The Future of Electric Aircraft

"World fuel reserves are continuing to dwindle as demand increases. This inversion of the supply/demand cycle will increase operating costs of all fuel-based vehicles, especially in the aviation industry. Nowhere is this more apparent than in the commercial helicopter market, where the critical role rotorcraft play could be threatened by spiraling fuel costs," said Mark Miller, Vice President, Sikorsky Research & Engineering, in a statement.

Hybrid aircraft

Meanwhile, in Europe, EADS is developing a hybrid helicopter concept that uses two diesel engines driving generators and two lithium-ion battery packs to power electric motors on the main and tail rotors. EADS showcased this diesel-electric hybrid helicopter concept at the 2010 ILA Berlin Airshow at Berlin-Schönefeld Airport in Germany in mid 2010 and an all electric stunt plane. It argues that fuel consumption and emissions can be considerably reduced by the hybrid propulsion technology.

In July this year, there was a symposium on these "More Electric" aircraft. Prof. Alberto Tenconi of the University of Turin is behind the Italian electric aircraft program and he has his sights on electric feeder aircraft for passenger routes. On the other hand, in the UK, Falx Air Vehicles is planning to push fuel economy further by using a hybrid-electric motor and inbuilt solar arrays in tilt rotor aircraft. The company expects its upcoming compact single and double-seater tiltrotor aircraft to use only 10 liters of fuel per hour airborne, and the quiet electric operation should see these small, light and manoeuvrable aircraft also act as good military stealth vehicles.

Fuel cell aircraft

171 years ago, the fuel cell was invented in the UK, where Intelligent Energy now has its fuel cells powering experimental aircraft. As in on-road vehicles, fuel cells in aircraft are used rather like hybrids, with a sophisticated battery to manage load variations and regenerative charging. The SkySpark team in Italy now plans to focus on an engine powered by hydrogen fuel cells, something used by AeroVironment in huge fixed wing unmanned surveillance aircraft that cruise the upper atmosphere. The leading aircraft manufacturers Boeing and Airbus, a subsidiary of EADS, are interested in the possibility of large passenger aircraft taking off and landing in almost total silence by using all electric mode, possibly with fuel cells involved.

What next?

Certainly, the electrification of aircraft is intimately related to the electrification of land and water vehicles. They use the same or similar batteries, battery management systems and motors. Removing weight is an almost universal objective. Of interest are printed electronics and electrics from companies such as T-Ink, wireless sensors and actuators and energy harvesting as developed by the Center for Energy Harvesting Materials and Systems (CEHMS) at Virginia Tech and photovoltaic energy boosting as analysed by IDTechEx, preferably in transparent form over the whole vehicle.

Regenerative braking in an aircraft sounds fanciful but recent studies indicate that a regenerative soaring feature is possible, whereby the propeller can be used as a turbine to recharge stored energy when the aircraft encounters an updraft. This is similar to the way the new hybrid electric motor-sailing boats will regenerate next year using their propulsion screws. An aircraft using regenerative soaring can potentially remain aloft indefinitely at high altitudes where the energy available from vertical atmospheric motion can exceed available solar power by a factor of ten or more. And remember that the pure electric Deepflight submarines of Hawkes Ocean Technologies act as aircraft underwater and have similar opportunities.

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