Naked Science Forum
Non Life Sciences => Technology => Topic started by: satguy1 on 06/02/2009 16:40:21
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Could car wheels be fitted with windings and magnets to make them generate electricity as they turn? The car would be a gas/electric hybrid. The batteries would be charged any time the vehicle was in motion.
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Could car wheels be fitted with windings and magnets to make them generate electricity as they turn? The car would be a gas/electric hybrid. The batteries would be charged any time the vehicle was in motion.
If they only generates electricity you wouldn't get an hybrid, but electromagnetic brakes. If those brakes acts also as electric engines, than you have made a kind of KERS (Kinetic Energy Recovery System) even if usually they use a mechanical, instead of electric, system:
http://en.wikipedia.org/wiki/Regenerative_brake#Use_in_motor_sport_.28KERS.29
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When a good clean design finally settles in I suspect they will have motors in each wheel. When breaking the motors would generate power back into its storage system which could be some combination of battery and / or gyro-generator. If electrics caught on my guess is that batteries would be rapid change things that service stations owned and leased to users.
To fill-er-up you just zip into the station and change the quick-connect battery.
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Could car wheels be fitted with windings and magnets to make them generate electricity as they turn? The car would be a gas/electric hybrid. The batteries would be charged any time the vehicle was in motion.
If you generate energy by taking it out of the wheels' rotation it'll just mean that the engine has to work harder to keep the wheels rotating at the same rate. Also, as you're introducing another stage in the power chain, which will not be 100% efficient, you'll end up with s slightly less efficient system overall. As the others have said, it's only real benefit would lie as a braking system where some of the energy used to brake the car can be recovered instead of being wasted as heat.
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This seems to be just another version of "Is perpetual motion possible?"
And it isn't.
Of course, motor/generators in wheels are the way to go, however.
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Of course, motor/generators in wheels are the way to go, however
Weeell, I can't unconditionally go along with that. This is because putting the motors etc in the wheels increases the unsprung weight. This not only adversely effects performance, in terms of response times, damping and forces when the wheel goes over a bump, but also as a consequence, results in increased wear, both on the tyre and the road, which then reduces efficiency as a consequence of those increased forces.
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I agree; perhaps I should have said "for each wheel" rather than "on each wheel". Having said that, motors can be made extremely light these days
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Perhaps one solution would be to move the suspension from between the hub and the chassis to between the hub and the rim? Off-set spoked wheels provide a degree of suspension, as well as reducing the unsprung weight, so perhaps some type of 'intelligent' curvy-type hollow graphite spokes, filled with a lightweight damping fluid, might work. I suppose that it might also be possible to incorporate 'intelligent' spokes in an integrated active hydraulic design for the hub/rim assembly. Effective braking might be more difficult to achieve with the suspension between the hubs and rims though.
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I was thinking of the wheel itself being the motor / generator. It need not necessarily be all that much heavier than a wheel that is not a motor. This would then allow software control of differential forces etc.
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I was thinking of the wheel itself being the motor / generator. It need not necessarily be all that much heavier than a wheel that is not a motor. This would then allow software control of differential forces etc.
How could it not be heavier than a comparative wheel that does not incorporate all the motor stuff? The only way this could work is by comparing dissimilar wheels, which rather invalidates the comparison. You can't use exotic lightweight materials in the motor wheel and compare it with an ordinary wheel made out of pressed steel, and then claim that it's not much heavier; you'd need to compare the motor wheel with a motorless wheel made using the same technology.
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A drive shaft with a flexible mount for each motor would do the job. The effective unsprung mass would be the same or better than using the present system. You would need only one universal coupling, too. FWD would also mean less unsprung mass per wheel.
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Umm... the present system is to use a chassis mounted engine with flexible drive to the sprung/suspended hubs.
Now with a hydraulic drive system, on the other hand, not only do you get a very flexible drive transmission to the wheels but the weight of the drive rotors could be off-set against a reduction in weight of the braking system components because the hydraulic system could also supply the dynamic braking requirements (you'd still need a parking/hand-brake though).
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I had a 2CV with inboard discs! Revolutionary.
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I had a 2CV with inboard discs! Revolutionary.
