermal energy. This energy can be exploited through open and closed shallow geothermal systems (SGS), and their performances greatly depend on the ground/groundwater temperature, which can be affected by both natural and anthropogenic phenomena. The present study proposes an approach to characterize aquifers affected by high SGS exploitation (not simulated in this work). Characterization of the potential hydro/thermogeological natural state is necessary to understand the regional flow and heat transport, and to identify local thermal anomalies. Passive microseismic and groundwater monitoring were used to assess the shape and thermal status of the aquifer; numerical modeling in both steady-state and transient conditions allowed understanding of the flow and heat transport patterns. Two significant thermal anomalies were detected in a fluvio-glacial aquifer in southern Switzerland, one created by river water exfiltration and one of anthropogenic nature. A favorable time lag of 110 days between river and groundwater temperature and an urban hot plume produced by underground structures were observed. These thermal anomalies greatly affect the local thermal status of the aquifer and consequently the design and efficiency of current and future SGS. Results show that the correct characterization of the natural thermo-hydrogeological status of an aquifer is a fundamental basis for determining the impact of boundary conditions and to provide initial conditions required to perform reliable local thermal sustainability assessments, especially where high SGS exploitation occurs. 相似文献
8.
Thermal perturbation in the subsurface produced in an open-loop groundwater heat pump (GWHP) plant is a complex transport phenomenon affected by several factors, including the exploited aquifer’s hydrogeological and thermal characteristics, well construction features, and the temporal dynamics of the plant’s groundwater abstraction and reinjection system. Hydraulic conductivity has a major influence on heat transport because plume propagation, which occurs primarily through advection, tends to degrade following conductive heat transport and convection within moving water. Hydraulic conductivity is, in turn, influenced by water reinjection because the dynamic viscosity of groundwater varies with temperature. This paper reports on a computational analysis conducted using FEFLOW software to quantify how the thermal-affected zone (TAZ) is influenced by the variation in dynamic viscosity due to reinjected groundwater in a well-doublet scheme. The modeling results demonstrate non-negligible groundwater dynamic-viscosity variation that affects thermal plume propagation in the aquifer. This influence on TAZ calculation was enhanced for aquifers with high intrinsic permeability and/or substantial temperature differences between abstracted and post-heat-pump-reinjected groundwater. 相似文献
9.
含水介质中地下水热量运移过程模拟是地源热泵系统这类新型浅层地温能利用工程科学论证的重要内容。通过建立饱和含水介质中热量运移对流-弥散数学模型,模拟了拟建地源热泵系统理想的对井抽-灌运行特定水流及热源条件下地下水热量运移过程。结果表明热泵系统完整运行周期(一年)内地下水热量运移过程具有显著的"阶段性"特征,"夏、冬抽-灌输运"和"春、秋停运蓄存"两阶段取决于不同的作用因素。从数学和概念模型两方面讨论了地下水流作用对热量输运过程的决定性影响,说明不同时期抽、灌井互换运行是解决拟定工作模式下热(冷)能浪费问题的理想途径。 相似文献
10.
Large thermal extractions and extensive implementation of groundwater heat pumps (GWHP) necessitate a validation of the sustainability of their use and possible detrimental effects on groundwater. The goal of this work is to develop a regional heat transport model (of ~13 km × 5 km) for real site conditions. This model should consider all relevant transport processes, despite the large area under investigation. The model is based on a two-dimensional, transient-calibrated groundwater flow model for the “Leibnitzer Feld” (Styria, Austria). The two-dimensional horizontal model is linked via the FEFLOW interface manager with a newly developed “Multi-Layer-Model”-tool, which reproduces thermal aquifer–atmosphere interaction. Based on the regional heat transport model, scenarios are delineated for heating and cooling purposes for large GWHPs, which are appropriate for a small manufacturing business, an administrative building and 10 family homes. First of all, these have large spacing and thereafter, effects of area-covering usage of geothermal systems are evaluated for five administrative buildings located in close proximity to one another (200–350 m) and also for a large number of smaller heat extractions (each representing a one family house system). Modeled spatial and temporal temperature effects on the shallow aquifer are discussed. It was possible to present a simulation of realistic heating and cooling scenarios. This simulation may be introduced into practice once some further simplifications to the system are made. Locally limited heat plumes (max. length: 625 m) were observed for the manufacturing business. Any thermal effects coming from the geothermal systems were shown to be temporally stable. As such, no distinct trend of reduced annual temperatures could be observed. 相似文献
11.
