The Solar Impulse HB-SIA plane is powered entirely by solar energy and does not contain conventional engines or the mechanisms for using standard fuel. The airplane uses four 10 horsepower electrical engines powered by almost 12,000 solar cells found primarily on the 64 meter long wings. The plane uses 145 micron monocrystalline silicon cells to convert about 12% of the available light into electricity. While higher efficiency cells are available, they are considerably heavier and thus any advantage would be offset by the extra power needed to move more weight through the air.
The plane made its first test flight solely during the daylight hours in April, 2010 as a preliminary to night flight. The night flight test took off from Payerne, Switzerland at 6:51 am on July 7 and remained airborne until 9:00 am the next day. Piloted by company CEO André Borschberg, the flight reached 8,564 meters above sea level with a maximum speed of 68 knots and an average speed of 23 knots.
There are still several more tests planned for the Solar Impulse HB-SIA leading up to the construction of a second plane designed for two pilots and flights of several days or longer. The plan is to fly this second plane, the Solar Impulse HB-SIB, completely around the globe sometime in late 2012 or early 2013.
TFOT has previously reported on other environmentally friendly aircraft designs including an for NASA that significantly lowers fuel consumption and emissions, manned tests of a hydrogen powered Boeing airplane, Air New Zealand’s tests of a jetliner running on biofuel without any modifications to the plane or its engines, and tests of a solar powered unmanned aerial vehicle.