A fine-grained temperature monitoring system for sustainable geothermal boreholes

Ground source heat pumps offer a technology for the thermal conditioning of buildings which is both renewable and economically competitive against fuel-based solutions. However, in spite of the good performances already proved by several studies, the optimal operation and the long-term sustainability of a specific geothermal plant is always affected by a certain degree of uncertainty. The installation of accurate and stable temperature monitoring systems within geothermal boreholes would hence contribute significantly to increase the confidence towards this kind of technology. Unfortunately, existing temperature acquisition systems can be expensive and difficult to deploy, especially in small (i.e. domestic) plants. In this paper, first the general requirements of this kind of monitoring systems are described, in order to find a reasonable tradeoff between measurement accuracy and installation costs. Then, two different solutions, one based on Pt100 sensors, the other based on a more innovative 1-Wire® system are presented and compared. Finally, some meaningful experimental results are reported and commented.