Evaluation of geothermal resources in a hotspot realm: Mauritius Island (Indian Ocean)

Geochemical and geothermal investigations were performed in the Mauritius Island, located along the Seychelles-Mascarene Plateau, aimed at the preliminary assessment of possible geothermal resources. The central part of the island may be the most suitable as characterized by the most recent volcanic activity (0.03 Ma). Geochemical analyses of water samples collected from this area indicate no mature water and the chemical features are ascribable to short-term water-rock interaction in shallow hydrogeological circuits. A gradient borehole was drilled and thermal logs performed after complete thermal equilibration to evaluate the thermal gradient in central part of the island. A value of 43 \ub0C km-1 was measured and a similar result was obtained by logging a deep well no longer used for water extraction. The results point to a weak or null deep-seated thermal anomaly beneath Mauritius. This might mean that the deep thermal processes (mantle plume) invoked to occur in the hotspot area do not likely yield any particular thermal signature

Non-linear thermal simulation at system level: Compact modelling and experimental validation

In this work, a general methodology to extract compact, non-linear transient thermal models of complex thermal systems is presented and validated. The focus of the work is to show a robust method to develop compact and accurate non-linear thermal models in the general case of systems with multiple heat sources. A real example of such a system is manufactured and its thermal behaviour is analyzed by means of Infra-Red thermography measurements. A transient, non-linear Finite-Element-Method based model is therefore built and tuned on the measured thermal responses. From this model, the transient thermal responses of the system are calculated in the locations of interest. From these transient responses, non-linear compact transient thermal models are derived. These models are based on Foster network topology and they can capture the effect of thermal non-linearities present in any real thermal system, accounting for mutual interaction between different power sources. The followed methodology is described, verification of the model against measurements is performed and limitations of the approach are therefore discussed. The developed methodology shows that it is possible to capture strongly non-linear effects in multiple-heat source systems with very good accuracy, enabling fast and accurate thermal simulations in electrical solvers

A simple 1-D finite elements approach to model the effect of PCB in electronic assemblies

In this paper, a simple method to describe the effect of Printed Circuit Board (PCB) and environment on the thermal behavior of packaged devices is addressed. This approach aims at exploiting the benefit of compact thermal models, which are necessarily one-dimensional, together with the advantage of Finite Element (FE) modeling, which retains all the three-dimensional geometrical details, only in the regions of the model that must be accurately described. The main focus is on correct modeling of long power pulses for subsequent electro-thermal and thermo-mechanical analysis at chip level

Conductive heat flow pattern of the central-northern Apennines, Italy

We analyzed thermal data from deep oil exploration and geothermal boreholes in the 1000-7000 m depth range to unravel thermal regime beneath the central-northern Apennines chain and the surrounding sedimentary basins. We particularly selected deepest bottom hole temperatures, all recorded within the permeable carbonate Paleogene-Mesozoic formations, which represent the most widespread tectono-stratigraphic unit of the study area. The available temperatures were corrected for the drilling disturbance and the thermal conductivity was estimated from detailed litho-stratigraphic information and by taking into account the pressure and temperature effect. The thermal resistance approach, including also the radiogenic heat production, was used to infer the terrestrial heat flow and to highlight possible advective perturbation due to groundwater circulation. Only two boreholes close to recharge areas argue for deep groundwater flow in the permeable carbonate unit, whereas most of the obtained heat-flow data may reflect the deep, undisturbed, conductive thermal regime

Geothermal flow and water-load seafloor depth of the Eastern Mediterranean Sea

We used bathymetry, sediment thickness and terrestrial heat-flow data to investigate the nature of the Eastern Mediterranean Sea lithosphere. We processed bathymetric data by removing the subsidence caused by sediment deposition to obtain the water-loaded seafloor depth. Terrestrial heat flow measurements were corrected for sedimentation and climatic changes to infer the purely conductive steady-state geothermal flow. Water-load seafloor depths and thermal data were then compared to reference models of continental lithosphere stretching and ocean plate cooling. The results argue that the Levantine Basin is floored by a continental stretched crust that thinned by a factor of 1.6-2.7, whereas the Herodotus Basin crust is of oceanic type. The water-loaded seafloor depths in all the Eastern Mediterranean are consistent with geological ages of > 250 Ma. The mantle heat flow in the Herodotus Basin (33 mW m-2) is consistent with that of the oceanic Ionian lithosphere, whereas in the Levantine Basin (26 mW m-2) is comparable to that of the Sinai continental microplate

Thermophysical parameters from laboratory measurements and tests in borehole heat exchangers

Besides the type of thermal regime, the performance of borehole heat exchangers relies on the overall thermal resistance of the borehole. This parameter strongly depends on the underground thermal conductivity, which accounts for most of the heat that can be extracted. The geometric configuration and the increase of thermal conductivity of the grout filling back the bore can yield a non-negligible enhancement in thermal performances. In this paper, we present a study on a pilot geothermal plant consisting of two borehole heat exchangers, 95 m deep and 9 m apart. Laboratory and in situ tests were carried out with the aim of investigating underground thermal properties, mechanisms of heat transfer and thermal characteristics of the filling grouts. Samples of grouting materials were analysed in the lab for assessing the thermal conductivity. An attempt to improve the thermal conductivity was made by doping grouts with alumina. Results showed that alumina large concentrations can increase the thermal conductivity by 25-30%