Panemone windmill

A panemone windmill is a type of vertical axis wind turbine. It has a rotating axis positioned vertically, while the wind-catching blades move parallel to the wind. By contrast, the shaft of a horizontal axis wind turbine (HAWT) points into the wind while its blades move at right-angles to the wind's thrust. That is, a panemone primarily uses drag whereas the blades of a HAWT use lift.

Historically the earliest known wind machine was made by the Persians and it was the panemone design, consisting of a wall, with slits, surrounding a vertical axle containing four to eight fabric sails. As the wind blew, the sails would turn the axle, which was in turn connected to grain grinders or some form of water transportation device (though little is known of the actual details of such methods).

No one knows when people first built windmills to do work. The first instance may have been in China more than 2,000 years ago, but archaeologists have found no definite record of their use there before 1219 AD. The earliest recorded windmill design found was Persian in origin, and was invented around 500–900 AD. This design was the panemone, with vertical lightweight wooden sails attached by horizontal struts to a central vertical shaft. It was first built to pump water, and subsequently modified to grind grain as well.

Before becoming a slave to Calif Umar, Pīrūz Nahāvandi used to design and build windmills. In the 9th. century AD., Pīrūz brought a complaint to Umar about the high tax charged to him by his master Mughirah. Umar wrote to Mughirah and inquired about the tax; Mughirah's reply was satisfactory, but Umar held that the tax charged from Abu Lulu was reasonable, owing to his daily income. Umar then is reported to have asked Abu Lulu to design a windmill for him, in which Pīrūz replies, " By God, I will build this [wind]mill of which the World will talk".

The vanes of a panemone are moved by the wind in a circle to turn the drive shaft. To accomplish this they must move with the wind only while on one side of the circle, and move against the wind on the other side. To prevent the vanes moving upwind from being blown back by the wind, one half of the panemone may be shielded, or else the vanes may be attached so that they can turn edge-on to the wind when the wheel is moving them upwind.

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