Temperature evolution around four laboratory-scale borehole heat exchangers grouted with phase change materials subjected to heating–cooling cycles: An experimental study

This article presents the experimental results from a unique laboratory test-setup used to comparative study of heat transfer conditions in borehole heat exchangers with different grouts under a controlled environment. The work was part of a larger, EU-funded project on advanced materials for boreho...

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Bibliographic Details
Published in:	Journal of energy storage Vol. 74; p. 109302
Main Authors:	Žirgulis, Giedrius, Javadi, Hossein, Chaudhari, Ojas Arun, Ghafar, Ali Nejad, Fontana, Patrick, Sanner, Burkhard, Urchueguía, Javier F., Badenes, Borja, Castell, José Manuel Cuevas, Shuster, Michael
Format:	Journal Article
Language:	English
Published:	Elsevier Ltd 25-12-2023
Subjects:	Borehole heat exchanger Cyclic heating High thermal conductivity grout Phase-change material Shallow geothermal energy Cyclic heating Shallow geothermal energy High thermal conductivity grout Borehole heat exchanger Phase-change material Cooling Mortar Shape stabilized phase change material Geothermal energy Boreholes Test setups Phase change materials Borehole heat exchangers Shallow geothermal energies Temperature evolution Grouting Thermal conductivity Laboratory test Heating-cooling cycle High thermal conductivity
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Summary:	This article presents the experimental results from a unique laboratory test-setup used to comparative study of heat transfer conditions in borehole heat exchangers with different grouts under a controlled environment. The work was part of a larger, EU-funded project on advanced materials for borehole heat exchangers pipes and grout, GEOCOND. Four grout columns with different formulations were cast and tested under cyclic heating and cooling. One grout column was cast using high thermal conductivity grout; two columns were cast from high thermal conductivity grout with microencapsulated phase change material (MC-PCM) and one with shape-stabilised phase-change material (SS-PCM). The objective of the test was to comparatively evaluate performance of the borehole heat exchanger under a cyclic temperature regime and to investigate if the selected phase change materials (PCM) embedded in grout can be activated by cyclic heating and function steadily. Twenty-five heating-cooling cycles were performed, each lasted 24 h. The results showed clear cooling delay in grouts containing PCM associated with the crystallization heat release. The cooling delay was better expressed in grouts with SS-PCM. The PCM related cooling delay was stable throughout all the cycling in SS-PCM containing grouts, however, the effect vanished in grouts with MC-PCM. •Role of phase change materials embedded in the grouting of a geothermal heat exchanger were tested using a unique test bench.•The rig had a box wall cooling system that effectively equalised the temperature in the sand around the grout columns.•PCM thermal activity was observed, expressed as a time delay of temperature increase on heating and temperature decrease on cooling.
ISSN:	2352-152X 2352-1538 2352-1538
DOI:	10.1016/j.est.2023.109302