Abstract
Mechanical (flexural and uniaxial compressive strengths) and physical (thermal conductivity) properties of two new bentonitic grouts doped with 5 and 10% of graphite powder are discussed in this work and evaluated for their potential use in low-enthalpy geothermal applications. The same tests have been also conducted on a pure starting material (bentonitic grout) already present on the market and used to seal geothermal probes into boreholes. Experimental data show that the addition of 5 and 10% of graphite powder positively alters the mechanical properties of the doped bentonitic grouts, i.e., both flexural and uniaxial compressive strengths increased with respect to those of the pure material. Thermal conductivity also improved up to 60% in the doped bentonitic grouts. A simple analysis of the cost/benefit ratio suggests, however, that the bentonitic grouts doped with 5% of graphite powder is more suitable and competitive for a launch on the market and utilization as a sealing material in boreholes aimed at low-enthalpy geothermal installations. Implementation of thermal properties of the grout material implicates a reduction of the total borehole length of 15–20%.
Highlights
Energy is a fundamental condition for the social growth of the community, being an essential ingredient for almost all human activities and services
Experimental data show that the addition of 5 and 10% of graphite powder positively alters the mechanical properties of the doped bentonitic grouts, i.e., both flexural and uniaxial compressive strengths increased with respect to those of the pure material
A simple analysis of the cost/benefit ratio suggests, that the bentonitic grouts doped with 5% of graphite powder is more suitable and competitive for a launch on the market and utilization as a sealing material in boreholes aimed at low-enthalpy geothermal installations
Summary
Energy is a fundamental condition for the social growth of the community, being an essential ingredient for almost all human activities and services. Anomalous geothermal fluxes useful for exploitation are present in specific geological settings, there is a worldwide incredible potential related to low-enthalpy geothermal energy that is, at present, scarcely considered in many countries (Banks 2012 and references therein). In this regard, primary reasons are the lack of scientific-technical background in the field of low-enthalpy geothermal resources, coupled with the absence of adequate basic information of Viccaro Geotherm Energy (2018) 6:4 small-to-medium scale subsoil characteristics that are essential to appropriately manage feasibility studies. Heating and cooling systems from low-enthalpy geothermal energy seem to be the most acceptable solution in circumstances where solar thermal or photovoltaic are prevented (e.g., scarce exposure to solar radiation, intense urbanization, protected natural/archeological sites, historical city centers, etc.)
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