Selecting a Wind Turbine Site
Bent Tree Picture
Photograph Soren Krohn
© 1997 DWIA
Bent Tree Picture Wind Conditions
Looking at nature itself is usually an excellent guide to finding a suitable wind turbine site.
If there are trees and shrubs in the area, you may get a good clue about the prevailing wind direction , as you do in the picture to the left.
If you move along a rugged coastline, you may also notice that centuries of erosion have worked in one particular direction.
Meteorology data, ideally in terms of a wind rose calculated over 30 years is probably your best guide, but these data are rarely collected directly at your site, and here are many reasons to be careful about the use of meteorology data, as we explain in the next section.
If there are already wind turbines in the area, their production results are an excellent guide to local wind conditions. In countries like Denmark and Germany where you often find a large number of turbines scattered around the countryside, manufacturers can offer guaranteed production results on the basis of wind calculations made on the site.
Look for a view
As you have learned from the previous pages, we would like to have as wide and open a view as possible in the prevailing wind direction, and we would like to have as few obstacles and as low a roughness as possible in that same direction. If you can find a rounded hill to place the turbines, you may even get a speed up effect in the bargain.
Grid Connection
Obviously, large wind turbines have to be connected to the electrical grid.
For smaller projects, it is therefore essential to be reasonably close to a 10-30 kilovolt power line if the costs of extending the electrical grid are not to be prohibitively high. (It matters a lot who has to pay for the power line extension, of course).
The generators in large, modern wind turbines generally produce electricity at 690 volts. A transformer located next to the turbine, or inside the turbine tower, converts the electricity to high voltage (usually 10-30 kilovolts).
Grid Reinforcement
The electrical grid near the wind turbine(s) should be able to receive the electricity coming from the turbine. If there are already many turbines connected to the grid, the grid may need reinforcement, i.e. a larger cable, perhaps connected closer to a higher voltage transformer station. Read the section on Electrical Grid Issues for further information.
Soil Conditions
Both the feasibility of building foundations of the turbines, and road construction to reach the site with heavy trucks must be taken into account with any wind turbine project.
Pitfalls in Using Meteorology Data
Meteorologists already collect wind data for weather forecasts and aviation, and that information is often used to assess the general wind conditions for wind energy in an area.
Precision measurement of wind speeds, and thus wind energy is not nearly as important for weather forecasting as it is for wind energy planning, however.
Wind speeds are heavily influenced by the surface roughness of the surrounding area, of nearby obstacles (such as trees, lighthouses or other buildings), and by the contours of the local terrain.
Unless you make calculations which compensate for the local conditions under which the meteorology measurements were made, it is difficult to estimate wind conditions at a nearby site. In most cases using meteorology data directly will underestimate the true wind energy potential in an area.
We'll return to how the professionals do their wind speed calculations on the following pages.
© Copyright 1997-2003 Danish Wind Industry Association
Updated 19 September 2003
http://www.windpower.org/en/tour/wres/siting.htm
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