Amid Switzerland’s mountainous landscape lies a hangar, enclosed by fences, where a group of pioneers is trying to change the way that we see solar power.

It is home to Solar Impulse 2, a plane that acquires all of its power from the sun.



In just two months time the team developing the plane will attempt to fly it around the world. If successful, the journey will take two intrepid explorers, Bertrand Piccard and Andre Borschberg, five months to complete as they fly between stopping points around the world.

It is a challenging task both for the technology and the pilots, but it marks a potential new high point for solar power.

Having come a long way from the early iterations of solar cars, the plane can show the world below the true potential of this renewable energy source.

It can also prove to be a benchmark for solar-powered flight, and may lead to future solar-powered planes used for passenger transport.

Sun-powered round-the-world flight

Taking to the skies in March the plane and its pilots, who will take turns flying the aircraft, will embark on a journey around the world. Abu Dhabi in the United Arab Emirates will be the starting and finishing point of the flight.

The plane, equipped with a 72m wingspan, has already been transported to the city for testing and final training of the pilots and crew.



From here it will go on its 22,000-mile journey, clocking around 500 hours of flying time. A special route has been devised and the planners have had to negotiate with airports and flight controllers to ensure the plane does not disrupt the smooth running of each country’s airspaces.

The journey is planned to consist of around ten legs, with a support team of 60 people helping the plane and its pilots to complete the mission.

For the two longest legs, across the Atlantic and Pacific oceans, each pilot will be alone for five days and nights. The only sleep that is permitted is a series of 20 minute naps, so that some energy can be restored.

“Twenty minutes is a good time as we have seen to bring back some energy, and a better functioning of the brain,” Borschberg explains.

It is crucial that the pilots are able to pay as much attention to the flight as possible due to the plane’s low flying speed.

In the event of things not going to plan, the pilots can rely on a life raft and preserver.

Building a solar plane

In preparation for its journey around the world, the plane has undergone significant improvements from the first model, which completed a 24-hour flight.

Its batteries can be fully charged with solar energy within three to four hours while it is on the ground; they will then continue to be charged during flight.

If you want to demonstrate the potential of this technology you need to fly day and night

The second iteration of the plane made its first flight in June 2014 and has been rigorously designed, manufactured and tested to increase the potential for success when it embarks on the monumental trip.

The upgraded model features a bigger cockpit, a bed and a toilet, all of which will prove essential for the longest legs of the journey. Borschberg says that from the first version to the second it was important that they could “make the pilot sustainable as well”.

Piccard, who was the first person to complete a non-stop balloon flight around the world, says that the original idea of the plane was not new, but that it is a way to highlight issues that the world needs to tackle.

“For decades the protection of the environment was expensive and boring,” he says.

“If you want to demonstrate the potential of this technology you need to fly day and night. We can say that Solar Impulse has the technology of yesterday; Solar Impulse 2 has the technology of tomorrow.”

In the run-up to the world trip, the developers are flying the plane almost every day to give the pilots and the technology as much flight experience as possible.

During the construction, development and testing of the plane they have relied on modelling and flight simulation software.

To simulate the plane’s performance they created a 3D model using Dassault Systèmes’ 3D virtual design software.

This allowed them to test out different wing span and weight arrangements, solar panel configurations and more without having to create physical prototypes.

“It gave us complete traceability and control over our plane from the design desk to the workshop where it was built,” says Jonas Schär, the head of the plane’s design team.

“This helped ensure that every bolt, plate and washer shown in the 3D model and design can be found in the actual physical plane.”

Solar flights of the future

It will remain to be seen whether the gigantic but lightweight plane and its pilots can meet the inevitable challenges that will be posed by the weather, technology and human limitations, but in attempting to do so they will be able to showcase solar power to almost the entire world.

“The problem is not technology, it is political,” Piccard explains. “Do the governments want to make a change?”

As well as flying a flag for solar power, the journey will include the longest single pilot flight to be completed – highlighting the potential for the aviation industry.

This could lead to the development of more solar planes, potentially even for passenger transport or autonomous flight.

Shortfall flights with 50 passengers could be happening within ten years, Piccard believes, adding that there are still many challenges along the way, including vigorous testing, safety, durability and also a change in attitude within the air transport industry.

Solar energy has struggled to be taken seriously as a power source for air travel, with many in the aircraft industry seeing it as more of a gimmick.

Even where solar is being explored, it is largely being treated as a source of support power.

Airbus, for example, is researching solar energy as a source of electricity once a plane is cruising, but has made no announcements to suggest it is looking to make a plane running entirely on solar power.

However, the solar industry is making remarkable gains, with improvements in the technology coming thick and fast.

To this end Borschberg said that unmanned planes, or flying objects, would be a “logical application” of the technologies that are being developed.

These applications may come in the form of solar-powered drones, such as those that Facebook has invested in.

Whatever the future of solar flight may hold, the endeavours of Solar Impulse 2 will play a large part in forming the popular opinion.

Based on the previous successes of the Solar Impulse team, the meticulous attention to detail and rigorous training completed, it would not be at all surprising if the world-wide flight proves to be successful.

All images courtesy of Solar Impulse / Revillard