Thursday, 02 October 2014
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Aircraft power needs could be met by landing-gear wheels

Future aircraft could contribute to their power needs by harnessing energy from the wheel rotation of their landing gear to generate electricity.

They could use this to power their taxiing to and from airport buildings, which would lead to savings on aviation fuel, cutting emissions and reducing noise pollution.

According to a statement, the feasibility of this — part of the Research Councils UK Energy Programme — has been confirmed by a team of engineers from Lincoln University with funding from EPSRC.

The energy produced by a aircraft’s braking system during landing — currently wasted as heat produced by friction in the aircraft’s disc brakes — would be captured and converted into electricity by motor generators built into the landing gear. The electricity would then be stored and supplied to the in-hub motors in the wheels of the aircraft when it needed to taxi.

‘Engine-less taxiing’ could therefore become a reality. ACARE (Advisory Council for Aeronautics Research in Europe) has made engine-less taxiing one of the key objectives beyond 2020 for the European aviation industry.

‘Taxiing is a highly fuel-inefficient part of any trip by aircraft with emissions and noise pollution caused by jet engines being a huge issue for airports all over the world,’ says Prof Paul Stewart, who led the research.

‘If the next generation of aircraft that emerges over the next 15 to 20 years could incorporate this kind of technology, it would deliver enormous benefits, especially for people living near airports. Currently, commercial aircraft spend a lot of time on the ground with their noisy jet engines running. In the future this technology could significantly reduce the need to do that.’

Lincoln University’s research formed part of a project that aimed to assess the basic feasibility of as many ways of capturing energy from a landing aircraft as possible.

‘When an Airbus 320 lands, for example, a combination of its weight and speed gives it around three megawatts peak available power,’ Prof Stewart explained. ‘We explored a wide variety of ways of harnessing that energy, such as generating electricity from the interaction between copper coils embedded in the runway and magnets attached to the underside of the aircraft, and then feeding the power produced into the local electricity grid.’

Most of the ideas weren’t technically feasible or cost-effective but the study showed that capturing energy direct from a aircraft’s landing gear and recycling it for the aircraft’s own use really could work, particularly if integrated with new technologies emerging from current research related to more-electric or all-electric aircraft.

A number of technical challenges would need to be overcome. For example, weight would be a key issue, so a way of minimising the amount of conductors and electronic power converters used in an on-board energy-recovery system would need to be identified.

The project was carried out under the auspices of the EPSRC-funded Airport Energy Technologies Network (AETN) established in 2008 to carry out low-carbon research in the field of aviation, and was undertaken in collaboration with researchers at Loughborough University.


Readers' comments (28)

  • How much would a storage system for 3Mw x 30s (= approx 25kwh) weigh? The 30Ah battery (= approx 0.4kwh) in my car probably weighs 20kg.
    How much fuel would have to be burned to fly this extra weight from one end of Europe to the other?

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  • This has been raised previously and someone made the good point that the engines would most likely be running anyway during taxiing so savings from this power source may be minimal. Lateral thinking suggests an aircraft with high friction skids landing on a conveyor belt runway which when moved by the force of an aircraft landing would recover all the power from landing in a ground based accumulator. No weight penalty.... indeed a substantial weight saving from less complex landing gear. Taking off would entail the aircraft being accelerated to V2 by the use of the power stored to move the conveyor belt with the aircraft on it. How the aircraft would taxi there is another problem, perhaps a giant powered trolley jack... :o)

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  • Well, taxiing electrically with the engines at idle hardly saves any fuel. Jet engines tend to produce more than enough thrust at idle to taxi (once taxi-speed is established). So, 90% of the taxi-time is spent with the engines at idle.

    I see another drawback if you turn on the engines moments prior to take-off. It is only then when you find out if the engines are fully operational or if there is a (slight) malfunction for which you now need to taxi all the way back. A whole hour of taxiing as a result at some airports.

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  • Radio controlled ground tugs might be the most efficient way to move planes around the airport and its runways. Could be controlled by the pilot then released by the pilot to the control of the tower.
    I've often thought that landing gear wheels should have fairings and vanes to promote rotation before touchdown to prolong the life of tyres and minimise the skid at touchdown.
    Saving onboard fuel, energy, when taking off and touching down might have a lot in common with the aircraft carrier situation.

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  • This is one of the best move that will have been made in aviation. A lot of energy is lost on landing that when converted to useful form it will not only be economical but environmental freindly. Weight affect aircraft perfomance so additional weight should be kept low. Good luck.

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  • High-friction skids on a conveyor would actually impose a substantial weight penalty on the aircraft. The spin-up and spring-back loads resulting from a dynamic landing can design much of the aircraft: the landing gear, attachments to the wing, and even the fore and aft fuselage. By making the landing a high-friction event, you increase those loads substantially, thereby adding weight.

    An onboard combination of regenerative braking and APU-powered wheel drive would get around this problem by spinning up the wheels prior to touchdown. The problem is still, of course, a substantial weight penalty, which would likely make it economical only for short-range aircraft.

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  • This type of generation has been used on forklifts for years and still causes debate as to the benefits.
    It maybe better to harness the electricity to assist wheel braking, thus reducing heat build up of the brake discs resulting in longer brake life?

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  • Generating electricity from the interaction between copper coils embedded in the runway and magnets attached to the underside of the aircraft would mean digging up he runway but wouldn't need the weight of an energy storage system on the aircraft and would slow the aircraft even if the runway was slippery, improving landing safety

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  • Can't we fit the aircraft with arrestor hooks and extract the power from the arrestor gear? This is a long-established technology, we just need to scale it up from Tomcat size to Jumbo size. We could substantially reduce the length of runways as well. And before anyone says you can't do that with big aircraft, watch this. http://youtu.be/BjNyQvhsQE8

    In fact, I don't think this one even used arrestor gear!!

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  • Is news quiet this week? I guess this 'news' is due to the engineering equivalent of the political 'silly season'?

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