Performance evaluation of a homemade cylindrical basket heat exchanger, by a multi-sensors monitoring campaign

Very Shallow Geothermal Systems (vSGS) can be economic attractive, even in case they do not present high efficiency, when excavation and realisation costs are significantly lowered by on-site construction and management; a typical case is the rural environment, where necessary equipment is usually already owned by final users and customers. Up to date, in contrast with the increasing utilisation, a wide scientific literature on the performance of vSGS does not exist, presumably because of their “plug-and-play” nature and relatively low efficiency. In fact, these systems can be object of high improvements, too, firstly by an increased knowledge of thermal interaction among underground, baskets and ambient temperature wave, and the consequent variations following seasonality and building energy demands. The paper presents the results of an experimental monitoring campaign on a homemade cylindrical geothermal basket, which will be connected to an underground cellar, for improving thermo-hygrometric comfort of wine. The vSGS and the monitoring system (composed by a set of underground temperature sensors and a dedicated Micro-Thermal Response Test machine M-TRT) have been realised entirely in-house, without accessing to commercial products. Through a 3D displacement of sensors inside and outside the basket, it has been possible to determine the entire thermal behaviour of the geo-exchanger, subjected to different thermal pulses and to changing climate. Finally, it has been possible to determine a range of costs for such in-house installations, when local conditions allow an easy and efficient on-site realisation.