A windmill is a machine which converts the energy of wind into rotational energy by means of vanes called sails or blades. Originally windmills were developed for milling grain for food production. In the course of history the windmill was adapted to many other industrial uses. An important non-milling use is to pump water, either for land drainage or to extract groundwater with windpumps. Windmills used for generating electricity are commonly known as wind turbines.
Spread and decline
The total number of wind powered mills in Europe is estimated to have been around 200,000 at its peak, compared to some 500,000 waterwheels. With the coming of the industrial revolution, the importance of wind (and water) as primary industrial energy source declined and was eventually replaced by steam (in steam mills) and internal combustion engines, although windmills continued to be built in large numbers until late in the 19th Century. More recently windmills have been preserved for their historic value, in some cases as static exhibits when the antique machinery is too fragile to put in motion, and in other cases as fully working mills. There are around 50 working mills in operation in Britain as of 2009.
Of the 10,000 windmills in use in the Netherlands around 1850, about 1000 are still standing. Most of these are being run by volunteers though there are some grist mills still operating commercially. Many of the drainage mills have been appointed as backup to the modern pumping stations. The Zaan district has been said to have been the first industrialized region of the world with around 600 operating wind powered industries by the end of the 18th century. Economic fluctuations and the industrial revolution had a much greater impact on these industries than on grain and drainage mills so only very few are left.Construction of mills spread to the Cape Colony in the 17th century. The early tower-mills did not survive the gales of the Cape Peninsula, so that in 1717 the Heeren XVII sent carpenters, masons and materials to construct a durable mill. The mill was completed in 1718 and became known as the Oude Molen and was located between Pinelands Station and the Black River. Long since demolished, its name lives on as that of a Technical school in Pinelands. By 1863 Cape Town could boast eleven mills stretching from Paarden Eiland to Mowbray.