Solar Impulse : round the world without a single drop of fuel

by Raphaelle Nicolet

Flying… humans have always been obsessed with flying. Icarus, Leonardo Da Vinci, the Mongolfier Brothers, the Wright Brothers and many others have paved the path to aviation as we know it today. It is now an integral part of our every day lives. However, human kind is now facing a huge challenge: starting to respect its mother, the one who is providing it with everything it needs to survive: water, food, air. The earth is under serious threat and it is time to save it. This ambitious goal is attainable, but adaptation and innovation are highly needed. Amongst the changes that will have to be done, one is fundamental: the switch to clean technologies. The good news is that it is not impossible! This was Solar Impulse’s goal to show it to the world. Our motto was: Future is clean and we were determined to prove it.

two pioneers

But what is exactly Solar Impulse ?

It is an ambitious project, developed in Switzerland by two pioneers and their team, Bertrand Piccard and André Borschberg. Bertrand Piccard a Swiss psychiatrist and balloonist who comes from a famous family of adventurers. Flashback to March 1999, together with Brian Jones he completed a non-stop tour of the globe in a balloon called Breitling Orbiter 3. Encouraged by his success and concerned about the need to raise environmental awareness the journey of Solar Impulse began. Bertrand Piccard was joined 4 years later by André Borschberg, an aviation lover. Former pilot in the Swiss Air Army, helicopter pilot, engineer in mechanics and thermodynamics. Enthusiastic about the project he began to develop it alongside Bertrand Piccard.


Fast forward to 2009, the year that saw the first plane driven by solar energy born and named Solar Impulse 1, HB-SIA. This plane flew to various countries, namely Belgium, France, Spain, Morocco and the United States. The duration of the flights performed by HB-SIA was between 14 and 22 hours. If you want to see this plane, it has been bought by Solvay, one of the main and faithful sponsors and is on show at La Cité des Sciences et de l’Industrie in Paris.Five years after its first success, in 2014, the second plane arrived, Solar Impulse 2, HB-SIB. Unlike its predecessor this one had been built for nothing less than performing the first round the world without using a single drop of fuel. This crazy and exclusive experience would start in Abu Dhabi at the beginning of 2015.

A few impressive technical facts

Before going any further, I would like to give you a few impressive technical facts regarding Solar Impulse. First of all, its wingspan is 72 metres (236 feet) and only the pilot fits in the cockpit, with no space for a passenger. By contrast, think about a big Boeing 747. This plane is impressively big and can carry up to 660 passengers. But, its wingspan is still ‘only’… 68 metres (224 feet). If you compare the two planes, you realise how impressive Solar Impulse’s wingspan is. It’s shape looks pretty much like a glider. Beside its size, HB-SIB was also incredibly light. Think a minute about the pickups we see everywhere here in Thailand. Their weight is around 2080kg (4576lbs). Now, guess the weight of the solar plane… you won’t believe it, but it was only 2300kg (5060lbs)! The carbon fibre used to build it is incredibly light and yet very strong. The cruising speed is quite slow – it doesn’t fly faster than 50-100km/h (30mph to 60mph, 25 KIAS-35 KIAS). Solar Impulse may not be fast but, it is important to remember that it represents a major technological advancement, that has yet to be improved. Like every invention, it starts with the emergence of technology that will evolve and become more efficient with time. In order to generate enough power to fly, Solar Impulse uses no less than 17,248 solar cells spread on the wings and fuselage.

Operating mode


So how does this revolutionary plane work in simple terms? Solar energy works non-stop through the following process. As the solar energy feeds through the cells it is then distributed to the batteries via an inverter thus producing power to charge the engines. All of this, without even using a single drop of fuel! Solar Impulse 2 was flying up to the maximum altitude of 8,500-9,000 metres (27,887-29,527 feet). As the plane gained altitude, it used the energy driven directly from the solar cells while at the same time storing energy in the batteries.  The motors were then turned off and the plane would glide, going down to 1,500 metres (4,921 feet). During this 4 hour stage, no energy was used. Finally, the motors were turned on again using the energy stored during the day. At the first sign of daylight the process would start all over again. The first time I saw this beautiful bird flying, I was surprised at its silence. We are not used to seeing silent planes. This was something completely foreign to me yet it amazed me at the same time.

The round the world

Now that you know a little more about the technical characteristics of the plane, allow me to move on to round the world trip itself. The journey started in Abu Dhabi. The entire team was about to face a huge challenge of never, before seen events and we had to be ready. Flight tests, training on the mobile hangar, used to store the plane daily, solar charges, everything had to be executed to ensure the odds were on our side. As you can imagine, the logistics on the project were immense and nothing was left to chance. For example, as HB-SIB was so huge, we didn’t have hangars big enough all around the world to store the plane. Therefore, we had a special mobile hangar, developed by an Italian company in the balloon field, to protect the plane. Erecting it took us around 8 hours, dismantling it, around 12 hours. We would monitor it 24/7 to ensure it did not deflate and was well secured, in the event of strong winds.

