Windmills
Find out how these towers have helped harness wind power throughout history
DID YOU KNOW? Windmills are so popular in the Netherlands that the country celebrates a National Windmill Day
It is thought that the windmill was invented around 1,500 years ago. Historians are still unsure exactly where the first one was constr ucted, but it is believed that it was either in ancient China or ancient Persia.
The first windmill mechanisms used millstones powered by sails that rotated a drive shaft to pump water or mill cereal. They became an integral part of anc ient agriculture and were also used in sawmills and to help with irrigation and drainage.
The first windmills turned on a vertical axis. L ater versions revolved hor i zontally, which was fou nd to be a more eff icient process. Tail fans were also added to later models to automatically move the sails in the direction the wind was blowing.
To remedy variable wind speeds, modern windmills utilise overspeed controls to turn the mechanism away from the wind if the gusts are too powerf ul for the sails to hand le. Before the invent ion of windmills, grinding corn, pumping water and cutting lumber was done by hand. Windmills sped up and increased the efficienc y of the process significantly, having a dramatic impact on the world’s agriculture and economy.
Inside a thatched smock mill
How a windmill uses wind power to mill grain
1 Revolving cap
The cap of the mill rotates to face whichever way the wind is blowing, increasing rotation speed
2 Sails
The lattice sails move anticlockwise, turning the mechanism inside in a clockwise direction
3 Brake wheel
The sails catch the wind and turn the horizontal wind shaft, which in turn revolves the largest cog, the drive gear
4 Dual millstones
The movement of the drive gear turns a vertical shaft that powers a millstone
5 Feeding the grain
The grain is fed into the two millstones by a hopper. One millstone is still while the other rotates
6 Grain to flour
The bottom floor is called the meal floor and is where the flour, barley or oats are collected
Why did windmills fall out of use?
The use of windmills has declined in the modern world. This is primarily down to the introduction of steam power in the Industrial Revolution. This reduction only became even greater than before when electricity came into common use. Today, windmills are mainly listed as heritage sites or have fallen into disrepair. Rather than grinding grain, today’s windmills take the form of wind turbines and are one of the world’s leading renewable energy sources. Moreover, simple wind pumps have been around since ancient times and are still commonly used both for draining wetlands and obtaining groundwater in areas short on drinking water.