Picard, who made history by circling the globe non-stop in a balloon in 1999, said he wants to demonstrate the potential of renewable energies.

Picard's Solar Impulse team has invested tremendous energy in trying to find what they believe is a breakthrough design.

Image: A team member works on the photovoltaic cells.
Photographs: Courtesy solarimpulse.com

"I love this type of vision where you set the goal and then you try to find a way to reach it, because this is challenging," he told BBC News.

Called the HB-SIA, the solar plane has the look of a glider, but is on the scale -- in terms of its width -- of a modern airliner.

Image: Andre Borschberg and Bertrand Piccard during the 2008 virtual flight
Photographs: Courtesy solarimpulse.com

The aeroplane incorporates composite materials to keep it extremely light and uses super-efficient solar cells, batteries, motors and propellers to get it through the dark hours.

Picard will begin testing with short runway flights in which the plane lifts just a few metres into the air.

Image: The wings are delivered
Photographs: Courtesy solarimpulse.com

As confidence in the machine develops, the team will move to a day-night circle. This has never been done before in a piloted solar-powered plane.

HB-SIA should be succeeded by HB-SIB. It is likely to be bigger, and will incorporate a pressurized capsule and better avionics.

Image: The gondola test
Photographs: Courtesy solarimpulse.com

It is probable that Picard will follow a route around the world in this aeroplane close to the path he took in the record-breaking Breitling Orbiter 3 balloon -- going from the United Arab Emirates, to China, to Hawaii, across the southern US, southern Europe, and back to the UAE.

Image: The Solar Impulse plane
Photographs: Courtesy solarimpulse.com

Although the vehicle is expected to be capable of flying non-stop around the globe, Picard will in fact make five long hops, sharing flying duties with project partner Andre Borschberg
Image: The Solar Impulse plane
Photographs: Courtesy solarimpulse.com

"The real success for Solar Impulse would be to have enough millions of people following the project, being enthusiastic about it, and saying, 'if they managed to do it around the world with renewable energies and energy savings, then we should be able to do it in our daily life,'" said Picard.

Image: The Solar Impulse plane
Photographs: Courtesy solarimpulse.com