Two drilling techniques were developed: “enlarged easy drill” to install helicoidal Borehole Heat Exchangers (BHEs) at very shallow depth and “piling” to install co-axial BHEs.

A new drilling technique has been studied to optimize the easy-drill concept together with the heat baskets developed by REHAU. The large diameter of the heat basket implied to redesign of the drilling equipment. This new technology has been named the ‘enlarged easy drill’ due to the fact that the standard easy drill has been stretched to fit with the helicoidal BHEs.

Piling technique had been already conceived few years before CHEAP-GSHPs project. Such technique was further developed utilizing a rotating-vibrating drilling head coupled with water injection. Rotation is one of the key factors that helps to improve drilling in soils that were too hard to drill with the ‘old’ piling technique. Moreover water injection can reduce the friction between the tubes and the ground. Grouting is not necessary and casings are not needed since the external tube of the BHE acts as casing. Such improvements allows to reduce the drilling time by 30% compared with the conventional technique.