Geothermics最新文献

{"title":"Gas equilibrium in the H2O-H2-CO2-CO-CH4 system for wet-steam geothermal-well fluids and their sources: A case study from Krafla, Iceland","authors":"Giulio Bini ,&nbsp;Matteo Lelli ,&nbsp;Stefano Caliro ,&nbsp;Tullio Ricci ,&nbsp;Anette K. Mortensen ,&nbsp;Ásgerður K. Sigurðardóttir ,&nbsp;Alessandro Santi ,&nbsp;Antonio Costa","doi":"10.1016/j.geothermics.2025.103322","DOIUrl":"10.1016/j.geothermics.2025.103322","url":null,"abstract":"<div><div>Equilibrium in the H₂O-H₂-CO₂-CO-CH₄ gas system has been extensively applied to fumarole data for geothermal exploration and volcano monitoring. However, little is known about its application to two-phase (vapor and liquid) geothermal well fluids, which can show an excess of enthalpy. Here, we applied the H₂O-H₂-CO₂-CO-CH₄ gas indicators to two-phase geothermal well discharges from the Krafla geothermal system, Iceland, to estimate aquifer temperatures and identify secondary processes during resource exploitation. Results suggest that the Krafla resource is drawn from a deep (approximately between –500 and –1,600 m a.s.l.), two-phase aquifer with temperatures ranging from 272 to 320 °C and vapor fractions between 0.26 and 0.93, explaining the excess enthalpy observed in well fluids. These estimates align with the temperatures of the main production zones of geothermal wells, whereas solute geothermometers (SiO₂ and Na/K) appear to record lower temperatures of minor, shallower, liquid aquifers. Wells with liquid-like enthalpy are sourced from the two-phase aquifer but are also influenced by water reinjection or downflows from a colder, shallower aquifer, consistent with the isothermal zone extending approximately between 400 and –900 m a.s.l. in Leirbotnar and Vesturhlíðar subfields. Water isotopes indicate the main aquifer is recharged by meteoric and reinjection fluids. Excess-enthalpy discharges show an influx of Ar- and N₂-rich vapor, with depleted ⁴⁰Ar/³⁶Ar and δ¹⁵N values, suggesting fractionations of atmospheric gases dissolved into the reservoir liquid. On the other hand, δ¹³C_CO2 and ³He/⁴He values point to a mantle origin, despite the lower δ¹³C_CO2 and P_CO2 levels that reflect a degassed magma (i.e., a noneruptive phase). These findings underscore the usefulness of the H₂O-H₂-CO₂-CO-CH₄ gas system and isotopic methods in tracking geothermal reservoir temperatures, their sources, and secondary processes, such as water reinjection or downflows from shallower aquifers.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"130 ","pages":"Article 103322"},"PeriodicalIF":3.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143644817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heat extraction performance and techno-economic analysis of a deep U-type borehole heat exchanger under intermittent operation","authors":"Chao Huan ,&nbsp;Fei Meng ,&nbsp;Zhengna Yang ,&nbsp;Wanlong Cai ,&nbsp;Zhihua Wang ,&nbsp;Fenghao Wang ,&nbsp;Chaofan Chen","doi":"10.1016/j.geothermics.2025.103307","DOIUrl":"10.1016/j.geothermics.2025.103307","url":null,"abstract":"<div><div>The deep U-type borehole heat exchanger (DUBHE) has been extensively investigated in terms of its long-term heat extraction capacity and economic feasibility. In this work, a 3D numerical model of DUBHE was established based on the open-source numerical software OpenGeoSys (OGS). Three- and sixty-day experimental data from two pilot projects in Xi’an, China, were used for the model validation. Subsequently, the model was extended to the long-term operational period by introducing different operation-shutdown ratios. In the long-term operation, the extension of the daily operational time from 8 to 24 h resulted in a reduction of the soil temperature difference from 14.87<!--> <!-->°C to 7.51<!--> <!-->°C. Compared to the continuous operational scenario with an operation-shutdown ratio of 24:0, the total heat extraction for operation-shutdown ratios of 8:16, 12:12, and 16:8 was discovered to be 65.15<!--> <!-->%, 76.14<!--> <!-->%, and 84.85<!--> <!-->%, respectively. Considering the system’s initial investment and the operational costs coupled with the heat pump and circulating water pump, a techno-economic analysis was also executed based on benchmark parameters. For the DUBHE heating system with an operation-shutdown ratio of 8:16, the investment payback period is approximately 8.2 years, which is the shortest among all scenarios. The related suggestions proposed in this work aim to provide insightful references for engineers and decision-makers in practice.