Field behaviour of a flat panel ground heat exchanger

Abstract

An experimental plant has been devised to investigate the behaviour of a novel type of horizontal ground heat exchanger (GHX), aiming to improve the performance of ground-source heat pumps for space heating and cooling. The GHX system is composed by hollow flat panels, which have been installed edgeways in shallow trenches two meters deep in soil. The hydraulic closed loop and the surrounding soil have been equipped with several digital sensors to monitor the ground temperature distribution and the plant in real-time. The behaviour has been tested for two years in several operating carried out especially in summertime. The specific power of heat transfer for surface-unit achieves considerable values, and no over-heating conditions were measured at the soil surface. Moreover, the GHX showed to be able to involve a large soil volume, and this behaviour enables high energy performance, at least in cooling mode. After few months of inactivity, the natural ground heat transfer erased the memory of the energy exploitation carried out by the GHX. Thus, unlike with the vertical systems, long-term subsurface thermal energy build-up or depletion wouldn’t be expecting by shallow GHXs.