Vehicular communications are expected to enable the development of Intelligent Cooperative Systems to be exploited for solving crucial problems related to mobility: road safety, traffic management etc. Information and Communication Technologies could also play a very important role in order to optimize the energy management of conventional, hybrid and electrical vehicles and, thus, to reduce their environment impact. In particular, vehicular communications could be used to predict driving conditions with the objective to determinate future load power demand. An adaptative energy management strategy for series hybrid electric vehicles based on genetic algorithm optimized maps and the SUMO (Simulation of Urban Mobility) predictor is presenter here. The control stategy paremeters are optimized over a series of possible mini cycles (duration $60s$) obteined by a K-means clustering algorithm. These references mini cycles are colled centroids. The centroids are abteined with respect at $60s$ time windowed standard driving cycles (UDDS, EUDC, etc) and realistic driving cycles acquired.

The present investigation describes the results of a research project (P.R.I.M.E.) aimed at testing the performance and the environmental impact of an electric city car in Italian cities. The vehicle considered in the project is the Daimler AG Smart ForTwo Electric Drive. A Smart ED vehicle was tested at the University of Salento for six months over different driving conditions (routes, traffic, use of auxiliaries). A data acquisition system has been designed on purpose and assembled on board to provide information about driving cycle and energy flows. The system was also used to evaluate the losses of energy during recharges due to the battery cooling system. The experimental tests were used to identify the average, minimum and maximum consumption of electricity in the Smart ED in Lecce according to driving conditions and in particular according to the usage of auxiliaries. The measured data of electric consumption have been used to quantify the emissions of CO2 and pollution of the vehicle using information about the Italian electricity production mix of each recharging event and the emissions factors of the Italian power plants with an innovative and comprehensive methodology.

Abstract: - A mobile test bench for testing energy management strategies for fuel cell hybrid electric vehicle has been obtained by modifying a Volksbot RT3 differential drive mobile robot. The robot provides the University of Salento with a low-cost system to test models and develop control strategies applicable to real scale vehicles. In fact, the prototype has been developed with the goal of implementing any control strategies by setting the instantaneous power split between the fuel cell and the batteries. H2Volks can be moved in two modes: a free mode that allow the user to simulate and acquire realistic driving cycles and a controlled mode that can be used to test different control strategies over the same driving cycle. In particular, a control strategy presented by the authors in a previous investigation has been implemented on the H2-VOLKS.

The present paper reports the experimental results and the potential performance of the investigation on flat solar thermal collectors using nanofluids as innovative heat transfer fluids for solar energy applications. The straight use of heat-transfer nanofluids in traditional solar flat panel revealed some technical issues, due to the nanoparticles sedimentation. Therefore, sedimentation has been investigated both in standard solar flat panels and modified ones made from transparent tubes. The results of the first tests showed that the main sedimentation parameter is the flow velocity and to better control it a standard flat panel was modified changing the cross-section of the lower and top header of the panel, that have been tapered to keep constant the fluid axial velocity. The modification of the panel shape (patent pending) enabled a negligible particles deposit. After different nanofluids were tested on the panel prototype, water–Al2O3 was chosen as heat transfer fluid. All tested nanofluids were prepared in batch and their thermal conductivity and convective heat transfer coefficient were measured prior of their use as heat transfer fluid in the solar panel. A thermal conductivity enhancement up to 6.7% at a concentration of 3 vol% was observed, while the convective heat transfer coefficient increased up to 25%.

The adoption of diesel LTC combustion concepts is widely recognised as a practical way to reduce simultaneously nitric oxides and particulate emission levels from diesel internal combustion engines. However, several challenges have to be faced up when implementing diesel LTC concepts in real application vehicles. In particular, achieving acceptable performance concerning the drivability comfort, in terms of output torque stability and combustion noise during engine dynamic transients, is generally a critical point. One of the most promising solutions to improve the LTC combustion operation lays in the exploitation of closed loop combustion control, based on in-cylinder pressure signals. In this work, the application of an in-cylinder pressure-based closed loop combustion control to a Euro 6-compliant demonstrator vehicle has been developed. The main challenges deriving from the control of the LTC combustion, directly affecting the engine/vehicle performance, have been analysed in detail. In order to overcome these drawbacks, a new control function, integrated into the base closed loop system, has been designed. The performance of the new function have been experimentally tested at the engine test bench. Results showed a significant enhancement of the LTC operation, in terms of both combustion stability and noise reduction during engine transients. The new function was also implemented on a real vehicle, thus proving the potential of the new control concept in realistic operating conditions.

This study demonstrates how it is possible to increase the performances of an air-cooled heat pump by the use of Horizontal Air-Ground Heat Exchanger (HAGHE); the analysis has been carried out varying the air flow rate and heat conductivity of the ground. For a warm climate, the air treatment using HAGHE involves an improvement of the Energy Efficiency Ratio (EER) of the heat pump for the entire summertime. About the wintertime, the coefficient of performance (COP) results improved from November to February, but it is possible to install a by-pass to permit to the heat pump to work at the best conditions.

The possibility to ignite the single wall carbon nanotubes (SWCNTs) containing impurities of iron in atmosphere once exposed to the radiation of a flash camera was observed for the first time in 2002. Afterwards, it was proposed to exploit this property in order to use nanostructured materials as ignition agents for fuel mixtures. Finally, in 2011 it was shown that SWCNTs can be effectively used as ignition source for an air/ethylene mixture filling a constant volume combustion chamber; the observed combustion presented the characteristics of a homogeneous-like combustion. In this paper a system for the ignition of an air/methane mixture is proposed, based on the exposition of multi wall carbon nanotubes (MWCNTs) to a low consumption flash camera. Namely, several experiments have been run in which 20 mg of MWCNTs, containing 75% in weight of ferrocene, have been added to an air/methane fuel mixture inside a constant volume combustion chamber. The mixture has been heated up to 373 K and the onset pressure was set equal to 3 bar. The experiments have been run varying the equivalence ratio in the range 1 - 2. The combustion process so realized has been compared to that obtained igniting the mixture with a traditional spark as in spark ignition engines. The comparison has been based on chamber pressure measurement as well as combustion process images, both sampled at a frequency equal to 2,5 kHz for an overall duration of 1.8 s. Results confirm that the ignition triggered with MWCNTs leads to a homogeneous-like combustion, without observing a well-defined flame front propagation. The contrary is observed, as expected, with the spark assisted ignition. Moreover, dynamic pressure measurements show that, compared to spark assisted ignition, the MWCNTs photo-ignition determines a more rapid pressure gradient and a higher peak pressure which corresponds to a higher energy release rate.

This paper presents a new analytic model for the estimation of the trapping efficiency of two-stroke engines using an extremely reduced number of measured physical variables. Mainly, the model estimates the trapping efficiency according to the Ostwald diagram, to the molal concentration of carbon dioxide and oxygen at tailpipe and accordingto the mass flow of air and fuel. In order to provide a measure of effectiveness for the proposed model, a use case has been chosen. The model’s effectiveness has been evaluated comparing its outcomes with the results obtained by thermo-fluid dynamic simulation of the use case on a 0D-1D commercial code, whose scavenging model has been previously validated by an extensive experimental activity. The present study shows that, for all the cases considered, the model results differ no more than 11% in absolute value from the simulated ones. In brief, the accuracy of the model allows the estimation of the trapping efficiency for two-stroke engines with reasonable confidence, reduced computational effort and time and costs lower than the currently available techniques.

A tool has been developed to integrate electric vehicles into a general systems for the energy management and optimization of energy from renewable sources in the Campus of the University of Salento. The tool is designed to monitor the status of plug-in vehicles and recharging station and manage the recharging on the basis of the prediction of power from the photovoltaic roofs and usage of electricity in three buildings used by the Department of engineering. The tool will allow the surplus of electricity from photovoltaic to be used for the recharge of the plug-in vehicles. In the present investigation, the benefits in terms of CO2 and costs of the scheduled recharge with respect to free recharge are evaluated on the basis of the preliminary data acquired in the first stage of the experimental campaign.

