Imagine a plane that can fly round the world day and night with zero fuel, zero emissions - and powered by just solar energy. With skyrocketing jet fuel prices, that's not a pipe dream anymore - but a real vision that adventurer Dr Bertrand Piccard hopes to turn into reality by 2011.

It may just be a prototype now. But this dream of a plane - the Solar Impulse - developed by Dr Piccard's team, should go on its first test flight by 2009.

And by 2011, the team hopes to build a second plane that will travel around the world, day and night.

However, when the sun goes down, what happens to this plane that depends on solar energy to stay in flight?

Piccard said: "On solar energy, you have to capture the energy with solar cells on the wings, store this energy in the batteries and at the same time, run the engine during the day."

"So when you get the dark, you can use the energy from the batteries until the next sunrise, and continue the next day and next night and next day again," he added.

Batteries are expected to last at least 16 hours after dark. But to fly without fuel, obtaining the right aerodynamics was tough.

However, that dream is now a reality with a cool US$70 million tag - of which 65 per cent of the financing has been obtained.

And with a man who has gone round the world non-stop in a hot air balloon, an adventure like this at the frontiers of aviation should be no barrier.

With an aviation industry vision of zero carbons emissions in 50 years, we could be travelling on a 300-passenger plane powered solely by clean energy in the future.