A wind farm is a collection of wind turbines that operate as a single power station. Depending on its size, a wind farm will normally have a dedicated substation into which power from all the wind turbines is fed and from which it is carried to the nearest access point to the grid system (Figure 11.6).
Power can be fed either into a local distribution system, or, for the largest wind farms, directly into the transmission grid. As many wind farms are located in regions remote from existing transmission system backbones, wind power development will often involve additional transmission lines. This can add to the expense of a wind project.
When wind turbines are built close together they will often affect one another because, depending on the wind direction, some turbines will be down- wind of others and will therefore experience turbulence from the upwind turbines. Correct turbine placement is vital if a wind farm is to extract the maximum energy from the resource.
Onshore wind farms are generally limited in size and this, together with the nature of the terrain, will often make turbine placement less critical. For off- shore construction, however, where individual turbines are larger and the number of turbines can be larger too, placement can be critical and can in some cases affect the economics of a project. Energy losses due to poor placement of up to
10% have been recorded. Modeling airflow over the wind farm site is the best way to determine the optimum placement, but computer modeling techniques have yet to reach the level of sophistication to accurately model a large offshore wind farm.
Maintaining a good distance between wind turbines means that wind farms can end up occupying a very large area of land or sea. This is not necessarily a handicap because the turbines generally occupy less than 1% of the actual area. The remainder is usually accessible for farming use onshore or for fishing or the passage of ships offshore.