Il presente lavoro affronta lo studio delle tecniche di produzione di idrogeno, basate su cicli termochimici alimentati da impianti solari a concentrazione ad alta temperatura. In particolare, sulla base dei dati disponibili in letteratura relativi ai componenti costituenti l’impianto, si è sviluppato un modello in grado di produrre idrogeno sulla base del ciclo Zolfo-Iodio (S-I). Ogni componente dell’impianto proposto è stato caratterizzato in funzione dei flussi energetici e di massa e dimensionato in modo da definire le condizioni termodinamiche in ogni punto del sistema. I risultati hanno dimostrato che è possibile realizzare un impianto di produzione di idrogeno da fonte solare avente rendimenti di primo principio superiori al 44%. Inoltre prevedendo il recupero energetico dei cascami termici si è dimostrato che tale rendimento può essere notevolmente migliorato fino a valori prossimi al 65%. I risultati ottenuti rivelano le grandi potenzialità dei cicli termochimici di water-splitting basati sull’utilizzo della fonte rinnovabile solare per un passaggio verso l’economia dell’idrogeno. Il presente lavoro è stato sviluppato nell’ambito del progetto di laboratorio pubblico-privato SOLAR, finanziato dal MIUR.

I collettori parabolici lineari (PTC) costituiscono il tipo più comune di tecnologia solare termodinamica ad alta temperatura (HTST), in cui il fluido di lavoro è di solito olio sintetico o una miscela di sali fusi. Nel presente lavoro è stata svolta l’analisi di un collettore solare ad alta temperatura basato sull’impiego di nanofluido, quale fluido termovettore non convenzionale. A tal proposito, si evidenzia che i nanofluidi possiedono alcune proprietà che li rendono utili in molte applicazioni di trasferimento di calore. In quest’ottica, un'analisi termica ed un algoritmo di calcolo sono stati messi a punto per valutare le prestazioni di PTC, utilizzanti un nanofluido su base gassosa come fluido termovettore.

The European Directives promote the energy consumption assessment in residential and industrial sectors in order to identify specific measures for getting energy savings. This paper presents the results of the energy use analysis, carried out for a wine manufacturing firm located in Southern Italy. The energy consumptions of the main wine production processes are investigated, showing that the cooling is the most energy-intensive user. Potential actions as thermal insulation of storage tanks and integration of solar cooling system are proposed and analyzed in terms of energy saving to improve energy efficiency of the refrigeration process in the winery.

The energy planning based on Mean - Variance theory, guides the investors in investment decisions, trying to maximize the return and minimize the risk of investment. However, this theory is based on strong hypotheses and, in addition, input data are often affected by estimation errors. Moreover, this theory determines poor diversification increasing return and risk of the portfolio, and strong variability of the outputs when inputs are varied. In the first part of the paper, the Mean - Variance theory was applied to the energy generation in Italy; in particular, the analysis was on the actual energy mix, but also assuming the use of nuclear technology and taking into account verisimilar improvement, of technologies in the future. On the other hand, in the second part of the paper, a methodology has been applied in order to limit the problems of Mean-Variance theory applied to the energy mix settlement. In particular, the input variables have been calculated using Monte Carlo simulation, in order to reduce the estimation error, and the Resampled Efficiency TM technique has been applied in order to calculate the resulting new "average" efficient frontier. This methodology has been applied either not limiting or limiting the minimum and maximum percentage for every energy generation technology, in order to simulate constraints due, for example, to the technological characteristics of the plant, the availability of the sources and eventually to norms, to the territorial characteristics and to the socio-political choices. The application of Mean - Variance theory allowed to obtain energy portfolio, alternative to the actual, characterized by higher values of expected returns an lower values of risk. It was also shown that the application of the Resampled Efficiency TM technique with data originated with the Monte Carlo simulation effectively tackles the problems of Mean - Variance theory; in this way, the decision maker is helped in making decisions in the energy system policy and development. Thanks to this approach, applied in particular to the Italian energy contest, it was also possible to evaluate the effectiveness of the introduced modifications to the Italian actual energy mix to achieve the 2020 European Energy Directive targets in particular concerning the reduction of CO2 levels.

In this work, the efficiency of a 1 kWp horizontal-axis wind turbine installed on the roof of the Engineering building at the University of Salento has been evaluated, by means of CFD and experimental data. Particularly the influence of the building on the micro wind turbine performance has been studied and the numerical results (wind velocity fields and turbulence intensity above the building) have been compared with the experimental data collected over a period of time of three years. The results have shown that horizontal axis wind turbines suffer from wake effect due to buildings, therefore best sites in urban area have to be identified by a careful fluid dynamic analysis aimed at evaluating all causes that can reduce significantly the performance of the generator: in fact building should allow to exploit increased wind intensity, but often this advantage is voided by turbulence phenomena, as in the case under investigation where the measured aerogenerator efficiency is lower than the nominal performance curve. Then, the best site can be found by crossing the contours of wind velocity with the turbulence intensity fields: in this way it is possible to localize an area (best location) where the aerogenerator can gives maximum performance.

The main goal of the EPBD (Energy Performance Buildings Directive) is the improvement of the energy performance of the European buildings. The internal comfort is critically dependent on the envelope that plays a key role in the thermal balance of the entire building. In particular, the windows are one of the most critical elements in terms of solar gains, heat losses and thermal bridges; therefore, the design of high efficiency frames is requested, both in cold and warm climate, but with different peculiarity. The UNI EN ISO 10077-2 provides a methodology to evaluate the frame thermal behaviour and it proposes the criteria to validate the numerical model. This paper presents a two-dimensional numerical method for the thermal behaviour evaluation of the frame sections using GAMBIT 2.2 and ANSYS FLUENT 14.5 CFD code. The results have been validated in accordance with the UNI EN ISO 10077-2. The standard ISO replaces the air gas with a fictitious material “air solid” into the cavities. Besides the simulation carried out with ideal gas entails higher internal surface temperature than the air solid case. Therefore, the standard ISO imposes preventive computational conditions. The proposed numerical method can be implemented for several frame profiles with different features in terms of geometry and materials, representing a valid support in the design of new high thermal performance frames.

In this paper, the results of an extensive experimental campaign about dual fuel combustion development and the related pollutant emissions are reported, paying particular attention to the effect of both the in-cylinder charge bulk motion and methane supply method. A diesel common rail research engine was converted to operate in dual fuel mode and, by activating/deactivating the two different inlet valves of the engine (i.e. swirl and tumble), three different bulk flow structures of the charge were induced inside the cylinder. A methane port injection method was proposed, in which the gaseous fuel was injected into the inlet duct very close to the intake valves, in order to obtain a stratified-like air–fuel mixture up to the end of the compression stroke. For comparison purposes, a homogeneous-like air–fuel mixture was obtained injecting methane more upstream the intake line. Combining the different positions of the methane injector and the three possible bulk flow structures, seven different engine inlet setup were tested. In this way, it was possible to evaluate the effects on dual fuel combustion due to the interaction between methane injector position and charge bulk motion. In addition, methane injection pressure and diesel pilot injection parameters were varied setting the engine at two operating conditions. For some interesting low load tests, the combustion development was studied more in detail by means of direct observation of the process, using an in-cylinder endoscope and a digital CCD camera. Each combustion image was post-processed by a dedicated software, in order to extract only those portions with flame presence and to calculate an average luminance value over the whole frame. These luminance values, chosen as indicators of the combustion intensity, were represented over crank angle position and, then, an analysis of the resulting curves was performed. Results showed that the charge bulk motion associated to the swirl port, improving the charge mixing of the diesel spray and the propagation of the turbulent flame fronts, is capable to enhance the oxidation of air–methane mixture, both at low and high engine loads. Furthermore, at low loads, the analysis of combustion images and luminance curves showed that methane port injection can significantly affect the intensity and the spreading of the flame during dual fuel combustion, especially when a suitable in-cylinder bulk motion is obtained. Concerning the engine emissions, some correlations with what observed during the analysis of the combustion development were found. Furthermore, it was revealed that, for several combinations of the engine operating parameters, methane port injection was always associated to the lowest emission levels, demonstrating that this methane supply method is a very effective strategy to reduce unburned hydrocarbons and nitric oxides concentrations, especially when implemented with variable intake geometry systems.

