People powered might just as well be the description of this nifty solar plane, as the 12,000 solar cells are all sponsored to the tune of $200 each.
Finn Olaf-Jones reports for the Wall Street Journal:
…In 2003, [Bertand] Piccard approached European companies to sponsor what has become a $148 million project and began assembling a team of 80 engineers and technicians plucked largely from Swiss universities. After seven years of tinkering, they arrived at a machine with a deceptively simple design: Solar Impulse—with its sleek, clean lines, white-gloss finish and rakishly angled 208-foot wings (bent to increase the plane’s stability)—resembles what you might get had Steve Jobs reimagined a child’s balsa-wood glider in giant form.
“The crux to flying nonstop around the world with solar energy is being able to fly even when the sun isn’t out, especially at night,” notes André Borschberg, a former Swiss air force fighter ace and McKinsey & Company consultant who, as the project’s CEO, oversees the design team and takes turns piloting the plane. The solution: Four specially developed lithium polymer batteries that store energy from the nearly 12,000 solar cells lining the horizontal stabilizer and the wings (cells that are supported by individual sponsorships at around $200 each—even former Vice President Al Gore bought one). During the daytime, the batteries accumulate energy while the plane climbs to a height of up to 30,000 feet. After sunset, the plane slowly glides to lower altitudes on the stored power until dawn, when the process starts again.
The most revolutionary aspect of the plane’s design are the materials used to minimize its weight. Every unneeded ounce had to be discarded so that the machine could bear the payload of even a single pilot. “We did a feasibility study and discovered that we weren’t going to be able to get down to the right weight with any available construction materials,” remembers Borschberg. “When we talked to aeronautics companies to see if they could develop this, everyone said it was impossible. So we turned to a boat-building company.”
The company—Decision SA boatyards, which specializes in racing ships out of Ecublens, Switzerland—created rectangular carbon-fiber beams, honeycombed to lighten the plane’s internal structure. Over this skeleton they pulled a specially developed carbon skin half the weight of copy machine paper. “You can actually tear the plane’s skin apart with your hands,” says Piccard. “It’s funny something so strong on a grand scale is so delicate up close.” Though Solar Impulse is as wide as a Boeing 747, it weighs a mere 3,500 pounds—about as much as a family sedan. But unlike a car, Solar Impulse can be disassembled into 10 pieces and packed into a plane’s hull for shipment anywhere in the world…