An apparatus and method for extracting power from a moving fluid, such as the wind. In an illustrative embodiment, the invention is a vertical axis wind turbine with variable-pitch wings, each turned directly by a servomotor under the control of an on-board computer. The computer is continuously updated from onboard transducers which measure wind direction, wind speed, rotor assembly position and rotor assembly speed and calculates each wing's optimum angle of attack at all times and under all conditions. This angle is then sent as a command to each wing's servomotor and the computer executes the control loop again.