This work presents an experimental investigation to determine the performance and characteristics of the combustion process triggered by a new ignition system based on photo-thermal effect, observed when nano-Energetic Materials are exposed to a flash light. The resulting combustion process has been compared with the one obtained using the spark-plug traditionally used in spark ignition engines. Results showed that the photo-thermal ignition determines higher combustion pressure gradient, peak pressure, total heat released, fuel combustion efficiency, and a shorter ignition delay and combustion duration compared with the spark ignition, for all the tested fuels and air-fuel ratios.

In order to satisfy the requirements of Directive 2010/31/EU for Zero Energy Buildings (ZEB), innovative solutions were investigated for building HVAC systems. Horizontal air-ground heat exchangers (HAGHE) offer a significant contribution in reducing energy consumption for ventilation, using the thermal energy stored underground, in order to pre-heat or pre-cool the ventilation air, in winter and summer, respectively. This is particularly interesting in applications for industrial, commercial and education buildings where keeping the indoor air quality under control is extremely important. Experimental measurements show that, throughout the year, the outside air temperature fluctuations are mitigated at sufficient ground depth (about 3 m) because of the high thermal inertia of the soil, the ground temperature is relatively constant and instead higher than that of the outside air in winter and lower in summer. The study aims to numerically investigate the behavior of HAGHE by varying the air flow rate and soil conductivity in unsteady conditions by using annual weather data of South-East Italy. The analysis shows that, in warm climates, the HAGHE brings a real advantage for only a few hours daily in winter, while it shows significant benefits in the summer for the cooling of ventilation air up to several temperature degrees, already by a short pipe.

The paper proposes an analytical methodology that uses empirical based models and CFD simulations to efficiently evaluate design alternatives in the conversion of a diesel engine to either CNG dedicated or dual fuel engines. The procedure is performed in five steps. Firstly, a database of different combustion chambers that can be obtained from the original piston is obtained. The chambers in the database differ for the shape of the bowl, the value of the compression ratio, the offset of the bowl and the size of the squish region. The second step of the procedure is the selection, from the first database, of the combustion chambers able to resist to the mechanical stresses due to the pressure and temperature distribution at full load. For each combination of suitable combustion chamber shape and engine control parameters (ignition/injection crank angle, EGR, etc.), a CFD simulation is used to evaluate the combustion performance of the engine. Then, a post-processing procedure is used to evaluate the detonation tendency and intensity of each combination. All the tools developed for the application of the method have been linked in the ModeFrontier optimization environment in order to perform the final choice of the combustion chamber. The overall process requires not more of a week of computation on the four processor servers considered for the optimization. Moreover, the selected chambers can be obtained from the original piston of the engine. Therefore, the conversion cost of the engine is quite small compared with the case of a completely new piston. The paper also describes the application of the procedure to two different engines.

Cooling of electronic devices is one of the main challenge of new generation technology. The extreme miniaturization has high benefits, but the heat to be dissipated per unit of surface increases in uncontrolled way. In this paper the application of a new generation of heat transfer fluids, nanofluids, to electronic devices is analyzed. Even if the use of nanofluids is not still common, there are many papers that deal with this topic, reporting both experimental and theoretical results. The development of this technology could be one of the key elements that could give an important impulse to further miniaturization of electronic devices and at the same time increase their energy efficiency.

An adaptative energy management strategy for series hybrid electric vehicles based on optimized maps and the SUMO (Simulation of Urban MObility) predictor is presented here. The first step of the investigation is the off line optimization of the control strategy parameters (already developed by the authors) over a series of reference mini driving cycles (duration of 60s) obtained from standard driving cycles (UDDS, EUDC, etc) and realistic driving cycles acquired on the ITAN500 HEV. The optimal variables related to each mini driving cycle are stored in maps that are then implemented on the ITAN500 vehicles. When the vehicle moves, a wireless card is used to exchange information with surrounding vehicle and infrastructure. These information are used by a local instance of the SUMO traffic prediction tool (run on board) to predict the driving conditions of the HEV in the future period of time T=60s. The predicted driving cycle is compared with the reference mini driving cycles and the most similar one is found. The optimal control strategy parameters mapped for that reference cycle are then used to select the power-split in the future time window. This process is repeated every T seconds obtaining an adaptative control strategy which do not requires much computational power on board. The proposed approach has been compared numerically with the “no knowledge” approach and the “full knowledge” approach. In the “no knowledge” case, the energy management was optimized for NEDC and then applied to three realistic driving cycles. In the “full knowledge” approach the energy management was optimized for each realistic driving cycle. The “full knowledge” approach allows the best fuel consumption to be obtained but requires the knowledge of the whole vehicle mission while the “no knowledge” method gives poor results since it cannot exploit the potentiality of a PHEV. The proposed approach allows good results to be obtained in terms of fuel consumption thanks to a better usage of the internal combustion engine.

This investigation describes the results of an experimental and numerical research project aimed at comparing mileage and CO2 emissions from two different commercial versions of Daimler AG Smart ForTwo car: conventional (gasoline) and electric (ED). The investigation includes numerical simulations with the AVL CRUISE software package and on-board acquisitions. A data acquisition system has been designed for this purpose and assembled on board of the Smart ED. The system is composed by a GPS antenna with USB interface, two current transducers, a NI-DAQ device and a netbook computer with a LabView-VI. This system provided on-board information about driving cycle and current flows, gathered simultaneously by GPS, transducers and NI-DAQ. The system was also used to evaluate the losses of energy during the recharge of the electric car. The two cars have been tested over a wide range of driving conditions related to different routes, traffic conditions and use of on-board accessories (i.e. Air Conditioning and radio). The CO2 emissions have been evaluated with a Well-to-Wheel approach.

The paper presents the results of an extensive experimental activity aimed at exploring the potentialities of improvement of an ICE operation, working in dual fuel modality, through the gaseous charge stratification. In this early experimental campaign, the engine under analysis, a single cylinder equipped with a common rail Diesel fuel injection system, has been fed with two gaseous fuels, hydrogen and methane, through an injector positioned along the intake duct, thanks to the facilities available in Machinery Laboratory at University of Salento, with which it is possible to mix up to five gaseous species (CO2, CO, H2, N2, CH4) freely setting the mixture composition and pressure. The gaseous mixture air-fuel has been introduced into the combustion chamber inducing a swirl bulk motion; once trapped into the cylinder, the gaseous mixture has been ignited injecting a small quantity of Diesel fuel, while the injector used for supplying the gaseous fuel has been positioned either upstream the intake duct, in order to obtain a more homogeneous gaseous mixture before it enters the cylinder, or just before the intake valve, so trying to obtain a stratified-like distribution of the fuel into the cylinder before the combustion start. During the tests, the value of several factors affecting the process of charge preparation have been varied: injection pressure of the gaseous fuel, quantity of Diesel fuel, in addition to the variation of the gas injector position. The effect of these factors has been evaluated on the behavior of the pressure in the combustion chamber, on the related heat release rate and on the pollutant emission levels at the exhaust.

The advancement of photovoltaic (PV) energy into electricity market requires efficient photovoltaic power prediction systems. Furthermore the analysis of PV power forecasting errors is essential for optimal unit commitment and economic dispatch of power systems with significant PV power penetrations. This study is focused on the forecasting of the power output of a photovoltaic system located in Apulia - South East of Italy at different forecasting horizons, using historical output power data and performed by hybrid statistical models based on Least Square Support Vector Machines (LS-SVM) with Wavelet Decomposition (WD). Five forecasting horizons, from 1 h up to 24 h, were considered. A detailed error analysis, by mean error and statistical distributions was carried out to compare the performance with the traditional Artificial Neural Network (ANN) and LS-SVM without the WD. The decomposition of the RMSE into three contributions (bias, standard deviation bias and dispersion) and the estimation of the skewness and kurtosis statistical metrics provide a better understanding of the differences between prediction and measurement values. The hybrid method based on LS-SVM and WD out-performs other methods in the majority of cases. It is also evaluated the impact of the accuracy of the forecasting method on the imbalance penalties. The most accurate forecasts permit to reduce such penalties and thus maximize revenue. © 2015 Elsevier Ltd. All rights reserved.

