FAQ



Where does the idea of the Solar Impulse come from?
Bertrand Piccard came up with this idea following Orbiter 3. This successful world tour in 1999 conveyed a great deal of enthusiasm. It is precisely this enthusiasm that must be mobilized to make people aware of the challenge of the 21st century: reconcile economic and ecologic interests. Promoting the use of new technologies not only to give credibility to sources of alternative forms of energy but also to show that we must spare today's resources.


Which are the concrete objectives of this operation?
To show what can be achieved using renewable energies and encourage their use. We want a strong symbol capable of striking the minds. In this respect, Solar Impulse will be our ambassador. The message we want to share is that it is essential to develop new technologies to allow our society to reduce its energetic consumption. As it is almost unthinkable that people will accept to diminish their life standards, we must develop efficient equipments that consume less, as well as alternative sources of energy and first of all solar energy.


Why is the wingspan of the plane so important?
Firstly, a longer wingspan allows the improvement of its aerodynamic efficiency by reducing the importance of induced drag. This produces a weaker airplane sink-rate and thus reduces the power of the motors required to maintain it in a horizontal position. The second advantage of a large wingspan is the benefit from a greater surface on which to place the solar cells.


What area still limits the plane's performance?
It is above all, the energetic density of the batteries. Their stocking capacity is still limited and their influence has a great bearing on the total mass of the airplane. By doubling their storage capacity, it would be possible to allow a second person on board and therefore carry out longer flights.


What will happen in case of a breakdown? In other words, what are the risks for the pilot?
If the pilot wastes his energy during the night, he will have to interrupt the flight before the next sunrise. But isn't it also the case of our generation running the risk of not being able to hand down the planet to future generations without a major human and technological disaster? The pilot will be equipped with a parachute, but our world doesn't have any such protection to face the climate change! In other words, the greatest risk is not flying on board of the Solar Impulse, but keeping on wasting our world's energy and raw materials!


What is the output of solar cells?
The output of the cells reserved for the project is about 20%. Two criteria are used for this selection: the output, but also the weight. The cells chosen are made of silicon mono-crystalline of a fine thickness. Today there exist more high-performance technologies with up to 30% output, but they are also heavy. It is obvious that a significant improvement of this output would also improve the airplane's performance and reduce its wingspan or increase the payload.


What does photovoltaic mean?
Cells are photovoltaic, when they directly transform the photons (light) into electricity. But there are thermal solar panels that allow water to be heated either for houses or for producing the steam used to turn the turbines that generate electricity.


Why not a world tour without stopovers?
For the time being this is not feasible because even if we are able to reach "perpetual flight" there will be a human limitation. The plane's cockpit is very small and can only accommodate one pilot. He won't be able to physically endure these conditions more than 4 to 5 days. The world tour without stopovers could be made possible as soon as 2 pilots can embark. One must know that it took was 60 years between the first world tour with stopovers and the first world tour without stopovers in a traditional motor airplane...


What technological developments can we expect after the completion of the world tour?
It's difficult to say, but we can already expect multiple developments in fields of weight and energy saving, in components efficiency, in the greater reliability of electrical engines, in a better output of solar cells, energy storage or improvements of cabin pressurisation systems. But we will first have to develop know-how before communicating the technologies.


Can solar energy replace oil?
Solar energy alone cannot. The future energy supply will certainly be based on a large diversification of sources: solar, but also wind, hydroelectric, tidal and, geothermic. Until this goal has been reached, there will still be an important demand for oil, coal and nuclear power.


Why is the cause of sustainable development progressing so slowly, when the risks of pollution and climate change are undeniable?
Because protecting the environment too often still remains associated with a restriction of mobility and financial sacrifice. The economic benefits offered by a true policy of sustainable development must be shown, including new products, new prospects, new sectors offering jobs, market share and profitability.


Do you think it would be possible to replace conventional airlines with solar ones in the near future?
Currently, technology only allows the transport of a single person on a flight of 24 hours, and then with a wingspan of 60 to 80 meters. But if we go back into history, when the great Wright brothers got their first plane to fly a distance of 200 meters in 1903, could they have imagined that 66 years later, two men would walk on the moon?