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Scuola di Dottorato "Pitagora" in Scienze Ingegneristiche, XXI Ciclo, a.a. 2015-2016 Università della Calabria

La necessità di monitorare le vibrazioni sulle strutture e su elementi meccanici assume notevole importanza. Mantenere sotto controllo strutture vetuste, infrastrutture e macchinari ricopre un ruolo strategico nella prevenzioni di situazioni che potrebbero destabilizzare, o finanche distruggere, le strutture stesse. Recenti sviluppi nei sistemi Micro Elettro Meccanici (MEMS), hanno reso gli accelerometri MEMS uno strumento attraente per il monitoraggio dello stato in cui versano diverse tipologie di strutture (SHM). Fino ad ora, la scarsa sensibilità e la bassa risoluzione dei sensori adoperati, specie alle bassissime frequenze, hanno costituito una seria limitazione per il monitoraggio di grandi strutture. Convenzionalmente, i segnali analogici in uscita dagli accelerometri MEMS sono convertiti in segnali digitali prima di essere trasmessi tramite radio-frequenza (RF). La conversione può causare perdita di accuratezza nell’analisi dei segnali caratterizzati da bassa frequenza e piccola ampiezza, che sono d’interesse nel campo dello SHM. Al fine di ovviare a tale limitazione, un nuovo sistema per la valutazione di accelerazioni (ALE) è progettato e realizzato in questo studio. ALE converte il valore di tensione in uscita dall’accelerometro MEMS in un segnale modulato in frequenza (FM) prima della radiotrasmissione. Per fare ciò, è adoperato, al posto del tradizionale Convertitore Analogico Digitale (ADC), un convertitore Voltaggio – Frequenza (V/F). Il prototipo realizzato in questo studio è formato da due schede: una trasmittente e una ricevente. La prima unità è equipaggiata con il suddetto accelerometro MEMS, un convertitore V/F e un’antenna trasmittente; la seconda, invece, per demodulare il segnale ed inviarlo ad una scheda di acquisizione dati (DAQ) collegata ad un computer, utilizza un’antenna ricevente e un convertitore Frequenza – Voltaggio (F/V). L’efficacia del prototipo realizzato, nel misurare sollecitazioni dinamiche caratterizzate da bassissime frequenze e piccole ampiezze, è valutata per dimostrare la possibilità di utilizzo di ALE nelle analisi SHM. Per fare ciò, sono state effettuate prove di laboratorio ed esperimenti su differenti strutture reali. Le prime consistono in calibrazioni statiche, studi sugli effetti che la carica residua delle batterie può avere sul comportamento delle schede, prove per valutare la distanza massima alla quale il sistema RF può trasmettere, e una serie di misure comparative con accelerometri cablati. Le seconde, invece, consistono in una serie di misurazioni effettuate su diverse tipologie di sistemi dinamici: una condotta per il trasporto di carburante (applicazioni industriali), una guglia in pietra di un edificio storico (applicazioni sismiche) e un ponte pedonale (monitoraggio di infrastrutture civili). In questo studio sono discussi i risultati raggiunti e fornite indicazioni utili per possibili futuri sviluppi del prototipo. Scuola di Dottorato Pitagora In Scienze Ingegneristiche, Ciclo XXVII,a.a. 2014 Università degli Studi della Calabria

In recent years, research has shown a growing interest in the use of hybrid wind photovoltaic (PV) systems that provide better performance compared to the use of a single component due to complementarity in meeting electricity demand. Over the past twenty-five years, hundreds of articles have addressed the topic of hybrid systems considering different configurations and final uses and, over the past decades, many reviews have made a comprehensive summary of various results obtained. However, some reviews deal with the research in a too general and qualitative way, without providing quantitative data, and other reviews are too focused on a specific topic aspect. To provide a qualitative-quantitative prospect of the research trend in the last twenty-five years, the present work is aimed at carrying out a literature review and statistical analysis starting from data extracted from the 550 most relevant and recent articles concerning hybrid systems, published between 1995 and 2020. The review aim was to produce an upgradable matrix literature database that schematizes the content of all articles in terms of different categories, such as the geographical distribution, their component configurations, operating mode and the auxiliary components used to support it, their intended uses and study methodologies (simulation, experimental, economic, energy, environmental and social analysis etc.) and software used. In addition, all the optimization algorithm, energy, economic, environmental and social indicators available in the literature were extracted and elaborated to identify the most used. The 550 articles were analysed, compared, and classified into several categories to provide an overall framework of the state of the art. The objective is to clearly and appropriately show important trends and findings in the development of hybrid wind and solar PV experimental, simulation and optimization projects. Data are elaborated to obtain a statistical analysis for each category or a combination of categories. In particular, the analysis highlighted that research is more focused on testing systems in warm or temperate localities, with the Koppen climate groups B and C prevalent over the others. From the geographical point of view, Asia is the continent most involved in world research (with China, India and Iran the first three countries for total publications produced). However, also in other parts of the world, a growing interest was noticed in this technology. The prevalent tested system configuration mode is the stand-alone hybrid systems, in a wide variety of climates and especially for residential uses. Simulations are mostly implemented in the analysed publications, mainly through HOMER and MATLAB software. Parametric analysis is widely used for optimal system design with a large variety of techniques. In particular, the system performance is examined mostly from an energy point of view. Economic analysis is also very common, alone or in combination with energy analysis. The most frequently used optimization algorithms are the particle swarm optimization (PSO) and genetic algorithm (GA), while the loss of power supply probability (LPSP) and renewable fraction (RE) for the energy analysis, the net present cost (NPC) and cost of energy (COE) for the economic analysis and the emissions (E) of CO2 for the environmental analysis are most widespread indicators. Finally, an analysis on the size of the system components is performed to study which renewable source is more preferred at low and high installed power, for stand-alone, grid-connected systems and overall, considering different intended uses. The analysis highlights that PV systems are preferred at low installed powers, especially for residential use and stand-alone mode, while wind systems, in addition to being extensively used for low installed powers, demonstrates higher employment compared to PV systems as the power increases. The paper findings and upgradable matrix literature database are proposed as a valuable tool for engineers, experts and national and international policymakers.

