ABSTRACT
A duct, shroudshroud, or diffuser increases the power/area for a rotor by accelerating the air passing through the rotor, thereby increasing the velocity, by accommodating the expanded wind stream behind the rotor, and it also reduces tip losses. Ducted wind turbines are not a new idea as one was installed in San Gorgonia Pass, California, in the 1920s. A toroidal wind turbine is another design option that is similar to a ducted wind turbine. A number of designs and some installations have been developed by architects, inventors, and people selling wind systems to integrate wind turbines into building structures. Buildings block and accelerate wind flow, so there are a number of installations of turbines on parapets, facades, and as part of the original design of buildings. An early diffuser wind turbine was tested at the Beijing Badaling Wind Power Test Station, China. Two aspects touted by diffuser augmented wind turbines manufacturers are less vibration and less noise.
