Study of Borefield Connection Configurations in Single-Pipe District Geothermal Heating and Cooling Systems Using a Simulation Test Bed
Single pipe geothermal district heating and cooling networks (GDHCN) operate with ambient loop temperatures to provide service fluid to multiple buildings while using the soil as a heat source or heat sink. This work investigates single-pipe GDHCN configurations using a simulation test bed. The network connects three buildings with distinct load profiles: balanced, heating-dominant, and cooling-dominant. An appropriately sized bore field is designed for each building. Two sizing strategies were tested: individual sizing based on peak loads and integrated sizing using net system load. Performance metrics include annual electricity consumption and peak power demand of heat pumps under varying layouts, including even-spaced pairs (each bore field placed downstream of its building), partial clustering (two buildings grouped with their respective bore fields) and complete clustering (all three buildings grouped with their bore fields). Results show that the studied configuration changes have negligible impact on total system energy use, with annual consumption differences below 1%. However, building-level performance varies slightly due to upstream loads affecting entering fluid temperature and seasonal COP trends. Bore field sizing based on the system net load reduced total drilling depth by 42% without significant performance penalties, indicating potential for cost reduction. These findings suggest that while configuration alone does not substantially influence system-wide energy performance (up to 0.4% difference among different configurations), it may affect individual building efficiency (up to 1.5% difference) and become more critical in larger or less balanced networks. Future research should examine variable-speed pump control, expanded network topologies, and economic implications under diverse load conditions.