French President Nicolas Sarkozy and EADS CEO Louis Gallois were among the dignitaries visiting the Solar Impulse display at the recent Paris Air Show in what amounted to a promotional stop for the Swiss maker of the HB-SIA sun-powered airplane.
In addition to promoting new technologies and renewable energy, the company said its Paris Air Show participation—which included presentations and a demonstration flight during the event as well as arrival and departure flights involving airports in Switzerland, Belgium, and France—helped it gain knowledge about slotting the aircraft into international airspace and landing at international airports.
“The feedback from our European flight campaign is encouraging,” said Bertrand Piccard, Solar Impulse Founder and President. “The welcome we received from political and industrial circles in Brussels and Paris shows that Solar Impulse is pioneering a new way of thinking in terms of renewable energy and energy saving.”
Solar Impulse plans to fly a second airplane (the one in use now is the first prototype) around the world. That flight, slated for 2014, will be done in five stages, each lasting several days. Engineers are working on the new model.
The current prototype has 11,628 monocrystalline silicon solar cells, 10,748 of which are attached atop the wing and another 880 atop the horizontal stabilizer. The 150-µm-thick cells were selected for their lightness, flexibility, and output (22% efficiency) and cover a total of 200 m².
The electricity they derive from sunlight is stored in advanced lithium-polymer batteries. Housed in the four engine nacelles, the batteries have an energy density of 240 w·h/kg and a total mass of 400 kg—a quarter of the aircraft’s total. Energy storage is described by the company as the “major constraint in the project.”
Each nacelle also houses a battery management system (for temperature and charge control) and a 10-hp motor for propulsion. Thermal insulation has been designed to conserve the heat radiated by the batteries to keep them functioning in the low temperatures at altitude. Fitted is a reduction gear that keeps the speed of the twin-blade propeller (3.5 m in diameter) between 200 and 400 rpm.
Even with a wingspan of 63.4 m (equal to that of an A340) and a length of 21.85 m, the plane weighs only 1600 kg. The plane is built of composite materials consisting of a carbon-fiber-honeycomb sandwich structure. The wing has 120 ribs placed 50 cm apart.
Take-off speed is 44 km/h, and average flying speed is 70 km/h. Maximum cruising altitude is 8500 m.
The aircraft on July 7-8, 2010, recorded three world records for solar-powered flight: duration (26 h, 10 min, 19 s); absolute altitude (9235 m); and gain of height (8744 m).
About 70 engineers and technicians are employed by Solar Impulse, which is based in Lausanne. Major suppliers/partners include Solvay, Omega, and Schindler.
The project began in 2003 and was founded by Piccard, who with Brian Jones in 1999 became the first to achieve an around-the-world balloon flight.