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14. CONSTRUCTION: What is a wind turbine and how does it work? A wind turbine transforms the kinetic energy of the wind into mechanical or electrical energy. Wind turbines consist of a foundation, a tower, a nacelle and a rotor. The foundation prevents the turbine from falling over. Construction minimises disturbance of surrounding land. The tower holds up the rotor and a nacelle. It can be up to 100m high. The nacelle contains the main axle, gearbox, generator, transformer and control system. The rotor includes the blades and hub, which holds them in position as they turn. Most commercial wind turbines have three rotor blades. The length of the blades is approx ½ the height of the tower. Towers are built in a number of parts (2 or 3); Carried to site by truck. Cranes are used to construct the towers. Blades are joined on ground below and then lifted into place by crane. What are wind turbines made of? Towers are tubular steel. The blades are fibre-glass reinforced polyester. They are light grey or off-white because it is inconspicuous under most lighting conditions. The finish is matt, to reduce reflected light. How does a wind turbine generate electricity? Wind passes over the blades creating lift, which causes the rotor to turn. The blades turn a low-speed shaft inside the nacelle: gears connect the low speed shaft of the rotor with a high speed shaft that drives a generator. Here, the slow rotation speed of the blades is increased to the high speed of generator revolution. The rapidly spinning shaft drives the generator to produce electric energy. Electricity from the generator passes through to a transformer which converts it to the correct voltage for the distribution system. The electricity is then transmitted via the electricity network. How much electricity does a wind turbine generate? The output of a wind turbine depends on the turbine's size and the wind's speed through the rotor. Wind turbines manufactured today have power ratings ranging from 250 watts to 7 MW. Those proposed for Mt Emerald will be around 3MW. How fast do the blades turn? The blades rotate at between 15-20 revolutions per minute at constant speed. How long does it take to build? Construction time is relatively short. A larger than 100 MW wind farm can be ready in 18 months to three years. It takes 2-3 years to develop, and 1-2 years to build. Why do turbines sometimes stand still? There are a number of reasons why turbines are not always spinning: Turbines have to be stopped for scheduled maintenance, for repairing components or if there is a failure that needs to be checked. If there is too little or too much wind. Wind turbines operate from when the wind is above 15m/s. If the wind is below that they do not operate. If the wind is too strong, the turbine needs to be shut down: In a cyclone, the wind turbines will not turn – they will be ‘feathered’ so that the high wind passes over them, or locked because it could be damaged. When electricity demand is low, then electricity from wind turbines is not needed and they switch off. WILL construction trucks DESTROY OUR ROADS AND KILL OUR PEOPLE? Construction vehicles will travel on existing major roads to bring towers and plant to the site. Qualified and aware (inducted) drivers in roadworthy trucks will be used – if long loads, they will be escorted to site. Speed limits and expected behaviour will be clearly defined and adhered to. Roads constructed internally on the site to allow access to tower pads for construction and ongoing maintenance – these will be kept to a minimum, and designed for purpose – for the size of the small number of vehicles to be used; minimal impact on the environment and requiring simple ongoing maintenance.