Solar Impulse SA of Switzerland started to test the HB-SIA, a huge airplane that uses only photovoltaic (PV) cells as its power source, in earnest March 30, 2010.
Solar Impulse prototyped the HB-SIA based on the "Solar Impulse Project," which was launched by adventurer Bertrand Piccard and others in 2003. The company plans to prototype another plane in 2011 or 2012, aiming to go on a round-the-world trip by using only solar energy.
The HB-SIA is 21.85m in length, 63.4m in wing length and 6.4m in height. The wing length is as long as those of The Boeing Company's 747 passenger airplane and Airbus SAS' A340. On the other hand, the weight of the HB-SIA is as light as 1.6t, which is equivalent to the weight of a car.
On the main wing and the horizontal tail (area: 200m2), 11,628 pieces of SunPower Corp's photovoltaic (PV) cell are mounted. The cell has a conversion efficiency of 22% and a thickness of 150μm.
Those PV cells power four electrically-driven engines with a maximum output of 7.5kW (10hp) and an average output of 6kW. The average flight speed of the HB-SIA is as low as 70km/h.
For night flight, the airplane is equipped with about 400kg of lithium polymer rechargeable battery with an energy density of about 220Wh/kg, which accounts for about 25% of the total weight.
Solar Impulse completed the first flight in December 2009. But, at that time, the HB-SIA flew only 350m at a height of 1m above the ground. This time, the airplane will fly for half an hour to check its controllability. And the company expects that it will continuously fly for 36 hours by the summer of 2010.
Furthermore, Solar Impulse is planning to make an even larger airplane, "HB-SIB," in 2011. It will have a wing length of 80m, which is longer than that of AirBus' A380. The company will try to fly across the Atlantic Ocean in 2012 and to fly around the world in 20 to 25 days in 2013. During the around-the-world tour, it plans to make stops in five places including China and Japan.