It doesn't make good business sense, physics sense, or much of any kind
of sense, to try to fly an airplane on solar power. Not yet. With the
state of the technology, and how relatively young the solar sector
still is, such an endeavor would be considered quixotic today—let alone
in 2003, when Bertrand Piccard and André Borschberg, co-founders of
Solar Impulse, announced they would design a solar-powered aircraft and
fly it around the world.
It would be a statement, they said, about our global dependence on
fossil fuels and the untapped promise of burgeoning green technologies.
The Swiss pilot-entrepreneurs were after "perpetual flight": a plane
that could climb to 9,000 feet and fly on the sun's energy by day, then
descend below cloud cover to lower altitudes, where it would cruise on
stored battery power by night.
It was a long shot. And yet seven years of innovation later, the
70-person Solar Impulse team is nearing its goal. "We were intrigued by
this notion of perpetual flight," said Borschberg when visited in
September in Solar Impulse’s massive hangar, situated smack in the
middle of Düendorf Airfield, a Swiss military zone. "We wanted to be
totally independent of any fuel." Forget hybrid planes, or the biofuels
fixating most of the sustainable aviation sector today; Piccard and
Borschberg are purists. "No fuel, no CO2, no pollution. It could fly
almost forever, assuming good weather," Borschberg said of their
invention.
By November of last year, test pilot Markus Scherdel—formerly of DLR
German Aerospace, the NASA of Germany—was climbing into the cockpit of
the completed prototype to taxi down the Dübendorf runway for the first
time. Soon after that, Scherde was back in the cockpit, this time
guiding the plane not just down the runway but up into the air for a
series of successful "flea-hop" mini-flights over the tarmac.
The Solar Impulse HB-SIA, as it is officially named, is a strange sight
to behold. Resting under the sky-high ceiling of its hangar at
Dubendorf, it looks fragile to the point of breakable. And no wonder:
HB-SIA, comprised of a carbon skeleton covered in a flexible
polycarbonate “skin,”� weighs only about 1.5 tons, about as much as a
small car. Its wings are so light that a single person can carry them.
And when I tested both the pilot's parachute and the detached nosepiece
of a second prototype of the plane for weight, the parachute was
heavier.
Article continues: http://www.good.is/post/powering-planes-with-the-sun/
The Chapters 
In Switzerland, two pioneers are coming closer and closer to a flight around the world powered only by solar energy.
