Flying Windmills
If like me you grew up reading Jules Verne, H.G. Wells and Robert Heinlein, then you can't help but love an idea like this. Instead of all those wind turbines cluttering up the landscape, why not put them up in the sky? It may sound like science fiction, but a scientist in Australia is developing Flying Electric Generators (FEGs), as reported by Wired.

The basic premise is similar to that for space solar power. If you want to get the most output from your hardware for tapping a natural energy flow, be it wind or sunlight, then you must place it where the flow is strongest. In the case of wind, that means going to the middle atmosphere, or troposphere.

It's not hard to imagine the objections to this approach. Aside from the visual impact, it's unlikely that the best places for setting up the FEGs will turn out to be entirely uninhabited. Really simple and reassuring safety backups (giant parachutes?) will be essential, because it is far too easy to imagine these things falling out of the sky.

In any case, a company has been established to exploit this idea, though they appear to be having trouble raising capital for it. As the article suggests, though, this is exactly the kind of thing we ought to be considering, because of its enormous energy potential and the absence of harmful emissions or byproducts. And if it seems a bit too much like science fiction, consider how much of today's world would seem like science fiction to someone from the 1950s--even if we still don't have flying cars.