Panemone Windmill

A panemone windmill is a type of vertical axis wind turbine whose wind catching blades move parallel to the wind rather than perpendicular to it, the way a horizontal axis wind turbine blades do, and its own reliance on aerodynamic drag rather than lift makes the design comparatively rudimentary and inefficient. The earliest documented example was built in Persia, using a wall with slits surrounding a vertical axle carrying four to eight fabric sails; wind blowing through the slits turned the axle, which was linked to grain grinding or water lifting machinery. The clearest early evidence places the design in ninth century Sistan, in what is now Iran and Afghanistan, around 700 to 900 AD, after which it spread across the Islamic world and eventually reached India and China. Despite ranking among the least efficient wind turbine designs, the panemone has been repeatedly reinvented and patented over the centuries.