Panemone

A panemone is a type of wind turbine. It is characterised by the fact that the rotating axis is positioned at 90 degrees to the direction of the wind, while the wind-catching blades move parallel to the wind. By contrast, the shaft of a propeller points into the wind while its blades move at right-angles to the wind's thrust. That is, a panemone primarily makes use of drag where a propellor uses 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).

History
It is unknown when windmills were first built with the purpose of doing 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.

Operation
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.

Efficiency
Wind-harnessing devices which rely on drag reach their maximum efficiency if the collector is pushed away from the wind. Because the wind panels do no work while returning to the upwind side of the device, the rotor in the Persian panemone design can only take energy from wind striking half the collection area (see diagram).

The panemone is one of the least efficient forms of wind turbine to be used. Despite this it is also one of the most commonly re-invented and patented forms.