Swiss adventurer Dr. Bertrand Piccard has unveiled a prototype of the solar-powered plane that he hopes to eventually fly around the world. Dubbed the Solar Impluse HB-SIA, the airplane is designed to fly both day and night without the need for fuel and will begin test flights by year's end.

The prototype of the new solar-powered aircraft was unveiled at a Swiss airfield by its future pilots Piccard and André Borschberg.

Piccard, who made history in 1999 by circling the globe non-stop in the Breitling Orbiter 3 balloon, says he wants to demonstrate the potential of renewable energies.

Despite a wingspan equal to that of a Boeing 747-400 plane, the Solar Impulse, which has the look of glider, weighs only around 1.7 tons, about the same as an average car. More than 12,000 solar cells mounted on the wing supply renewable solar energy to the four 10-horsepower electric motors. During the day, the solar panels charge the plane's lithium polymer batteries, allowing it to fly at night.

According to Piccard, it took 6 years of intense work, calculations, simulations and tests by a 70-person team to complete the Solar Impulse – a project that he believes is a breakthrough design.

The airplane 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. Piccard will begin testing with short runway flights in which the plane lifts just a few feet into the air.

At a press conference at the plane's Duebendorf airfield near Zurich, Piccard made clear the goal of the aircraft is to prove the business viability and profitability 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 systems, and computers," he said.

After fine-tuning on the ground, the aircraft should make its first test flights between now and the end of 2009. A first complete night flight is programmed for 2010 and 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.

Although the vehicle is expected to be capable of flying non-stop around the globe, Piccard will in fact make five long hops, sharing flying duties with project partner Borschberg.

"The aeroplane could do it theoretically non-stop - but not the pilot," said Piccard.

"We should fly at roughly 25 knots and that would make it between 20 and 25 days to go around the world, which is too much for a pilot who has to steer the plane.

"In a balloon you can sleep, because it stays in the air even if you sleep. We believe the maximum for one pilot is five days."

The results from the HB-SIA and their analysis will serve to develop and build a second aircraft, the HB-SIB for circumnavigating the word in five stages, each lasting several days, in 2012.

"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'."

Supporters can enroll on www.solarimpulse.com to receive news in real time, to adopt a solar cell on the wing, reserve a VIP visit at the Solar Impulse base, or place their names on the aircraft's fuselage.