Quick facts

• The first modern wind turbine was built in Vermont in the 1940’s
• Wind turbines can be up to 200 m tall and a single rotor blade can be up to 60m long.
• Wind turbine towers are made out of steel and concrete. The blades are made of fibreglass, reinforced polyester or wood epoxy. The finish on both is matt to reduce glare from reflected light.
• The largest wind turbine can be found in Hawaii and stands 20 stories tall and has blades the length of a football field.
• Wind turbines operate when the wind speed is between 13km/h and 90km/h
• A single turbine (depending on size and speed of operation) has a capacity of 2,5-3MW can produce more than 6 million kWh in a year.
• Wind turbine blades rotate between 15 and 20 revolutions per minute at constant speed.
• The life of a wind turbine is between 20 and 25 years, during which time they operate continuously for as much as 120,000 hours.
• A grouping of wind turbines is called a wind farm.
• Wind farms can be constructed both on land and offshore.

Wind farm

The typical operating sequence of a wind turbine is as follows:

• When the wind speed reaches around 4 metres per second, the turbine blades will spin up to operating speed, usually around 14 to 29 rpm (varies by turbine model), and starts generating electricity
• As the wind speed increases, the generator output increases
• When the wind speed increases to the rated wind speed (usually around 12-13 metres per second), the generator will output its nameplate-rated capacity (i.e. a 2.3MW turbine would now output 2.3MW)
• As the wind speed continues to increase, the generator output will remain at the rated capacity (i.e. 2.3MW) until the wind reaches the cut-out speed (usually around 25 metres per second)
• At this wind speed, the turbine will deploy its tip-brakes and then apply its disk brake, stopping the blades in a few revolutions
• It will then rotate itself 90 degrees out of the wind and park itself
• If the wind speed drops to a level below the cut-out speed for a sufficient length of time, the turbine will point itself back into the wind, release the brake, and resume power production.

Inside a wind turbine