Comparative analysis of Different Closed-loop Borehole Heat Exchanger Thermal Performance in shallow High-Temperature Environment

Comparative analysis of Different Closed-loop Borehole Heat Exchanger Thermal Performance in shallow High-Temperature Environment | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Comparative analysis of Different Closed-loop Borehole Heat Exchanger Thermal Performance in shallow High-Temperature Environment DAN AZIMI MOHAMAN, Monia Procesi, Eloisa Di Sipio, Giorgia Dalla Santa, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8927294/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Closed-loop geothermal systems offer a promising pathway for exploiting high geothermal gradients in volcanic environments while avoiding the operational and environmental risks associated with open-loop circulation. However, the influence of borehole trajectory and geometric configuration on the long-term thermal performance of such systems remains insufficiently constrained, particularly under shallow, high-temperature volcanic conditions. This study presents a systematic numerical comparison of five closed-loop borehole heat exchanger (CBHE) configurations: i) vertical coaxial (V-CBHE), ii) deviated coaxial (D-CBHE), iii) horizontal coaxial (H-CBHE), iv) U-loop (U-CBHE), and v) single-lateral (SL-CBHE), using geological and thermal conditions representative of Vulcano Island (Italy). A fully coupled 1D wellbore–3D formation thermo-hydraulic model was developed in a FEM commercial software to simulate conductive heat transfer and fluid circulation over a 25-year operational period. Sensitivity analyses were conducted to evaluate the effects of borehole geometry, inclination depth and angle, horizontal extension length, injection temperature, flow rate, and insulation strategies. Results demonstrate that borehole geometry exerts a dominant control on long-term performance, surpassing the influence of operational parameters. Lateral configurations significantly outperform vertical and deviated systems by extending heat-exchange length within high-temperature formations, increasing fluid residence time, and distributing thermal drawdown over a larger rock volume. After 25 years of continuous operation, horizontal, U-loop, and single-lateral systems stabilise at production temperatures of approximately 147–165°C, compared to 96–101°C for vertical and deviated configurations. Inner-pipe insulation effectively mitigates internal thermal short-circuiting, particularly during early operation. Although electrical power estimates represent idealised upper bounds, the relative performance ranking among configurations remains robust. These findings highlight trajectory design as a critical lever for optimising closed-loop geothermal systems in shallow, high-enthalpy volcanic environments. Closed-loop geothermal system Coaxial borehole heat exchanger Horizontal well multilateral well Heat transfer numerical modelling Renewable energy Island decarbonization Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8927294","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":596355863,"identity":"270dd377-779a-4b03-a7e8-dd883132e0c4","order_by":0,"name":"DAN AZIMI 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However, the influence of borehole trajectory and geometric configuration on the long-term thermal performance of such systems remains insufficiently constrained, particularly under shallow, high-temperature volcanic conditions. This study presents a systematic numerical comparison of five closed-loop borehole heat exchanger (CBHE) configurations: i) vertical coaxial (V-CBHE), ii) deviated coaxial (D-CBHE), iii) horizontal coaxial (H-CBHE), iv) U-loop (U-CBHE), and v) single-lateral (SL-CBHE), using geological and thermal conditions representative of Vulcano Island (Italy). A fully coupled 1D wellbore\u0026ndash;3D formation thermo-hydraulic model was developed in a FEM commercial software to simulate conductive heat transfer and fluid circulation over a 25-year operational period. Sensitivity analyses were conducted to evaluate the effects of borehole geometry, inclination depth and angle, horizontal extension length, injection temperature, flow rate, and insulation strategies. Results demonstrate that borehole geometry exerts a dominant control on long-term performance, surpassing the influence of operational parameters. Lateral configurations significantly outperform vertical and deviated systems by extending heat-exchange length within high-temperature formations, increasing fluid residence time, and distributing thermal drawdown over a larger rock volume. After 25 years of continuous operation, horizontal, U-loop, and single-lateral systems stabilise at production temperatures of approximately 147\u0026ndash;165\u0026deg;C, compared to 96\u0026ndash;101\u0026deg;C for vertical and deviated configurations. Inner-pipe insulation effectively mitigates internal thermal short-circuiting, particularly during early operation. Although electrical power estimates represent idealised upper bounds, the relative performance ranking among configurations remains robust. These findings highlight trajectory design as a critical lever for optimising closed-loop geothermal systems in shallow, high-enthalpy volcanic environments.\u003c/p\u003e","manuscriptTitle":"Comparative analysis of Different Closed-loop Borehole Heat Exchanger Thermal Performance in shallow High-Temperature Environment","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-26 03:44:29","doi":"10.21203/rs.3.rs-8927294/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"df57fb21-4eac-4b84-98ea-076a6761788d","owner":[],"postedDate":"February 26th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-06T09:43:02+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-26 03:44:29","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8927294","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8927294","identity":"rs-8927294","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}