Salient White Elephant

March 27, 2009

Wind Turbine With Flow Accelerating Shroud

Everyone knows that a smaller wind turbine rotor may be used if a shroud accelerates flow in its direction. Most people who know much about the design of utility scale wind turbines don’t take this idea seriously, and I confess I never took it seriously either. It just seems like an idea that cannot be applied to a large wind machine. But here are some ideas for light-weight shrouds that can be easily retracted during storm wind conditions:

Wind Turbine With Flow Accelerating Shroud

The idea is to provide a shroud that is made from some flexible material (nylon or whatever… I don’t know anything about materials). The shroud is shaped like a giant cone with its large end opening in the downwind direction (colored aqua in the diagram). But the cone is flexible… how will it be supported? It is supported by attaching its large opening to the small opening of another conically shaped shroud (colored purple in the diagram). The large end of the purple shroud opens in the upwind direction. The two upwind openings of these shrouds are each supported by a rigid ring – sort of like bending a couple of giant coat hangers into circles:

Downwind View Wind Turbine With Flow Accelerating Shroud

In order to help the shrouds hold their proper shapes, some kind of minimally designed light-weight rigid supports may be added:

light-weight ribs may be sewn into fabric of shroud to help maintain proper shape

Now we get to the second big problem with shrouds – their terrible storm wind drag profile. But since the shrouds are nothing but flexible fabric, they can easily be designed to fold into a shape that has a low drag profile! In fact, if the shrouds were well designed, it seems like maybe this machine would have even a much improved storm wind drag profile as compared with a traditional design with the same rated power output.

Giant Spoked Annular Wheel Variation

Here’s an interesting variation on this idea. This shroud sits on the ground or on a small post with bearings for yawing:

Wind Turbine With Spoked Annular Shroud, Downwind View

One interesting feature of this idea is that it makes use of all of the energy in the wind all the way down to the ground!

Wind Turbine With Spoked Annular Shroud, Side View

The following diagram shows how the shroud looks like a doughnut sliced in half (the doughnut slice and the cross section slice are in different planes):

Cross Section of Side View of Fabric Part of Shroud

The next diagram shows how the shroud may be deployed or retracted much like opening and closing drapes:

Wind Turbine With Spoked Flow Accelerating Shroud, Deploying the Shroud

Partial Cross Section of How Shroud is Deployed or Retracted Like Opening and Closing Drapes

Of course, another way to reduce the storm wind drag profile is to just lay the whole turbine down on the ground. Can’t get a much better drag profile than that!

Linear Turbine Variation

Here’s a variation that resembles the Direct Drive Linear Turbine With Yawing Oblong Track:

Shrouded Linear Turbine With Elongated Oblong Track


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