Design optimization of the borehole system for a plus-energy kindergarten in Oslo, Norway

This paper presents the case study of a newly constructed 1600 m 2 kindergarten building in Oslo, Norway. The building has been designed within the framework of the Norwegian Research Council Project LowEx, which aims at engineering solutions to achieve a seasonal coefficient of performance (SCOP) of 6–10 for heating, a seasonal energy efficiency ratio (SEER) of 80–100 for cooling, and an 80% reduction in the purchased electric energy for heating and cooling of the buildings. Several architectural and technical measures have been implemented in the case study building to meet these requirements. This paper first provides an account of the design measures implemented in the building to achieve the ambitious energy performance targets. It then focuses on the design of the ground source heating and cooling system for the building and presents the preliminary design of the borehole system to provide low-temperature heating and high-temperature cooling to the kindergarten. The possibility of improving the borehole system design by optimizing the solar heat gains through the building envelope to balance the ground thermal loads is explored next. Finally, the effect of uncertainties in the design input values of ground thermal conductivity, effective borehole thermal resistance, and undisturbed ground temperature on the final design of the borehole system is evaluated.