The fact is that the UK abounds in speed bumps (“sleeping policemen”) as “traffic calming measures”, as Douglas2 points out. You find them on most suburban streets. Other methods of forcing cars to slow are used in more urban areas. It remains a fact, however, that cars go over the bumps and lose kinetic energy. Some of that energy shows up in the cars’ shocks and springs or as heat on the bump. The rest of the kinetic energy, as well as the potential energy represented by the pull of gravity on the car, is what’s a question. This’s pure physics and fully in compliance with the 2nd Law of Thermodynamics.

The proposal is to intended to harness the energy that would otherwise be lost (as Douglas2 also points out) by converting the up/down mechanical energy into electrical energy. No violation of laws here. It is ‘leeching’ or ‘vampirism’ only to the extent that new speed bumps would be built in order to generate power. Otherwise, it’s just capturing energy that would otherwise be discarded.

Perhaps the process is not efficient. It might not be cost effective in the end. But since the energy lost from the cars passing over speed bumps is already drained from the cars momentum, it is not irrational to find a way to scavenge that energy and use it. Any tool or toy that works by converting a hand squeeze into rotary motion (like some pinwheels) can also be jiggered to convert it to electricity (as, for example, the newer battery-less radios). Doing it at a larger scale–i.e., vehicles passing over a pressure plate–certainly will work. Just how well it will work is the only question.

Well, it’s not technically free, but it is currently being thrown away via friction to the brakes.

This is actually a pretty good idea for places like exit ramps, where all that momentum that normally just goes into deforming your brake pads could be used to generate power. The only question is whether the “free” energy can pay for the cost of the apparatus.

He meant, essentially free jobs for life for marginally talented engineers who have a phobia for working in private industry where you actually have to make real profits by serving people if you’re going to survive.

“This guy is an engineer who used to advise the UN?”

Er, yes, I understand that before becoming an engineer he was a special diplomatic advisor to the U.N. on “how to avoid genocide in Rwanda”, “how to establish good government in Haiti”, and “how to avoid corruption in the Iraqi oil-for-food program”.

Holy mother of… Are they retarded? ~$100,000 for a friggin’ speed bumb? Even if it does generate a few thousand watts, a lot of it is just stolen from the drivers, it’s still a tremendous waste of money.

For $100,000 you could provide solar panels for 10-15 few houses (or better yet, you could pool the money and build nuclear reactors).

Energy per ac= force times distance = 5000n * 0.1m = 500J
Per car = 1000J
3 cars/second = 3000W. (Really, will cars be going bumper to bumper fast enough to cover 3 time length in a second? In a speed-bump zone?)

We’re only short of the claim by a factor of 10. I guess that’s close enough for an engineer who worked for the UN, although my boss would fire me so fast…

What is the effect on the car? Say it’s going 25kph (15mph), which is pretty fast across speed bumps. The KE is 1/2 (1000kg)(25000/3600 m/s)^2 = 24,000 J. Take away 1,000J and the new speed is 6.80 m/s = 24.5 kph. Not much of a jolt, but there will also be an up-and-down jolt. That vertical jolt is inefficient energy transfer, so I think if the device is built at all right, it won’t jolt the car up and down nearly as much as a mild 2 inch speed bump, so there’s a net improvement in the ride. (Or reduction in speed bump effectiveness, depending on your POV.)

It seems pretty obvious that they’re never going to recoup the energy used to make these things and plant them in the roads. But perhaps it’s a reasonable alternative to running power lines or mounting solar cells. So, is it believable that you could power a stoplight from this? I don’t know about stoplights, but we’re manufacturing LED streetlights that use 150W. Each car going by gives one light about 6 seconds of power. What happens if it’s minutes between cars at 2 am? Better have big batteries, and better only do this at busy intersections so there’s enough daytime traffic to charge them – but busy intersections are also where there’s the most need to have a power backup, which in this case is probably a power line…

OTOH, I can see it working to light LED lane markers in a roundabout.

“Q1. Doesn’t the ramp just steal pennies from our petrol tanks?
A1. The ramp is designed to be situated in parts of the roadway where vehicles are having to slow down, for example on downhill gradients, when approaching traffic lights or roundabouts as well as replacing sleeping policemen and traditional traffic calming measures.
In the these situations, the kinetic energy of the car is being dissipated into heat (i.e. through the braking system) anyway; the ramp at this point scavenges a degree of kinetic energy as the car passes over it, but this is far less than is lost through other mechanisms.”

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These could certainly be installed on highway off-ramps and downhill slopes where one must slow down anyway. Thus, some energy is captured instead of it being lost to heat/braking anyway. Speed bump replacement (as the article stated) is another viable use.

They are NOT proposing they be placed in the middle of normal roads but in places where one is braking and losing that energy to heat friction anyhow. It is all about placement. Effective placement is certainly beneficial and NOT being stolen from drivers.

It’s still going to be quite the bump, though, with half the speed loss.

This seems implausible. Assume our stream of cars is going 100kph, spaced out one car every ten meters. This is 10,000 cars per hour; let’s call it 3 cars per second. If each car pushes down a piston a distance of 10cm with a force of 1000n, twice (once for each set of wheels), that’s 3 x 2 x 1000 x 0.1 = 600 Joules per second, or about 150 watts. And I believe the jolts would be quite noticeable with these parameters (though it could depend on the mass of the moving components). Then again, since this is a ‘series of panels’ maybe they are going to have a hundred of these things in a row…

As a thought experiment, we can figure out how much of a decelerative shock a perfectly efficient fixed-point ‘momentum extractor’ would have to inflict on passing cars in order to generate 30 kilowatts of power. Again, let’s assume 3 cars per second, this time 25m/sec velocity, each car weighing 1000 kilos. Each car is packing 312,000 joules of energy (e=1/2mv^2), and we need to get about 120,000 joules per second (actually a bit more, I am using 1w = 4J instead of 4.18…), or 40,000 joules of energy from each passing car. So if we can reduce the velocity to 23.3m/sec and use that energy with 100% efficiency, we have our 30kW.
Assuming the car travels 4m in the ‘deceleration zone’, it will spend 1/6 of a second decelerating. 1.7m/sec / 1/6 = 10.2m per second squared, a little more than one g of deceleration.

Anyway, the only way this thing would be a free lunch is if you put it in some spot where people had to decelerate anyway, and preferably one where people are going kind of fast (stop sign is a lousy idea not least because you don’t have high enough velocities at work). For example, on the downslope of a big hill. I’m sure it’s still 100x easier to build a working wind turbine than this cockamamie thing, but it’s not a total violation of thermodynamics.