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Description: Energy | Version: 4.9.0 | Updated: 10.03.09 | |
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The annual energy production, AEP is calculated for all visible Turbine objects. If several climatology objects are available the AEP based on each climatology is calculated separately. Any discrepancies between the AEP's based on different climatologies are easily accessible.
A climatology is given by its frequency distribution and presented graphically in the wind rose. Additionally a climatology is given by its Weibull distribution. The AEP is calculated for both representations.
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| Properties | ||||
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| 1. Calculations | ||||
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| Air density | ||||
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| Specification of the air density at the Turbine positions. A power curve is given for a specific air density. If the air densities given in the power curves differ from the air density given herein, a correction will be applied to the power curves. Two different correction methods can be applied depending on the power control system of the WECS (EN 61400-12). If a power curve is defined without any corresponding density, the correction of the power curve will not be applied. The default value is 1 (kg/m3). | ||||
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| Method for density correction | ||||
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| Pitch-regulated WECS | ||||
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| In the case of pitch-regulated wind turbines the power output of the WECS is calculated by entering in the original power curve with a corrected wind speed. The corrected wind speed is obtained by the wind speed times the fraction (air density AEP)/(air density power curve) at the power 1/3. | ||||
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| Stall-regulated WECS | ||||
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| In the case of stall-regulated wind turbines the fraction (air density AEP)/(air density power curve) is used in the AEP calculations as a multiplication factor of the reference power curves. | ||||
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| Sector interpolation | ||||
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| See description page of Wind Resources | ||||
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| Wake effects | ||||
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| See description page of Wind Resources | ||||
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| 2. Export | ||||
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| Export vertical profiles | ||||
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| An ASCII file with vertical profiles at all visible Turbine positions is produced. The profiles are extracted from the wind database from ground level up to the "Height of reduced wind database" specified in the Wind Field module. A link to the file will be provided in the report. | ||||
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| Figure 1. | Definition sketch of vertical profiles, e.g. Speed_2D. Variable values are given in cell centres. | |||
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| The vertical profile file contains the following variables: | ||||
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| UCRT - wind speed scalar in East-West direction (m/s) | ||||
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| VCRT - wind speed scalar in North-South direction (m/s) | ||||
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| WCRT - wind speed scalar in vertical direction (m/s) | ||||
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| Speed_2D - wind speed scalar in horizontal plane, SQRT(UCRT2+VCRT2) (m/s) | ||||
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| Inflow - angle with respect to the horizontal, ATAN(WCRT/Speed_2D) (deg) | ||||
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| Shear - derivate of Speed_2D with respect to vertical direction, ΔSpeed_2D/ΔZ (1/s), where ΔSpeed_2D = Speed_2Dk+1 - Speed_2Dk-1, ΔZ = Zk+1 - Zk-1 | ||||
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| Shear_low - derivate of Speed_2D with respect to vertical direction, ΔSpeed_2D/ΔZ (1/s), where ΔSpeed_2D = Speed_2Dk - Speed_2Dk-1, ΔZ = Zk - Zk-1 | ||||
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| Shear_high - derivate of Speed_2D with respect to vertical direction, ΔSpeed_2D/ΔZ (1/s), where ΔSpeed_2D = Speed_2Dk+1 - Speed_2Dk, ΔZ = Zk+1 - Zk | ||||
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| KE - turbulent kinetic energy (m2/s2) | ||||
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| TI - turbulent intensity assuming isotropic KE, 100*SQRT((4/3)*KE)/SQRT(UCRT2+VCRT2) (%) | ||||
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| alpha - is the wind shear power exponent of a power law tangent to the calculated wind speed profile, Shear/(Speed_2D/za.g.l.) (-) | ||||
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| The default value is False (-). | ||||
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| Export rotor profiles | ||||
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| An ASCII file with rotor profiles at all visible Turbine positions is produced. Data is extracted from the wind database in the corners of a square centred at the hub. A link to the file will be provided in the report. | ||||
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| Figure 2. | Definition sketch of rotor profiles. | |||
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| The rotor profile file contains the same variables as the vertical profiles, see above. The variables are given at the HUB and in the corners of a square centred at the hub, the extension of each side is equal to the rotor diameter given in the module Objects. The following name syntax is used for corners; Upstream (U), Downstream (D), Right (R), Left (L), Top (T) and Bottom (B). The upstream plane of the cube is perpendicular to the incoming wind direction. The position in the vertical direction is referred to: above sea level (asl), above ground level (agl) and referred to HUB (rth). | ||||
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| The default value is False (-). | ||||
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| Export power history | ||||
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| The visible climatologies of type time history (.tws) are transferred to the hubs of each visible turbine; the relative .tws files are placed in the object folder of the project. ASCII files containing the electrical power output of each WECS for each record of the time history files are furthermore created and saved into the report folder. A link to the power history files will be provided in the report. | ||||
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| 3. IEC Classification | ||||
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| The two basic parameters for the classification of the wind generators, according to the standards IEC61400-1, are calculated at each hub position. First each .tws is transferred to each hub position, then the parameters Vref, Iref (mean value and standard deviation) are computed for the transferred .tws. The reference velocity, an extreme wind with a recurrence period of 50 years, is computed by Gumbel fitting the annual peaks of recorded wind speed (with the method of the maximum likelihood). At least two years of measurements are needed to perform a Gumbel fitting, with uncertainties reducing with longer time histories. The Iref, is given as mean turbulence intensity for 15 m/s bin, its standard deviation is also computed for the same samples. In the case of classification according to the second edition of the standards a characteristic turbulent intensity is required (84th percentile, mean plus the standard deviation). In the case of classification according to the third edition of the standards a representative turbulent intensity is required (90th percentile, mean plus 1.28 times the standard deviation). | ||||
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| 15 m/s bin width | ||||
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| Width of the velocity bin centered at 15 m/s used to compute mean and standard deviation of turbulent intensity. | ||||