We often hear about hybrid cars, which run in part on electricity and can travel about 20 kilometers on a liter of fuel. Engineers are also experimenting with another mode of electric transportation - airplanes.
Experimental aircraft took to the skies over California recently for the 2011 Green Flight Challenge, a contest that prized fuel efficiency.
The event's sponsor, the Comparative Aircraft Flight Efficiency Foundation, required eligible aircraft to fly 322 kilometers in less than two hours, while using less than 3.75 liters of fuel per passenger or the equivalent in electricity.
Fourteen teams registered, and judges ruled that three qualified to compete.
Team Pipistrel-USA.com of Pennsylvania took home the grand prize, and $1.35 million, for its electric-powered craft, the Taurus G4. The four-seater plane managed the equivalent of 171 passenger kilometers per liter of fuel.
Jack Langelaan led Team Pipistrel-USA.com to victory.
"Together we've all shown that electricity is not only a viable, but in fact a beautiful, way of powering these airplanes," said Langelaan. "When our airplanes fly overhead, 2,000 feet up [610 meters], we cannot hear them. When they fly by, there are no emissions. The power to recharge our batteries came from a geothermal plant powered by geysers near Santa Rosa [California]."
Langelaan said it costs about $7.00 for the kilowatts of electricity needed to fly the craft for two hours.
Team e-Genius of California came in second place overall, winning $120,000 in prize money for an electric aircraft that traveled the equivalent of about 160 passenger kilometers per liter.
It also won another award. Eric Raymond accepted his team's prize for the quietest craft.
"A thought that just occurred to me is people expect progress through the passage of time, as if in the future there will be quiet electric aircraft, and it's really been slow in coming," said Raymond. "And what we really need is support for the engineers."
NASA's acting chief technology officer, Joseph Parrish, said these new aircraft are five to 10 times more efficient than conventional planes.
"It was not possible to win the Green Flight Challenge with an existing aircraft design. Innovation was required in order to win this competition," said Parrish. "Lighter batteries, more compact and powerful electric motors, sleeker and lighter structures are going to benefit more than just the aerospace community. They're going to usher in technologies that are useful in the automotive industry, in mass transit, in the green energy industries."
The CAFE Green Flight Challenge was sponsored by Google, and the prize money was awarded by NASA. The U.S. space agency says, collectively, the competing teams invested more than $4 million in pursuit of the prize.