New Jersey Turnpike As a Power Source? 264
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."
Re:Drag? (Score:3, Informative)
Re:Drag? (Score:5, Informative)
Re:Drag? (Score:3, Informative)
Re:Drag? (Score:2, Informative)
"New" Jersey Barriers (Score:5, Informative)
Dumb idea - way too small (Score:4, Informative)
Wrong answer. Too many little turbines not generating enough energy each. Worse, gearing a number of turbines together when they don't get uniform wind pressure means some of them are just sources of drag.
Progress in wind turbines has been through scaling them up. The 50KW - 100 KW machines of the 1970s never paid for themselves. Somewhere above 500KW, the economics start to work, and farms of megawatt and up machines are quite profitable. Here's General Electric's 2.5 megawatt wind turbine, [gepower.com] which is typical of current large wind turbines. Total worldwide wind generation capacity is about 75 gigawatts. Wind power is now a serious energy source because, at last, the units are big enough to generate serious power.
Nothing to do with New Jersey (Score:1, Informative)
Re:Drag? (Score:4, Informative)
I am a physicist and had the same thought.
Without a doubt, the turbines will interfere with laminar flow, increase turbulence, and increase drag.
I have no idea if the increase in drag will dominate over the increase in efficiency by reclaiming lost energy, but it's definitely something that should be studied before implementing this kind of system on a large scale.
Re:Drag? (Score:3, Informative)
Yes: Drag. (Score:5, Informative)
The stream of cars generates an air motion along their path. Like geese (though through a different mechanism) the leading cars reduce the amount of air drag experienced by following cars. This improves their fuel economy. (The phenomenon is even more pronounced with semi-trucks. "Drafting": following another truck closely to save even more fuel, is a common practice.
A smooth central barrier separating the two directions of traffic improves the situation by letting the two sides of the freeway have separate airstreams traveling in opposite directions. The barrier reduces energy lost to turbulence, improving the airflow.
Replacing the barrier with turbines will suck energy out of the air streams on both sides to generate electricity. The result will be to decelerate the airstreams that had been giving following vehicles an advantage.
While some of the power comes from captured crosswinds and some from capturing energy that would have been lost to turbulence anyhow, a large portion of it comes from increasing the drag on following vehicles by putting friction on the "following wind": Fuel economy for the trailing vehicles in a bunch is reduced to something near that of lone or leading vehicles.
But there's plenty of power to be had higher (Score:5, Informative)
There's PLENTY of power to be had WITHOUT disrupting the traffic airflow and canabalizing the fuel of the cars.
A freeway or toll road is a clear area and there will be plenty of winds ABOVE it that are essentially unrelated to the airflow near the ground. They're also faster - with energy going up with the CUBE of the airspeed.
By building a wind turbine that starts significantly above the ground the turbines can avoid disturbing the flow at traffic level while collecting plenty of energy.
Also: A Darrieus wants linear airflow THROUGH it. It would be great for salvaging power from crosswind, but rotten for snagging power from opposing winds on the two sides of its axes.
And they're a major hazard: Darrieus turbines fly at tip speeds of about 7 times the wind speed and their narrow blades experience drag loads about equivalent to a wind barrier with a cross-section the size of the swept area - reversing twice per rotation. This has tended to produce fatigue in their materials, sometimes ending with the mill coming apart in high winds some years after construction, with massive pieces flying around at a goodly fraction of the speed of sound.
A savonius-derived design (like the Sandia configuration) would be a better choice. Though it only collects about 2/3s as much power for a given swept area, it rotates at about an eighth the speed and has broad blades that can be much more solidly constructed.
Re:Drag? (Score:3, Informative)
http://en.wikipedia.org/wiki/Betz'_law [wikipedia.org]
50% ain't bad anyway. It beats many other common energy transformations. Your average automobile is probably only 10% efficient.
A far better idea than sapping cars' energy (Score:3, Informative)
Re:Drag? (Score:5, Informative)
The air moved around by the cars is being absorbed and dissipated anyway by the objects surrounding the road. All the turbines will do is instead of the airflow from the cars going to swish the surrounding grass, trees and bushes - it'll spin a turbine. The energy is already being absorbed by the surrounds of the road.
It's like putting a turbine over a kettle - you won't cause the kettle to use more energy to boil the water by allowing the steam coming from it to pass through a turbine - you'll just extract some of the energy that otherwise would have been used up by the environment of the kettle.
If it's designed correctly, it won't increase drag.
Re:Nothing to do with New Jersey (Score:2, Informative)
Try again! You're right it's a modification to a Jersey Barrier, but this Jersey Barrier is in NJ on the New Jersey Turnpike.
Summary:
*New Jersey*, home of the eponymous Jersey barrier, is considering wind turbines powered by the breeze generated from traffic
Article:
*New Jersey* highways to be used as a power source, Governor made an offer he couldn't refuse