Salient White Elephant

April 23, 2009

Blimp VAWT

Since no people will ride in the blimp, I guess it could be filled with hydrogen.

Blimp VAWT

I’m always drawing 2 bladed VAWTs when I really mean 3. A three bladed VAWT produces relatively constant power, and more importantly in this case, thrust. Since wind speed will normally increase with altitude, blade radius increases with altitude so as to maintain a more constant tip speed ratio. For simplicity, I drew only 2 guy wires. In reality, at least three would be required.

The turbine’s rotational axis can tilt, and the gearbox and generator tilt along with the rotor axis. This allows the wind turbine to seek its optimum orientation given wind speed and other parameters. Alternatively, perhaps the lower end of the wind turbine (the generator) is on wheels and is able to move if the turbine wants to move. Since the structure will be very heavy, the control system would likely control the movement of the generator this way and that along the ground as wind conditions change. But if we let the lower end of the turbine move, then we may as well save some weight by using only one guy wire or lattice to moor the blimp. In this case, the turbine will “yaw” by roughly tracing out a circle about the guy wire anchor point as the wind direction sweeps through a 360 degree arc.

The teardrop streamlined shape of the blimp is critical. If any old shape is used for the floatation device, then the wind will tend to carry it downstream. I don’t know what the optimum aerodynamic profile would be, but you would want to minimize drag. For this reason, perhaps a very elongated shape (kind of like a cigar) might be used.

Kites and Airfoils

Additional lift may be generated if a kite is positioned on top of the blimp. Imagine, for example, those modern parachutes that look like a big airfoil made out of something like nylon. If one of these is mounted on a vertical pole that extends upward from the blimp, then it will “take flight” when the wind speed reaches a sufficient value. In this case it will be available to add further support for the turbine whenever the turbine is running and producing power. Some kind of inflatable airfoil might do the same trick. If a kite or modern parachute is used, it will be suspended by its supporting structure in a shape and orientation that “prepares it” for taking flight when the wind picks up.

Other Variations

I think there must be many ways to develop better configurations if more than one blimp is employed. For example, two blimps could be moored to a giant circular railroad track. The anchor points are “yawed” so that a line connecting them forms a right angle with wind direction. The blimps are connected by a cable, and multiple VAWT turbines are suspended from the cable that connects the two blimps.

Weight is obviously one of the primary issues with airborne turbines. Perhaps some sort of inflatable airfoils can be used. The airfoils may even themselves be filled with hydrogen. Or a design similar to those light-weight modern parachutes might be used for the blades.

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