Advice Section

Hill Effect

Posted on: May 11th, 2008
A common way of siting wind turbines is to place them on hills or ridges overlooking the surrounding landscape. In particular, it is always an advantage to have as wide a view as possible in the prevailing wind direction in the area.
On hills, one may also experience that wind speeds are higher than in the surrounding area. Once again, this is due to the fact that the wind becomes compressed on the windy side of the hill, and once the air reaches the ridge it can expand again as its soars down into the low pressure area on the lee side of the hill.

The wind in practice starts bending some time before it reaches the hill, because the high pressure area actually extends quite some distance out in front of the hill.

Also, you may notice that the wind becomes very irregular, once it passes through the wind turbine rotor.  As before, if the hill is steep or has an uneven surface, one may get significant amounts of turbulence , which may negate the advantage of higher wind speeds.