Battery plane could lead to take-off for electric aircraft
The European plane-maker Airbus has flown an battery-powered plane that could be the forerunner of a new generation of small electric and hybrid powered aircraft, as well as hybrid airliners capable of carrying 80 passengers.
Unlike most previous electric aircraft, which have been adapted from conventional airframes, the Airbus E-Fan has been designed from scratch as a dedicated electrically-powered vehicle, almost ready for commercialisation. Each wing contains a 65kg lithium-ion polymer battery pack that powers a 30kW motor driving a ducted, variable-pitch fan propeller.
The 6.67m-long carbon-fibre craft weighs 500kg unloaded and can fly for up to an hour at speeds of up to 220km/h. On the ground, the E-Fan is propelled by a wheel-mounted motor.
Airbus has designed the E-Fan for duties such as pilot training and acting as a tow-plane for gliders. It is planning to set up a new division called VoltAir that will design and build electric and hybrid aircraft from a base close to Bordeaux, starting in 2017. Initial products could include an all-electric two-seater and a hybrid four-seater. These could be followed by an 80-seat hybrid aircraft aimed at regional flights of three hours or more, using an on-board jet engine to charge its batteries.
As well as reducing CO2 emissions, the E-Fan is much quieter than a conventional aircraft, with lower levels of vibration. Airbus says that the “fuel’ cost to fly it for an hour is around $16, compared to $55 for a conventional aircraft of a similar size. Also, the performance of the electric propulsion system is not affected by high temperatures or altitude that can impair the performance of conventional propulsion systems. By mounting the ducted fan propellers on the fuselage, the plane is easier to control if one of them fails during a flight.
The E-Fan’s 120 lithium polymer cells can be recharged within an hour, but commercial versions may incorporate replaceable battery packs for rapid turnarounds. Future batteries with higher energy densities could extend flight times.
Scaling up electric aircraft for commercial passenger transport will require much more powerful motors. Airbus’ proposed 60-seater hybrid-electric airliner, called E-Thrust, would need six motors, each rated at around 670kW. The large currents needed to power these would pose problems in terms of cabling, connectors and control electronics. New Scientist reports that Airbus is working with motor experts from Siemens to look at ways of using superconductors for the motor windings and cabling.
Other companies that have demonstrated electrically-powered aircraft include Boeing, which flew a fuel-cell-powered plane in 2008, the Austrian plane-maker Diamond Aircraft, and a consortium called Apame, backed by French aerospace companies.