Solar Impulse project is a four-engine high-wing ultralight aircraft, made in Switzerland, at the Federal Polytechnic of Lausanne. Primary characteristic is the ability to hover without fuel because solar powered.

The promoters of the project are Bertrand Piccard , André Borschberg , Luigino Torrigiani and Brian Jones. The first aircraft, officially known as HB-SIA, was a single-seater capable of taking off with its own strengths and designed to sustain flight with its own forces for a period of 36 hours.

Between 7 and 8 July 2010, the aircraft proved to be capable of flying for 24 hours, staying in the air during the night due to the accumulated charge during the day. On 13 May 2011 he was the protagonist of a journey that lasted 13 hours from Payerne to Brussels.

It ‘s the time now for HB- SIB, the official name of Solar Impulse 2, a bit  larger than the first . On the basis of the experience of its predecessor, HB- SIB should be able to circumnavigate the globe in 20-25 days.
It has a wingspan of about 72 meters , almost as much as that of a Boeing 747 . The plane works thanks to 17.248 monocrystalline silicon photovoltaic cells placed on the wings, so wide in order not to affect the aerodynamics and simultaneously allow the insertion of many solar panels. This solution represents the best compromise between lightness, efficiency and flexibility.

The stored energy is fed to 4 electric motors of 17.5 hp. To ensure that the aircraft maintains its charge even at night, during the day the solar cells transfer energy in 633 Kg lithium batteries  ( one-fourth of the total weight of the aircraft ), covered by a foam very dense that contributes to their isolation. Equipped with a control system of charge and temperature, these batteries are usually put into the engines of the plane. So conceived , the HB- SIB can travel at the same speed of a car, between 36 Km/h and 140 Km/h.

The first test flight was carried out in June 2, 2014. Swiss plane took off from Payerne in Switzerland and landed shortly after 2 hours and 17 minutes of flight.
Solar Impulse 2 incorporates new technologies to be more efficient, reliable and, in particular, more suitable for long-haul flights. It ‘s the first plane will have a virtually unlimited endurance. “In the course of such an innovative project, every step is a leap into the unknown. Today, the suspense was at its peak. The results show that our engineering team can be very proud of the work done over the past 10 years” said  Bertrand Piccard.

The highest altitude during the flight was 1.670 meters and the average speed (soil) of just over 55 Km/h. The world tour will be accomplished in stages. The aircraft will be able to fly for 5-6 consecutive days and the drivers take turns.