BALANCED STRESS VERTICAL AXIS WIND TURBINE

Balanced Stress Vertical Axis Wind Turbine of the Disclosure Curved airfoils are mounted on members attached to a vertical shaft. The ends of the airfoils point outward from the shaft, The members are attached to the upper and lower sections of the airfoils and converge as they approach the shaft. This minimizes the shaft length above the turbines upper most bearing and provides a balanced condition that distributes forces in such a manner which reduces airfoil stress. The invention relates to vertical axis wind turbines having airfoils radially disposed about their axis of rotation, wherein airfoil stress is balanced against reaction forces. The length of the shaft above the upper most bearing of a vertical axis wind turbine having no support structure above its airfoils, is usually one half the length of its airfoils. This results in a large bending moment on the shaft, hence its diameter must be made large for the power it handles. In this type of turbine members are used to connect the airfoils to the vertical shaft. In the vertical axis wind turbine using a troposkein shape, a supporting structure such as guy wires must be employed or a very thick shaft used. In the present invention airfoil stress due to centrifugal forces is balanced against reaction forces set up in the members used to connect them to the shaft.To provide this condition these members must converge as they approach the shaft.This will permit the use of a relatively short shaft above its upper most bearing, thus reducing shaft diameter and bearing size. An objective of the invention is to reduce airfoil stress as compared to what it would be in a vertical axis wind turbine using straight airfoils. Another objective is to reduce shaft diameter and bearing size.