Windmill Evolution

The history of wind power shows a general evolution from the use of simple devices driven by drag forces to heavy material to efficient aerodynamic lift devices. Aerodynamic lift isn’t a modern concept. The earliest known use of wind power was the sailboat. Ancient sailors understood lift although they didn’t understand the physics to explain how it worked.
Early windmills were used for tasks like grain grinding and water-pumping. The earliest known design was the vertical axis system developed in Persia in about 500 AD. The first known documented design is also of a Persian windmill. It had vertical sails made of bundles of reeds, which were attached to the central vertical shaft by horizontal struts.
Grain grinding was the first documented windmill application. A grinding stone was attached to the same vertical shaft. The machinery was commonly enclosed in a building which featured a wall to block incoming wind. This prevented wind from slowing the drag-type ...