Solar Impulse

The plane of tomorrow?

By David Bouscarrat

 David Bouscarrat, PhD candidate in the field of Mechanic of materials at Polytechnique School of Montreal.

David Bouscarrat, PhD candidate in the field of Mechanic of materials at Polytechnique School of Montreal.

Solar Impulse is a long-range experimental solar-powered aircraft project that is fed by the dream to achieve the first circumnavigation of the Earth by plane using no fuel but only solar power. 

What is Solar Impulse? 

This project is led by André Borschberg (Swiss engineer and entrepreneur) and Bertrand Piccard (Swiss psychiatrist and aeronaut), and is driven by the will to demonstrate that green technologies and renewable energies can achieve the impossible and could change the way of thinking of society. Solar Impulse has a long story. Indeed the Solar Impulse project was initiated in November 2003 after a feasibility study in partnership with the Ecole Polytechnique Fédérale de Lausanne. By 2009, they had achieved the construction of the first prototype (Solar Impulse 1) thanks to a multi-disciplinary team. A second prototype (Solar Impulse 2) was completed in 2014 and is carrying more solar cells, among other improvements. In March 2015, achieved a circumnavigation of the globe began with the last prototype.  In May 2016 their final flight in the United States: the flyover of the Statue of Liberty and a landing at JFK in New York, where Bertrand Piccard was getting ready for the Atlantic Crossing. 

Imagine energy reserves increasing during flight! To make this dream a reality, we had to make maximum use of every single watt supplied by the sun, and store it in our batteries. We tracked down every possible source of energy efficiency. Today, Solar Impulse is the first solar airplane flying through night and day, the first aircraft to come close to perpetual flight.
— André Borschberg

Solar Impulse in a nutshell: 
12 years of study, concept, design and construction
50 engineers and technicians
80 technological partners
100 advisers and suppliers
1 prototype: Solar Impulse 1
1 final airplane: Solar Impulse 2

What are the main technical challenges which made this possible? 

Solar cells: about 17’000 solar cells (monocrystalline silicon cells) on the fuselage, wings, and tailplane, providing a good compromise between lightness, flexibility and efficiency (23%).

Batteries: the energy collected by the solar cells is stored in lithium polymer batteries allowing the plane to fly day and night without a drop of fuel. These batteries are insulated by high-density foam. In order to be efficient in term of use of energy, the aircraft climbs to 8’500 m during the day and descents to 1,500 m at night. 

Lightness: in the end, Solar Impulse weighs 2 300kg (as much as small van!) including the batteries on board and a cockpit large enough for the pilot. There is a lot of innovation in the field of sheets of carbon, which are lighter and lighter.

Robustness: Solar Impulse is made of composite materials: carbon fiber and honeycomb sandwich. The lower surface of the wings is covered by a high-strength, flexible skin. Furthermore carbon-fiber ribs maintain the rigidity of the wings.

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