Defining geoexchange extraction rates in the same geological environment for different borehole geometry settings – pilot results from the HAPPEN - HORIZON 2020 project

Scientific paper - Original scientific paper

• Title (croatian): Određivanje prinosa bušotinskih izmjenjivača različitih geometrijskih karakteristika u istome geološkom okruženju – rezultati pilot-projekta HAPPEN – HORIZON 2020
• Author: Tomislav Kurevija
• Author: Marija Macenić
• Author: Tea Sabolić
• Author: Dalibor Jovanović
• Author's institution: University of Zagreb; Faculty of Mining, Geology and Petroleum Engineering; (Department of Petroleum and Gas Engineering and energy)
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mining, Petroleum and Geology Engineering

Abstract (english)

Kindergarten Grdelin in the city of Buzet, Istria, Croatia, was chosen to undergo a deep retrofit of the current thermotechnical system, as a part of the HORIZON 2020 HAPPEN project1. The existing shallow spiral heat exchanger field is insufficient to cover heating loads of the building. Therefore, additional BHEs were drilled and completed to determine optimal borehole heat exchanger type within the same geological environment. Four BHEs, either single U (1U) or double U (2U), with different geometrical setting and depth were tested: BHE-1 (50 m, 2U DN32 ribbed), BHE-2 (75 m, 2U DN40 ribbed), BHE-3 (100 m, 2U DN32 smooth) and BHE-4 (150 m, 1U DN45 ribbed). A thermal response test (TRT) was performed to obtain the ground thermal properties. Furthermore, synthetic TRT curves were calculated to describe temperature response in the case of different heat pulses. This was done to determine heat extraction rates and the capacity of each BHE type, according to EN14511 norm. It was established that the BHE-4 is the optimal design for heating and cooling purposes on the selected site due to positive impact of the geothermal gradient, higher initial borehole temperature and a positive effect of the ribbed inner wall.

Abstract (croatian)

Zgrada dječjega vrtića Grdelin, smještena u gradu Buzetu, Istarska županija, odabrana je unutar HORIZON 2020 HAPPEN projekta za obnovu i dopunu termotehničkoga sustava grijanja i hlađenja. Postojeći sustav bušotinskih izmjenjivača nije dovoljan da pokrije potrebe za toplinskom energijom te je zaključeno da je potrebna izrada dodatnih bušotinskih izmjenjivača topline. Da bi se odredio optimalan tip bušotinskoga izmjenjivača u istome geološkom okruženju, izrađene su 4 bušotine različitih dubina te su opremljene bušotinskim izmjenjivačima različitih geometrijskih karakteristika: BHE-1 (50 m, 2U DN32 žljebasta), BHE-2 (75 m, 2U DN40 žljebasta), BHE-3 (100 m, 2U DN32 glatka) i BHE-4 (150 m, 1U DN45 žljebasta). Test toplinskoga odaziva (TRT) izveden je na svim četirima bušotinama te su određena toplinska svojstva tla. Nadalje, simulacijom toplinskoga step-testa dobiveni su temperaturni odazivi pomoću kojih su određeni prinosi za pojedini bušotinski izmjenjivač. Zaključeno je da je BHE-4 izmjenjivač (150 m, 1U DN45 žljebasta), s obzirom na pozitivan utjecaj geotermalnoga gradijenta, više početne, statičke, temperature tla i pozitivnoga utjecaja žljebaste cijevi, onaj koji se pokazao kao optimalan izbor na lokaciji. Prinos svih testiranih bušotinskih izmjenjivača prema normi EN14511 i ulaznoj temperaturi 0 °C iznosi 18,8 kWt te 23,5 kWt pri vršnim uvjetima.

• Keywords (english): borehole heat exchanger; geological environment; geothermal gradient; heat extraction rates
• Keywords (croatian): bušotinski izmjenjivači topline; geološko okruženje; geotermalni gradijent; određivanje toplinskoga prinosa
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Rudarsko-geološko-naftni zbornik
• Numbering: vol. 36, no. 3, pp. 99-113
• e-ISSN: 1849-0409
• DOI: https://doi.org/10.17794/rgn.2021.3.7
• URN:NBN: urn:nbn:hr:169:749702
• Publication: 2021
• Document URL: https://hrcak.srce.hr/259510
• Type of resource: Text
• Access conditions: Open access
• Created on: 2021-09-13 10:36:33