Indagine geoelettrica per la valutazione dell'intrusione salina negli acquiferi costieri del comprensorio meridionale veneziano

Riassunto Attraverso l’indagine geoelettrica è stata eseguita una prima valutazione dell’estensione dell’intrusione salina marina e lagunare nel settore meridionale del comprensorio veneziano. Nel settore costiero, caratterizzato da dune e cordoni litoranei, è presente una falda freatica con acqua “dolce” fino ad una profondità di anche una decina di metri e l’intrusione salina coinvolge i terreni sottostanti fino ad oltre 70 metri. Nell’entroterra, la soggiacenza del territorio rispetto al livello marino, i pompaggi con idrovore e la rete idrografica pensile in comunicazione col mare sono fattori che riducono a pochi metri, ed in alcune zone annullano, lo spessore della falda dolce superficiale e consentono al cuneo salino di raggiungere la base dei terreni coltivati. Abstract A preliminary evaluation of the salt water intrusion in coastal aquifers of the southern Venetian region, is here made using geoelectical investigation. The results of the analyses show that the two dimensional extent of the saline contamination is mainly related to the geomorphology of this area. In the littoral sector, characterized by a mean ground elevation of two meters above mean sea level (sand dunes and paleolittoral strips), a phreatic fresh water body is present and salt water contamination involves aquifers and aquitards from 10 to 70 m deep. In the inland, the ground level is about 2-3 m below mean sea level; the water pumping in the reclaimed lands and the marine water seepage in the rivers during high tides are among the factors that seriously reduce the fresh water body and that allow salt water to contaminate the agricultural soils

Techno-economic mapping for the improvement of shallow geothermal management in southern Switzerland

Cantone Ticino, a mountainous region located in the southern part of Switzerland, is greatly affected by the continuous growth of subsurface exploitation through the use of both closed-loop and open-loop geothermal systems. In this study, techno-economic maps for shallow geothermal potential of Cantone Ticino are produced, considering closed-loop systems. The work starts with the identification of the main parameters affecting the techno-economic potential such as GST and thermal conductivity. Maps for different indicators of techno-economic feasibility are created and compared against real data/measurements. An empirical method is tailored to derive a map of the techno-economic geothermal potential, expressed as meters required to provide 1 kW of installed power. The produced map shows an overall discrepancy from real installed length data of approximately ±23%. Moreover, compared with current regulation, the produced maps show an unoptimized management of the shallow geothermal resource, since high potential zones are commonly located where the installation of BHE is not permitted and often closed-loop systems are installed where the estimated potential is lower, mainly in alluvial fans. In light of these considerations, the authorization process in Cantone Ticino for BHE should be revised taking into account the real techno-economic potential

Laboratory thermal conductivity measurements on gravel sample

Modern Ground Source Heat Pumps (GSHPs) systems must be designed by taking into account the ground thermal properties, in order to properly plan the capability of the heat pumps to transfer calories through the Ground Source Heat Exchangers (GSHE) to the subsoil (and vice versa). [...

Solar assisted ground source heat pump in cold climates

The geothermal heat pump(or ground source heat pump) uses the ground as heat source or sink for heating and cooling respectively. The design of the borehole field is the key element of these systems since the wrong evaluation of the boreholes’ length affects the initial costs and/or the energy performance of the heat pump. The geothermal heat pumps are considered as renewable energy technologies, consequently can help the community to reduce the primary energy uses and also the CO2 emissions. However the sustainability and efficiency are ensured in the long period only when the heat balance through the ground is guaranteed. This work evaluates the thermal behavior of ground source heat pumps in cold climates, where the thermal load profile of buildings is not balanced between heating and cooling, especially in residential sector characterized by low internal loads. In these contexts, the heat pump mainly works in heating mode, extracting continuously heat from the ground. As a result, the ground temperature decreases gradually during the years affecting the energy performance of the heat pump. A possible solution to this problem is to use solar thermal collectors to stabilize or gradually increase the mean ground temperature(these systems are called Solar Assisted Ground Source Heat Pump – SAGSHP). In this work a multi floors residential building with 12 flats (88 m2 each)is analyzed in three climate zones, making use of the simulation tool TRNSYS. Different configurations of the plant system have been investigated and the case without the solar thermal collectors has been considered as reference

