Abstract
Thermal energy storage in compacted soils can be considered as a new economically efficient and environmentally friendly technology in geotechnical engineering. Compacted soils are usually unsaturated; therefore, reliable estimates and measurements of their thermal properties are important in the efficiency analysis of these structures. In this study, a method is used to estimate the thermal properties of an unsaturated compacted soil. Several temperature sensors were placed in a thermo-regulated metric scale container to monitor the imposed temperature variation in the range of the 20 to 50 °C. This imposed temperature variation reproduced the temperature variation in the thermal energy storages. An inverse analytical model based on a one-dimensional radial heat conduction equation is used to estimate the thermal diffusivity using the temperature variation between two temperature sensors. The volumetric heat capacity was measured using a calorimeter in the laboratory, enabling the estimation of the thermal conductivity of the compacted soil. Then, this estimated thermal conductivity was compared with the thermal conductivity values measured with two other methods (steady-state and transient-state method). The difference between them are discussed in terms of the sample heterogeneity, sample size, and measurement method.
Highlights
The sun is a renewable source of thermal energy
The thermal properties that affect the capacity for heat storage are the volumetric heat capacity Cv (J.m-3.K-1), the thermal conductivity λ (W.m-1.K-1) and the thermal diffusivity α (m2.s-1)
The thermal conductivity of the two samples was measured with the needle-probe device (KD2 pro)
Summary
The sun is a renewable source of thermal energy. It provides a relatively clean, abundant and safe source of energy [1]. Different types of structures are made of unsaturated compacted soil, for example, road, rail embankments and dikes. These linear structures contain several layers of unsaturated compacted soils. The proper design of an embankment to store the thermal energy requires the knowledge of the compacted soil thermal properties to optimize the efficiency of heat storage. The thermal properties that affect the capacity for heat storage are the volumetric heat capacity Cv (J.m-3.K-1), the thermal conductivity λ (W.m-1.K-1) and the thermal diffusivity α (m2.s-1). The relationship between these thermal properties is as follow: α=
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