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

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value at 30 meters. It can be seen that every vertical profile passes trough the pointwith coordinates (1, 30) of the graphs.Values of U30 are reported in table 6.3, while in table 6.4 the RMS errors, calculatedto evaluate the disagreement of the CFD results respect to the experimental winddata, are shown. In each table highest and lowest values are highlighted.Table 6.3: U30 values in [m/s].Table 6.4: RMS Errors between experimental and numerical dataThe table of RMS errors has been calculated by the formulas6.1) = ( + + ⋯ + ) and6.2) = ( − )If the error results of the tower 5424 (CLIFF) are analyzed, worst and best sectors arededuced. The worst sector is 180°, showing highest errors in both periods April-Mayand November-December. The best sectors are, instead, 240° during the periodApril-May and 60°, during the period November-December.It must be noticed the trend similarity between the errors and the values of thewind velocity at 30 meters height. In fact, the best sectors (240° and 60°) are95
characterized by high wind speed (5,93 and 6,01 m/s), while the worst sectors arecharacterized by low speed (1,73 and 2,61 m/s).A physical explanation of this phenomenon could be related to the seasonal thermaleffects. It is wise to think that modification of the neutral boundary layer by thermaleffects is high when the wind speed is low and vice versa. According to this, sectorscharacterized by high wind speed should be considered almost free of thermaleffects. Then, considering that the simulations do not take into account theinfluence of thermal effects, the CFD results should have a better agreement withmeasurements in sectors where wind speed is high.A threshold value related to the importance of thermal effects on the wind fieldwind velocity is difficult to be deduced from the results, but a range in which it isexpected is 3-4 m/s. Data Analysis confirms that RMS errors are low when the windis blowing with a velocity higher than a value contained in the range, resulting in afair agreement between experimental data and result of the CFD model.96
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UNIVERSITÀ DEGLI STUDI DI CAGLIARI
Page 3 and 4:
IndexIndex page IAcknowledgmentsVII
Page 5 and 6:
CHAPTER 4: Characteristics of the s
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6.7.1 Mean wind velocity page 1096.
Page 9 and 10:
This thesis is the result of a prac
Page 11 and 12:
WindSim is a software developed by
Page 13 and 14:
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),
Page 21 and 22:
1.5.4 RESULTSThe Results module all
Page 23 and 24:
Figure 1.2: Example of TKE vertical
Page 25 and 26:
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
Page 35 and 36:
CHAPTER 3. Simulations over 2D hill
Page 37 and 38:
Table 3.1: Measurement coordinatesS
Page 39 and 40:
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
Page 51 and 52:
Figure 3.18: Particular of the nume
Page 53 and 54: Finally, the horizontal x velocity
Page 55 and 56: Figure 3.25: Z velocity componentFi
Page 57 and 58: 3.6 RemarksA CFD study of a boundar
Page 59 and 60: Some experimental wind data of this
Page 61 and 62: Both the pictures 4.3 and 4.4 have
Page 63 and 64: Table 4.2: Description of the color
Page 65 and 66: In this periods, data are recorded
Page 67 and 68: In the following pages, a short des
Page 69 and 70: 4.3.2 Mast 5424-15 m Period April-M
Page 71 and 72: 4.3.4 Mast 5424-15 m Period Novembe
Page 73 and 74: 4.3.6 Mast 5428-40 m Period April-M
Page 75 and 76: 4.3.8 Mast 5428-50 m Period Novembe
Page 77 and 78: 4.3.10 Mast 5428-30 m Period Novemb
Page 79 and 80: 4.4.2 Mast 542870
Page 81 and 82: 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: 6.5 Vertical profiles of VelocityTo
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 and 134: The calculated AEP has been reporte
Page 135 and 136: ConclusionsIn this thesis the evalu
Page 137 and 138: Bibliography[1] CRASTO G. - Numeric
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