1,721,045 research outputs found
Low Enthalpy Geothermal Open Loop Heat Pumps: a suitable tool for thermal energy supply in urban areas
No full textGeothermal heat pumps represent an interesting technology that is expected to contribute significantly to the reduction of primary energy use for heating and cooling and meet the targets set by the European Union. Additional benefits of this technology are related to the integration with discontinuous energy resources, in particular wind, combining heat and power. The replacement of conventional heating systems such as boilers, with heat pump systems allows the de-localization of emissions of micropollutants from urban centers to the sites in which thermal power stations are operating. This also enhances emissions monitoring and control. Furthermore, the use of distributed production systems based on the use of renewable sources reduces also CO2 emissions. (Lo Russo et al., 2011) In this general context, the increasing implementation in several areas of the world of the open-loop groundwater heat pumps technology which discharge into the aquifer for cooling and heating buildings could potentially cause, even in the short term, a significant environmental impact associated with thermal interference with groundwater, particularly in the shallow aquifers. The discharge of water at different temperatures compared to baseline (warmer in summer and colder in winter) poses a number of problems in relation to the potential functionality of many existing situations of use of the groundwater (drinking water wells, agricultural, industrial, etc.). In addition, there may be cases of interference between systems, especially in the more densely urbanized. This means that the alteration of the temperature of the groundwater determined by a plant may affect the installations located downstream, with significant alterations of the performances of the systems themselves. These issues highlight how it is crucial for the compatible development of the technology of groundwater heat pumps discharging into aquifers that it shall be a fair assessment and technically effective both for cooling and heating plants and pumping and injection systems in ground. The current legislation related to withdrawals and discharges into aquifers design a framework suitable for the protection of groundwater and permit to decide the 3 best configuration of the plant with a case by case approach. Appropriate specialized hydrogeological investigations should be performed for the characterization of the main hydrogeological parameters of the subsoil at the considered site. In this thesis some important aspects related to the development of open-loop heat pumps have been explored in a typical urban contest (Torino city, NW Italy). The results of the work have allowed to define several fundamental aspects in order to optimize the design choices of GroundWater Heat Pump (GWHP) systems. After a general description of the low enthalpy geothermal heat pumps technologies (Chapter 1), the analysis and comparison of the current hydrogeology problems in urban area are described, considering the impact of groundwater heat pump system in a urban contest (Chapter 2). Urban and industrial development can impose major stresses on groundwater resources. The conceptual model for the groundwater flow system, the schematization of the aquifer boundaries and the estimation of basic hydrogeological parameters are among the main issues which should be investigated in the development of open-loop heat pumps plants. In particular, some characteristics of urban elements require particular attention if compared to less anthropized areas. In Chapter 3 the geological and hydro-stratigraphical characteristics of the Torino test site have been described. This chapter includes a complete description of the GWHP system plant and monitoring system that has been installed in the Politecnico di Torino and the illustration of the fundamentals of the numerical modelling we performed using a specific comme
Evidences of advective heat transport related to an open-loop groundwater heat pump plant (Turin, NW Italy)
No full textAdvective Heat Transport in an Unconfined Aquifer Induced by the FieldInjection of an Open-Loop Groundwater Heat Pump
No full textProblem statement: The increasing diffusion of low-enthalpy geothermal open-loop Groundwater Heat Pumps (GWHP) providing buildings air conditioning requires a careful assessment of the overall effects on groundwater system, especially in the urban areas. The impact on the groundwater temperature in the surrounding area of the re-injection well is directly linked to the aquifer properties. Physical processes affecting heat transport within an aquifer include advection (or convection) and hydrodynamic thermodispersion (diffusion and mechanical dispersion). If the
