Horizontal axis wind turbine and method for generating electrical energy

A horizontal axis wind turbine, comprising a turbine unit, a turbine unit supporting frame, a generator configured for generating electrical energy, and a yaw bearing mechanism, wherein the turbine unit is supported on one or more bearings by the turbine unit supporting frame,

• wherein the turbine unit is rotatable about a horizontal rotation axis to drive the generator in a direction of rotation,
• wherein the yaw bearing mechanism is configured for mounting the turbine unit supporting frame to a support structure such that the turbine unit supporting frame is rotatable about a Z axis,
• the turbine unit comprising:
• a central hub arranged on said horizontal rotation axis, said central hub having a front end and a rear end, said central hub having an exterior hub surface,
• a plurality of rigid twisted blades, and
• an outer tubular shroud having a front end, a rear end, an inner shroud surface, an inner diameter defined by said inner shroud surface, and an outer shroud surface, an outer diameter defined by said outer shroud surface, and a shroud length between said front end of the outer tubular shroud and said rear end of the outer tubular shroud along said horizontal rotation axis,
• wherein the wind turbine is configured so that, in use, wind flows through and past the turbine unit including along the inner shroud surface and the outer shroud surface from the front end of the outer tubular shroud to the rear end of the outer tubular shroud,
• wherein each rigid twisted blade of the plurality of rigid twisted blades has a leading edge, a trailing edge, a chord length between said leading edge and said trailing edge, a root end, and a tip end,
• wherein the root end is integral with the central hub and the tip end is integral with the outer tubular shroud so that the turbine unit is rigid, wherein the leading edge and the trailing edge adjoin the outer tubular shroud, and wherein the leading edge and the trailing edge adjoin the central hub,
• wherein each rigid twisted blade of the plurality of rigid twisted blades has a first main surface and an opposed second main surface, each of said first main surface and said second main surface extending from the leading edge to the trailing edge, wherein, seen in the direction of rotation of the turbine unit during operation, the first main surface precedes the second main surface,
• wherein a chord length of each rigid twisted blade of the plurality of rigid twisted blades is at least ⅕ of a smallest inner diameter of the outer tubular shroud,
• wherein the first main surface and the second main surface of each rigid twisted blade of the plurality of rigid twisted blades have a gradual twist from the leading edge towards the trailing edge, wherein the gradual twist is counter to the direction of rotation,
• wherein each rigid twisted blade of the plurality of rigid twisted blades is embodied as an aerofoil having a profile with a camber line midway between the first main surface and the second main surface, wherein the profile has a thickness that varies in direction of the camber line, said thickness being perpendicular to the camber line,
• wherein the profile of the aerofoil is configured to produce a lift force that contributes to said rotation of the turbine unit in said direction of rotation,
• wherein the outer tubular shroud has a conical shroud section over at least 60% of the shroud length, the conical shroud section extends up to the rear end of the outer tubular shroud, within the conical shroud section, the inner shroud surface and the outer shroud surface each gradually increase in diameter towards the rear end of the outer tubular shroud,
• wherein the outer tubular shroud is provided with an outwardly protruding annular brim flange at the rear end of the outer tubular shroud,
• wherein the central hub comprises a conical hub section in which the exterior hub surface increases in diameter towards the rear end of the central hub, wherein the conical hub section extends over a length along the rotation axis at least through the conical shroud section.