Bryan Roberts of Australia has a benign vision of a giant windmill in the sky . . .
Like a circle in a spiral
Like a wheel within a wheel
Never ending or beginning
On an ever-spinning reel.
In concert, these windmills could comprise one great aeronautical power station, and would generate hundreds of megawatts of electricity, doing no harm to anyone. He calls them gyromills.
His ambition is to harness the latent energy of the strong westerly winds that surge around our planet several miles above the surface. These are more stable, more dependable, than any winds elsewhere, and contain perhaps 100 times more power than those available to conventional windmills on your average hilltop. Typical wind speeds are 40 to 50 m.p.h., but 100 m.p.h. or more is not uncommon several kilometres above the ground.
Roberts's concept combines the aerodynamic qualities of a helicopter and a kite. Each would comprise a skeletal aircraft-like fuselage with a rotor on each "wing", the rotors acting like unpowered helicopters to ride the wind and provide sufficient lift to keep the whole ensemble in the air. And in addition to providing lift, each rotor, whose blades would be comparable in size to those of a conventional helicopter, would generate about five megawatts of electricity.
To stop the generators from simply flying away, each gyromill would be tethered to the ground, and the tethers would contain internal cables by which the generated power could be downloaded and fed into the national grid. Roberts seeks backing for a prototype fleet of 10 such gyromills hovering some four or five kilometres over New South Wales, and providing a combined output equivalent to that of a medium-sized power station.
The proposal has numerous advantages. There would be no noise pollution, a perennial problem with conventional windmills, and the visual impact would be restricted to a number of tiny specks high up in the sky.
The machines would not need to be as robust as ordinary windmills, since turbulence at these altitudes is minimal and they could in any event ride the gusts by simply ascending and descending like a kite, rather than standing rigidly against the wind. For maintenance purposes, the craft would simply be reeled in, and then launched again by feeding in some power to allow the generators to act in reverse as helicopter motors.
And there, far above our heads, those gyromills would stay and feed us energy . . .
Spinning silently in space
Like the circles that you find
In the windmills of your mind.