A machine for generating usable energy from a wind source is provided. The machine includes a casing structure that may define an air inlet oriented with respect to a prevailing wind direction and an air outlet. The casing structure may be substantially cylindrical. A rotor having a blade structure is positioned within the casing structure and has a substantially vertical axis of rotation. The casing structure may include two side passages for creating a zone of low pressure downstream of the rotor near the air outlet.