wind energy resource evaluation in a site of central italy ... - WindSim

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7.5 RemarksThe AEP of a wind farm constituted by 16 turbines has been calculated. The positionof the turbines was chosen considering the main wind direction sectors and thewind resource map, obtained by weighting the CFD results against the climatology5428 (plateau) at 50 meters height in the period Apr-May.The total energy production of the park was 46,2 GWh per year, corresponding to1443 hours of work at nominal power output.For further analysis it could be interesting to have a complete one year wind dataset and to have wind data filtered with cases of atmospheric stability, in order toavoid strong thermal effects which WindSim was not able to reproduce.125
ConclusionsIn this thesis the evaluation of wind energy resources over a site in central Italy wasconducted by means of the CFD code WindSim.A series of 2D simulations were performed in order to validate the code. The codevalidation process brought to find the correct discretization parameter capable toguarantee grid-independent results. The “wall with no friction” boundary condition,to be applied at the top of the geometrical model was chosen, in order to describe aneutral stratified ABL. The comparison of the CFD results with numerical andexperimental results found in literature showed a fair agreement.The second part of the study concerned the evaluation of the wind resources o a sitein Central Italy. The experimental wind data of two measurement masts (withmultiple measurement stations) were reduced and statistically analyzed.Taking advantage of the validation phase results, 3D simulations were carried out fora geometrical model reproducing the complex orography of the site. Firstly, acorrect value of the free stream velocity of the geostrophic wind was found, to avoidconvergence problems. A “nesting technique” in a coarse grid model was used toreduce the computational resources.Finally the simulations over a 14x14 km extended model with fine grid resolutionhave been performed and the wind field over the whole site was calculated.The results of the CFD calculations have been processed, in order to establish acomparison between experimental data and calculated values. The Vertical profilesof velocity and of turbulence intensity allowed the evaluation of RMS errors againstthe experimental data. RMS errors of velocity profiles exhibit a direct relation withthe mean velocity of the directional sector, hereby showing a strong dependence onthermal effects. Indeed, these effects are not taken into account by the CFDsimulations, whose numerical model is addressed to reproduce a neutral ABL. Theanalysis of results on the wind rose sectors allowed to find a range of mean velocity(3÷4 m/s) that discriminate whether or not data are influenced by thermal effects.For high mean velocity a fair agreement was evident.126
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UNIVERSITÀ DEGLI STUDI DI CAGLIARI
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IndexIndex page IAcknowledgmentsVII
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CHAPTER 4: Characteristics of the s
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6.7.1 Mean wind velocity page 1096.
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This thesis is the result of a prac
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WindSim is a software developed by
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CHAPTER 1. Atmospheric Boundary Lay
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Figure 1.1: Example of an atmospher
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1.5 The WindSim numerical codeWindS
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(κ−ε RNG or the Low Reynolds),
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1.5.4 RESULTSThe Results module all
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Figure 1.2: Example of TKE vertical
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CHAPTER 2. Simulations over flat te
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inlet position (0 meters), station
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2.4 Height distribution factor sens
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e decreased, to avoid to build thin
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Figure 2.10: Vertical profiles for
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CHAPTER 3. Simulations over 2D hill
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Table 3.1: Measurement coordinatesS
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The results shown above demonstrate
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Figure 3.6: Sketch of the 15 km lon
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Figure 3.9: Influence of the height
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Figure 3.13: Zoom of the hill top r
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3.5.2) = ∙.The two models for att
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H [m] hill heightν[m 2 /s] air cin
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Figure 3.18: Particular of the nume
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Finally, the horizontal x velocity
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Figure 3.25: Z velocity componentFi
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3.6 RemarksA CFD study of a boundar
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Some experimental wind data of this
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Both the pictures 4.3 and 4.4 have
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Table 4.2: Description of the color
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In this periods, data are recorded
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In the following pages, a short des
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4.3.2 Mast 5424-15 m Period April-M
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4.3.4 Mast 5424-15 m Period Novembe
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4.3.6 Mast 5428-40 m Period April-M
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4.3.8 Mast 5428-50 m Period Novembe
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4.3.10 Mast 5428-30 m Period Novemb
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4.4.2 Mast 542870
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4.5.2 Mast 542872
Page 83 and 84: CHAPTER 5. Test of the Free Stream
Page 85 and 86: case the wind is blowing from the e
Page 87 and 88: Geometrical modelTable 5.3: Input p
Page 89 and 90: Figure 5.6: Vertical profiles in po
Page 91 and 92: The orthogonalization of the grid h
Page 93 and 94: Figure 5.9: Map of speed-ups for di
Page 95 and 96: Figure 5.30: Speed-2D at 30 m heigh
Page 97 and 98: Figure 5.12: Speed-2D at 30 m heigh
Page 99 and 100: CHAPTER 6. Analysis of the wind fie
Page 101 and 102: Table 6.2: Boundary conditions and
Page 103 and 104: 6.5 Vertical profiles of VelocityTo
Page 105 and 106: characterized by high wind speed (5
Page 107 and 108: From the error analysis, it is foun
Page 109 and 110: Anyhow, the trend of the linear int
Page 111 and 112: Concerning the CFD simulations, val
Page 113 and 114: Analyzing RMS error table for tower
Page 115 and 116: A general overview of the figure 6.
Page 117 and 118: 6.7 Cross Checking of wind dataIn t
Page 119 and 120: Figure 6.8 a/bFigure 6.8 c/dFigure
Page 121 and 122: Table 6.11: RMS error for cross che
Page 123 and 124: Figure 6.9 e/fFigure 6.9 g/hFigure
Page 125 and 126: Figure 6.10 g/hFigure 6.10 i/lFigur
Page 127 and 128: to have a better agreement during t
Page 129 and 130: Figure 7.2: Weibull fitting of the
Page 131 and 132: Figure 7.5: Perspective view of the
Page 133: The calculated AEP has been reporte
Page 137 and 138: Bibliography[1] CRASTO G. - Numeric
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