Is this just rubbish?

I should just add that I'm not suggesting this as a way to power the car, but as an added way to recharge the batteries, thereby prolonging the range between charges.

What about an overhead electric cable, a pantograph and an earthed metal plate running along the road?

Or a slot in the road into which is lowered an electric pick-up skate?

Always so criticle. Get a life, and maybe practice doing things, as opposed to just criticising, about other people's ideas. If it were for people like you, we'd still be living in the Medievil times.

Those that can do, do; those that can't do, teach; and those that can't teach, complain and overtly critcise.

You apparently, cannot do, and cannot teach !

This doesn't seem to be an appropriate reply to #2.

Maybe you fall into your own category?

Maybe you should carefully r e a d all the posts, then reply (carefully)

(perhaps have a pencil and paper with you, for any long words)

Phil Anthropist

I agree. PW Slack is not known to be randomly critical, and if anything, is known for perceptive comments.

Edit: Never mind.

Windmill....!!!...!!!

Falls off chair...you are havin' a Steffi.....?

It's the old put a fan on the back of your sail boat to blow into the sail conundrum.

Although, if you popped up the wind mill as a brake, then you might gain some!

Hi Del the cat. Not so stupid! In 1978 a company in Germany constructed a sea going ship that was powered by wind turbines. The turbines were conected to a gear box which in turn turned the propeller shaft. Just like sails the turbines could be moved to face the wind in all directions except straight forward. There were three wind turbines on this ship and each turbine had five blades, it attained a speed of 17 knots on it's trial run. The only problem was that they could not sail into the wind. At the time there was an oil scare, so many different companies tried to design a ship that was not dependant on oil. Spencer.

I am suitably chastened!

Wait a minute! You need not feel so chastened. There is a world of difference between powering a boat with a windmill (in which case the energy comes from the wind's momentum i.e., an external source) and powering a car from energy derived from it's own motion (in which case, the energy comes from the car's fuel tank via the engine). (Windmill powered boats, incidentally sail well directly into the wind -- something an ordinary sailboat cannot do.)

The original post said: "so that as the car drives over it, instead of using power it generates it". The italicized "it" means the car, I think we can agree. (The logic seemed to be that the car would be working like a linear motor generator, with something in the car serving as the armature, and something in the road serving as the stationary field.) So no, it would not make sense to generate current by using the car's motion: this only makes sense if you want to slow the car, as in regenerative braking.

Charging a car inductively, as it moves over electric coils in the road, is quite different than the original poster seems to have proposed. In this case, the energy is again coming from an outside source -- the vehicle's motion is not generating the energy. There is no fundamental difference between this and plugging in -- it's simply more convenient but somewhat less efficient.

So you might have "jumped" on the original poster a bit, but as I read the post, it certainly seems he was proposing to generate electricity by virtue of the cars motion, not simply to receive energy inductively from the power company. If that is the case, then you are not alone in cringing a bit.

Yeh, I was just trying to extricate myself gracefully without upsetting RIKK ! lol

Unless there was something else in their design, what would prevent the turbines from facing into the wind? I assume that they are mounted on some sort of swivel. Of course that makes them a bit more complex than a fixed mount.

By the way, Jacques Cousteau solved that problem with a boat powered by a cylindrical turbine that spun the same regardless of wind direction, like an anemometer that measures windspeed regardless of direction. The trick is in the type of airfoil used to turn the generator.

Normally, when we think of a turbine, we only think of the type that has a single inlet and a single outlet, such as used in electrical power plants to obtain electricity from steam or water flow. In a standard windpower application these would spin about a horizontal axis pointed straight into the wind for maximum efficiency/power generation. In the Cousteau design the turbine spins on vertical axis, like the wind powered ventilator fans common on many roof tops. Wind passing over these from any direction will have the same effect and you need not turn them into the wind for maximum power.

Unless there was something else in their design, what would prevent the turbines from facing into the wind?

I'd guess that Spencer might have the directions backwards. The real forte of windmill powered boats is that they can sail directly into the wind, reducing travel distance (if you actually want to go to windward) by 30 percent or so. In fact, when you do the math on these things you say "Wow, if I can sail straight into a 10 knot wind at 5 knots over the ground, then my apparent windspeed is 15 knots. Given that lift goes up with the square of apparent wind, my windmill can generate 2.25 times as much force at 15 knots apparent as it can with 10 knots apparent. So I have more force and can accelerate even faster because of the apparent wind building. That means more apparent wind, and more force, etc. I COULD RULE THE WORLD! (Where windmill-powered boats don't so so well is with the wind directly behind. Then as the boat accelerates, it robs the windmill of its apparent wind.)