Well yes, until you put the brakes on, at which point they would stop revolving, hopefully [;)]
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[;D]
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LeeE
Umm... the present system is to use a chassis mounted engine with flexible drive to the sprung/suspended hubs.
But the engine (/gearbox) is not on a flexible mount in the conventional system - you need two UJs on each shaft.
The motor could be at the centre of radial motion of the wheel suspension - very low moment of inertia and hardly affecting the total effectively unsprung mass.
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Apart from the engine mounting bushes, to deal with low-amplitude, high-frequency vibrations, you don't want the engine to be flexibly mounted in the chassis; that's what stops the engine from turning itself around instead of the drive shafts. The suspension then, is located between the chassis and the hubs, so it's only the wheels that are unsprung and the UJs are there just to cope with the changing geometry between the essentially rigidly mounted engine in the chassis and the suspended hubs.
Although brakes seem to be mostly mounted on the hubs these days, I can remember some older designs where the disks were mounted in-board i.e. on the drive shafts close to the UJs, which effectively reduced their unsprung weight. The trouble is, it makes them harder to maintain as you've got to lift the entire car up to service them, instead of just taking a wheel off.
I don't have a problem with using multiple engines on an engine per wheel basis but there is an issue with ensuring that each one supplies the right amount of power; should one of the engines suddnely brake down or drastically lose power it would be like applying the brake on that wheel only, which would make the vehicle very unstable and possibly uncontrollable - not good. Even then though, I see no benefit to mounting the engines outboard of the UJs, which you'll need in any case if any of the weight of the engines is to be sprung; if you don't mount the engines on something that is attached to the chassis then you're right back to unsprung engines again.
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My flexible mounting would be gimbals - not rubber! I don't understand your comment about mounting motors outboard of UJs.
ABS manages to balance the braking effort pretty well so I doubt that balancing the load on four Electric Motors would present a serious problem with modern control systems. As for one motor fault producing serious consequences - siezed brakes, broken wheel bearings and broken half shafts on a limited slip differential can all give their own problems. Not to mention collapsing suspension (been there!).
Any decent control system could switch to two wheel drive to give good control whilst you bring the vehicle to a halt.
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I think we may have gone running off in different directions here and are talking at cross-purposes; I can't quite see what, or where you'd be mounting anything, on gimbals. Looks like we may have to resort to diagrams.
But apart from that, while ABS manages a reasonable, but not perfect, job of preventing wheel lock-up during braking, just by comparing the rotation of each wheel in comparison to the others, it doesn't try to balance brake forces; it would need to be a pretty expensive high-performance car to justify the cost of an active/intelligent braking/traction control system.
While I agree that a sort of drive-by-wire system would probably be able to cope with the potential problems inherent in a design using independent engines for each wheel, aren't you just adding one system to deal with design problems in another when the design problems could be avoided in the first place? Sure, any many different faults can occur to just one wheel in a multi-wheel design utilising a single drive source anyway, but why add to their number?
Having said that, I'm still not sure what sort of design you're thinking of now, so perhaps it's benefits would outweigh the potential problems. I'm a bit confused.
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A picture is worth a thousand words.
Actually, it may only need a horizontal pin through the motor, but a vertical axis would probably be needed too in order to get the geometry right.
The longer the shaft, the better, probably.
It is likely that suitable wiring / cross coupling of the motors could act as a differential. It's amazing what you can do with electromagnetism, geometry and phases.
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I think this might be of some interest
http://www.youtube.com/watch?gl=GB&hl=en-GB&v=i1uTR-8KarE
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Right - I'm with you now. There you have an engine rigidly mounted in the chassis and driving the suspended hubs. You'd need a UJ/flexible joint at each end of the drive shaft though (think about it - it's rotating).
I think the only real factor governing the length of the shaft is the amount of movement of the hub you want to accommodate, primarily in the vertical plane, but also for general changes in geometry due to flexure of the wishbones and their bushes. A longer shaft allows a greater range of movement but increases mass and is more susceptible to torque-twist. Mounting the brakes inboard, near where the arc is in your drawing, reduces the unsprung weight, but like I said earlier, makes them more difficult to maintain, and perhaps, cool.
