IT'S ELECTRIC: Fully electric airplanes are beginning to make inroads among unmanned aerial vehicles.
Image: flickr/nasa hq photo
Dully whining electric motors may soon compete with roaring turbofans in the sky as battery-powered planes and helicopters take flight.
Aircraft are emerging as the new frontier in electric vehicles as new technology and market demand converge to drive development. More energy-dense batteries, lighter components and more efficient power electronics are making plug-in airplanes a realistic prospect. Talk of taxes on greenhouse gas emissions and more stringent noise regulations have sent engineers looking beyond pistons and turbines.
In addition, electric aircraft have begun to post impressive results. Chip Yates, an electric vehicle developer, set a manned electric air speed record of 202.6 mph two weeks ago. The 16-minute flight over the Mojave Desert bested the previous electric speed record of 175 mph.
Last year, Pipistrel USA won NASA's Green Flight Challenge with an electric airplane that flew 200 miles with a fuel-equivalent efficiency of 403.5 passenger miles per gallon, which is the fuel efficiency divided by the number of passengers. Pascal Chretien, an aviation consultant and a test pilot, built and flew the first manned electric helicopter last August.
Why has it taken so long for airplanes to boldly go where cars have been for years?
The aviation industry is conservative about new technologies, stemming from culture as well as regulations, according to Peter Harrop, chairman of IDTechEx, a market research and consultancy firm. IDTechEx published a major report last month on the state of electric aviation throughout the industry.
The report details developments in electrical technologies, from airships to unmanned aerial vehicles. Harrop said much of the progress is driven by high fuel prices and market competition, especially in civil aviation.
Boeing and Airbus take notice
Though only small companies and entrepreneurs are currently making fully electric airplanes, larger manufacturers such as Boeing Co. and Airbus are investigating how to electrify portions of aircraft operations as the push for bigger, faster and farther yields to cheaper, quieter and greener. "We're on the tipping point," Harrop said.
One example is the auxiliary power unit in commercial aircraft. The device, usually located in the tail, is a generator that provides electricity to the plane when it's on the ground and gives power to start the main engines. It usually runs off a small turbine, but airline manufacturers are developing battery and fuel cell auxiliary power units to reduce their emissions and curb fuel use on the ground.
Another target is electrifying how planes move on the ground. Most aircraft taxi using thrust from their engines. At low speeds, this is tremendously inefficient; jet engines on an airliner can use 5 megawatts of energy, but a comparable electric drive system would use 2 kilowatts while producing no pollution and minimal noise, according to Harrop.
Boeing and Airbus are experimenting with electric landing gear that allow aircraft to turn, taxi and reverse on their own power without a truck to push the plane back from the gate. These systems can also integrate regenerative braking so that the energy from slowing a landing aircraft could charge batteries.
Some niche aviation applications are also looking to trade hydrocarbons for electrons. Harrop noted electric aircraft could be useful as trainers for pilots because the aircraft are cheap to operate and trainers seldom venture far enough to test range limits.
Defense contractors are also pursuing electric drivetrains to make stealthier unmanned aerial vehicles that have a minimal heat signature. They could also be charged on the fly from photovoltaic panels.
A mechanically simpler helicopter?
Electrification can also provide safety advantages. Hybrid electric propulsion can help extend flying time in emergencies. Electric drivetrains are also less mechanically complicated because electric motors can directly drive propellers and rotors, leaving fewer things that can go wrong in flight.
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8 Comments
Add CommentNagnostic,
Reply | Report Abuse | Link to thisI'm sure we can all agree you need to improve your online searching and navigation skills. It's quite telling.
Nagnostic, it's all a bit esoteric, but try this:
Reply | Report Abuse | Link to thisType "curiosity mars" in the search box.
You'll get about 80 articles.
carbon frames, solar skin, non-flammable batteries, low BMI passengers--definite terrafugue implications--but how do we prevent duct-fans from scattering gravel at velocity thru nabors' windows.
Reply | Report Abuse | Link to this'nabors'? (people who nab?)
Reply | Report Abuse | Link to thisThe article states:
Reply | Report Abuse | Link to this"Storing the electrons needed to power an airplane also carries its own unique risks, as poorly cooled high-technology batteries can catch fire or explode."
While cooling components in an airplane would not likely be a problem in most cases, extended departure delays can occur. It also seems that there have been many cases where (very difficult to cool) laptops have caught fire or exploded apparently due to battery defects. Perhaps 'aviation grade batteries' (analogous to aviation grade gasoline) could be specified to meet more rigorous operational requirements...
The prototype plane here appears to be similar to a lightweight glider design, which would not likely meet durability requirements for general use aircraft. Significant increases in structural weight would have to be offset by significant increases in power and battery capacity - also incurring additional weight... Production feasibility has not been demonstrated by the prototypes I've seen.
what about some kind of Hybrid. say something that uses electric for takeoff and landing. and some kind of Ramjet that kick in when certain speeds are reached
Reply | Report Abuse | Link to thismjacks2,
Reply | Report Abuse | Link to thisUm, you're thinking a propeller driven craft could get a plane up to Ramjet speed? They don't even work below 300MPH, don't even begin to be efficient below 600MPH, and work best a mach 2-4. Ramjets are only efficient when working within fixed pressure and speed conditions, so don't think it could be used to accelerate from 300 to whatever MPH either.
Hybrid automobiles gain much of their efficiency from being able to shut the gasoline engine off during stops at red lights etc. and by using breaking to recharge batteries. As a pilot with many hours in light planes, 300,000 lb jets and mach 2 fighter airplanes, I can see many advantages to using some of the same principles for aircraft. The takeoff and climb phase of flight eat large amounts of energy but also stores it as potential energy as altitude. Many large aircraft have a better glide ratio than light planes and can convert altitude to distance very efficiently without engines running, and stopping an airplane after touchdown that weighs more than several deseil train engines generates a trmendous amount of energy as wasted braking heat. Not much we can do about getting an airplane to altitude but cruise is fairly efficient and descent and landing are energy producers. Hybrid aircraft can capitalize on this in much the same way automobiles do.
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