Pilots hope to fly around the world powered only by the sun

Two pioneering aviators will take off from Abu Dhabi this week, hoping to complete the first round-the-world flight using zero fuel - in a mission that will test the limits of human endurance.

André Borschberg, 62, and Bertrand Piccard, 57, will take turns at the controls of the Solar Impulse 2 as it flies 35,000km in a journey expected to take five months. That includes 12 stops, two of which are in China.

The aircraft, which is almost as large as an Airbus A380 but weighs about the same as a car, has a 72-metre wingspan, wider than a Boeing 747 jumbo jet, and a top speed of 90km/h at sea level and 140 km/h at maximum altitude.

The main aim of the mission is to promote green technology but the two men - both Swiss - also have their sights set on getting China's burgeoning solar power industry on board in their quest to take the power of the sun to new levels.

Among the 12 stops they will make are the mainland cities of Chongqing and Nanjing.

Borschberg, co-founder and chief executive of Solar Impulse, the Swiss company that developed the plane, told the Sunday Morning Post that the transpacific leg, between Nanjing and Hawaii, would be the most challenging. Over the non-stop, five-day period, the pilot will have to negotiate the hours of darkness in an aircraft powered by the sun - a first in aviation history.

"Solar Impulse is not made to carry passengers, but to carry messages," said Piccard, who comes from a family of explorers and scientists and who, in 1999 made the first ever non-stop round-the-world balloon flight.

Engineer and entrepreneur Borschberg said his love for flying was matched only by his passion for clean energy. Borschberg, who was trained by the Swiss air force, led a team of 80 technicians and engineers to build the "super-light, super-robust and energy-efficient" Solar Impulse 2, equipped with technology that theoretically gives the it unlimited endurance. It is a bigger and better version of the prototype Solar Impulse 1 that has already completed flights across Europe and the United States.

For the transpacific and transatlantic legs, the pilot may only get two to three hours sleep a day with the plane on autopilot and real-time monitoring from their ground control centre in Monaco. The two men should be well-equipped to deal with the mental stress: Borschberg has practised meditation and yoga for years, while Piccard is a psychiatrist with expertise in hypnosis.

The plane will fly at an altitude just below commercial passenger airliners during the day and descend to 1,500 metres at night to save energy.

A key aim of the mission is to highlight the fact that the technology needed to tackle today's environmental challenges is available; what's missing is the will to apply it, they say.

They also have their sights set on taking solar technology to a new level - with China's solar power players as partners.

"China is the world's largest solar energy producer, but unfortunately when we started the [Solar Impulse] project, it was a little bit too early for us to contact the Chinese companies," Borschberg said.

"For our third airplane, the next generation, we may integrate Chinese technology, and we've had discussions with Chinese companies such as Hanergy. This is absolutely possible for the future."

Borschberg envisions the Solar Impulse 3 as an unmanned solar plane that can fly at an altitude of 20,000 metres for six months without stopping.

"It can have surveillance and communication usage, basically replacing part of what satellites are doing these days, but at much cheaper costs and with much cleaner energy," he said.

China recently committed to doubling its renewable energy use from 10 per cent of its energy mix in 2013 to 20 per cent by 2030.

The country poured US$90 billion into clean energy development last year - which topped world spending for the sector. It was more than the US$52 billion the United States spent, and the US$41 billion Japan laid out, according to Bloomberg New Energy Finance. That drove global investment last year in clean energy to US$310 billion.

Public awareness and governmental commitment are key to changing the world's energy consumption patterns, he added.

Thirty years ago, exploring alternative energy became a salient issue when oil prices increased - but interest lapsed when oil prices stabilised, Borschberg said.

"I think this has changed now. For the first time it seems to me that now the growth of renewable energy has got its own momentum," he said.

"What we spend on Solar Impulse is only 4 per cent of a Formula One team", which has a budget of around US$300-400 million a year, Borschberg said. "It is not a question of cost, it is a question of change."