Abstract: A wind turbine generator assembly comprising an enclosure forming an air pathway; one or more wind turbines within the enclosure air pathway for generating power from air flow through the air pathway; a powered induction fan located at the upstream end of the enclosure air pathway for directing and accelerating ambient air flow into the enclosure and along the air pathway; and a powered vacuum fan located within the air pathway downstream from at least one wind turbine, the vacuum fan operating to create a negative pressure downstream from the wind turbine to increase air flow across the wind turbine and increase the efficiency of power generation by the wind turbines. In some embodiments, the air pathway within the enclosure forms a straight path with no turns and has a substantially constant cross-section between the location of the induction fan and the vacuum fan.