That (I could rule the world) line of reasoning is not altogether haywire, and it actually applies to any fast sailboat, like a windsurfer or an ice boat, or my own boat in my avatar. Of course, aero drag also increases with the square of speed, and certain regimes of hydro drag increase even faster (but then the regime changes and suddenly the curve flattens out...)

What the heck is this thread about?

Oh well, I'll ramble a bit more, because you may find it amusing: On my own boat, with 10 knots true wind from abeam, and the boat stationary, the lift (which is called lift by aero convention, even though the vector is horizontal) directed forward is on the order of 100 pounds. The whole boat and its pilot weighs about 400 pounds, so it accelerates at .25G (Don't ya love the English system of units so we can be so sloppy in mixing up mass and weight?) So the boat accelerates to 20 knots, and the apparent wind, along the hypotenuse, is now 22.36 mph or so. The lift produced is now 500 lb (100 x 22.36^2 /10^2). Unfortunately, most of that is trying to push me sideways, but almost 250 lbs is available to push me forward. Wow!

The hydro drag is now about 15% of the boat's displacement, or just 60 lb. The vector of aero drag (which aligns pretty well to slow the boat) is only about 8% of the total lift, or 40 lb. That means, that at 20 knots boatspeed (still in the original 10 knot true wind speed) I have a net thrust of 150 lb after subtracting drags, and after taking into account the unfavorable vector direction of the lift. When the boat was standing still, I only had 100 lbs. So now the boat is actually accelerating faster than it was at the start -- all because it is sailing on its own wind. This works in practice as well as theory, with the acceleration rate noticeably better at 20 knots boatspeed than it was at 5 knots boatspeed. Dreams of perpetual motion ensue.

At very high boatspeeds, the vector angle problem becomes severe (in other words, even more lift goes into blowing the boat sideways, and proportionally less pushes it forward), aero drag becomes more pronounced (and even better aligned for boat slowing) and hydro drag has gone up too (although by only 20% or so). So the sailor's dreams of perpetual motion come to an end.

Where this phenomena is most striking is in ice boats, some of which cannot get moving in 5 knots of wind without a push, but will sail at 35 or even 40 knots in that same wind. (One land speed record contender claims a 10:1 boatspeed:true windspeed ratio)

Why is it so stupid?

We have a fan on the front of the car to cool the radiator, why not one to run the lights, radio etc..

Why is it so stupid?

The windmill would add wind resistance which absorbed more power than it generated!

That's why it's only good as a brake.

The fan and alternator, waterpump etc on a car all consume power.

It's a bit like saying, on your electric car...why not power a big halogen lamp, and shine this at a solar panel to generate some electricity...hey then you could drive at night!!?

Wow...Lunar panels ...theres an idea!

(No offence intended in the original post)

PS...

Before someone jumps on me...I know aeroplanes have drop down generators (windgenerators) which will give emergency power in event of total engine failure...but these are extracting potential & kinetic energy from the trip back down to earth!

(The solar panels or regenerative braking seem the only way to get some power..unless you want to pedal!)

Del

I think it's a drag issue. The fan will create drag. It will take more power to move the car because of that drag. You cannot gain more energy from the fan than is required to turn it. There will always be some loss. In this case you are just wasting energy.

The fan has nothing to do with this thread anyway, and is a petty point to be arguing over.

The fan has nothing to do with this thread anyway, and is a petty point to be arguing over.????????????????????????????????????

Well why put this in the question?

!!!!!!!!!!!!!!!!!!!!!!

"The obvious ways are solar panels, and maybe a little windmill"

!!!!!!!!!!!!!!!!!!!!!!

Is that it?

I came on here for a serious discussion, what did I do to deserve you?

GIGO

"GIGO"

Do you really have nothing better to do that frequent forums to contribute nothing?

People like you are two-a-penny, unfortunately.

LOL

Suggest you check facts before criticism!

Reducing the drag by coupling them nascar style [drafting] would also increase the range of all vehicles, wind drag is 1 of the bigger power robbers.

The lads get frisky when anything that sounds like perpetual motion is mentioned around these parts!

