Estimation of Thermal Diffusivity from a Long-term Measurement of Sub-soil Temperature in Marrakech

The objective of this work is to predict the underground temperature that allow for performance evaluation of the low energy systems used for air cooling/heating in buildings. To this end, indirect measurement of the soil thermal diffusivity using a long-term measurement of soil temperature at different depths is conducted in a site located in Marrakech. These temperatures are measured at 0.4 m, 0.8 m, 1.6 m, 3.2 m and 6.4 m depths, during a period of 23 months that lasts from February 2017 to April 2019. The comparison between the in-situ measurements of the underground temperature with that calculated from the estimated soil thermal diffusivity shows a good match indicating the robustness of the estimation method. Indeed, the results show that, for a period of one year, the RMSE is varying in between 4.1 and 1.8 °C or 1.6 and 1.8 °C depending on the considered period of time.