PROBLEM TO BE SOLVED: To provide a Savonius vertical shaft windmill capable of using high speed wind having large energy and of reducing resistance by wind during a return motion in a zone where wind speed is low, and to provide a gyro mill vertical windmill of high output efficiency and also a wind power generation device applying the same.;SOLUTION: The Savonius vertical shaft windmill has tapered shape blades to change cross section area in an upper and lower direction (a vertical direction) of windmill blade. Since wind sped is higher in an upper side in general, the taper shape of the windmill blade has large wind receiving cross section area in an upper side and small wind receiving cross section area in a lower side. In a place where wind speed difference is upside down (low wind speed in the upper side and high wind speed in the lower side), the tapered shape of the windmill blade has large wind receiving cross section area in the lower side and small wind receiving cross section area in the upper side. Also, the same can rotate at low wind speed and output efficiency is increased by compounding with the gyro mill vertical shaft windmill of high output efficiency.;COPYRIGHT: (C)2007,JPO&INPIT
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