Royd Moor wind farm at twilight. Wind power creates no emissions, and is reasonably efficient. By altering the angle which the turbine blades present to the wind, some adjustment may be made for changes in wind velocity. However, the nature of the weather means that wind power may only be used as an adjunct to other sources - reducing the demand on fossil or nuclear fuels. Wind farms are also quite noisy, primarily made by the blades and the generators. Photographed near Penistone, South Yorkshire, UK.