6. Constraints Map
6.1 IEC constraints
Press the IEC Constraints button to view/edit the constraint limits, and press the Extract button after selecting one or several of the following IEC Constraints, to generate the Constraints Map
The gray areas in the figure below are regions where the IEC Constraints are not satisfied, or are additional constraints. The white areas show valid turbine positions.
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6.2.1 IEC Shear
The shear calculation uses wind speed Input Files, at heights defined with the Hight Definition button. In addition, the Wind Resource file selected in the Energy Map tab will provide the frequency of each sector : f(s).
Let v1, v2 and v3 be the wind speed values corresponding to heights h1= ‘Simulation Hight’+’Shear Deviation’, h2=’Simulation Hight’ and h3=’Simulation Hight’-‘Shear Deviation’ respectively. Further, let s be each of the sectors listed in the Use Sectors box of Constraints Map tab. Then the shear coefficient for sector s ,a(s), at each point is the (Least Squares) solution of the equations
(v1(s)/v2(s)) = (h1/h2)^a(s) (^ denotes exponentiation)
(v3(s)/v2(s)) = (h3/h2)^a(s) .
The shear coefficient a is then the sum over the Use Sectors sectors of a(s)*f(s).
Note that if the Wind Resource file is not defined, the shear coefficient will be set to the maximum over the sectors of a(s).
6.2.2 IEC Turbulence
Turbulence is calculated from the turbulence intensity files of Input Files at the Simulation Hight, scaled according to a tws measurement file (if defined, in which case a turbulence intensity at the measurement height is also required). The Wind Resource file selected in the Energy Map tab provides frequency distribution of the sectors.
Select the tws measurement file by pressing turbulence Setup followed by Select :
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The turbulence at each point ( assuming a measurement file is used ) is calculated as follows. For each sector s, let ti(s) be the turbulence intensity at the Simulation Hight, ti_meas(s) the turbulence intensity from the measurement file (at the measurement height), ti_ws(s) the WindSim turbulence intensity at the same coordinate and height as ti_meas, and f(s) the sector frequency from the Wind Resource file, then the turbulence t is the sum over sectors s in Use Sectors of
The turbulence at each point is set to the maximum over s in Use Sectors of t(s) if the Wind Resource file is not defined.
6.2.3 IEC Extreme wind
The Extreme Wind calculation is based on extreem speed values estimated externally. These values are scaled according to wind speeds of WindSim Input Files at the Simulation Hight and the average windspeeds of a tws measurement file.
Select the measurement file and enter the corresponding extreem speed values via the Setup button :
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The Extreem Speed at each point x,y, is the maximum over sectors s in Use Sectors of
es_xy(s) = es_meas(s) * ( v_xy(s) / v_meas(s) ) , where
es_meas(s) : extreem speed entered in gui above.
v_meas(s) : average speed from tws file.
v_xy(s): WindSim wind speed.
6.2 Additional Constraints
Constraints can be added to the Constraints Map by importing a shape file (.shp) or by defining constraints with a drawing editor, by pressing New. When a constraint is added with New, it will automatically be saved to the Results Directory, and can later be read with the Open pgn button.
The shape file can define several polygons : The shape file must contain the field ‘Shape’, consisting of an array of fields ‘x’ and ‘y’, where each ‘Shape(k).x’ and ‘Shape(k).y’ is an array of coordinates – terminated with NaN – that define a polygonal constraint.