Salient White Elephant

April 21, 2009

VAWT Forest

Many tall slender VAWT rotors are optimally dispersed and mechanically linked to drive a single generator.

Savonius Forest

Walmart Rooftop VAWT Forest

A weather protection shroud (not shown above) runs along the same path as the chain and protects components from rain and other weather. It may also be desirable to explore the option of using a rotating drive shaft to transmit power from turbine to turbine, and finally to the generator. I won’t draw this option, because I’ve already drawn it for one of the variations below.

In the following embodiment, rotors form a wall along the four sides of the roof. A tarp that is supported by a lightweight metal frame runs along each of the four sides of the roof and beneath the rotors. The tarp minimizes turbulence.

Walmart Rooftop VAWT Wall

Variable Scale Deployment – Rotors Suspended From Tubes

This embodiment is suitable both for utility scale deployment, such as a large VAWT Forest suspended over a cornfield, as well as for small scale deployment, such as a rooftop turbine for a residence.

One Row of VAWT Forest Suspended From Tubes

In this variation, rotors are suspended from a bunch of tube segments. The tubes are connected by flexible joints that allow them to approximate the troposkein shape of a cable. Suspended VAWT rotors drive a chain that runs inside the tubes along their longitudinal dimension. A universal joint connects the turbine rotor shaft to a second shaft above the turbine rotor. The weight of the turbine rotor keeps its shaft approximately vertical. However, in high winds the lower end of the rotor shaft can swing in the downwind direction, thus regulating power output and thrust load on the supporting tubes. The yielding rotor shaft also provides a low drag profile storm wind shut down mechanism. The drive chain bears only a relatively low torque load, since tubes carry the gravity load, and since the diameter of the turbine rotor is relatively small (so that the rotor turns at relatively high rpm). Whatever the chain load, it acts to lift the row of turbines up against the force of gravity, and it also cancels some of the gravity load supported by the tubes. Only a single chain runs down one row of turbines because the return path for the chain is through the next higher level of turbines:

Path of Drive Chain, VAWT Rotors Suspended From Tubes

Rotors Suspended From Cables, Counter-Rotating Torque Tubes

VAWT Forest With Counter-Rotating Drive

VAWT Forest With Counter-Rotating Drive (Zoomed In View)

The universal joints not only allow for transferring mechanical power to a slightly different axis, they also permit the rotor to yield in response to wind gusts, and to assume a nearly horizontal orientation when the machine is shut down for storm winds. Note that if the wind direction is at a right angle to the cable, then the cable will twist in response to rotor thrust. This does not present a problem because the orientation of the torque tubes is fixed with respect to the cable, and so the torque tubes move along with the cable when it twists. The orientation of the top rotor shaft is also fixed with respect to the cable, so it rotates along with the torque tubes when the cable twists.

Reciprocating Drive

It is also possible to use a reciprocating drive for all of these machines. In this case, a tube is pushed and pulled by a crankshaft. Perhaps the simplest (and least expensive) option would have the crankshaft driving a cable. I will add some drawings of these options if I have more time later.

For more related discussion, see VAWT Wall.



  1. Just a thought – rather then the complicated gearing setup – use a bicicyle style free wheel cog (real wheel) for each rotot attached to the chain – thuse if the wheel/rotor is adding tourque – then more power to ya – and if for some reason the individual rotor is not keeping up it is not a drag to the rest.

    Comment by Tom Martin — June 28, 2009 @ 7:18 am

  2. Yes – good idea. Thanks Tom.

    Comment by Salient White Elephant — June 28, 2009 @ 7:22 am

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