New Jersey Turnpike As a Power Source?

New Jersites writes "New Jersey, home of the eponymous Jersey barrier, is considering wind turbines powered by the breeze generated from traffic on the Jersey Turnpike. The wind turbines won't be built on the side of the highway. They will be built inside — what else? — the Jersey barriers. By replacing sections of solid concrete with Darius turbines, they might be able to harvest enough energy to power a light-rail line."

Comments

Drag?

[Graham MacRobie]

I'm not a physicist, but won't the turbines cause a drag effect on the cars, resulting in the cars burning more fuel? Is so, aren't they just moving the problem from one place to another? There's no such thing as free energy, right?

Truly curious - I'd love an explanation if someone knows why this isn't the case.

Re:Drag?

[deek]

I'm not a physicist, but won't the turbines cause a drag effect on the cars, resulting in the cars burning more fuel?

You've got it right. The turbines would take energy from the air being pushed around by the cars, leading to the breeze around the car slowing down, and therefore exerting more drag on the car.

At the same time, this is a rather ingenious way of creating a virtual toll for roads. If the power gathered is then invested into a public transport system, then you'll end up having drivers subsidise public transport. The fuel savings with public transport may well offset the extra fuel burnt through the turbine induced drag.

Re:Drag?

[tobias.sargeant]

I agree with you. Turbines do generate turbulence, however, and turbulence will impede the progress of cars to some small extent. It is possible for this to be a net win, contrary to the assumption of the originator of the thread. It's also reasonable to assume that it will cause a non zero increase in energy expenditure by cars. Whether it's negligible or not is something best left to engineers and fluid dynamics simulations.

Re:Drag?

[smenor]

At the same time, this is a rather ingenious way of creating a virtual toll for roads. If the power gathered is then invested into a public transport system, then you'll end up having drivers subsidise public transport.

That's a great point I never would have thought of.

The fuel savings with public transport may well offset the extra fuel burnt through the turbine induced drag.

I'd be shocked if the energy extracted from burning extra fuel in cars on a freeway would come close to what you'd get by burning the same fuel in a properly designed power plant (and I'm quite confident that the emissions would be worse).

Re:Drag?

[Myself]

The wind blowing on that unit isn't caused by the cars, and that wind doesn't always benefit the cars.

The wind in the (been-shot-down-before) turnpike story is a draft caused by the cars' motion, and benefits their efficiency because it acts like a slight tailwind for each vehicle. Eliminating that tailwind would have a large energy cost, compared to the minor harvest from the turbines.

Re:Drag?

[Kpt Kill]

I'm not a physicist, but but aren't those large sections of cement there for a reason? like preventing crashes from spilling to the other side of the highway?

Re:Drag?

[Capsaicin]

There's no such thing as free energy, right?

Indeed! There is, however, such a thing as wasted energy.

Re:Drag?

[Nefarious Wheel]

The point is, the cars are going to be generating that wind whether it's used or not. Inside a plenum, you will get a lateral compression shock wave from pushing the car through that air. That compression results in drag. Where that compressive effect is diminished (by say, venting it through holes in the plenum walls --- oh, yes, let's stick some turbines there while we're at it --- you will get a net reduction in the amount of drag on the cars. They're still pushing air and making the shock waves, but the compressive resistance is less than it would normally be, no? Ergo, no measurable penalty.

I imagine if they slso harvested all that exhaust heat from passing cars and friction dumped into the road from the rotating tyres, you could tap that heat differential with a closed gas heat exchanger perhaps running a Stirling engine.

The energy is being dumped anyway, might as well recover what we can. Reduce, re-use, regenerate...

Re:Drag?

[dheera]

This is an unfathomably silly idea that shows how much energy is being wasted in commuting. The solution is instead to reduce the amount of driving and replace the insane amount of driving in this country with a decent train and bus network that actually gets people where they want to go. New Jersey has extremely poor public transportation for its density compared to other similar-density parts of the world outside the USA. The amount of energy that could be saved (in joules provided by gasoline) by reducing driving would be orders of magnitude higher than that you could generate (in joules of electrical energy) from turbines from the wind from cars. Even if you reduced driving by as much as 5-10%, I would suspect that that energy reduction would by greater than what could be generated.