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You don't need a UJ on the inboard end because the motor 'casing' can rotate about two axes (gimbals - see my 'pin' on the diag.) to accommodate the up/down and fore/aft movement of the hub. Some spline joint may be needed if the radius of rotation of the suspension is not the same as the length of the drive shaft.
Inboard disc pads are as easy to change as outboard pads. The motor would probably be as easy (and cleaner) to remove as a wheel and would allow a disc (which could be right next to it) to be replaced. Actually, the disc could even be mounted on the other side of the motor - if the shaft passed right through the motor. Inboard discs represent less unprung mass, too.
The movies in teregram's links show a substantial extra unsprung mass is involved. With an 'active' suspension, this could be coped with, however.
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So you want movement of the wheel to not only move the entire drive-shaft but also the motor too???
Inboard disc pads are as easy to change as outboard pads
I can assure you that they're not, at least not on anything larger than a go-cart, although I do agree that inboard disks represent less unsprung mass. I think I've already said that.
Using an active suspension system could alleviate most of the control issues that come from increasing the unsprung weight, but they can do nothing to deal with the unnecessarily increased forces and wear upon the tyres and road that would also result from increasing the unsprung weight. It's a bad solution to an unnecessary problem.
You should stop and ask yourself why, if this is such a better way of doing things, aren't they already being done this way?
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So you want movement of the wheel to not only move the entire drive-shaft but also the motor too???
The motor would be extremely light compared with an 'engine' and it would be right at the fulcrum. That would mean a very low moment of inertia, which corresponds to a low unsprung mass (just think of the small angle of rotation of the shaft / motor around the fulcrum). I would envisage the drive shafts being almost full width of the car - not unlike some of the torsion bar suspensions.
Inboard disc pads are as easy to change as outboard pads
I can assure you that they're not, at least not on anything larger than a go-cart, although I do agree that inboard disks represent less unsprung mass. I think I've already said that.
I don't know which veh you worked on but for me it was a piece of cake. You lift the bonnet and reach in - take the pins out and off comes the calliper. You don't even need to take off a wheel - I've done it in ten minutes. In a system with regen braking, it's unlikely that you'd need to change them very often in any case.
Using an active suspension system could alleviate most of the control issues that come from increasing the unsprung weight, but they can do nothing to deal with the unnecessarily increased forces and wear upon the tyres and road that would also result from increasing the unsprung weight. It's a bad solution to an unnecessary problem.
You should stop and ask yourself why, if this is such a better way of doing things, aren't they already being done this way?
I agree - except the active suspension keeps your ride with 'g' pointing down. Dunno how your eyes deal with the horizon waving about tho'; that demo car looked like a scary ride, actually. It may be an acquired taste or it could just be a lot better.
They aren't being done the 'new way' because it's not been feasible until lately.
My suggested system is more basic and cheaper.
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The motor would be extremely light compared with an 'engine' and it would be right at the fulcrum
I think you're comparing dissimilar things here; you should be comparing similar electric motors mounted in different ways, not comparing dissimilar power plants, which make the comparison pretty meaningless. When you do that you find that having both the motor and the drive shafts moving increases the mass of the moving parts when compared with not moving the power plant. Why have the motor moving about when there's no need for it? you need a UJ of some sort at each end of the drive shaft anyway, whether it's placed between the chassis and the motor, or between the motor and the drive shaft, so why complicate it and increase the loads it has to bear unnecessarily, even if it by a relatively small amount when compared with a heavier power plant? Like I said, if you compare similar power plants, all you're achieving by having the power plant move is increasing the mass of the moving parts, which increases the requirements, makes things more complicated, not less, and more expensive, not cheaper.
Regarding just reaching in through the engine compartment to access inboard brakes: it might just be possible to do in my old mini, which doesn't have a large engine and lots of ancillaries filling the engine compartment, but even so, it would still be a tight squeeze to get two hands down there. For my other car, it would simply be impossible. Not only is the bonnet deeper but it's full of engine and all the other ancillaries; even just getting to a couple of the spark-plugs needs you get in to a particular contorted pose, in addition to using a UJ on the plug wrench. Incidentally, how would you deal with the rear brakes (assuming a front-engined car)?