Embedding power distribution in the roadbed using inductive coupling is certainly technically possible. I worked on a project proposal to do this several years back. The biggest impediment (obviously) is the cost of digging up miles and miles of roadbed to embed the required coils. Then there's maintenance (I live in the northeast U.S., where the roads are constantly chewed up by harsh winters).

Much of the work on powered roadways was done by the California PATH program. There's a good report at: http://www.path.berkeley.edu/PATH/Publications/PDF/PRR/92/PRR-92-17.pdf or, for more info, search Google for "powered roadway"

(By the way, the windmill thing won't work, but I agree, it's not worth wasting this whole thread name-calling about it).

Right on!

What the OP tried to describe (if I understand correctly) is a DC system, in which the motor couples as a dynamo to re-charge the battery while breaking in slopes.

Not a bad idea at all, which brings me to the point:

- It's probably implemented already by Electric or Hybrid car manufacturers in given models of near-future ones.

- It is actually so obvious, I would genuinely be surprised if it wasn't implemented in existing models, without even checking.

It is actually so obvious, I would genuinely be surprised if it wasn't implemented in existing models, without even checking.

How can you say such a thing?? Regen is a very recent development!* Here's a quote from The Electric Car my Michael Westbrook: The French were proving to be particularly inventive in the electric car field, exemplified by the electric coupe demonstrated by M.A. Darracq in Paris in 1897. The vehicle was notable because it used regenerative braking for the first time.

* I'm speaking in geological time, of course.

Regen is used in virtually every EV and hybrid that is intended for the road. Many golf carts and fork lifts use it, although there, people are less concerned with range, and don't think a great deal about the environmental consequences -- so there are still lots of vehicles in those classes in which regen is not implemented.

Aside from the phenomenal cost of linear motors in which one part of the motor is in the vehicle, and the other part is built into the road, there is also the issue of efficiency. It is comparably easy to achieve the small clearances required for high flux density in a cylindrical motor. Imagine the difficulty in maintaining .5 mm clearances between a road and a rubber-tired, spring-suspended vehicle.

You're right Ken, I shouldn't be the evident impulsive bugger I usually am. However, reversing the role of a DC motor to act as dynamo to re-charge the battery, is pretty obvious, isn't it?

As obvious as the nose on your kitty's face.

"Just say the magic woid!"

It's simple. Lay tracks on the road for guidance. String electrical wires overhead. Attach electrical wipers to poles that extend from the car to the overhead wires. Voilá - streetcar.

Certainly you can use solar panels. I just read an article about a company that modifies Prius's with a solar roof to further increase the gas mileage.

You could, in theory, bury giant coils under the streets and couple that power into passing cars, but it would not be efficient.

It's actually quite efficient. It's just expensive. See my post above.

up to 65%.

I stand corrected.

See 'MIT Scientists Show How To Light A Bulb Wirelessly'

In 'latest engineering news' section.

I believe this is pertinent.

(But I reserve the right to be wrong)

In order to create the electrical power you have stated the vehicle motor would have to work harder. Which would mean bigger motor to due more work. The power generating device would act as a drag slowing vehicle down. Meaning you would have to give it more fuel to maintain speed.

It would be more economical to use the fuel directly in a generator. Mechanical and heat losses of energy from the vehicle would make it inefficient.

Can't get something from nothing.

Electric cars already have such a system. Any electric motor is a generator. In the simplest case, a permanent magnet motor will, as a motor, have a speed of (let's say) 70 rpm per volt. If you disconnect the leads from motor, and spin it by hand, you will find that it produces 1 volt for every 70 rpm. Therefore, when you apply 48 volts to this motor, it will accelerate to speed of 3360 rpm, at which it is generating a counter EMF of 48 volts. The applied voltage and the counter EMF cancel, and current (and therefore torque) drop to (near) zero, and the motor stops accelerating. (This is only slightly oversimplified.)

So... when an electric car is going faster than the speed demanded by the driver, it generates current which naturally recharges the battery. This current can be slight (as when coasting down a gentle hill) or quite a lot (as when the driver puts on the "brakes"). Thus, to generate current to recharge the batteries, the car's kinetic energy is converted to potential energy in the batteries, by means of the motor acting as a generator. Because kinetic energy is being converted, that means the only time an electric car can put energy back into the batteries is when it is slowing or being gently braked to maintain a speed going downhill -- in other words, when the driver is demanding a lower speed, either by backing off the speed control or applying the "brakes".

This regenerative braking effect is applicable to even the simplest of cars. Suppose you make a toy car that goes 2 mph with its rechargeable batteries. You wire the batteries directly to the motor, and the wheels start spinning. Let it run around the floor until you can see it slowing down. Then push it at 3 mph for a while. You'll recharge the batteries and restore the car to its original speed. (The energy you expend in pushing it will now be in its batteries -- minus, of course, the heat losses, as represented by your sweat, the warm motor windings, warm tires, etc.) You'll notice, that its a little hard to push it at 3 mph... it "wants" to go slower.

BTW, whether the motor is linear or rotary doesn't change the fundamental relationship. As you said, a linear motor is just a motor stretched out into a line.

Even the 1896 Porsche electric car had regen, and regen can charge batteries, but it is far from perpetual motion. Even if the regen were 100% efficient (returning the energy of acceleration every time you stopped) there are still large energy requirements for rolling along on soft tires, and pushing air out of the way (the two of which are about equal at 30 - 40 mph -- depending upon tires, weight, and aero efficiency -- with aero drag taking over at higher speeds.)

You might wonder if a separate generator would work better at recovering energy. Probably not. Given a high efficiency motor, the slight gain in optimizing a separate motor to be a generator is probably not justified by the extra weight of the generator and it's wiring (and electronics).

just a thought on what you were saying...what if one made the generator an actual complete braking system? if you spin a a rotor head of a generator disconnnected from the wiring for a second and then connect the wiring it stops it due to generating the electrical current; so what if to brake, the brake pedal just engaged the drive shaft to a generator? this would of course generate energy but more importantly for the immediate it would brake the car, dependin obvouolsy on e the specs of the generator etc.

That's actually very close to how regenerative braking works now. In efficient electric vehicles, when you apply the brakes, it effectively turns the motor(s) into generator(s), and the generated current goes into the batteries. As long as the batteries are not overcharged, the braking force can be quite high -- high enough that in normal driving little or none of the braking energy comes from the friction brakes. The same brushed motor that is 92% efficient as a motor might be 92% efficient as a generator, if the brushes are not offset to favor one direction of rotation over another. In brushless motors (which are typically three phase motors, but usually with permanent magnets) the commutation is handled electronically, and generally by the motor controller. The same motor controller controls dynamic braking, so the commutation can be varied electronically to make the motor equally efficient as a generator.

A car like the Tesla is capable of "spinning" the wheels (exceeding available traction)during acceleration, so its regenerative braking should also be capable of making the tires squeal.

If the batteries cannot accept any more charge, then this all falls apart, to some extent, with the excess current fed into resistors, and with the friction brakes more heavily relied upon.

If you had a plug in hybrid, and lived at the top of a hill, you'd want to cut the recharge a little short, to allow the hill and the stop at the bottom to charge the batteries, rather than paying the power company, and letting the braking energy go off as heat.

A journey to home and back will always have the same nett potential energy. Unless you have a multi-storey carpark in your yard!

However parking on a slope so you can accelerate away using gravity to overcome the initial inertia (is that a tortology?) sounds like it will save some juice.

Here's a thought. You live in a 50 story building, in a flat city. You work on floor 25 of an office building a few miles away. You coast to work in the morning, docking your car on floor 25. Then you coast home at night. You work long hours, so that when you get home, the electrical rates are low. An elevator lifts you and your car back up to the 50th floor, using cheap electricity. Your car uses regenerative braking to stop when you get to work and back home, and that energy is inverted and sold back to the power company each night.

Oooo! I've got it. You live in a pod on the outside of a solar tower (see thread here). Once you've coasted home, you drive into the solar tower, deploy a parachute, and are lifted to your pod. You wear a Nomex suit.

You must be an extraordinarily hard worker. You wrote: "A journey to home and back..." Many people would have written "A journey to the office and back..."

LOL,

Nice one!...you want to know how hard I work?...read my profile and weep!

When I was a kid we had this wonderful tin toy...it was a hopper on top of a tower, a track sloped down to the floor with a lttle truck on a string with a counterbalance weight.

You filled the hopper with sand....

sand trickled into the truck until it was heavier than the counterweight...

The truck shot down the track, hit a stop tipped out the sand...

shot back up...

The cycle repeated til the sand was gone.....

Oh how I loved that toy.! (It would be worth good money If I still had it!)

That's what we need to get us to work and back! Sand powered vehice from the 50th floor!

as may have been mentioned the actual charging of the battery with this track system will detract from the very motion of the car itself forcing the engine to work harder thus expending more energy whether by gasoline or electric (etc.) so whatever energy is gleaned to the battery through this recharge system, would be lost to the motor. the system would be only as good as the efficiency of both the motor and the generator and the battery. many cars in the present age charge their batteries during idling, which allows for the battery to be charged during a time that it would not be convenient to stop the engine anyway. Also accelration would be a larger problem, if you have ever held a small dynamo or just generator in hand, the faster you try to spin the rotor manually , the harder it becomes to turn it, because you are generating energy. so trying to accelerate to and maintain a speed of say 60 mph would be a harder task than were the car to move without the aforementioned resistance.

Yes, it is rubbish, and this is about the third time you've posted it. Please curb your enthusiasm.

That won't save or recover any energy, but somewhere I have read of using piezoelectric generation from the load of wheels going over the road. No energy drain on the vehicles going by, and a lot more potential at lower cost.

RichH

Energy in = energy out. Always

There would be extra drag on the vehicles just making it a very
inefficient auto driven generator.

Might have some application toward the bottom of steep grades where
vehicle are normally braking though.

The piezoelectric generation is powered by tge roadway vibrations caused by the passing traffic. It's the only case where currently waste energy can be recovered without costing more energy than recovered. Worst effect would be the roadway runs cooler.

There are some recoverable resources in this world.

RichH

Hi all. I just want to state a fact: What is being proposed here is perpetual motion! This is not possible, there are a few small things like, friction, drag (another word for air friction) and engine/generator efficiancy. Take the example of a vehicle running on electricity. You burn coal to heat a boiler full of water, the steam generated has less energy than the heat applied. This steam is then used to turn a turbine, the turbine produces less shaft energy than was in the steam. The turbine turns a generator, the generator produces less electrical energy than the generator shaft. The elecricity then loses energy as it travels along a cable. The electricity is used to charge a battery in the vehicle, which in turn turns the wheels of the vehicle, but the energy at the wheels is a lot less that the energy supplied by the motor. The friction between the wheels and the road means that we lose a lot of energy there. So adding any other type of load to the vehicle only compounds the problem. Spencer.

Energy in = energy out. Always

Law of conservation of energy.

I agree with you.

These arguments seems like save the power being wasted in automobiles and use it for other needs. But energy conversion is not 100% efficient.

So, its best to prevent the wastage instead saving it in some other form.

The basic instinct is not rubbish. Because he is trying to save the power.

In this matter, regenerative braking is a good compromise since it is using 50% of braking power for mechanical braking and 50% momentum to generate electricity.

Sir ,

'Energy in = Energy out. Always'

Outrageous !

Yours ,

Annoyed Black Hole, Etherville.

"If this is true, would it be possible to reverse the effects of the train by having something built into the road, and something in the car, so that as the car drives over it, instead of using power it generates it ?"

Rikk, if I understand your question, you want to know if electromagnetic regenerative braking or simply power feedback is possible directly by interaction of electrical/magnetic components mounted in the road and the car.

Theoretically, this is possible. Practically, no. Firstly, it would be very inefficient to require more energy expenditure to overcome the magnetic resistance that would be encountered by a linear generator such as you are proposing, only to use that energy to recharge the battery you took it from in the first place!

Secondly, electro-mechanical regenerative braking as currently exists is much cheaper and more efficient that what you would propose. The costs in road infra-structure alone would be staggering, not to mention the trade-off of one proven type of regeneration for another unproven system, and the years of development it would take for no real increase in value.

But don't let this stop you from thinking outside the box. Just learn a little more about elementary Physics and practical, logical engineering. Being a good engineer actually means eliminating the NIH (Not Invented Here) factor that keeps many from looking to new and exotic solutions, provided they are real solutions and not just fantasies that defy the laws of physics! Let's leave it to the Physicists to define those laws and let us know when new loopholes are found (or the laws re-defined) that might allow us to use that new insight into the ways of the universe for the benefit of mankind. A perfect example was when Einstein postulated correctly that matter could be converted to energy inside the atom, which gave birth to the notion of extracting nuclear energy for both peaceful and destructive purposes.

I have started closing my door to read this stuff...everyone in the office was curious about my laughter. I think you guys would be a real hoot about half loaded.

And there is some reason you think we are not already half loaded?

If I understand, You are talking about a linear drive with regenerative braking - both are well-established technologies. The linear drive is particularly neat. The technology goes back over a century. It is an electric motor with all the rotation removed; it has only two moving parts - the vehicle and the electrons - and tends to be very efficient mechanically. Regenerative braking can be extremely stiff,that is very high accelleration, or "stopping power." It just trades the momentum of the vehicle for a flow of electrons. In the place I work there is a rail-based vehicle that uses these technologies. (We quit using it more than ten years ago.) Combining these technologies with maglev is naturally symbiotic - very similar technologies.

A great article at wikipedia: http://en.wikipedia.org/wiki/Maglev_train#Maglev_train_companies

Sam H.

skh7@bellsouth.net

One more item to note. The vehicle we no longer use is propelled by a simple linear drive with no mechanical components. The wheels are free-wheeling. It has a regenerative braking system, which is the primary means of stopping it. Clearly, this is an electromagnetic, rather than mechanical, system.

I think you are discussing use of this technology on individual automobiles. that would be a very serious challenge. It would require creation of an infrastructure unique to what isnow and of remarkable scope. As a comparison, use of Hydrogen fueled cars is limited by the lack of infrastructure that would take billions invested to create nation-wide. This system would dwarf those needs. Then there are the regulatory and cultural issues. A lot of obstacles to overcome.

Sam H.

Dear Sam,

Register, come aboard, and become a full fledged member, if you are not, just yet.

Top-left red strip? Where it's done. Bless you.

Guest #54:

Pot calling the kettle black, methinks?

ROFLOL

I just think this is a wonderful idea, and I would love to see it work. It dovetails well with so many other technologies on the cusp of being very useful in transportation. First among them, of course, is information technology as applied to vehicle control and traffic coordination. If there is already a persistant electrical connection between each vehicle and some central facility then overlaying this connection with digital communications is logical if anticipated. Given such a system most traffic jams would be a thing of the past. My son likes to refer to it as the "slinky effect" where traffic traffic stops every mile or so for no reason except the dynamics of the traffic. One could have assistive or true autopilot. Traffic could be routed around accidents or other blockages. The plusses are legion.

If it happened it would be just the latest in a long chain of revolution in technology and infrastructure in "recent" history. That history suggests thisis n ot impossible, regardless of how difficult.

Jules Verne comes to mind. He invented the sci-fi genre, and along the way came up the ideas of space travel and long-duration submarines at a time over a century ago when virtually everyone scoffed at the concepts as foolhardy, and even impossible. He is not the fool today.

It is a wonderful idea. What is the next one?

Sam H.

"My son likes to refer to it as the "slinky effect" where traffic traffic stops every mile or so for no reason except the dynamics of the traffic"...

Have a look at the Prometheus Road-Control Research Project in Europe, links provided here and here for your convenience.

I'd like to think it's a wonderful idea too, but I'm not sure what the idea is. It seems the original poster was suggesting that the steady state motion of the vehicle would generate electricity. That does not work to increase the vehicle's energy stores. Regenerative braking works very well, and is used in most electric road vehicles, but requires the the vehicle is demanding braking. Charging cars (and simply powering them) via inductive transfer would be appealing, although the infrastructure cost and politics would be staggering. I'm not sure what else he might have been proposing. What did you take as the essential idea?

My comments were centered on creation of a system of systems employing existing or developing technologies to allow efficient use of highways or other means of individual transport similar to highways. I thought it was a logical extension on the discussion. On reexamination I see that it is not at all the subject originally introduced. My apologies to all.

r/

Sam H.

No apologies required, whatsoever. All input is valuable.

"It seems the original poster was suggesting that the steady state motion of the vehicle would generate electricity."

Ken, my thought was that if the coil was built into the road, and the magnets built into the car, that the car could generate spare energy for the batteries.

The car would be travelling over the road anyway, under it's own power.

This has NOTHING to do with powering the car, and nothing to do with cost or efficiency, I just wondered if it was possible.

At least this thread turned into something somewhat interesting, despite the effort of certain people to demonstrate what smartarses they could be, I thank you for that.

Hi Rikk:

Your question is a good one, and represents the kind of thinking that needs to be done. There are too many people who assume that all the efficiency questions have already been answered -- that engineers must already have thought about this stuff. And although many engineers do, in fact, think about squeezing every lost drop of efficiency out of systems, many do not. Consider the Toyota Prius, which will carry 5 people in comfort and get 50 mpg, vs the original Hummer, which will also carry 5 people (and has atrocious ride and handling) at 10 mpg.

I've been something of an efficiency nut for quite a while. The boat in my avatar came out of a desire to offer a boat that could sail at near "jet ski" speeds, but not use any fuel whatsoever. A the time that I built it, the world speed sailing record stood at about 46 knots (53mph) in 18 knots of wind. The average wind around the US is only 8 knots, but if my boat could do 3 times wind speed (on a reach, i.e., with wind from the side) then you could sail at 24 knots on an average day -- fast enough to be fun -- and on a windy day, you could have a blast. Jet skis, by comparison, make Hummers seem like marvels of efficiency. In the year 2000, a typical 2 stroke jet ski (which is actually a Kawasaki product -- the generic term is personal watercraft) would dump almost 1/3 of its fuel, unburned, out the exhaust and right into the water. They would emit more pollution in an hour than a typical full-sized car would emit in several years driving. (This sounds like hyperbole, but it is not.)

So there are loads of efficiency improvements to be made.

In CR4 we periodically get threads in which a perpetual motion machine is proposed, and sometimes these are proposed with the intent of making money, and are true, (probably knowing) frauds. So people can be a bit impatient if it sounds like someone is proposing anything related to "free energy", "perpetual motion", or "over unity" machines.

So in the case of your question, it is true that with magnets close to coils in the road would generate current in those coils that could be used to charge batteries (or power electrical devices, etc.). However, it is also true that as soon as any current is generated, the car must either slow down, or the driver must press harder on the accelerator pedal to maintain speed. If the generating and charging systems were perfectly efficient (they are not), the electricity gained would equal the energy lost in the car dong the generating. Given any losses at all, the energy gained will be be less than the energy lost. So if the car is on a level road, generating any current from its motion will cause it to use more energy than you can get back.

But if you want to go slower, then the energy required to slow you down can be either entirely lost, in mechanical braking heat, or can be used to charge up the batteries, as it is in regenerative braking. (Or, in your idea, the braking energy could end up in the underground coils, and be fed back into the grid, so someone else uses the energy -- but you car would have a meter and you'd only pay for the energy used, so regen would save you money -- in the same way that windmill owners sell back energy to the power companies, unfortunately at very low rates).

One of the posters mentioned an infrastructure in which charging could be done inductively: coils in the road would be fed AC acting as one half of a transformer, and pickup coils in the car would act as the other half. (The GM EV was charged this way (although while sitting still: there was no wired connection between the car and the "puck" you'd plug into it during charging.) 60% efficiency is pretty low for electrical systems, but much of the time, the vehicles in question would be operating directly off the inductive connection (and not charging their batteries [which is "lossy" even when hard wired]) so the total efficiency could be pretty good.

With either a slip ring style connection (like an old street car) or a very precise gap inductive coupling, the transfer of energy from grid to vehicle could be very high (97%-99%). The motor in such a vehicle could operate at 96% efficiency much of the time, and its controller could operate at about 98% efficiency. A simple two speed transmission could be 96% efficient, so a modern equivalent of a street car, but with temporary autonomy for lane changes, could be highly efficient. Of course, the grid is supplied with energy at about 38% efficiency -- not much better than automotive diesel engine efficiency. But there are many reasons to believe that the overall efficiency of generating power can improve.

In any case, good question, good thread.

Here is a piezoelectric generator that consumes only "waste" energy that could perhaps be mounted on the vehicle, as well as in the roadway for use in roadway lighting or control. The loss of heat generated by the dampening action of shock absorbers and springs might allow a similar decrease in weight as that of the added micro-generators.

Free energy it is not, but recovery of waste is another matter. From the website http://www.vibes.ecs.soton.ac.uk/piezogen.htm,

Micromachined Piezoelectric Generator

Both electromagnetic and piezoelectric generators utilise a cantilever/mass structure. The piezoelectric generator couples the motion of a silicon mass and cantilever beam to AlN or PZT piezoelectric thin films deposited on the top surface of the cantilever. Figure 1 shows a finite element plot of a typical device geometry.

Figure 1 - Finite element model of piezoelectric generator

This has been fabricated using a range of standard silicon micromachining techniques and a completed device deflecting during testing is shown in figure 2. Initial tests on early prototypes have demonstrated ~10nW of power generated at resonant frequencies of around 200Hz from an AlN device with a volume of 1 cubic millimetre. PZT based generators are currently under development.

Figure 2 - Piezoelectric genertaor under test