Windmills. (Source: © Eric Gevaert / stock.adobe.com)

An old facility that used wind power to spin a drag-principle rotor to drive equipment for grinding grain or pumping water for irrigation. A windmill usually has four flat vanes made of wood and canvas that can stretch or skew across the vanes depending on the wind intensity. The rotating vanes then drive an internal device that can be used to grind grain, power saws, trip hammers or power irrigation pumps. Nowadays, the term windmill is sometimes used to refer to a wind power plant.