This dataset supports the research article “Complete greenhouse dynamic simulation tool to assess the crop thermal well-being and energy needs” [1] . In the agricultural sector, the use of energy can be very intensive [2] and the simulation of solar greenhouses is a very complex work [3] . This dataset provides the results of thermal modeling and dynamic simulation of a solar greenhouse considering simultaneously several thermal phenomena. The analysis was performed by TRNSYS 17 software (TRaNsient SYstem Simulation). The results obtained consider different phenomena that affect the thermal behavior of the greenhouse, including evapotranspiration produced by plants, heat exchange with the soil and the presence of artificial lights. Different models are presented for the calculation of the convective coefficient that best suits the presence of glass surfaces, considering the different discretization of the internal volume (single thermal zone and twenty thermal zones). The parameters that influence the thermal behavior of the greenhouse are analyzed on an hourly basis, the model has been validated with EnergyPlus. The data allow the researcher to choose a suitable greenhouse model in the case of free-floating model or in the presence of an air conditioning system.

The data describe supplementary materials supporting the research article entitled “Worldwide geographical mapping and optimization of stand-alone and grid-connected hybrid renewable system techno-economic performance across Koppen-Geiger climates” (Mazzeo et al., 2020). Hybrid renewable energy systems are increasingly adopted worldwide as technically and economically effective solutions to achieve energy decarbonization and greenhouse gas reduction targets. This data article includes the results of worldwide techno-economic optimization of stand-alone and grid-connected photovoltaic-wind hybrid renewable energy systems designed to meet the electrical energy needs of an office district. The technical simulations have been performed in TRNSYS 17 (Transient Energy System) environment. A total of 48 different locations around the world have been chosen across Koppen-Geiger climates with different latitudes and homogeneously distributed over the whole globe, considering very different climates. The analyses have been conducted for 343 different system power configurations, considering both stand-alone and grid-connected systems. A total of 16464 dynamic simulations were performed, summarized in yearly energy output from each component and in energy and economic indicators.

Greenhouse technology is an important energy consumer sector representing an indispensable solution for modern methods of crop production. In the greenhouse envelope and system design phase, thermodynamic performance simulation tools are required. The greenhouse simulation is still a very complex task despite many building tools are available in the literature. This work aims to overcome this gap by proposing a reference methodology to accommodate the building TRNSYS software for a greenhouse able to consider simultaneously different thermal phenomena with detailed modelling of: dense volume discretization, 3D shortwave and longwave radiative exchange, air flow exchanges, presence of lamps with their exact 3D position, ground and plant evapotranspiration, and convective heat transfer coefficients. A standard hourly simulation of the one-zone greenhouse was validated with another recognized tool, showing excellent agreement throughout the year. The main parameters affecting the greenhouse thermal balance were investigated in both a free-floating and continuous regime. The investigation has shown that a standard simulation is accurate to only reproduce the thermal response in a free-floating regime; instead, the detailed simulation has led to overall cooling and heating energy needs in the continuous regime, respectively, of 51.4 kWh/m3 and 49.1 kWh/m3, avoiding to obtain very high errors.

