A blade adapter for rotor blades of wind turbines, for increasing the rotor diameter, has a first end for attaching to the rotor hub, and a second end, spaced apart in the axial direction, for connecting to the blade root of a rotor blade. In addition, the blade adapter, at its first and second end, has a pitch circle for connecting to the rotor hub or to the rotor blade, wherein the wall of the blade adapter extending in the axial direction is open outwardly, in the form of a truncated cone, from the first end toward the second end, in at least one portion.

An example wind turbine is provided that includes a shaft assembly, strut mounts coupled to the shaft assembly, airfoils directly or indirectly coupled to the strut mounts, and a generator assembly connected to the shaft assembly. The shaft assembly defines a central longitudinal axis of the wind turbine. The airfoils are capable of being positioned in a fully extended orientation and a fully retracted orientation. Rotation of the airfoils results in rotation of at least a portion of the shaft assembly to generate electrical current with the generator assembly.

An aerofoil module for use in a blade of a propeller or turbine comprising: a body comprising a suction surface and a pressure surface; an air passage traversing the body, the air passage having an entrance opening on the pressure surface and an exit opening on the suction surface; a cover for covering a variable portion of a cross-section of the air passage; and a mechanism for varying the portion of the cross-section of the air passage covered by the cover, wherein the mechanism reacts passively to the oncoming air speed of oncoming air in the axial direction of the propeller/turbine; wherein the mechanism varies the portion of the cross-section covered by the cover such that the cover covers a smaller portion of the cross-section in response to a higher oncoming air speed, and covers a larger portion of the cross-section in response to a lower oncoming air speed.

An aerofoil module for use in a blade of a propeller or turbine comprising: a body comprising a suction surface and a pressure surface; an air passage traversing the body, the air passage having an entrance opening on the pressure surface and an exit opening on the suction surface; a cover for covering a variable portion of a cross-section of the air passage; and a mechanism for varying the portion of the cross-section of the air passage covered by the cover, wherein the mechanism reacts passively to the oncoming air speed of oncoming air in the axial direction of the propeller/turbine; wherein the mechanism varies the portion of the cross-section covered by the cover such that the cover covers a smaller portion of the cross-section in response to a higher oncoming air speed, and covers a larger portion of the cross-section of the air passage in response to a lower oncoming air speed.

This invention relates to an arrangement for a surface area adjustment of a reciprocating wing system in a wave energy recovery system where the wave energy recovery system comprises at least a body, a set of wings fastened to a support means that is hinged at its lower ends onto the body to make a reciprocating motion in response to kinetic energy of waves or tidal currents, and a power-take-off means. The arrangement comprises at least adjustment means capable to adjust the total effective surface area of the wings.

Disclosed is a dynamic turbine, capable of altering the sweep area in a large interval by moving a first fixing structure, a second fixing structure and blades to and from an essential same plane along an axis of rotation of the turbine.

The lengths and/or chords and/or pitches of wind turbine or propeller blades are individually established, so that a first blade can have a length/chord/pitch that is different at a given time to the length/chord/pitch of a second blade to optimize performance and/or to equalize stresses on the system.