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"130 ","pages":"Article 103307"},"PeriodicalIF":3.5,"publicationDate":"2025-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143629422","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":"Assessment of geothermal waters in Yunnan, China: Distribution, quality and driving factors","authors":"Zhaojun Zeng ,&nbsp;Li Yang ,&nbsp;Yueju Cui ,&nbsp;Xiaocheng Zhou ,&nbsp;Miao He ,&nbsp;Yuwen Wang ,&nbsp;Yucong Yan ,&nbsp;Bingyu Yao ,&nbsp;Xiaojing Hu ,&nbsp;Weiye Shao ,&nbsp;Jian Li ,&nbsp;Hong Fu","doi":"10.1016/j.geothermics.2025.103323","DOIUrl":"10.1016/j.geothermics.2025.103323","url":null,"abstract":"<div><div>Geothermal energy is a vital renewable resource widely used for various applications, including drinking water, domestic supply, irrigation, and industrial purposes. However, the utilization of geothermal water for drinking can expose individuals to toxic elements, particularly arsenic, which poses significant health risks. Despite the growing interest in geothermal water, there has been a lack of systematic analysis regarding the spatial variability of its quality and health risk. This study aims to address this gap by evaluating the spatial variability of the water quality characteristics and health risks in Yunnan Province using a combination of hydrochemical and isotopic methods, Principal Component Analysis (PCA), Self-Organizing Maps (SOM) and integrated tools such as Water Quality Index (WQI) and Human Health Risk Assessment (HHRA). According to this study, atmospheric precipitation serves as the primary recharge source with Na-HCO₃, Ca-HCO₃, Na-Cl and Ca-Cl as the dominant geothermal water hydrochemical in Yunnan Province. While most samples exhibit good water quality, those from the northwestern regions (e.g., Lijiang, Lincang, Kunming, Baoshan, Jinghong, Pu'er, and Dali) show poorer water quality and significant health risks. PCA analysis reveals that the spatial variability of geothermal water quality is largely influenced by deep hydrological cycles and magma-tectonic interactions, resulting in arsenic enrichment in high-risk areas. This study addresses the research gap regarding the spatial variability of geothermal water quality and health risk assessment in Yunnan Province and provides a scientific foundation for sustainable development and management.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"130 ","pages":"Article 103323"},"PeriodicalIF":3.5,"publicationDate":"2025-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143629421","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":"Design of silica nanoparticle tracers with optimized dispersion stability, sorption and deposition properties based on (X)DLVO and filtration theory","authors":"Laura Spitzmüller ,&nbsp;Jonathan Berson ,&nbsp;Thomas Kohl ,&nbsp;Thomas Schimmel ,&nbsp;Fabian Nitschke","doi":"10.1016/j.geothermics.2025.103309","DOIUrl":"10.1016/j.geothermics.2025.103309","url":null,"abstract":"<div><div>Functional nanoparticles emerged as potential new tracers for geoscientific applications, such as geothermal reservoir exploration. In this study, optimization strategies based on DLVO, extended DLVO (XDLVO) and filtration theory are presented. Our results show that nanoparticle material should have a low Hamaker constant, making metallic nanoparticles unfavorable. To ensure dispersion stability and minimize sorption on commonly negatively charged reservoir minerals, the nanoparticles should exhibit ζ-potentials below -30 mV. Decreasing the size of nanoparticles increases the diffusion-driven collisions with minerals grains and the probability of deposition while keeping the particle-to-grain size ratio below 0.008 prevents size exclusion effects. The impact of gravity on particle deposition is negligible for nanoparticles, making higher-density nanoparticle tracers viable. Experimental findings and XDLVO theory confirm the applicability of surface modifications to form a steric barrier that lowers attachment efficiencies while increasing colloidal dispersion stability. The impact of temperature cannot be assessed in a straightforward manner as it depends on multiple factors that can have contradicting effects. The presented study can serve as a guideline for the design of stable nanoparticle tracers with predictable transport properties in reservoirs. It shows that selecting appropriate materials, adapting ζ-potentials or employing effective surface modifications are key strategies to improve the performance of engineered nanoparticle tracers for geothermal exploration.