Geothermics最新文献

{"title":"Combining magnetotelluric, DC resistivity, and time-domain electromagnetic data in geothermal exploration: An example from the M’Deek Geothermal Field in Western British Columbia, Canada","authors":"Zoë Vestrum ,&nbsp;Martyn J Unsworth ,&nbsp;Tim Thompson ,&nbsp;David Try","doi":"10.1016/j.geothermics.2025.103452","DOIUrl":"10.1016/j.geothermics.2025.103452","url":null,"abstract":"<div><div>The M’Deek geothermal field is an extensional, fracture-controlled hydrothermal system located in western British Columbia, Canada. The system has surface expressions of hot springs and pockmarks. Heat is derived from past subduction on the west coast of North America.</div><div>Electric and electromagnetic (EM) geophysical methods are commonly used in the exploration for geothermal resources due to their sensitivity to the presence of both fluids and regions of hydrothermal alteration. In the initial stages of exploration, prior to this study, time-domain electromagnetics (TDEM) and direct-current (DC) resistivity methods were used to measure the near-surface resistivity structure. These datasets were inverted to obtain resistivity models, which showed a ∼100 m thick near-surface conductor. However, both of these methods have a limited depth of exploration. To image the deeper structure of the geothermal field, broadband magnetotelluric (MT) data were acquired in 2020 and 2022. The TDEM and DC inversion models were incorporated into the starting models for the MT inversion in order to improve the resolution of the near-surface conductor.</div><div>The preferred 3D MT inversion resistivity model of the M’Deek geothermal field shows a sub-vertical low resistivity feature at depths between 500 m and 5 km. This feature was interpreted to be the fault system, which acts as a conduit for the thermal waters that supply the hot springs. The fault system is the target for ongoing geothermal exploration. Sensitivity analysis showed that the fault had an estimated width of 400–1000 m, a strike between S and S45°W and a porosity of 10–20 %.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"133 ","pages":"Article 103452"},"PeriodicalIF":3.9,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144749176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparative study of hydrochemical characteristics and formation mechanisms of representative geothermal areas in Xinjiang area, Northwest China","authors":"Jiangyun Wang ,&nbsp;Mo Xu ,&nbsp;Chengpeng Ling ,&nbsp;Haojie Cheng ,&nbsp;Heng Zhang ,&nbsp;Jian Guo","doi":"10.1016/j.geothermics.2025.103459","DOIUrl":"10.1016/j.geothermics.2025.103459","url":null,"abstract":"<div><div>Geothermal resources have become one of the crucial clean energy sources worldwide. Geothermal systems in Xinjiang area, shaped by complex tectonic interactions across multiple domains, exhibit distinct hydrogeochemical signatures and circulation patterns. This study integrates hydrochemical analysis, stable isotopes, and geothermometric estimation to compare three major geothermal regions: Tashkurgan in the Inner Kunlun Mountains, the Tianshan orogenic belt, and the Altai tectonic belt. Results demonstrate that Tashkurgan geothermal waters, characterized by the HCO₃·SO₄·Cl-Na type, exhibit the highest reservoir temperatures reaching 258 °C and the circulation depths reaching 5030 m, driven by crustal thickening and magmatic heat sources, with minimal cold-water mixing ratios ranging from 0.31 to 0.94. In contrast, Tianshan geothermal systems, primarily of the SO₄·Cl-Na type, show moderate reservoir temperatures of 215 °C and circulation depths of 5163 m, influenced by NW-trending faults and medium heat flow. Altai geothermal water, dominated by the HCO₃·SO₄_-_<img>Na·Ca type, display the lowest temperatures averaging 118.5 °C and the shallowest circulation depths of 3499–3655 m, with extensive cold-water mixing ratios ranging from 0.95 to 0.97. Hydrogen-oxygen isotopes and ion ratios reveal meteoric recharge elevations decreasing northward, with Tashkurgan, Tianshan, and Altai ranging from 3915 to 5306 m, 3064 to 4161 m, and 2362 to 2983 m, respectively. Regional tectonic intensity governs heat flow and fracture permeability, whereas local lithology controls hydrochemical evolution.These findings provide a scientific basis for assessing geothermal resource potential and guiding sustainable development in Xinjiang.