The paper analyzes data about recharge of electric cars in Rome during 2013 as a part of a national research project (P.R.I.M.E.). The electric vehicles were recharged through the public Enel Distribuzione recharging infrastructure. For each recharge, the initial and final time were registered together with the electricity absorbed from the grid. The total number of recharges was about 7700. The first step of the investigation is the statistical analysis of the distribution of recharges in daily time slots in order to analyze the recharge behavior of Italian drivers. For each day and for each time slot, literature data from the Italian national grid operator (Terna) were used to retrieve the energy mix used to produce electricity in that day and in that time slot. In the third step, electricity generation mixes were used to obtain emission factors for greenhouse (CO2) and pollutant emissions (CO, NOx, HC and particulate). Using information about the electric consumption of vehicles registered in Rome, the emission factors in g/km were obtained and compared with the limits set by European legislation for conventional (gasoline and diesel).

In urban areas, the evaluation of the energy outcome of a horizontal axis micro wind turbine depends on several factors such as mean wind velocity, location, turbulence, etc. To maximize the micro wind turbine efficiency it is important to define the best location. The present paper focuses on the definition of common rules for micro siting in urban areas. In this work, the efficiency of a 1 kWp horizontal-axis wind turbine has been evaluated, by means of CFD and experimental data. The numerical results have been compared with the experimental data collected over a period of time of three years, by using a measurement equipment installed on the roof of the Engineering building at the University of Salento. The results have shown that horizontal axis wind turbines suffer from wake effect due to buildings, therefore best sites in urban area have to be identified by a careful fluid dynamic analysis aimed at evaluating all causes that can reduce significantly the performance of the generator.

In this study, a modified flat panel solar thermal collector was built and thermal efficiency was measured with two heat transfer fluids: distillated water and Al2O3–distillated water based nanofluid at high concentration (3.0%) volume fraction of solid phase. In this work for the first time nanofluid with high nanoparticle concentration has been used thanks to a modified solar thermal collector, based on patent WO2011138752 A1, which consists in bottom and top headers properly shaped in order to reduce sedimentation of clusters of nanoparticles. Thermal efficiency has been measured through an experimental setup, according to EN 12975-2 standard. Experimental results showed that an increase of thermal efficiency up to 11.7% compared to that measured with water has been obtained by using nanofluid. Besides effect of nanofluid on thermal efficiency is greater at high temperatures.

The work reported in this paper shows experimental results from a study on a new type of heat transfer fluid, nanofluids, using diathermic oil as base fluid. These kinds of heat transfer fluids find application in those areas of heat transfer where high efficiency, compact volumes and high energy fluxes are required. In literature there are not many experimental data on diathermic oil based nanofluids because many experimental campaigns are focused on water nanofluids. On the other hand diathermic oil nanofluids are very important in those applications where high temperatures are reached or where the use of water is not suitable. Samples of nanofluids, with nanoparticles of CuO, Al2O3, ZnO and Cu, having different shapes and concentrations varying from 0.0% up to 3.0%, have been produced and their thermal conductivity has been measured by means of hot-wire technique, according to the standard ASTM D 2717-95. Measurements were carried out to investigate the effects of volume fraction, particle size of nanoparticles and thermal conductivity of base fluid. The effect of temperature has been also investigated in the range 20°C - 60°C. A dependence was observed on the measured parameters and the results showed that the heat transfer performance of diathermic oil enhances more than water with the same nanoparticles.

Energy procurement is a necessity which needs a deep study of both the demand and the generation sources, referred to consumers territorial localization. The study presented in this paper extends and consolidate the Shimon Awerbuch’s study on portfolio theory applied to the energy planning, in order to define a broad generating mix which optimizes one or more objective functions defined for a determined contest. For this purpose the computation model was specialized in energy generation problem and extended with the addition of new cost-risk settings, like renewable energy availability, and Black–Litterman model, which extends Markowitz theory. Energy planning was then contextualized to the territory: the introduction of geographic and climatic features allows to plan energy infrastructures on both global and local (regional, provincial, municipal) scale. The result is an efficient decision making tool to drive the investment on typical energy policy assets. In general the tool allows to analyze several scenarios in support of renewable energy sources, environmental sustainability, costs and risks reduction. In this paper the model was applied to the energy generation in Italy, and the analysis was done: on the actual energy mix; assuming the use of nuclear technology; assuming the verisimilar improvement of several technologies in the future.

The efficiency of cooling system is critical for wind turbines, particularly during the hot season, when high temperatures could damage the electric generator and mechanical parts of the turbine. The cooling system proposed in this paper is able to increase the efficiency of heat transfer with the use of nanofluids and the wind turbine tower as a heat exchanger to dissipate waste heat in the environment. In this study the use of Al2O3-water nanofluids has been considered. The results of this investigation appear encouraging because they have shown that the proposed new solution is able to assure highly efficient heat transfer and to limit thermal stresses on the electrical and mechanical components of wind turbines.

Dual-fuel biodiesel-producer gas combustion has shown potential in reducing nitric oxides and particulate emission levels compared to only diesel operation; however, engine overall efficiency is slightly penalized, while the main drawbacks are represented by the higher levels of total hydrocarbons and carbon monoxide emissions. In this work, the improvements in the combustion development deriving from the splitting of the liquid fuel injection at low loads have been assessed using a 0.51 L single-cylinder research diesel engine equipped with a high pressure common rail injection system and operated in dual-fuel mode. In this case, a synthetic producer gas was used as inducted gaseous fuel, while biodiesel was used as pilot fuel. Initially, the spray morphology was characterized in a constant-volume vessel for different values of injection duration and pressure, as well as vessel backpressure. Then, the experimental campaign, run on the engine at 1500 rpm, was divided in two sessions. During the former, only one pilot injection of constant fuel amount (11 mm3/cycle) was performed, the rail pressure was set equal to 500 or 1000 bar, the injection timing was varied in the range −50 ÷ 5 degrees crank angle after top dead center while the amount of gaseous fuel inducted in the cylinder was varied on three levels. During the latter, the pilot fuel amount, kept equal to the one pilot injection tests, was split in two smaller injections and the effect of the dwell between them – varied in the range 5 ÷50 degrees crank angle – was investigated as well. The results of the first set of experiments revealed that pilot injection timing and pressure both affect the combustion development. This resulted in sensible variations on thermal and combustion efficiencies, and therefore on fuel conversion efficiency, the last one exhibiting higher values with pilot injection timing slightly advanced respect to top dead center and lower injection pressure. In these conditions, total hydrocarbons and carbon monoxide are lowered, while nitric oxides are increased. The amount of gas demonstrated to have asecondary effect on combustion development and emissions levels at the exhaust. Splitting pilot injection, demonstrated to be an effective way to increase fuel conversion efficiency and to reduce the levels of all the pollutant species compared to the single pilot injection strategy. Based on the extensive experimental activity described in this paper, a dwell ranging between 10 and 30 degrees of crank angle, combined with a first injection timing ranging between 35 and 20 degrees of crank angle before top dead center guarantee the highest fuel conversion efficiency and the lowest pollutants emission levels. Injection pressure confirmed to be a significant factor in affecting the combustion development, while a secondary effect was determined by the gaseous mass inducted in the cylinder.Ultimately, pilot injection splitting demonstrated to be an effective way for improving gaseous fuel combustion in dual-fuel mode at low load (lean mixture) conditions.

In dual-fuel engines, a combustible mixture of air and generally a gaseous fuel is ignited, thanks to the injection and autoignition 6 of a small amount of liquid fuel. It is well-known that dual-fuel engines suffer from poor combustion when operated at low loads. This 7 behavior, due mainly to the presence of an overlean mixture into the combustion chamber, leads to unacceptably high levels of carbon 8 monoxide and unburned hydrocarbons emitted at the exhaust. In order to solve this problem a possible solution could be to split the pilot 9 injection of liquid fuel into two split injections, the second having the function of boosting the combustion of gaseous fuel also during the late 10 combustion phase. In this paper this solution has been implemented on a diesel common rail single cylinder research engine converted to 11 operate in dual-fuel mode. The composition of the gaseous fuel, indirectly injected, simulated a typical producer gas. The liquid fuel used 12 during the experiments was biodiesel, injected by means of a common rail injection system. The first section of results describes the tests run 13 for comparison purposes, performing only one pilot biodiesel injection and varying its timing on a wide range. The second section of results 14 then presents the tests run for different timings, varied on a wide range, of the first split injection, and different dwells between the first and the 15 second injections. The engine behavior has been discussed in terms of heat release rate, fuel conversion efficiency, and nitric oxides, total 16 hydrocarbons, and carbon monoxide emission levels at the exhaust. The results demonstrate that splitting the pilot injection leads to an 17 increase of fuel conversion efficiency and a reduction of both total hydrocarbons and carbon monoxide. This final result allows to state 18 that splitting the pilot injection is an effective way for sustaining the gaseous fuel combustion in dual-fuel engine late during the combustion 19 phase.

