The importance of surface air temperature fluctuations on long-term performance of vertical ground heat exchangers

Abstract

Ground source heat pump (GSHP) systems efficiently heat and cool buildings using geothermal energy accessed via ground heat exchangers (GHEs). The thermal performance of GHEs is usually studied with equivalent groups of linear heat sinks/sources or with more advanced numerical models. In most cases, in regions with common geothermal gradients, the ground temperature is assumed to be constant with depth, a simplification that is reasonable for typical borehole GHEs which are at least 50 m deep. However, the increasing use of piles (and other geo-structures) as GHEs, which are typically shallower than borehole GHEs requires a re-assessment of the thermal effects of the surface air temperature ..