And yes, with regenerative braking you might need to change the pads less frequently, but that assumes that the manufacturers don't downgrade the spec of the brake pads to suite the lowered braking requirements, and you can be sure that they will as it will reduce their costs.
Re the car in that demo: being able to raise and lower the ride height can be useful in vehicles that have to go off-road, but tilting it is a bad idea because not only is it likely to be disorientating and induce motion sickness but it also reduces your visibility on the side that's lifting; as you tilt over you'll not be able to see the road on that side - dumb idea. The only benefit I can see in it is to reduce shear forces in your neck at very high cornering speeds and if you're corning that quickly on a public road you're a danger to other road users. Funnily enough, F-1 cars use active suspension specifically to keep the car flat through cornering, as tilting the body would upset the aerodynamics.
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Changing inboard pads in conventional cars may be made hard because of the engine. There wouldn't be one in the new system.
You do not seem to take point that " unsprung mass" is not increased directly by the motor mass. A gimbal motor mount just has to cope with a non rotating, low stress load, as opposed to a UJ. The whole motor - brake unit could be lifted out by hand- slid off the drive shaft even.
There may be several reasons for rejecting the basic idea but I don't think your objections are as significant as you say.
We do share the reservations about the revolutionary ideas.
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.....and why do you insist that a UJ is needed each end of the drive shaft?
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.....and why do you insist that a UJ is needed each end of the drive shaft?
Because you won't be able to entirely eliminate all forward and backward movement of the wheels relative to the motor, so you'll need to accommodate movement from the motor to the hubs in two axis. Without doing this you'll end up with fatigue problems, either in the driveshaft, or in the motor bearings/mountings.
Even if the motor is fixed to the chassis and rotates as you suggest, it'll still impart a degree of torque on the hubs/wheels, which will have the effect of increasing the unsprung weight. Yes; with a very light weight motor this might be small, but it's still an unnecessary overhead.
I still can't see any benefit in having the engine/motor moving around when it's just the wheels that you want to move; the energy to move the motor has got to come from somewhere i.e. the power plant, which just reduces the energy available for propulsion and complicates the motor mounting, and which now has got to be capable of handling not only the power of the motor but also allow the motor to move as well.
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Using a spline joint will take out any stretch needed in the shaft. Even with UJs you would still need this if the geometry were not exact. What force do you think will produce 'fatigue'?
The motor will not 'rotate - it will just tilt/ oscillate and, yes there is a contribution to unsprung mass but how much torque is needed to tilt the motor by perhaps 10degrees+/- at the rate of wheel bounce? The Moment of Inertia is proportional to the square of the distance from the fulcrum and the relative MI of the wheel will be enormous compared with that of the motor (Which would only have much the same mass, actually)
The engine mounts would have very small load on them - they do not 'rotate' like a big-end bearing but 'rock' like a small end bearing and you must well know the difference in size and wear between those two on an engine of any given power. There is far more stress imposed on a UJ, because of its necessary small size. In fact, by removing one UJ and replacing it with a length of (tubular) shaft - you have reduced the total rotating mass.
You are not using the word 'power' correctly in your last para; the only 'power' involved would refer to 'rate of work done' . The only work done on moving the engine about comes from the movement of the road wheels up and down on the suspension and the contribution from the load of the engine is, as above, very small. Again, I don't think you have actually identified a source of 'energy loss' here - what force and what distance are involved?
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The issue isn't about needing the drive shafts to stretch but that there will a degree of forward and backward movement in the wheels relative to the motor producing a shear force if there's not a two-axis bearing between both ends of the drive-shaft. And yes, I used 'power' incorrectly there.
Other than that, I surrender. [:-X]
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A two axis mounting on the motor will achieve exactly the same effect of stress relief. How can it not? It will allow the wheels to be in any position within its limits and still be 'pointing at them'. The mountings will not allow the motor to rotate, of course.
