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

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it is possible to forecast a climatology in a new position B inside the map. It meansthat is possible to “transfer” experimental data from the original position (A) toanother one (B).The procedure that allows to build a “transferred climatology”, making use of theCFD simulations, is explained in the following lines.1) CFD simulations are carried out using boundary conditions somehowdifferent from the actual ones, in order to obtain a better convergence of thesimulations as will be explained in chapter 5.2) As a result of the CFD calculation the speed-up map is found, in a zone wherethe experimental climatology can be placed. The speed-up is defined as theratio between the wind velocity in one point of the map and the windvelocity in a particular reference point.3) This map can be modified (with a linear scaling operation) in the way to havethe speed-up value equal to 1 in the location where the climatology isknown. A new speed-up map is generated.4) Finally, the scalar value of the experimental velocity in the climatologyposition must be multiplied per every value of the CFD speed-up map, inorder to generate a new velocity map, that simulates the “real” velocity inthe numerical domain.5) This procedure is repeated for each sector of the wind rose (12 in the specificcase) and for each velocity bin defined in the frequency table of theclimatology.The use of the “transferred climatologies” is needed when doing a “cross checking”of experimental data, for example when inside the map more than one climatologyis present. In this way, it is possible to use experimental data of one station andforecast CFD wind data in an other position. Then, it is possible a comparisonbetween the data forecasted by simulations and the experimental data, in a secondstation.11
1.5.4 RESULTSThe Results module allows the user to extract the informations related to thethermo-fluid dynamic variables calculated by the Windfield module.All extracted variables are not weighted with climatology, but refer directly to thePhoenics database, containing the results of the pure CFD calculation.1.5.5 WIND RESOURCESTrough this module is possible to calculate the horizontal wind speed maps all overthe site, by weighting the CFD results with the experimental climatology. Theprocedure to arrive to the wind resources maps is basically the same of thetransferred climatology calculation.By this module, the calculation of the wind turbine losses is possible, using 3different models.1.5.6 ENERGYThis module is the last one and calculates the Annual Energy Production (AEP) of thewindfarm, with the possibility to include the losses calculation.1.6 κ−ε turbulence modelTo close the system of equations introduced by the Navier-Stokes equations aturbulence model is needed. In all the simulations the standard k-e model is used,which needs two new equations to add to the system of numerical equations andintroduces two new unknown variables. One is the Turbulent Kinetic Energy (TKE),while the second is the Dissipation Rate (ε).12
Page 1 and 2: UNIVERSITÀ DEGLI STUDI DI CAGLIARI
Page 3 and 4: IndexIndex page IAcknowledgmentsVII
Page 5 and 6: CHAPTER 4: Characteristics of the s
Page 7 and 8: 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
Page 15 and 16: Figure 1.1: Example of an atmospher
Page 17 and 18: 1.5 The WindSim numerical codeWindS
Page 19: (κ−ε RNG or the Low Reynolds),
Page 23 and 24: Figure 1.2: Example of TKE vertical
Page 25 and 26: CHAPTER 2. Simulations over flat te
Page 27 and 28: inlet position (0 meters), station
Page 29 and 30: 2.4 Height distribution factor sens
Page 31 and 32: e decreased, to avoid to build thin
Page 33 and 34: 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
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
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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
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CHAPTER 5. Test of the Free Stream
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case the wind is blowing from the e
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Geometrical modelTable 5.3: Input p
Page 89 and 90:
Figure 5.6: Vertical profiles in po
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The orthogonalization of the grid h
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Figure 5.9: Map of speed-ups for di
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Figure 5.30: Speed-2D at 30 m heigh
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Figure 5.12: Speed-2D at 30 m heigh
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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
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characterized by high wind speed (5
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From the error analysis, it is foun
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Anyhow, the trend of the linear int
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Concerning the CFD simulations, val
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Analyzing RMS error table for tower
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A general overview of the figure 6.
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6.7 Cross Checking of wind dataIn t
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Figure 6.8 a/bFigure 6.8 c/dFigure
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Table 6.11: RMS error for cross che
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Figure 6.9 e/fFigure 6.9 g/hFigure
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Figure 6.10 g/hFigure 6.10 i/lFigur
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to have a better agreement during t
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Figure 7.2: Weibull fitting of the
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Figure 7.5: Perspective view of the
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The calculated AEP has been reporte
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ConclusionsIn this thesis the evalu
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Bibliography[1] CRASTO G. - Numeric
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