groundwater flows, the advective components tend to dominate the heat transfer process within the aquifer and the diffusion can be considered negligible. This study illustrates the experimental results derived from the groundwater monitoring in the surrounding area of an injection well connected to an open-loop GWHP plant which has been installed in the “Politecnico di Torino” (NW Italy) for cooling some of the university buildings. Groundwater pumping and injection interfere only with the upper unconfined aquifer. Approach: After the description of the hydrogeological setting the authors examined the data deriving from multiparameter probes installed inside the pumping well (P2), the injection well (P4) and a downgradient piezometer (S2). Data refers to the summer 2009. To control the aquifer thermal stratification some multi-temporal temperature logs have been performed in the S2. Results: After the injection of warm water in P4 the plume arrived after 30 days in the S2. That delay is compatible with the calculated plume migration velocity (1.27 m d-1) and their respective distance
(35 m). The natural temperature in the aquifer due to the switching-off of the GWHP plant has been reached after two month. The Electrical Conductivity (EC) values tend to vary out of phase with the temperature. The temperature logs in the S2 highlighted a thermal stratification in the aquifer due to a low vertical dispersion of the injected warm water. Conclusion: Experimental evidences seem to confirm the prevalence of heat advective transport component respect the dispersive phenomena. This
hypothesis appears validated by the following evidences: (i) the calculated advective migration velocities are compatible with the calculated retardation factor and the temperature revealed in the S2, (ii) both the groundwater and the heat tend to flow horizontally due to the different values of horizontal and vertical hydraulic conductivity in the Unit 1 (thermal stratification) and (iii) the flowing water highlighted different geochemical characteristics during the time
Groundwater in the Urban Environment: Management Needs and Planning Strategies
No full textProblem statement: Over the past thirty years urban transformations, such as urbanization, suburbanization, dis-urbanization and re-urbanization processes, have modified the subsurface conditions of Torino (NW Italy). In order to contribute to the solution of the problems concerning groundwater the conceptual model for the groundwater flow system, the schematization of the aquifers boundaries and the estimation of basic hydrogeological parameters are among the main issues which should be investigated. This study was mainly aimed at illustrating (i) a new interpretation for the Torino urban area hydrogeological setting (ii) highlighting the current groundwater criticisms and (iii) emphasizing the priority actions to implement a good urban groundwater management system. Approach: Starting from the analysis of the existing subsurface data, a comprehensive description of the general geological setting had been performed, three main (hydro) stratigraphical Units had been described and their reciprocal relationships had been detected. On the basis of the available data, the unconfined groundwater natural seepage had been reconstructed, a hydrogeological map and a cross section illustrating the units characteristics had been produced. Results: The analysis highlighted three main groundwater criticisms: A natural unconfined groundwater level uplifting in the quaternary unit 1, a widespread inorganic pollution under abandoned industrial areas and many interference problems with the groundwater in unit 1 caused by the new transport infrastructures. Another important problem was the scarce geographical density of the existing groundwater monitoring network operating in the urban area. Conclusion: Solutions to specific, local problems can give the opportunity to transform some of the above mentioned problems into useful resources for the territorial development. The expansion of the groundwater observation network clearly appeared to be the main action to be implemented by the public authorities. Other successive actions could be the construction of a multipurpose interactive real-time mathematical model of groundwater movement in the urban area and the development of improved methods for predicting changes of hydrogeological condition
An open-loop ground-water heat pump system: transient numericalmodeling and site experimental results
No full textDistribution of quarries in the piedmont region: the regional plan of mining activities (PRAE) as a tool for mining activities regulation and characterisation
Full text linkThe Regional Plan of Mining Activities (PRAE), adopted in December 2022, represents the strategic regulation instrument pursuing the balance between environmental sustainability and economic development produced by mining activity at a regional scale. The paper proposes an overview of the main regional in-force instrument for surface and ground-water planning and management (PAI and PTA) and how these intersect with the introduced PRAE. Besides, the interaction between mining activities and the geomorphological and hydrogeological contexts in which they are located is described, defining the resulting constraints regarding their interaction with extraction areas. A significant portion of the quarries are located in the floodplain, falling both in river bands of medium-high probability of flooding and in areas involving aquifers bodies, hence these extractive sites are heavily restricted both in terms of excavation depths, never exceeding the base of the surface aquifer. The depth of the water table and the base of the aquifer represent the two fundamental parameters on which new restrictions have been defined in the PRAE in terms of the possibility of developing new quarry areas