Solar Assisted Ground Source Heat Pump in Cold Climates

Abstract The geothermal heat pump (or ground source heat pump) uses the ground as heat source or sink for heating and cooling respectively. The design of the borehole field is the key element of these systems since the wrong evaluation of the boreholes' length affects the initial costs and/or the energy performance of the heat pump. The geothermal heat pumps are considered as renewable energy technologies, consequently can help the community to reduce the primary energy uses and also the CO 2 emissions. However the sustainability and efficiency are ensured in the long period only when the heat balance through the ground is guaranteed. This work evaluates the thermal behavior of ground source heat pumps in cold climates, where the thermal load profile of buildings is not balanced between heating and cooling, especially in residential sector characterized by low internal loads. In these contexts, the heat pump mainly works in heating mode, extracting continuously heat from the ground. As a result, the ground temperature decreases gradually during the years affecting the energy performance of the heat pump. A possible solution to this problem is to use solar thermal collectors to stabilize or gradually increase the mean ground temperature (these systems are called Solar Assisted Ground Source Heat Pump – SAGSHP). In this work a multi floors residential building with 12 flats (88 m 2 each) is analyzed in three climate zones, making use of the simulation tool TRNSYS. Different configurations of the plant system have been investigated and the case without the solar thermal collectors has been considered as reference

Laboratory Measurements of Gravel Thermal Conductivity: An Update Methodological Approach

Abstract Direct measurements of gravel thermal properties are usually quite challenging to be performed in laboratory, due to the very coarse sediments size. As a consequence, the reference thermal values provided by literature for gravels are quite limited and dispersed. A guarded hot plate Taurus Instruments TLP 800, usually used for measuring the thermal conductivity of buildings materials, was slightly modified in order to measure the thermal conductivity of some gravel samples. The tests were performed both in dry and wet conditions. The paper presents the first obtained results

Rock Thermal Conductivity as Key Parameter for Geothermal Numerical Models

Abstract The geothermal energy applications are undergoing a rapid development. However, there are still several challenges in the successful exploitation of geothermal energy resources. A special effort is required to characterize the thermal properties of the ground and to implement the thermal energy transfer technologies. Aim of this study is to provide original heat conductivity values for rocks and sediments in regions included in the VIGOR Project (southern Italy), to overcome the existing lack of data. Thermal properties tests were performed on several samples, both in dry and wet conditions, using thermal analyzer operating following the Modified Transient Plane Source method

ground source heat pump systems in historical buildings two italian case studies

Abstract Reducing the energy demand of buildings has become one of the key points of the European Union. The issue related to the air conditioning of old and historical buildings is nowadays one of the most important field of operation for the primary energy saving and, at the same time, for the reduction of the CO 2 emission. The recent development of heat pump able to rise the supply of high temperature at the condenser side makes this technology suitable for the application also in historical buildings that are characterized by low thermal insulation and high thermal capacitance. In this context, the ground source heat pump systems can be used for both heating and cooling. The aim of this work is to analyze the thermal behavior of two historical buildings located in Italy, in Venice and Florence respectively. Detailed computer simulations of the buildings have been carried out by means of a transient calculation tool TRNSYS. Energy simulations of GSHP systems have been performed and a comparison with a common plant system using a gas boiler for heating and air-to-water chiller for cooling has been carried out

Soil thermal conductivity from early TRT logs using an active hybrid optic fibre system

At the Molinella test site in Italy, a monitoring well has been equipped with a hybrid active optical fibre cable down to the depth of 100 m sealed with geothermal grouting. The cored borehole provided a full stratigraphic sequence of unconsolidated alluvial deposits. The cored material has been classified from a geotechnical point of view, and the thermal parameters of the most relevant lithologies have been directly measured. Active heating of the optical fibre cable has been provided by a constant heating power injected through copper wires contained within the cable structure. This way, not only the equivalent thermal conductivity of the entire stratigraphy but also the thermal conductivity at a spatial resolution of 1 m have been obtained. For each investigated layer, the thermal conductivity obtained from the distributed temperature measurements and the ones acquired using direct measurements are interpreted and compared