Abstract: A wind-driven energy-generating device comprises a shroud having a throat within which the rotor blades of a turbine are mounted, an intake section upstream of and having an inner face converging towards the throat, and a diffuser section downstream of and having an inner face diverging away from the throat. To prevent premature air separation along the inner surface of the diffuser section, the device includes boundary layer control means comprising a plurality of air channels leading from an external surface of the shroud to the internal surface of its diffuser section for injecting a flow of air of high kinetic energy from the air stream external of the shroud to the boundary layer of the air stream within the diffuser section of the shroud.