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"130 ","pages":"Article 103309"},"PeriodicalIF":3.5,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143621428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal waters in the central part of Baikal Rift Zone: Hydrogeochemistry and geothermometry (Republic of Buryatia, Russia)","authors":"E.V. Zippa ,&nbsp;A.V. Ukraintsev ,&nbsp;M.K. Chernyavskii ,&nbsp;I.A. Fedorov ,&nbsp;V.A. Poturay ,&nbsp;E.V. Domrocheva ,&nbsp;N.A. Mukhortina","doi":"10.1016/j.geothermics.2025.103317","DOIUrl":"10.1016/j.geothermics.2025.103317","url":null,"abstract":"<div><div>The thermal waters of the Central Baikal Rift Zone are considered in this manuscript. The measured temperatures ranged from 19.8 to 75.6 °C. It was obtained that the studied waters are fresh (TDS 273–941 mg/L), generally weak alkaline and alkaline, enriched with Na⁺ (77–263 mg/L), SO₄^2- (70–489 mg/L), F^- (3.4–19.9 mg/L) and SiO₂ (54–118 mg/L) and depleted in Ca²⁺ (4.65–44.91) and Mg²⁺ (0.01–0.93 mg/L). The thermal springs mainly belong to SO₄-Na and HCO₃-SO₄-Na chemical types. SO₄-Na chemical type was characterized by dominant N₂ (89.61–92.20 vol. %) in gas composition, HCO₃-SO₄-Na type – with N₂ (10.72–57.23 vol. %) and CH₄ (37.76–71.43 vol. %) predominant gases. The two groups of springs were selected in accordance with TDS, SO₄^2-, HCO₃^-+CO₃^2-, Ca²⁺ and Na⁺. Likewise, the geochemical features of the thermal waters were identified. It was shown that more alkaline waters have lower pH; TDS forms due to SO₄²- and Na⁺ accumulation; Cl^- and HCO₃^-+CO₃^2- increased simultaneously, unlike SO₄^2-. Furthermore, F^- and SiO₂ also increased with pH and temperature, along with a decrease in Ca²⁺. It was assumed that the thermal waters enriched or depleted in chemical elements depending on the water-rock interaction processes (minerals dissolution/precipitation) and the duration of the water residence in the host rocks. This was illustrated by Cl^-/(Cl^- + HCO₃^-) diagram and calculation of ions ratios Na/Cl, HCO₃/Cl, Ca/Na, Ca/Mg, Ca/Cl, K/Cl and Mg/Cl. In addition, the reservoir temperatures were estimated using various geothermometers and geoindicators, including the Si-enthalpy diagram. The silica-enthalpy mixing model indicated mixing process only for 7 thermal springs. The analysis of estimated reservoir temperatures using various methods showed that the Si- and K/Mg- geothermometer are more reliable for the studying waters.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"130 ","pages":"Article 103317"},"PeriodicalIF":3.5,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143621429","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":"Detection and constraints of geothermal latent heat zones under the complex terrain of the Western Sichuan Plateau: A fusion of multi-source temporal remote sensing data","authors":"Ben Dong ,&nbsp;Bo Li ,&nbsp;Rongcai Song ,&nbsp;Haiwen Chen ,&nbsp;Yingchun Wang","doi":"10.1016/j.geothermics.2025.103287","DOIUrl":"10.1016/j.geothermics.2025.103287","url":null,"abstract":"<div><div>Geothermal energy is a sustainable and renewable resource with significant potential, particularly in regions with complex topography, such as high plateaus. However, accurately detecting geothermal anomalies in these areas presents challenges due to the influence of topographic factors and the resolution limitations of remote sensing data. To address these challenges, this study proposes a novel method that integrates multi-source and multi-temporal remote sensing data. The method leverages the high temporal resolution of MODIS, the high spatial resolution of Landsat 8, and topographic parameters derived from ALOS data. By combining dynamic multi-temporal thresholding and topographic correction, the approach effectively distinguishes geothermal signals from pseudo-thermal anomalies induced by solar radiation. The results demonstrate that the integration of multi-source remote sensing data enables the accurate identification of fine-scale thermal anomalies, consistent with the regional tectonic heat-control mechanisms. Topographic factors, including slope, aspect, and hillshade, are shown to significantly influence the spatial distribution of surface temperature. Following topographic correction, the model eliminates 36 %–45 % of pseudo-thermal anomaly areas, with high validation accuracy against actual hot spring locations. These findings underscore the critical importance of topographic correction in geothermal anomaly detection. By effectively reducing false thermal anomalies and enhancing the precision of geothermal zone identification, this integrated approach improves the applicability of remote sensing techniques for geothermal exploration. Furthermore, it provides a robust framework for assessing sustainable energy resources in regions with complex terrain.