Hitting new heights: the legacy of Solar Impulse

A daring round-the-world solar powered flight could lead to a revolution in the skies.

Bertrand Piccard and André Borschberg (c) Solar Impulse Foundation
Bertrand Piccard and André Borschberg. Source: Solar Impulse Foundation  

A century after the Wright brothers took to the skies, the world witnessed a daring new first for aviation. 

The record-setting craft weighed no more than a family car, with a cramped one-man cabin of just 3.8 cubic metres, and a wingspan of a whopping 72 metres – longer than that of a jumbo jet. But what really set Solar Impulse 2 apart from other aircraft was that the upper surface of its wings were covered with 17,428 solar cells, each thinner than a human hair, which enabled pilots Bertrand Piccard and André Borschberg to take in turns to circumnavigate the world – covering over 43,000 km – without using any fuel. Lithium polymer batteries stored the sun's energy to power the plane at night.

“We wanted to show that clean technologies and renewable energies can achieve so-called impossible goals,” says Piccard. “We flew around the world without a drop of fuel, in an aeroplane that could fly day and night only on solar energy. It was the first time ever, and I think it was a very powerful message.”

Both men were experienced pilots, but the Solar Impulse flight – which lasted a total of 558 hours over 17 separate stages – presented new challenges. Borschberg, who completed 8,924km in a five-day-long non-stop solo stint, did yoga positions to keep his body from stiffening up in the cramped cabin and slept in 20 minute bursts. 

solar impulse
Solar Impulse 2 (c) Solar Impulse Foundation
Source: Solar Impulse Foundation

Just the beginning

Key to the success of the Solar Impulse team was how it used existing technology in a pioneering way, reaching optimal performance with the second plane it built.

“We had to build a completely new type of aeroplane that was considered to be impossible by all the specialists. The aircraft manufacturers refused to build the plane and finally it was a ship yard who built it because they knew how to use carbon fibre so that it was light enough,” Piccard explains.

“On a personal level, what struck me the most is the perseverance we had to implement and the resilience to go through so many problems – technical, meteorological, administrative, financial, human – in order to succeed. Honestly, in the air it was easy. In the air it was fantastic, it was just moments of grace. On the ground, sometimes it was hell.” 

Of course, the amount of surface area needed for solar cells to power the plane in the air makes the Solar Impulse model impractical for commercial use under currently available technology. But the flight has shown that planes can become greener.

Borschberg believes flying taxis may become one of the first mass market users of solar energy in aviation, flying for up to 30 minutes on solar batteries charged on the ground. Piccard reckons it won’t be long before such technology is extended to full-sized passenger planes too.

“In 20 years’ time, I think you will have short and medium haul that will be electric, and you will have long haul that will be sub-orbital,” Piccard says. Charging on the ground “makes the plane perfectly operational for short to medium haul. It will be silent, it can land at night without disturbing the neighbours and it is safer, because an electric engine is much simpler to use than a combustion engine.”

The Solar Impulse team is now using the attention generated by their record-breaking flight to turn the spotlight onto their new project: a portfolio of 1,000 innovative solutions to protect the environment, which they will be presenting to governments and businesses around the world to continue proving that what seems impossible can, in fact, be achieved.

Projects include desalinating water with solar energy, making biodegradable plastic from waste milk proteins and a small, easy-to-install box capable of slashing fuel use and emissions for existing cars. Some of the technology used for the Solar Impulse flight will also live on in other forms – work is afoot, for example, to adapt the insulation foam from the cockpit door for refrigeration units. 

“For us, the project is really just starting. The round the world flight was the first major goal. We want to get across the message about the potential of clean tech – to show that we already have the technology to be much more energy efficient. Now we are bringing together projects in clean tech to show the political world that there are lots of opportunities,” says Borschberg.

Crucially, as well as being designed to benefit the environment, the ideas need to be financially viable.

“It will never work as a charity with the amount of change that we have to bring. So it has to be a (business) opportunity as well.”