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

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Numerical modelTabella 5.6: Settings for the numerical model.BOUNDARY CONDITIONSTopWall with no frictionGeostrophic height From linked model (500 m)Free stream wind speedFrom linked model (variable)Wind direction 0 - 90 – 180 – 270Turbulence modelstandard k-εSOLVER SETTINGSSolverCoupledNumber of iterations 500 – 800 – 400The high number of cells built up in the microscale model required some time toarrive to a good convergence level, which has been kept constant in all thesimulations. Anyhow, few critical runs have been found, mostly in the simulation for10 m/s: in the speed-up maps some areas in which divergence is growing up are wellevident; this tendency to diverge has been reduced by increasing the free streamvelocity, therefore the tests with 20 m/s are the ones that showed less problems ofconvergence. This fact let to think that in such a complex terrain and in such finegrid resolution the default value of the free stream velocity is not good enough.A presentation of this phenomenon can be seen in the figure 5.9, where in the leftzone of the picture is shown a critical area; the problems are mostly relevant whenwind is blowing from East sector, confirming the hypothesis by which the smallvariation in speed-up maps can be strictly connected to flow separation effects.83
Figure 5.9: Map of speed-ups for directional sector 90, Speed 10 m/s, Height 30 m.5.5 RemarksThe following pages shows the horizontal speed maps for the microscale model,extracted at 30 meters height above ground level for a wind speed of 5, 10 and 20m/s.As it can be easily seen, the velocity of the free stream seems to be not veryimportant in determining the speed-up maps. In fact, the pictures show goodagreement and the variations are very small. The variations are smaller in the centerof the maps, where the plateau is sited and the two mast measurements are placed.The value of 20 m/s for the free stream velocity seems to be the best value tested inorder to reduce this variations and convergence problems; so this, value has beenchosen to run the final simulations over the site.84
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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
Page 41 and 42: Figure 3.6: Sketch of the 15 km lon
Page 43 and 44: Figure 3.9: Influence of the height
Page 45 and 46: Figure 3.13: Zoom of the hill top r
Page 47 and 48: 3.5.2) = ∙.The two models for att
Page 49 and 50: 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: The orthogonalization of the grid h
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 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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