Wake Effects

Wake effect from wind turbine (Picture © Riso National Laboratory, Denmark)

Energy cannot be created nor consumed, only transformed. Therefore, since wind turbines produce electrical power from the wind energy, it's clear that the wind leaving the turbine must have a lower energy content than the wind arriving in front of the turbine.

A wake will be created behind the turbine. Flow in this trail is quite turbulent and slowed down when compared with the flow arriving in front of the turbine. On the above picture, the wake can be seen thanks to the addition of smoke to the air passing through the turbine.

In order to avoid too much turbulence around the turbines downstream, wind turbines are usually spaced at least three rotor diameters away from one another. In the main wind direction turbines are usually spaced even more, as explained below.

Park Effect

Because of the wake effect, each wind turbine will slow down the wind behind it as it converts wind energy into electricity. Ideally, it would be interesting to space turbines as far apart as possible in the prevailing wind direction in order to minimise energy losses.

On the other hand, land use and the cost of connecting wind turbines to the electrical grid encourage to reduce the space between them. A compromise must then be found between these two parameters. Typically, the energy loss is about 5 percent.

Park Layout

Usually, the space between turbines in wind parks is somewhere between 5 and 9 rotor diameters apart in the prevailing wind direction, and between 3 and 5 diameters apart in the direction perpendicular to the prevailing winds. In the above example, turbines (white dots) have been spaced by 7 diameters apart in the main wind direction and by 4 diameters in the perpendicular direction