The design and performance of a geothermal heat pump system using horizontal sub-slab ground coils

Conference · Thu Jul 01 04:00:00 EDT 1999

OSTI ID:20030604

Jensen, J; Den Braven, K

The most significant disadvantage of geothermal or ground-coupled heat pumps (GHPs or GCHPs) is the relatively high cost of installing the ground coil. Installation costs can be reduced by effectively utilizing the soil under slab floors in residential installations, taking advantage of the excavation required for the house foundation and other features. A GHP system with six ground coils was installed in a residence on Lake Coeur d'Alene in northern Idaho. Four horizontal sub-slab ground coils were installed beneath the slab floor of the house and garage. Another ground coil was wrapped around the residential septic tank. A sixth coil was placed in a trench outside the basement wall in a spiral-coiled configuration. The primary purpose of this research was to design and install a geothermal heat pump system using different designs of horizontal sub-slab coils, and to compare the performance of the different types of coil placement. Coils that are placed deeper and/or contacting a greater volume of soil tend to have better performance than those which have shallow placement or are in contact with a smaller amount of soil. The below grade basement sub-slab coils and foundation spiral-coil loop consistently absorbed more energy during the heating season and rejected more heat during the cooling season compared to the garage and septic coils.

• Research Organization: Univ. of Idaho, Moscow, ID (US)
• OSTI ID: 20030604
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
COMPARATIVE EVALUATIONS
DESIGN
GROUND SOURCE HEAT PUMPS
IDAHO
INSTALLATION
PERFORMANCE
PIPES