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Keep on watching the skies

Wind turbines are on the up. The giant constructions are constantly getting taller because, as every schoolboy knows, the higher you get off the ground, the greater the wind speeds. But building big towers is a costly business, especially if you want one 15,000ft tall. So why not ditch the tower and make the windmill fly? PES investigates one possible future for energy generation…

It may sound crazy but several developers are now in the process of trying to achieve just the scenario above. There are three main leaders on the field – Sky Windpower, Laddermill, and Magenn. Some of the ideas are currently at the R&D, drawing board stage, while others are working prototypes – but they all deserve a look. What’s more it seems obvious that once someone creates a workable system, it will become a huge winner, because of the sheer amount of power available up there in our skies.

Just one per cent of the jetstream’s wind power could, amazingly, supply all US electrical demand. Also, one of the ongoing major complaints about wind power is its intermittency – that darned pesky wind out there stoically refuses to blow all the time, and so, according to the Sky Windpower project, most wind farms are only operating at their peak capacity between 19 and 35 per cent of the time. The wind is much steadier at altitude, however, so you get even more advantage over ground-based wind power. A final advantage is ad-hoc generation: devices with a reasonably simple tether system do not have to be permanently installed in one place. Instead they can be trucked out to any location which needs them.

Sky Windpower is probably the furthest along the road, with functional prototypes tested in the field. Bryan Roberts, an Australian mechanical engineering professor, teamed up with some Americans to commercialize his Flying Electric Generator idea – a windmill tethered to the ground but flying like a helicopter in the jetstream, at 15,000 to 35,000 feet altitude. According to their figures, one flying windmill rated at 240kW with rotor diameters of 35 feet could generate power for less than two cents per kilowatt hour.


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