A comparative study on borehole heat exchanger size for direct ground coupled cooling systems using active chilled beams and TABS

Research output: Contribution to journalArticle


Direct ground cooling is a method for cooling buildings whereby free cooling is provided by circulating water through borehole heat exchangers (BHEs). Since no refrigeration cooling is involved, supply water temperature to the building's cooling system is dependent mainly on BHE sizing. This study investigates the sizing of BHEs for direct ground cooling systems, with a particular focus on the influence of terminal unit types and their operating strategies. Experimental results using a direct ground-coupled active chilled beam (ACB) system are used to develop a simulation model for an office building. The model is also modified for thermally activated building systems (TABS). The simulation results show that using TABS instead of ACBs for a similar BHE reduced the ground peak hourly loads, resulting in a lower borehole outlet temperature. Resizing BHE depth to reach similar maximum borehole outlet temperatures according to the actual heat extraction rate from the cooling systems resulted in a significantly shorter BHE depth with TABS compared to ACBs. However, indoor temperature was generally warmer with TABS, due to their slower heat extraction rate from the room. The findings are practical for analysing the design and operation of BHEs for different types of terminal units.


  • Taha Arghand
  • Saqib Javed
  • Anders Trüschel
  • Jan Olof Dalenbäck
External organisations
  • Chalmers University of Technology
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Building Technologies


  • Active chilled beam, Borehole heat exchanger, Direct ground cooling, Free cooling, Geocooling, GeoTABS
Original languageEnglish
Article number110874
Number of pages12
JournalEnergy and Buildings
Publication statusPublished - 2021 Jun 1
Publication categoryResearch
Externally publishedYes

Bibliographic note

Funding Information: This work was financially supported by the Swedish Energy Agency (Energimyndigheten) through its E2B2 national research programme. The in-kind contribution of laboratory facilities by Swegon and Lindab is gratefully appreciated. We are particularly grateful to Håkan Larsson for his lab assistance. Valuable discussions with Carl-Ola Danielsson (Swegon) and Göran Hultmark (Lindab) are also acknowledged. Publisher Copyright: © 2021 The Author(s) Copyright: Copyright 2021 Elsevier B.V., All rights reserved.