Stationary co-axial multi-rotor wind turbine supported by continuous central driveshaft

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 α (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.

What is claimed is: 
     
         1 . A method of harnessing power from a fluid flow comprising:
 mounting a series of substantially horizontal-axis type rotors to an elongate driveshaft at spaced intervals;   aiming said driveshaft at an offset angle α (alpha) from the wind direction;   whereby offset angle α (alpha) is sufficiently small that said rotors are sufficiently aligned with said fluid flow to function effectively to gather power from said fluid flow, and;   said spaced intervals are sufficient to provide substantially fresh wind to each rotor;   whereby said rotors are caused by said fluid flow to rotate, causing said driveshaft to rotate, so that useful power can be drawn from said rotating driveshaft.