Salient White Elephant

April 23, 2009

Airborne Wind Dam

A blimp suspends a giant flow accelerator with a small high-power turbine in the middle of it. In other words, a blimp suspends a turbine that looks kind of like the one described in this earlier post:

Wind Turbine with Flow Accelerating Shroud

This rotor will spin at high rpm, so it is easy to make it a direct drive machine. As described in prior posts, the bottom of the flow accelerator can attach to the top of a supporting tube in order that the blimp doesn’t have to carry the entire gravity load of the shroud and turbine. The tube is on wheels and a control system causes it to follow the blimp around with changing wind speed and direction.

Here’s another variation:

Airborne Wind Dam

Airborne Wind Dam with Lattice Support

Blimp With a Hole Variation

In this variation, the blimp has a cylindrical hole right through the middle of it (running down its longitudinal dimension). The small high-speed direct drive turbine rotor is inside this cylinder. A large shroud like the ones depicted above encircles the blimp in order to further accelerate flow through the cylinder and direct drive turbine rotor.

Airborne Wind Dam, Cylindrical Hole in Blimp

Skyscraper Variation

In this variation, the blimp is moored to the top of a skyscraper. When the windspeed gets too high the blimp simply detaches from the building and flies to a nearby airport where it lands until the storm passes. I hate to make the next suggestion, because somebody might actually do it. The blimp could be moored to the top of a mountain. This would produce a lot of visual pollution, so I don’t think it’s a very good idea.

Lightweight Electrical Components Variation

The blimp is big and round. It has plenty of room for a ring generator. Of course, you don’t need a ring generator to make this machine direct drive, because the accelerated flow through the cylinder is already sufficient for making the turbine rotor spin at high rpm. But if the turbine drives a very large diameter ring generator, then electricity can be generated with high voltage. If voltage is high, then current is low, and the weight of electrical components such as the electrical cables is minimized. (I’m assuming insulation weighs less than copper.)

Structural Electrical Cable Variation

This option develops electrical cable technology that is suitable both for conducting electrical power and for carrying a tensile mechanical load. This minimizes the weight of the mooring cable, since the electrical cable simultaneously provides both mechanical and electrical functions.

Aerodynamic Transmission Variation

The diagram below is a little ridiculous, but I’m a terrible artist, and I’m using 2D software to create these diagrams, so for this diagram I decided to come up with something that just shows the general idea. And the general idea is to reduce the weight of airborne components by using a light-weight hollow tube to moor the blimps. The hollow tube transmits the high air pressure that accumulates at the center of the dam (shroud) to the ground. A small high-speed turbine rotor drives a generator at the ground level end of the tube. The turbine rotor is high speed, and so it doesn’t need a gearbox. The airborne system carries no electrical or mechanical devices, and so it is light in weight.

Airborne Wind Dam With Aerodynamic Transmission

This idea suggests an interesting question – what happens to the Betz Limit when de-energized air doesn’t flow away from the turbine on the downwind side of the turbine “rotor”?

Of course, the aerodynamic transmission may also be applied to more convention turbine designs. Perhaps a shroud is positioned at the top of a conventional wind turbine tower, and the tower itself is used to route the high pressure air to a turbine rotor and generator on the ground.

Pressure Differential Aerodynamic Transmission Variation

A wall is added to the inside of the aerodynamic transmission tube. This separates the tube into two halves, just as though there were two tubes instead of one. One half of the tube opens on the high pressure side of the shroud, and the other half opens on the low pressure side. This pressure differential is carried to the ground where one side of a high-speed turbine rotor encounters the high pressure, and the other side of the rotor encounters the low pressure. Air thus flows through the rotor and turns an electric generator.

Cross-Section of Aerodynamic Transmission Tube Showing Transmission of Pressure Differential

Rotating Drive Shaft Variation

Hollow, light-weight, rotating tubes are connected end-to-end through universal joints. The tubes are attached to the mooring cable and so are suspended beneath the mooring cable. A high-speed rotor at the top transmits power to the ground through the rotating drive shaft tubes. The spins at high rpm so drive shaft torque is low.


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