Search results for "Geothermal gradient"
showing 10 items of 52 documents
The importance of iron speciation (Fe+2 /Fe+3 ) in determining mineral assemblages: an example from the high-grade aluminous metapelites of southeast…
2012
Metapelitic granulites from the Anosyen domain of southeastern Madagascar are exposed in three intercalated formations: the Amparihy, Bakika and Ihosy formations. Although mineralogically distinct from each other, the rocks from these formations show very similar bulk-rock compositions when measured on a FeT basis. The preserved mineral assemblages thus do not reflect differences in the ratios of the main rock-forming oxides (i.e. Al2O3:FeT:MgO), but instead reflect variations in the pre-metamorphic oxidation state of the protolith rocks. These differences in oxidation state are manifested via differences in iron speciation – either Fe+2 or Fe+3. The relatively reduced rocks of the Amparihy…
Methodological approach for evaluating the geo-exchange potential: VIGOR Project
2012
In the framework of VIGOR Project, a national project coordinated by the Institute of Geosciences and Earth Resources (CNR-IGG) and sponsored by the Ministry of Economic Development (MiSE), dedicated to the evaluation of geothermal potential in the regions of the Convergence Objective in Italy (Puglia, Calabria, Campania and Sicily), is expected to evaluate the ability of the territory to heat exchange with the ground for air conditioning of buildings. To identify the conditions for the development of low enthalpy geothermal systems collected and organized on a regional scale geological and stratigraphic data useful for the preparation of a specific thematic mapping, able to represent in a …
LABORATORY INSTRUMENTATION TO STUDY CHANGES OF ELECTRICAL CONDUCTIVITY OF ROCKS WITH CHANGES OF FREQUENCY, TEMPERATURE AND PRESSURE*
1983
A laboratory instrument was developed to investigate the electrical properties of rock samples with respect to changes of frequency, temperature and pressure. The instrument can be used to obtain general trends and typical values for geological media. It should be of particular interest in geothermal studies and research in the geophysical properties of rocks. The design intervals for quantities under investigation were 20–300°C, 10 5 -4 × 10 7 Pa and 5 × 10 −4 -10 3 Hz. Certain limitations exist on the simultaneous use of the highest values of temperature and pressure. The main features of the instrument are: analog electrical outputs recorded by an x-y recorder or observed on a scope with…
Chronological records of metal deposition in sediments from the Strait of Sicily, central Mediterranean: assessing natural fluxes and anthropogenic a…
2010
Abstract Sediment box-cores were recovered from the Strait of Sicily along two onshore–offshore transects in water depths of 29–500 m. Samples were dated by 210 Pb and analysed for major and trace elements. Inspections of chronological profiles integrated with application of statistical algorithms to the geochemical dataset and supported by in situ hydrological observations were used to assess factors driving element distributions. Mineralogical and chemical variability of sediments offshore of the southwestern Sicily coast reflect the irregular sea floor morphology of the Adventure Bank. Anthropogenic inputs explain enrichments with respect to background values for Sb, As, Pb, and Hg, that…
Comparison between the energy performance of a ground coupled water to water heat pump system and an air to water heat pump system for heating and co…
2008
Abstract The investigation presented in this article was aimed at demonstrating the technical and economical feasibility of using ground source heat pump systems in mixed climate applications, where cooling requirements are dominant. We show an experimental comparison between a ground coupled heat pump system and a conventional air to water heat pump system, focussing at the heating and cooling energy performance. A direct comparison could be made as both systems are linked, in parallel, to the same building with exactly the same loads and climatic conditions. For a whole climatic season the results obtained show that the geothermal system saves, in terms of primary energy consumption, a 43…
Exergetic and exergoeconomic analysis of a novel hybrid solar-geothermal polygeneration system producing energy and water
2016
Abstract A dynamic simulation model of a novel solar–geothermal polygeneration system and the related exergetic and exergoeconomic analyses are presented in this paper. The plant is designed in order to supply electrical, thermal and cooling energy and fresh water for a small community, connected to a district heating and cooling network. The hybrid system is equipped with an Organic Rankine Cycle fueled by medium-enthalpy geothermal energy and by a Parabolic Trough Collector solar field. Geothermal brine is also used for space heating and cooling purposes. Finally, geothermal fluid supplies heat to a Multi-Effect Distillation unit, producing also desalinized water from seawater. Dynamic si…
Wireless Sensor Network for Monitoring Thermal Evolution of the Fluid Traveling inside Ground Heat Exchangers
2011
Ground-Coupled Heat Pump (GCHP) systems are an attractive choice of system for heating and cooling buildings (Genchi, 2002; Sanner, 2003; Omer, 2008; Urchueguia, 2008). By comparison with standard technologies, these heat pumps offer competitive levels of comfort, reduced noise levels, lower greenhouse gas emissions, and reasonable environmental safety. Furthermore, their electrical consumption and maintenance requirements are lower than those required by conventional systems and, consequently, they have a lower annual operating cost (Lund, 2000). Ground source systems are recognized by the U.S. Environmental Protection Agency as being among the most efficient and comfortable heating and co…
Mercury levels in sediments of central Mediterranean Sea: a 150+ year record from box-cores recovered in the Strait of Sicily.
2006
To evaluate the degree of anthropogenic mercury pollution, Hg contents have been measured for box-core sediments sampled along three nearshore-offshore transects in the Strait of Sicily and well constrained for their mineralogy, bulk geochemistry and TOC%. Hg values are generally low (from 15 to 70 microg kg(-1)); however, depth profiles clearly display upcore rising concentrations (up to 202 microg kg(-1) near the SE Sicily coast) that are attributed to anthropogenic load. Based on (210)Pb chronology, these trends are more dramatic across the last 20-30 years. Geogenic influence is thought to explain some anomalies related to volcanic emission and geothermal activity. Combined effects due …
Geochemical characterization of surface waters and groundwater resources in the Managua area (Nicaragua, Central America)
2008
This paper reports new geochemical data on dissolved major and minor constituents in surface waters and ground waters collected in the Managua region (Nicaragua), and provides a preliminary characterization of the hydrogeochemical processes governing the natural water evolution in this area. The peculiar geological features of the study site, an active tectonic region (Nicaragua Depression) characterized by active volcanism and thermalism, combined with significant anthropogenic pressure, contribute to a complex evolution of water chemistry, which results from the simultaneous action of several geochemical processes such as evaporation, rock leaching, mixing with saline brines of natural or…
Diffuse and focused carbon dioxide and methane emissions from the Sousaki geothermal system, Greece
2006
[1] We report first data on chemical composition of the gas emitted by the geothermal system of Sousaki, Greece. Gas manifestations display typical geothermal gas composition with CO2 as the main component and CH4 and H2S as minor species. Soil gas composition derives from the mixing of two end-members (atmospheric air and geothermal gas). Soil CO2 fluxes range from<2 to 33,400 g m−2 d−1. The estimated diffuse output of hydrothermal CO2, estimated for an area of 0.015 km2, is about 630 g s−1, while a tentative estimation of CH4 diffuse output gave a value of about 1.15 g s−1. Point sources accounted for lower flux values of ∼26 g s−1 of CO2, ∼0.1 g s−1 of CH4 and ∼0.02 g s−1 of H2S.