The Parabolic Trough Collector (PTC) is the most common type of high-temperature solar thermal technology, in which the heat transfer fluid is usually synthetic oil, molten salt or water/steam. Expe- riences in existing plants have shown some operating problems with all these types of fluid, which limit solar to thermal efficiency and increase power plant costs. To solve such constraints an innovative solar Transparent Parabolic Through Collector (TPTC) working with gas-based nanofluid has been proposed and investigated in the present paper. Transparent receivers combined with gas-based nanofluids were found to be able to directly adsorb solar radiation due to the very high total surface of nanoparticles. The use of directly radiated nano- particles allows compensating the relatively low heat transfer coefficient typical of gaseous heat transfer fluids with an increase of the exchange surface. Yet to allow a complete absorption of the solar energy within the transparent receiver tube a proper mixture of CuO and Ni nanoparticles has been designed. The proposed solar collector has been modelled by means of a discretized in space model to simplify the description of the behaviour of the physical system under the assumptions of quasi steady state conditions. The above-mentioned model has then been used to run an optimization procedure to define the main geometrical and operational parameters of the TPTC. Simulations have shown that the maximum TPTC solar to thermal efficiency is 62.5%, for a nanofluid outlet temperature of 650 C and a nanoparticles volume concentration of 0.3%.

Abstract {ZEBs} in Europe adopt a technology of light multi-layered walls by using structural materials with low density, thermal isolation, wide thickness, low specific weight, low mass accumulation, to achieve very low steady thermal transmittance. These techniques work toward bringing down winter heating costs. In the Mediterranean area, the thermal overload is irreversible when radiation is not controlled and the free supply of heat indoors is mismanaged. The characteristics of multi-layered walls do not yield typical passive heating system benefits because there are not large surfaces with thermal accumulation mass that are capable of storing heat when necessary, and discharge it once the effect of solar radiation is exhausted. A multi-objective analysis is key to obtaining several types of high energetic efficiency external walls for {ZEBs} in the Mediterranean climate, through the combination of various materials. The analysis is carried out in terms of steady thermal transmittance, periodic thermal transmittance, decrement factor, time shift, areal heat capacity, thermal admittance, surface mass, thickness. The results show that the superficial mass of the external wall has important to obtain the best performance in the warm climate. It is possible to reach high performance in the summertime also by lighter and thinner walls.

The recent worldwide environmental issues impose to reduce the energy consumption and the greenhouse gas emissions of the building sector, keeping in mind the whole life cycle of construction materials. The Itaca protocol (Institute for Innovation and Transparency of Contracts and Environmental Sustainability) promotes the use of recycled, renewable and locally sourced materials; in particular, the definition of product’s sustainability is complex, and the presence of one or more “eco” features does not necessarily make it “eco” in its entirety. A multi-objective analysis has been carried out in order to identify high energy efficiency external walls for Zero Energy Buildings (ZEBs) in the warm climate, privileging eco-friendly building materials. The definition of the external walls for Mediterranean climate with an optimal multilayer package through the integration of a multi-criteria optimization analysis was carried out in Modefrontier rel.4.3 environment with calculation procedures to evaluate the dynamic performance of building components developed in MatLab rel.7.0 environment. The optimization has been performed in terms of static transmittance, periodic thermal transmittance, decrement factor, time shift, areal heat capacity, thermal admittance, surface mass, thickness and Itaca score. The topic of this paper is to define a method for the design of high efficiency external walls of new low-cost residential buildings among which the designer can choose the proper solution for his application, according to the Pareto front of the multi-objective problem.

In this paper, the design of a double-loop fluidized bed solar reactor, involving CeO2 nanoparticles and two gas streams of N2 and CO2, for efficient thermochemical fuel production, has been optimized in a six-dimensional parameter space by means of a multi-parameter optimization algorithm. The system under investigation is capable to develop a thermochemical two-step cycle, producing CO by means of the overall reaction CO2→CO+1/2O2. The use of nanoparticles as catalyst allows maximizing the performance of the reactor; actually, nanoparticles increase surface area of reaction, with respect to common catalysts and, at the same time, allow realizing the reactor as double-loop fluidized bed, which can operate without alternating flows of CO2 and inert sweep gas. A genetic algorithm coupled with a quasi-random Sobol design population has been used, to find the optimal configuration of the double-loop fluidized bed solar reactor. The results highlighted the very important role of several factors, as radius of fluidized beds, mean residence time of reactor, mass of nanoparticles within reactor, solar concentration ratio, etc., on the performance of the system under investigation and allowed to find the best configuration of the system, reaching the mean global efficiency over a period of time of 1 year equal to 29.96%, with a maximum of 59.46%.

The potentials and characteristics of a new ignition system for air-fuel mixtures are discussed. This ignition method (referred to as photo-thermal ignition) is based on light exposure of Multi-Walled Carbon Nanotubes (MWCNTs), bonded with other nano-Structured Materials (nSMs), (collectively referred here as ‘‘nanoignition agent”), using a low-consumption camera flash. Here, Ferrocene, an organometallic compound, was used as the nSMs. Results from, and benefits of, this new ignition method are compared with a conventional spark-plug initiated ignition used in automotive engines. The main objective of this research is to demonstrate ignition feasibility of mixtures of both gaseous and liquid fuels with air under high pressures using the photo-thermal ignition (PTI) phenomenon. Specifically, the ignition and subsequent combustion characteristics of gaseous air-fuel mixtures at different air-fuel ratios were investigated by means of light exposures of nano-ignition agents (nIAs) after they are mixed with air-fuel mixtures. Analysis of the acquired data showed that for the range of air-fuel ratios tested, the photo-thermal ignition with a flash lamp resulted in a higher peak chamber pressure when compared to those obtained with a conventional spark ignition system. Heat release rate analysis showed that shorter ignition delays and total combustion durations for the Photo-thermal ignition are achieved. Comparative percent reduction of these values for photo-ignition ranges from 20% to 50% for LPG and methane, whereas values up to 70% were observed for the hydrogen. The positive impact of the photo-thermal ignition appears to be primarily at the ignition delay period of the combustion. With liquid fuels, photo-thermal ignition was capable to ignite mixtures as lean as a relative air-fuel ratio of 2.7 while the spark ignition was incapable to initiate combustion. Additionally, tests with the liquid gasoline injection highlighted that the combustion process with a higher ‘‘residence mixing time” exhibited higher peak pressures and shorter ignition delay times. High-speed camera images were used to capture images of the light emission during the combustion process in visible range, allowing investigation of the ignition processes. In particular, the results showed that the photo-thermal ignition process of the air-fuel mixtures with nano-ignition agents led to a spatially-distributed ignition followed by a faster consumption of the air-fuel mixture with no evidence of any discernible flame front formation or propagation.

One of the factors limiting the utilization of piston internal combustion engines for aircraft propulsion is the performance decrease increasing the altitude of operation. This is due to the negative effect of air density reduction increasing the altitude on cylinder filling. A solution to this problem is represented by the engine supercharging. Unfortunately, in two stroke engines, the cylinder filling efficiency is antithetical to the cylinder scavenging efficiency. With the aim of guaranteeing an optimal balance between engine performance and specific consumption, an engine breathing system optimization is needed. In this work, the results obtained running a multi-objective optimization procedure aiming at performance increase and fuel consumption reduction of an aircraft two stroke supercharged diesel engine at various altitudes are analyzed. During the optimization procedure, several geometric parameters of the intake and exhaust systems as well as geometric and operating engine parameters have been varied. Then, a multi-objective optimization algorithm based on genetic algorithms has been run to obtain the configurations optimizing the engine performance at Sea Level (take-off conditions) and fuel consumption at 10680 m (cruise conditions).

