Abstract: Co-axial, multi-rotor wind turbines, producing more power than a single rotor of the same diameter, are made even more powerful by increasing driveshaft length and supporting the driveshaft from more than one point. Sacrificing the ability to aim, for the extra length to support additional rotors, results in a more powerful co-axial multi-rotor turbine, especially useful for areas with a predominantly unidirectional wind resource. Ideally the turbine is placed at an offset angle ? (alpha) from the wind direction, which, in combination with proper spacing between rotors, allows fresh wind to reach each rotor, so that all rotors contribute toward rotation of the driveshaft. Placing the driveshaft under tension can raise critical speeds and reduce the number of intermediate supports required. This places the Earth or underlying substrate in compression, making it effectively part of the structure of the turbine, saving cost. Cross-axis and reversible blades may also be incorporated.

Abstract: A multiplicity of horizontal axis rotors are coaxially attached, at spaced intervals, to an elongate driveshaft. This driveshaft with attached rotors is aimed, not directly into the wind, but at a slightly offset angle, allowing each rotor to encounter a wind stream having fresh wind. That offset angle may be in the vertical plane, horizontal plane, or oblique. The shaft is held with rotational freedom at or near its midsection by a cantilevered bearing means, and drives a load, such as an electrical generator. This cantilevered bearing means, along with the rotor laden driveshaft which it supports, is allowed to pivot, as an entire unit, about the vertical axis of a supporting tower. The generator, brake, support frame, as well as a dedicated counterweight can also serve as a counterweight to help elevate the downwind section of the driveshaft, by pushing downward on the upwind section of the turbine.