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If anybody is still looking:-
The Michelin movie demonstrates what can be done, not necessarily what will be done, in the future. Re the banking of the car, only a nutcase would want to drive a car which behaved in that fashion (although they do it with trains?). The movie demonstrates the control that can be engineered into systems using electrical and programmable technology. The system shown could I think easily cope with keeping the car exactly parallel to the road surface under all cornering conditions.
A couple of points worth repeating from the (very poor) soundtrack are:-
There are no mechanical brakes,
Deceleration can reach 1g.
(I do not suggest that we have cars without brakes (reducing unsprung mass), but the system does make mechanical brakes redundant, apart from parking brakes.)
The accompanying movie with soundtrack in French, seems to claim that the motor power is 30Kw, (it’s only as big as a tin of beans!!!).
The comments about added unsprung mass are very relevant, but try
http://www.telegraph.co.uk/motoring/environment/2748517/English-electric-Lightning.html
Please read it all, and note for interest’s sake the comments on Nano Titanate batteries (relevant to the general discussion on electric cars).
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"If you generate energy by taking it out of the wheels' rotation it'll just mean that the engine has to work harder to keep the wheels rotating at the same rate"
That happens if you have generators that use kinetic force, that kind causes friction, but you can have a device that dont have resistance between the coils(static disc) and the magnets(rotative wheel), and using that type, this can be real possible... because the force applyed by the motor in the transmission will be the same of having a custom wheel, or a custom wheel with magnets side by side with a static disc generator!
i been trying to develop this kind of technology since october/08, and allready patent it here in Portugal, soon will put here some information about...
good work sophie centaur, how do you resolve the problem of the suspension? in your schematic you dont mention it.
sorry my english, :P king regards
If you generate energy by taking it out of the wheels' rotation it'll just mean that the engine has to work harder to keep the wheels rotating at the same rate. Also, as you're introducing another stage in the power chain, which will not be 100% efficient, you'll end up with s slightly less efficient system overall. As the others have said, it's only real benefit would lie as a braking system where some of the energy used to brake the car can be recovered instead of being wasted as heat.
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That happens if you have generators that use kinetic force, that kind causes friction, but you can have a device that dont have resistance between the coils(static disc) and the magnets(rotative wheel), and using that type, this can be real possible..
Do you not understand that you need to do WORK on a generator in order to produce Power from it? Even if you were to eliminate the friction, you would still have to provide power equivalent to the product of the V and I from the generator.
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V and I? sorry dont understand what you mean.
yes u'r right, you have to do work on a generator to produce power from it, but imagine an electric car with battery's, the car can almost use an alternate source like "solar or magnetic generator", so the batterys will never stay without charge to start the car again.
If the car is stopped the wheels are not generating, but also the motor is not consuming. But, imagine if case the 4 wheels generators was so efficient, that the regenerative system can produce more energy at movement that the one that is being applyed on the motor, you will allways have a small reserve of battery charge, to start the car again after you stop it.
this can be helped by small wind turbines at the front of the car, maybe in the spot of the radiator(cooler), because when you move your are constantly passing by air that can rotate wind generators at high speeds.
The question is, how much energy can we get from 4 friction less wheel size generators at 20km/h (example), and how much energy a standard electric motor consumes from the batterys at the same speed. At more velocity more energy is being consumed, but more energy is being generated to.
The system will work like the Electric Hybrid, that can constantly recharge the batterys with a fuel generator, and feed the electric motor at the same time, or like the standard fuel motor cars, that can constantly charge the battery with the alternator, and feed the electric system (lights, panels, cooler, etc) in simultaneus.
the system, will be a standard electric car, one light motor connected to the transmission.
Do you think that maybe it can be done?
Maybe this will have interest,
http://www.greenoptimistic.com/2009/03/05/thane-heins-back-emf-recovery-free-energy/
"His device can accelerate a motor from 100 rpm to 3,500 rpm without increasing power. Every electric motor has a force that opposes the propelling electromagnetic field inside it, called “Back EMF”. Heins succeeded to recover this back-EMF and, instead of letting it cause resistance, he transformed it into useful power."
Do you not understand that you need to do WORK on a generator in order to produce Power from it? Even if you were to eliminate the friction, you would still have to provide power equivalent to the product of the V and I from the generator.
