Pitstone Windmill, believed to be the oldest windmill in the British Isles
A windmill is an engine powered by the energy of wind. It often refers to an engine contained in a large building as in traditional post mills, smock mills and tower mills . It also refers to small tower mounted wind engines used to pump water on farms and modern wind turbines for generating electricity.
In Europe, windmills have been used since the Middle Ages; regions famous for their windmills include the Netherlands and La Mancha, Spain. Windmills were developed from the 12th century, apparently from technology gained by crusaders who came into contact with windmills in the Middle East. Persian sources indicate windmill use as early as the 7th century BC 1 2. Common applications of windmills are grain milling, water pumping, threshing, and saw mills. Over the ages, windmills have evolved into more sophisticated and efficient wind-powered water pumps and power generators.
In the United States
The development of the water-pumping windmill in the USA was the major factor in allowing the farming and ranching of vast areas of North America, which were otherwise devoid of readily accessible water. They contributed to the expansion of rail transport systems, throughout the world, by pumping water pumping water from wells to supply the needs of the steam locomotives of those early times. They are still used today for the same purpose in some areas of the world where a connection to electric power lines is not a realistic option.
The multi-bladed wind turbine atop a lattice tower made of wood or steel was, for many years, a fixture of the rural landscape throughout rural America. These mills, made by a variety of manufacturers, featured a large number of blades so that they would turn slowly but with considerable torque in low winds and be self regulating in high winds. A tower-top gearbox and crankshaft converted the rotary motion into reciprocating strokes carried downward through a pole or rod to the pump cylinder below.
In areas not prone to freezing weather, a pump jack (or standard) was frequently mounted at the top of the well in the center of the base off the tower. This was the connection between the windmill and the pump rod, which generally went through the drop pipe to the cylinder below. The pump jack provided a means for manual operation of the pump when the wind was not blowing. Some pump jacks provided a sealed connection, allowing water to be forced out under pressure allowing a tank at a higher elevation to provide water for a home and other uses, but many had a simple spout allowing water to flow away in a trough by gravity.
The drop pipe and pump rod continued down deep into the well, terminating at the pump cylinder below the lowest likely groundwater level. A suction tube usually continued a short distance more. This arrangement allowed wells as deep as 1200 feet (370 m) to be constructed, though most were much more shallow.
Windmills and related equipment are still manufactured and installed today on farms and ranches, usually in remote parts of the western United States where electric power is not readily available. The arrival of electricity in rural areas, brought by the [[Rural Electrification Administration REA in the 1930s through 1950s, contributed to the decline in the use of windmills in the US. Today, with increases in energy prices and the expense of replacing electric pumps, has led to an increase in the repair, restoration and installation of new windmills.
Test and construction
Small windmills for urban rooftop use