Electrical flying with Solar Impulse

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Electrical flying with Solar Impulse

La Cinyc

Beneath you can find a photo gallery of the prototype of solar flight.

Solar Impulse (official name HB-SIA) is a long-range solar plane project currently under study at the EPFL. The project is promoted by Bertrand Piccard, and aims at completely solar-powered circumnavigation.

The first aircraft is intended to be a one-seater, capable of taking off autonomously, and to remain airborne for days. Once the efficiency of the batteries makes it possible to reduce the weight, a two-seater is planned to make circumnavigation possible.

Proposed timeline

  • 2003: Feasibility study at the École Polytechnique Fédérale de Lausanne.
  • 2004-2005: Development of the concept.
  • 2006: Simulation of long-haul flights.
  • 2006-2007: prototype.
  • 2008-2009: prototype test flights
  • 2009-2010: construction of the final plane
  • 2011: several-day-missions, crossing the Atlantic and trials circumnavigating the globe in five stages

Take-off is proposed for May 2011, for a flight around the world near the equator, but essentially in the northern hemisphere. Five stops are planned to change pilots. Each leg will last three to four days, limited by the physiology of the human pilot.

The wingspan of Solar Impulse will be 80 metres, slightly wider than the wingspan of an Airbus A380, in order to minimise drag and offer a maximum surface for solar cells. Such light wing loading (8 kg/m²) creates greater sensitivity to turbulence.


The Solar Impulse weighs 1600 kg. To keep the structure ultra-light, customised carbon fibres are used. While traditional sandwich composites have an area density in the order of 10 kg/m², those developed for Solar Impulse should weigh in the order of 0.5 kg/m². These materials could also have functionality integrated, such as integrity sensors, active control of the form, etc. A layer of ultra-thin solar cells will be integrated to the wings, which are designed to be flexible enough to withstand deformations and vibrations.


Photovoltaic cells, with a total surface of 200 m², will generate electricity during the day, which will serve both to propel the plane and to recharge the batteries to allow flight at night. Energy accumulated during the day will be stored in lithium batteries in the wings, the density of which must be close to 200 Wh/kg, in spite of temperatures ranging from +80 C to –60 C.
The average power provided to the engines will be on the order of 9 kilowatts (12 hp), comparable to that of the Wright Flyer.


The cockpit will provide pressurisation, oxygen and various environmental support to the pilot to allow a cruise altitude of 12,000 metres.


The project is partially financed by private companies such as Solvay, Omega SA, Deutsche Bank, Altran and Swisscom. The EPFL, the European Space Agency (ESA) and Dassault provide technical expertise.

First flight

On 26 June 2009, the Solar Impulse was first presented to the public, in Dübendorf, Switzerland. The first testflight is planned for late summer 2009. A second version is planned by 2011. The fact that this is a two-seater makes circumnavigation possbible. At a top speed of 90 km/h, that should take between 20 and 25 days.

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source:: solarimpulse.com
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