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"130 ","pages":"Article 103287"},"PeriodicalIF":3.5,"publicationDate":"2025-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143578585","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":"Investigation into the influence of multiple factors on the buried pipes clusters system based on similarity theory","authors":"Jing Wang ,&nbsp;Zongwei Han ,&nbsp;Yunsheng Chang ,&nbsp;Chunming Shen","doi":"10.1016/j.geothermics.2025.103305","DOIUrl":"10.1016/j.geothermics.2025.103305","url":null,"abstract":"<div><div>In rural areas, the building volume is small and geothermal energy is abundant. As a crucial medium of the development of shallow geothermal energy, identifying the factors influencing buried pipes can provide a reliable reference for the operation of rural ground source heat pump systems. To explore this question, a sand box test bench was constructed based on similarity theory and nine tests were designed using orthogonal theory. The orthogonal results showed that the <em>F</em> values of inlet temperature, operation mode, circulating flow rate and the quantities of buried pipes were 8.30, 1.71, 0.10, 0.01 in order for heat transfer capacity; the <em>F</em> values of these factors were 19.24, 0.32, 0.38, 0.05 in order for total heat transfer amount. The temperature difference between the inlet temperature and the soil temperature was positively related to heat transfer amount, moreover, the thermal performance was significantly higher during intermittent operation compared to partial intermittent operation. The temperature difference between the inlet and outlet of buried pipes reached 0.6 °C under intermittent operation, which was greater than the 0.15 °C observed under partial intermittent operation. This study provides valuable insights for the development of shallow geothermal energy systems.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"130 ","pages":"Article 103305"},"PeriodicalIF":3.5,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143578584","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":"Petrogenesis and comprehensive thermal assessment of the Dikili-Bergama region, western Anatolia","authors":"Tolga Ayzit ,&nbsp;Selçuk Erol ,&nbsp;Alper Baba","doi":"10.1016/j.geothermics.2025.103306","DOIUrl":"10.1016/j.geothermics.2025.103306","url":null,"abstract":"<div><div>Various methods are available to evaluate the thermal properties and energy potential of geothermal fields. The heat flow method is crucial for thermal modeling and understanding geological evolution. It helps to assess the impact of geological formations on various processes, including hydrocarbon generation and structural modeling. This study focuses on the Dikili-Bergama geothermal region and presents heat flow trends based on thermal modeling. The analysis of volcanic rock petrogenesis data and a thermal model are presented based on data from deep and shallow boreholes. The geothermal gradient is found to vary between 66.28 °C km^-1 and 121.68 °C km^-1, according to the interpolated data. Additionally, the study investigates the geochemical and lithological properties of magmatic rocks in the Dikili-Bergama region. The Kozak pluton group's has been measured to have radioactive heat production of up to 7.4 μWm^-3. Thermal conductivity properties and correlations, along with heat flow assessment, contribute to the understanding of geothermal potential. The mean dry thermal conductivity of the rocks in the study area is 2.33 Wm^-1K^-1. The data for the terrestrial heat flow and the radioactive heat flow values are up to 200 mWm^-2. The integration of 3D geological models and thermal models has highlighted the south western area of the study as a promising location for unconventional geothermal operations.