Thermal perturbation produced in the subsurface by open-loop groundwater heat pumps (GWHPs) represents a complex transport phenomenon that is affected by several factors, including intrinsic characteristics of the exploited aquifer, abstraction and reinjection well features, and the temporal dynamics of the accessed groundwater. Post-GWHP water may have become warmed or cooled before being reinjected into the aquifer, thereby creating a thermal plume, known as the thermal affected zone (TAZ), which can alter aquifer temperature. The TAZ is propagated mainly by advection, after which the plume tends to degrade via conductive heat transport and convection within moving water. Groundwater monitoring and multiparametric probes are used to check the dynamics of plume propagation and whether a system’s thermal plumes are generating unsuitable interference with wells, subsurface infrastructure, or land use. Analyses of time-series groundwater monitoring data can be used to monitor TAZ movement. In this paper, the thermal plume velocity was calculated by both an analytical solution and cross-correlation. Cross-correlation calculated between temperature measured in the reinjection well and control downstream piezometers can reveal plume dynamics and demonstrate the importance of advective transport in aquifer heat transfer. 相似文献
12.
通过对昆明地热田深层基岩地下热水系统的地质、水文地质条件和开采现状的分析,建立了考虑温压变化和越流条件的岩溶热储层中地下热水的水流和溶质(污染物)运移的准三维非稳定流数学模型。对开采条件下地热田Ⅱ 块段地下热水系统中水位及F- 、Cl- 、NH+4 、SO2-4 浓度的模拟结果表明,所建立的模型合理、可靠,具有较高的仿真性。模型可预测不同条件下地热田地下热水的流场和溶质浓度的动态变化趋势,为防治地下热水环境的进一步恶化提供参考。 相似文献
13.
通过建立地下水地源热泵系统试验场,运行热泵系统,并进行地下水温度连续监测,分析应用地下水地源热泵系统对地温场的影响。抽水井与回灌井之间以及回灌井附近的地下水温度随系统运行明显变化。系统运行后,回灌水体将以不规则边缘的透镜体贮存于含水层中,以回灌井为中心向外围扩展,水温最低或最高点位于含水层中部。粘性土相对隔水层的温度变化幅度、影响范围均小于含水层。由于热量的累积效应,即使是冷热负荷均衡的热泵系统,运行一个采暖、制冷周期后也将在热源井附近的抽、灌水含水层以及相邻的隔水层中形成冷量或热量的小范围聚积。 相似文献
14.
Aquifer storage and recovery (ASR) is considered as a strategy for the storage of water to ensure a sustainable water supply in the Abu Dhabi emirate. Earlier investigations have been conducted, and two sites were proposed for the installation of ASR in the surficial aquifer. Recently, the site located in the center of Abu Dhabi (sand dune area) was executed, and the second site is undergoing the pilot phase of the study. However, the performance and influence of the regional groundwater system may vary depending on regional hydrogeological characteristics, which have not been investigated. Hence, this study attempts to understand the feasibility of the proposed ASR sites in the surficial aquifer using a regional model developed by the finite-difference approach with an accuracy of 0.28 m mean residual difference. Additionally, six sites were selected on the basis of the literature and aquifer parameters and were investigated for their suitability for future ASR installation. Six cycles of injection and recovery at various rates were analyzed at each ASR site by using a transient calibrated model until the end of the year 2030. The area of influence is axisymmetrical in the sand dune area and non-symmetrical in the east and northeastern areas because of the steep topography and groundwater table gradient. At the sites that possess a non-symmetrical influence, the area of influence is always high upstream of the groundwater flow. Heterogeneity-induced variation in the fluctuation of the groundwater table is noted in all sites. Even with 100% recovery, the groundwater table did not reach the ambient groundwater table during the recovery period. This finding confirms the contribution of regional groundwater to the site during recovery. All sites selected for future ASR installation, except site 5, are capable of storing the volume needed to meet expected water demand. Site 2 is considered the most suitable site for ASR installation in the future. This study will facilitate the scientific communities and authorities in understanding the feasibility of ASR installation for sustainable water storage and supply in the Abu Dhabi emirate. 相似文献
15.
深层含水层储热是一种利用深度>500 m的深层含水层作为储热介质的储热技术,储热对象通常为50~150 ℃的热水。它通过地下水井从深层含水层中抽取和灌入地下水,实现热能储存和回收。深层含水层储热技术是弥补能源供需时空分布的不平衡,综合利用多种可再生能源,实现节能减排的有效途径,是国内外研究的前沿和热点。文中首先阐述了深层含水层储热系统在世界范围内的历史发展,归纳储热系统的热工性能,在总结前人研究工作的基础上分析影响其热回收效率的关键参数,并对各个参数对热回收效率的敏感性做了综述。在此基础上,本文还讨论了限制深层含水层储热系统发展的技术瓶颈,并针对系统的经济效益和市场潜力做了预测和展望。 相似文献
16.
