Solar powered aircraft: A flight of fancy?

Solar Impulse 2: Reaching new heights
Solar Impulse 2: Reaching new heights   

From the Wright brothers to Amelia Earhart, the history of aviation is rich in pioneers who dared to dream and push boundaries. Earlier this week two more innovators – Bertrand Piccard and André Borschberg – set off from Abu Dhabi on a journey that could change the way we think about flying forever.

Their aim? To fly around the world aboard Solar Impulse 2 (Si2), a single-seater plane whose only source of power is from the sun.

Made out of carbon fiber, the Si2 has a 72 meter wing span and weighs just over two tons. A staggering 17,000 solar cells cover its wings, supplying four electric motors.

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During sunlight hours, the plane's solar cells recharge 633 kilogram lithium batteries which, according to the Solar Impulse website, "allow the aircraft to fly at night and therefore to have virtually unlimited autonomy."

"Solar impulse is using only the sun as a source of energy," CEO, co-founder and pilot Borschberg told CNBC's Sustainable Energy. "We can fly day and night, in fact we can fly a week, we can fly months, non-stop… [it's] the first time we have an aeroplane which has unlimited endurance."

On Tuesday, Piccard, the Solar Impulse Chairman, took over the controls as the Si2 took off from Muscat, in Oman, on the second leg of the journey. It took Piccard a little over 15 hours to complete the journey to Ahmedabad, India.

If completed, the trip will be seen as a feat of endurance and technological innovation. It could also help transform attitudes to the use of renewables.

"Very often people believe that renewable energies, and energy efficiency… [are] a step backward, instead of a step forward," Piccard said. "What we want to demonstrate with Solar Impulse is that you can achieve absolutely impossible things with renewable energies, like flying an aeroplane around the world with no fuel."

Jean Revillard | Getty Images

Due to complete its 20,000 mile round the world trip in late July or early August, the Si2 will have to cross both the Atlantic and Pacific Oceans on its route.

"Some of the flights, like the Pacific and the Atlantic, will be five days and five nights in a row, non-stop, with a single pilot on board," Piccard said. "So it's also going to be a really challenging human adventure."

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If the Si2 is successful in its 'mission', it will show the world the potential of solar flight.

For Borschberg, the trip also has a deep, personal significance. "It's not so much the question of how fast we go to the destination, it's how to get [to] it… in some ways it's almost a spiritual experience."