Super-critical mixing and combustion phenomena involves a large spectrum of interconnected physical processes which determine complexity in the problem formulation. Near critical or trans-critical condition the reacting mixture exhibits large variation in thermodynamic and transport properties, which affect drastically the mixing and combustion processes. The aim of this investigation is the implementation by user defined routines of thermodynamically consistent real gas mixing equation of state into the commercially available CFD-code ANSYS Fluent and the validation using experimental data. CFD simulations have been also performed by using different approaches: the Soave Redlich-Kwong real gas model and Peng Robinson have been implemented to model the physical properties of the species. This work is divided in two parts: in the first part a numerical analysis has been conducted to study the nitrogen high pressure flow in liquid rocket near the critical point , in the second the numerical study of the LOX/H2 and LOX/CH4 injection, mixing and combustion in liquid rocket engines with shear coaxial injectors, at supercritical conditions by using one-step reaction mechanism and detailed chemical kinetic reaction mechanism.

A numerical method, named WEST (Wind Energy Study of Territory), has been developed and applied to a specific geographical area in south of Italy. This method, through actual historical meteorological and geophysical data of a territory, allows characterizing anemometric fields and, therefore, potential available wind power. WEST has been developed in such a way to be effective in both studies of large area and siting. Particularly, this method is composed by different calculation algorithms, which altogether constitutes the numerical model, which allow obtaining useful information on the technical feasibility of installing wind turbine in an area. In this work, by means of WEST, three-dimensional wind fields of Apulia Region (Italy) have been reconstructed, obtaining the wind power density maps at several heights: 35 m, 60 m, 80 m and 100 m above ground level.

Lubrication of large two stroke marine diesel engines typically is performed by specially blended lubricants with high CaCO3 concentration in order to prevent sulphuric acid corrosion. The feed rate of lubricant, which is injected into the engine, is strictly related to neutralization reaction of sulphuric acid. At the state of the art, its amount is established following a function of engine load and sulphur content of fuel oil, but regardless the stoichiometric quantity needed to neutralize acid corrosion effects. As result of this lubrication strategy, feed rate of lubricant often results higher than the minimum stoichiometric quantity, yielding unnecessary costs, but sometimes feed rate of lubricant and its content of CaCO3 cannot be enough to completely neutralize sulphuric acid, producing corrosion. Taking into account that concentration of CaCO3 within lube oil can be estimated by measuring refractive index, this work aimed to study SPR sensors, capable to measure in real time small variation of lubricant optical properties, in order to adjust lubricant feed rate, according to the real needs of neutralization. Therefore, a numerical optimization of SPR sensors for lube oil characterization has been carried out, analysing several cases, different for laser source, optical prism and thickness of 3 metal film layers. Mathematical results allowed to find the best sensor in terms of sensitivity. This work is the first step towards the development of a semi-closed loop lubrication control system.

This work aims to develop an anaerobic digestion system, which allows recovering energy from olive wastes, solving the problem of their disposal. To reach this result, polyphenols, which are contained in olives inhibiting the digestion process, have to be abated. For this reason a new anaerobic digestion system able to treat the high concentration of polyphenols has been studied. Particularly, this system, composed by a storage of olive pomace, a mixing/washing unit, a pomace/water separation unit (decanter), an ultrafiltration unit and an anaerobic digester, has been numerically investigated to evaluate the anaerobic digestion key variables as a function of the hydraulic retention time (HRT), as well as the production of biogas for different values of the biomass yield factor. The results revealed that by abating polyphenols, the methane potential of the system under investigation rises from 7.5 molCH4/kgTSS to 11.7 molCH4/kgTSS, with an increment of about 56%, for HRT equal to 30 days.

A cost saving procedure for the optimization of a CNG converted diesel engine is proposed. The procedure is performed in five steps. Firstly, a database of different combustion chambers that can be obtained from the original piston is obtained. The chambers in the database differ for the shape of the bowl, the value of the compression ratio, the offset of the bowl and the size of the squish region. In the second step of the procedure, an empirical method is used to extract from the first database, only the combustion chambers able to resist to the mechanical stresses due to the pressure and temperature distribution at full load. For each combination of suitable combustion chamber shape and ignition timing, a CFD simulation is used to evaluate the combustion performance of the engine. Then, an empirical post-processing procedure is used to evaluate the detonation tendency and intensity of each combination. All the tools developed for the application of the method have been linked in the ModeFrontier optimization environment in order to perform the final choice of the combustion chamber. The overall process requires not more of a week of computation on the 4 processor servers considered for the optimization. Moreover, the selected chambers can be obtained from the original piston of the engine. Therefore, the conversion cost of the engine is quite small compared with the case of a completely new piston. The procedure can be applied to diesel engines to be converted to either CNG dedicated or dual fuel combustion. The main aspects and challenges to be taken into account in both cases are also analyzed.

Since more than one century, energy procurement worldwide has been based on liquid products obtained from refining of crude oil, a not-renewable energy source destined to the exhaustion. It is well known, however, that emissions produced by combustion of fossil fuels, containing CO2, CO, nitrogen and sulphur oxides, Volatile Organic Compounds and particulate, are harmful and cause environmental problems as well. A characterization of performance and pollutant emission levels was then conducted on a compression ignition engine fed with a diesel fuel-biodiesel mixture. In particular, five different blends of the two fuels were studied, and, for each of them, the EGR valve was set on four different opening values. For each of these operating conditions, cylinder pressure fluctuations were measured and heat release rate calculated; moreover, fuel consumption, together with NOx, CO2, HC and particulate matter (PM) levels have been measured. Data obtained from the experimental campaign indicate the biodiesel as an excellent substitute of the diesel fuel from the point of view of energy sources diversification, since its utilization leads to a reduction of HC emission levels equal to about 25% and of PM of about 20%. On the other hand, fuel consumption is increased of about 15% and NOx emission levels of about 30%.

Building integrated-mounted wind turbine (BUWT) is one of the most promising renewable energy devices. However, this renewable energy technology is not fully spread principally due to two factors such as uncertainty in the prediction of wind velocity and high turbulence intensity around the building. In this work, the Taguchi method and the analysis of variance (ANOVA) on a horizontal-axis wind turbine has been applied, to study the influence of geometrical parameters such as building depth, width and height, as well as turbine position on the roof and turbine height. To evaluate the above-cited effects, the airflow around an isolated building of parametrical dimension has been simulated using a Computation Fluid Dynamic (CFD) code calibrated against experimental data in a previous paper from the authors. The results reported in the present paper outline the relative effects of the main building geometrical parameters on the performance of a rooftop installed wind turbine and establish basic guidelines for the optimal location of such turbines.

This article describes the photo-induced ignition process of multi-walled carbon nano-tubes (MWCNTs)/ferrocene mixtures by pulsed Xe lamps using programmable driving boards with adjustable parameters, such as variable flash rate and pulse’s energy/intensity. Varying the energy of incident light pulse, minimum ignition energy values were found as a function ofmixture weight ratio, observing that a higherMWCNT amount with respect to metal nano-particles leads to lower ignition energy. The photo-induced ignition of CNTsmixed with nano-particles was then used iin a properly realized experimental setup for triggering the combustion of CNT-enriched fuel mixtures. Different types of gaseous fuels mixed with air (CH4, liquid propane, and H2) were tested. The combustion process triggered by MWCNTs/ferrocene photo-ignition shows better performances, for all used gaseous fuels and for all tested air/fuel ratios, compared with those obtained by using a traditional spark plug. In particular, CNT-based photo-induced combustion evolves more rapidly with shorter ignition delays, higher peak pressure values, and a higher fuel burning rate as observed by reported experimental tests.

