Prius in the Sky

Today’s private planes are dirty and outdated largely because companies have no economic incentive to clean them up. Of all the transportation sectors, the general-aviation category has the fewest pollution regulations. But the green potential is tremendous, Seeley argues. Airplanes are far more aerodynamic than cars and, once aloft, they can cruise on minimal power. Cessna’s Columbia 300 gets only 20 miles per gallon at 200 mph. But planes designed to fly half as fast could do far better. While slower planes might not attract barnstormers, they would look great to commuters. “One hundred miles per hour is pretty much twice as fast as you get to go in a car,” says Greg Cole, the Columbia’s lead designer.

Cole is building a two-seat electric plane called the Goshawk that he estimates will travel at an average speed of 102 mph and get the equivalent of 438 mpg. And later this year, Slovenian plane-maker Pipistrel will begin selling its Taurus Electro, a glider that uses an electric motor on takeoff. “Electric propulsion is where it’s at,” Moore says. The clearest benefit is efficiency. Whereas piston engines extract about 20 percent of the energy in gas, electric motors use at least 90 percent of the power stored in batteries. The biggest obstacle is packing enough on board. Cole’s Goshawk can hold only enough
lithium-ion batteries for a one-hour flight.

New designs also borrow ideas from cars, like plug-in gas-electric hybrids. The Green Prize competition will allow entrants to use familiar automotive technologies, such as diesel, biodiesel and electric. Although a 100mpg plane won’t emerge at this year’s competition, Seeley expects to see planes getting well above 30 miles per gallon, a big step toward a new wave of cleaner, greener personal aircraft. “It’s critical that small aircraft be shown to be highly efficient,” Moore says. “You’ve got to show that before people are going to accept a lot more aircraft in the sky.”