Thermal performance analysis of a ground-coupled heat pump integrated with building foundation in summer

Geothermal energy has been provided to improve the energy performance of buildings with great support from the government in Korea. However, despite the many advantages of using a ground-coupled heat pump (GCHP) with geothermal energy, the high construction cost of the ground-coupled heat exchanger (GCHE) is the primary obstacle to prevent the supply and spread of GCHPs. In this study, in order to overcome the problems of the conventional GCHP, a GCHP integrated with a PHC (prestressed high-strength concrete) pile, which is used in the foundation of buildings, was introduced and its thermal performance was analyzed through experiments conducted in summer. To increase the thermal performance, a coil-type pipe was used. The PHC-pile-integrated GCHP was installed at a depth of 15 m. However, because it was installed in the beneath of the building, it was not largely affected by the outdoor temperature. The measured effective thermal conductivity was 3.69 W/m °C, which is similar to that of a conventional vertical GCHP. Also, the COP was determined to be 3.9-4.3, which is slightly lower than the conventional vertical GCHP. However, considering the fact that the expensive drilling cost could be mitigated by 83.7%, the thermal performances were satisfactory.