Transparent Soil to Model Thermal Processes: An Energy Pile Example

Managing energy resources is fast becoming a crucial issue of the 21st century, with ground-based heat exchange energy structures targeted as a viable means of reducing carbon emissions associated with regulating building temperatures. Limited information exists about the thermo-dynamic interactions of geothermal structures and soil owing to the practical constraints of placing measurement sensors in proximity to foundations; hence, questions remain about their long-term performance and interaction mechanics. An alternative experimental method using transparent soil and digital image analysis was proposed to visualize heat flow in soil. Advocating the loss of optical clarity as a beneficial attribute of transparent soil, this paper explored the hypothesis that temperature change will alter its refractive index and therefore progressively reduce its transparency, becoming more opaque. The development of the experimental methodology was discussed and a relationship between pixel intensity and soil temperature was defined and verified. This relationship was applied to an energy pile example to demonstrate heat flow in soil. The heating zone of influence was observed to extend to a radial distance of 1.5 pile diameters and was differentiated by a visual thermal gradient propagating from the pile. The successful implementation of this technique provided a new paradigm for transparent soil to potentially contribute to the understanding of thermo-dynamic processes in soil.