Wind energy is the most promising source of renewable energy in response to the emerging needs for replacement of the conventional power plants. Currently, the two main devices for generating electricity from wind energy are vertical axis wind turbines and horizontal axis wind turbines. The vertical axis turbine is more suitable for application in the urban and rural areas due to its ability to operate in a lower wind speed range, high turbulence, and capability to accommodate wind from any direction. There are two types of vertical axis wind turbines; the Savonius and the Darrieus with opposing capabilities. The Savonius turbine is a self-starting turbine but has low efficiency due to the drag type blades. Alternatively, the Darrieus turbine has airfoil blades that generate lift (force) that makes the turbine high efficiency. Initially, when the turbine is at rest the airfoil blades do not generate enough torque to start the turbine because of inadequate relative angles of attack. Currently, the start problem has been solved by using hybrid systems that combine Savonius and Darrieus turbines to form a self-starting system. This increases the turbine complexity, cost of manufacturing and maintenance, and has the average of both turbine efficiencies.
We developed a novel vertical axis wind turbine of the Darrieus type that has the advantages of a high efficiency turbine and the self-starting feature. The turbine has a new blade passage design that generates thrust to start the turbine from rest, independent of the blade angle of attack relative to the wind. As the turbine starts to rotate, the relative blade angle of attack becomes adequate for generating torque for electric power generation. In addition, the generated thrust from the blade passage further enhances the turbine efficiency beyond the classical Darrieus turbine. A prototype has been built and tested to validate the new design. The proposed turbine has the advantages of self-starting, increased efficiency, reduced material, and lower manufacturing cost which in turn will lower the turbine price for consumers.