We may be on the verge of an age in which small, unmanned aerial systems, better known as drones, fill the sky -- powered only by the sun. From the Economist:
Eventually...the civilian use of small drones may well exceed that of military ones. They can survey pipelines and power cables, perform aerial filming for anyone from television news stations to estate agents, monitor fires, assist in search-and-rescue operations and help carry out research. Aviation regulators are now forming rules that would allow far greater civilian use of such systems.
For many of these missions long flight times would be important, and solar power can help with that. It also means not having to transport fuel or carry recharging equipment. With electrically powered small drones the limitation is the battery. This means the flight time of some small craft like the Raven is limited to around 90 minutes. So the race is on to find ways to fly for a lot longer.
We saw the civilian use of drones in action when they were deployed to help fight the Yosemite Rim Fire. According to the Economist, new, less expensive, lightweight yet robust solar panels are expected to hit the market soon, and engineers are taking advantage of that. Some people developing the crafts say they'll be able to last in the air for days, or even weeks, at a time, relying on a small backup battery for dark or cloudy situations. And there's no need to get paranoid, but the planes' life span, they predict, could be practically limitless.