Wind turbines

A wind turbine assembly comprising a tower, a head mounted on the upper end of said tower for swivelling about a vertical axis, a duct extending upwardly within said tower, and having an upper end and a lower end, a swivel joint between said head and the upper end of said duct, a wind turbine mounted on said head and having blades thereon, an air compressor mounted in said head, with the axis of the wind turbine and compressor being substantially horizontal, means operatively connecting the air compressor to the turbine, whereby the compressor is driven thereby, an air inlet and an air outlet of said compressor, said air inlet being positioned downstream and sufficiently close to said blades and of a size effective to remove a substantial quantity of air from the axial flow airstream in the vicinity of said blades of said wind turbine thereby significantly to improve the efficiency of said turbine, the outlet of the compressor being connected to said swivel joint, whereby air under pressure from said air compressor can be fed down said duct to the lower end thereof and a reservoir connected to said lower end of the duct, effective to receive air under pressure from said compressor, said head being allowed to swivel, so that the wind turbine can face the wind.