Salient White Elephant

March 27, 2009

Direct Drive Linear Turbine With Yawing Oblong Track

Direct Drive Linear Turbine With Yawing Oblong Track

Direct Drive Linear Turbine With Yawing Oblong Track, Close Up View of Blade to Blade Guide Interface

Although the direct drive apparatus isn’t shown in the diagrams, a written explanation should suffice. Permanent magnets are attached to the blade supporting structure that is at each end of the airfoils. The airfoils drive these magnets at a speed that is analogous to the “tip speed” of a more traditional wind turbine. Generator windings are built into the blade guides (aqua colored components in diagram above). Instead of embedding windings into the entire length of the blade guides, windings are separated somewhat. Blades speed up slightly while traversing the distance between windings.

Direct Drive Linear Turbine With Yawing Oblong Track, Aerial View

The blade inverting sections of the track permit the use of asymmetrical, pitched airfoils. (Asymmetrical, pitched airfoils deliver better aerodynamic performance than zero-pitch, symmetrical airfoils. For an explanation of the “helical airfoil inverting section” of the track, see my earlier post: 20 Megawatt Direct Drive Darrieus.)

I wonder if the blade guides can be flexible? If so, the flexibility may provide a number of benefits. For one thing a flexible guide might be cheaper, lighter in weight, and easier to build. For another, it may help to absorb abruptly changing loads due to (for example) wind gusts. It might be interesting to explore the possibility of a blade guide which is flexible enough to resemble, to a degree, a hanging cable, and yet which is still rigid enough to accurately maintain the tight mechanical tolerances that would be required for the direct drive generator components contained within it:

Can Blade Guides Be Flexible?

Two Hanging Cables Variation

Airfoil Suspended Between Two Cables (Drive System Omitted)

(If you haven’t yet read about why you might want to invert the blade, click here.)

Airfoil Suspended Between Two Cables

Close Up of Drive System for Airfoil Suspended Between Two Cables

It might be interesting to explore how the Eye of the Cat Rotor Blades would perform when hanging from two cables. Although there’s no centrifugal forces to balance, remember that the Cat’s Eye Rotor also balances aerodynamic forces. In this case, think about what happens if the blades are longer than the separation distance of the cables (including slack… so that they tend to keep the cables pushed apart).

Single Hanging Cable Variation

In this variation, sensors detect when two airfoils get too close to each other. In this case, the direct drive generator coils for the leading airfoil are switched off until it reaches an acceptable distance from the airfoil immediately behind it.

View Looking Down Structural Cable Cable Hanging Between Towers

View Looking Down Structural Cable, Moving and Stationary Parts, Cable Hanging Between Towers

View Looking Down Structural Cable, Big Picture, Cable Hanging Between Towers

Downwind View, Airfoil Entering Helical Blade Inverter

Aerial View, Airfoil Entering Helical Blade Inverter

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