Total cost of ownership of electric vehicles using energy from a renewable-based microgrid

This work aims at analyzing the integration between electric mobility and renewable energy sources studying the case of the grid-connected microgrid under construction at the University of Trieste, Italy. A general model able to estimate the charging price and the resulting total cost of ownership per kilometer considering the match between the demand and the production of a photovoltaic generator is presented. The result is that the electric vehicle is mainly charged with the produced renewable energy (72%) and that the 60% of it flows through the storage unit. The study also presents a sensitivity analysis to show how the battery size and cost, together with the travelled distance, influence the charging price and the total cost of ownership per kilometer. Considering the current Italian prices and subsidies, results show that the use of an electric car is today feasibl

A hardware field simulator for photovoltaic materials applications.

2006/2007Il presente lavoro riguarda la descrizione di un simulatore di campo fotovoltaico (in seguito simulatore). Il simulatore è un convertitore elettronico di potenza che, alimentato dalla rete elettrica, riproduce la caratteristica tensione corrente di un campo fotovoltaico (insieme di moduli fotovoltaici connessi in serie e in parallelo) operante in condizioni climatiche di temperatura e irraggiamento arbitrarie. Il nuovo dispositivo verrà impiegato nell’ambito del laboratorio fotovoltaico cui fa riferimento l’impianto in via di realizzazione sul tetto dell’edificio che ospita il Dipartimento dei Materiali e delle Risorse Naturali dell’Università di Trieste. Il simulatore viene proposto come utile strumento per i progettisti di dispositivi solari funzionanti in sistemi fotovoltaici connessi in rete. In particolare, il simulatore permetterà di prevedere il funzionamento di nuovi moduli fotovoltaici operanti in condizioni di ombreggiamento arbitrario e inseriti in un sistema fotovoltaico reale. L’uso del simulatore sarà particolarmente efficace nel caso di simulazioni di tecnologie in film sottile come, ad esempio, il silicio amorfo, il tellururo di cadmio, ecc. Il simulatore sarà anche necessario per testare i componenti che fanno parte di un sistema fotovoltaico connesso in rete, con particolare riferimento ai sistemi di condizionamento della potenza (detti anche inverter). Tali sistemi, oltre a convertire la tensione continua prodotta dai moduli fotovoltaici in una tensione compatibile e sincronizzata con quella della rete, devono garantire istante per istante l’inseguimento del punto di massima potenza estraibile dal campo fotovoltaico cui sono connessi. Il lavoro è stato suddiviso in cinque capitoli. Il primo capitolo fornisce una breve descrizione dello stato dell’arte e di alcune aspetti economici relativi alla tecnologia fotovoltaica. Nel secondo capitolo vengono richiamati il modello classico di una cella solare e le definizioni riguardo le sue caratteristiche principali (punto di massima potenza, efficienza, fill factor, ecc.). Nello stesso capitolo un’overview sui materiali e sulle tecnologie utilizzate nella realizzazione dei dispositivi fotovoltaici divide, come suggerito da Martin Green, le celle solari in tre diverse generazioni: la prima comprende i dispositivi realizzati in silicio cristallino (mono e policrisallino), la seconda quelli in film sottile (in silicio amorfo, tellururo di cadmio CdTe, diseleniuro di rame e indio CIS, diseleniuro di rame, indio e gallio CIGS, diseleniuro di rame, indio, gallio e zolfo CIGSS) e le celle di Graetzel, e la terza le celle multigiunzione, a banda intermedia e quelle organiche. Nel capitolo tre viene fornita una descrizione dei componenti costituenti un sistema fotovoltaico connesso in rete e viene proposto un nuovo metodo per la determinazione delle caratteristiche corrente tensione e potenza tensione prodotte da dispositivi fotovoltaici. Il metodo risulta efficace in quanto non necessita di misure sperimentali da effetture sui diversi dispositivi. I dati forniti nei comuni data sheet che vengono forniti a corredo dei moduli fotovoltaici sono sufficienti a determinarne il comportamento al variare della temperatura di funzionamento e del livello di radiazione solare. L’efficienza di un sistema fotovoltaico (Balance Of the System, BOS) viene calcolata nel capitolo quattro. Particolare enfasi viene data all’effetto di mismatching che è tanto più importante quanto più è elevato il livello di ombreggiamento presente sul piano dei moduli fotovoltaici costituenti l’impianto. Infine, l’ultimo capitolo riguarda la descrizione del simulatore e delle sue applicazioni.The subject of this work is a power electronic device, hereafter named photovoltaic field simulator, which converts the grid voltage into a current voltage characteristic. This characteristic replicates the behavior of a real photovoltaic field working in arbitrary conditions of irradiance and temperature. After building, the photovoltaic field simulator will be used in the photovoltaic laboratory which is connected to the experimental photovoltaic plant which will be installed on the roof top of the Materials and Natural Resources Department of Trieste University. The photovoltaic field simulator will be used for photovoltaic module parameters design with particular reference to its behavior when inserted in a photovoltaic field operating under shaded conditions. The use of the simulator will be particularly effective when simulating thin-film technologies as, for example, amorphous silicon, cadmium telluride, and etc. The photovoltaic field simulator will also be used for testing the components of grid connected photovoltaic systems with particular reference to the power conditioning units (also named inverters). These systems, which convert the direct current produced by the photovoltaic modules into a utility grade current (typically alternate and sinusoidal at a frequency of 50-60Hz), must extract maximum power from the photovoltaic field. The work is divided into five chapters. In the first a brief description of photovoltaic technology and its economic aspects is given. Chapter two is on classic solar cell modelling basics and on the definition of the parameters of photovoltaic technology (maximum power point, efficiency, fill factor, and etc.). In the same chapter a materials and technologies overview splits, as suggested by Martin Green, solar cells in three different generations: the first comprises crystalline silicon (mono and polycrystalline) devices, the second thin-film devices (amorphous silicon, cadmium telluride CdTe, copper indium diselenide CIS, copper indium gallium diselenide CIGS, copper indium gallium sulphur diselenide CIGSS), and the Graetzel cells, while the third multi-junction, intermediate band and organic photovoltaic devices. The third chapter briefly describes photovoltaic grid connected system components. In particular a new model for plotting photovoltaic current voltage and power voltage characteristics is provided. The method is original because only module data sheet parameters are used and experimental measurements are not needed in order to determine the photovoltaic modules behavior with reference to irradiance and working temperatures changes. In chapter four the Balance of a photovoltaic System (BOS) is calculated. In particular the importance of the mismatching effect of photovoltaic modules due to shaded conditions is shown. The last chapter is on simulator description and its applications.XX Ciclo197

