Effect of Microbially Induced Calcite Precipitation on soil thermal conductivity

Energy piles efficiency is strongly affected by soil saturation conditions: low water contents considerably decrease their performance thus limiting the possibility to extend their application in arid environments. This paper investigates the MICP (Microbially Induced Calcite Precipitation) technique as a potential means of enhancing the soil-pile heat exchange rates by improving soil thermal properties. The study puts the focus on measuring the thermal conductivity of untreated and treaded sand at various degrees of saturation. Experimental results clearly show a significant improvement of the thermal conductivity of the soil especially for low degrees of saturation. This enhancement is attributed to the mineralized calcite crystals acting as “thermal bridges” between the soil grains, offering larger surfaces for heat exchanges compared to the untreated material where exchanges occur via smaller contact points.