Process — How a wind turbine generates electricity

The diagram shows the five stages by which a wind turbine converts moving air into electricity for the grid.

Overall, the story of the diagram is one of amplification: the blades themselves turn surprisingly slowly, and it is the gearbox inside the nacelle that multiplies this rotation about a hundred times before it reaches the generator.

The process begins with the wind, which blows most reliably on hills and offshore — the sites where turbines are usually placed. The wind pushes the three blades, each up to eighty metres long, and they rotate at only about fifteen turns per minute. This slow rotation is fed into the nacelle at the top of the tower, where the gearbox speeds the shaft up a hundredfold and passes it to the generator, which produces the current.

The electricity then travels down a cable inside the tower to ground level, where a transformer raises the voltage so that the power can be carried efficiently. Finally, pylons take it into the national grid and on to homes — a single large turbine supplying roughly 1,500 households, though only, of course, while the wind is blowing.