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Geological and geophysical exploration campaigns have ascertained the coexistence of low to medium-temperature geothermal energy resources in the deepest regions of Italian sedimentary basins. As such, energy production based on the exploitation of available geothermal resources associated with disused deep oil and gas wells in Italian oilfields could represent a considerable source of renewable energy. This study used information available on Italian hydrocarbon wells and on-field temperatures to apply a simplified closed-loop coaxial Wellbore Heat Exchanger (WBHE) model to three different hydrocarbon wells located in different Italian oilfields (Villafortuna-Trecate, Val d’Agri field, Gela fields). From this study, the authors have highlighted the differences in the quantity of potentially extracted thermal energy from different analysed wells. Considering the maximum extracted working fluid temperature of 100 °C and imagining a cascading exploitation mode of the heat accumulated, for Villafortuna 1 WBHE was it possible to hypothesise a multi-variant and comprehensive use of the resource. This could be done using existing infrastructure, available technologies, and current knowledge.

Abstract In this paper, an Artificial Neural Network is used for the prediction of pole slips of a synchronous generator, which is in the process of resynchronisaton after a fault. The measurements considered are the rotor speed and angle, at the moment the circuit breaker recloses. Given these in-puts, the Artificial Neural Network suggested is capable of predictfng whether the generator will resynchronise or it will skip a pole. This prediction is very fast, so that it could be used in real-time control.The method proposed has been tested with a simulation program based on a synchronous generator model with seven state variables, including also the saturation in the d-axis.

Abstract In this study, the influence of compressor speed, ejector motive nozzle needle position and evaporator inlet metering valve opening on the oil circulation rates (OCRs) of an R744 transcritical standard ejector cycle was experimentally investigated. Significantly higher OCR (∼10%) was observed at the evaporator inlet of the ejector cycle than that at the high pressure side (∼1%) measured in the same cycle under the same conditions. It has been observed that evaporator OCR was increased with increasing compressor speed. When the motive nozzle needle moved towards the nozzle throat, both compressor discharge flow rate and evaporator OCR were observed to be significantly lowered. As the evaporator inlet metering valve opening was adjusted, the compressor mass flow rate did not vary significantly while the evaporator mass flow rate decreased with decreasing metering valve opening. The evaporator OCR decreased from 6.5% to 2.2% as the metering valve opening varied from 86% to 27%. High evaporator OCR results in large evaporator pressure drop and low heat transfer coefficient. In addition to the standard ejector cycle, several alternative ejector cycles were theoretically analyzed to see if there is similar problem of high OCR in the evaporator. In ejector liquid recirculation cycle and multi-stage multi-ejector supermarket refrigeration cycle, similar high OCR problem in the evaporator may exist, while in two evaporator ejector cycle, evaporator OCR is equal to compressor OCR at steady state.

Artículos en revistas Islands are facing considerable challenges in meeting their energy needs in a sustainable, affordable and reliable way. The present paper develops an integrated approach to economically assess initiatives that can transform island power systems into smart ones. Single and multi-action initiatives fostering the deployment of renewable energy sources (RES), energy storage systems (ESS), demand-side management (DSM), and electric vehicle (EV) are considered. An hourly unit commitment on a weekly basis is proposed to assess the impact of the initiatives on the system operation costs of five prototype island power systems, which have been identified by applying clustering techniques to a set of sixty islands power systems. The different investment costs of the initiatives are accounted for determining their corresponding internal rate of return (IRR) through their lifetime. The economic assessment of single and multi-action initiatives for five prototype islands representing sixty island power systems quantifies which initiatives are most suitable for which type of island power system. The assessment shows that islands of different sizes and features require different initiatives. Larger islands tend to DSM initiatives, whereas smaller islands tend to RES initiatives. Multi-action initiatives achieve highest system operation cost reduction, whereas single action initiatives yield to highest IRR. info:eu-repo/semantics/publishedVersion

GDI injection systems have become dominant in passenger cars due to their flexibility in managing and advantages in the fuel economy. With the increasingly stringent emissions regulations and concurrent requirements for enhanced engine thermal efficiency, a comprehensive characterization of the fuel spray behavior has become essential. Different engine loads produce in a variety of fuel supplying conditions that affect the air/fuel mixture preparation and influence the efficiency and pollutant production. The flash boiling is a particular state that occurs for peculiar thermodynamic conditions of the engine. It could strongly influence the mixture in subatmospheric environments with detrimental effects on emissions. In order to obtain an in-depth understanding of the flash boiling phenomena, it is necessary to study the parameters influencing the mixture formation and their appearance in diverse engine conditions. The objective of this study is to investigate the effect of the ambient pressure and temperature on the morphology of a multi-jet spray operating in flash boiling status using a Gasoline Direct Injection setup. An eight-hole, GDI injector from the Engine Combustion Network (ECN), was investigated under flashing and non-flashing conditions. The experiments were performed in an opticallyaccessible, constant-volume vessel at engine-like conditions. A hybrid optical setup, Z-type schlieren and Mie scattering, using a high-speed C-Mos camera allowed the quasi-simultaneous acquisition of both the vapor and the liquid phases. A customized image-processing procedure, developed in Matlab environment, was used to outline the contours of both the fuel phases. Different morphologies of the fuel spray were studied as function of the injection pressure, the fuel temperature, and the backpressure in the vessel, through the measurement of the axial penetration and cone angle