In the last years, a significant interest in research in stand-alone (SA) and grid-connected (GC) photovoltaic (PV)-wind hybrid renewable energy systems (HRES) is observed for their complementary in the satisfaction of the electrical energy demand in many sectors. However, direct comparisons between the techno-economic performance of two system modes under the same operating conditions are rarely carried out. Additionally, most of the researches are limited to specific weather conditions. This work aims to bridge the lack of this type of investigations providing a worldwide techno-economic mapping and optimization of SA and GC PV-wind HRES to supply the electrical demand of an office building district. For this purpose, energy and economic optimization problems were formulated to find the optimal SA and GC systems worldwide among 343 HRES system power configurations located in 48 different localities, uniformly divided in the sub-group of the Koppen classification. The energy reliability and economic profitability of optimal systems were geographically mapped worldwide. In general, the energy or economic optimizations of SA HRES do not lead to highly profitable systems; instead, feed-in-tariff to sell the energy in excess assures viable GC HRES in many localities. However, economically optimal SA and GC HRES, respectively, do not everywhere comply with the threshold value of 70% of the satisfied energy required by the load and are characterized by a high level of energy exchanged with the grid. The study highlighted that the most suitable climate conditions to install a SA HRES are: (i) Toamasina (Madagascar) from an energy point of view, with 76% of load satisfied and 76% of the energy generated utilized to supply the load; (ii) Cambridge Bay (Canada) from an economic point of view, with 11.1% of the capital cost recovered each year; instead, the most suitable climate conditions to install a GC HRES are: (iii) New Delhi (India) from an energy point of view, with 48% of energy exchanged with the grid per each kWh required by the load; (iv) Lihue (Hawaii, United States) from an economic point of view, with 24.3% of the capital cost recovered each year.

The growth of economies and the world population has led to an increase in the electricity demand, toward a disproportionate use of fossil fuels. The PV-wind hybrid system is considered an optimal solution in terms of technical efficiency and costs to reduce the use of fossil sources. The strong variability of renewable energies generated by solar and wind systems in different locations around the world sometimes leads to the need to use battery storage systems. In addition, the self-consumed energy produced by the hybrid system is strongly dependent on the load trend. Owing to the strong influence of the climatic conditions on a hybrid system energy performance, its optimal sizing is a very complex issue that must be addressed in each weather condition. This paper presents an energy feasibility study of a PV-wind-battery hybrid system considering different yearly climatic conditions in the world, according to the Koppen classification. The system is used to supply electrical energy to a district composed of five office buildings. The electrical load consists of artificial lighting systems, electrical office devices and electric vehicle charging stations. The effects produced by different yearly climatic conditions on three hybrid systems, characterized by the same overall nominal powers and different photovoltaic and wind nominal powers, were investigated. TRNSYS 17 was used for the dynamic simulation of the hybrid system. The overall aim is to identify the most proper climatic conditions by means of the optimization of several energy indicators: maximization of the self-consumed renewable energy and of the renewable energy produced utilized to supply the load, namely minimization of the energy imported from and exported to the grid. For this issue, a global indicator, that measures the energy exchange of the hybrid system and load with the grid, is proposed to select the optimal trade-off localities and hybrid systems.

Electric production data of a grid-connected hybrid system are presented. The system consists of a photovoltaic generator, a wind micro-generator in the presence (HPWBS) or absence (HPWS) of an electric storage system. In such a system, the power generated by RES (Renewable energy sources) is sent directly to balance the load.A residential use has been analysed in warm climate. The analysis has been carried out by TRNSYS 17 (Transient System Simulation) software and the mathematical modelling and the energy balance of the system have been shown in “Energy reliability-constrained method for the multi-objective optimization of a photovoltaic-wind hybrid system with battery storage” [1]. The annual energy performance has been evaluated, in terms of dimensionless balance of the generated energy and dimensionless balance of the energy required by the load, for 375 hybrid system configurations. These configurations were obtained by varying the photovoltaic power, the wind power and the battery storage capacity, considering different hourly average daily values of the load.

A multi-objective optimization method for the dimensioning of hybrid photovoltaic-wind-battery systems HPWBS characterized by high-energy reliability is proposed. The energy reliability-constrained (ERC) method permits choosing the most proper indicators combination to be constrained or optimized as a function of the specific application. The ERC method is applicable to grid-connected and stand-alone hybrid systems with and without storage battery, for residential as well as for other uses. The reliability indicators defined are: the photovoltaic-wind fraction, energy fraction required by the load satisfied by the HPWBS; the utilization factor, energy fraction produced sent to the load; the manufacturability that characterizes the energy produced sent to the load in relation to the nominal power of the system. The ERC method was employed for the multi-objective optimization of a grid-connected hybrid system with and without storage battery for the electric energy supply to an urban residential building in a Mediterranean climate. A parametric analysis, for different loads, by varying the photovoltaic and wind power and the battery storage capacity, was developed to evaluate the annual energy reliability in a dimensionless form of 450 system configurations. The results allowed obtaining empiric correlations to be used in the system design. Finally, the ERC method application allowed achieving optimal system configurations with greater reliability compared with those provided by the Pareto-front method.