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"133 ","pages":"Article 103459"},"PeriodicalIF":3.9,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144749177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stochastic optimization of geothermal power plant capacity","authors":"Sigurdur Bjornsson ,&nbsp;Egill Juliusson ,&nbsp;Dadi Mar Kristofersson","doi":"10.1016/j.geothermics.2025.103444","DOIUrl":"10.1016/j.geothermics.2025.103444","url":null,"abstract":"<div><div>Geothermal resources play a role in the transition away from fossil fuels and can be crucial for local energy production and promoting social development. This paper indicates the optimal first capacity installment of a geothermal power plant and production paths under resource uncertainty. A stochastic, constrained, NPV maximization model is developed, explicitly including probabilities of possible realizations of the reservoir. Three factors are considered stochastic, reservoir heat content, well capacity decline and well drilling cost. Probability distributions are defined for each and possible scenarios defined. A case study is conducted for the Bjarnarflag geothermal area in Iceland. Of the stochastic factors, heat content most strongly affects the optimal first phase. Changing the underlying probability distribution for heat content considerably affects optimal outcomes, especially shifting. Narrowing non-symmetric distributions of heat content increases the optimal first phase while symmetric distributions do not. Including uncertainty in a stochastic model is responsible because using constant parameters disregards alternative realizations of the geothermal reservoir which can affect planning and development. New information decreases uncertainty and narrows distributions, produces more robust results, and increases the value of model output, showcasing the utility of the model. Less robust results can still support early-stage planning. This paper presents a non-biased method towards resource uncertainty and an alternative to traditional passive methods. Being unbiased towards uncertainty and considering geothermal development projects as a portfolio maximizes overall net benefits compared to precautionary development strategies for stand-alone projects.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"133 ","pages":"Article 103444"},"PeriodicalIF":3.9,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144724578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CO2 degassing and calcite precipitation from hot springs in the Litang, western Sichuan","authors":"Guangbin Tao ,&nbsp;Xun Zhou ,&nbsp;Yanqiu Wu ,&nbsp;Ruwen Cao ,&nbsp;Binghua Chen ,&nbsp;Zhuang Li ,&nbsp;Zhe Jiang ,&nbsp;Mengmeng Wang","doi":"10.1016/j.geothermics.2025.103442","DOIUrl":"10.1016/j.geothermics.2025.103442","url":null,"abstract":"<div><div>The travertine morphologies of the Gezha (GZ) hot spring and Maoya (MY) hot spring in the Litang area of western Sichuan exhibit significant differences. Elucidating the hydrochemical mechanism of travertine deposition is crucial for geothermal exploration, paleoenvironmental reconstruction, and ore potential assessment. A total of 17 water samples of the GZ and MY hot springs, and a travertine sample of the MY hot spring were collected to analyze the chemical compositions. Multiphasic (gas-water-solid) thermodynamic equilibrium models of calcite precipitation under various conditions were established to analyze the different hydrochemical mechanisms of the travertine deposition between the GZ hot spring and MY hot spring. The results indicate that significant degassing of CO₂, in GZ-1-1<span><math><mo>∼</mo></math></span>2, GZ-2 and MY-1-2 samples promotes calcite precipitation and increases pH value under low air pressure conditions. The calcite precipitation is less affected by the degassing of CO₂ in most other samples under various conditions. Furthermore, the calcite precipitation in the MY-8 vent is primarily regulated by <span><math><msup><mrow><mi>Ca</mi></mrow><mrow><mn>2</mn><mo>+</mo></mrow></msup></math></span> and <span><math><msubsup><mrow><mi>CO</mi></mrow><mrow><mn>3</mn></mrow><mrow><mn>2</mn><mo>−</mo></mrow></msubsup></math></span> chemical processes; however, CO₂ degassing would hinder the ascension of the calcite saturate index. The GZ hot spring exhibits less calcite precipitation and <span><math><msup><mrow><mi>Ca</mi></mrow><mrow><mn>2</mn><mo>+</mo></mrow></msup></math></span> complexes transformation than the MY hot spring generally. According to this study, the travertine deposition in the GZ hot spring is significantly affected by the intense degassing of CO₂ under low pressure conditions. Travertine is readily deposited near the vents, but its morphological development is constrained by the low <span><math><msup><mrow><mi>Ca</mi></mrow><mrow><mn>2</mn><mo>+</mo></mrow></msup></math></span> concentration. In contrast, The travertine deposition in the MY hot spring is less affected by CO₂ degassing, leading to a more widely distributed fissure-ridge travertine morphology. The differences in travertine morphologies between GZ and MY hot springs are also related to the influence of the faults on the geothermal water circulation processes. The multiphase thermodynamic equilibrium model is beneficial for understanding the hydrochemical genesis of travertine, especially for the CO₂-driven calcite precipitation process in plateau. Furthermore, it also offers a robust theoretical foundation for investigating the hydrogeochemical genesis of hot springs.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"133 ","pages":"Article 103442"},"PeriodicalIF":3.9,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144739488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental study on mineral precipitation prediction and mitigation for geothermal fluids in Clarke Lake Field in British Columbia, Canada","authors":"Kamran Hassani ,&nbsp;Wenbo Zheng ,&nbsp;Sudip Shrestha","doi":"10.1016/j.geothermics.2025.103458","DOIUrl":"10.1016/j.geothermics.2025.103458","url":null,"abstract":"<div><div>Mineral precipitation in geothermal facilities, caused by variations in geothermal fluid temperature, pressure, and ion composition, impedes fluid flow and reduces energy utilization efficiency. This study investigates the potential mineral precipitation of geothermal fluids in the Clarke Lake Field in British Columbia, focusing on unveiling scaling phenomena and exploring the potential integration of hydraulic fracturing flowback water. The primary goal is to identify potential scale types in geothermal brines from various fluid sources (i.e. formation water and two types of flowback water) and evaluate scale mitigation using a commonly used inhibitor. Geochemical simulations using PHREEQC were performed to analyze the influence of temperature and water chemistry on the formation of precipitation. Subsequently, laboratory experiments and analyses were performed to confirm mineral precipitation and evaluate inhibitor performance, including static bottle tests, scanning electron microscopy, X-ray diffraction, and inductively coupled plasma-optical emission spectrometry. Both simulations and laboratory analysis identified dolomite (CaMg(CO₃)₂) and calcite (CaCO₃) scaling for flowback water with additional barite (BaSO₄) scaling for some water samples, while formation water showed CaCO₃ and CaMg(CO₃)₂ in the Clarke Lake Field. The study also demonstrates the efficacy of the inhibitor in mitigating scale formation by inhibiting nucleation and chelating calcium and barium ions, with an inhibition efficiency of 63.2 % for CaCO₃ in formation water and efficiencies of about 30 % for BaSO₄ and CaCO₃ in flowback water.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"133 ","pages":"Article 103458"},"PeriodicalIF":3.9,"publicationDate":"2025-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144724579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of 10- and 25-year horizon designs for vertical borehole heat exchangers in geothermal heat pump applications","authors":"Stefano Morchio,&nbsp;Marco Fossa,&nbsp;Samuele Memme,&nbsp;Mattia Parenti,&nbsp;Antonella Priarone","doi":"10.1016/j.geothermics.2025.103457","DOIUrl":"10.1016/j.geothermics.2025.103457","url":null,"abstract":"<div><div>The precise design of Borehole Heat Exchanger (BHE) fields in ground-coupled heat pump (GCHP) systems is essential for maintaining optimal long-term performance. Conventional sizing methodologies, such as the ASHRAE method, typically account for a 10-year operational horizon. This study seeks to expand the applicability of the ASHRAE-T_p8 method to a 25-year operational period and to compare the design results related to different time horizon strategies. To this aim, the dimensionless