EnvironmentalSensorLayers help users assess and limit environmental impact at points of interest. Generally, such layers can be digitized in Openwind or converted from a PointLayer such as a buildings layer.
Openwind offers a tab for each type of environmental impact it attempts to model: visual, noise and shadow flicker. The impacts shown in the Environmental-Sensor-Layer properties are recalculated each time the dialog is shown. You can output a report of all the environmental impacts using the Report Environmental Impacts button shown in figure 65. Checking the box next to that option will only output results for sensors which are non-compliant in some way. This means that a limit has been set for some type of impact and that limit has been broken (e.g. noise limit of 45 dB and noise level of 45.1 dB).
The Visual Impact tab in figure 66 outlines the visual impact at the currently selected point object in terms of the number of turbine hubs and tips visible (see Section 42 for more) as well as the horizontal or panoramic impact of each wind-farm (represented by different SiteLayers).
The Visual Impact tab allows the user to set limits on the visual impact at each location in the EnvironmentalSensorLayer.
Figure 66 shows the Noise tab, which reports the noise at the currently selected location and allows the user to set a noise limit at this location as well as to set a different receptor height. The noise value is calculated using the current noise model options. The octave band sound pressure levels only show when the octave band spreading model is selected in the Noise Model settings.
The limits on noise and visual impact are applied as constraints to the layout optimiser. In order to successfully place a turbine, the layout as a whole must not break the limits set in the environmental sensor layers.
It is theoretically possible to set limits on the shadow flicker that may be suffered at the sensor locations. However, due to processing requirements, it is not practical in Openwind as of yet. It is part of the framework, though, and could be included at a future date.
When setting environmental sensor limits on noise and visual impact, it is important to bear in mind that this may restrict a site to the point at which it is no longer possible to fit as many turbines into the site as the user would like. The optimiser may not be able to find a solution in such a case. If this happens, the user can remove several turbines—in the extreme case, this would leave just one turbine—and grow the layout (see optimiser options for more info) to discern how many turbines may be accommodated within the site while still satisfying the environmental impact constraints.
Shadow flicker is modelled using freely available NREL solar declination code SPA to calculate the sun vector minute-by-minute over the course of a year. Users may view the resulting information as a total number of minutes or in calendar form as seen in figure 66 (see Shadow Flicker ). It is important to check the button Use sensor bearing (from Camera tab) if you want this sensor to be directional with respect to shadow flicker.
The Camera tab, shown in figure 67, allows the user to output a KML file showing one or more wind farms from the currently selected point of view.
For a terrain profile between a turbine and a sensor, please see the section on Terrain Transect.
Display and edit bearings - this displays and edits the bearing of the view of each sensor. Changing the values of the bearing will be reflected in the map view in real time. Checking this box will make visible the bearings of all the sensors in this layer.
It is possible to edit multiple environmental sensor points at once by pressing the drag-box button on the toolbar and holding the left mouse button whilst dragging a box from top left to bottom right to enclose the desired turbines of the currently selected environmental sensor layer.
For values that are marked as “mix”, leaving these will leave different values in different objects. Otherwise, editing them and pressing OK will write the values in this dialog to all the objects that were selected.
