How Utility-Scale Wind Farms Work
The vast majority of the world’s wind energy is generated on wind farms. Ranging in size from a handful of turbines to hundreds, large-scale wind farms have become an increasingly common feature of the rural environment, especially in highly exposed terrain such as plateaus, mountain ridges, islands and gusty agricultural table-lands. Some of the earliest North American wind farms were built in California and southern Alberta. The world’s largest is being built in the Texas panhandle by oil billionaire T. Boone Pickens. Spread over 200,000 acres, his 4000-MW wind farm will have about 2,000 turbines and cost $6 billion.
Because wind is variable, turbines aren’t always producing power. In general, turbines have a “capacity factor” of 30 to 40 per cent, whereas, a well sited turbine will provide power 70 to 80 per cent of the time. The "capacity factor" is defined as a turbine’s actual energy output over one year divided by its total capacity (i.e., how much it could generate if it were rotating all the time).
Local wind speed is one of the most important factors that determine a wind farm's viability. Energy companies begin by consulting wind resource maps. These maps [e.g. www.ontariowindatlas.ca] offer high-level information on regional wind patterns, but the energy firms must then scout out specific locations on their own, erecting test towers equipped with instruments that measure wind frequency, intensity and direction.
When developers have identified a target region, they must secure access to the area in order to build service roads and turbine foundations. When the location is within Crown land or Aboriginal territory this process involves negotiations with government agencies and Aboriginal groups. When the land in the identified area is privately-owned, the developer must negotiate agreements with owners, typically paying them an annual fee for the right to build and operate turbines on their properties.
The turbines are placed at least several hundred metres away from one another, and their internal control systems are monitored electronically from a central control station. The electrical current generated by each turbine is directed through underground cables to the transformers in a “sub-station,” which is the point of connection between the wind farm and high-voltage power lines. From there, this renewable energy flows into the electrical grid and becomes part of the region’s overall power supply, along with conventional sources such as natural gas, hydro-electric and nuclear.
This interactive animation depicts average wind speeds during every month of the year across Canada using colour-coded tiles. Buttons below allow the user to select where the measurements were taken — at 30m, 50m or 80m off the ground.