Here are some facts about a typical turbine: Question What is the ‘swept area’ of the turbine? Extension Question What is the percentage increase in swept area if the blade length is increased by 1 metre? Hub height 96 m Rotor diameter 82 m Blade length 40 m Blade rotation 12 to 21 rpm As of November 2014, there are 28 onshore wind farms in Wales. Between them they share 498 wind turbines. Wind Turbines