This work presents a novel design for a rooftop wind tower system; the system is primarily intended for areas of low natural wind speeds. The relatively low natural wind is increased by a factor of about 1.6 times via a wind deflecting structure to reach the cut-in speed of typical rooftop wind turbines which is approximately 3 m/s. The system additionally responds to relatively high wind velocity, above 20 m/s, in a way that eliminates its wind speed amplification attributes; this will protect the wind turbines against exposure to high wind speeds that could be harmful to the turbines and to the mast structure that supports the turbine/generator. In case of high natural wind speed, above 20 m/s, passively controlled trap-doors, that are parts of the wind deflecting structure, allow wind to pass through the wind deflecting structure, thereby eliminating wind speed amplification of the deflecting structure. The design disclosed in this work comprises of a half cylinder wind deflecting structure that includes a plurality of spring loaded trap-doors; when closed, they form the wind deflecting structure up to a prescribed maximum natural wind speed. As the natural wind speed increases beyond its prescribed maximum, the spring loaded trap doors open as the result of the pressure exerted upon them by the wind. The design presented in this work increases the range of cut-in and cut-out wind speeds for a typical rooftop wind turbine.

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