Abstract: An Archimedean screw turbine generator of increased efficiency is disclosed. Rather than having the helical flighting of the turbine perpendicular to the central torque tube, this design incorporates cupped or cambered flighting. This increases the turbine's overall efficiency, as well as its efficiency across a broad range of fluid flows. The improved Archimedean screw turbine produces efficient power from about 5 percent of design flow to about 110 percent of design flow. In addition, design flow efficiency is 9-10 percent better than existing Archimedean screw generators. Prior art turbines of the Archimedean screw type operate efficiently only near design-rated flows. Most are turned off if flows drop more than 30 percent below deign-rated flow figures. For a presently-preferred embodiment of the invention, the screw axially rotates within a close-fitting half pipe. A three-phase permanent-magnet AC servo motor is used as a generator.