temperature penalties have been compared against reference results obtained from g-functions pertaining to actual borehole field geometries. New optimized constants have been derived specifically for the ASHRAE-T_p8 method, facilitating its adaptation to the longer time frame of 25 years. The accuracy and reliability of this enhanced method have been extensively validated (at a 25-year time horizon, the average error is 3.8 % respect to the reference code). The findings of this study underscore the potential errors in total borefield length and borehole depth that could arise when applying the conventional 10-year design methodology to a 25-year horizon. On the other hand, the present study leads to deducing that the drilling costs due to a necessary higher borehole depth for a correct design, proper to a 25-year horizon, relatively increase (overall length can increase up to +16.8 %). The proposed methodology demonstrates wide applicability, providing a robust framework adaptable to various operational time frames.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"132 ","pages":"Article 103457"},"PeriodicalIF":3.5,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genesis and quantitative assessment of travertine precipitation in high-temperature geothermal system in Eastern Tibetan Plateau","authors":"Bin Li ,&nbsp;Yiman Li ,&nbsp;Zhonghe Pang ,&nbsp;Binbin Gao ,&nbsp;Tianming Huang","doi":"10.1016/j.geothermics.2025.103455","DOIUrl":"10.1016/j.geothermics.2025.103455","url":null,"abstract":"<div><div>It’s widely known that siliceous sinter always occurs in high-temperature geothermal system while travertine is mostly found in low-medium temperature geothermal system. This conventional knowledge provides some insights for us to assess the potential of geothermal resources based on the field investigations of geothermal fluid and surrounding precipitations. However, it’s not totally true for many high-temperature geothermal systems in Tibetan Plateau where widely distributed travertine could be found in the surface. This paper takes Riduo geothermal system in Eastern Tibetan Plateau as an example to discuss the genesis of geothermal fluid and travertine formation from high-temperature geothermal system using chemical and isotopic methods as well as geochemical modeling. Results showed that geothermal fluid of the study area is recharged by local precipitation and snow-melting water. During infiltration and circulation in the reservoir, dissolution of minerals of albite, microcline, gypsum and magnesite and precipitation of minerals of amesite(14A), daphite and illite lead to the formation of reservoir fluid. The reservoir fluid is established to be of HCO₃‧ SO₄_<img>Na‧ Ca type with pH of 5.56 and temperature of 200 °C ∼215 °C at reservoir conditions. When ascending along the faults, up to 80 % of shallow groundwater mixed with deep hot water and lead to the formation of surface hot spring of 77 °C ∼ 81 °C. Regional tectonic evolution leads to the deposition of carbonate-clastic rock of Duodigou Formation-Takena Formation and metamorphism due to high-temperature magmatism during the period of North-South trending rifts formation result in generation of substantial carbon and calcium sources for the geothermal fluid at reservoir conditions through direct recharge or water-rock interactions and become the matter sources for travertine, as evidenced by carbon isotope. Degassing of large quantities of CO₂ from deep geothermal fluid when it ascending to the surface change the carbonate species equilibrium and leads to oversaturation and precipitation of calcite. In addition, mixing of shallow cold groundwater with calcium and magnesium also contribute to the calcite precipitation. Thermodynamic simulation shows that the travertine precipitation rate is about 382 mg/kgs for Riduo geothermal system.</div><div>Because geothermal gas in most high-temperature geothermal systems in Tibet Plateau is dominated by CO₂ from metamorphism (70 vol.% on average and 97.4 vol.% for extreme case), degassing due to the CO₂ partial pressure differences between deep fluid and atmosphere will definitely cause calcite precipitation as travertine. Therefore, it’s concluded that the key controlling factor for travertine formation from many high temperature geothermal systems in Tibetan Plateau is loss of large quantities of CO₂ when ascending to the surface.