In internal combustion engines, an ignition source is required to initiate the combustion process. This is commonly obtained either through an electric spark generation or by physical art of compression-ignition. In order to improve performance and lower pollutants levels, researchers have proposed alternatives to conventional ignition or combustion processes, such as Homogeneously-Charge Compression-Ignition (HCCI) combustion, whose critical operational requirement is precise control of the autoignition timing within the engine operating cycle. In this work, an innovative volumetrically-distributed ignition approach is proposed to control the onset of the autoignition process, by taking advantage of the optical ignition properties of carbon nanotubes when exposed to a low-consumption light source. It is shown that this ignition method enhanced the combustion of methane, hydrogen, LPG and gasoline (injected to chamber in liquid phase). Results for this new ignition method show that pressure gradient and combustion efficiency are increased, while combustion duration and ignition delay time are decreased. A direct observation of the combustion process indicates that these benefits are due to the spatially-distributed ignition followed by a faster initial consumption of the air/fuel mixture. The use of this ignition system is therefore proposed as a promising technology for the combustion management in internal combustion engines, specifically for HCCI engines.

This paper conducts an extensive experimental campaign for dual fuel biodiesel-producer gas combustion development and the related pollutant emissions and reports the results with the aim of highlighting the effect of biodiesel pilot injection parameters. For this purpose, a common rail diesel research engine was converted to operate in dual fuel mode; the gaseous fuel was introduced into the engine through an indirect injector housed well upstream of the engine intake duct; and the composition of the gaseous fuel simulating the producer gas was obtained using a mixing system able to generate a gaseous mixture of carbon monoxide (CO), hydrogen (H2), and nitrogen (N2) with the desired amount for each of them. The biodiesel pilot injection required to ignite the gaseous fuel was instead sprayed into the cylinder using a common rail high-pressure injection system. During tests, the biodiesel injection amount, pressure, and advance were varied on several levels, together with the composition and amount of gaseous fuel. The cylinder pressure was sampled and, from it, heat release rate and indicated mean effective pressure were estimated. Moreover, gaseous pollutant emissions at the exhaust were measured. The results demonstrate that biodiesel pilot injection parameters are crucial to control the development of combustion and emission levels when the engine is operated in dual fuel biodiesel-producer gas mode. Therefore, the potentialities of the common-rail high-pressure injection system may be developed to optimize as much as possible the operation of such engines in terms of power output, increase in combustion efficiency, and reduction of environmental impact.

Il presente lavoro affronta lo studio delle tecniche di produzione di idrogeno, basate su cicli termochimici alimentati da impianti solari a concentrazione ad alta temperatura.

The work reported in this paper shows the experimental results from a study on diathermic oil based nanofluids. Diathermic oil finds application in renewable energy, cogeneration and cooling systems. For example, it is used in solar thermodynamic or biomass plants, where high efficiency, compact volumes and high energy fluxes are required. Besides diathermic oil is very important in those applications where high temperatures are reached or where the use of water or vapor is not suitable. Therefore an improvement of diathermic oil thermo-physical properties, by using of nanoparticles, can increase the performance of the systems. In literature there are not many experimental data on diathermic oil based nanofluids because many experimental campaigns are focused on water nanofluids. Samples of nanofluids, with nanoparticles of CuO, Al2O3, ZnO and Cu, having different shapes and concentrations varying from 0.0% up to 3.0%, have been produced and their thermal conductivity has been measured by means of hot-wire technique, according to the standard ASTM D 2717-95. Measurements were carried out to investigate the effects of volume fraction, particle size of nanoparticles on the thermal conductivity of the nanofluid. The effect of temperature has been also investigated in the range 20°C - 60°C. A dependence was observed on the measured parameters and the results showed that the heat transfer performance of diathermic oil enhances more than water with the same nanoparticles.

The recent worldwide environmental issues impose to decrease the energy consumption and the greenhouse gas emissions from the construction sector. To improve productivity and to decrease the negative effects on the environmental and social activities, particular attention is placed on precast systems. A multi-objective analysis has been carried out in order to identify high energy efficiency external walls for Zero Energy Buildings (ZEBs) in warm climate, encouraging eco-friendly building materials. The definition of the external walls for Mediterranean climate has been carried out through the integration of a multi-criteria optimization. ModeFRONTIER rel.4.3 environment has been used with calculation procedures to evaluate the dynamic performance of building components developed in MatLab rel.7.0 environment. The optimization has been carried out in terms of steady thermal transmittance, periodic thermal transmittance, decrement factor, time shift, areal heat capacity, thermal admittance, surface mass, small thickness, eco sustainability score, light-weight and costs. The results shows the possibility to reach high energy performance with light and thin solutions, considering the superficial mass and the internal areal heat capacity. The best solutions present repetitive features: high surface mass for the first layer (internal side), eco-friendly insulating materials for the middle layers and common insulating materials for the outer layer. The aim is to show a method to design high efficiency precast external walls of new low-cost residential buildings among which the designers can choose the proper solution for his application, according to the Pareto front of the multi-objective problem.

Gli impianti solari termodinamici ad alta temperatura sono prevalentemente basati sull’impiego di collettori parabolici lineari (CPL), utilizzanti come fluido di lavoro olio sintetico o una miscela di sali fusi. Solo recentemente è stato avviato lo studio di CPL, impieganti aria come fluido termovettore, con notevoli problemi di carattere tecnologico legati alla concomitanza di elevate pressioni e temperature all’interno dell’impianto. Nel presente lavoro si propone lo sviluppo di un collettore parabolico lineare con ricevitore trasparente in quarzo (CPLT), impiegante, quale fluido termovettore, un nanofluido a base aria. Negli ultimi anni, i nanofluidi sono stati al centro di numerosi studi in ambito nazionale ed internazionale, grazie alle migliorate proprietà di scambio termico (rispetto al fluido base), utili in molte applicazioni di trasferimento di calore. Una proprietà ancora poco esplorata, da un punto di vista applicativo, dei nanofluidi, è quella dell’assorbimento diretto dell’energia solare. Tale principio fisico è alla base del funzionamento del collettore solare oggetto del presente lavoro. Difatti, differentemente dalle soluzioni tecnologiche fino ad oggi esplorate, l’energia solare concentrata sul ricevitore in quarzo trasparente, può essere assorbita direttamente dal nanofluido che scorre al suo interno, incrementando in tal modo le performance di captazione del sistema. Inoltre, rispetto ai primi tentavi di impianti solari termodinamici con fluido termovettore aria, l’impiego del nanofluido consente di incrementare in modo significativo la capacità termica del fluido termovettore, riducendo drasticamente le pressioni di lavoro del sistema. Ciò permette di risolvere parte dei nodi tecnologici ed incrementare i livelli complessivi di sicurezza dell’impianto. In quest’ottica, nel presente lavoro è stato svolto un processo di ottimizzazione dei parametri funzionali di un CPLT (temperature e portate di lavoro, concentrazione di nanoparticelle) raggiungendo un rendimento solare-termico teorico di esercizio pari al 66.74% ad una temperatura di ingresso del nanofluido di 473 K.

Nel presente lavoro si propone lo sviluppo di un collettore parabolico lineare con ricevitore trasparente in quarzo (CPLT), impiegante, quale fluido termovettore, un nanofluido a base aria. In particolare è stato svolto un processo di ottimizzazione dei parametri funzionali di un CPLT (tempera- ture e portate di lavoro, concentrazione di nanoparticelle) raggiungendo un rendimento solare-termico teorico di esercizio pari al 66.74% a una temperatura di ingresso del nanofluido di 473 K.

The effects of several operating parameters on dual fuel combustion at light load were investigated by means of direct endoscopic observation of the process. Therefore, an intense experimental campaign was performed on a single cylinder diesel common rail research engine, converted to operate in dual fuel mode and equipped with optical accesses and variable intake configuration. Three bulk flow structures of the charge were induced inside the cylinder by activating/deactivating the two different inlet valves of the engine (i.e. swirl and tumble). Methane was injected into the inlet manifold at different pressure levels and varying the injector position. In order to obtain a stratified-like air-methane mixture, the injector was mounted very close to the inlet valve, while, to obtain a homogeneous-like one, methane was injected more upstream. By combining the different positions of the methane injector and the three possible bulk flow structures, seven different engine inlet setup were tested. Moreover, pressure and quantity of the diesel pilot injection were varied. For each acquired combustion image, the luminance plane was extracted and a luminance value, averaged over the whole frame, was calculated in order to obtain an indicator of the combustion intensity. These crank angle-based luminance curves were compared while the total integral and the peak values were calculated. From the analysis of the luminance curves it can be observed that the in-cylinder bulk flow associated with the swirl port is characterized by a more rapid development of the combustion. Especially for certain combinations of the engine operating parameters, higher peaks of luminance values can be noticed while the luminance curves fall to zero earlier with respect to the other inlet configurations. Concerning the methane injector position, some noticeable effects on the intensity and distribution of the flame during dual fuel combustion were observed. Depending on the bulk flow structure induced inside the cylinder, methane injector position can induce a certain degree of stratification of the in-cylinder charge, capable to enhance dual fuel combustion at low loads.

