Energy Renovation Strategies for Office Buildings using Direct Ground Cooling Systems

Direct ground cooling systems (DGCS) can provide comfort cooling to buildings without the use of any refrigeration-based cooling methods. DGCS is an emerging technology, commonly used for new office buildings in cold climates. This study aims at evaluating the energy-saving possibilities of a DGCS compared to a conventional chiller system for an existing office building. A typical Swedish office building with a chiller-based cooling system and in need of an energy renovation is taken as a reference case. A range of possible renovation measures are applied on the building and the cooling system, and the results are evaluated in terms of borehole design and building energy demand. The results show that applying the DGCS substantially reduces the building’s purchased energy, as chiller electricity demand is eliminated. In addition, implementing the renovation measures to reduce the thermal demand of the building could further reduce purchased energy. The results suggest implementing the DGCS after performing the renovation measures. This may lead to a considerable reduction in the required borehole length and hence, the drilling costs. Results from this study provide useful inputs for designing boreholes in ground-coupled systems for new and existing office buildings.