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?

[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?

[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.

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.