Designing a wind farm - Part I - Location

The choice of an area as suited for building a wind farm largely depends on the area’s type and amount of wind (the ‘wind regime’). When it comes to placing the turbines in the area, other factors come into play. The basic aim of a wind farm and its design is to maximize energy production, minimize capital costs and stay within the constraints imposed by the site. The energy production is determined by the wind regime at the chosen site, the layout of the wind farm layout and the choice of wind turbine.

The factors most likely to affect turbine location are as follows:

1. Optimizing energy production

It is necessary to look not only at the wind conditions around a measuring mast but also everywhere a wind turbine is to be put up. In order to find the optimum areas for turbine placement, a wind stream field/wind resource map can be calculated, using information from a measuring mast and the topography (the “roughness” of the terrain, such as trees and buildings) and the orography (the terrain’s “contours”, such as hills and mountains). It is possible to simulate the wind conditions at every single spot on the given site and to calculate the energy production of each turbine. Ideally, the area should be as wide and open as possible in the prevailing wind direction, with few obstacles.

2. Visual influence

Likewise it is possible to calculate the zone of visual influence (ZVI) in the form of a map. A wind farm of a few, larger turbines are usually preferable to many smaller ones.

3. Access and maintenance constraints

The turbines need to be easily accessible for maintenance and repair work when needed.

4. Noise

The noise made by wind turbines has been significantly reduced. The noise levels can be calculated so the farm is compatible with the acceptable levels of sound as usually stipulated in national legislation.

5. Turbine spacing

The supplier defines the minimum acceptable turbine spacing, taking into account the effect one turbine can have on others nearby (the “wake effect”). The nature of the terrain and the wind rose (which measures wind speed and direction) of the given site also influence the positioning and spacing of the turbines.

6. Choosing the right turbine

The types of turbines chosen for the different sites depend on the wind conditions and the landscape features. This choice is also influenced by local restrictions on turbine height, noise levels and nature conservation, requirements from the authorities, the risk of extreme external influences such as earthquakes, the transport possibilities and the local availability of cranes. Software exists to simulate and optimize the design of the wind farm.

Reference: Wind Direction by EWEA, July 2009