A diffuser-augmented wind turbine may include an annular diffuser that may encompass a rotor such that the rotor and the annular diffuser may be coaxial about a main axis. A diffuser-augmented wind turbine may further include a flared diffuser assembly that may be connected to the annular diffuser such that an air stream discharged from the annular diffuser may enter the flared diffuser assembly. A flared diffuser assembly may include a fixed flared diffuser that may include a number of flared petals extending from a leading edge of the fixed flared diffuser toward the trailing edge thereof. A flared diffuser assembly may further include a rotatable flared diffuser that may be disposed coaxially within the fixed flared diffuser and rotatable about the main axis. A rotatable flared diffuser may include a number of flared petals extending from an annular leading edge of the rotatable flared diffuser toward a trailing edge thereof.