A Suggested Design Modification to Present,
Blimp-Supported Wind Power Systems
G.R.Dixon, September 24, 2008
I saw a very interesting thing on TV a few days ago. It told about experiments with a barrel-shaped blimp equipped with fins. The idea was that the blimp would rise up to where the airflow is more laminar (and often stronger), and would then spin as the wind blew against its anemometer-like fins. The spin axis was horizontal and linked to one or two generators whose housing was kept from rotating by being attached to a fork-like gimbal. Fig. 1 illustrates.
Schematic of Blimp Spinner
The device met with only very limited success, and my impression at the programís conclusion was that the inventors were going back to the drawing board to try to brainstorm why the thing didnít work better, and to make the necessary design changes.
I donít remember hearing them mention gyroscopic effects as a possible contributing factor to the deviceís failure to perform. I am writing this article to suggest a possible way around this problem, as well as to propose that the spin axis of the wind rotor be made vertical rather than horizontal.
To begin with, I am inclined to believe that the function of the blimp should be strictly to carry and hold the generator assembly aloft, and that the wind-harnessing rotor should be made out of rigid but super light material. The gyroscopic effects would be effectively canceled out by having two rotors, designed to counter-rotate in the breeze. Both would be mounted on a rigid axle. The generators on the ends of the two rotors would serve as counterpoises to one another. Fig. 2 depicts the suggested configuration.
Proposed, Counter-rotating Wind Rotor Generation System
The depicted "wind jenny" would spin regardless of which direction the wind was blowing. There would be no gyroscopic effects, owing to the counter-rotating rotors and their attached generators. The housing of both generators would be welded together so that only the internal parts counter-rotated. The wind rotors would be linked to the generator internal (spinning) parts. The tether to the ground would again include a conductor so that generated electric power could be transferred to ground-based facilities. The tether would be long enough to allow the entire apparatus to be lifted to a region of laminar airflow (perhaps one or a few hundred meters).
I believe that these devices would be considerably cheaper to build and maintain than conventional windmills. While their efficiency might be less, they should require minimal maintenance once sent aloft. The generators can be AC, thereby reducing the gauge of conducting wire required between ground and generators. The footprint of any one device would be minimal and not subject to the shear stresses of conventional mills. (The generator/blimp would move laterally and closer to the ground in the wind until equilibrium is reached.) Hopefully these devices will provide a quick and cost-effective means of exploiting that resource.