by Timothy B. Lee, washingtonpost.com -- July 15 2013
An airplane has flown across the United States, powered only by sunlight. The impressive feat was made possible by improvements in solar cell and battery technology. This chart, produced by the Department of Energy, shows how solar technology has improved:
[see story link for DoE Chart]
Because the flight across the United States took more than 24 hours (specifically, about 2 months), the plane needed to collect energy during the day and then use it at night. It used lightweight lithium polymer batteries to do this. The Solar Impulse team says the “total efficiency of the propulsion train” -- counting power lost by the solar cells, the batteries and other components -- was about 12 percent.
Solar-powered airplanes won’t replace traditional airplanes any time soon. [...] But the flight across the United States was an impressive feat of engineering. [...]
For some photos of the solar plane:
www.mnn.com -- Jul 15 2013