Different studies on both 2- and 4-stroke engines have shown how the choice of different supercharging architectures can influence engine performance. Among them, architectures coupling one turbocharger with a mechanical compressor or two turbochargers are found to be the most performing in terms of engine output power and efficiency. However, defining the best supercharging architecture for aircraft 2-stroke engines is a quite complex task because the supercharging system as well as the ambient conditions influence the engine performance/efficiency. This is due to the close interaction between supercharging, trapping, scavenging and combustion processes. The aim of the present work is the comparison between different architectures (single turbocharger, double turbocharger, single turbocharger combined with a mechanical compressor, single turbocharger with an electrically-assisted turbocharger, with intercooler or aftercooler) designed to supercharge an aircraft 2-stroke Diesel engine for general aviation and unmanned aerial vehicles characterized by a very high altitude operation and long fuel distance. A 1D model of the engine purposely designed has been used to compare the performance of the different supercharging systems in terms of power, fuel consumption, and their effect on trapping and scavenging efficiency at different altitudes. The analysis shows that the engine target power is reached by a 2 turbochargers architecture; in this way, in fact, the cylinder filling, and consequently the engine performance, are maximized. Moreover, it is shown that the performance of a 2 turbochargers architecture performance can be further improved connecting electrically and not mechanically the low pressure compressor and turbine (electrically-assisted turbocharger). From an energetic point of view, this system has also proved to be particularly convenient at high engine speed and load, because it is possible to extract power from the electric turbocharger without a penalty on specific fuel consumption.

Obiettivo del lavoro è l’analisi del fenomeno della sedimentazione dei nanofluidi all’interno di pannelli solari piani, finalizzata ad adottare gli accorgimenti necessari alla sua attenuazione o alla sua completa eliminazione. Lo studio è condotto su pannelli a tubi trasparenti attraverso analisi ottica. In una fase iniziale si è realizzato un pannello solare piano a tubi trasparenti, con le dimensioni di un classico pannello disponibile in commercio, all’interno del quale si è fatto fluire un nanofluido a base di acqua e ossido di alluminio (Al2O3). Le zone interessate dalla sedimentazione della fase solida erano il tubo collettore di ingresso, quello collettore di uscita e i tubi traversi La quantità di fase solida depositata è risultata essere dipendente dalla velocità del nanofluido nei tubi di ingresso e di uscita. Nella fase successiva si è realizzato un pannello solare piano, delle stesse dimensioni del precedente, con una modifica sui tubi di ingresso e di uscita, volta a eliminare il fenomeno della sedimentazione per effetto di una opportuna variazione di velocità del nanofluido. La forma era tale da garantire una velocità costante lungo tutta la loro lunghezza. Essa è stata ottenuta agendo sulla sezione di passaggio all’interno dei tubi attraverso l’introduzione di un solido opportunamente sagomato. Il nanofluido utilizzato era a base di acqua e Al2O3 ed era alimentato nelle stesse condizioni adottate per il pannello della prima fase. Per effetto delle modifiche apportate il fenomeno di sedimentazione si è ridotto a livelli trascurabili e, in certi punti, è stato completamente eliminato. Il pannello solare modificato, dotato di tubi a sezione variabile, è stato oggetto di domanda di brevetto per invenzione industriale depositata all’Ufficio Italiano Brevetti e Marchi (N° LE2010A000006) e successivamente è stata depositata anche la domanda di brevetto internazionale (Application number: PCT/IB2011/051988).

Le pompe di calore geotermiche hanno avuto in Italia nell’ultimo decennio sviluppo e diffusione grazie soprattutto al fatto che consentono consistenti risparmi energetici quando utilizzate per soddisfare il fabbisogno di climatizzazione estiva e invernale degli edifici. In questo lavoro vengono analizzati i diversi modelli matematici presenti in letteratura per il calcolo delle prestazioni delle pompe di calore dotate di scambiatori orizzontali e verticali e per le relative metodologie di dimensionamento semplificate. A seguito dei risultati di questa analisi è stato concepito e implementato un modello matematico in ambiente Matlab-Simulink che integra le metodologie per la progettazione dei sistemi geotermici verticali e orizzontali e valuta le potenze termiche scambiate con il terreno correggendo i valori tabellari di riferimento e largamente in uso nella progettazione semplificata degli impianti di piccola taglia, in funzione delle particolari condizioni operative. Il modello è tarato con il riferimento a risultati sperimentali e ai valori in uscita dalle procedure di calcolo del software RETScreen.

La valutazione dell’impatto acustico generato da una installazione eolica richiede la conoscenza delle caratteristiche del suono emesso e le modalità con cui questo si propaga in campo aperto. Gli strumenti attualmente disponibili per tale analisi previsionale fanno riferimento, per la maggior parte, al modello standard proposto dalla ISO9613-2, e partono dall’assunto che una turbina eolica sia rappresentabile da una sorgente di rumore puntuale, la cui direttività è tenuta in considerazione solo in modo approssimato. Per valutare le caratteristiche della direttività, infatti, non vi sono in letteratura sufficienti riscontri sperimentali che consentano di apprezzarne la reale efficacia e/o i limiti dei modelli che si stanno adoperando. Lo scopo del presente lavoro, quindi, è validare, attraverso rilievi fonometrici eseguiti presso installazioni eoliche esistenti, un modello semplice che permetta di valutare ante operam il campo acustico prodotto da una installazione eolica tenendo in conto le caratteristiche di direttività del rumore emesso dalle turbine.

The study focuses on wind-waves-bottom characterization as first step in the feasibility evaluation of an offshore windfarm in the offing of Apulian coast - Italy. Planning offshore windfarm, hydrodynamic and aerodynamic fields, and their interaction, must be investigated. Waves studies and their transformation due to diffraction, shoaling, refraction, etc. are fundamental to predict the effects that sea could have on turbine's foundation, especially for floating turbine, mooring lines, structural stress and moreover to consider the influence that frequently high waves may have on installation, operation and maintenance. In this study, starting from wind data and a nautical map, a good determination of the wave motion has been obtained. Particularly, three-hours measurements of wind intensity and direction, by on-land anemometer, have been used. Wind data of a period of time of 45 years, from 1951 to 1996, have been statistically processed to extract the most relevant winds with velocity and duration bigger than 10 knots and 6 hours respectively. Using the nautical map of the area under investigation, the sea bottom morphology has been reconstructed to obtain a model of bathymetry. After that, the bathymetric curves have been traced on the map, converted in a depth matrix and then transformed into an interpolated grid point. Subsequently, the assessment of waves propagation has been obtained through both Jonswap Spectrum and SPM method and the results have been compared. Finally, the wave heights and peak periods were calculated with reference to return period of fifty years and used as input in two model: Nearshore Spectral Waves (NSW) model and Parabolic Mild Slope Spectra Waves (PMS) model. In conclusion, this study can represent a useful approach to plan an offshore windfarm.

Solar concentration system with thermo-vector fluid made up of gas-based nanofluids and with suitably shaped receiver element of the solar radiation.

New Graeztel cell (or DSSC: dye-sensitized solar cell) provided with a refilling system both of the electrolyte and the organic dye (dye).

Solar concentration system with thermo-vector fluid made up of nanofluids and with suitably shaped receiver element of the solar radiation.

Solar collector for applications with nanofluids or biphasic heat transfer fluids, including both a top pipe ( 1CT) and a bottom pipe ( 1CB ) wherein at least one of these pipes has a variable cross section in order to avoid sedimentation of nanofluids and other biphasic heat transfer fluids that flow inside the tubes of the solar collector itself.