Comparison between Measured and Calculated Thermal Conductivities within Different Grain Size Classes and Their Related Depth Ranges

Abstract

In the field of the efficiency of very shallow geothermal energy systems, there is still a significant need for research activity. To ensure the proper exploitation of this energy resource, the decisive geophysical parameters of soil must be well-known. Within this study, thermal conductivity, as a fundamental property for evaluating the geothermal potential of very shallow geothermal systems, was analyzed and measured with a TK04 device. A dataset, consisting of various geophysical parameters (thermal conductivity, bulk density, water content, and porosity) determined for a large range of different textural soil classes, was collated. In a new approach, the geophysical properties were visualized covering the complete grain size range. The comparison between the measured and calculated thermal conductivity values enabled an investigation with respect to the validity of the different Kersten equations. In the course of this comparison, the influence of effective bulk density was taken into account. In conclusion, both Kersten formulas should be used as recommended and regular bulk density corresponded better to the reference dataset representing the outcomes of the TK04 laboratory measurement. Another objective was to visualize the relation of thermal conductivities within their corresponding textural classes and the validity of Kersten formulas for various bulk densities, depths, and soils. As a result, the accessibility to information for expedient recommendations about the feasibility of very shallow geothermal systems will be improved. Easy, accessible know-how of the fundamentals is important for a growing renewable energy sector where very shallow geothermal installations can also cover heating and cooling demands.

A Comparison of the Effects of Solar Radiation on Sandy-Loam and Clay-Loam Soils with Convective Boundary Condition

“…The model also makes a room for estimating the thermal conductivity with laboratory experiments. David et al [6] compared thermal conductivities of soils with various grain classes and sizes related to their depth using direct measurement and calculated methods. Their results showed that when the soil is saturated, the thermal conductivity increases with increase in the quantity of quartz or sand grains and bulk density.…”

A Case Study of Thermal Evolution in the Vicinity of Geothermal Probes Following a Distributed TRT Method

“…After combining the information from the ERT measurements and from the lithologic column, we then assigned standard values for the thermal properties of each sub-layer that were taken from references [2] and [46] (Table 2). 1 Represents 'moist' conditions.…”

Renewable Energy Sources in a Post-Socialist Transitional Environment: The Influence of Social Geographic Factors on Potential Utilization of Very Shallow Geothermal Energy within Heating Systems in Small Serbian Town of Ub

“…In general, every soil is suitable for very shallow geothermal applications [3]. Several parameters, such as thermal conductivity of soil, water content, pore size distribution and bulk density, have crucial influence on efficiency of very shallow geothermal applications and create different local potentials related to the prevailing soil conditions [36,37].…”

“…Available data show that in the municipality of Ub there are 2653 occupied dwellings with central heating, and 6466 occupied dwellings without district and central heating installations [65] (pp. [36][37]. Vast majority of those dwellings use coal and wood for heating.…”

“…Thermal heat conductivity is defined essentially by texture, water content and bulk density of the soil [37]. ThermoMap predefines bulk density (relation between mass and volume) for selected area at 1.3 g/m 3 .…”