Geothermal Heat Pump Plant Performance in a Nearly Zero-energy Building

On the behalf of reaching EU directive 2010/31/EU energy performance targets and fulfilling nearly zero-energy energy buildings (nZEB) requirements by the end of 2020, utilization of renewable energy sources becomes important. Renewable solar and ground energy can be efficiently utilized by a hybrid geothermal heat pump with a solar thermal storage, which is expected to yield high seasonal coefficient of performance (SCOP) making it attractive to consider in nZEB design. This numerical study investigates the impact of various ground heat exchangers and thermal storage options along with their possible combinations on heat pump plant heating/cooling performance in the design of commercial hall-type nZEB located in cold climate of Hämeenlinna, Finland. Components applied in a numerical study were energy piles, vertical boreholes (heat wells), solar collector and/or exhaust air heat as a thermal storage source. A whole year dynamic simulations were performed in IDA-ICE simulation environment, where detailed custom ground-source heat pump (GSHP) plants were modelled. Results revealed GSHP plant to be favorable heat source option in nZEB design. Application of thermal storage enabled to reduce energy piles field by more than two times. Proposed exhaust air thermal storage option performed highly efficient in comparison to solar thermal storage.