Description: Objects Version: 8.0.0 Updated: 20.08.14

Objects

Placing the objects

The Objects module is used to position turbines, climatologies and transferred climatologies. For visualisation purposes various geometrical objects can also be placed within the 3D terrain model.

Alternatively objects can be read from a .ows files using the Tools->Import objects menu item, see example of the .ows format.

Climatology conversion

If the climatology data is not given on the WindSim format .wws, a conversion is necessary before the data can be used within WindSim.

Conversion from other formats is performed by clicking the Tools->Convert climatology data menu item. The Convert climatology data is subject to continuous development, so please contact WindSim AS if you need extensions in order to perform the conversion of your specific data, see examples of supported climatology formats: third party formats. Alternatively, you can convert your climatology data directly to the .wws format by using your own tools, see: climatology data.

Properties
1. Object definition
Object type
Setting the object type as Turbine, Climatology, Geometrical or TransferredClimatology. Default value is Turbine (-).
Name
Name of the object.
Visible
Setting the object as visible or invisible for visualisation purposes. Setting visible, False for a Turbine object will cause it to be disregarded in the energy calculation. Setting visible , False for a Climatology object will cause it to be disregarded in the wind resource and energy calculation.
Visualisation file
Specification of a file with geometry used for visualisation. For Turbine objects it is recommended to use turbin_nn (nn is a height), which automatically generates simple scaleable geometries in accordance with the legend in the report section. Likewise for climatology and climatology transfer objects it is recommended to use climatology_nn (nn is a height). Default value depends on Object type (-).
Climatology file
Specification of a climatology file. Climatologies can be converted from other formats by clicking the Tools->Convert climatology data menu item.
If the object type is TransferredClimatology then the specification of an existing climatology file used within the project will be transferred to a new position. Any x and y coordinates within the model is allowed, but there is a restriction on the z values. The z values must be above the first computational node, which varies according to the resolution in the given mode. A warning is given if a value below the allowed minimum is given. The height of the reduced wind database, specified under the Wind Fields module defines the maximum z value. The transferred climatology will be placed in the climatology folder with the prefix trans_ added to the original file name.
Transfer climatology is useful for cross checking and for successive transfer of climatologies over larger distances. By transferring a climatology to higher altitudes in a refined model, small scale effects are filtered out. Now the transferred climatology can be used in a coarser model for transfer over larger distances. Finally the climatology can be imported again in new refined models.
Note that transferred climatology objects within a model are not used in the Wind Resources and Energy modules, as they don't provide any new information. A climatology transferred from an external model will provide new information, these climatologies can be included as ordinary climatology objects. Default value is none (-).
Power curve file
Specification of a power curve file in WindSim format .pws. If a turbine type is not available in the WindSim database (C:\Program Files\WindSim\WindSim 8.0.0\Data\Objects\Power Curve) you can write it with Tools->Create power curve (.pws) or in a text editor taking into account the required syntax. Default value is none (-).
Hub height
Turbine hub height. Default value is 80 (meters).
Rotor diameter
Turbine rotor diameter. Default value is 60 (meters).
Rotation speed
The rotational speed of the turbine blades or the climatology anemometer. Default value is 10 (rounds per minute) for turbines and 25 (rounds per minute) for climatologies.
Facing wind direction
The direction towards which a turbine is turned. The angle is in degrees measured clockwise from North. The default value is 180 (degrees), meaning that the turbine is oriented towards South.
2. Position
Coordinate system
Positioning of objects is by reference to a local or global coordinate system. The local coordinate system has its origin in the lower left-hand corner of the 3D terrain model. The global system is the system specified in the grid.gws file. Default value is Local (-).
X and Y position
The X and Y position of the objects according to specified coordinate system. For Climatology objects the position cannot be changed, because it is specified in the .wws file. The .wws file can be opened in a text editor by clicking the Tools->View climatology data (.wws) menu item.
3. Noise calculation
Based on broadband
A map of sound pressure level Lp [dB(A)] is calculated at the Noise map height, optionally accounting for the background sound level. The noise level is calculated for a particular wind condition, specified by the user, therefore a wind speed at a given height has to be specified by the user. WindSim will calculate for the assigned wind condition the wind speed at each hub position, according to the Wind Fields calculations, and the relative sound power level Lw. In order to estimate the power level, the wind speed at the hub is tranferred to the reference height assigned in the .pws file by using a power law with a wind-shear exponent of 1/7.
The sound pressure level Lpi(x,y) at a generic point P(x,y) produced by the i-th wind turbine is given by:
Lpi(x,y) = Lwi - 10 Log10 (2 π di2) - α di
where:
Lwi = broadband sound power level [dB(A)] of turbine i-th;
di = distance of P(x,y) to the i-th turbine, [m];
α = broadband attenuation coefficient, [dB(A)/m];
While the sound pressure levels due to the different wind turbines, and eventually the background sound pressure level, are summed according to the decibels rules.
Lp(x,y) = 10 Log10 10 0.1 Lpi + 10 0.1 Lpbg)
Noise map height
The height at which the sound map is extracted. The map height [m] is given as a real number.
Background noise
Optional background noise [dB(A)] for the sound pressure level calculation. A default value of 0 will produce a map not accounting for background noise.
Attenuation coefficient
Broadband attenuation coefficient [dB(A)/m] to account for the noise absorption of the air.
Noise at height
Height [m] above ground level at which the wind speed and direction condition is assigned.
Noise coordinate system
Specify which coordinate system Global/Local is used to assign the x y coordinates at which the wind conditions (wind speed and direction at Noise at height) are given.
Conditions X position
X (easting) coordinate of the point used to specify the wind conditions.
Conditions Y position
Y (northing) coordinate of the point used to specify the wind conditions.
Noise at wind speed
Wind speed condition [m/s] at which the noise map is calculated.
Noise at wind direction
Wind direction condition [deg], measured clockwise from north, at which the noise map is calculated.
4. Terrain Complexity
Terrain complexity calculation is performed at each turbine position and climatology position, following the IEC standard and getting WindSim complexity indexes, see terrain complexity.
The terrain complexity parameters and the cross-checking can be send back to WindSim in an anonymous way. This will enable us to create a data base and to give some estimations for the losses & uncertainty tool about the model error.