A solar-power aircraft theoretically capable of flying at night was unveiled by a Swiss adventurer yesterday as he announced plans to circumnavigate the globe using alternative energy.

Bertrand Piccard said that he would take science and aviation to a new frontier with the €66 million (£56 million) project revealed at a Swiss military airfield.

“Yesterday it was a dream. Today it is a plane. Tomorrow it will be an ambassador of renewable energy,” he said as he stood beside the Solar Impulse prototype, which has the wingspan of an Airbus A340, the weight of a family car and the motor power of a scooter.

The ceremony, at Dubendorf airport, was attended by 800 aviation enthusiasts, including Prince Albert of Monaco and Moritz Leuenberger, the Swiss Transport Minister.

The Solar Impluse will have its maiden flight this autumn when Mr Piccard, 51, a psychiatrist, will put six years of research into practice. The first stage will involve short flights to test the capacity of the 11,628 monocrystalline silicon cells needed to generate enough energy for the four motors, each generating 10hp, to get the Solar Impulse off the ground.

After that Mr Piccard and André Borschberg, his partner, will need to check that the lithium polymer batteries store sufficient energy to stay airborne at night and that the ultra-light, carbon-fibre honeycomb structure is as resistant as they believe.

They will also need to verify studies suggesting that the pilots — themselves, in practice — can stay alert for as long as 25 hours using a system of electrodes to detect their sleep cycles. If all goes to plan, the prototype, which has a maximum altitude of 28,000ft (8,500m) and a maximum speed of 44mph (70km/h), will be replaced by the final version of the Solar Impulse for a round-the-world flight in 2012.

Mr Piccard said that the project would make history in a field where existing solar-power aircraft are unable to stay in the air at the slightest hint of cloud. It would also demonstrate the potential of renewable energy.

“If an aircraft is able to fly day and night without fuel, propelled solely by solar energy, let no one come and claim that is impossible to do the same thing for motor vehicles, heating and air conditioning and computers,” he said. “Through this project we are proclaiming our conviction that a pioneering spirit and political vision can together change society and put an end to fossil-fuel dependency.”

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