A helical turbine is operatively connected to at least one generator system for generating electrical power. System performance is optimized by controlling the operative angle between the longitudinal axis of the turbine and the direction of the current flow and by controlling a pitch ratio of the turbine. A pair of turbines, arranged in V-shape, each at the operative angle from a neutral centerline, provides symmetry and counteracts reactive torque. For wind operations, the V-shape is freely rotatable into the wind. For bi-directional tidal operations, the V-shape is part of a buoyant structure, positioned in the current and anchored to the floor. The structure is fit with control surfaces to ensure the system orientation. In unidirectional currents, one or more turbines can be angled downwardly into the current at the operative angle, elevators ensuring the angle is maintained.