岩溶含水介质的不均一性导致岩溶地下水流动、溶质运移和热量迁移的数学模拟研究成为地下水模拟的难点。本文综述了岩溶区地下水流模拟的几种方法,重点阐述了等效多孔介质法、双重连续介质法和三重介质法的定义、发展过程和适用范围,并回顾了这几种方法的研究成果。从等效多孔介质法到三重介质法,模拟精度不断提高,适用范围也逐渐由大区域实际问题向小区域理论研究过渡。介绍了溶质运移模拟和热迁移模拟的研究方法及实例。溶质运移模拟以对流弥散方程为基础,其中尺度效应是溶质运移模拟的重点研究问题;热量迁移模拟应考虑地下热水密度变化对地下热水运动的影响。溶质运移模拟和热量迁移模拟往往是将迁移模型和已经调试成功的地下水流动模型相耦合,从而达到模拟溶质及热量迁移的目的。由于溶质运移和热量迁移的复杂性,现阶段水流模型多数处于等效多孔介质模型阶段。综合理论及实际应用,指出精确刻画裂隙及管道和注重基础数学算法是岩溶水数值模拟进步的关键。 相似文献
17.
Due to its large heat transfer area and stable thermal performance,the middle-deep coaxial borehole heat exchanger (CBHE) has become one of the emerging technologies to extract geothermal energy. In this paper,a numerical modeling on a three-dimensional unsteady heat transfer model of a CBHE was conducted by using software FEFLOW,in which the model simulation was compared with the other studies and was validated with experimental data. On this basis,a further simulation was done in respect of assessing the influencing factors of thermal extraction performance and thermal influence radius of the CBHE. The results show that the outlet temperature of the heat exchanger decreases rapidly at the initial stage,and then tended to be stable; and the thermal influence radius increases with the increase of borehole depth. The heat extraction rate of the borehole increases linearly with the geothermal gradient. Rock heat capacity has limited impact on the heat extraction rate,but has a great influence on the thermal influence radius of the CBHE. When there is groundwater flow in the reservoir,the increase of groundwater velocity will result in the rise of both outlet temperature and heat extraction rate. The heat affected zone extends along with the groundwater flow direction; and its influence radius is increasing along with flow velocity. In addition,the material of the inner pipe has a significant effect on the heat loss in the pipe,so it is recommended that the material with low thermal conductivity should be used if possible. 相似文献
18.
大气降水的氢氧同位素含量具有高程效应,降水入渗后参与地下水循环,其高程效应如何受地下水流系统的影响转化为地下水氢氧同位素的深度效应？现有研究对于这个问题缺少定量认识。文章构建单向倾斜盆地和双峰波状盆地的稳态地下水循环理论模型,采用MODFLOW模拟剖面二维地下水流场、采用MT3DMS模拟重同位素分子的对流-弥散过程,得到地下水D和 18O含量的空间分布,探讨了氢氧同位素高程效应在地下水流系统转化为深度效应的机理。结果表明：在单斜盆地,补给区大气降水D和 18O含量的高程效应转化为排泄区地下水δD和δ 18O值随埋深增大而指数型衰减的深度效应;在双峰波状盆地,当含水层渗透性相对入渗强度较大时(K 0/w=1 000),仅发育一个区域地下水流系统,在区域地下水的排泄区δD和δ 18O随埋深增大呈现S形曲线分布;当含水层渗透性相对入渗强度较小时(K0/w=250),双峰波状盆地发育多个局部地下水流系统,区域地下水的排泄区δD和δ 18O随埋深增大呈现S形曲线,而局部地下水排... 相似文献
19.
The impact of groundwater heat pumps on groundwater temperature is simulated by means of a 2D numerical groundwater model
in the Leibnitzer Feld aquifer, Austria. The model provides a basis for assessing the regional use of groundwater temperature
as an energy source. Since the groundwater table is shallow, the air temperature represents the main source controlling the
groundwater temperature. A temperature input function depending on the depth of the groundwater table is delineated from an
observed soil temperature profile and the air temperature. Given the diffuse and ubiquitous nature of the heat input, the
heat exchange is implemented as a third type boundary condition to enable two-way heat transfer. The temperature of the reinjected
water is limited to a decrease of 5 K and an absolute minimum of 5°C by Austrian law. The pumping rates needed to cover the
heat requirements of three typical users are determined for selected locations. It is shown that the reduction of the ambient
groundwater temperature approximately 300 m downstream of the reinjection wells is less than 0.5°C. Thus it can be concluded
that aquifers in similar settings show substantial potential to provide heating and warm water supply for buildings without
deteriorating the regional groundwater temperature regime. 相似文献
20.
以丘陵地区某医院水源热泵系统为例,在建立耦合数学模型的基础上,利用TOUGH2软件,讨论含水层孔隙度以及渗透系数对潜水水热运移的影响,定量评价对热泵采能区域的温度场演化影响。在该研究区特定地质及水文地质条件下,含水层有效孔隙度和渗透系数等水文地质参数对热泵采能区域的温度场演化影响较明显。从而为研究类似地区的地下水环境变化有一定的借鉴意义。 相似文献
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