Assessments about soil temperature variation under censored data and importance for geothermal energy applications. Illustration with Romanian data

Abstract

The study presents an experimental research carried out to study the natural soil temperature variations and to determine the soil thermal diffusivity based solely on temperature measurements. The research was conducted for two locations in Romania: Cluj-Napoca on bare clay soil and Reghin on grass covered clay soil. It was proved that the design and methodology of the research can be successfully applied in any location. Based on a statistical analysis of the experimental data, a simple and precise mathematical model for natural temperature variation was identified for each location. An important particularity of the models is that for each parameter are presented specific ranges of variation and confidence intervals. To the best knowledge of the authors, this approach is unique in the scientific literature. Another particularity of the models is that it was obtained under censored data. The presented models are generally suitable for any depth up to 10 m. For both locations the soil thermal diffusivity was calculated with specific ranges of variation and confidence interval. The obtained results are of utmost importance for the evaluation of local soil thermal potential for geothermal energy applications.