We were aware of the highly unpredictable nature of our crazy project. But it didn’t deter us and the team was highly determined to make it happen.March 9, 2015, the adventure began. Everybody was excited. It was a mixed bag of emotions, happiness, excitement, apprehension, haziness, but above all, the feeling of being part of a historical moment was overpowering any fears we had. The first leg led us to Muscat (Oman) before taking us to Ahmedabad (India), Varanasi (India), Mandalay (Myanmar), Chongqing (China), Nanjing (China), Nagoya (Japan) and Oahu, Hawaii (USA). Unfortunately, the batteries had been damaged during the very long flight between Japan and Hawaii.


Can you imagine André Borschberg flew for 5 days and 5 nights, exactly 117 hours 52 minutes to cross the Pacific and reach Hawaii? This is actually a solo flight world record. As the batteries couldn’t be used in its state, the adventure had to be put on a hold after this epic flight. It wasn’t easy to replace the batteries of an exclusive prototype like Solar Impulse, therefore some time was needed to replace them. As the days got shorter, the sunshine was not sufficient to circumnavigate round the world. For this reason the plane stayed grounded in Hawaii and the second part of the journey round the world started again on April 21, 2016. The plane then flew to San Francisco, Phoenix, Tulsa, Dayton, Lehigh Valley, New York, Seville, Cairo and finally made it back to Abu Dhabi on July 24, 2016.

This adventure was amazing in so many ways. Being a pioneer, having the chance to inspire people all around the world was a privilege. We faced challenges because of the weather, the regulations, the distrust of the unknown, but it was all worth it. Seeing this shy teenager in Abu Dhabi asking the pilots if they were thinking about recruiting female pilots for solar planes, seeing more than 15,000 people in one day queueing to have the chance to see this incredible plane, seeing a future pilot in China with sparkles in his eyes, asking questions, seeing with an indescribable emotion Solar Impulse 2 appearing in the sky of Hawaii after leaving it five days earlier in Japan, all of these moments – amongst others – were worth all the doubts and challenges we had to face.

And now?


Even if today we are far from a solar aviation, the goal of Solar Impulse was to show the world that incredible things can be achieved with clean technology that it is definitely the future. This plane was built not to carry people, but to carry an important message and raise awareness about the resources available to live an eco friendly lifestyle. Global warming is not a fatality. Solar Impulse legacy led to great new concepts, like the company H55* which just released on June 21, 2019 a two-seater ‘zero emission’ electric airplane. The Solar Impulse Foundation** also keeps on spreading the message by selecting 1,000 solutions with the goal of protecting the environment in a profitable way. These projects are awarded the Solar Impulse Efficient Solution Label. Beside this label, the World Alliance for Efficient Solutions was set up. But what is the goal pursued by this Alliance? It brings together actors who are protecting the environment in a profitable way. They can act through developing, financing or promoting clean products, processes, services and technologies. For now, there are 1,849 members of the World Alliance all around the World and 177 projects have been already awarded.

What about you?


Saving our planet is our duty, all of us. Together, we can make a difference. Don’t minimise your impact. If you bring your own cup and straw to coffee shops, don’t see it as a drop in the ocean. If you have one coffee a day, at the end of the week, you will have saved at least 5 cups and 5 straws. If 20 people do it, this is aa 100 units a week. Besides cups and straws, plastic bags are a real cancer to the environment. Can you imagine that the ASEAN countries represent just 9% of the world population, but are responsible for half of the 8 millions tons of plastic discharged into the ocean every year (Ocean Conservancy’s report, 2017)! Therefore, if you stop using plastic bags, it will have a huge impact on the planet. After all, all it takes to help the earth is carrying a really light reusable bag with you: insignificant effort for a big result. You can make a difference by making small changes in your daily life. Unsubscribe from newsletters you never read, empty your junk mail. You may ask me why? To store all this data, we need gigantic servers, cooled down by enormous AC installations. You get my point I guess: less data, less energy spent.

June 23, 2019, in Bangkok, the ASEAN member countries signed an advancing partnership for sustainability. Although no concrete measures have been put in place it is a first step towards the right direction but more still needs to be done. But it is not nearly enough. If the population doesn’t raise awareness about global warming now and doesn’t show willingness to change its habits, political agreements will struggle to reach their goal. For the sake of the planet, please consider following the path of Solar Impulse and all the people actively working on saving mother earth. There are many opportunities to keep our comfort, wealth and money, even improve them by changing paradigm, believing and investing in clean technology! If we have been able to complete a round the world tour with a solar energy driven plane, you too can have a big impact. We have only one earth, let’s work together to take care of it and not leave only a carbon footprint for future generations!

LinkedIn : Raphaëlle Nicolet          Email : [email protected]

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