Solving very-large-scale optimization problems frequently require to decompose them in smaller subproblems, which are iteratively solved to produce useful information. One such approach is the Lagrangian relaxation (LR), a general technique that leads to many different decomposition schemes. The LR produces a lower bound of the objective function and useful information for heuristics aimed at constructing feasible primal solutions. In this paper, we compare the main LR strategies used so far for stochastic hydrothermal unit commitment problems, where uncertainty mainly concerns water availability in reservoirs and demand (weather conditions). The problem is customarily modeled as a two-stage mixed-integer optimization problem. We compare different decomposition strategies (unit and scenario schemes) in terms of quality of produced lower bound and running time. The schemes are assessed with various hydrothermal systems, considering different configuration of power plants, in terms of capacity and number of units.

The advent of the COVID-19 pandemic led to an economic crisis of the construction industry and to an increasing of energy consumption in the residential sector for all the world. The European Union highlights the crucial role of building sector for both energy gains and economic growth, defining a “Renovation Wave” plan combining regulation, financing and technical support with the aim of greening the buildings, creating jobs and improving lives. In Italy a great support mechanism for energy refurbishment of existing buildings has been launched by means of tax deduction of 110% over 5 years. The present study aims to analyze this new funding mechanism, under energy, environmental and economic point of views. By means of a real case study, representative of highly widespread southern Italy HVAC-building system, it will be highlighting advantages and contradictions of the incentive mechanism developed, proposing possible future improvements. It is found that, if on one hand, the best refurbishment measure under energy/environmental point of view is the external insulation, windows replacement, electric heat pump and PV-system installation, with a global not renewable performance index reduction of 81%, on the other hand it is not the best solution considering the cost/saving ratio.

Abstract This paper deals with the problem of an infinite cylindrical heat source embedded into a saturated porous medium and subject to a cross-axial Darcian flow. Only forced convection is considered. We derived the transient dimensionless solution through a combined analytical – numerical method consisting of four steps: (a) a preliminary dimensional analysis of the constitutive equations of the problem in order to find the dimensionless groups governing the solution; (b) the identification of the validity range of the model as a function of the just-mentioned dimensionless groups; (c) the numerical resolution of the problem; (d) the synthesis of the numerical results in a general dimensionless form. Specifically, we provide several dimensionless maps of the 2D thermal field evolution for six different orders of magnitude of the Peclet number ( 10 - 3 – 10 2 ) . The evolution of the temperature of the heat source is fully illustrated and discussed through plain dimensionless criteria. Then, we discuss the time, space and fluid velocity scales in which the solution is practically equivalent to the ones given by a linear heat source and a purely conductive model. We conclude that the present model has to be employed to evaluate the temperature in proximity of the heat source when the reference Peclet number is greater than 0.5. On the contrary, the linear model can be successfully used for radial distances 5–10 times greater that the heat source radius, depending on the reference Peclet number.

Background: Phenolic compounds are food-derived bioactive compounds well-known for their antioxidant and anti-inflammatory properties. They are in the spotlight for the management of diabetes due to their positive effects on glucose homeostasis. Materials and methods: We have performed a literature review on the main topics related to the application of phenolic compounds as functional food ingredients. This includes extraction and purification from vegetable sources and agro-industrial by-products, encapsulation to improve their solubility and bioavailability, and preclinical and clinical evidence linking these compounds with anti-diabetic activity. Objectives: (1) provide an understanding of the role of phenolic compounds on diabetes; (2) identify green technologies for phenolic compounds extraction from agri-food by-products following a biorefinery scheme; (3) underline the relevance of encapsulation techniques using nanotechnology to improve their bioavailability; (4) discuss the therapeutic efficacy of polyphenols. Results: This review compiles recent relevant research on phenolic compounds extraction from renewable resources, their purification from agri-food by-products, and encapsulation strategies using eco-friendly processes. It also highlights the preclinical and clinical evidence on phenolic compounds’ antidiabetic activity, giving insight into their mechanisms of action. Conclusions: This review explores the latest advances in polyphenols and how their benefits in glucose homeostasis can be applied toward improving the health of patients with diabetes and related conditions.