Five years after landing in Abu Dhabi, ‘Solar Impulse’ team are still flying high

Electric plane’s audacious round-the-world trip from UAE capital smashed preconceptions about the limits of renewable energy

'Solar Impulse 2' flies past the Sheikh Zayed Grand Mosque in Abu Dhabi. The solar-powered aircraft began and ended its 2015-2016 circumnavigation of the world in the UAE's capital.

'Solar Impulse 2' lands in Cairo on July 13, 2016. From there it took off on its final, 48-hour leg to Abu Dhabi.

'Solar Impulse 2' approaches Hawaii after a record-setting flight across the Pacific. It left Nagoya in Japan on June 28, 2015, arriving at Kalaeloa, Hawaii almost 118 hours later.

Swiss pilot Bertrand Piccard, left, and alternate pilot Andre Borschberg, right, pose with crew members in front of 'Solar Impulse 2' after landing at at Tulsa, Oklahoma, in the US, on May 13, 2016.

Bertrand Piccard takes a selfie over the eastern US on May 25, 2016. 'Solar Impulse 2' arrived in Lehigh Valley, Pennsylvania, from Dayton, Ohio, after more than 16 hours.

Support crew members attend to of 'Solar Impulse 2' before it takes off from Mandalay, Myanmar on March 29, 2015.

'Solar Impulse 2' flies over Abu Dhabi's Reem Island during a test flight.

Bertrand Piccard and Andre Borschberg divided piloting duties over the 17 legs of the single-seat aircraft's circumnavigation of the globe.

Sheikh Zayed Grand Mosque in Abu Dhabi provides a spectacular backdrop to an early morning test flight before 'Solar Impulse 2' embarked on its round-the-world attempt on March 9, 2015.

Ground crew prepare the 'Solar Impulse 2' for take-off. Its wingspan of almost 72 metres is only slightly less than that of an Airbus A380, the world's largest airliner.

Spectators gather for the maiden flight of 'Solar Impulse 2' in Payerne, Switzerland, on June 2, 2014.

'Solar Impulse 2' was the second aircraft of the Solar Impulse project, devised with the aim of circumnavigating the world with a solar-powered aircraft.

Ground crew push the 'Solar Impulse 2' back into its hangar after its maiden flight in Payerne, Switzerland, on June 2, 2014. In comparison to its size, the aircraft weighs a modest 2.3 tonnes.

'Solar Impulse 2' is the successor to the 'Solar Impulse' prototype that flew across the US in 2013 without using a drop of fuel.

'Solar Impulse 2' approaches Abu Dhabi's Al Bateen Executive Airport, before touching down to complete its circumnavigation of the globe, on July 26, 2016.

The Gulf has become a well-known testing ground for some of the world's most advanced sustainable technologies.

'Solar Impulse 2' sits on the tarmac at Abu Dhabi's Al Bateen Executive Airport in the early hours of July 26, 2016, after completing its round-the-world flight.

'Solar Impulse 2' approaches to land in Abu Dhabi. It covered almost 42,440 kilometers in its journey round the world.

'Solar Impulse 2' prepares to land in Hawaii on July 3, 2015, after flying non-stop from Nagoya, Japan. It covered the distance of more than 8,920 kilometres in just under 118 hours.

'Solar Impulse' was the prototype for 'Solar Power 2'.

'Solar Impulse 2' flies over San Francisco towards the end of leg 9. It left Hawaii on April 21, 2016, flying for more than 4,000 kilometres in 62 hours to California.

'Solar Impulse 2' during its first test flight in Abu Dhabi, on February 26, 2015, after being reassembled following delivery to the city.

'Solar Impulse 2' lands at Mountain View, California after leaving Hawaii more than 62 hours earlier on April 21, 2016.

Bertrand Piccard, left, and Andre Borschberg address a crowd after 'Solar Impulse 2' landed at Mountain View, California on April 23, 2016.

Andre Borschberg, who piloted 'Solar Impulse 2' on eight of the 17 legs of the round-the-world flight.

'Solar Impulse 2' passes over the Gemasolar thermosolar plant in Seville province, Spain, on its way to Cairo. The aircraft left Seville on July 11, 2016 for the flight of more than 48 hours.

'Solar Impulse 2' is pictured from above next to a huge Emirati flag, at Al Bateen Executive Airport, after completing its record-breaking trip early on July 26, 2016.

