Patent ID: 8522435

Claim:
A method of making a turbine configured to rotate about an axis of rotation, the method comprising: extruding a blade portion with a foil cross-section extending along a longitudinal axis of the blade portion; twisting the blade portion about the longitudinal axis by a first angle as the blade portion is extruded; repeating the steps of extruding and twisting the blade portion for a plurality of blade portions; and forming one or more elliptical blades from the plurality of blade portions, each of the plurality of elliptical blades having a pair of distal ends, wherein each of the one or more elliptical blades has an elliptical shape that is approximated by a plurality of substantially straight portions extending between one or more central locations of that elliptical blade, and wherein the one or more central locations of each elliptical blade is configured to be disposed at a same distance from the axis of rotation as the distal ends of each elliptical blade when that elliptical blade is disposed at a second angle with respect to the axis of rotation.