Tomorrow morning at a military airport near Zurich, two Swiss adventurers will reveal a prototype for a solar-powered aircraft they hope will be the first to fly around the globe in 2011.

The £42m Solar Impulse is one of the most ambitious aviation projects of recent times and could revolutionise air travel.

Instead of using conventional aircraft fuel it will have ultra-thin solar cells integrated into the wings, which will be used to collect sunlight and convert it into energy to power the four electric motors. By storing energy the plane will be able to fly at night.

When the final version is built, the plane will measure about 262ft from wing tip to wing tip, giving it a similar wingspan to that of the new A380 superjumbo, which made its maiden flight last month.

But that’s where the similarity ends – while the superjumbo can carry more than 800 passengers and has a top speed of more than 560mph, the Solar Impulse will have room for just one person in its small cockpit, and will reach only about 40mph, at which speed a round-the-world flight will take about four weeks.

The project represents potentially the biggest landmark in aviation in the past three decades. In the early years of flight, records fell thick and fast. In 1927 Charles Lindbergh became the first person to make a solo nonstop flight across the Atlantic.

Chuck Yeager broke the sound barrier in 1947. In the past 30 years, though, the pace of advancement in aviation has slowed. By following the footsteps of the early pioneers, André Borschberg and Bertrand Piccard, the plane’s two pilots, hope to push the envelope once more.

The project will be an endurance feat – pilots will fly in shifts lasting five days, then land and swap over. The voyage will also be fraught with danger.

In order to fly during the night, the plane will soak up sunlight during the day and store it in onboard batteries. However, there is a real risk the batteries will empty before sunrise. The sun will be high enough for only seven or eight hours a day to provide sufficient power to drive the aircraft and charge the batteries.

If there are too many clouds the plane will not get enough energy. To counter this, Solar Impulse will be flying at altitudes of up to 42,000ft, which is above the clouds even in tropical regions, and is some 10,000ft higher than a normal cruising flight. The flight will be followed closely by meteorologists who will advise the pilot on where to fly for the sunniest conditions and minimum turbulence.

Then there is the threat of engine failure, which applies to any long-distance flight, and that of strong turbulence. Because the plane will be made from carbon fibre and is designed to be as light as possible, it will not be able to withstand jetstreams, which are fast-moving “rivers” of air in the lower atmosphere.

Unlike conventional aircraft, which can use these streams to propel themselves faster, the Solar Impulse could be smashed by them.

Borschberg and Piccard will be working in cramped conditions. Apart from the pilot, the tiny cockpit will be crammed with avionic instruments, computers and spacecraft-style vacuum-packed food.

However, these are all conditions that one of the team has experienced before. Piccard is a seasoned adventurer who already has one circumnavigation record to his name. In 1999 he captained the Breitling Orbiter 3, which pipped Sir Richard Branson’s efforts to become the first balloon to circle the world.

He is also the scion of a famous Swiss record-setting family. His grandfather Auguste set an altitude record of 51,000ft in a balloon in 1931 and his father Jacques reached a record 35,800ft under the sea in 1960.

In order to get the most sunlight, the plane will fly along the equator. Alongside a mission team of about 50 weathermen, air traffic controllers and simulation engineers supervising the attempt from Switzerland, a support crew and a portable hangar will follow and assist the plane on the ground.

Before the full flight goes ahead, the two Swiss intend to test their prototype in 2009. This smaller model has a wingspan of 197ft and is designed to fly for only 36 hours. It will not be pressurised and will be restricted to an altitude of 27,000ft, with the pilot having an oxygen pack. Heat will be retained by clothing and revolutionary insulation.

In these times of raised eco-awareness, the Solar Impulse suggests a potential future of guilt-free flying. However, the sun-powered passenger plane could be a long time coming. Driven by a trillion-dollar mobile phone market, battery technology has advanced impressively in the past 25 years. A phone that once needed a briefcase-sized battery now gets better service from something smaller than a matchbox. But things haven’t come far enough for Solar Impulse.

At the moment, solar panel and battery technology is barely efficient enough to propel the 1½ton Solar Impulse, let alone a 400-ton jumbo jet.

“We must presume a number of technical improvements in the field of solar cells and batteries before we can make the round-the-world flight,” says Borschberg. “At the moment, it could not be done, but in 2011 we will do it.” Sun-powered flight is not new – Paul MacCready, who died in August, built the Solar Challenger, which flew 163 miles from Paris to Canterbury as long ago as 1981, and American pilot Eric Raymond flew his home-built solar aircraft across America in 21 hops in 1990. However, it is the scope and ambition of this expedition that sets it apart.

The Solar Impulse project states its aims in impressive language that make great play of words such as environment, symbolic, planet and humanity, but unlike many “visionary” schemes that are long on poetic witter and short on practicality, Solar Impulse is soundly rooted in science and engineering.

It is also well fixed for cash, and has raised 65% of its target budget, largely from companies such as Deutsche Bank that are keen to be associated with environmental projects at a time when it’s bad business policy not to be.

The project may also go some way to begin the rehabilitation of aviation, which has become the focus of global warming hysteria.

Borschberg quotes Winston Churchill’s aphorism, “Civil aviation is the greatest instrument ever forged for international solidarity”, and adds: “We must continue to bring people together, and to do so we must find sustainable means. Solar Impulse is designed to show what can be achieved when energy-saving is taken to the absolute limit, but that’s not to say solar power will not play a part in future air transport.

“Few could have thought when mankind first flew in 1903 that 50 years later aircraft carrying 200 people would be crossing oceans at 500mph. Who knows what we will be doing in 20 or 50 years’ time?”