Water services risk related to flooding and landslides phenomena: the Vernazza case study (Cinque Terre National Park, Italy)
No full textL'individuazione di una metodologia di valutazione del rischio per le infrastrutture idriche rappresenta un fondamentale tassello nelle complesse operazioni di pianificazione territoriale per la gestione delle emergenze soprattutto nelle fasi immediatamente successive all'evento calamitoso. Lo scopo del lavoro presentato consiste nell'individuazione dei principali parametri di quantificazione del rischio idrogeologico connesso a dissesti gravitativi e fenomeni di inondazione cui sono potenzialmente soggetti i punti di approvvigionamento e le reti idriche, la rete fognaria e gli impianti di depurazione. Nello sviluppo del lavoro si è preso in considerazione il sito pilota di Vernazza nel Parco Nazionale delle Cinque Terre in Liguria, colpito gravemente dall'alluvione del 25 ottobre 201
Development of the thermally affected zone (TAZ) around a groundwater heatpump (GWHP) system: A sensitivity analysis
No full textOpen-loop groundwater heat pumps (GWHPs) are considered one of the most energy efficient and environmentally friendly air-conditioning systems for temperate zones. A fundamental aspect in GWHP plant design is early evaluation of the thermally affected zone (TAZ) that develops around the injection well. This is particularly important to avoid interference with previously existing groundwater uses (wells) and subsurface underground structures. Numerical modelling is useful for delineating temperature anomalies. We carry out numerical simulations and a sensitivity analysis for the subsurface parameters affecting the TAZ. Using the simulation resultsweobtain a relative hierarchy of significance for the parameters with respect to the final result and then apply this analysis to an actual site. The results of the analysis indicate that the hydrodynamic parameters correlated with groundwater flow such as the hydraulic conductivity and the gradient are highly important, particularly those relating to the advective heat flow componen
The unconfined aquifers potential for the diffusion of the Open-Loop Groundwater heat pumps (GWHP) in the Piemonte Region (NW Italy)
No full textThe successful implementation of very low-enthalpy geothermal (T<50°C) open-loop groundwater heat pumps (GWHP) for heating and cooling buildings in several European countries has stimulated the investigation of the thermal and productive characteristics of the plain aquifers in the overall Piemonte region (NW Italy). These widespread systems can be frequently located near potential users (below and near buildings) and therefore no regional thermal energy transport infrastructure is required.
GWHP typically withdraws groundwater to provide heat. In the winter, the GWHP extracts heat from the water to provide space heating. With reversible heat pumps, the heat-transfer process can be reversed in the summer and the groundwater absorbs heat from the living or working space and cools the air. Actually, the GWHP’s are suited to regions with extended shallow aquifers, from which it is relatively easy and not very expensive to extract groundwater. Generally, a highly productive, shallow aquifer would favour successful and efficient functioning of the GWHP. The most important
consideration in GWHP design is to obtain a plentiful amount of groundwater with a very stable temperature. In Piemonte region there are extensive alluvial plain shallow aquifers which are suitable to be used for this aims. The vertical separation between the unconfined and deeper confined aquifers varies from a few meters to several tens of meters depending on local hydrogeological conditions. Deep, high-quality groundwater bodies are legally preserved for human consumption. To avoid potential alteration of the deeper aquifer, they should not be intersected by the wells to be used to
operate the GWHP plant. Moreover, GWHP could be used only with shallow groundwater. Fortunately, the shallow groundwater temperatures are rather constant for the summer or winter seasons and also considering annual periods. Air-temperature influence (seasonal variability) seemed strictly connected to the depth to groundwater and it was negligible when the value was over 9.5 m. This element confirms that a strong implementation of GWHP could be considered suitable in the overall plain.
At the end of 2012 more than 55 GWHP plants were requested to be authorized or are under construction in the whole Piemonte region plain
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