A system and method for improving efficiency of vertical axis wind turbines for all wind directions, comprising an inlet convergent section, a wind turbine section adjacent to exit of convergent section and an outlet divergent section. The system provides an air passage through the inlet section, the wind turbine and the outlet section, and allows for variation of the inlet and outlet depending on wind direction, in order to maximize efficiency harnessed within a time interval in accordance to wind direction and wind speed.