In addition, yes, this will create some degree of drag on the cars, and in essence, they are using gasoline to produce electricity in about the most inefficient way possible. Considering oil is already becoming scarce and is not renewable, they should not do this.

Re:Drag?

[bwcook0]

OK lets expand this theory a bit. Suppose said kettle....what the hell, lets call it a boiler, is under a turbine and I want to boil water and have the steam turn the turbine. A novel idea. Unforunately it is going to take extra energy to boil the water now, as the increased pressure in the kettle from the pushback of the turbine is going to raise the boiling point of the water. The car is the kettle, the burner is its engine, and now the engine has to work harder.

Re:Drag?

[yahooadam]

>I'm not a physicist, but won't the turbines cause a drag effect on the cars, resulting in the cars burning more fuel? Is so, aren't they just moving the problem from one place to
>another? There's no such thing as free energy, right?

No it wouldn't cause drag on the cars

the cars are already pushing a wall of air, ATM that wall of air just dissipates after a while, the barrier would take that wall of air and convert it to some power

So in fact, its actually making the cars more efficient, as the wasted energy that is normally lost through drag is being utilised now

Re:Drag?

[Rei]

Any boost that the turbines are getting is resisting an equivalent amount of airflow induced by the cars, which the cars will need to reaccelerate. The further you move them away, the less work the cars you need to do, but you get correspondingly less power.

It's a really stupid idea.

Re:Drag?

[Gilmoure]

Isn't the wind from the cars currently impacting on the plain barriers now, exerting a force on them? Granted, that force isn't enough to move the barriers or even heat them appreciatively (friction) but if the wind is already there and just be deflected upwards/out towards the cars, why not harness it. It's like harnessing the wake in a channel. The boat's going to make the wake regardless of what it impacts on. Is doubtful current highway is designed for the wind wake to bounce back and power the cars going past.

Re:Drag?

[yahooadam]

As you said, when a car passes its wake effects you

Whether you are there or not, the wake exists, normally it just dissipates around the car - wasted energy

If they put these by the side of the road that energy can be utilised, how is that going to cause drag, your already pushing the air around you, the drag is already happening, their just using that to make energy

I don't see this causing additional drag at all

Lets compare this to solar energy, the light hits the ground, that energy is wasted, put a solar panel in the way and you generate power, but there are no more solar rays to do this, your just harnessing otherwise wasted energy

Though i believe that it would make more sense to put up some solar panels, rather then spend all this money on roadworks and stuff to harness the air that's being pushed by a car ....

The barriers are supposed to be solid.

[deopmix]

This might work until somebody decides to use the barriers for their original purpose(separating traffic). When the Powers That Be realize that the only thing separating two lanes of traffic moving at each other at 140 mph is a few turbines they may decide that this is a Bad Idea.

People can fly?

[ghoul]

If you put a light rail right in the middle of a high traffic freeway how do people get on or off? Fly?

Something similar in London?

[steevc]

This week I noticed a set of four more conventional wind turbines had appeared on a new building on the A406 North Circular Road opposite Ikea. If the intention is to use the breeze generated by cars to power them then they are doomed as the traffic generally crawls past there. Given all the stuff I've read about the viability of wind turbines in built-up areas I wonder how much good they will do anyway, but it's still a very visible bit of greenwashing.

My first thought on seeing a picture of the NJ turbines was that they would have to be increasing the fuel consumption of passing cars, if only marginally. Perhaps they could be placed where people should be slowing down, e.g. off ramps and junctions, to actually slow the cars a little. I had a thought ages ago that junctions should be on raised ground so that cars are naturally slowed as they approach uphill and gain easier acceleration as they leave downhill.

Have you seen that "systems analysis"?

[Bearpaw]

This same systems analysis makes a hummer look competitive with a prius in terms of total energy consumption during its lifetime.

Have you seen that particular "systems analysis"? I have. It's so blatantly flawed that the flaws are almost certainly intentional.

Cost

[Billkamm]

Wouldn't the cost of installing and maintaining all of those turbines far exceed the cost savings of the electricity generated?