Stormblade, works by accelerating the wind onto the blades and is therefore more efficient at low as well as high wind speeds. Accordingly, "Bird and bat friendly, the design does not have the mechanical noise often associated with commercial wind turbines and, as a result, is very silent in operation. It has fewer parts and higher generating capacity than other models and can theoretically, operate at any wind speed... Stormblade Turbine can convert up to 70 per cent of wind power into electricity, double the current average. Operational wind speed is expected to be 7mph to120mph, double the current average range ...". The Stormblade project has a website here.
"Stormblade:" The First Truly Quiet Residential Wind Turbine (TreeHugger)