Small wind turbines Fig. 12: Power coefficient of the 402 tapered type. Fig. 16: Horizontal axis “Bellsion type” wind turbine (down-wind, 5-blade winglets). the performance of a rotor designed at a low tip-speed ratio (about λ=2) can be improved by increasing the number of blades and by adopting inversely tapered blades. Fig. 13: Power coefficient of the 204 inversely tapered type. Fig. 17: Fureai ranch in Tokyo Hachijo-island. Fig. 18: Hagiwara strawberry farm in Shizuoka. Vertical axis “Bellsion type” wind turbine (2-blade winglets). Fig. 14: Power coefficient of the 304 inversely tapered type. Conclusions The performance comparison of blades with different design tipspeed ratios, number of blades, and tapered types resulted in the following conclusions: - The rotor with tapered blades designed at a certain tip-speed ratio has a high torque coefficient for the greater chord length. - Increasing the blade number also contributes to improving the power coefficient. - The power coefficient of the rotor designed at a low tip-speed ratio (about λ=2) can be improved by increasing the number of blades and by adopting the inversely tapered blade shape. Contacts: nishizawa.yoshifumi@v90.ashitech.ac.jp taniguchi@globalenergy.co.jp Fig. 15: Power coefficient of the 404 inversely tapered type. No54 January 2010 / jec composites magazine