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"129 ","pages":"Article 103306"},"PeriodicalIF":3.5,"publicationDate":"2025-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143562122","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":"Syn- to post-rift thermal evolution of the Pechelbronn sub-basin (Upper Rhine Graben)","authors":"Tchang-Tchong Laurie ,&nbsp;Michels Raymond ,&nbsp;Beccaletto Laurent","doi":"10.1016/j.geothermics.2025.103296","DOIUrl":"10.1016/j.geothermics.2025.103296","url":null,"abstract":"<div><div>The Upper Rhine Graben (URG) is a key target for geothermal projects in Western Europe, requiring an understanding of the development and spatial evolution of geothermal fluids. Its thermal and geological history was impacted during the Neogene period by a major change in rift kinematics, evidenced by a regional-scale and gradual erosive unconformity and coeval volcanic activity. This study investigates the interplay between URG syn- and post-rift burial history and heat flow evolution in the westerly Pechelbronn sub-basin - hosting petroleum and geothermal fields – in comparison to the more central Rastatt Trough. The method uses thermal maturity assessment by vitrinite reflectance and 2D burial coupled to conductive thermal modelling. Results reveal that the maximum burial occurs during the Aquitanian (post-rift), and that the maximum cumulative sediment thickness related to the Neogene erosion was approximately 1200 m in the Pechelbronn sub-basin, from the top of the Schistes à Poissons (Rupelian shale) to the Aquitanian sediments. Toarcian source rock (Schistes carton) reached the oil window at 29–28 Ma within the Pechelbronn sub-basin and at 43 Ma for the Rastatt Trough at Roeschwoog well. The comparison of current adjacent local heat anomalies reveals variations in thermal history of the Pechelbronn sub-basin, highlighting the dominant influence of syn-rift burial in some areas, e.g. in Soultz-sous-Forêts or additional heat input attributed to geothermal fluids in others, e.g. in Rittershoffen. Moreover, it appears that the heat flow must have been considerably higher (around 180 mW/m², under the pure conduction hypothesis) during faults activation around 15 Ma in the Rittershoffen area, compared to Soultz-sous-Forêts (150 mW/m²). Changes in local heat flows are attributed to east-west migration of hydrothermal cells positions through time in relationship to fluid circulation at basin scale. These results provide a broad geological time frame for further thermal modeling in the URG and provide new insights into the thermal evolution of the URG and its implications for sub-surface resources exploration.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"129 ","pages":"Article 103296"},"PeriodicalIF":3.5,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143550612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental study on the thermo-mechanical behavior of steel pipe energy pile groups with and without phase change material","authors":"Hong Chang ,&nbsp;Xing Wu ,&nbsp;Yuan Du ,&nbsp;Zhaoxuan Wang ,&nbsp;Huicheng Jiang ,&nbsp;Huang Zhao ,&nbsp;Yu Zhang ,&nbsp;Yunli Gao ,&nbsp;Zhengheng Gan","doi":"10.1016/j.geothermics.2025.103304","DOIUrl":"10.1016/j.geothermics.2025.103304","url":null,"abstract":"<div><div>Energy piles have attracted global interest as a low-carbon, environmentally friendly and cost-effective underground energy structure. However, there were fewer studies on the thermo-mechanical behavior of steel pipe energy pile groups. The thermo-mechanical behavior of steel pipe concrete energy pile groups (SPEPG) and steel pipe phase change concrete energy pile groups (SCEPG) have been analyzed and compared by means of an indoor model test under thermal imbalance cycles (heating with different amplitude than cooling). The results indicated that by the third heating phase, the heat exchange power of the SCEPG stabilized at 73.3 W, which was 16% higher than that of the SPEPG. During the cooling phase, the heat exchange power of the SCEPG was stable at 96.7 W, which was 18% higher than that of the SPEPG. Furthermore, the average heat exchange efficiency of each pile in the pile group was lower than that of a single pile, with the maximum heat exchange power occurring when the pile spacing was four times the pile diameter. In terms of mechanical performance, the maximum thermally induced stress applied to the SPEPG and SCEPG were 485.0 kPa and 441.3 kPa, respectively, accounting for 2.3% and 2.1% of the design tensile strength of the steel pipe pile. The pile head displacement of the steel pipe energy pile groups was primarily determined by the displacement after the first cycle, and the accumulation rate of pile head displacement decreases as the number of cycles increases. After three cycles, the pile head displacement of the SCEPG decreased by 9.1% compared to that of the SPEPG. This study provides a reference for the application of steel pipe energy pile groups with and without phase change material in hot climate regions.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"129 ","pages":"Article 103304"},"PeriodicalIF":3.5,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143550611","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}