Apparatus for extracting power from fluid flow

1. An apparatus for extracting power comprising:

a track comprising first and second elongate sections, wherein the first elongate section is positioned above the second elongate section;

an airfoil comprising a suction surface and a pressure surface, wherein the airfoil is coupled to the track so that the pressure surface lies between the suction surface and the track, and wherein the airfoil is moveable in opposite directions when alternately coupled to the first elongate section and second elongate section;

a bridle coupled at a first end to the first elongate section and at a second end to an anchor, wherein the bridles is angled at γ degrees to a horizon and the airfoil is rolled at approximately 90−γ degrees to the horizon when coupled to the first elongate section; and

a power generator to harvest power from an atmospheric wind through the movement of the airfoil.

2. The apparatus of claim 1 , further comprising at least three bridles coupled to the first elongate section.

3. The apparatus of claim 1 , wherein the airfoil has a first roll to a horizon when the airfoil is coupled to the first elongate section and a second roll to the horizon when the airfoil is coupled to the second elongate section, and wherein the first roll is different from the second roll.

4. The apparatus of claim 1 , wherein the track further comprises a terminal connecting the first and second elongate sections, wherein the airfoil decelerates when the airfoil transitions from the first elongate section to the terminal, and wherein the airfoil accelerates when the airfoil transitions from the terminal to the second elongate section.

5. The apparatus of claim 1 , wherein the track further comprises a terminal connecting the first and second elongate sections, wherein the airfoil yaws as it travels along the terminal.

6. A method of extracting power comprising:

providing a track comprising a first elongate section and a second elongate section lower than the first elongate section;

coupling an airframe to the track, wherein the airframe comprises a suction surface and a pressure surface, wherein the airframe is coupled to the track so that the pressure surface lies between the suction surface and the track;

positioning the track so that the airframe travels crosswind to an atmospheric wind;

attaching a bridle to the first elongate section;

anchoring the bridle, wherein the bridle is angled at γ degrees to a horizon;

rolling the airframe at approximately 90−γ degrees to the horizon when coupled to the first elongate section; and

harvesting power from the atmospheric wind through the movement of the airframe.

7. The method of claim 6 , further comprising attaching at least three bridles to the first elongate section.

8. The method of claim 6 , further comprising rolling the airframe at a first angle to a horizon when the airframe is coupled to the first elongate section and rolling the airframe at a second angle to the horizon when the airframe is coupled to the second elongate section, and wherein the first angle is different from the second angle.

9. The method of claim 6 , further comprising coupling a terminal between the first and second elongate sections, wherein the airframe decelerates when the airframe transitions from the first elongate section to the terminal, and wherein the airframe accelerates when the airframe transitions from the terminal to the second elongate section.

10. The method of claim 6 , further comprising coupling a terminal between the first and second elongate sections and yawing the airframe as it travels along the terminal.