Diffuser-augmented wind turbines can include a first diffuser ring arranged to form a turbine rotor cowling, the diffuser being fixed to and rotatable with the turbine rotor about the horizontal axis of the wind turbine. The first diffuser ring may have one or more dynamic, aero-elastic, vortex entrainment devices attached to a trailing edge of the diffuser. The first diffuser ring may include one or more slot gaps arranged within its body, each slot gap creating a channel between the interior and exterior surfaces of the first diffuser ring. In some embodiments the diffuser may optionally further include one or more further diffuser rings, the one or more further diffuser rings being static rings (e.g. non-rotatable about the horizontal axis) or dynamic diffuser rings (e.g. rotatable around the horizontal axis).

A drone with a horizontal rotor includes one or more rotor(s) (115, 116) which rotate in a horizontal plane, each rotor (115, 116) being equipped with one or more rigid or non-rigid blades (120, 121), the blade end being mounted on an electric motor (110, 111) with a propeller.

A set of units for assembly to form a wind turbine nacelle. The nacelle comprises a rotor-supporting assembly and generator, and a power conversion assembly and the set of units comprises a main unit arranged to be connected to a wind turbine tower and housing the rotor-supporting assembly and the generator, and at least two different auxiliary units each housing an operative component forming part of the power conversion assembly. To allow different wind turbine configurations, one of the auxiliary units can be selected from the at least two auxiliary units and assembled with the main unit to form the nacelle.