Adaptive Neural Network-Based Control of a Hybrid AC/DC Microgrid

In this paper, the behavior of a grid-connected hybrid ac/dc microgrid has been investigated. Different renewable energy sources - photovoltaics modules and a wind turbine generator - have been considered together with a solid oxide fuel cell and a battery energy storage system. The main contribution of this paper is the design and the validation of an innovative online-trained artificial neural network-based control system for a hybrid microgrid. Adaptive neural networks are used to track the maximum power point of renewable energy generators and to control the power exchanged between the front-end converter and the electrical grid. Moreover, a fuzzy logic-based power management system is proposed in order to minimize the energy purchased from the electrical grid. The operation of the hybrid microgrid has been tested in the MATLAB/Simulink environment under different operating conditions. The obtained results demonstrate the effectiveness, the high robustness and the self-adaptation ability of the proposed control system

Optimal Sizing and Environ-Economic Analysis of PV-BESS Systems for Jointly Acting Renewable Self-Consumers

Future residential applications could benefit from nanogrids that integrate photovoltaics (PV) and battery energy storage systems (BESS), especially after the establishment of recent European Community directives on renewable energy communities (RECs) and jointly acting renewable self-consumers (JARSCs). These entities consist of aggregations of users who share locally produced energy with the aim of gaining economic, environmental, and social benefits by enhancing their independence from the electricity grid. In this regard, the sizing of the PV and BESS systems is an important aspect that results in a trade-off from technical, economic, and environmental perspectives. To this end, this paper presents an investigation on the optimal PV-BESS system sizing of a condominium acting as a JARSC community, which includes a common PV plant and EMS, operated by rule-based criteria. PV-BESS sizing results are investigated from economic and environmental perspectives, considering a case study located in Milan, Italy. In these regards, in addition to the common techno-economic criteria, carbon dioxide emissions are considered with particular attention, as their reduction is the driving ethos behind recent EU directives

The effect of manufacturing mismatch on energy production for large-scale photovoltaic plants

