Abstract
The vertical axis wind turbine generators are mainly used for small size wind turbine generators, and are independent on wind direction. The rotor of the vertical axis wind turbine is required to start rotating at a low wind speed and to smoothly rotate with small torque loss so that the energy loss from the energy of wind is minimized and the power generation efficiency is increased. But when the rotor is designed according to the wind conditions and the safety factors in the international safety standard for small wind turbines, IEC61400–2, commercially-available bearings are not suitable for the rotor, because both of the static and dynamic load ratings are larger than those demanded for the vertical axis wind turbine. That is, the frictional force and the rotating torque resistance of the commercially-available bearings are too large for the rotor to meet the above mentioned requirements.
In this study, the bearings having the most suitable load ratings and the very low frictional force for the rotor were newly designed conforming to the wind conditions and the safety factors in the above mentioned IEC61400–2. And the low torque shaft unit for the rotor using these newly designed bearings was also designed and experimentally produced. This low torque shaft unit was equipped in the real vertical axis wind turbine and a demonstration experiment was conducted. The result of the experiment showed that the low torque shaft unit started rotating at low wind speed and the power generation efficiency was improved. It is verified that the low torque shaft unit satisfies the above mentioned requirements well.
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