1,721,014 research outputs found
Terrestrial heat flow, a baseline for the evaluation of geothermal potential: current knowledge in Italy and surrounding seas
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Optimising geothermal grout: Comparison of different commercial and experimental mixes and first result from numerical simulations
No full textRheology and seismotectonic regime in the northern central Mediterranean
No full textThe connection between thermal field and mechanical properties is analysed in the northern central Mediterranean region, extending from the Ligurian-Provençal basin to the Adriatic foredeep. As the thermal regime is still far from equilibrium in most of the tectonic units, transient thermal models are used. The temperature-depth distribution is estimated in four areas affected by the volcanic activity, which from the Neogene to the Present shifted from Corsica to the Apenninic arc. In the Adriatic foredeep, the thermal effects of the recent thrust-faulting phase in the buried sectors of the northern Apennines are taken into account. The general context consists of convergence involving westward subduction of the Adriatic plate. This process caused anti-clockwise rotation of Corsica and Sardinia, which led to formation of the Ligurian marginal basin, and also resulted in crustal doubling and overthrusting in the northern Apennines and rifting in the northern Tyrrhenian. Seismic activity is focused in the internal and external zones of the Apenninic arc, where low surface heat flux is observed, and in the western margin of the Ligurian-Provençal basin. This is a consequence not only of lateral variations in the thermal field but also of the different tectonic settings. Regional extensional patterns in the shallow crust, with minimum principal stress axes trending N60°E and E-W, are observed in the northern and in the southern sectors of the Apenninic arc, respectively. A compressional regime at depths greater than 30 km is observed below the northern sector of the arc, while to the south a change in the structure of the lithosphere is marked by a decrease in deeper seismic activity. Thrust faults and strike-slip faults with a thrust component support a compressional regime along the western margin of the Ligurian basin with maximum principal stress axis oriented N120°E. Two lithospheric cross-sections across the study region are constructed, based on structural, thermal, gravity, rheological and seismic data. There is clear evidence of the presence of the subducting slab of the Adriatic plate, corresponding to a thickening of the uppermost brittle layer. The crustal seismicity cut-off corresponds to temperatures of 320-390°C. A brittle layer of considerable thickness is present in the uppermost mantle beneath Variscan Corsica and the Adriatic foredeep, with estimated seismic cut-off temperature of about 550 ± 50°C
Innovative applications of geothermal energy for direct uses: a pilot study case in Marche region (Italy)
No full textRheological consequences of the lithospheric thermal structure in the Fennoscandian Shield
No full textThe surface heat-flow density of the Fennoscandian Shield, after removing the disturbances due to palaeoclimatic changes, shows a remarkable contrast from the Archaean terrains to the Late Proterozoic provinces which derive from tectonic reactivation and reheating of older materials. This involves lateral variations in the rheological behaviour of the lithosphere. On the basis of seismic structural data and assumptions about the petrological composition and flow parameters of steady-state dislocation creep, strength profiles and lateral viscosity variations have been deduced for several sites. In the northern and northeastern parts of the shield, where the Moho temperature and mantle heat-flow density are typically cratonic, the rheological thickness of the lithosphere, given by the depth at which the strength is reduced to 1 MPa, ranges from 120 to 140 km. In the southwestern shield, were enhanced Moho temperatures and mantle heat-flow density occur, the rheological thickness is reduced to 60-80 km. The depth of the brittle-ductile transition in the upper crust, above which most earthquakes occur, varies on average from 30 km in the northeast to 18 km in the southwest. The limiting temperature of the brittle uppermost layer on average is 365 ± 70°C. The essentially aseismic behaviour of the mantle agrees with the subcrustal predominating ductile deformations predicted by the models. The average lithospheric strength falls within the range 70-200 MPa, typical of the older stable areas. The viscosity of the upper mantle, at a reference depth level of 60 km, ranges from 1021 to 1024 Pa s and increases with the geological age, being maximum beneath the Archaean nucleus
Testing a Model of Flow and Heat Transfer for U-shaped Geothermal Exchangers
No full textAmong renewable resources, geothermal energy is one of the most promising for its independence on
weather conditions. However, design and installation of borehole heat exchangers on low enthalpy regions
must consider numerous influencing factors. Here, we focus on the efficiency improvement in hot water
production and heating and cooling of buildings of a pilot geothermal plant, which was implemented as part
of a hybrid system within the frame of a research project at the University of Camerino (Italy). The aims of
the geothermal plant were to study the subsoil thermal properties and monitoring the parameters of the system
during operation. As an important application for the design and sizing of low enthalpy geothermal systems,
we propose a mathematical model to study the heat transfer between the fluid circulating in the pipes and the
underground, where the mutual influence between the soil and the exchanger is considered. We present results
of these approximated solutions based on experimental measurements acquired in the actual geothermal
exchangers. Laboratory and in situ tests were also carried out to investigate the underground thermal
properties and thermal regime of the heterogeneous soil sedimentary succession
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