In the literature, the effect of the mismatch due to manufacturing tolerances on PV plant productivity has been investigated under the hypothesis of plant operation in Standard Test Conditions (STC). In this paper, mismatch impacts are evaluated in more realistic terms taking into account various possible operating conditions. Results are illustrated through the study case of a 1 MWp solar park for which module datasheets as well as flash test data are available. The plant production is evaluated assuming operating conditions that comply with the European efficiency standards. It is shown how the effect of a given mismatch on the annual productivity estimation can significantly change depending on the operating conditions

Advanced Methods for Photovoltaic Output Power Forecasting: A Review

Forecasting is a crucial task for successfully integrating photovoltaic (PV) output power into the grid. The design of accurate photovoltaic output forecasters remains a challenging issue, particularly for multistep-ahead prediction. Accurate PV output power forecasting is critical in a number of applications, such as micro-grids (MGs), energy optimization and management, PV integrated in smart buildings, and electrical vehicle chartering. Over the last decade, a vast literature has been produced on this topic, investigating numerical and probabilistic methods, physical models, and artificial intelligence (AI) techniques. This paper aims at providing a complete and critical review on the recent applications of AI techniques; we will focus particularly on machine learning (ML), deep learning (DL), and hybrid methods, as these branches of AI are becoming increasingly attractive. Special attention will be paid to the recent development of the application of DL, as well as to the future trends in this topic

Sustainability Analysis of Hydrogen Production Processes: a Comparison Based on Sustainability Indicators

Hydrogen is a versatile energy carrier and storage medium that may be employed in a variety of applications. It may be produced using different processes. In this work, process simulation is used to obtain material and energy balances for each process investigated, as well as for the evaluation of capital and maintenance costs. Process simulation outcomes are then used to estimate three key performance indicators focusing on sustainability issues: the energy return of energy invested, the levelized cost of hydrogen and the life cycle assessment. We compared several hydrogen generation processes, each denoted by a unique colour code: (i) green hydrogen, produced by electrolysis of water using electricity from renewable sources, (ii) grid hydrogen, produced by electrolysis using grid electricity, (iii) grey hydrogen, produced from natural gas using steam reforming and (iv) blue hydrogen, like grey one, but coupled with carbon capture and storage. In conclusion, the most sustainable hydrogen production method is the green hydrogen, produced by water electrolysis

A novel fault diagnosis technique for photovoltaic systems based on artificial neural networks

This work proposes a novel fault diagnostic technique for photovoltaic systems based on Artificial Neural Networks (ANN). For a given set of working conditions - solar irradiance and photovoltaic (PV) module's temperature - a number of attributes such as current, voltage, and number of peaks in the current-voltage (I-V) characteristics of the PV strings are calculated using a simulation model. The simulated attributes are then compared with the ones obtained from the field measurements, leading to the identification of possible faulty operating conditions. Two different algorithms are then developed in order to isolate and identify eight different types of faults. The method has been validated using an experimental database of climatic and electrical parameters from a PV string installed at the Renewable Energy Laboratory (REL) of the University of Jijel (Algeria). The obtained results show that the proposed technique can accurately detect and classify the different faults occurring in a PV array. This work also shows the implementation of the developed method into a Field Programmable Gate Array (FPGA) using a Xilinx System Generator (XSG) and an Integrated Software Environment (ISE)

Energy Scheduling and Performance Evaluation of an e-Vehicle Charging Station

This paper proposes an energy management system (EMS) for a photovoltaic (PV) grid-connected charging station with a battery energy storage system (BESS). The main objective of this EMS is to manage the energy delivered to the electric vehicle (EV), considering the price and (Formula presented.) emissions due to the grid’s connection. Thus, we present a multi-objective two-stage optimization to reduce the impact of the charging station on the environment, as well as the costs. The first stage of the optimization provides an energy schedule, taking into account the PV forecast, the hourly grid’s (Formula presented.) emissions factor, the electricity price, and the initial state of charge of the BESS. The output from this first stage corresponds to the maximum power permitted to be delivered to the EV by the grid. Then, the second stage of the optimization is based on model predictive control that looks to manage the energy flow from the grid, the PV, and the BESS. The proposed EMS is validated using an actual PV/BESS charging station located at the University of Trieste, Italy. Then, this paper presents an analysis of the performance of the charging station under the new EMS considering three main aspects, economic, environmental, and energy, for one month of data. The results show that due to the proposed optimization, the new energy profile guarantees a reduction of 32% in emissions and 29% in energy costs