Wednesday, August 15, 2007

Horizontal axis wind turbine

Visited the Bembridge windmill - the only extant windmill on the Isle of Wight.

All of the main elements are similar to most of the wind turbines currently available. The main gearbox is in the nacelle, changing the direction of rotation from horizontal to vertical, and you can just about make out the yawing gears at the top, which allow the nacelle to rotate to stay head to wind.

The blade thrust is controlled by reefing the sails, rather than by fancy feathering technologies, and you can see how the blade geometry allows for different angles of attack at different radii from the hub.

The difference is that the majority of power offtake is lower down the tower, where additional gears drive the grinding stones, rather than in the nacelles as at present. Perhaps there's something to learn from our predecessors?

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