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Metodo Innovativo Per La Valutazione Delle Prestazioni Di Una Turbina

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Metodo Innovativo Per La Valutazione Delle Prestazioni Di Una Turbina Mauro Menegazzo, 1020312 Tesi Magistrale, Aprile 2014 Metodo Innovativo per la Valutazione delle Prestazioni di una Turbina Eolica Darrieus ad Asse Verticale utilizzando Simulazioni Bidimensionali di Fluidodinamica Computazionale (CFD) Relatore: Prof. Ernesto Benini, Ph.D. Dipartimento di Ingegneria Industriale Facoltà di Ingegneria Aerospaziale Indice Prima parte: Energia eolica 1.1 Introduzione .............................................................................................................................. 5 1.2 Storia ........................................................................................................................................ 6 1.2.1 I primi sfruttamenti per generare potenza elettrica ............................................................... 7 1.3 L'energia eolica ......................................................................................................................... 8 1.3.1 Distribuzione della velocità del vento.................................................................................. 9 1.3.2 Venti d’alta quota ............................................................................................................... 9 1.4 Parchi eolici ............................................................................................................................ 10 1.4.1 Eolico on-shore e near-shore ............................................................................................. 11 1.4.2 Eolico off-shore ................................................................................................................ 12 1.4.3 Minieolico e microeolico .................................................................................................. 13 1.4.4 Eolico d'alta quota............................................................................................................. 13 1.5 Turbina eolica ......................................................................................................................... 14 1.5.1 Generatore ad asse orizzontale .......................................................................................... 15 1.5.2 Principali componenti ....................................................................................................... 16 1.5.2.1 Rotore ........................................................................................................................ 16 1.5.2.2 Navicella o gondola .................................................................................................... 16 1.5.2.3 Torre .......................................................................................................................... 17 1.6 Generatore ad asse verticale .................................................................................................... 18 1.7 Eolico magnetico ..................................................................................................................... 18 1.8 Capacità di energia eolica e produzione ................................................................................... 18 1.8.1 Trend di crescita ............................................................................................................... 20 1.8.2 Fattore di capacità ............................................................................................................. 21 1.8.3 Penetrazione ..................................................................................................................... 22 1.8.4 Variabilità ......................................................................................................................... 24 1.8.5 Prevedibilità...................................................................................................................... 25 1.8.6 Affidabilità ....................................................................................................................... 25 1.8.7 Accumulo dell'energia ...................................................................................................... 25 1.8.8 Effetti sull'ambiente .......................................................................................................... 26 1.8.9 Efficienza ......................................................................................................................... 27 1.9 Economia ................................................................................................................................ 27 1 1.9.1 Trend dei costi .................................................................................................................. 28 1.9.2 Incentivi e benefici di comunità ........................................................................................ 29 1.10 Politica .................................................................................................................................. 29 1.10.1 Governi centrali .............................................................................................................. 29 1.10.2 Opinione pubblica ........................................................................................................... 30 1.10.3 Comunità ........................................................................................................................ 31 1.11 Costi mini-eolico ................................................................................................................... 31 1.12 Costi micro-eolico ................................................................................................................. 32 Seconda parte: Turbine eoliche 2.1 Introduzione ............................................................................................................................ 37 2.2 Turbine ad asse orizzontale ..................................................................................................... 38 2.2.1 Legge di Betz .................................................................................................................... 38 2.2.2 Coefficiente di potenza Cp ................................................................................................ 42 2.2.3 Momento torcente medio .................................................................................................. 43 2.3 Turbine ad asse verticale ......................................................................................................... 44 2.3.1 Turbine a resistenza .......................................................................................................... 44 2.3.2 Turbine a portanza ............................................................................................................ 45 2.3.3 Turbina Darrieus ............................................................................................................... 46 2.3.4 Turbina Savonius .............................................................................................................. 47 2.3.5 Turbina Gorlov ................................................................................................................. 48 2.4 Comparazione tra HAWT e VAWT......................................................................................... 48 2.4.1 Meccanismo di Yaw ......................................................................................................... 48 2.4.2 Direzione dell’asse ............................................................................................................ 49 2.4.3 Azionamento diretto ......................................................................................................... 49 2.5 Costruzione ............................................................................................................................. 49 2.6 Meccanica strutturale .............................................................................................................. 50 2.7 Aerogeneratori di piccola potenza ........................................................................................... 50 2.8 Turbine ad asse verticale in ambiente urbano ........................................................................... 51 2.9 Turbina analizzata in questo lavoro ......................................................................................... 51 2.10 Principio di funzionanento di una VAWT .............................................................................. 52 2 Terza parte: Fondamenti di fluidodinamica computazionale 3.1 Introduzione ............................................................................................................................ 57 3.2 La fluidodinamica computazionale .......................................................................................... 57 3.3 Metodi di discretizzazione ....................................................................................................... 58 3.3.1 Procedura di analisi ........................................................................................................... 58 3.4 La strategia della CFD ............................................................................................................. 59 3.5 Metodo delle differenze finite .................................................................................................. 60 3.6 Discretizzazione attraverso il metodo dei volumi finiti ............................................................ 61 3.6.1 Assemblaggio del sistema discreto e applicazione delle
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