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"132 ","pages":"Article 103455"},"PeriodicalIF":3.5,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental assessment of sustainable lithium extraction from geothermal reservoirs","authors":"Lucjan Sajkowski ,&nbsp;Rose Turnbull ,&nbsp;Jon Blundy ,&nbsp;Karyne Rogers","doi":"10.1016/j.geothermics.2025.103448","DOIUrl":"10.1016/j.geothermics.2025.103448","url":null,"abstract":"<div><div>The sustainable extraction of critical metals, including lithium, from geothermal fluids offers an environmentally responsible alternative to traditional mining practices, addressing the rising global demand for these materials. This study examines the interaction of reinjected geothermal fluids with rhyolite and pumice rocks from the Taupō Volcanic Zone under simulated geothermal reservoir conditions. Using a continuous-flow system capable of maintaining pressures up to 500 bar and temperatures up to 400 °C, we investigate the mechanisms and timescales of metal mobilization and the roles of fluid chemistry, temperature, and rock composition on timescales of 1 to 2 months. The reactant, reinjection fluid is silica-depleted, which enhances reaction rates with the silica-rich rocks. Product fluids from our experiments were analysed for a large number of major and trace elements and run product solids were characterised by SEM and XRD.</div><div>The results demonstrate that lithium release is significantly influenced by temperature, with elevated temperatures (&gt;200 °C) enhancing lithium mobilization through the devitrification of volcanic glass. At the end of each experiment, the total recovery (as a percentage of that originally in the rock) of lithium is 90 % for the pumice and 80 % for the rhyolite. The only other elements with significant (&gt;5 %) recovery rates are tungsten (29 % for rhyolite), cesium (100 % rhyolite), fluorine (59 % pumice; 11 % rhyolite), silver (30 % pumice) and germanium (40 % pumice; 100 % rhyolite). Some elements, notably antimony for both rhyolite and pumice, are quantitatively stripped from the reactant fluid, presumably into secondary minerals. Differences in behaviour between rhyolite and pumice for tungsten and cesium may reflect sequestering of these phases in secondary minerals, such as zeolites, in the pumice experiments. Secondary minerals did not sequester lithium in either of the experiments; its very high recovery rates probably reflect rapid diffusion through the silicate glass that operates at a faster rate than silicate glass breakdown. The study provides insights into fluid-rock interactions within volcanic geothermal reservoir rocks and highlights the ability of silica-poor reinjection fluids to enhance lithium extraction from the reservoir, a potential strategy for sustainable lithium extraction from geothermal systems.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"132 ","pages":"Article 103448"},"PeriodicalIF":3.5,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heterogeneous distribution of surface hydrothermal alteration in the Nevados de Chillán Fractured Geothermal System, Southern Andes","authors":"Camila López-Contreras ,&nbsp;Gloria Arancibia ,&nbsp;Valentina Mura ,&nbsp;Santiago Maza ,&nbsp;Diego Morata ,&nbsp;Philippe Robidoux ,&nbsp;John Browning ,&nbsp;David Healy ,&nbsp;John Singleton","doi":"10.1016/j.geothermics.2025.103454","DOIUrl":"10.1016/j.geothermics.2025.103454","url":null,"abstract":"<div><div>The spatial distribution of surface geothermal manifestations and hydrothermal alteration reflects the complex interplay of multiple factors controlling fluid circulation. This study aims to understand the different controls on the distribution of surface hydrothermal alteration, using the Nevados de Chillán Geothermal System (NChGS) as a case study. Lineament maps were created at 1:2500 and 1:5000 scales, and orientations of faults, fractures, and veins were measured. The pH measured ranges from 2.6 to 5.4. Surface temperature was measured and analyzed via Inverse Distance Weighted (IDW) interpolation in ArcGIS®. Surface hydrothermal alteration was mapped using drones, and minerals were identified through X-Ray Diffraction of whole rock and clay analysis, including chalcedony, opal, native sulfur, illite, kaolinite, iron oxides, sulfates, and hydrated sulfates. Illite crystallinity measured using the Full Width at Half Maximum index (FWHM) ranged from 0.05 to 1.77, while kaolinite crystallinity measuring using Aparicio-Galán-Ferrell index (AGFI), ranged from 0.73 to 1.15. The results show that the distribution of high temperatures (reaching 95 °C) and intense advanced argillic hydrothermal alteration is heterogeneous, controlled by lithological contact and the interaction between ∼E-W-trending lineaments associated with subvertical faults and NNW-striking surficial low-angle faults. Circulation of acid-sulfate waters rich in Fe, Al, and Cu occur primarily along fault/fracture networks, promoting the formation of high-crystallinity illite and kaolinite at the surface. This study proposes a link between surface geothermal manifestations with fault-fracture network and lithological controls within a fractured geothermal system in the Southern Andes.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"132 ","pages":"Article 103454"},"PeriodicalIF":3.5,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144694703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development and thermal performance analysis of modified vertical U-tube ground heat exchangers: Approaches to enhance the thermal performance","authors":"Nafisa Lubaba ,&nbsp;Fahim Tanvir ,&nbsp;Adrita Anwar ,&nbsp;Nahyan Ahnaf Pratik ,&nbsp;Md. Hasan Ali ,&nbsp;Ahbab Faiyaj Haque","doi":"10.1016/j.geothermics.2025.103456","DOIUrl":"10.1016/j.geothermics.2025.103456","url":null,"abstract":"<div><div>Ground Source Heat Pump (GSHP) systems are recognized as one of the most energy-efficient and environmentally sustainable solutions for heating and cooling applications. The core of GSHP systems is the Ground Heat Exchanger (GHE), which facilitates the transfer of thermal energy between the ground and a working fluid. The performance of GHEs plays a pivotal role in determining the overall efficiency of the system. Traditional GHEs often employ a constant-diameter U-tube design, which may not be optimal for maximizing heat transfer or minimizing pressure losses. This experimental study investigates the thermal performance enhancement of U-tube GHE through geometric modification. Three types of U-tube GHEs were installed in boreholes up to 20 m depth. The first configuration used a traditional constant-diameter U-tube (C-1). The second one (C-2) featured a larger diameter in the lower 10 m section and a smaller diameter in the upper 10 m section, while the third configuration (C-3) incorporated an asymmetric leg design with a smaller-diameter inlet pipe and larger-diameter outlet pipe. Three vertical GHE configurations were fabricated and tested under identical operating conditions, with an inlet fluid temperature of 303 K, a flow rate of 2 L/min and 72 h continuous operation period. To establish a reliable ground temperature profile, a monitoring hole was dug up to a depth of 10 m and T-type thermocouples were installed at different depths at the Khulna University of Engineering &amp; Technology (KUET) campus. Results showed that beyond 5 – 7 m depth, the ground temperature remained nearly constant, making it ideal for consistent thermal exchange. Average heat exchange rates of C-1, C-2 and C-3 are 10.59 W/m, 18.12 W/m and 14.53 W/m, respectively. Configuration C-2 achieved the highest rate, reflecting an improvement of approximately 70.8 % compared to C-1, while configuration C-3 achieved approximately 36.8 % improvement over C-1. To evaluate the combined impact of heat transfer rate and pressure drop, the Thermal Performance Capability (TPC) was calculated for the configurations. Among them, C-2 exhibited the highest overall thermal performance, achieving a maximum TPC value of 2.47. The higher value of TPC indicates that C-2 provides a favorable balance between enhanced heat exchange and associated pressure drop, thereby demonstrating superior thermal performance compared to the conventional configuration C-1. These findings demonstrate that geometric modification of GHEs significantly improves thermal performance. This study provides experimental insights into optimizing U-tube GHE design, offering a valuable pathway for enhancing the effectiveness of GSHP systems in future implementations.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"132 ","pages":"Article 103456"},"PeriodicalIF":3.5,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703602","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}