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Electrical power = V(volts) times I(current)
That must be supplied from somewhere. You don't get it for free.
However you get it. Wind generators will need to be pushed through the air by the motor - and don't say you're moving anyway because the motor will have to be pushing harder to provide the IxV again.
Any external input will be useful but solar cells are pretty low power, providing a few tens of Watts unless they are a Huge Area, as on a satellite. Best bet is to carry lots of charge in batteries. The latest design may give an advantage.
Regenerative braking could return some of the Kinetic Energy of your moving car back into the battery. The hybrid system is a good one because the energy from the fuel doesn't have to be lost when you slow down and you can operate your engine at maximum efficiency. It ain't magic, though.
I'm afraid the last thing about 'back emf' is not right - or you didn't read it right. Back emf doesn't actually constitute a loss of energy.
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i was talking about new gen wind generators, the wind come from the front and goes out to the back of the car, without causing resistance, that will be the same, you only will be regenerating the air energy, the force of air against te car will be equal, with or without wind generators.
Electrical power = V(volts) times I(current)
That must be supplied from somewhere. You don't get it for free.
However you get it. Wind generators will need to be pushed through the air by the motor - and don't say you're moving anyway because the motor will have to be pushing harder to provide the IxV again.
the wheel generators without friction will work like the hybrid system, even if they cannot be overunit and regenerate all the energy that the motor use, it will give u much more efficiency and drive distances.
dont understand u, you dont think it can be done?
Any external input will be useful but solar cells are pretty low power, providing a few tens of Watts unless they are a Huge Area, as on a satellite. Best bet is to carry lots of charge in batteries. The latest design may give an advantage.
Regenerative braking could return some of the Kinetic Energy of your moving car back into the battery. The hybrid system is a good one because the energy from the fuel doesn't have to be lost when you slow down and you can operate your engine at maximum efficiency. It ain't magic, though.
i have just copied the text from the green optimistic site, i dont invented nothing, and i dont say that the back EMF constitute a loss o energy, simply is a force the opposes the propelling electromagnetic.
I'm afraid the last thing about 'back emf' is not right - or you didn't read it right. Back emf doesn't actually constitute a loss of energy.
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dont understand u, you dont think it can be done?
I KNOW it can't be done because your idea that, somehow, the turbine can be made to turn without consuming any power (from some source) is not viable. If your turbine is turning your generator which is generating electrical power then there HAS to be a source of power. This power must come from the car engine, in this case. That is the most basic law of all Physics. For a turbine to turn, there has to be some air turbulence - an efficient body shape reduces drag as much as possible byt promoting laminar flow as much as possible.
The same thing applies to 'wheel generators'.
Either the green optimistic site is in cloud cuckoo land or you have misread it, somewhere.
You can't eliminate friction and you can't get energy out of a system that you haven't put into it. Any machine will be a net consumer of energy.
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light or not you will just be taking the energy u already produced for one reason and use it for another. this would most probably leave ur initial reason for producing that energy at a very big loss. also taking energy away from brakes will lead to their not working as effecients. car makers go out of their way to add extra energy into their braking sytems (eg bmw, heating the brake pads before the brakes are to be applied). you must produce heat in order to stop a car. if you make a system that somehow takes that heat away then there must be some performance that is decreased. producing a system that is more effecient in getting energy out of the fuel is the only salvation for mother Earth.
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light or not you will just be taking the energy u already produced for one reason and use it for another. this would most probably leave ur initial reason for producing that energy at a very big loss. also taking energy away from brakes will lead to their not working as effecients. car makers go out of their way to add extra energy into their braking sytems (eg bmw, heating the brake pads before the brakes are to be applied). you must produce heat in order to stop a car. if you make a system that somehow takes that heat away then there must be some performance that is decreased. producing a system that is more effecient in getting energy out of the fuel is the only salvation for mother Earth.
That is rather mixed up. You do not 'need' heat to dissipate KE; the process of simple friction braking just transforms the KE into thermal energy (cause and effect are the reverse of your statement). BMW use a practical solution for increasing friction,I guess - it's not fundamental.
The acceleration and braking cycle, will not be efficient, of course, but regen braking can help.