Solar Impulse 2 prepares to land Abu Dhabi early on July 26, 2016 and become the first solar-powered piloted aircraft to circumnavigate the Earth.

'Solar Impulse 2' flying over the Red Sea. The aircraft could reach an altitude of 12,000 metres and had a cruising speed of 90 kilometres an hour.

The dismantled 'Solar Impulse 2' is pictured before being loaded into a Cargolux Boeing 747 cargo aircraft. Cargolux carried the aircraft from Switzerland to Abu Dhabi, where it was reassembled for its globe-spanning journey.

'Solar Impulse 2' proves a popular attraction at Sardar Vallabhbhai Patel International Airport in Ahmedabad, India, during a stopover in mid-March 2015.

'Solar Impulse 2' on a test flight over Abu Dhabi on February 26, 2015.

Ground crew prepare the cockpit of 'Solar Impulse 2' in Switzerland. On multi-day legs of its round-the-world journey, the pilot would take 20-minute naps while the aircraft was on autopilot.

A dramatic view of 'Solar Impulse 2' after leaving New York, bound for Seville, Spain, on June 20, 2016.

'Solar Impulse 2' flies over the Statue of Liberty in New York shortly before landing at John F Kennedy International Airport on June 11, 2016. The 265-kilometre flight from Lehigh Valley International Airport in Pennsylvania took four hours 40 minutes.

'Solar Impulse 2' after landing in Spain, after crossing the Atlantic in a 6,765-kilometre flight that took more than 71 hours.

During its record-breaking circumnavigation of the globe in 17 stages, over 16 and a half months, 'Solar Impulse 2' flew for 558 hours, at an average speed of 41 kilometers an hour and covered 42,438 kilometres.

The sun had yet to rise over Abu Dhabi when a giant aircraft, silent as a moth, settled gently on the runway at Al Bateen Executive Airport and into the history books.

Monday marks five years since Solar Impulse 2, powered by sunlight and with wings longer than a Boeing 747, completed its 42,000-kilometre voyage around the world.

Piloted by Bertrand Piccard, 63, and entrepreneur Andre Borschberg, 68, the flight was completed without any fuel beyond the sun’s rays, using four electric motors powered by more than 17,000 solar cells.

Despite its 72-metre wingspan, the aircraft weighed no more than a Toyota Land Cruiser.

With a pressurised cabin, it could reach an altitude of 8,500 metres but generally cruised at 1,800 metres.

On a full charge, it could fly throughout the night.

Solar Impulse 2 left Abu Dhabi on March 9, 2015, on its way around the world. It spent about 23 days in the air, travelling at an average speed of about 70 kilometres an hour.

When Mr Borschberg landed the aircraft in Kalaeloa, Hawaii, on July 3, 2015, it was discovered that the batteries had overheated during the flight from Japan. The rest of the journey was postponed until the following year.

The circumnavigation was not without challenges, including turbulence caused by the hot desert air as the plane made the final approach to the UAE capital on July 26.

It was several months behind schedule, delayed by bad weather in China and Japan and battery repairs in Hawaii.

By then it had already broken several records, including the longest solar-powered flight by time and distance at 117 hours 52 minutes and 7,212 kilometres.

After landing at Abu Dhabi, Mr Piccard predicted electric passenger aircraft would fly within 10 years.

What then seemed an impossible dream is now edging towards reality.

Several short-haul commuter aircraft are being developed, including projects by Boeing and Airbus, the world’s largest aircraft manufacturers.

Mr Piccard and Mr Borschberg founded the Solar Impulse Foundation in 2003. It aims to find 1,000 solutions to environmental problems using non-polluting energy.

Its aviation company, H55, was launched in 2017.

This month, Mr Piccard and Mr Borschberg marked the anniversary by taking to the air in a very different aircraft, but one also powered by electricity.

The Bristell Energic is a single-engine battery-powered flight trainer. Built by H55, it could become one of the first commercial electric planes.

It was the first time the men had flown an electric aircraft together. Their combined weight would have been too much for Solar Impulse 2, which they piloted in turn.

“It was so good to be back in electric flight mode with my old partner,” Mr Piccard said on Twitter.

That alone illustrates the technological leap since their global flight five years ago. Other alternatives to fossil fuels include hydrogen fuel, which emits only water vapour.

Mr Piccard said his latest aircraft was “the perfect proof that clean and efficient technologies allow us to do so much better for the environment and all fields of the industry”.

“This low-carbon flight reminded me how great it is to fly without noise," he said.