Calculating Shadows from Wind Turbines

Calculating Shadows from Wind Turbines

Daily Shadow Variation - Worst Case

Rotor shadow simulaton This simulation of shadow casting shows how the rotor shadow moves (worst case) from sunrise to sunset on a particular day at a certain location on the globe. The image is seen directly from above, with the centre of the wind turbine tower placed at the tiny black dot in the centre. The shadow positions are shown for every half hour during the day. Shadows, of course, are long around sunrise and sunset, and short at noon.
This particular set of images was made for 55° Northern latitude for 21 September, assuming a 43 m rotor diameter on a 50 m tower, using the shadow simulation programme on this web site.
Doing a worst case simulation we assume that the rotor yaws so as to track the movement of the sun exactly. This is is equivalent to assuming that the rotor is a solid balloon (or a Darrieus turbine).

Map of maximum (worst case) shadows around a 600 kW wind turbine placed at 55 degrees Northern latitude. The turbine has a 43 m rotor diameter and a 50 m tower. The map is 1200 m wide (East - West) and 750 m in the North - South direction. The map was computed using the Wind Turbine Shadow Calculator on this web site.

Annual and Daily Shadows - Worst Case

Worst case shadows for Copenhagen This map shows how shadows are typically distributed around a wind turbine throughout a year, assuming a worst case direction of the rotor. You will notice a number of kidney-shaped or bell-shaped areas around the wind turbine in the centre of the map. Each of the grey areas represents a certain maximum number of minutes of shadow from the wind turbine rotor. Since this map was computed for 55 degrees latitude in the Northern hemisphere, there is no shadow South of the turbine.

Timing Shadows
You will notice from the white lines on the map, that we can easily predict the time of day when shadows may occur. The shadow will e.g. obviously be directly North of the turbine at solar noon, when the sun reaches its maximum height in the sky. (Solar noon varies a bit during the year relative to our clocks, but it is fairly close to 12 o' clock, local time). The shadow will be to the bottom left at 4 o'clock in the morning on a summer day, so shadows to the Southwest are a minor problem in the Northern hemisphere. (The shadows occur in summer only, and at 4 in the morning most neighbours will be asleep anyway).
The commercial software we referred to earlier will tell you exactly the dates and times when shadows may occur.

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© Copyright 1998 Soren Krohn. All rights reserved.
Updated 26 September 2000
http://www.windpower.org/tour/env/shadow/shadow.htm


		Calculating Shadows from Wind Turbines Daily Shadow Variation - Worst Case This simulation of shadow casting shows how the rotor shadow moves (worst case) from sunrise to sunset on a particular day at a certain location on the globe. The image is seen directly from above, with the centre of the wind turbine tower placed at the tiny black dot in the centre. The shadow positions are shown for every half hour during the day. Shadows, of course, are long around sunrise and sunset, and short at noon. This particular set of images was made for 55° Northern latitude for 21 September, assuming a 43 m rotor diameter on a 50 m tower, using the shadow simulation programme on this web site. Doing a worst case simulation we assume that the rotor yaws so as to track the movement of the sun exactly. This is is equivalent to assuming that the rotor is a solid balloon (or a Darrieus turbine).
Map of maximum (worst case) shadows around a 600 kW wind turbine placed at 55 degrees Northern latitude. The turbine has a 43 m rotor diameter and a 50 m tower. The map is 1200 m wide (East - West) and 750 m in the North - South direction. The map was computed using the Wind Turbine Shadow Calculator on this web site.		Annual and Daily Shadows - Worst Case This map shows how shadows are typically distributed around a wind turbine throughout a year, assuming a worst case direction of the rotor. You will notice a number of kidney-shaped or bell-shaped areas around the wind turbine in the centre of the map. Each of the grey areas represents a certain maximum number of minutes of shadow from the wind turbine rotor. Since this map was computed for 55 degrees latitude in the Northern hemisphere, there is no shadow South of the turbine. Timing Shadows You will notice from the white lines on the map, that we can easily predict the time of day when shadows may occur. The shadow will e.g. obviously be directly North of the turbine at solar noon, when the sun reaches its maximum height in the sky. (Solar noon varies a bit during the year relative to our clocks, but it is fairly close to 12 o' clock, local time). The shadow will be to the bottom left at 4 o'clock in the morning on a summer day, so shadows to the Southwest are a minor problem in the Northern hemisphere. (The shadows occur in summer only, and at 4 in the morning most neighbours will be asleep anyway). The commercial software we referred to earlier will tell you exactly the dates and times when shadows may occur.
		\| Back \| Home \| Forward \| © Copyright 1998 Soren Krohn. All rights reserved. Updated 26 September 2000 http://www.windpower.org/tour/env/shadow/shadow.htm