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dubh12000
12th Jan 2010, 13:09
It just occured to me recently while reading about the differing methods that have been used in the KERS technology in F1 (dropped for this season onwards...). Has there ever been any work done by the airframers to convert any of that free kinetic energy coming onto the main gear from touchdown to rollout? I presume there has and the weight penalties are too restrictive.

Pugilistic Animus
12th Jan 2010, 20:35
I'm not sure what you mean?

but let me just say there's few 'new things' in aviation,...even aerodynamics, it was badly wrong, but once! in 1943:}

Cardinal
12th Jan 2010, 21:09
After some research the subject is apparently regenerative braking. The KERS system (flywheel based) is discussed here: Regenerative brake - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Regenerative_brake)

Pugilistic Animus
12th Jan 2010, 21:14
oh dynamic braking too heavy [generators use lots of iron and copper;)] too much to go wrong [I had better be on the mel],...too expensive

nope, ain't gonna happen--- they do have these devices called 'spoilers' though:)

bookworm
13th Jan 2010, 08:38
Kinetic energy of a 50 ton aircraft at 70 m/s (about 140 kt) is about 125 MJ.

Jet-A1 has about 40 MJ/kg. That means that if it costs 3 kg of fuel per landing to carry the system, even a 100% efficient system is only just braking ;) even. Typically, a flight might use fuel equivalent to 5-10% of the extra weight it carries, which means that a system for storing and re-using 125 MJ weighing 30 - 60 kg would only just be worth it from an energy point of view, let alone a cost point of view. Tough to achieve!

Capt Pit Bull
13th Jan 2010, 10:26
Yes, and consider that the current state of the art has a pretty tough time just reliably dissipating that energy safely, let along storing and reusing it.

megapete
13th Jan 2010, 11:31
A better bet would be to capture the energy at the airfield - to be used again to assist take off or just recovered to the grid?

P

David Horn
13th Jan 2010, 12:02
A better bet would be to capture the energy at the airfield - to be used again to assist take off or just recovered to the grid?

Oh Jesus, not the conveyor belt again... ;-)

Pugilistic Animus
13th Jan 2010, 14:14
how about some solar panels on top of the terminal:)

airborne_artist
13th Jan 2010, 14:28
You'd need a dedicated landing RW, but you could always use some of these clever speed bumps (http://www.guardian.co.uk/environment/2009/feb/08/alternative-energy-speed-bumps).

MOL's customers wouldn't notice the difference :E

fleigle
13th Jan 2010, 14:50
Why not an arrestor cable, a few pulleys, and a catapult to launch the next plane out ????.

WindSheer
14th Jan 2010, 21:58
Some electric trains use this re-generative method, they put power back into the grid when they are braking.

Clever!!

Pugilistic Animus
14th Jan 2010, 22:18
Yes they are directly conected to the conductors,....

further the heat from dynamic braking [on non electrified lines/diesels has to be dissapated through resistor banks ===heating elements,...let's place those near the fuel tanks:} and it's so heavy,.... you'd burn tons of fuel,...for absolutely nothing,...N.B the mechanical equivalent of dynamic braking is reverse thrust,..if it helps:rolleyes:


I guess 'Qwikipedia injunearin' don't hold up to someone who knows what what the hell he's talking about:ooh:

Lester:E

N1 Vibes
15th Jan 2010, 06:00
Here's a possible suggestion:

Israeli energy start-up turns traffic into source of electricity <br><br> - Haaretz - Israel News (http://www.haaretz.com/hasen/spages/1070010.html)

It's an Israeli firm that is intending to put piezoelectric cells under highways to generate electricity every time a car/truck passes over. I guess the restriction for aircraft landing is the technology has to deal with the weight/pressure and according to this article it needs a constant stream of vehicles on the highway. But still perhaps you could use it on the taxi-ways where there is more traffic?

Best Regards,

N1 Vibes

cwatters
15th Jan 2010, 23:40
> It's an Israeli firm that is intending to put piezoelectric
> cells under highways to generate electricity every
> time a car/truck passes over.

That's a really bad idea.

They fail to point out that the laws of physics mean there is no free lunch. The car or truck in question will be slowed down slightly. That's fine if it's used on the approach to a junction (the driver doesn't have to brake as hard) but bad news if used on the exit or an entire motorway. More fuel would be needed to maintain the same speed.

The question then becomes... Are a load of car engines more or less efficient than a power station at generating electricity? I suspect not so this idea would also increase C02 emissions.

It has a limited life as well. Once we all start driving electric cars we'll all have regenerative braking and want to use the energy ourselves rather than give it away to the electricity company.

The only practical application I can see is for powering illuminated road signs out in the country and solar panels might do a better job.

Pugilistic Animus
16th Jan 2010, 20:30
piezoelectric streets I'd hate to repair that every three second like in NYC:eek: