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Generation of electricity from moving vehicles (Current thread in Scepticism.etc).)

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sundar
#1
Aug15-08, 12:27 PM
P: 7
Original Post
"
Using electro gravity tiles, there is an emerging technology that can generate electricity from moving vehicles. If we continue to populate the highways and roads, we might as well extract energy from their motion. How cool is that? "


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"Originally Posted by Ivan Seeking
This is completely bogus. The energy from the tiles comes from petroleum powering the cars. It would be an extremely inefficient means of converting petro energy to electrical energy"


My Thoughts :

A car expends energy in moving forward (and overcoming friction). Unless the car continues repleneshing its energy sources (through the accelerator), it is going to come to a halt eventually, even without braking (Otherwise, one would keep moving in a state of uniform motion or skid)

So at every moment, the car is imparting some stress to the surface of the road. I feel it should , in principle be possible to avoid dissipation of energy as heat if one could have transducers below the road surface converting the pressure / strain energy to electricity and storing the same (even on straight stretches)

When considering density / tonnage of traffic on busy highways, this should translate to a sizeable amount of energy over a period of time. I guess efficiency etc is a matter of engineering and / or demand / economics / mass production.

Possible applications :

- Lighting up highways at night
- Controlling speed of cars (by tuning the amount of energy absorbed at different sections of the road) and reducing need for braking and / or making braking easier
- Auxilary source of power for track electrification in case of rail traffic.

Regards,
Sundar
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russ_watters
#2
Aug15-08, 04:15 PM
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It's real simple: any energy that is already being absorbed by the road or the tires would be better saved by decreasing the friction that causes it in the first place. And it really actually isn't much energy: the vast majority is lost due to wind resistance at highway speed.
mgb_phys
#3
Aug15-08, 04:46 PM
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Quote Quote by russ_watters View Post
the vast majority is lost due to wind resistance at highway speed.
There was a suggestion to use small road side wind turbines to harvest this wasted energy and use it to power lighting etc. The advantage is that it doesn't impose any extra load on the car and is a lot easier/cheaper to fit

russ_watters
#4
Aug15-08, 07:56 PM
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Generation of electricity from moving vehicles (Current thread in Scepticism.etc).)

Quote Quote by mgb_phys View Post
The advantage is that it doesn't impose any extra load on the car
That isn't true. Anything that happens in the car's wake affects the drag on the car. Even worse, when you have several cars traveling together on a highway, they help each other - if you have 3 cars drafting off each other, the third still helps the first, and this would hurt all of them more.

And again, the amount of energy available here is very small or perhaps better put: the energy density is very low. The turbines would generate orders of magnitude more electricity from the local wind than from the cars driving down the road.
sundar
#5
Aug15-08, 11:18 PM
P: 7
But we do need traction / friction, d'ont we or vehicles would be slipping / skidding.
Besides, what is miniscule at the level of a single vehicle at a single spot would be sizeable when one considers the total mileage of all vehicles along an entire highway. Besides, as compared to other viable forms such as wind energy etc, the road / track can be said to form a connected grid which would be convenient for pooling energy
russ_watters
#6
Aug16-08, 08:15 AM
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Quote Quote by sundar View Post
But we do need traction / friction, d'ont we or vehicles would be slipping / skidding.
Static friction does not dissipate energy. Rolling friction, due to the flexing of the tires, is where the energy is dissipated. Making the tires harder and roads smoother would save tons of energy (at the expense of comfort...).
Besides, what is miniscule at the level of a single vehicle at a single spot would be sizeable when one considers the total mileage of all vehicles along an entire highway.
Actually, it's not. The energy dissipated in this way is not a sizeable fraction of our gas usage and recovering it would require covering millions of miles of roads with something to absorb it. I did some calcs in the other thread on the subject.
sundar
#7
Aug16-08, 11:32 AM
P: 7
One could view the problem as that of a rotary toothed profile engaging with a linear toothed profile (which may be a mix of different pitches and which may in general , not be in resonance with the rotary profile). If an initial force were enough to keep in things in motion for ever (neglecting air resistance which would be negligible except at high speeds), would it not amount to realizing the equivalent of a perpetual motion machine ?

Entropy could possibly be another factor to consider as well as improving efficiency by dampening modes of vibrations of the car.

Possibly , harnessing vibrations induced by vehicles moving over bridges and similar structures would be a comparitively more efficient way of harnessing energy.

In this connection, it would be interesting to examine the effects of a vehicle being driven over sand.
--
Sundar
chayced
#8
Aug17-08, 08:35 PM
P: 158
Actually there is a wind powered car prototype:[crackpot link deleted]
I would invest, but I already have all my money in magnet engines.
sundar
#9
Aug18-08, 12:17 AM
P: 7
The wind powered / propelled prototype looks interesting and would be useful in areas with constant wind (assuming that there is enough wind for people to enjoy a cool breeze !). Presumably, the wind power feeds into a system of turbines / generators that move the vehicle in the forward direction.

An interesting possibility is whether air resistance could be deflected and reversed (possibly with sails / other devices) to power the vehicle in a similar fashion .

In any case, it is orthogonal to the harvesting of energy from the motion of the vehicle (which is also useful in cases where there is no wind or less wind).

The road / track provides the most convenient medium for collection, storage and distribution of power in an efficient way.
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Sundar
jaap de vries
#10
Aug18-08, 01:16 AM
P: 254
Quote Quote by sundar View Post
The wind powered / propelled prototype looks interesting and would be useful in areas with constant wind (assuming that there is enough wind for people to enjoy a cool breeze !). Presumably, the wind power feeds into a system of turbines / generators that move the vehicle in the forward direction.

An interesting possibility is whether air resistance could be deflected and reversed (possibly with sails / other devices) to power the vehicle in a similar fashion .

In any case, it is orthogonal to the harvesting of energy from the motion of the vehicle (which is also useful in cases where there is no wind or less wind).

The road / track provides the most convenient medium for collection, storage and distribution of power in an efficient way.
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Sundar
I have been hanging around the political threads too much and I almost forgot that when it comes to these kind of things, Russ does know what he is talking about.

The main point is the quality of the energy, in the case of using the air that is displaced by a car, this is a very turbulent flow with high level of vorticity. In other words, extremely hard to capture.

In the case of using the road resistance I don't really understand your argument here. Where is the energy? You might as well lay a brick on the table and harvest energy from that. I worked with MagLev and linear induction machines but I just don't see any residual waste here that can be used.

I would actually like to place you argument in a larger discussion, and that is people that have finite scientific background (politicians) supporting these ideas that are not viable or don't make sense. I have even been called "closed minded" because I don't believe we can have cars run on water, or put turbines on their roofs etc.
sundar
#11
Aug18-08, 03:38 AM
P: 7
As far as turbulence and vorticity are concerned, i suppose there would be a boundary layer separating the laminar flow from the turbulent which would be relevant for our purposes.

Regarding the main topic, it is all about harnessing the energy absorbed by the road / track. Otherwise there would be no energy expended by the car in uniform motion (in cruise control mode for example) which obviously is not the case as mentioned in one of the earlier posts on this thread.

And most of those staying near railway tracks would have felt the vibrations when a train passes by not to mention bridges / other structures.

This energy could be stored and harnessed (again as mentioned in the earlier posts)

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Sundar
Topher925
#12
Aug18-08, 10:19 AM
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P: 1,672
The wind powered car haha, are you serious? If you want a wind powered car then you should just use the technology of the wind powered boat (also called the sail boat ) and just put a sail on it.

The energy your talking about is not enough to bother harnessing. Putting transducers in a road is extremely unpractical for the gains it would give even for a train. You would be better off using transducers as dampers in the cars suspension.

And as mentioned earlier, the majority of the energy wasted in a car cruising down the road is wind resistance, which it maybe takes 10hp to overcome for your average sedan. The only time you use a lot of power in your car is when your accelerating and giving your car kinetic energy.
sundar
#13
Aug18-08, 12:05 PM
P: 7
As i seem to recollect, the wheels of toy vehicles , given an initial torque, revolve much longer when held in the hand as compared to the time they spend on the ground. As mentioned earlier , rolling friction seems to be a major component even in cruise mode (or there would be slippage etc ). Even in case of a railway track (where friction is relatively less), the kinetic energy due to the flywheel action of the wheel (which would have been available to complete the full cycle and achieve maximum potential) is spent in driving the track / rail in a rack and pinion mechanism. The idea is to harness this energy (or part of it). Of course, there would be other factors like internal friction in the flywheel action of the engine and / orwheel. In case of structures such as bridges, there are the forces that cause bending and vibrations of the structures due to the loads.

The idea is to use some kind of shock and energy absorbent fluid (possibly at the time of laying the road / rail blocks) which can conduct , store and generate electricity (when subjected to mechanical loads) like a piezoelectric transducer. The law of conservation of energy would still not be violated (the law of conservation of momentum still stands -> Newton's third law etc) if the free energy of the system stays the same or is reduced by increasing the entropy of the absorbent fluid (which accounts for its energy storage capability)


As mentioned earlier, they can also be used for sensing and dampening vibrations, regulate the speed of vehicles along sections of the road, absorb shocks whatever the type / model of vehicle (including one with relatively stiff horse carriage wheels :-) !! which does not deform under applied load and which could reduce rolling friction as mentioned in one of the earlier posts)

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Sundar
russ_watters
#14
Aug18-08, 05:24 PM
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P: 22,252
I deleted the link to the youtube self-wind-powered-car crackpot. Hopefully everyone realizes it was posted as a joke...
chayced
#15
Aug18-08, 05:32 PM
P: 158
Sorry, I thought it was pretty over the top. Didn't mean for anyone to take it seriously.
russ_watters
#16
Aug18-08, 09:49 PM
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P: 22,252
No prob - I got a kick out of it, but I just wanted to make sure some more impressionable types would understand that it was joke.
sundar
#17
Aug19-08, 03:54 AM
P: 7
The topic seems to be linked to the concept of a material absorbing energy under a load and bouncing back thus transmitting the same energy to the load (bouncing ball or someone bouncing off a trampoline). It would be interesting to investigate if more energy can be extracted from the material (possibly over a period of time) than was put in, i.e, a mechanical analogue of raman's effect where the system is excited to an unstable state by absorbing energy and transmits a photon of higher energy and drops to a lower energy state. The system also cools down (also could be linked to increase of entropy). Of course, the probability of this depends on the temperature.

For example , materials like rubber elongate and become more directed under force thus losing entropy and hence becoming unstable. This instability could be harnessed for release of energy (possibly more than was put into the system). Liquid crystals also order themselves when exposed to electromagnetic fields of certain frequencies, thus lowering entropy and thus increasing instability and making it suitable for harnessing energy. Of course, to store energy, one would have to reverse this process.

It seems to boil down to a search for the right materials whose stability / instability properties can be tailored / harnessed properly and where the energy can be harnessed appropriately at the right time and place. (One wild fanatasy related to the you-tube link : Could air be such a medium ? :-))

Could the above also be linked to forces causing vibrations of certain frequencies causing collapse of the structures ? ( Of course, in this case, they have not been dampened / harnessed appropriately)

In any case, IFF fuel was available in plenty and cheaply (through solar power, use of water as fuel, wind power etc), then the road could absorb a certain amount of energy thus increasing fuel consumption a bit. But overall, this could go a long way towards creation of an immense reservoir of energy that could be harnessed for tasks of earthshaking magnitude that would have been otherwise impossible to accomplish.

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Sundar
russ_watters
#18
Aug19-08, 05:28 AM
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P: 22,252
Ok, now you are talking about perpetual motion and various other crackpot ideas. This thread was on thin ice to begin with - now we've fallen through.


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